Search

The GW electron–hole interaction kernel, which includes two second-order exchange terms in addition to the first-order direct and exchange terms considered in the conventional GW + Bethe–Salpeter method, is applied to 10 two-molecular systems and six thermally activated delayed fluorescence (TADF) molecules in which inter- and intramolecular charge transfer excitations are expected to occur. The contributions of the two second-order exchange terms are almost zero for intermolecular charge transfer excitations and ∼0.75 eV for intramolecular charge transfer excitations according to our exciton analysis method with exciton wave functions. For TADF molecules, we found that the second-order exchange terms are more significant than the first-order exchange terms, and the contributions—even for local-type and delocalized-type excitations—are not negligibly small. We revealed that the two second-order exchange terms are proportional to the molecular size, the exciton binding energy, and the electron–hole overlap strength for intramolecular charge-transfer excitations. We believe that our findings are indispensable for further considerations of the GW method in the future. [ABSTRACT FROM AUTHOR]

Photofunctional materials based on donor-acceptor molecules have drawn intense attention due to their unique optical properties. Importantly, Systematic investigation of substitution effects on excited-state charge transfer dynamics of donor-acceptor molecules is a powerful approach for identifying application-relevant design principles. Here, by coupling phenothiazine (PTZ) at the ortho-, meta-, and para-positions of the benzene ring of benzophenone (BP), three regioisomeric BP-PTZ dyads were designed to understand the relationship between substituted positions and excited-state evolution channels. Ultrafast transient absorption is used to detect and trace the transient species and related evolution channels of BP-PTZ dyads at excited state. In a non-polar solvent, BP-o-PTZ undergoes the through-space charge transfer process to produce a singlet charge-transfer (1CT) state, which subsequently proceeds the intersystem crossing process and transforms into a triplet charge-transfer (3CT) state; BP-m-PTZ experiences intramolecular charge transfer (ICT) process to generate the 1CT state, which subsequently transforms into the 3CT state by the intersystem crossing (ISC) and finally converts into the local-excited triplet (3LE) state; as for BP-p-PTZ, only 3LE states can be detected after the ISC process from the 1CT state. On the other hand, the twisted ICT states are generated via twisted motion between the donor and acceptor for all BP-PTZ dyads or planarization of the PTZ unit in high polar solvents. The excited-state theoretical calculations unveil that the features of ICT and intramolecular interaction between the three dyads play a decisive role in determining the through-bond charge transfer and through-space charge transfer processes. Also, these results demonstrate that the excited-state evolution channels of PTZ derivatives could be modified by tuning the substituted positions of the donor-acceptor dyads. This study provides a deep perspective for the substitute-position effect on donor-acceptor-type PTZ derivatives. [ABSTRACT FROM AUTHOR]

Development of new organic synthetic methods fascinating the researchers which facilitating the increasing demands of the modern society, environmental friendly with high efficiency and low cost. The introduction of chromophores in an organic molecules facilitating intersystem crossing (ISC) to harvest both singlet and triplet excitons is also currently demanding field. We report a facile synthesis of symmetrical azines from carbonyl compounds and hydrazine hydrate with carboxylic acid esters as catalyst in methanol. This reaction presents a condensation of primary amino groups in hydrazine hydrate and carbonyl compounds took place simultaneously in a very short refluxing time. The prepared azines 1–10 were structurally analysed by various analytical techniques such as LC-MS1, H NMR13, C NMR, UV-Vis, FTIR and single crystal X-ray diffraction. Photoluminescence properties of prepared azines were recorded in CCl4 at 1 × 10−3 M and excitation range from 329 to 362 nm. The photoluminescence analysis results revealed that compounds 1–10 (except 8) were showed delayed fluorescence and 8 was showed fluorescence property. The photophysical properties of compounds 1–10 such as electron density and band gap energies was calculated by density function theory. This results revealed that the intra-molecular charge transfer occurs within the azines. The azine function in the azines enabling intersystem crossing hence, it is showing phosphorescence. [ABSTRACT FROM AUTHOR]

A series of six DPP-based organic small molecule photovoltaic donor materials were designed and synthesized successfully. The targeted structural design and regulation of the materials were carried out in three steps. Firstly, the introduction of a π-bridge in the molecule enhances the intramolecular charge transfer (ICT) effect and improves the short-circuit current (Jsc) of the device. Secondly, different end groups were introduced to adjust the energy levels of molecules, to obtain more matching donor materials for acceptor materials. Finally, the molecular configuration was adjusted to meet the requirements of increasing the open circuit voltage (Voc). It is worth mentioning that for the end group regulation strategy, a small molecule donor was synthesized, in which fluorene-capped triarylamine as the electron-donating unit provided a reference for the future development of related donor materials. To our knowledge, the selection of triphenylamine and phenyl-carbazole as central nuclei for double-armed small molecule donors has been rarely reported. In this work, triphenylamine and phenyl-carbazole were used as the central nuclei of the A–π–D–π–A type molecular configuration, resulting in lower HOMO energy levels and higher Voc. As a result, without further optimization of the devices, the power conversion efficiency (PCE) of the photovoltaic device based on (DPP)2TPA was more than three times that of a previously reported device based on TPA-DPP-TPA, and the PCE of the device based on (DPP)2PCZ was more than twice that of a previously reported device based on SM1. Our work demonstrates that optimization of photovoltaic performance can be achieved through rational structural design and configuration regulation of the photovoltaic material, which provides important guidance for the development of novel photovoltaic materials in the future. [ABSTRACT FROM AUTHOR]

The fluorophores, the fluorescence of which can be switched between multi bright colors in the solid state, show promising applications not only in the sophisticated multicolor display but also in the advanced encryption and anti‐counterfeiting systems. However, it is very challenging to obtain such fluorophores. Herein, we disclose such an example, g‐BPhANMe2‐Cp, which contains an electron‐donating dimethylamino (NMe2) and an electron‐accepting [(2‐dimesitylboryl)phenyl]acetyl at the pseudo‐gem position of [2.2]paracyclophane skeleton. This molecule can display tricolor mechanochromic luminescence (MCL) due to the different responses of the mechanically ground amorphous state to heating and solvent‐fuming. Owing to the absence of intermolecular π‐π interactions in the solid state, the fluorescence efficiency is very high irrespective of its morphological state (ΦF=0.60–0.87). Moreover, this molecule also displays reversible acidochromic luminescence (ACL) by protonation and deprotonation of NMe2 with trifluoroacetic acid (TFA) and triethylamine (TEA), respectively. The protonated sample fluoresces (ΦF=0.31) at much shorter wavelength due to the interruption of intramolecular charge transfer process. Therefore, with the combination of tricolor MCL and ACL properties, the solid‐state emission of g‐BPhANMe2‐Cp can be switched among four bright fluorescence colors of yellow, green, cyan and blue via treatment with appropriate stimulus. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) are subcellular organelles that are dynamic and play a central role in energy homeostasis and lipid metabolism. They also contribute to the transport and maturation of cellular proteins and are closely associated with several diseases. The important role of the cellular microenvironment in maintaining cellular homeostasis. Changes in cell polarity, particularly in organelles, have been found to be strongly linked to inflammation, Alzheimer's disease, cancer, and other illnesses. It is essential to check the polarity of the LDs. A series of arylated naphthalimide derivatives were synthesized using the Suzuki reaction. Modification of synthesized aryl naphthalimides using oligomeric PEG based on intramolecular charge transfer (ICT) mechanism. A series of fluorescent probes were designed to target LDs and detect their polarity. Nap‐TPA‐PEG3 probe exhibited high sensitivity to polarity. The addition of oligomeric polyethylene glycol (PEG) to the probe not only significantly improved its solubility in water, but also effectively reduced its cytotoxicity. In addition, the probe exhibited excellent aggregation‐induced luminescence (AIE) properties and solvent discolouration effects. Nap‐TPA‐PEG3 probe exhibited high Pearson correlation coefficient (0.957163) in lipid droplet co‐localization in cells. Nap‐TPA‐PEG3 could be used as an effective hand tool to monitor cell polarity. [ABSTRACT FROM AUTHOR]

Achieving the concurrent manifestation of thermally activated delayed fluorescence (TADF) and aggregation‐induced emission (AIE) within a single molecular system is highly sought after for organic light‐emitting diodes (OLEDs), yet remains rare. In this study, we present a novel TADF‐AIE dye, named PQMO‐PXZ, which has been designed, synthesized, and systematically characterized. Our comprehensive investigation, which includes structural analysis, theoretical calculations, and optical studies, evaluates the potential of PQMO‐PXZ for integration into OLEDs. Unlike existing azaryl‐ketone‐based emitters, PQMO‐PXZ exhibits red‐shifted emission and enhanced luminescence efficiency, due to its rigid structure and strong intramolecular charge transfer characteristics. Significantly, PQMO‐PXZ demonstrates pronounced AIE properties and TADF with a short delayed lifetime. When utilized as the emissive core, OLED devices based on PQMO‐PXZ achieve a respectable external quantum efficiency of up to 11.8 % with minimal efficiency roll‐off, underscoring PQMO‐PXZ's promise as a highly efficient candidate for OLED applications. [ABSTRACT FROM AUTHOR]

Donor‐acceptor (D‐A) materials based on butterfly‐shaped molecules could inhibit exciton‐migration‐induced quenching due to molecular twist. To explore this attribute towards beneficial photophysical properties, three novel bipolar acceptor‐donor‐acceptor (A‐D‐A) molecules with triphenyl triazine end capping along with substitution ortho to the Tröger's base (TB) scaffold varying from H, Me, and F were explored. The installation of H/Me/F imparted an electron push‐pull effect with concomitant maneuvering of photophysical properties. On increasing solvent polarity, a remarkable bathochromic shift with a significant decrease in emission efficiency was observed due to the twisted intramolecular charge transfer state (TICT). Emission enhancement in the ethylene glycol‐water mixture and diminution in the THF‐water mixture further confirmed the existence of TICT states in these TBs. The torsional dynamics in the excited state were also evidenced by the time‐dependent density‐functional theory (TD‐DFT) calculations. Owing to the butterfly architecture of the TB that suppressed TICT, TB‐Trzs exhibited a significant blue shift, accompanied by a favorable quantum yield in the solid state. Among the three compounds, Me‐TB‐Trz exhibited deep‐blue photoluminescence and was explored as a dopant in organic light‐emitting diodes (OLEDs) to obtain deep‐blue electroluminescence of brightness 4128 cdm−2 and CIE coordinates of (0.16, 0.09). [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) represent highly dynamic organelles found in almost all organisms and play a pivotal role in regulating the balance of intracellular lipid homeostasis. Viscosity directly affects the metabolism of lipid droplets, and the abnormal change of viscosity will lead to a series of related diseases. Therefore, developing a tool that can monitor changes in intracellular lipid droplet viscosity in real-time is of great significance for disease prevention, diagnosis, and treatment. In this study, a viscosity-sensitive fluorescent probe CA-LD based on an intramolecular twisted charge transfer (TICT) mechanism was developed. The CA-LD probe exhibited strong fluorescence emission at approximately 640 nm and showed a 161-fold increase in fluorescence intensity in 99% glycerol compared to water. Additionally, the probe CA-LD demonstrated the advantages of good anti-interference, excellent biocompatibility and good photostability. Significantly, because of the probe's sensitivity to viscosity, the probe CA-LD successfully distinguished normal cells from cancer cells and has been able to visualize changes in lipid droplets' viscosity induced by oleic acid. In addition, the probe CA-LD was effectively employed to monitor changes in the viscosity of cells and zebrafish induced by different drugs. Therefore, the probe CA-LD can provide an effective means for the detection of lipid droplet viscosity changes and is of great value for physiological diagnosis, pathological analysis and medical research on related diseases. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal CrystEngComm, which focuses on the design and understanding of solid-state and crystalline materials. The contents list includes various articles on topics such as halogen bonding in crown ether chemistry, metal-organic framework-derived materials for enhanced performance of aqueous zinc ion batteries, and the effect of grain boundary doping on the mechanical behavior of Ta bicrystal. The journal is published by The Royal Society of Chemistry, a leading chemistry community. [Extracted from the article]

Imidazopyridines, benzimidazoles and their derivatives are important heterocyclic substances with a wide range of future applications in the field of fluorescent sensors due to their excellent solid-state luminescence properties, long fluorescence lifetimes, and large Stokes shifts. Two 3-phenylimidazo[1,5-a]pyridines and two 2-phenyl-1H-benzo[d]imidazoles were synthesized and spectroscopically characterized by NMR spectroscopy and fluorescence spectroscopy analysis. The molecular structures and crystal stacking properties of three types of compounds, namely, imidazo[1,2-a]pyridine, imidazo[1,5-a]pyridine and benzimidazole, have been investigated by single-crystal X-ray diffraction analysis, and the results show that the different positions of the N atoms affect the stacking of the crystals, whereas the molecules are connected mostly through intermolecular π–π stacking and C–H⋯N and C–H⋯π interactions. Tight π-stacking contacts lead to a decrease in the fluorescence quantum yield of the molecules. Also, the shortened distance between imidazolepyridine or benzimidazole units and the strong aromatic interactions from polar substituents lead to solid-state fluorescence quenching. With the help of Hirshfeld surface analysis and electrostatic potential analysis, the roles of various noncovalent forces including hydrogen bonding, π-stacking, and C–H⋯π interactions in the formation of solid-state molecules are elucidated. The redshift of the emission spectra in solution with increasing solvent polarity and the apparent separation of the electron cloud densities between the HOMO and LUMO orbitals suggest that all seven compounds are typical intramolecular charge transfer (ICT) molecules. The HOMO–LUMO energy gap results are consistent with the fluorescence emission behavior of the compounds in solution and solid states. [ABSTRACT FROM AUTHOR]

In this work, we synthesize a series of push–pull compounds bearing naphthalimide as the electron acceptor and tetraphenylethylene (TPE)/triphenylamine (TPA)/phenothiazine (PTZ) as the electron rich/electron donor units. These moieties are arranged in highly conjugated quadrupolar structures. The structure–property relationships are investigated through a joint experimental time–resolved spectroscopic and computational TD–DFT study. The femtosecond transient absorption and fluorescence up–conversion experiments reveal ultrafast photoinduced intramolecular charge transfer. This is likely the key factor leading to efficient spin–orbit CT–induced intersystem crossing for the TPA– and PTZ–derivatives as well as to small singlet–to–triplet energy gap. Consequently, evidence for a delayed fluorescence component is found together with the main prompt emission in the fluorescence kinetics both in solution and in thin film. The weight of the Thermally Activated Delayed Fluorescence (TADF) is greatly enhanced when these fluorophores are used as guests in solid–state host matrices. TADF is interestingly revealed in the orange–red region of the visible. Such long wavelength emission is here observed with surprisingly large fluorescence quantum yields, thanks to the conjugation enhancement achieved in these newly synthesized structures relative to previous studies. Our findings may be thus promising for the future development of efficient third generation TADF–based OLEDs. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs) and lysosomes are vital organelles that play crucial roles in various physiological and pathological processes. However, simultaneous two-color visualization of these two organelles using a single probe for cell homeostasis monitoring remains a challenge due to the lack of rational design strategies. To address this issue, we have developed an aggregation-induced emission (AIE) fluorescent probe named TPE-NDI-Mor with an electron donor (D)–acceptor (A) structure, which can stain both LDs and lysosomes with high selectivity through green and red fluorescence imaging, respectively. A detailed mechanism study revealed that TPE-NDI-Mor, with a twisted intramolecular charge transfer (TICT) effect, shows a high affinity for a polar microenvironment. Additionally, the probe also demonstrates good stability, high anti-interference performance and a large Stokes shift, making it suitable for visualizing cell homeostasis and further disease diagnosis by tracking the dynamic changes of LDs and lysosomes. [ABSTRACT FROM AUTHOR]

Exploring the organic molecular structural features and supramolecular interactions provide basis for developing stimuli-responsive organic solid-state fluorescent materials. Herein, we have synthesized methoxyphenyl-substituted carbazole-based π-conjugated derivatives (Cz-MN, Cz-ECA, Cz-CA, Cz-CAA and Cz-NBA) with different acceptor units and investigated their influence on solid-state fluorescence. All five compounds showed aggregation-induced emission (AIE) in the solid state with acceptor-dependent tunable fluorescence from 488 to 602 nm (quantum yield (Φf) = 7.2 to 1.9%). Cz-ECA exhibited blue-shifted fluorescence, whereas Cz-NBA showed red-shifted fluorescence. Cz-MN, Cz-ECA and Cz-CA revealed relatively strong solid-state fluorescence compared to Cz-CAA and Cz-NBA. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) calculations suggested intramolecular charge transfer (ICT) from the carbazole donor to the acceptor unit. Mechanofluorochromic studies of Cz-MN and Cz-ECA showed self-reversible fluorescence switching but the other three AIEgens did not show any stimuli–response. Single crystal structural analysis of Cz-MN, Cz-ECA and Cz-CA showed twisted molecular conformations with different intermolecular interactions. Both Cz-MN and Cz-ECA did not show any strong intermolecular interactions in the crystal lattice. In contrast, Cz-CA exhibited strong amide–amide complementary H-bonding and an extended network structure. Hence, the twisted molecular conformation and the absence of strong intermolecular interactions in Cz-MN and Cz-ECA contributed to self-reversible mechanofluorochromism (MFC). Thus, the present study is expected to provide further insight to design AIEgens with stimuli-responsive self-reversible fluorescent materials. [ABSTRACT FROM AUTHOR]

This work is devoted to the study of the influence of protonation on the photophysical properties of dimethylamino‐substituted styryl dyes. The formation of a bond on the unshared nitrogen electron pair involved in conjugation with the dye chromophore changes the mobility of the terminal group of the donor fragment and thereby "switches" the molecule from n‐π* to π‐π* mode. The correlations found between changes in the electron density of the dye in native form and during protonation and changes in its properties contribute to the study of the ground and excited states of these compounds and the energy transitions between them. Comparison with analog compounds and consideration of vibronic effects allow us to evaluate the potential advantages and limitations of the TD‐DFT method in the calculation of electronic transitions in styryl dyes. The work contributes to the understanding of the influence of protonation on the behavior of dyes with a nitrogen atom in the donor part of the chromophore of the molecule. The patterns found can be applied to similar chromophore systems. [ABSTRACT FROM AUTHOR]

We describe the synthesis, full photophysical study, and ab initio calculations of 2‐(2'‐hydroxyphenyl)benzazole (HBX) fluorophores substituted, at the meta position of the phenol group, by pyridine derivatives. HBX are commonly used as model dyes to study the stimuli‐induced modulation of the Excited State Intramolecular Proton Transfer (ESIPT) process. The meta‐substituted fluorophores reported herein, display a photophysical profile different from the previously reported ortho‐ and para‐substituted HBO pyridine isomers. Indeed, while all dyes undergo spontaneous deprotonation in neutral conditions, leading to highly emissive anionic species; upon protonation, ortho‐ and para‐pyridine substitution leads to resonance‐stabilized keto isomers, formed after ESIPT. Protonated meta derivatives, unable to stabilize their excited structure by such electronic delocalization process, display sizable intramolecular charge transfer (ICT) processes, translating into significantly redshifted emission. In addition, all dyes present a strong emission intensity, not only in neutral and acidic solutions, but also in the solid‐state. The nature of the emissive transitions was confirmed in each case by theoretical calculations combining Time‐Dependent Density Functional Theory (TD‐DFT) and second‐order Coupled Cluster (CC2) methods. [ABSTRACT FROM AUTHOR]

The newly synthesized chiral active [5]helicene‐like tetrabenzofluorene (TBF) based highly red‐emitting molecules exhibit flower‐like self‐assembly. These molecules display photophysical and structural properties such as intramolecular charge transfer, dual state emission, large fluorescence quantum yield, and solvatochromism. In TBFID, the indandione functional group attached on both sides as the terminal group offers an A‐D‐A push‐pull effect and acts as a strong acceptor to cause more redshift in solution as well as in solid state as compared to TBFPA (TBF with benzaldehyde functional group in terminal position). The self‐assembly studies of TBFID demonstrate the aggregation‐induced emission enhancement (AIEE) attributed to the restriction of intramolecular rotation at the aggregated state. Furthermore, TBFID shows high quantum yield and intense red emission, making the molecule fit for organic light‐emitting diodes (OLED) and bioimaging applications. [ABSTRACT FROM AUTHOR]

N‐type organic semiconductors are essential for the advancement of organic electronic devices. However, in relation to extensive research on n‐type and p‐type polymers, studies on high‐mobility n‐type small‐molecule semiconductors (SMSCs) are limited. Here, a series of ultra‐narrow bandgap n‐type SMSCs are developed on an A‐D‐A‐type structure. These SMSCs feature an exceptionally large π‐conjugated area, leading to strong intramolecular charge transfer and robust π‐π interactions. For the first time, central core and terminal halogenation are employed to control molecular surface electrostatic potential distribution, thereby regulating the π‐π stacking area (Sπ‐π) and studying their correlation. The research reveals that, in n‐type SMSCs with an edge‐on arrangement, introducing fluorine into the 2D central core can reduce the Sπ‐π, which is detrimental to the electron mobility (µe) of organic field‐effect transistors (OFETs). Conversely, terminal chlorination facilitates electron injection and improves µe. Consequently, DTPC‐OD‐4Cl, featuring shorter alkyl side chains and a non‐fluorinated 2D central core and undergoing terminal chlorination, achieved the highest µe of up to 0.52 cm2 V−1 s−1, ranking among the highest values reported for A‐D‐A type SMSCs. This work not only systematically investigated the influence of molecular structure on mobility but also provided novel insights for designing more efficient n‐type SMSCs. [ABSTRACT FROM AUTHOR]

We have developed new derivatives of Ruthenium metal complex-based dyes for use as sensitizers in DSSCs. Theoretical investigations have been conducted on ten Ruthenium metal complex clusters to analyse their geometries, electronic structures, density of states, optical properties, photovoltaic properties, and electrochemical properties. These investigations were carried out using the Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) methods. The objective was to design novel ligands that enhance the performance of dyes in dye-sensitized solar cells. We evaluated the impact of various chalcogen atoms in the ligand donor moieties, using different aromatic annulenes as building blocks. Additionally, we examined the influence of different functional groups connected to the bipyridyl unit in the ligand acceptor moiety. The designed dyes exhibit red-shifted spectra and improved electron transition abilities compared to other dyes, resulting in more effective intramolecular charge transfer upon photo-excitation. This suggests that these dyes would deliver the best photovoltaic performance. Furthermore, the designed dyes demonstrate a significantly enhanced light-harvesting efficiency, a higher open-circuit voltage (), a greater short-circuit current, and favourable electrochemical properties. These characteristics are crucial for achieving faster electron injection efficiency and higher performance in photovoltaic devices. [ABSTRACT FROM AUTHOR]

Imidazo[1,2‐c]quinazoline, a class of fused imidazole and quinazoline acceptor units, is widely established as biologically and broadly spectral active materials, while their optoelectronic properties were seldom investigated in the literature. In this context, this research work introduced two donors of varying strength, such as triphenylamine (TP) and phenothiazine (PZ) units, into the phenanthroimidazo [1,2‐c] quinazoline acceptor unit to form donor‐acceptor type luminescence materials such as TPQZ and PZQZ, respectively and were characterized by NMR and mass spectroscopy. Both these materials exhibited intramolecular charge transfer (ICT) type absorption (∼380–450 nm) and emission (∼540–600 nm) characteristics, which attributed to the electronic transition occurring from the HOMO of the TP/PZ donor to the LUMO+1 and LUMO+2 of the imidazo [1,2‐c] quinazoline acceptor unit, as predicted using DFT calculations. Increasing the electron donor strength was not only limited to fine‐tuning the π→π* based localized (∼400–450 nm) to ICT (∼450–650 nm) emission characteristics in both the solution and solid‐state conditions but also found to improve the zone of inhibition to 16 mm against Staphylococcus aureus/Bacillus subtilis bacterial species. The scope of realizing the luminescence nature of this acceptor unit is further expanded towards tagging biological samples such as E. coli. Overall, this work opens up a new paradigm in developing luminescent materials utilizing imidazo[1,2‐c]quinazoline acceptor unit for optoelectronic and biological applications. [ABSTRACT FROM AUTHOR]

A series of triphenylamine‐quinoxaline donor‐acceptor (bipolar) compounds (TPA‐QH, TPA‐QMe, TPA‐QCOOH and TPA‐QNO2) with different substituents were synthesized and investigated their fluorescence properties, including stimuli‐induced fluorescence responses in solution and the solid‐state. Single crystal structural analysis revealed non‐planar molecular conformation, substituent controlled intermolecular interactions and molecular packing in the crystal lattice. TPA‐QH, TPA‐QMe, TPA‐QCOOH and TPA‐QNO2 showed tunable solid‐state emission from green to red. TPA‐QH showed strong fluorescence at 487 nm (quantum yield (Φf)=28.3 %) whereas NO2 substituted TPA‐QNO2 exhibited relatively weak fluorescence at 610 nm (Φf=4.3 %). Density functional theoretical (DFT) calculations also indicated reduction of optical bandgap with substituting electron withdrawing group. The donor‐acceptor structure with intramolecular charge transfer (ICT) resulted solvent polarity dependent fluorescence tuning. The presence of acid responsive quinoxaline group was utilized to demonstrate pH‐responsive fluorescence switching and dual state fluorescence was utilized for fabricating rewritable fluorescent platform. Thus, the present study provides a structural insight to develop dual state emissive triphenylamine–quinoxaline based bipolar materials for optoelectronic applications. [ABSTRACT FROM AUTHOR]

The influence of pure solvent and binary solvent mixtures on the optical properties of non-steroidal anti-inflammatory drug (NSAID) molecule, specifically flufenamic acid (FLA), has been studied using absorption and fluorescence spectroscopic techniques. A bathochromic shift is observed in the emission wavelength of FLA with an increase in the solvent polarity of pure solvents, attributed to the highest stability of the excited state. The spectral properties are correlated with Lippert–Mataga, solvent polarity parameter, Kamlet, and Catalan solvent polarity parameters, suggesting that both general and specific solvent effects influence the spectral properties, with general solvent effects dominating over specific solvent effects. Preferential solvation studies have been carried out in tetrahydrofuran (THF) and water solvent mixture, revealing variations in the preference for solvation of FLA as a function of the mole fraction of water. Solvatochromic data are utilized to estimate the excited state dipole moment in pure solvents using different solvatochromic methods, revealing that the excited state dipole moment of FLA is higher than its ground state counterpart. The increase in dipole moment in the excited state compared to the ground state is explained based on intramolecular charge transfer (ICT), with elaboration and discussion on the possible resonance structure corresponding to ICT, inferring the more polar nature of the excited state compared to the ground state. The effect of solute polarizability on the excited state dipole moment and change in dipole moment is also discussed. [ABSTRACT FROM AUTHOR]

We propose a [4+1] annulation of sulfoxonium ylides with allyl ethers catalyzed by Rh(III), which leads to the formation of alkyl-substituted indanone derivatives. The reactions occur under mild conditions without external oxidants. The ylide serves as a traceless directing group in the subsequent annulation with allyl alkyl ethers via the (4+1) annulation. The process involves Csp2–H bond functionalization facilitated by AgBF4, generating DMSO as a separable byproduct. This redox–neutral reaction exhibits a good substrate scope and excellent yields toward the various alkyl allyl ethers. The molecular structures of the title compounds (3a, 3b, and 3c) are optimized at the DFT/B3LYP/6-311++G(d,p) level of the basis set. The hyperpolarizability (β0) values that are computed suggest that all molecules may behave in a nonlinear optical (NLO) manner. The Lewis (bonding) and non-Lewis (anti-bonding) structural types are calculated to investigate the intramolecular charge transfer inside the molecule. It appears that the molecule experiences intramolecular charge transfer based on the HOMO–LUMO transition. Understanding a molecule's reactive sites is possible by using its molecular electrostatic potential (MEP) surface. At various temperatures in the gas phase, the thermodynamic parameters of the title compounds, including entropy, heat capacity, and enthalpy, are calculated. Additionally, the anti-inflammatory and anti-diabetic performances of the above-synthesized compounds revealed better activity than their standard drug molecules. [ABSTRACT FROM AUTHOR]

Copper nanoclusters have attracted significant interest in the field of materials science due to their high abundance, complex structure, and unique properties. However, there is a limited amount of research on the relationship between structure and properties. In this study, we synthesized and comprehensively characterized two new Cu9 nanoclusters, [Cu9(PhSe)6(PPh2O2)3] (Cu9-1) and [Cu9(CH3OPhS)6(PPh2O2)3] (Cu9-2), in order to investigate the effect of ligands on photoluminescence. Both clusters have the same metal skeleton and similar distribution of ligands, with the only difference being the surface ligands (PhSe vs. CH3OPhS). Interestingly, the photoluminescence lifetime of Cu9-2 was found to be 3.2 times longer than that of Cu9-1. Furthermore, a notable Stokes shift (ST) was observed in the emission spectra of the two clusters. Single-crystal X-ray analysis revealed the formation of hydrogen bonds between neighboring clusters of Cu9-2, which influenced intramolecular interactions. Additionally, the methoxy groups in Cu9-2, acting as conjugated electron donors, promoted intramolecular charge transfer and π–π interaction. This study is expected to inspire further research on surface ligand engineering for controlling the properties of copper nanoclusters beyond photoluminescence. [ABSTRACT FROM AUTHOR]

Two o-carborane-hybridized macrocyclic arenes have been synthesized via Friedel–Crafts alkylation of carborane diaryl derivatives. The single-crystal X-ray diffraction analysis clearly revealed their cavity structure and intermolecular interaction force. These novel macrocycles exhibited aggregation-induced luminescence and intramolecular charge transfer properties and also significant selectivity towards nitro explosive compounds. This work provided a method for the synthesis of hybridized macrocyclic arenes. [ABSTRACT FROM AUTHOR]

A series of selectively cyanated spirofluorene‐bridged N‐heterotriangulenes (N‐HTAs) with three to nine cyano groups are synthesized via a newly developed synthetic strategy. X‐ray crystallographic analysis of the compounds revealed a tripod‐like molecular shape with the fluorenyl moieties arranged in a perpendicular fashion around the nitrogen‐centered N‐HTA core. The solid state packing is found to be strongly influenced by the dipolar cyano functions. Under electrochemical conditions, the N‐HTA core is prone to undergo a reversible one‐electron oxidation toward the nitrogen‐centered radical cation, which becomes increasingly difficult as the number of the cyano acceptors, and consequently the ionization potential, increases. While a clear bathochromic shift is observed in the steady‐state UV–vis absorption spectra, the fluorescence behavior is complex and strongly dependent on the position and number of the cyano groups. The compound with six cyano functions at the fluorenyl flanks is unique within the series and shows a broad emission maximum at 499 nm and an unusually large Stokes shift of 10 171 cm−1. Time‐resolved absorption and fluorescence measurements, supported by quantum chemical calculations, identified this spectroscopic signature to originate from fast and robust photoinduced intramolecular charge transfer. [ABSTRACT FROM AUTHOR]

This review focuses mostly on organic dye‐sensitized solar cells, as they are an attractive, environmentally friendly alternative to traditional silicon solar cells for the production of renewable energy at a lower cost. The dye chromophore is recognized as the central component of the DSSC device. To improve the electrochemical, photovoltaic, and absorption properties of organic sensitizing dyes, we have designed a series of eight new dyes Pi (i = 1.8) based on the DPA‐2 architecture (the reference molecule). We have investigated the effects of internal absorption of different acceptor groups in D‐Ai‐π‐A before and after binding to the TiO2 cluster surface on the ability to inject electrons into the surface. The benzophenothiazine is the D donor, the π‐spacer is furan, and the A acceptor is cycnoacrylic acid. We are using time‐dependent density functional theory (TD‐DFT), and density functional theory (DFT) in our quantum calculations. It is theoretically possible to predict suitable candidates for the DSSC device and identify correlations between their structure and properties by using DFT and TD‐DFT simulations to thoroughly study in detail electronic structures, natural binding orbital (NBO), analysis of UV‐visible absorption spectra, parameters influencing short‐circuit current density (JSC), open‐circuit voltage (VOC), and intramolecular charge transfer (ICT). Additionally, the relationship between optoelectronic properties and molecular structure was investigated, and the effect of auxiliary acceptor groups (Ai) on the primary photovoltaic properties of the reference molecule DPA‐2. The results show that by changing the internal acceptor to DPA‐2 could create a more coplanar and rigid structure. This would cause the energy gap (Eg) for each of the dyes created to significantly shrink, reducing it from 2.29 to 1.38 eV. The absorption spectra's λmax for each dye would also change color, this was because the acceptor moiety Ai of the phenothiazine moiety changed when it came to DPA‐2 (not including compounds P1 and P4). In contrast, P6 and P7 dyes demonstrate an absorption range beyond 500 nm, implying a more efficient utilization of sunlight in the visible spectrum compared to other dyes. Furthermore, all organic dyes show a robust LHE performance (0.919 to 0.993), correlating with the lowest ΔGreg values (0.097 to 0.356) and the most negative ΔGinject values (−2.067 to −1.121). The power conversion efficiency of PCE and JSC could increase according to these results. Therefore, theoretical research into adding a second internal acceptor group to the D‐Ai‐π‐A structure should produce new methods for improving solar energy output. [ABSTRACT FROM AUTHOR]

This study presents the design, synthesis, and comprehensive characterization of a novel series of D‐π‐A type malononitrile‐derived chromophores, BTC‐1–BTC‐4. Combining various spectroscopic techniques, nonlinear Z‐scan measurements, and quantum chemical calculations, we revealed the intricate relationship between nonlinear optical properties and the interplay of molecular structure, intramolecular charge transfer (ICT), and dipole moments (μ). Our experimental and computational findings corroborate that the polarization degree in the ground state, the charge separation in the excited state and twisted intramolecular charge transfer (TICT) collectively dictate the nonlinear optical properties of the compounds. Notably, BTC‐1 exhibits an exceptional nonlinear absorption coefficient β value (2×10−8 m W−1), attributed to its optimized charge transfer efficiency and pronounced degree of charge separation. Our findings provide actionable insights for the rational design of high‐performance organic Nonlinear optics (NLO) materials with potential applications in advanced photonic devices. [ABSTRACT FROM AUTHOR]

Near-infrared transparent films demonstrate important applications in many fields, but how to eliminate light interference from ultraviolet-visible region and how to tackle the trade-off effect between film thickness and transmittance remain as challenges. Herein, we report a near-infrared transparent film that achieves high-efficient combination of thin thickness (16 μm), suitable cut-off wavelength (890 nm), and ideal transmittance (TNIR > 90%, TVis < 1%). Moreover, the film is photo-chemically stable, heating resistance and moisture insensitive. The key component of the film is a complex of a specially designed boron compound containing a perylene monoimide unit (PMI-CBN) with an organic base 1,8-diazabicyclo[5,4,0]undec-7-ene. The complex depicts red-shifted absorption from 709 to 943 nm owing to deprotonation of the N-H group of PMI-CBN. Dispersion of the complex in polymethyl methacrylate results in the high-performance film. As demos, the film is successfully used for night vision imaging and information encryption. Near-infrared transparent films have a number of applications, but combining elimination of UV-vis light and the balance of film thickness and transmittance is challenging. Here, the authors report the development of a thin material with good transmittance and a suitable wavelength cutoff. [ABSTRACT FROM AUTHOR]

Developing red fluorescence emitters with simple structures via convenient synthetic routes is highly desirable yet challenging. Herein, two novel donor–acceptor-type red emitters, DCFOPV-TPA and SCFOPV-TPA, featuring the intramolecular charge transfer effect were designed by integrating triphenylamine and trifluoromethyl into a CN-substituted oligo(p-phenylene vinylene) backbone. Both chromophores exhibited aggregation-induced enhanced emission and solvatochromic behavior. Moreover, DCFOPV-TPA also displayed reversible mechanofluorochromic properties under external force. [ABSTRACT FROM AUTHOR]

We performed intra- and intermolecular charge transfer (CT) excitation energy calculations of (a) conjugated carbon chain [H2N–(CH=CH)n–X] and (b) its equidistant H2NH∙∙∙HX (n = 2~8) with various electron acceptors (X = NH2, OH, Cl, CHO, CN, and NO2) using EOM-CCSD, time-dependent (TD) Hartree–Fock (HF) and various density functional theory (DFT) functionals, such as BLYP, B3LYP, long-range corrected (LC) DFT, and LC-DFT with an optimally tuned (OT) range separation parameter (µ) using Koopman's theorem to investigate the effect of the electron-withdrawing (or -donating) strength of end-capped functional group (X) and CT distance (R) on intra- and intermolecular CT excitation energies. As the electron-withdrawing strength of X increases, both intra- and intermolecular CT excitation energies tend to decrease, since energy gaps between orbitals corresponding to CT excitations (e.g., HOMO and LUMO) decrease. However, the effect of the electron-withdrawing group on intramolecular CT excitation energy is negligible (at most 0.5 eV). OT-LC-DFT shows accurate intermolecular CT excitation energy, but worse results in intramolecular CT excitation energy than LC-DFT with the default µ value (0.47). Therefore, we conclude that the optimal tuning method is not effective in predicting intramolecular CT excitation energy. While intermolecular CT excitation energy has excitonic binding energy with asymptotic behavior to CT distance that is not affected by the choice of range separation parameter, intramolecular CT excitation energy is affected by orbital relaxation energy, which strongly depends on the choice of range separation parameter, which makes the OT method of range separation parameter ineffective in predicting intramolecular CT excitation energy as well as local excitation with high accuracy. [ABSTRACT FROM AUTHOR]

A tetraphenylethylene (TPE) derivative, TPEPhDAT, modified by diaminotriazine (DAT), was prepared by successive Suzuki–Miyaura coupling and ring-closing reactions. This compound exhibits aggregation-induced emission enhancement (AIEE) properties in the DMSO/MeOH system, with a fluorescence emission intensity in the aggregated state that is 5-fold higher than that of its counterpart in a dilute solution. Moreover, the DAT structure of the molecule is a good acceptor of protons; thus, the TPEPhDAT molecule exhibits acid-responsive fluorescence. TPEPhDAT was protonated by trifluoroacetic acid (TFA), leading to fluorescence quenching, which was reversibly restored by treatment with ammonia (on–off switch). Time-dependent density functional theory (TDDFT) computational studies have shown that protonation enhances the electron-withdrawing capacity of the triazine nucleus and reduces the bandgap. The protonated TPEPhDAT conformation became more distorted, and the fluorescence lifetime was attenuated, which may have produced a twisted intramolecular charge transfer (TICT) effect, leading to fluorescence redshift and quenching. MeOH can easily remove the protonated TPEPhDAT, and this acid-induced discoloration and erasable property can be applied in anti-counterfeiting. [ABSTRACT FROM AUTHOR]

Herein, nitrogen is doped into carbon quantum dots (N‐CQDs) using a hydrothermal method for the rapid detection of metolachlor in grain. The morphological features, elemental compositions, and optical properties of the N‐CQDs are then analyzed and investigated using transmission electron microscopy, X‐ray photoelectron spectroscopy, and fluorescence spectroscopy, respectively. Based on the principle of intramolecular charge transfer, a fluorescent probe is constructed for the rapid detection of metolachlor. Under optimal experimental conditions, the fluorescence intensity change values of the N‐CQDs and metolachlor concentration have a good linear relationship when the concentration of metolachlor is in the range of 0.0125−2.5 μg mL−1. An evaluation of the method shows that the method has good selectivity, reproducibility, and stability, with a limit of detection of 1.63 μg kg−1 and a limit of quantification of 3.92 μg kg−1. The spiked recoveries of six real samples are tested using a spiked recovery assay that yielded spiked recoveries in the range of 105.05−87.13%, and their relative standard deviations (n = 3) ranged from 4.62% to 0.61%, indicating that the method can be used for detection in actual samples with good precision and stability. [ABSTRACT FROM AUTHOR]

ABSTRACT The reaction between 2‐hydroxy‐1‐naphthaldehyde and 3‐hydrazino‐5,6‐diphenyl‐1,2,4‐triazine produced a novel hydrazone ligand (DTHMN), which reacted with Cu(II) and Zn(II) metal ion in molar ratio 1:1, giving octahedral Cu(II)‐DTHMN and tetrahedral Zn(II)‐DTHMN nanosized complexes. The structural geometries have been elucidated on the basis of elemental analysis, nuclear magnetic resonance, infrared, electronic, and electron spin resonance spectra, and magnetic and molar conductance measurements as well as x‐ray diffraction and thermal analysis. TEM analysis showed that Zn(II)‐DTHMN complex has nano‐rode morphology shape. On the other hand, Cu(II)‐DTHMN has sphere shape within nanodomain. The DTHMN ligand exhibits ONN chelating sites through N‐triazine ring, azomethine nitrogen, and deprotonated OH group, forming the mononuclear metal complexes. The synthesized compounds showed a distinct solvatochromic behavior in different polar solvents. A bathochromic alteration is observed when moving from less to high polar solvents, indicating strong solute–solvent interactions accompanied by intramolecular charge transfer (ICT). The ground and excited state dipole moments of these compounds were determined experimentally by solvatochromic shift method using Bilot–Kawski, Lippert–Mataga, Bakhshiev, and Kawski–Chamma–Viallet functions and a microscopic Reichardt's solvent polarity parameter (ETN). The dipole moment is increased significantly upon excitation referring to stabilizing the excited species includes n–π* transition by polarity of solvent. The experimental results are generally consistent with those values obtained by B3LYP/GENECP method at 6‐311G(d,p) basis set for C, H, N, and O atoms and SDD (Stuttgart/Dresden) basis set for the metal atoms. The compounds were tested for antimicrobial efficiency against Gram‐positive bacteria, Gram‐negative bacteria, and fungus strain. Finally, molecular docking was used to study the interactions between donors (the current compounds) and receptors FabH–CoA complex (PDB code: 1HNJ). [ABSTRACT FROM AUTHOR]

[Display omitted] Although photothermal therapy (PTT) is effective at killing tumor cells, it can inadvertently damage healthy tissues surrounding the tumor. Nevertheless, lowering the treatment temperature will reduce the therapeutic effectiveness. In this study, we employed 2,2′-((2Z,2′Z)-((4,4,9,9-Tetrahexyl-4,9-dihydro-s-indaceno[1,2- b :5,6- b ']dithiophene-2,7-diyl)bis(methanylylidene))bis(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)) dimalononitrile (IDIC), a molecule possessing a conventional acceptor–donor-acceptor (A-D-A) structure, as a photothermal agent (PTA) to facilitate effective mild photothermal therapy (mPTT). IDIC promotes intramolecular charge transfer under laser irradiation, making it a promising candidate for mPTT. To enhance the therapeutic potential of IDIC, we incorporated quercetin (Qu) into IDIC to form IDIC-Qu nanoparticles (NPs), which can inhibit heat shock protein (HSP) activity during the process of mPTT. Moreover, IDIC-Qu NPs exhibited exceptional water dispersibility and passive targeting abilities towards tumor tissues, attributed to its enhanced permeation and retention (EPR) effect. These advantageous properties position IDIC-Qu NPs as a promising candidate for targeted tumor treatment. Importantly, the IDIC-Qu NPs demonstrated controllable photothermal effects, leading to outstanding in vitro cytotoxicity against cancer cells and effective in vivo tumor ablation through mPTT. IDIC-Qu NPs nano-system enriches the family of organic PTAs and holds significant promise for future clinical applications of mPTT. [ABSTRACT FROM AUTHOR]

Donor–acceptor (D–A) structure with charge transfer (CT) effect is widely utilized in the construction of organic luminescent materials. The adjustment of their CT effect and related luminescent property usually relies on the changes of molecular structure with different D or A moieties, which will lead to some uncertainties in structure‐property relationship. With the aim to explore the clear inherent luminescent mechanism for D–A molecule with CT effect, it is ideal that the regulation of intramolecular charge transfer in one same D–A molecule can be realized. Accordingly, three D–A type organic phosphorescence luminogens are designed and synthesized. Once being doped into different polymer matrixes, disparate charge transfer effects and related room temperature phosphorescence (RTP) properties can be achieved for a single molecule. Subsequent experiments confirm that different distributions of molecules with locally excited (LE) state and CT state are mainly responsible for their distinct RTP behaviors, exhibiting the well‐clarified structure‐property relationship of D–A type phosphorescence luminogens. Furthermore, the transition from CT to LE state can even be realized through chemical reaction, leading to the activated RTP effect for practical applications. [ABSTRACT FROM AUTHOR]

A series of novel reactive dyes D1–D3 based on vinamidinium salt were designed and synthesized. Bis(monochlorotriazine) was introduced as the reactive group and sodium sulfonate was the water‐soluble group. Their photophysical properties were studied systematacially. The strong and sharp ground‐state absorption peak in the 250–320 nm range in the UV‐vis absorption spectrum of the aqueous solution could be attributed to the 1π–π* transition by the parent structure of the dyes, and the relatively broad absorption peak in the range of 300–650 nm could be attributed to the 1π–π* mixed intramolecular charge transfer. By applying this series of reactive dyes to the dyeing of four fabrics (silk, cotton, polyester/cotton blends, and polyester), the dyeing depths were in the range of 5.2–28.6 under salt‐free conditions. The results show that D3 with higher planarity can increase the dyeing depth. At length, fastening tests on dyed cotton fabrics and silk showed that this series of reactive dyes had a color fastness between grades 3 and 5 for abrasion and soap‐washing. In summary, these reactive dyes could be potential dyes for salt‐free dyeing applications. [ABSTRACT FROM AUTHOR]

Significant advances are made in understanding the structure‐property relationship in room‐temperature phosphorescence (RTP) materials. For example, intramolecular charge transfer (ICT) structural molecules based on electron donors(D) and electron acceptors(A) are an efficient method to achieve RTP. However, the ability to precisely regulate the singlet‐triplet energy gap (ΔEST) through molecular design to control RTP emissions remains constrained. Herein, a group of 4BN‐NP and 5BN‐NP isomers is reported with D and A position isomerization, where 4BN‐NP exhibits a photo‐induced orange afterglow phenomenon in PMMA. Calculations show that the spin‐orbit coupling (SOC) value of 4BN‐NP is greater compared to 5BN‐NP and the intersystem crossing (ISC) channel is more efficient, resulting in a smaller ΔEST value for 4BN‐NP. This indicates that the short ICT channel is more conducive to inducing phosphorescence emission. In addition, compound 4BN‐NP co‐doped with red fluorescent dyes (RhB, Rh6G, and RBNN) in PMMA produces phosphorescence resonance energy transfer (PRET), inducing red afterglow emission. Surprisingly, light‐activated yellow RTP can be obtained by attaching 4BN‐NP with polymethyl methacrylate (PMMA) to nylon filaments, and its phosphorescence intensity does not diminish even when it is immersed in water containing detergent solution, thus expanding the prospects of its application in textile encryption. [ABSTRACT FROM AUTHOR]

Hydrazine, a compound known for its toxicity to human health and the environment, finds extensive use across various industries and potentially contributes to several diseases. Hence, the accurate measurement of hydrazine levels is paramount. This study introduces three new aggregation induced emissive luminogens (AIEgens) GBY-7, GBY-8, and GBY-9 crafted from benzofuran infused with a dicyanovinylidene group, tailored specifically for hydrazine monitoring. These probes feature a D–π–A core with a rotor, providing an optimal fluorescent base. Additionally, a potent electron-attracting nitrile group aids in the nucleophilic addition of N2H4 to form hydrazone, thereby blocking the intramolecular charge transfer (ICT) process and inducing optical signal modulation. Notably, luminogens GBY-8 and GBY-9 exhibit high selectivity in detecting hydrazine amidst competing amine-based compounds, showing detection limits of 0.00020 mM and 0.0043 mM, respectively. [ABSTRACT FROM AUTHOR]

In comparison to the sensing activity, the reactivity of arsenite (AsO2−) is less explored. Herein, we focused on AsO2− reactivity studies based on its pKa and compared the study with other common anions. All three pKa values of arsenite are >9.0, affording a flexible working pH range to design a probe for reactivity studies. We designed and synthesized six pH dependent benzothiazole-based Schiff bases, namely, 1-(((6-nitrobenzo[d]thiazol-2-yl)imino)methyl)naphthalen-2-ol (1), 5-(diethylamino)-2-(((6-nitrobenzo[d]thiazol-2-yl)imino)methyl)phenol (2), 9-(((6-nitrobenzo[d]thiazol-2-yl)imino)methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol (3), 5-methoxy-2-(((6-nitrobenzo[d]thiazol-2-yl)imino)methyl)phenol (4), 4-(((6-nitrobenzo[d]thiazol-2-yl)imino)methyl)benzene-1,3-diol (5), and 2-(((6-nitrobenzo[d]thiazol-2-yl)imino)methyl)phenol (6), as probes for hydrolysis studies containing 5% water in acetonitrile. In spite of the presence of water in the solution, no hydrolysis was observed for all the probes in the absence of a salt. In the presence of selected sodium salts of various anions in solution, intramolecular charge transfer (ICT) was observed after the deprotonation of an aromatic hydroxy group at the ortho position with respect to the imine groups within the probes. Among the studied anions, selective AsO2− induced imine hydrolysis was observed for probes 1 and 4. In the case of 5 with both o- and p-hydroxy groups, no hydrolysis was observed in the presence of AsO2−. Probe 6 with only the o-hydroxy group showed very fast hydrolysis with poor selectivity. The p-hydroxy group in 4-(((6-nitrobenzo[d]thiazol-2-yl)imino)methyl)phenol (7) resulted in poor AsO2− induced hydrolysis. The aldehyde, which was generated after hydrolysis of probe 1, showed selective emission at 450 nm in the presence of AsO2−. The time dependent hydrolysis reaction of probe 1 controls the emission intensity enhancement. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) contamination of food has raised widespread public health concerns, leading to substantial medical and economic burdens. Herein, a 2D/0D heterojunction fluorescent probe (TCTG) with Schottky barriers (SB) is designed and synthesized, utilizing Ti3C2Tx MXene‐loaded graphene quantum dots (GQDs), for the detection of H2S during food spoilage. The microstructures observed through SEM and TEM reveal that uniformly sized GQDs are evenly attached to the surface of a monolayer Ti3C2Tx. The chemisorption between GQDs and Ti3C2Tx facilitates charge transfer and the formation of SB, resulting in intramolecular charge transfer (ICT) effects. With the introduction of H2S, TCTG(50%) exhibits the highest sensitivity, selectivity, and anti‐interference properties, with ultra‐fast fluorescence transient reaction (3s) and remarkably low detection limit of 41.82 ppb as well as noticeable color change. When TCTG(50%) reacted with H2S, the ICT effects are inhibited, leading to the recovery of photoinduced electron transfer (PET) and fluorescence quenching. Notably, probe TCTG is effectively utilized to detect changes in H2S levels in raw foods to assess their quality. Overall, the significance of this study is its potential to revolutionize food spoilage detection, offering a fast, reliable, and sensitive method to ensure food safety and reduce associated health and economic burdens. [ABSTRACT FROM AUTHOR]

The mechanism of dual fluorescence emission of a fluorophore is controversial ever since its first observation in p-N,N-dimethylaminobenzonitrile (DMABN). Excited state twisted intramolecular charge transfer (TICT) and planarized intramolecular charge transfer (PICT) models have been the two prominent theories used to explain the dual fluorescence mechanism in several systems. These mechanisms are based on excited state adiabatic structural changes of the fluorophore. Nevertheless, pieces of evidences based on excitation spectral measurements at different emission windows suggest the possibility of additional and/or alternative mechanisms based on ground state structural changes of the fluorophore. In this paper, we have presented a systematic steady-state absorption and fluorescence spectroscopy of a donor-pacceptor system, p-N,N-(dialkylamino)benzylidenemalononitrile, and related compounds in solvents of different polarities. The excitation spectrum of p-N,N-(dialkylamino) benzylidenemalononitrile is found to be dependent on the emission window. Furthermore, the emission spectra of the molecule are dependent on the excitation wavelength which suggest that the molecule consists of two stable ground state conformational isomers. The spectroscopic pieces of evidence together with results from DFT calculations are in favor of the solvent-induced ground state structural change of the fluorophore. Hence, two ground state conformers of p-N,N-(dialkylamino)benzylidenemalononitrile are attributed to the dual emission of the molecule. [ABSTRACT FROM AUTHOR]

A dyad Carbazolyl‐bis(hydrazinobenzothiazole) was designed to form a symmetrical structure that containing two‐arm active binding sites facilitates coordination with Hg2+ ion. This sensor has imparted a colorimetric and fluorometric changes in presence of Hg2+ ions. The ligand showed a selective blue shift in presence of Hg2+even in co‐existence with heavy metal ions with luminescence change from colorless to blue and colorless to green under day light. Enhanced Intramolecular charge transfer process is responsible for fluorescence transformation when ligand interacts with Hg2+ ion. The emission spectra showed a ratiometric response to increasing addition of Hg2+ ions. The sensor is capable of detecting above the lower concentration of 6.8025×10−8 M. The fluorescence efficiency of CBT‐2 with Hg2+ ion is quite stable under different co‐metal ions and wide range of pH 6 to 9. The sensor CBT‐2 forms a 1 : 1 stoichiometric complex with Hg2+ ions and the binding nature is confirmed from the 1H‐NMR, FTIR, and mass spectroscopic studies. The sensor CBT‐2 and its Hg2+ complex possess good binding nature to protein in Bovine Serum Albumin which could be good in biological applications. Additionally, wedevelop a practical application in real water sample analysis and electrochemical detection via oxidation potential discrimination. [ABSTRACT FROM AUTHOR]

RNA‐based tools for biological and pharmacological research are raising an increasing interest. Among these, RNA aptamers whose biological activity can be controlled via illumination with specific wavelengths represent an important target. Here, we report on a proof‐of‐principle study supporting the viability of a systematic use of Morita‐Baylis‐Hillman adducts (MBHAs) for the synthesis of light‐responsive RNA building blocks. Accordingly, a specific acetylated MBHA derivative was employed in the functionalization of the four natural RNA bases as well as two unnatural bases (5‐aminomethyl uracil and 5‐methylaminomethyl uracil). The results reveal a highly selective functionalization for both unnatural bases. The conjugation products were then investigated spectroscopically, photochemically and computationally. It is shown that when a single light‐responsive unit is present (i. e. when using 5‐methylaminomethyl uracil), the generated unnatural uracil behaves like a cinnamic‐framework‐based photochemical switch that isomerizes upon illumination through a biomimetic light‐induced intramolecular charge transfer mechanism driving a barrierless and, therefore, ultrafast reaction path. [ABSTRACT FROM AUTHOR]

Organic luminescent solid materials have attracted much attention due to practical applications such as sensor materials and optical waveguides. We have previously reported that inverse type diarylethenes exhibit strong emission in crystal without causing aggregation‐caused quenching. However, the emission color was limited to mainly green. To tune the emission color, in this work, we newly synthesized inverse type diarylethenes having a shortened π‐conjugation length or a polar substituent and investigated their fluorescence properties in solutions and crystals. The crystals exhibited various emission colors from blue, green, yellow to red depending on the molecular structure. The emission color changes of the crystals were induced by the intermolecular interactions such as CH‐π interactions in addition to the shortened π‐conjugation length and the intramolecular charge transfer character. [ABSTRACT FROM AUTHOR]

A series of methoxylated bis(pentafluorophenyl)boron‐β‐diketonates (dkB(C6F5)2) with intense emission has been synthesized and characterized by a variety of physicochemical methods. The photophysical properties of the synthesized compounds were thoroughly investigated by electronic absorption, steady‐state, and time‐resolved fluorescence spectroscopy in both solution and solid state. The studied compounds exhibit solvatochromic behavior attributed to the intramolecular charge transfer (ICT) nature of the first excited state. The formation of exciplexes between DBMB(C6F5)2 and benzene derivatives was also studied. Notably, the studied compounds display a complex luminescence profile in the solid state, featuring fluorescence, delayed fluorescence and phosphorescence emission. Furthermore, the hydrolytical stability of the complexes was assessed, demonstrating excellent resistance to hydrolysis. Estimated rate constants, determined at 60 °C, are significantly lower (90‐2000 times) than those observed for the well‐studied dibenzoylmethanatoboron difluoride (DBMBF2). The incorporation of pentafluorophenyl substituents at the boron atom enables the synthesis of highly fluorescent and hydrolytically stable boron chelate complexes, suitable for sensing and bioimaging applications in water‐containing environments. [ABSTRACT FROM AUTHOR]

Heterocyclic compounds based on 1,3,4‐oxadiazole (ODA) have attracted considerable attention in the field of pharmacy, drug discovery, and in the field of material sciences. This article reports a series of new highly twisted blue‐ and green‐emitting ODA‐based materials 4(a–e) utilizing a simple and efficient synthetic approach, resulting in high yield. The formation of multiple CN bonds unfolds via a simple nucleophilic method that does not need costly metal catalysts. The derivative structures were validated using analytical methods such as 1H NMR, 13C NMR, and high‐resolution mass spectrometry (HRMS). Using fluorescence spectroscopy, UV–Vis spectroscopy, and fluorescence lifetime measurements, a thorough investigation was carried out on the photophysical characteristics of the newly synthesized derivatives. A deeper understanding of intramolecular charge transfer was uncovered via solvent‐dependent spectroscopy. Specifically, these materials show a large stock shift of up to 153 nm and long fluorescence decay value between 8 and 8.6 ns. Computational methods pinned on density functional theory (DFT) were used to determine the highest occupied molecular orbital–lowest unoccupied molecular orbital energy gaps. The optical band gaps derived from absorption peaks and the band gaps computed by DFT computations are highly correlated. Using cyclic voltammetry study, the compounds' redox potentials were further investigated. These results indicate that the ODAs 4(a–e) are promising organic materials and could play an important role in the field of optoelectronic devices, bioimaging, and photo‐redox reactions. [ABSTRACT FROM AUTHOR]

Potent antioxidants, like 3-hydroxy flavones, attracted considerable attention due to their excited state intramolecular proton transfer (ESIPT)-based fluorescence behaviour. This article is an interesting demonstration of a series of synthetic 3-hydroxy flavone analogues having high antioxidant activity as molecular rotor-like viscosity probes. Among these flavone analogues, 4′-N,N-dimethylamino-3-hydroxy flavone (3) is the most potent one, showing the twisted intramolecular charge transfer (TICT)-dependent fluoroprobing activity toward the blood viscosity changes associated with diabetes and free fatty acids (FFA)-induced nuclear viscosity changes of MIN6 cells. The TICT dynamics of (3), which instigates its viscosity probing activity, was comprehended with the help of DFT-based computational studies. Abnormal cellular viscosity changes are the pathological traits for various diseases, and non-toxic flavone-based viscosity probes can be useful for diagnosing such pathological conditions. [ABSTRACT FROM AUTHOR]

Polyimide (PI) refers to a type of high-performance polymer containing imide rings in the main chain, which has been widely used in fields of aerospace, microelectronic and photonic devices, gas separation technology, and so on. However, traditional aromatic PIs are, in general, the inefficient fluorescence or even no fluorescence, due to the strong inter- and intramolecular charge transfer (CT) interactions causing unavoidable fluorescence quenching, which greatly restricts their applications as light-emitting functional layers in the fabrication of organic light-emitting diode (OLED) devices. As such, the development of fluorescent PIs with high fluorescence quantum efficiency for their application fields in the OLED is an important research direction in the near future. In this review, we provide a comprehensive overview of fluorescent PIs as well as the methods to improve the fluorescence quantum efficiency of PIs. It is anticipated that this review will serve as a valuable reference and offer guidance for the design and development of fluorescent PIs with high fluorescence quantum efficiency, ultimately fostering further progress in OLED research. [ABSTRACT FROM AUTHOR]

We have synthesized two boron complexes based on N,N‐type bidentate imidazo[1,5‐a]pyridine ligands exhibiting blue emission with good quantum yields in solution. The transient absorption and theoretical studies of the boron complexes indicated the intramolecular charge transfer nature. In addition, one specific complex, 1 a was found to work as a mitochondrial imaging agent. [ABSTRACT FROM AUTHOR]