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Herein we reported the synthesis of three positional isomeric (o-, m-, and p-) π-conjugated polyyne chromophores, in which three diethynylbenzene positional isomers were used as π-conjugated bridges, respectively. Subsequently, the structural characterization of the above positional isomers was accomplished by NMR, MS, IR, etc. Then, their electronic absorption, photoluminescence (PL) emissions, and electrochemiluminescence (ECL) properties were further investigated. The PL emissions of three π-conjugated polyyne chromophores were observed in the wavelength of ~325–510 nm. Interestingly, the para-isomer with a rigid planar π-conjugated structure exhibits the strongest UV-Vis absorption and fluorescence emission. Finally, the ECL measurements indicated that the three π-conjugated polyyne chromophores exhibited stable cathode ECL emission, providing excellent candidate materials for the future design and manufacturing of ECL emitters. [ABSTRACT FROM AUTHOR]

We report an unexpected direct transfer hydrogenation (TH) from 8-alkoxyjulolidine as a strong electron donor to tricyanofuran-based hemicyanines and tandem condensation for the synthesis of push–pull chromophores. Density functional theory calculations identify the α-hydride transfer of julolidine derivatives, instead of nucleophilic addition, as the key initial step of reaction cascades, followed by efficient β-deprotonation to generate a nucleophilic enamine of isojuloline that condenses in situ with a second equivalent of hemicyanines as electrophiles. The scheme represents an exceptional example of TH reactions from 8-alkoxyjulolidine to highly polarizable hemicyanines, notably under simple reaction conditions without using potent catalysts of metal complexes or Lewis acids. The resulting products of isojuloline-based merocyanines exhibit strong near-infrared (NIR) absorption and large first hyperpolarizabilities. The study suggests that direct TH can be exploited to construct new NIR merocyanines by following rational, regioselective condensation pathways for photonic applications. [ABSTRACT FROM AUTHOR]

Two new monopyridyl‐based Anthracene and Pyrene ligands were synthesized and employed to design Ruthenium‐coordinated organometallic complexes, RuAnthra and RuPyrene, respectively. The ligands and their metal complexes were fully characterized by different analytical techniques, including multinuclear 1D‐ and 2D‐NMR, electrospray ionization‐mass spectrometry, UV–Vis, fluorescence spectroscopy, and elemental analysis. Furthermore, their photophysical properties were studied in different solvents with increasing polarity using UV–Vis and fluorescence spectroscopy, showing less or no significant solvolysis effect. The average emission lifetimes of the complexes were further determined using time‐resolved emission spectroscopy. Additionally, the ligands and their metal complexes showed excellent ability to generate singlet oxygen and can be useful for several important potential applications. [ABSTRACT FROM AUTHOR]

Partial genetically encoded 4-hydroxybenzylidene-imidazolinone (HBI)-type chromophores are new promising fluorescent probes, which are suitable for imaging and detection of living cells. However, the lack of infrared chromophores hinders the development seriously. Here more than 30 HBI-type chromophores with regular structure modifications were employed and typical spectral redshift change laws and mechanisms were investigated by quantum methods. Results show that both one-photon spectrum (OPS, absorption/emission) and two-photon absorption (TPA) can achieve large redshift via either extending conjugated lengths of frag-3 or enlarging conjugated areas of frag-1 of HBI skeleton. Spectral redshifts of all chromophores are highly related to intramolecular charge transfer (ICT), but neutral ones are closely related to the total ICT or electron-accepting-numbers of frag-3, and the high correlative factor of anions is the aromaticity of frag-2 bridge. The frag-2 bridge with high aromaticity can open a reverse charge transfer channel in anion relative to neutral, obtaining significant redshift. Based on analysis, a new 6-hydroxyl-naphthalene-imidazolinone (HNI) series, which have larger conjugated area in frag-1, are predicted. The OPS and TPA of anionic HNI ones acquire about 76–96 nm and 119–146 nm red-shift relative to traditional HBI series respectively as a whole. The longest emission of anionic HNI-4 realizes more 244 nm redshift relative to HBI-1. Our work clarifies worthy spectral regularities and redshift mechanisms of HBI-type chromophores and provides valuable design strategy for infrared chromophores synthesis in experiment. [ABSTRACT FROM AUTHOR]

Herein we report two anthracene-thiophene based π-conjugated homologues, in which the synthesis and structural characterizations were accomplished by NMR, HR-MS, etc. Subsequently, their electron absorptions, photoluminescence (PL) emissions, and electrochemiluminescence (ECL) properties were further investigated. Interestingly, in the visible region of ~400–550 nm, both of the two homologous chromophores displayed strong PL emissions. Finally, intense and stable cathodic ECL emissions in the visible region of ~400–1000 nm for the title compounds were further observed, which provided excellent potential candidates for the future construction of high-performance ECL emitters. Besides, the phenyl group substituted homologue exhibited more intense in fluorescence spectrum, while relatively weak in ECL emission, which added new insights into the structure-properties relationships of anthracene-thiophene containing π-conjugated luminescent materials. [ABSTRACT FROM AUTHOR]

Different strategies are utilized to design and synthesize remarkable non‐linear optical (NLO) materials. Herein, we have synthesized hydrazinylthiazole‐4‐carbohydrazides based eight derivatives (HZ1–HZ8) by condensation reaction of thiazole‐4‐carboxylates with hydrazine monohydrate. The structural interpretation of carbohydrazides was carried out with spectroscopic techniques i. e. FT‐IR, 1H‐NMR, 13C‐NMR and HRMS. For the exploration of varied terminal moieties impact, NLO properties of entitled compounds (HZ1–HZ8) were investigated via employing density functional theory (DFT) computations at B3LYP level along with 6‐31G(d,p) basis set. Aforementioned functional was utilized to acquire optimized geometries at true minima, non‐linear optical (NLO), UV‐Visible (UV‐Vis), frontier molecular orbital (FMO) and natural bond orbital (NBO) analyses. Moreover, dipole moment (μ), average linear polarizability and first order hyperpolarizability (βtot.) were computed for all the synthesized chromophores (HZ1–HZ8). However, HZ5 displayed the maximum value of βtot (2710.8 a.u.) as compared to all the other investigated compounds. From the discussion, it can be concluded that, this study of hydrazone‐based derivatives believed to be a significant contribution for achieving proficient NLO materials. In a nutshell, HZ5 might be contemplated as a highly efficient material for advanced NLO applications owing to its maximum nonlinear optical response. [ABSTRACT FROM AUTHOR]

Coumarin and its heterocyclic derivatives have been receiving tremendous attention from synthetic and medicinal chemists owing to their remarkable application in material science as well as pharmacological applications. In the current study, a series of coumarin‐coupled benzothiazole hydrazone compounds were synthesized by a two‐step process, post which their structural features were investigated with the aid of various spectroscopic techniques. The novel synthesized chromophores displayed an electronic absorption band in a range of 358–428 nm and exhibited a positive solvatochromism character as well as a high molar absorption coefficient in the studied solvents. HOMO‐LUMO gap, quantum parameters, and various other pharmacokinetics and ADME‐T properties of these compounds were investigated through the computational approach. Biological activity assays revealed that all compounds displayed excellent antibacterial activity compared to the Amoxicillin and have also been studied for their antimycobacterial efficacy against Mycobacterium tuberculosis. Furthermore, molecular docking studies was performed with enoyl‐acyl carrier protein reductase (InhA). [ABSTRACT FROM AUTHOR]

The facile synthesis of chromophores with near-infrared (NIR) absorption and emission is of particular interest due to their wide range of applications. Here we report a one-step synthesis of amino-functionalized perylenediimides exhibiting NIR absorption and emission via a catalyst-free amino–yne click reaction. We also demonstrate the post-modification of polyethylenimine by the click reaction, resulting in the formation of a polymeric NIR chromophore with an emission peak at 913 nm in the solid state. [ABSTRACT FROM AUTHOR]

Amine groups are common constituents of organic dyes and play important roles in tuning fluorescence properties. In particular, intensive research works have demonstrated the tendency and capabilities of amines in influencing chromophore brightness. Such properties have been explained by multiple mechanisms spanning from twisted intramolecular charge transfer (TICT) to the energy gap law and beyond, which introduce additional nonradiative energy dissipation pathways. In this review, we aim to provide a focused overview of the mechanistic insights mainly for the TICT mechanism, accompanied by a few other less common or influential fluorescence quenching mechanisms in the amine-containing fluorescent molecules. Various aspects of current scientific findings including the rational design and synthesis of organic chromophores, theoretical calculations, steady-state and time-resolved electronic and vibrational spectroscopies are reviewed. These in-depth understandings of how the amine groups with diverse chemical structures at various atomic sites affect excited-state nonradiative decay pathways will facilitate the strategic and targeted development of fluorophores with desired emission properties as versatile chemosensors for broad applications. [ABSTRACT FROM AUTHOR]

Novel D-π-A′-π-A chromophores with quinoxaline cores as auxiliary acceptors and various donor moieties (aniline, carbazole, phenothiazine, tetrahydroquinoline) containing bulky tert-butyldimethylsilyloxy (TBDMSO) groups and tricyanofuranyl (TCF) acceptors with bulky cyclohexylphenyl substituents were synthesized via eight- to nine-step procedures, and their photo-physical and thermal properties were investigated. The values of the chromophores' first hyperpolarizabilities were calculated in the framework of DFT at the M06-2X/aug-cc-pVDZ computational level; the effect of the introduction of the TBDMSO group into the donor fragment is shown to be inessential, as this group is not coupled to the π-conjugated system of the chromophore. The chromophore with the tetrahydroquinoline donor has a first hyperpolarizability value of 937 × 10−30 esu, which is the highest for the studied chromophores. Atomistic modeling of composite materials with the studied chromophores as guests demonstrated that the presence of bulky substituent in the donor fragment prevents notable aggregation of chromophores, even at high chromophore content (40 wt.%). The nonlinear optical performance of guest–host materials with 25 and 40 wt.% of suggested chromophore content was studied using a second harmonic generation technique to give the NLO coefficient, d33 up to 52 pm/V. [ABSTRACT FROM AUTHOR]

The [2+2] cycloaddition ‐ retro‐electrocyclization (CA‐RE) reaction is a "click‐like" protocol for facile synthesis of donor‐acceptor chromophores from an alkyne and tetracyanoethylene. Herein we shed light on the mechanism of this reaction by detailed kinetics studies using 1H NMR spectroscopy. By considering several experiments simultaneously, a variety of mechanistic models was evaluated. Surprisingly, a model in which the final 1,1,4,4‐tetracyanobuta‐1,3‐diene product promoted the first step was the only one that described well the experimental data. This autocatalysis model also involved a non‐concerted, stepwise formation of the cyclobutene cycloaddition adduct. By proper choice of conditions, we were able to generate the transient cyclobutene in sufficient amount to verify it as an intermediate using 13C NMR spectroscopy. For its final retro‐electrocyclization step, simple first‐order kinetics was observed and only minor solvent dependence, which indicates a concerted reaction. [ABSTRACT FROM AUTHOR]

D--π--A chromophores with indole donor and tricyanofuranyl acceptor moieties connected by vinylene and divinyl quinoxalinone π-conjugated bridges have been sythesized and their linear and nonlinear optical properties were studied. Chromophores exibit intramolecular charge-transfer (ICT) absorption band in the visible region, positive solvatochromism, and are transparent at 850 nm. The indole-based chromophore with divinylquinoxalinone π-conjugation bridge shows large µβ value (~13000•10-48esu); the incorporation of the vinyl quinoxalinone unit leads to a significant increase in the values of the first hyperpolarizability. [ABSTRACT FROM AUTHOR]

Merocyanines with embedded butadiene structure in a cyclohexane scaffold are readily obtained by consecutive three-component alkynylation-addition sequences in moderate to excellent yield. Moreover, employing pyrrolidine as an amine provides a pseudo four-component synthesis of related cyanines by carbonyl condensation of the heterocyclic amine in excellent yield. While the merocyanines are essentially nonluminescent, pentamethine cyanines show luminescence with low quantum yield. TDDFT calculations using various exchange correlation hybrid functionals in the gas phase and explicit continuum of dichloromethane underline that the lowest energy absorption bands are highly solvent dependent for a merocyanine and cyanine model. The blue-shifted deviation from the experimental spectra agrees with related merocyanine and cyanine systems. The lowest energy absorption band of merocyanines contains n-π* character, which rationalizes the absence of luminescence. [ABSTRACT FROM AUTHOR]

The effect of substituents in the aniline donor and the type of heterocyclic acceptor/donor moieties on the yields of 1,2-trans- and 1,1-isomer ethylene D-π-A chromophores in Pd-catalyzed Heck reaction has been studied. Various D-π-A chromophores – derivatives of quinoline, quinoxaline, benzothiazole, carbazole and indolizine – were synthesized. [ABSTRACT FROM AUTHOR]

Luminescent metal–organic frameworks (MOFs) have emerged as interesting materials due to their excellent photophysical and photochemical properties. Herein, we report the synthesis of a Zn‐based MOF AnDBP MOF derived from anthracenedicarboxylic ligand and dipyridyl boron dipyrromethene (BODIPY) chromophore. The single‐crystal structure of AnDBP MOF showed a noninterpenetrated network structure with zinc metal binding the ligands in an octahedral fashion. The AnBDP MOF showed efficient energy transfer between the linkers and also displayed excellent photocatalytic properties. [ABSTRACT FROM AUTHOR]

The review covered the works published after 2000 and is devoted to the synthesis of azo chromophores with nonlinear optical (NLO) properties that were estimated experimentally or theoretically. Since NLO properties are manly exhibited by the polymeric materials, the clear understanding of the paths leading to symbiotic relationship between azo chromophore and polymer is required. New strategy to the NLO materials involves the introduction of the guest chromophores into the azo chromophore-containing dendritic polymer host, namely, the use of two different chromophores in the same polymer matrix. [ABSTRACT FROM AUTHOR]

An efficient, mild, and environment‐friendly methodology for the synthesis of azomethine chromophores through the reaction of 2‐aminobenzonitrile derivatives and acetophenones has been developed using CuCl (10 mol %) catalyst and toluene as a solvent under visible light irradiation. The reaction proceeds readily at room temperature under 20 W white LED with good to excellent yields in short reaction time. This methodology shows significant advantages such as environmentally benign reaction conditions, sustainability, enumerating tolerance of wide range of functional groups, cost‐effectiveness, high atom economy, short reaction time, and applicability for large‐scale synthesis. [ABSTRACT FROM AUTHOR]

Free base and zinc porphyrins functionalized with cyclooctatetraene (COT), a molecule known as a good triplet‐state quencher, have been obtained and characterized in detail by structural, spectral, and photophysical techniques. Substitution with COT leads to a dramatic decrease of the intrinsic lifetime of the porphyrin triplet. As a result, photostability in oxygen‐free solution increases by two to three orders of magnitude. In non‐degassed solutions, improvement of photostability is about tenfold for zinc porphyrins, but the free bases become less photostable. Similar quantum yields of photodegradation in free base and zinc porphyrins containing the COT moiety indicate a common mechanism of photochemical decomposition. The new porphyrins are expected to be much less phototoxic, since the quantum yield of singlet oxygen formation strongly decreases because of the shorter triplet lifetime. The reduction of triplet lifetime should also enhance the brightness and reduce blinking in porphyrin chromophores emitting in single‐molecule regime, since the duration of dark OFF states will be shorter. [ABSTRACT FROM AUTHOR]

A series of chromophores bearing 4‐cyanoquinazoline, 2‐(4‐cyanophenyl)quinazoline or 2‐(4‐trifluorophenyl)quinazoline electron–acceptor (A) and 5‐(4‐aminophenyl)thiophen‐2‐yl or 4‐aminophenyl electron‐donor (D) units has been designed. The influence of the electron‐withdrawing substituent on the pyrimidine core as well as the nature of the amino electron donating group has been studied by cyclic voltammetry, UV/Vis and emission spectroscopy. Whereas 2‐(4‐cyanophenyl)quinazoline and 2‐(4‐trifluorophenyl)quinazoline derivatives are highly luminescent in chloroform solution, 4‐cyanoquinazolines are poorly emissive. Interestingly all compounds are luminescent in the solid state with the emission ranging from blue to red. The second order nonlinear optical properties were studied using electric field induced second harmonic generation (EFISH) method. Quantum‐chemical calculations corroborate the aforementioned experimental results. [ABSTRACT FROM AUTHOR]

The photophysical properties of a series of conjugated push–pull (iso)quinolines were studied. The compounds were synthesized by well‐established and straightforward methodologies. The materials exhibited not only emission solvatochromism in a variety of nonpolar solvents, but also tunable halochromism. Some of the compounds remained moderately luminescent after protonation and had a red emissive form, which was used to obtain white‐light emission, both in solution and in thin films, by controlled protonation of the initially blue–green‐emitting materials. This methodology has potential applications in the fabrication of white organic light‐emitting diodes with two forms of a single emitter in equilibrium. [ABSTRACT FROM AUTHOR]

We propose a new protocol for synthesis of the arylidene‐1H‐imidazol‐5(4H)‐ones which is based on O‐alkylation of amidoacetates using triethyloxonium tetrafluoroborate leading to carboximidates. These imidates have long been used in the synthesis of imidazolones by [2+3] cycloaddition reaction with Schiff bases. However, diversity of carboximidates prepared by the common techniques was limited. The protocol we proposed eliminated these limitations. Using this technique, a number of derivatives of the green fluorescent protein (GFP) and asFP chromophores were synthesized, and influence of the C2 residue on their optical properties was studied. [ABSTRACT FROM AUTHOR]

Organic luminogens with persistent room‐temperature phosphorescence (RTP) have found a wide range of applications. However, many RTP luminogens are prone to severe quenching in the crystalline state. Herein, we report a strategy to construct a donor‐sp3‐acceptor type luminogen that exhibits aggregation‐induced emission (AIE) while the donor‐sp2‐acceptor counterpart structure exhibits a non‐emissive solid state. Unexpectedly, it was discovered that a trace amount (0.01 %) of the structurally similar derivative, produced by a side reaction with the DMF solvent, could induce strong RTP with an absolute RTP yield up to 25.4 % and a lifetime of 48 ms, although the substance does not show RTP by itself. Single‐crystal XRD‐based calculations suggest that n–σ* orbital interactions as a result of structural similarity may be responsible for the strong RTP in the bicomponent system. This study provides a new insight into the design of multi‐component, solid‐state RTP materials from organic molecular systems. [ABSTRACT FROM AUTHOR]

Two novel nonlinear optical (NLO) chromophores JC-T-TCF and JC-F-TCF utilizing tetramethyljulolidine-based coumarin and tricyanofuran(TCF) as the electron donor and acceptor, respectively, were designed and synthesized. The two chromophores were linked with different π conjugated electron bridge (thiophene group and furan group), which provide the opportunity to study the structure–property relationship of coumarin-based chromophores. Both the novel obtained chromophores exhibited reasonable stability and solvatochromic effect. The theoretical calculation results indicated that both chromophores possess microscopic hyperpolarizability (β) in excess of 320 × 10−30esu, and the chromophore JC-T-TCF utilizing thiophene group as the electron bridge exhibited obviously larger β value (456.8 × 10−30esu). The larger β value, combination with the larger µ value, endowed JC-T-TCF with larger electro-optic activity of 70 pm V−1 at the wavelength of 1310 nm in the guest–host films of chromophores doped into PMMA, which provide the potential application opportunity in the field of optical waveguide devices. [ABSTRACT FROM AUTHOR]

The weak fluorescence (quantum yield <1 % in cyclohexane) of phenothiazine (PTZ) impedes its further application. In addition, the nitro group (NO2) is a well‐known fluorescence quencher. Interestingly, we obtained a highly fluorescent chromophore by combining these two moieties, forming 3‐nitrophenothiazine (PTZ‐NO2). For comparison, a series of PTZ derivatives bearing electron‐withdrawing groups (EWGs; CN and CHO) or electron‐donating groups (EDGs; OMe) at the 3‐position have been designed and synthesized. The phenothiazines bearing EWGs exhibited enhanced emission compared with the parent PTZ or EDG derivatives. Computational approaches unveiled that for PTZ and PTZ‐OMe, the transitions are from HOMOs dominated by π orbitals to LUMOs of mixed sulfur nonbonding–π* orbitals, and hence are partially forbidden. In contrast, the EWGs lower the energy level of the lone‐pair electrons on the sulfur atom, thereby suppressing the mixing of the nonbonding orbital with the π* orbital in the LUMO, such that the allowed ππ* transition becomes dominant. This work thus demonstrates a judicious chemical design to fine‐tune the transition character in PTZ analogues, with PTZ‐NO2 attaining 100 % emission quantum yields in nonpolar solvent. [ABSTRACT FROM AUTHOR]

Betaine is an essential nutrient for humans and a source of methyl donors for methionine and S‐adenosylmethionine formation, and it is used as a biomarker for pharmacological activities and to evaluate the quality of Lycium species and common foods. However, because of its special structural features, poor ultraviolet‐chromophore, and high polarity, the existing methods for betaine extraction and quantification cannot provide higher extraction efficiency, better sensitivity, or resolution degree. A simple, fast, and efficient high‐performance liquid chromatography–diode array detector coupled with solid‐phase extraction was adopted for simultaneous separation and quantification of betaine in four types of Lycium species. The results revealed that after degreasing with dichloromethane, extraction with 80% ethanol (pH adjusted to 1.0 with hydrochloric acid), and elution with aluminum oxide (OH− form), the improvement in the average yield rate of betaine was thrice of that of the existing methods. In addition, trigonelline was identified as the interfering substance of betaine for the first time in Lycium species, and betaine and trigonelline were simultaneously separated and quantified. Furthermore, their chemical characteristics and content distribution in different Lycium species were carried out. [ABSTRACT FROM AUTHOR]

A ferrocenyl‐based, chromophore‐containing 1‐indanone derivative was synthesized through crotonic condensation between 4‐chlorobutylferrocenecarboxaldehyde and 5,6‐dimethoxy‐1‐indanone followed by the nucleophilic substitution of chlorine atom of the obtained dyad with different aromatic and aliphatic amines. The electrochemical and optical properties of the synthesized compounds were investigated to explore the relationship between their structures and optical and electrochemical properties. The bandgaps determined from optical absorption spectra ranged from 2.05 to 2.15 eV. The important electrochemical parameters, including the peak potential separation, peak current ratios, and the dependence of peak currents on the scan rate, were studied. Results showed an electrochemically reversible redox system with diffusion‐controlled redox process for the synthesized compounds. The study of quantum chemistry was performed on the synthesized compounds using the density functional theory approach. The B3LYP method and 6‐311 G(d) basis set were used for optimizing the structures in the gas phase. The theoretical and experimental results show that these compounds can be considered as candidates to be used in optical applications. [ABSTRACT FROM AUTHOR]

The preparation of an entirely supramolecular, multichromophoric azaborondipyrromethene (ABDP)/zinc tetraphenylporphyrin (ZnTPP)/exfoliated graphene (GR) nanoensemble was accomplished. The ABDP derivative bears glycol chains for enhancing solubility and a pyridine functionality for allowing coordination with ZnTPP. The ABDP/ZnTPP/GR nanoensemble was characterized in terms of morphology and composition by using complementary microscopy imaging, thermogravimetric analysis, Raman as well as steady‐state and time‐resolved absorption and emission spectroscopy. The photophysical and electrochemical assessment of ABDP/ZnTPP/GR as well as the binding properties of the ABDP/ZnTPP complex, employed as a reference, are presented. Energy and electron transfer events were observed in ABDP/ZnTPP upon photoexcitation. However, in the case of ABDP/ZnTPP/GR, the graphene‐induced aggregation of the chromophores alters their electronic interactions, enhancing the energy/electron transfer process between them. [ABSTRACT FROM AUTHOR]

To turn on the fluorescence of the native green fluorescence protein (GFP) chromophore, 4‐hydroxybenzylidene‐dimethylimidazolinone (HBDI), in an artificial supramolecular system has been a challenging task, because it requires high local environmental rigidity. This work shows that the formation of H‐aggregates of an HBDI‐containing organogelator results in two orders of magnitude fluorescence enhancement (Φf=2.9 vs. 0.02 %), in which the inter‐HBDI OH⋅⋅⋅OH H‐bonds play a crucial role. The aggregation‐induced fluorescence enhancement of HBDI has important implications on the origin of the high fluorescence quantum efficiency of HBDI in the GFP β‐barrel and on the supramolecular strategy for a full fluorescence recovery of HBDI. These results reveal a new approach to designing rigid chromophore aggregates for high‐performance optoelectronic properties. [ABSTRACT FROM AUTHOR]

The electronic circular dichroism (ECD) exciton chirality method is very useful for determining the absolute configuration (AC) of chiral compounds. In the ECD spectroscopy, the chromophore‐chromophore interaction, ie, exciton coupling, is very important. For example, Harada and Nakanishi first discovered in 1969 that chiral dibenzoates exhibit exciton split bisignate Cotton effects, from the sign of which the screw sense between two long axes of benzoate chromophores, ie, the AC of dibenzoate, can be determined. This method was named the dibenzoate chirality rule and has been successfully applied to various natural products to determine their ACs. During these studies, it was also found that this CD method was expanded to encompass other aromatic and olefin chromophores like naphthalene, diene, enone, etc. Therefore, the name of the dibenzaote chirality rule was changed to the CD exciton chirality method. In 1970s, there were heated controversies about the inconsistency between X‐ray Bijvoet and CD exciton chirality methods, which was a shocking and serious problem in the community of molecular chirality research. Harada and coworkers synthesized the most ideal cage compound with two anthracene chromophores to connect X‐ray Bijvoet and CD exciton chitality methods and proved that these two methods are consistent with each other. [ABSTRACT FROM AUTHOR]

Vesicular photothermal therapy agents (PTAs) are highly desirable in photothermal therapy (PTT) for their excellent light-harvesting ability and versatile hollow compartments. However, up to now, the reported vesicular PTAs are generally self-assembled from small molecules like liposomes, and polymer vesicles have seldom been used as PTAs due to the unsatisfactory photothermal conversion efficiency resulting from the irregular packing of chromophores in the vesicle membranes. Here we report a nano-sized polymer vesicle from hyperbranched polyporphyrins with favorable photothermal stability and extraordinarily high photothermal efficiency (44.1%), showing great potential in imaging-guided PTT for tumors through in vitro and in vivo experiments. These excellent properties are attributed to the in situ supramolecular polymerization of porphyrin units inside the vesicle membrane into well-organized 1D monofilaments driven by π–π stacking. We believe the supramolecular polymerization-enhanced self-assembly process reported here will shed a new light on the design of supramolecular materials with new structures and functions. Photothermal therapy (PTT) has recently emerged as a promising approach for cancer therapy. Here, the authors report a hyperbranched polymer vesicle with favorable photothermal stability and high photothermal efficiency for PTT through a supramolecular polymerization-enhanced self-assembly strategy. [ABSTRACT FROM AUTHOR]

We describe the synthesis, electrochemistry, photophysics, computational analysis and electrochemiluminescence (ECL) of a new series of oxazaborine molecules. Our strategy is based on the modification of the coumarin‐oxazaborine moiety to be directly joined through a carbon‐carbon bond, forming donor‐acceptor (D‐A) chromophores. These new structures substantially change the electron distribution as well as photophysical and electrochemical behaviors with a strong effect on the final quantum yield. For all compounds, we observed a very high PL quantum yield (70–75 %) and relatively accessible first oxidation and first reduction. All of these characteristics allow us to study the ECL of these molecules, obtaining a very high ECL efficiency that is four times higher than the standard dyes, opening the application of oxazaborine as bright ECL luminophores. [ABSTRACT FROM AUTHOR]

Photoinduced polymerization reactions are an energy‐saving and environmentally friendly technology used in applications such as curing and coating. Photo initiators are one of the key materials which generate active species by photoirradiation. Many types of radical and cationic photo initiators (photoacid generators) have been developed. However, anionic photo initiators (photobase generators), which are more advantageous in terms of corrosion and lack of deactivation, remain under development. Cyclic amidine compounds, such as DBU® (1,8‐Diazabicyclo[5.4.0]undec‐7‐ene) and DBN (1,5‐Diazabicyclo[4.3.0]non‐5‐ene), are strong organic bases, widely used as catalysts in organic, polymerization, and crosslinking reactions. Developing a photobase initiator that can generate such a strong base is important, because there are few photobase generators with strong basicity and high reactivity for practical applications. In this study, we investigated the elementary mechanism of photolysis of quaternary amidinium borate salts by transient absorption measurements. We confirm that photoinduced electron transfer is a key step in the photo decomposition of quaternary amidinium borate salts and that the position of the sensitizing chromophore in the molecules significantly affects the decomposition efficiency. [ABSTRACT FROM AUTHOR]

We report the synthesis and photophysical characterization of π‐expanded quinoidal triplet chromophores which exhibit attractive light‐harvesting properties. The kinetic of the triplet excited state of quinoidal benzotetraphene 2 was found to be one order of magnitude higher than the lifetime of 3(1)* from the less conjugated parent chromophore 1. Furthermore, the evaluation of the optoelectronic properties indicates that π‐expansion helps narrow the optoelectronic band gap, but the influence of the additional aromatic rings in the structure of 2 and 3 compromises the stability of the p‐quinoidal ring. QDM 2 was isolated and fully characterized; however, it was found to rearomatize to a mixture of uncharacterized radical species. [ABSTRACT FROM AUTHOR]

The article discusses the response of the retinal in microbial rhodopsin NM-R3 from the marine flavobacterium Nonlabens marinus to photostimulation which appears to be substantially different from that seen in bacteriorhodopsin. Topics discussed include the diversity of mechanisms for biological energy conversion, structural determination of early intermediate photoexcited states of NM-R3 by laser pulses and structural differences of NM-R3 by photoexcitation.

This study was aimed at investigating the effect of electron donor and acceptor groups on electrical and optical properties of pi-conjugated [26] annulene. The results of the study showed that almost all selected substitutions reduced the value of E g compared with pristine annulene. Calculated dipole moments for the sandwiched forms of annulene are noticeably greater than those of its pristine form, of which the ED2–ANN–QB2 had the maximum value for dipole moment. It was found that the influence of electron donor and acceptor groups on annulene optical properties is very significant. More optical activity improvement was seen in the case of using QB2 and QB3 in one side and other electron donor groups in opposite side of [26] annulene molecule. The higher optical activity of these sandwiched molecules corresponds to higher electron transfer in them. The results of this research may be useful in designing new photosensitizers. [ABSTRACT FROM AUTHOR]

The first representatives of D–π–A chromophores containing a hydroxytricyanopyrrole (HTCP) acceptor and N,N-disubstituted aminophenyl donor were synthesized. The obtained molecules include reactive NH- and OH-fragments allowing the photophysical properties of the chromophores to be tuned, which is not possible for the well-known chromophores of the tricyanofuran (TCF) and tricyanopyrrole (TCP) series. The absorption properties of the synthesized HTCP-chromophores with a p-aminophenyl electron donor substituent were thoroughly studied. [ABSTRACT FROM AUTHOR]

Channelrhodopsins (ChRs) belong to the unique class of light-gated ion channels. The structure of channelrhodopsin-2 from Chlamydomonas reinhardtii (CrChR2) has been resolved, but the mechanistic link between light-induced isomerization of the chromophore retinal and channel gating remains elusive. Replacements of residues C128 and D156 (DC gate) resulted in drastic effects in channel closure. T127 is localized close to the retinal Schiff base and links the DC gate to the Schiff base. The homologous residue in bacteriorhodopsin (T89) has been shown to be crucial for the visible absorption maximum and dark–light adaptation, suggesting an interaction with the retinylidene chromophore, but the replacement had little effect on photocycle kinetics and proton pumping activity. Here, we show that the T127A and T127S variants of CrChR2 leave the visible absorption maximum unaffected. We inferred from hybrid quantum mechanics/molecular mechanics (QM/MM) calculations and resonance Raman spectroscopy that the hydroxylic side chain of T127 is hydrogen-bonded to E123 and the latter is hydrogen-bonded to the retinal Schiff base. The C=N–H vibration of the Schiff base in the T127A variant was 1674 cm−1, the highest among all rhodopsins reported to date. We also found heterogeneity in the Schiff base ground state vibrational properties due to different rotamer conformations of E123. The photoreaction of T127A is characterized by a long-lived P2380 state during which the Schiff base is deprotonated. The conservative replacement of T127S hardly affected the photocycle kinetics. Thus, we inferred that the hydroxyl group at position 127 is part of the proton transfer pathway from D156 to the Schiff base during rise of the P3530 intermediate. This finding provides molecular reasons for the evolutionary conservation of the chemically homologous residues threonine, serine, and cysteine at this position in all channelrhodopsins known so far. [ABSTRACT FROM AUTHOR]

The title pull–push chromophores, 2-[4-(di­methyl­amino)­benzyl­idene]-1H-indene-1,3(2H)-dione, C18H15NO2 (ID[1]) and (E)-2-{3-[4-(di­methyl­amino)­phen­yl]allyl­idene}-1H-indene-1,3(2H)-dione, C20H17NO2 (ID[2]), have donor–π-bridge–acceptor structures. The mol­ecule with the short π-bridge, ID[1], is almost planar while for the mol­ecule with a longer bridge, ID[2], is less planar. The benzene ring is inclined to the mean plane of the 2,3-di­hydro-1H-indene unit by 3.19 (4)° in ID[1] and 13.06 (8)° in ID[2]. The structures of three polymorphs of compound ID[1] have been reported: the α-polymorph [space group P21/c; Magomedova & Zvonkova (1978). Kristallografiya, 23, 281–288], the β-polymorph [space group P21/c; Magomedova & Zvonkova (1980). Kristallografiya, 25 1183–1187] and the γ-polymorph [space group Pna21; Magomedova, Neigauz, Zvonkova & Novakovskaya (1980). Kristallografiya, 25, 400–402]. The mol­ecular packing in ID[1] studied here is centrosymmetric (space group P21/c) and corresponds to the β-polymorph structure. The mol­ecular packing in ID[2] is non-centrosymmetric (space group P21), which suggests potential NLO properties for this crystalline material. In both compounds, there is short intra­molecular C—H∙∙∙O contact present, enclosing an S(7) ring motif. In the crystal of ID[1], mol­ecules are linked by C—H∙∙∙O hydrogen bonds and C—Hπ inter­actions, forming layers parallel to the bc plane. In the crystal of ID[2], mol­ecules are liked by C—H∙∙∙O hydrogen bonds to form 21 helices propagating along the b-axis direction. The mol­ecules in the helix are linked by offset π–π inter­actions with, for example, a centroid–centroid distance of 3.9664 (13) Å (= b axis) separating the indene rings, and an offset of 1.869 Å. Spectroscopic and electrochemical measurements show the ability of these compounds to easily transfer electrons through the π-conjugated chain. [ABSTRACT FROM AUTHOR]

Reactions of N-methylated adenine (9-methyladenine and 3-methyladenine) with water-soluble oxalato complexes have probed their capability to anchorage to 1D metal-oxalato polymeric chains. The non-covalent interactions among the nucleobases and with the metal-oxalato framework have been studied in detail as well as the magnetic interactions mediated by the bridging oxalato ligand. Reactions of N-methylated adenine (9-methyladenine and 3-methyladenine) with water-soluble oxalato complexes in the presence of potassium oxalate yields a series of oxalato-bridged complexes with the nucleobases as pendant ligands whose crystal structures and magnetic properties are reported herein. The complexes [M 2 (µ-ox) 2 (9Meade) 3 ] n [M(II) = Zn (1), Cu (2); where ox = oxalato and 9Meade = 9-methyladenine] are composed of infinite corrugated one-dimensional chains in which two types of metal(II) centres are sequentially bridged by asymmetric bis-bidentate oxalato ligands and their coordination polyhedra are filled by N7-coordinated 9-methyladenine molecules giving rise to two different chromophores: an octahedral N 2 O 4 donor set with the nucleobase moieties in trans -arrangement, and square based pyramidal NO 4 coordination polyhedra. The cohesiveness of their supramolecular 3D architectures is achieved by means of an extensive network of non-covalent interactions including a short contact between the minor groove N3 site of the model 9-methyladenine and the oxalato bridging ligand from a neighbouring chain. This unconventional interaction between the lone pair of the pyrimidinic nitrogen atom of the nucleobase and the π-system of the oxalate anion has been analysed and discussed in the light of available structural data for analogous systems. The compounds {[M(µ-ox)(H 2 O)(3Meade)]·H 2 O} n [M(II) = Zn (3), Co (4) and Mn (5); where 3Meade = 3-methyladenine], and {[Cu(µ-ox)(3Meade) 2 ]·4H 2 O} n (6) are comprised of zig–zag metal-oxalato chains, with the oxalato adopting a symmetric bis-bidentate coordination mode. The octahedral environment of the metals is completed in a cis -arrangement by one water molecule and the imidazole N7 donor site of a 3-methyladenine ligand for 3 – 5 , and by two N7-coordinated nucleobases for 6. The crystal packing of the chains leads to the presence of channels with dimensions of 5 × 10 Å for 6 , and 4 × 6 Å for 3 – 5 which are occupied by crystallization water molecules. The non-covalent interactions of the nucleobases among them and with the metal-oxalato framework have been studied in detail as well as the magnetic interactions mediated by the bridging oxalato ligand. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells (DSSCs) are becoming increasingly popular as low-cost organic photovoltaic devices due to their ease of fabrication and affordability. However, a primary limitation of DSSCs is their inability to absorb the entire solar spectrum, leading to lower efficiency. To overcome this limitation, a study was conducted to investigate the use of co-sensitization with two dyes that absorb different wavelengths of light to enhance the overall light absorption. In this study, four novel donor-acceptor (D-A) dyes (5a-d) containing benzo-1,4-diazine or benzo-1,4-oxazine groups as donors and a carbonyl group as an anchor were synthesized using a green and sustainable method to be used as co-sensitizers in DSSCs. These photosensitizers were co-sensitized with the Ru(II) dye N719 and were observed to significantly improve the light-harvesting ability of the device. The co-sensitizers (5a-d) reduced charge recombination, inhibiting dye aggregation, and increased dye loading on the TiO 2 photoanode, leading to improve the overall device performance because of the appropriate molecular volume structures of (5a-d) , which can fill the adsorption gap between N719 dye. The DSSC device of N719 showed a power conversion efficiency (PCE) of 7.81 % (J SC = 19.06 mA cm−2, V OC = 0.65 V, and FF = 61.24%). After co-sensitization, the PCE and short-circuit current of the device were significantly improved to reach (PCE = 8.79, J SC = 22.89 mA cm−2 and V OC = 0.68 V for 5a), (PCE = 8.56%, J SC = 22.37 mA cm−2, and V OC = 0.68 V mA cm−2 for 5b), (PCE = 8.59%, J SC = 22.45 mA cm−2, and V OC = 0.67 V for 5c) and (PCE = 8.50%, J SC = 21.93 mA cm−2, and V OC = 0.67 V for 5d). These findings demonstrate that co-sensitization with these novel dyes can compensate for the absorption defects of the Ru(II) dye and suppress charge recombination, leading to enhanced overall PCE in DSSCs. The graphical abstract is showing the impact of using a small organic co-sensitizer on improving the efficiency of converting light energy into electrical energy in a benchmark N719 complex. The co-sensitizer is being used to enhance the performance of the N719 complex, which is being used as a benchmark in the study. [Display omitted] • Novel simple photosensitizers/co-sensitizers were synthesized using visible light photoredox catalysis for DSSCs. • Co-sensitization with (5a-d) photosensitizers improved the power conversion efficiency (PCE) of N719 benchmark in DSSCs. • The enhanced PCE of N719 is attributed to the densely packed mixture of dyes on the TiO 2 surface. • A maximum PCE of 8.79 % was achieved with a co-sensitization mixture of 0.2 mM N719 and 0.2 mM 5a dye. [ABSTRACT FROM AUTHOR]

Focusing on the remarkably various cyclometalated Pt(ii) acetylcetonate complexes bearing an isomeric donor (D)–acceptor (A) conjugation framework ligand by virtue of adjusting the nitrogen atom coordination position, we have systematically investigated the geometric and electronic structures, redox properties, polarizabilities, first hyperpolarizabilities (βtot), and first hyperpolarizability densities of these intriguing isomeric Pt(ii) complexes using density functional theory with the view to rationalizing the nonlinear optical (NLO) structure–function relationships. Our calculations demonstrated that modulating the coordination position that affects the intramolecular D–A interactions gives rise to large second-order NLO responses in the studied complexes, which are qualitatively elucidated in terms of the change in the charge transfer (CT) patterns using time-dependent density functional theory. In particular, for complex 2, coordination with the stronger electron donating capacity of triphenylamine and the electron-withdrawing ability of the [1,2,5]thiadiazolo[3,4-c]pyridine unit produces the highest βtot value (329 × 10−30 esu) owing to the obvious bidirectional CT transition, which is the most fascinating candidate for a NLO material among all of the investigated complexes. Significantly, a noteworthy finding was that remarkable βtot contrasts were observed for these isomeric Pt(ii) complexes upon redox process, illustrating that they could be applicable for efficient redox-triggered NLO switches, especially using an oxidation stimulus with the highest on/off ratio, approaching 168.6 for complex 3. Furthermore, we have also quantitatively investigated the solid-state polarization effects on the βtot values for neutral complexes using the polarizable continuum model. Therefore, it can be anticipated that the present work may be advantageous to the experimental and theoretical design of novel smart cyclometalated Pt(ii) complexes for functional NLO materials. [ABSTRACT FROM AUTHOR]

We report the synthetic routes to mono‐ and di‐TCBD adducts onto N‐(het)arylpyrrole derivatives. We present herein two series of panchromatic chromophores bearing different combinations of donor–acceptor moieties. Additionally, we observe an impact of the nature of the central core. Cyclic voltammograms show very different behaviors at negative potentials between the two series. Particularly, four waves are observed for symmetrical di‐TCDB adducts, thus indicating a communication through the central unit despite the non‐planarity of these molecules. [ABSTRACT FROM AUTHOR]

• This work expands the scope of formal [2 + 2] cycloadditions. • The reported cycloadditions occur under ambient conditions without any catalyst. • The flexibility of the method allowed for the easy variation of triazenes. 1-(4-Ethynylphenyl)-3,3-dialkyltriaz-1-enes, well-known building blocks for branched dendrimer syntheses, were utilized as a new type of electron-donor component in formal [2 + 2] cycloadditions. The click-type, atom-economic reactions proceed efficiently under ambient conditions without any catalyst. The resulting products are structurally interesting push-pull chromophores and were investigated in the context of optoelectronic properties using UV/Vis spectroscopy, NMR studies, and computational chemistry. [ABSTRACT FROM AUTHOR]

Highlights • A new chromophore was investigated. • Phenothiazine with rich electron sulfur and nitrogen heteroatoms was introduced. • The new structure chromophore showed good nonlinear optical properties. Abstract A novel chromophore based on the phenoxazine and tricyanofuran acceptor linked together via thiophene as the bridges have been synthesized by the conventional technique and systematically investigated. Structure analysis and photophysical properties were carried out to investigate the new structure chromophore. Density functional theory was used to calculate the hyperpolarizability (β) and the result shows that chromophore A showed a lower energy gap. In addition, chromophore A displayed good thermal stability with the onset decomposition temperature over 240 °C. These results showed that chromophore A, which had good thermal stability and nonlinear optical properties was a promising candidate for practical use. [ABSTRACT FROM AUTHOR]

Abstract On the basis of great diverse applications of nonlinear optical (NLO) materials, organometallic complexes have attracted considerable attention. In this paper, we present a detailed investigation on a series of Pt(II) dithienylcyclopentene(DTE)-based complexes via density functional theory method with the aim of evaluating their structures, electronic absorption spectra and first hyperpolarizabilities. The calculations demonstrate that the first hyperpolarizabilities can be enhanced by the introduction of quinolone into the complexes because of the enlarged spatial separation of electron density. However, Pt(II) complexes containing perfluorocyclopentene ring exhibit decreasing NLO response attributed to lower amount of charge transferred and short effective CT distance. The static first hyperpolarizabilities (β tot) of monometallic Pt(II) complexes are larger than those of bimetallic Pt(II) complexes due to correlative mixed charge-transfer patterns. More importantly, the closed-ring (1c) complex comprising DTE unit exhibits the largest β tot value approaching 144 × 10−30 esu, with the contrast over five times compared to corresponding open-ring due to the better π-conjugated delocalization and smaller HOMO and LUMO energy gap. In general, we envision our work will be beneficial for further rational design of DTE-containing Pt(II) complexes as high performance NLO materials. Graphical abstract Image 1 Highlights • Monometallic Pt(II) DTE-based complexes exhibit the largest β tot values. • The second-order NLO response of bimetallic Pt(II) complexes can be altered by various ligands. • The switching of NLO properties has been achieved by photoisomerization. [ABSTRACT FROM AUTHOR]

• Pyridyl-benzimidazole-functionalized PDI derivatives were designed and synthesized. • The electronic tuning provided by the bay-substitution with different electron donating/accepting capability of the groups. • The effect of substituents in bay positions of PDIs derivatives on the photo-physical properties was discussed. • DFT and electrochemical studies suggest that these triads are suitable for use in electrochromic devices as color changing materials. These color changing materials have potential usages in electrochromic devices. • These triads have pronounced electron-accepting properties. In this study, four new perylene diimide (PDI) derivatives incorporating 2-(2′-pyridyl)-1H-benzimidazole (2PBI) chromophores at the imide positions, in which 1 bearing non-bay-substituted perylene core, and those having four substituents at 1,6,7,12-bay positions of the perylene core, namely 2 bearing electron-withdrawing chlorine atoms, 3 bearing electron-donating 4-methoxyphenoxy groups and 4 bearing non-electron-donating 4- tert -butylphenoxy groups, respectively were synthesized and fully characterized by FT-IR, 1H NMR, 13C NMR, MALDI-TOF mass spectrometry and UV/Vis spectroscopy. The thermal properties were measured by thermogravimetric analysis (TGA) which showed that the materials (1 - 4) are thermally very stable (T d > 450 °C). DFT was performed for geometry optimizations, and TDDFT was used to compare the calculated and the experimental UV/Vis electronic spectra at the B3LYP/6–311 G(d) level. Detailed measurements were carried out by the use of electroanalytical, spectroscopic and colorimetric techniques in order to understand redox natures, color changes and optoelectronic characters of the novel compounds. These 2PBI-functionalized PDI triads showed reversible reduction processes, chemically stable reduced species and considerably low HOMO-LUMO band gaps, as the new worthy members of photoactive charge transport materials for optoelectronic and photovoltaic systems. In addition, with distinct color changes associated with their redox processes in the solution, these new triads displayed great capacity for application in electrochromic devices. The emission maxima of the compounds were found to be red shifted in the solid state. [ABSTRACT FROM AUTHOR]

• Carbon dots (CDots) exploit unique properties of small carbon nanoparticles. • Carbon nanoparticles represent another 0-D carbon allotrope beyond fullerenes. • The core nanoparticles can be modified by selected chromophores for hybrid CDots. • The hybrid CDots exhibit integrated electronic structures and properties. • The hybrid CDots may enable optical and redox properties by design. Carbon dots (CDots) exploit unique properties of small carbon nanoparticles, which represent the often under-appreciated zero-dimensional carbon allotrope. The carbon nanoparticles in CDots could be modified by a selected organic chromophore of desired strong red/near-IR absorption in the dot synthesis to obtain a specific type of hybrid CDots. The reported results show that these hybrid CDots derived from the modification of core carbon nanoparticles by selected dyes or other chromophoric species represent a highly versatile and effective platform for CDots of desired optical properties and photoinduced redox characteristics in a by-design fashion. [ABSTRACT FROM AUTHOR]

A noble-metal-free chromophore–catalyst supramolecular assembly, which is composed of an organic thermally activated delayed fluorescence (TADF) chromophore and cobaloximes, has been designed and synthesized for the first time for the efficient acceptorless dehydrogenation of secondary amines under blue light irradiation at room temperature. The TADF chromophore has a long lifetime of 17.4 μs with suitable redox potentials for the selective acceptorless dehydrogenation of secondary amines to afford imines and H2 through cooperative catalysis of the chromophore and cobaloximes in the supramolecular assembly. A high TON of 895 was obtained for the acceptorless dehydrogenation of 1,2,3,4-tetrahydroisoquinoline despite its high oxidation potential (+1.38 V vs. SCE). [ABSTRACT FROM AUTHOR]

An improved D−A‐D typed π‐conjugated optical chromophore (PBHPI) with multi‐activated recognition sites and its functionalized testing‐paper strips were constructed and developed, for the first time, based on B3LYP/6‐31G level of theory in Gaussian 03 suite. After its UV‐vis spectral property was investigated in detail, it was noted to find that the target PBHPI and its functionalized paper strips could conclusively react with F− with obvious color change from light yellow to dark red. Under the optimized experimental conditions, both PBHPI and its functionalized paper‐strips could selectively recognize F− with a double‐wavelength colorimetric response to realize a wide linear range from 5.0 ×10–6 mol/L to 1.4 ×10–4 mol/L. The present sensing systems were successfully applied for visually on‐site monitoring F− in some commercial organic and toothpaste samples simply and conveniently. The recognition mechanism was confirmed to be the deprotonating mechanism to form multiple hydrogen bonds as what we expected. [ABSTRACT FROM AUTHOR]