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An exciton–phonon (ex–ph) model based on our recently developed block interaction product basis framework is introduced to simulate the distal charge separation (CS) process in aggregated perylenediimide (PDI) trimer incorporating the quantum dynamic method, i.e., the time-dependent density matrix renormalization group. The electronic Hamiltonian in the ex–ph model is represented by nine constructed diabatic states, which include three local excited (LE) states and six charge transfer (CT) states from both the neighboring and distal chromophores. These diabatic states are automatically generated from the direct products of the leading localized neutral or ionic states of each chromophore's reduced density matrix, which are obtained from ab initio quantum chemical calculation of the subsystem consisting of the targeted chromophore and its nearest neighbors, thus considering the interaction of the adjacent environment. In order to quantum-dynamically simulate the distal CS process with massive coupled vibrational modes in molecular aggregates, we used our recently proposed hierarchical mapping approach to renormalize these modes and truncate those vibrational modes that are not effectively coupled with electronic states accordingly. The simulation result demonstrates that the formation of the distal CS process undergoes an intermediate state of adjacent CT, i.e., starts from the LE states, passes through an adjacent CT state to generate the intermediates (∼ 200 fs), and then formalizes the targeted distal CS via further charge transference (∼ 1 ps). This finding agrees well with the results observed in the experiment, indicating that our scheme is capable of quantitatively investigating the CS process in a realistic aggregated PDI trimer and can also be potentially applied to exploring CS and other photoinduced processes in larger systems. [ABSTRACT FROM AUTHOR]

Fluorescence-encoded infrared (FEIR) spectroscopy is a recently developed technique for solution-phase vibrational spectroscopy with detection sensitivity at the single-molecule level. While its spectroscopic information content and important criteria for its practical experimental optimization have been identified, a general understanding of the electronic and nuclear properties required for highly sensitive detection, i.e., what makes a molecule a "good FEIR chromophore," is lacking. This work explores the molecular factors that determine FEIR vibrational activity and assesses computational approaches for its prediction. We employ density functional theory (DFT) and its time-dependent version (TD-DFT) to compute vibrational and electronic transition dipole moments, their relative orientation, and the Franck–Condon factors involved in FEIR activity. We apply these methods to compute the FEIR activities of normal modes of chromophores from the coumarin family and compare these predictions with experimental FEIR cross sections. We discuss the extent to which we can use computational models to predict the FEIR activity of individual vibrations in a candidate molecule. The results discussed in this work provide the groundwork for computational strategies for choosing FEIR vibrational probes or informing the structure of designer chromophores for single-molecule spectroscopic applications. [ABSTRACT FROM AUTHOR]

Interfacial electron transfer (IET) through saturated single-linker and dual-linker groups from a perylene chromophore into nanostructured TiO2 films was studied by ultrafast spectroscopy. Perylene chromophores with one and two propanoic acid linker groups in the peri and ortho positions were investigated. In comparison to previously studied perylenes bound via unsaturated acrylic acid linkers, the chromophores with saturated linkers showed bi-exponential IET dynamics. Two distinct transfer times were observed that indicate the presence of two concurrent binding modes. A comparison between ortho- and peri-substituted sensitizers resulted in slower IET dynamics and weaker electronic coupling for ortho substitution. Finally, IET from sensitizers with saturated linker groups is neither promoted nor hindered by a second linker group. This indicates that only one of the two linkers binds covalently to the surface. This study reveals the importance of the anchor-binding mode and design considerations of the linker for regulating IET. [ABSTRACT FROM AUTHOR]

Predicting the energy differences between different spin-states is challenging for many widely used ab initio electronic structure methods. We here assess the ability of the direct random phase approximation (dRPA), dRPA plus two different screened second-order exchange (SOX) corrections, and σ-functionals to predict adiabatic singlet-triplet gaps. With mean absolute deviations of below 0.1 eV to experimental reference values, independent of the Kohn–Sham starting point, dRPA and σ-functionals accurately predict singlet-triplet gaps of 18 organic chromophores. The addition of SOX corrections to dRPA considerably worsens agreement with experiment, adding to the mounting evidence that dRPA+SOX methods are not generally applicable beyond-RPA methods. Also for a series of linear acene chains with up to ten fused rings, dRPA, and σ-functionals are in excellent agreement with coupled-cluster single double triple reference data. In agreement with advanced multi-reference methods, dRPA@PBE and σ-functional@PBE predict a singlet ground state for all chain lengths, while dRPA@PBE0 and σ-functional@PBE0 predict a triplet ground state for longer acenes. Our work shows dRPA and σ-functionals to be reliable methods for calculating singlet-triplet gaps in aromatic molecules. [ABSTRACT FROM AUTHOR]

The solvent effects on the linear and second-order nonlinear optical properties of an aminonaphtylethenylpyridinium (ANEP) dye are investigated by combining experimental and theoretical chemistry methods. On the one hand, deep near infrared (NIR) hyper-Rayleigh scattering (HRS) measurements (1840–1950 nm) are performed on solutions of di-8-ANEPPS in deuterated chloroform, dimethylformamide, and dimethylsulfoxide to determine their first hyperpolarizablity (βHRS). For the first time, these HRS experiments are carried out in the picosecond regime in the deep NIR with very moderate (≤3 mW) average input power, providing a good signal-to-noise ratio and avoiding solvent thermal effects. Moreover, the frequency dispersion of βHRS is investigated for Disperse Red 1 (DR1), a dye commonly used as HRS external reference. On the other hand, these are compared with computational chemistry results obtained by using a sequential molecular dynamics (MD) then quantum mechanics (QM) approach. The MD method allows accounting for the dynamical nature of the molecular structures. Then, the QM part is based on TDDFT/M06-2X/6-311+G* calculations using solvation models ranging from continuum to discrete ones. Measurements report a decrease of the βHRS of di-8-ANEPPS in more polar solvents and these effects are reproduced by the different solvation models. For di-8-ANEPPS and DR1, comparisons show that the use of a hybrid solvation model, combining the description of the solvent molecules around the probe by point charges with a continuum model, already achieves quasi quantitative agreement with experiment. These results are further improved by using a polarizable embedding that includes the atomic polarizabilities in the solvent description. [ABSTRACT FROM AUTHOR]

Organic chromophores emerged as diverse functional materials in the areas of organic catalysis, toxic materials sensing, bio-imaging, and organic electronic devices. With rich chemical and electronic structures, main-group elements have been extensively implanted in organic chromophores to fine-tune the chemical/electronic structures and optoelectronic properties. In this Synpact article, we present a concise overview of the development of phosphorus (P)-containing organic chromophores, further highlighting our recent contributions in the field. A new aspect of combining the P element with the indole moiety was pursued to construct a new series of seven-membered P-organic chromophores; namely, indole-functionalized phosphepines. The new combination endowed the system with rich chemical and electronic structures, for which intriguing photophysical properties were consequently revealed. The combination provided an efficient synthetic protocol to access new P-heterocycles and also offered a new strategy to design functional organic chromophores. [ABSTRACT FROM AUTHOR]

Harvesting triplet excitons of heavy atom‐free purely organic chromophores under aerated conditions is challenging due to the quenching of long‐lived triplet states by molecular oxygen and vibrational dissipation. Herein, we show a supramolecular approach of triplet harvesting via mitigating quenching pathways of a triplet harvester. Specifically, we used a host–guest system based on 2,3 : 6,7‐naphthalene bis(dicarboximide)‐derived cyclophane (NBICy) and carbazole derivative (EtCz). Complexation studies and single‐crystal X‐ray analysis showed the formation of a rigid host–guest complex (K≈104 M−1 in CCl4), resulting in triplet‐exciton stabilization under aerated conditions via mitigating vibrational interference and oxygen quenching. Photophysical studies elucidate the delayed fluorescence emission from the charge‐transfer state (1CT) with a quantum yield (QY) of 6–8 % under ambient conditions which increased up to 36 % in an inert atmosphere. [ABSTRACT FROM AUTHOR]

ABSTRACT Herein, a series of fluorinated quinoxaline core–based chromophores (MTH1‐MTH6) with A1–π–A2–π–A1 configuration was designed by structural modulation of end‐capped acceptors in MTHR. The quantum chemical calculations were accomplished at MPW1PW91/6‐311G(d,p) functional to explore optoelectronic and photovoltaic properties of these designed compounds. The findings revealed that all the derivatives exhibited narrow band gap (Egap = 2.163–2.666 eV) with red shift spectra (610.24–766.944 eV in chloroform) as compared with MTHR. The designed compounds exhibited comparable open‐circuit voltage (Voc) and higher power conversion efficiencies (PCEs) as compared with the MTHR. Among the entitled chromophores, MTH1 was found to be a promising chromophore for organic solar cells (OSCs) owning to its lowest Egap (2.163 eV) with highest absorption peak (766.944 nm in chloroform and 717.709 nm in gaseous phase). The aforementioned findings indicate that molecular engineering of chromophores with extended acceptors enhances photovoltaic response, and this motivates researchers to develop highly effective photovoltaic devices. [ABSTRACT FROM AUTHOR]

Background/Objectives: Based on Blind Source Separation and the use of multispectral imaging, the new approach we propose in this paper aims to improve the estimation of the concentrations of the main skin chromophores (melanin, oxyhemoglobin and deoxyhemoglobin), while considering shading as a fully-fledged source. Methods: In this paper, we demonstrate that the use of the Infra-Red spectral band, in addition to the traditional RGB spectral bands of dermatological images, allows us to model the image provided by each spectral band as a mixture of the concentrations of the three chromophores in addition to that of the shading, which are estimated through four steps using Blind Source Separation. Results: We studied the performance of our new method on a database of real multispectral dermatological images of melanoma by proposing a new quantitative performances measurement criterion based on mutual information. We then validated these performances on a database of multispectral dermatological images that we simulated using our own new protocol. Conclusions: All the results obtained demonstrated the effectiveness of our new approach for estimating the concentrations of the skin chromophores from a multispectral dermatological image, compared to traditional approaches that consist of using only the RGB image by neglecting shading. [ABSTRACT FROM AUTHOR]

Complete or partial replacement of well-known five-membered chelating 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) ligands with analogous didentate 2,2′-biimidazole (H2biim) provides novel perspectives for exploiting the latter pH-tuneable bridging unit for connecting inert trivalent chromium with cationic partners. The most simple homoleptic complex [Cr(H2biim)3]3+ and its stepwise deprotonated analogues are only poorly soluble in most solvents and their characterization is limited to some solid-state structures, in which the pseudo-octahedral [CrN6] units are found to be intermolecularly connected via peripheral N–H⋯X hydrogen bonds. Moreover, the associated high-energy stretching N–H vibrations drastically quench the targeted near infrared (NIR) CrIII-based phosphorescence, which makes these homoleptic building blocks incompatible with the design of molecular-based luminescent assemblies. Restricting the number of bound 2,2′-biimidazole ligands to a single unit in the challenging heteroleptic [Cr(phen)2(Hxbiim)](1+x)+ (x = 2–0) complexes overcomes the latter limitations and allows (i) the synthesis and characterization of these [CrN6] chromophores in the solid state and in solution, (ii) the stepwise and controlled deprotonation of the bound 2,2′-biimidazole ligand and (iii) the implementation of Cr-centered phosphorescence with energies, lifetimes and quantum yields adapted for using the latter chromophores as sensitizers in promising 'complex-as-ligand' strategies. [ABSTRACT FROM AUTHOR]

Based on the same bis(4-piperidine) phenyl derivative donor, isophorone derivative bridge, and phenyl trifluoromethyl tricyclofuran (3F-TCF) acceptor, two different isolating groups, tert butyldimethylsilyl (TBDMS) and pentafluorophenyl ring (5F-Ph), were introduced into the donor and bridge to synthesize two chromophores XY 1-2. Eight 5F-Ph groups are respectively attached to the donor and bridge segments of the chromophore, which can prevent the molecules from tightly packing and thus improve polarization efficiency. This article systematically investigates the UV absorption, density functional theory (DFT) calculations, thermal stability, and electro-optic activity of these chromophores. The chromophores XY 1-2 exhibit good thermal stability at decomposition temperatures (Td) greater than 250 °C. Most importantly, rigid steric hindrance groups can effectively reduce dipole–dipole interactions between molecules and improve the conversion efficiency of the first-order hyperpolarization (β) of chromophores into large electro-optic (EO) coefficients (r33). And the poling efficiency of a single XY2 molecule at 1310 nm (0.69 ± 0.01 nm2 V−2/(1020 molecules per cm3)) is much higher than that of a single XY1 molecule when polarizing the polymer with chromophore XY 1-2. [ABSTRACT FROM AUTHOR]

A comprehensive investigation of two new molecular triads incorporating the diketopyrrolopyrrole unit into a quinoidized thienothiophene skeleton, which is further end‐capped with dicyanomethylene (DPP‐TT‐CN) or phenoxyl groups (DPP‐TT‐PhO), has been carried out. A combination of UV‐Vis‐NIR and infrared spectroelectrochemical techniques and cryogenic UV‐Vis‐NIR absorption spectroscopy supported by theoretical calculations has been used. The main result is the formation of similar H‐aggregates in the dimerization process of the neutral molecules and of the charged anionic species. The experimental absorption spectra of the aggregated species are accurately reproduced by quantum chemical calculations using the Spano's model, including excitonic coupling for the dimeric forms and full vibronic resolution of the absorption bands. The strong excitonic coupling taking place is key to understand the electronic structure of the dimeric species and has been instrumental to disentangle the type of H‐aggregation. This study is of relevance to get a better understanding of the molecular aggregation of organic π‐conjugated chromophores and is useful as a guideline for the refinement of the engineering of molecular materials for which supramolecular design is required. [ABSTRACT FROM AUTHOR]

In nature, molecular environments in proteins can sterically protect and stabilize reactive species such as organic radicals through non-covalent interactions. Here, we report a near-infrared fluorescent rotaxane in which the stabilization of a chemically labile squaraine fluorophore by the coordination of a tetralactam macrocycle can be controlled chemically and electrochemically. The rotaxane can be switched between two co-conformations in which the wheel either stabilizes or exposes the fluorophore. Coordination by the wheel affects the squaraine's stability across four redox states and renders the radical anion significantly more stable—by a factor of 6.7—than without protection by a mechanically bonded wheel. Furthermore, the fluorescence properties can be tuned by the redox reactions in a stepwise manner. Mechanically interlocked molecules provide an excellent scaffold to stabilize and selectively expose reactive species in a co-conformational switching process controlled by external stimuli. Incorporating sensitive chromophores into interlocked systems that are mechanically responsive to external stimuli is attractive for tuning of the dye's optical properties and stability. Here, the authors report the mechanically controlled protection and deprotection of a squaraine dye within a [2]rotaxane, governed by macrocycle shielding/de-shielding upon chloride addition or oxidation. [ABSTRACT FROM AUTHOR]

A smartphone-assisted electrochemiluminescence (ECL) strategy based on Ru(bpy)2(L)4+ as chromophores confined with metal − organic frameworks (Ru(bpy)2(L)4+@MOF-5) for the signal-amplified detection of miRNA-21 was developed. We synthesized a derivative of tris(2,2'-bipyridyl)ruthenium(II) complex (Ru(bpy)2(L)4+) with high charges, which can be loaded into the MOF-5 by strong electrostatic interaction to prevent from leakage. In addition, nucleic acid cycle amplification was used to quench the signal of Ru(bpy)2(L)4+@MOF-5 by ferrocene. This method was applied to detect the concentration of miRNA-21 ranging from 1.0 × 10−14-1.0 × 10−9 M with a low LOD of 7.2 fM. This work demonstrated the construction of a signal quenching strategy ECL biosensor for miRNA using Ru(bpy)2(L)4+@MOF-5 systems and its application in smartphone-assisted ECL detection. [ABSTRACT FROM AUTHOR]

This study investigated the applicability of fluorescent chromophores for exciton‐coupled circular dichroism (ECCD) exploiting fluorescence‐detected circular dichroism (FDCD). FDCD had been previously reported useful in allowing the sensitive detection of ECCD in favorable conditions. However, fluorescence detection may prevent applications of the combined method especially when solutions are polarized in emission. Even without polarization of emission, FDCD deviates from circular dichroism (CD) in some cases when the fluorophore of interest interacts with nonfluorescent chromophore. Herein, it was confirmed that employing 6‐methoxy‐2‐naphthoate always yielded interpretable exciton‐coupled FDCD spectra even when coupling with nonfluorescent p‐substituted benzoates. The 6‐methoxy‐2‐naphthoate chromophore (6‐MN) is prescribed in special cases when only a small amount of sample is available for determining the absolute stereochemistry by the CD exciton chirality method observed by FDCD. [ABSTRACT FROM AUTHOR]

Two regioisomeric extended tetrathiafulvalenes (TTFs) incorporating diindeno‐fused corannulene spacers were synthesized from suitable dione precursors using Horner‐Wadsworth‐Emmons olefination reactions. Both compounds are strong chromophores with a longest‐wavelength absorption that exhibited some degree of charge‐transfer character as inferred from solvatochromic behaviors and frontier orbital calculations. The compounds underwent two reversible one‐electron oxidations and a quasi‐reversible third oxidation during cyclic voltammetry conditions. The mono‐ and dications had characteristic NIR absorptions and both were EPR active. The dications with potential diradicaloid characters underwent reactions when generated in bulk. [ABSTRACT FROM AUTHOR]

Incorporating photoactive linkers into metal–organic frameworks (MOFs) has proved useful in improving photophysical properties of organic chromophores. This is achieved by controlling the local packing of linkers or defect engineering within the MOF. Using these ideas, we demonstrate that a tetraphenylethylene-based MOF exhibits long-lived linker-based emission out to 1 μs—substantially longer than previously reported. The emission contains two independent components whose dynamics branch from early timescales. These findings suggest that charge recombination and distinct defect sites exist and contribute a weak yet detectable emission, and demonstrate how high-sensitivity transient photoluminescence spectroscopy can reveal unexpected populations in nominally crystalline materials. [ABSTRACT FROM AUTHOR]

A novel series of homoconjugated oligomers of azapentacene, linked via the rigid connecting unit bicyclo[2.2.2]octane bridge is presented. The investigation delves into intramolecular singlet fission (iSF) within these dimeric and trimeric frameworks, employing various time‐resolved spectroscopies and quantum chemical calculations. Combining the merits of both through‐space and through‐bond couplings between the constituent chromophores within these rigid homoconjugated structures, iSF proceeds within a few picoseconds, exhibiting a 2–3 orders of magnitude acceleration compared to traditional covalently linked oligomers and achieving an iSF efficiency approaching unity. In the homoconjugated trimer, the larger interplanar angle between neighboring chromophores leads to a relatively slower iSF rate compared to that of the homoconjugated dimer. Furthermore, the active involvement of the charge transfer state is demonstrated to accelerate the iSF process in the trimer, while exerting no influence on the iSF process in the dimer. The study provides novel avenues for investigating the influence of molecular geometry on singlet fission and reveals the crucial role of the interplay between spatial and covalent coupling in facilitating intramolecular singlet fission. [ABSTRACT FROM AUTHOR]

A set of ferrocenyl-functionalized perylenediimide (PDI) compounds and their 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) derivatives 1–5 were designed and synthesized using palladium-catalyzed Sonogashira cross-coupling, followed by a thermally activated [2 + 2] cycloaddition–retroelectrocyclization [CA–RE] reaction with a 1,1,2,2-tetracyanoethylene (TCNE) acceptor in good yields. The TCBD group works as an acceptor, whereas the ferrocenyl group acts as a donor at the central PDI core. The effects of varying the number of ferrocenyl and TCNE groups on the photophysical, thermal, electrochemical, and spectroelectrochemical properties were studied. The di-substituted PDI derivatives 3, 4, and 5 exhibit bathochromic shifts in the absorption spectra compared to 1 and 2, attributed to the extended π-conjugation. The electrochemical analysis of derivatives 2, 4, and 5 shows multiple reduction waves in the low potential region due to the presence of TCBD and perylenediimide acceptor units. Spectroelectrochemical studies were performed, showing that upon applying redox potentials, the absorption spectra shifted from the visible to the near-infrared (NIR) region. Computational calculations indicate that in the HOMO, the electron density is localized on the ferrocene unit, while in the LUMO, it is distributed over the PDI–TCBD unit, indicating a strong D–A interaction. [ABSTRACT FROM AUTHOR]

Single luminophore enabling stimuli‐responsive dual‐emission characteristic has received considerable interest in recent years due to its special advantages in advanced optical events. A large number of reports around the globe have involved the dynamic or adjustable dual‐emission phenomenon (e.g., the dual emission intensity or ratio) in single‐emitter based systems. However, a systematic overview summarizing the underlying mechanisms, stimuli‐responsive behaviors, and applications of this topic is, so far, missing. To further promote the development and extend the important role of such a kind of materials in diverse communities, in this review, the latest advancements in the field of single‐luminophore based materials that exhibit stimuli‐responsive dual‐emission characteristics are summarized. The discussion is centered on the underlying the photophysical mechanisms, the innovative design approaches, strategies for modulating the dual emission properties, and the advanced applications of these single‐luminophore based systems. This review is anticipated to provide new insights into the distinctive field of the organic luminescence community from a materials perspective. [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]

This review contains data on a wide class of microporous materials with frameworks belonging to the sodalite topological type. Various methods for the synthesis of these materials, their structural and crystal chemical features, as well as physical and chemical properties are discussed. Specific properties of sodalite-related materials make it possible to consider they as thermally stable ionic conductors, catalysts and catalyst carriers, sorbents, ion exchangers for water purification, matrices for the immobilization of radionuclides and heavy metals, hydrogen and methane storage, and stabilization of chromophores and phosphors. It has been shown that the diversity of properties of sodalite-type materials is associated with the chemical diversity of their frameworks and extra-framework components, as well as with the high elasticity of the framework. [ABSTRACT FROM AUTHOR]

[Display omitted] In this paper, we present a facile method of synthesis and modification of poly(glycidyl methacrylate) brushes with 6-aminofluorescein (6AF) molecules. Polymer brushes were obtained using surface-grafted atom transfer radical polymerization (SI-ATRP) and functionalized in the presence of triethylamine (TEA) acting both as a reaction catalyst and an agent preventing aggregation of chromophores. Atomic force microscopy (AFM), FTIR, X-ray photoelectron spectroscopy (XPS) were used to study the structure and formation of obtained photoactive platforms. UV-Vis absorption and emission spectroscopy and confocal microscopy were conducted to investigate photoactivity of chromophores within the macromolecular matrix. Owing to the simplicity of fabrication and good ordering of the chromophore in a thin nanometric layer, the proposed method may open new opportunities for obtaining light sensors, photovoltaic devices, or other light-harvesting systems. [ABSTRACT FROM AUTHOR]

Beer is a popular beverage consumed globally, and studies have emphasized the benefits of moderate consumption as well as its sensory effects on consumers. Color is a crucial sensory attribute, being the first aspect a consumer notices when assessing a beer's quality. This review seeks to offer detailed insights into how brewing methods, raw materials, and the chemical diversity of beer influence the production of beer color. The chemical mechanisms responsible for color development and how consumers and color systems perceive the color of beer were assessed. A systematic review following the PRISMA methodology, coupled with a bibliometric analysis, was performed using (Rayyan 2022) and (VOSviewer 1.6.20) software to assess and evaluate the scientific research retrieved from the Web of Science Core Collection. The findings highlight the significant roles of malt types, heat brewing processes, control of chemical parameters, and innovative brewing techniques in conventional beer color production. Novel chromophores like perlolyrine, pyrrolothiazolate, and furpenthiazinate are thought to affect Pilsen-style beers, along with melanoidins, Strecker aldehydes, and 5-hydroxymethylfurfural (HMF) in conventional beers. In craft beers, such as fruit- or herb-based beers, flavonoids like anthocyanins, along with other natural pigments and synthetic colorants, are identified as the primary sources of color. However, studies related to the influence of chromophores like perlolyrine, pyrrolothiazolate, and furpenthiazinate on beer color are scarce, and emerging additives, such as pigments from microorganisms, spices, exotic herbs, and leaves of plants, on craft beer offer insights for future research. [ABSTRACT FROM AUTHOR]

The European Food Safety Authority (EFSA) has approved the use of a 1045 J/L UV-C dose as an adjunct to pasteurization to increase the shelf life and vitamin D3 content of milk. However, there are no verification methods analogous to the alkaline phosphatase test for pasteurized milk to ensure that the desired UV-C dose has been correctly applied. The aim is to develop a real-time in-line detector based on fluorescence spectroscopy. In this study, 22 different UV-C doses (ranging from 0 to 2000 J/L) were applied to milk to assess the impact of photooxidation on intrinsic photosensitive chromophores. Fluorescence spectroscopy (90°-angle) was employed as the method of analysis for monitoring the changes in the fluorescence spectra of chromophores in milk without sample pretreatment. Three important chromophore areas (CAs) were identified: CA 1 (riboflavin), CA 3 (vitamin A and dityrosine) and CA 4 (tryptophan), with statistically significant changes at around 1045 J/L and 1500 J/L. The findings of our preliminary study support our hypothesis that the fluorescence of intrinsic chromophores can be used as verification of the applied UV-C dose. [ABSTRACT FROM AUTHOR]

Molecular assemblies featuring two-dimensionality have attracted increasing attention, whereas such structures are difficult to construct simply relying on spontaneous molecular assembly. Here, we present two-dimensional assemblies of acene chromophores achieved using a tripodal triptycene supramolecular scaffold, which have been shown to exhibit a strong ability to assemble molecular and polymer motifs two-dimensionally. We designed pentacene and anthracene derivatives sandwiched by two triptycene units. These compounds assemble into expected two-dimensional structures, with the pentacene chromophores having both sufficient overlap to cause singlet fission and space for conformational change to facilitate the dissociation of a triplet pair into free triplets, which is not the case for the anthracene analog. Detailed spectroscopic analysis revealed that the pentacene chromophore in the assembly undergoes singlet fission with a quantum yield of 88 ± 5%, giving rise to triplet pairs, from which free triplets are efficiently generated (FT = 130 ± 8.8%). This demonstrates the utility of the triptycene-based scaffold to design functional p-electronic molecular assemblies. [ABSTRACT FROM AUTHOR]

ABSTRACT Para‐phenylene‐bridged pyridinium (acceptor)–dicyanomethanide (donor)‐based zwitterions were computationally investigated and are reported here. Reichardt's metamer was found to be twisted and Brooker's metamer in near‐planar conformation. Natural bond orbital (NBO) analysis showed that mesomeric resonance is helping Brooker's metamer but found to be not helpful for Reichardt's metamer. To assess the impacts of metamerism and aromatic bridges, fundamental molecular properties like dipole moments (μ), polarizabilities (α), hyperpolarizabilities (β), and adiabatic absorptions of these two molecules were analyzed and then directly compared with their counterpart zwitterions without any bridges (previously reported). Results of impact of metamerism: Reichardt's metamer showed around three times enhanced hyperpolarizabilities (ωB97xD: β = 1577.1 × 10−30 esu) than the Brooker's metamer (ωB97xD: β = 532.5 × 10−30 esu). Impacts of p‐phenylene bridges: Compared to their respective D–A directly connected zwitterions reported previously (in ωB97xD methodology, Reichardt's: β = 257.2 × 10−30 esu and Brooker's: β = 67.2 × 10−30 esu), respective p‐phenylene‐bridged zwitterions showed five to eight times enhanced hyperpolarizabilities. This report highlights the better efficiencies of Reichardt's metamer over Brooker's metamer and aromatically bridged over the directly connected zwitterions. Current findings may be helpful in the designing of efficient functional molecular chromophores, and aromatic bridge combined with zwitterions can be solutions to nonlinear transparency trade‐off problem. [ABSTRACT FROM AUTHOR]

New Y-shaped ferrocene (Fc)-conjugated trifluoromethyl-substituted imidazole (IM) donor–π–acceptor [(D–π)2–IM–D′–π–CF3] "push–pull" chromophores [(Fc–CH＝CH)2–IM–C6H4–R–C6H4–CF3] {R= –OCH3 (1); –N(C2H5)2 (2)} were synthesized and structurally characterized. The structure of the chromophores was confirmed via single-crystal X-ray diffraction studies. They crystallized in the triclinic P1¯ (for 1) and monoclinic P21/c (for 2) space groups. Thermogravimetric analysis (TGA) was used to study the thermal stability of chromophores 1 and 2, and it was found that both were stable at temperatures of about 300 °C. The redox properties were studied through cyclic voltammetry (CV), which revealed one-electron transfer from the ferrocene to ferrocenium ion (Fe2+ Fe3+), and their potentials were utilized to calculate their energy gaps, which were 2.16 eV for 1 and 2.12 eV for 2. The second-order nonlinear optical (NLO) properties of chromophores 1 and 2 were explored via electric-field-induced second-harmonic generation (EFISH) technique in CHCl3 solution with an incident wavelength of 1907 nm. μβEFISH values were −725 × 10−48 esu and −806 × 10−48 esu for 1 and 2, respectively. The μβEFISH values slightly decreased compared with other reported ferrocene-conjugated Y-shaped imidazole chromophores owing to their substitution on imidazole nitrogen, which increases steric hindrance and reduces the ICT process in the chromophores. In addition, their frontier molecular orbital levels, excited and ground state dipole moments (μe and μg), and electronic absorption spectra were studied using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) with the B3LYP method using the 6-31+G** basis set. [ABSTRACT FROM AUTHOR]

The investigation of impact of through‐space/through‐bond electronic interaction among chromophores on photoexcited‐state properties has immense potential owing to the distinct emergent photophysical pathways. Herein, the photoexcited‐state dynamics of homo‐sorted π‐stacked aggregates of a naphthalenemonoimide and perylene‐based acceptor‐donor (NI‐Pe) system and a fork‐shaped acceptor‐bisdonor (NI‐Pe2) system possessing integrally stacked peri‐substituted donors was examined. Femtosecond transient absorption (fsTA) spectra of NI‐Pe monomer recorded in chloroform displayed spectroscopic signatures of the singlet state of Pe; 1Pe*, the charge‐separated state; NI−⋅‐Pe+⋅, and the triplet state of Pe; 3Pe*. The examination of ultrafast excited‐state processes of NI‐Pe aggregate in chloroform revealed faster charge recombination (τCRa ${{\tau }_{CR}^{a}}$ =1.75 ns) than the corresponding monomer (τCRm ${{\tau }_{CR}^{m}}$ =2.46 ns) which was followed by observation of a broad structureless band attributed to an excimer‐like state. The fork‐shaped NI‐Pe2 displayed characteristic spectroscopic features of the NI radical anion (λmax~450 nm) and perylene dimer radical cation (λmax~520 nm) upon photoexcitation in non‐polar toluene solvent in the nanosecond transient absorption (nsTA) spectroscopy. The investigation highlights the significance of intrinsic close‐stacked arrangement of donors in ensuring a long‐lived photoinduced charge‐separated state (τCR ${{\tau }_{CR}}$ =1.35 μs) in non‐polar solvents via delocalization of radical cation between the donors. [ABSTRACT FROM AUTHOR]

Tricolor electrochromism was realized through the interconversion among the neutral (yellow), dicationic (green), and tetracationic (blue) states, even though only one kind of chromophore is generated upon oxidation. Both dicationic and tetracationic states were isolated as stable salts, and their different colors come from the effective inter‐chromophore interaction only in the tetracationic state but not in the dicationic state. Despite the negligible Coulombic repulsion in the tetracationic state with four cyanine‐type chromophores, pentacenebisquinodimethane undergoes stepwise two‐stage two‐electron oxidation when radical‐stabilizing 5‐(4‐octyloxyphenyl)‐2‐thienyl groups are attached on the exomethylene bonds. A contribution from the biradical form only in the neutral state but not in the dicationic state is the reason for the observed negative cooperativity during the electrochemical oxidation. [ABSTRACT FROM AUTHOR]

Pyrylium salts based on a cationic oxygen heterocycle are a key class of chromophores. However, synthesis of these salts generally requires use of harsh acids, copious organic solvents, and in many cases, hazardous conditions. This work provides a two-pot synthesis for substituted triphenyl pyrylium salts wherein chalcone intermediates are first prepared and then mild methanesulfonic acid is used in combination with a dehydrating agent to drive pyrylium cyclization. Purification is achieved through a simple, aqueous workup involving counterion metathesis which avoids the need for environmentally unfriendly organic solvents. This mild, green approach has been applied to synthesize a collection of known pyryliums as well as a new family of red-shifted pyrylium chromophores bearing p -pyrrolidinylphenyl substituents. The synthesis of the latter group demonstrates that unlike other current methods, our approach offers enhanced functional group tolerance as well as finer control over substituent placement. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to systematically demonstrate a methodology to determine the relative and absolute encapsulation efficiencies (αRe and αAb) for thermally- and chemically-robust inorganic pigments, typically like ZrSiO4-based pigments, thereby enhancing their coloring performance. Design/methodology/approach: The authors designed a route, surplus alkali-decomposition and subsequently strong-acid dissolution (SAD2) to completely decompose three classic zircon pigments (Pr–ZrSiO4, Fe2O3@ZrSiO4 and CdS@ZrSiO4) into clear solutions and preferably used inductively coupled plasma-optical emission spectrometry (ICP-OES) to determine the concentrations of host elements and chromophores, thereby deriving the numeric data and interrelation of αRe and αAb. Findings: Zircon pigments can be thoroughly decomposed into some dissoluble zirconate–silicate resultants by SAD2 at a ratio of the fluxing agent to pigment over 6. ICP-OES is proved more suitable than some other quantification techniques in deriving the compositional concentrations, thereby the values of αRe and αAb, and their transformation coefficient KRA, which maintains stably within 0.8–0.9 in Fe2O3@ZrSiO4 and CdS@ZrSiO4 and is slightly reduced to 0.67–0.85 in Pr–ZrSiO4. Practical implications: The SAD2 method and encapsulation efficiencies are well applicable for both zircon pigments and the other pigmental or non-pigmental inhomogeneous systems in characterizing their accurate composition. Originality/value: The authors herein first proposed strict definitions for the relative and absolute encapsulation efficiencies for inorganic pigments, developed a relatively stringent methodology to determine their accurate values and interrelation. [ABSTRACT FROM AUTHOR]

Development of organic nonlinear optical materials has become progressively more important due to their emerging applications in new‐generation photonic devices. A novel series of chromophores based on innovative thiophene and furan‐fused cyclopentadienyl bridge with various powerful donor and acceptor moieties were designed and theoretically investigated for applications in nonlinear optics. To unravel the structure–property relationship between this new push‐pull conjugated systems and their nonlinear optical property, multiple methods, including density of states analysis, coupled perturbed Kohn–Sham (CPKS) method, sum‐over‐states (SOS) model, the two‐level model (TSM), hyperpolarizability density analysis, and the (hyper)polarizability contribution decomposition, were performed to comprehensively investigated the nonlinear optical and electronic properties of this new π‐system. Due to excellent charge transfer ability of new bridge and distinctive structure of donor and acceptor, the designed chromophores exhibit deep HOMO levels, low excitation energy, high dipole moment difference and large hyperpolarizability, indicating the appealing air‐stable property and remarkable electrooptic performance of them. Importantly, THQ‐CS‐A3 and PA‐CS‐A3 shows outstanding NLO response properties with βtot value of 6953.9 × 10−30 and 5066.0 × 10−30 esu in AN, respectively. The influence of the push‐pull strength, the heterocycle and the π‐conjugation of new bridge on the nonlinear optical properties of this novel powerful systems are clarified. This new series of chromophores exhibit remarkable electro‐optical Pockels and optical rectification effect. More interestingly, PA‐CS‐A3 and THQ‐CS‐A2 also show appealing SHG effect. This study will help people understand the nature of nonlinear optical properties of innovative heteroarene‐fused based cyclopentadienyl chromophores and offer guidance for the rational design of chromophores with outstanding electrooptic (EO) performance in the future. [ABSTRACT FROM AUTHOR]

Due to their strong molecular hyperpolarizability, organic push–pull materials are gaining interest for nonlinear optical applications. We were able to characterize the intramolecular charge transfer and the distribution of the electron cloud within the molecular unit by exciting these materials under the influence of an electric field. The series products of conjugated monomers derived from acrylo–azobenzene containing in the para position the attracting groups (–H, –NO2, –COOC2H5, –SO3H and –COOH) exhibit good nonlinear optical activity. We computed the nonlinear optical characteristics of these compounds as well as exploiting the theoretical calculations of DFT and AM1 to determine their hyperpolarizabilities. Besides, we investigated the increase in hyperpolarizability in the push–pull model of organic compounds under the effect of the strength of attracting groups, the existence of the conjugated π -electron and the azo bridge. [ABSTRACT FROM AUTHOR]

We have conducted time-resolved experiments (pump–probe and pump–repump–probe) on a model aromatic chromophore, aniline, after excitation in water at 267 nm. In the initial spectra recorded, in addition to the absorption corresponding to the bright ππ* excitation, the fingerprint of a transient state with the electron located on the solvent molecule is identified. We postulate that the latter corresponds to the πσ* state along the N–H bond, whose complete relaxation with a ∼500 ps lifetime results in the formation of the fully solvated electron and cation. This ionization process occurs in parallel with the ππ* photophysical channel that yields the characteristic ∼1 ns fluorescence lifetime. The observed branched pathway is rationalized in terms of the different H-bonds that the water establishes with the amino group. The proposed mechanism could be common for aromatics in water containing N–H or O–H bonds and would allow the formation of separated charges after excitation at the threshold of their electronic absorptions. [ABSTRACT FROM AUTHOR]

Computationally inspired design of organic electronic materials requires robust models of not only the ground and excited electronic states but also of transitions between these states. In this work, we introduce a strategy for obtaining electronic transition dipole moments for the lowest-lying singlet–singlet transition in organic chromophores from time-independent excited-state density-functional tight-binding (ΔDFTB) calculations. Through small-molecule benchmarks and applications to larger chromophores, we explore the accuracy, potential, and limitations of this semiempirical strategy. While more accurate methods are recommended for small systems, we find some evidence for the method's potential in high-throughput molecular screening applications and in the analysis of molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

A simple DABCO-catalyzed domino reaction between tosyliminoindoles and arylidene malononitriles using NaHCO3 as a cheap, non-toxic cooperative base is reported. The transition-metal- and oxidant-free one-pot π-extension reaction creates two new C–C and C＝N bonds that deliver good to high yields of a series of blue-fluorescent 2-amino-α-carboline derivatives with good thermal stability. In addition, the solvatochromic studies indicate that the emission peaks and Stokes shift values are slightly higher in the case of polar solvents. Moreover, all the tested α-carbolines emitted blue light in the 413–471 nm range and showed moderate to good quantum yields (Øf ≤ 0.74) with typical Stokes shift values (Δ ≤ 6469 cm−1). Notably, electrochemical studies confirm that the prepared chromophores exhibit reversible oxidation potential waves and quasi-reversible waves. [ABSTRACT FROM AUTHOR]

Ultralong organic phosphorescence (UOP) is essential for potential applications in bioelectronics and optoelectronics. However, the precise design of UOP materials remains a formidable challenge. Herein, a facile strategy is presented to confine dimeric chromophores for triggering UOP emission, based on the manipulation of the carbonyl, sulfonyl, and amino groups within organic phosphors. The experimental data reveal that saccharin analogs in crystals containing dimeric chromophores, confined by the (3D) hydrogen‐bonded networks, exhibit ultralong emission lifetime of up to 635 ms under ambient conditions. Whereas for saccharin analogue crystals lacking dimeric chromophores, the lifetime decreases to 54 ms, resulting in the absence of UOP emission. Moreover, the non‐toxic saccharin crystals with UOP have succeeded in drug anti‐counterfeiting. These findings will open a novel avenue for the design UOP materials and broaden the domain of UOP to diverse applications. [ABSTRACT FROM AUTHOR]

Ultralong room‐temperature phosphorescent (URTP) materials have attracted wide attention in anti‐counterfeiting, optoelectronic display, and bio‐imaging due to their special optical properties. However, room‐temperature blue phosphorescent materials are very scarce during applications because of the need to simultaneously populate and stabilize high‐energy excited states. In this work, a stepwise stiffening chromophore strategy is proposed to suppress non‐radiative jump by continuously reducing the internal spin of the chromophore, and successfully developing a series of blue phosphorescent materials. Phosphorescence lifetimes of more than 3 s are achieved, with the longest lifetime reaching 5.44 s and lasting more than 70 s in the naked eye. As far as is know, this is the best result that has been reported. By adjusting the chromophore conjugation, multicolor phosphorescences from cyan to green have been realized. In addition, these chromophores exhibit the same excellent optical properties in urea and polyvinyl alcohmance (PVA). Finally, these materials are successfully applied to luminescent displays. [ABSTRACT FROM AUTHOR]

Chromophores undergoing excited‐state intramolecular proton transfer (ESIPT) feature a distinct four‐level photocycle and significant Stokes shift, which make them ideal for achieving population inversion upon photoexcitation, a fundamental prerequisite for lasing, by mitigating the concerns of self‐absorption owing to spectral overlap. This study focuses on functionalizing the hydroxyphenyl‐benzothiazole (HBT) ESIPT laser dye through the introduction of fluorene and phenyl‐carbazole moieties at the para‐position to the hydroxyl group, to demonstrate amplified spontaneous emission (ASE) activities. The synthesized HBT derivatives not only exhibit high thermal and photostability, but also high photoluminescence quantum yields, exceeding 40%, which is noteworthy for ESIPT materials emitting in the yellow–orange to red color ranges. Computational analyses show that these new HBT materials possess substantially lower ESIPT energy barriers, compared to their parent HBT, facilitating their efficient ESIPT processes. Moreover, these derivatives demonstrate a high radiative rate of 1.47 × 108 s−1. Thin films of a fluorene‐substituted HBT (HBT‐pFl) show a low solid‐state amplified spontaneous emission threshold value of 3.8 µJ cm−2 at 582 nm, representing the lowest reported solid‐state ASE threshold for laser dyes in the orange emission region (575–600 nm) to date. [ABSTRACT FROM AUTHOR]

Channelrhodopsins are popular optogenetic tools in neuroscience, but remain poorly understood mechanistically. Here we report the cryo-EM structures of channelrhodopsin-2 (ChR2) from Chlamydomonas reinhardtii and H. catenoides kalium channelrhodopsin (KCR1). We show that ChR2 recruits an endogenous N-retinylidene-PE-like molecule to a previously unidentified lateral retinal binding pocket, exhibiting a reduced light response in HEK293 cells. In contrast, H. catenoides kalium channelrhodopsin (KCR1) binds an endogenous retinal in its canonical retinal binding pocket under identical condition. However, exogenous ATR reduces the photocurrent magnitude of wild type KCR1 and also inhibits its leaky mutant C110T. Our results uncover diverse retinal chromophores with distinct binding patterns for channelrhodopsins in mammalian cells, which may further inspire next generation optogenetics for complex tasks such as cell fate control. It is known that channelrhodopsins use all-trans retinal as chromophore for light activation. Here, the authors find that different channelrhodopsins utilize various forms of retinal in mammalian cells, which could inspire next-generation optogenetic tools. [ABSTRACT FROM AUTHOR]

The presented work concerns computational investigations of the physical properties of composite materials based on polymer matrix and nonlinear optical (NLO) active chromophores. The structural, electronic, and optical properties of selected tetrathiafulvalene (TTF)-based chromophores have been calculated using quantum chemical methods. The polymer matrix changes the physical properties of the inserted chromophores influencing their optical parameters. To explain the mechanism of the NLO signal occurrence from the composites based on poly(methyl methacrylate) (PMMA) matrix and TTF chromophores, their structures are modeled using the classical molecular dynamics. In consequence, the structural properties of the composites are discussed according to the NLO requirements. By developing the theoretical model based on a discrete multipole local field approach, the impact of polymer matrix on the optical properties of chromophores is explained. [ABSTRACT FROM AUTHOR]

Sterically distorted donor‐acceptor π‐systems, termed DA springs, can be progressively planarized under mechanical load causing a bathochromic shift of the photoluminescence (PL) spectrum. By combining theory and experiment, we here use a simple linear force calibration for two different conformational mechanochromophores to determine molecular forces in polymers from the mechanochromic shift in PL wavelength during multiple uniaxial tensile tests. Two systems are used, i) a highly entangled linear glassy polyphenylene and ii) a covalent elastomeric polydimethylsiloxane network. The mean forces estimated by this method are validated using known threshold forces for the mechanochemical ring‐opening reactions of two different spiropyran force probes. The agreement between both approaches underlines that these DA springs provide the unique opportunity for the online monitoring of local molecular forces present in diverse polymer matrices. [ABSTRACT FROM AUTHOR]

The wavelength‐by‐wavelength resolved photoreactivity of two photo‐caged carboxylic acids, i. e. 7‐(diethylamino)‐coumarin‐ and 3‐perylene‐modified substrates, is investigated via photochemical action plots. The observed wavelength‐dependent reactivity of the chromophores is contrasted with their absorption profile. The photochemical action plots reveal a remarkable mismatch between the maximum reactivity and the absorbance. Through the action plot data, the study is able to uncover photochemical reactivity maxima at longer and shorter wavelengths, where the molar absorptivity of the chromophores is strongly reduced. Finally, the laser experiments are translated to light emitting diode (LED) irradiation and show efficient visible‐light‐induced release in a near fully wavelength‐orthogonal, sequence‐independent fashion (λLED1 = 405 nm, λLED2 = 505 nm) with both chromophores in the same reaction solution. The herein pioneered wavelength orthogonal release systems open an avenue for releasing two different molecular cargos with visible light in a fully orthogonal fashion. [ABSTRACT FROM AUTHOR]

Multicolor tuning of persistent luminescence has been extensively studied by deliberately integrating various luminescent units, known as activators or chromophores, into certain host compounds. However, it remains a formidable challenge to fine-tune the persistent luminescence spectra either in organic materials, such as small molecules, polymers, metal-organic complexes and carbon dots, or in doped inorganic crystals. Herein, we present a strategy to delicately control the persistent luminescence wavelength by engineering sub-bandgap donor-acceptor states in a series of single-phase Ca(Sr)ZnOS crystals. The persistent luminescence emission peak can be quasi-linearly tuned across a broad wavelength range (500–630 nm) as a function of Sr/Ca ratio, achieving a precision down to ~5 nm. Theoretical calculations reveal that the persistent luminescence wavelength fine-tuning stems from constantly lowered donor levels accompanying the modified band structure by Sr alloying. Besides, our experimental results show that these crystals exhibit a high initial luminance of 5.36 cd m−2 at 5 sec after charging and a maximum persistent luminescence duration of 6 h. The superior, color-tunable persistent luminescence enables a rapid, programable patterning technique for high-throughput optical encryption. Persistent luminescence is typically confined to discrete wavelengths. Here, the authors can fine tune emission color from green to orange through blending isostructural compounds in single-phase Ca(Sr)ZnOS crystals. [ABSTRACT FROM AUTHOR]

A strategic approach to develop efficient ultra‐broadband terahertz (THz) crystals involves the incorporation of different electron donating groups (EDGs) into cationic chromophores. In contrast to the widely utilized non‐cyclic 4‐(dimethylamino)phenyl (DA) EDG, cyclic 5‐membered 4‐(2‐(hydroxymethyl)pyrrolidine‐1‐yl)phenyl (PB) and cyclic 6‐membered 4‐(3‐(hydroxymethyl)piperidin‐1‐yl)phenyl (PN) EDGs exhibit an asymmetrical shape with a strongly interacting hydroxymethyl group at the chiral center. Notably, the PB EDG shows narrower intrinsic vibrational states with lower conformational flexibility and smaller ring flips compared to the PN EDG. In the crystalline state, introducing the PB EDG leads to the formation of a new class of nonlinear optical assembly, the so‐called stair‐type cation‐anion assembly. This assembly demonstrates optimal chromophore alignment with state‐of‐the‐art effective first hyperpolarizability (209 × 10−30 esu). Furthermore, the PB EDG‐based crystals exhibit significantly lower THz absorption compared to previously reported benchmark crystals. In THz wave generation experiments, PB EDG‐based crystals demonstrate state‐of‐the‐art efficiency and ultrabroad spectral bandwidth, featuring a cut‐off frequency of up to 16 THz. [ABSTRACT FROM AUTHOR]

Context: This work reports structure–property correlations of 27 zwitterions Reichardt's types of zwitterions. Focuses are twofold, to see the (1) impacts of metamerism with Reichardt's vs Brooker's types of zwitterions and (2) impacts of monocyclic aromatic rings as bridges. All the molecules considered here have pyridinium (common acceptor: A) and p-phenylene-dicyanomethanide (common donor: D). Fundamental molecular properties like dipole moments (μ), polarizabilities (α), hyperpolarizabilities (β), and adiabatic absorptions were computed only for the Reichardt types and compared with the literature reported respective Brooker's types of zwitterions. As an impact of metamerism, in general 2–3 times enhanced hyperpolarizabilities (β) were observed for Reichardt's compared to Brooker's types. Exceptions were observed with some triazine bridges and furan bridge, where Brooker's types were found to be more efficient. As impacts of aromatic bridges, in general, 6–sevenfold enhanced β compared to well-known traditional bridges and enhanced β were observed compared to D-A directly connected zwitterion (benzene bridge: sixfold enhanced β). Current findings show that the aromatic bridge control with Reichardt's types of zwitterions is more efficient and thus may be employed as an effective strategy for the designing of functional molecular chromophores for various other fundamental areas. Methods: All computations were performed with Gaussian 09. Geometry optimizations and computations of fundamental properties were carried out with HF, B3LYP, CAM-B3LYP, and ωB97xD methodologies, with 6-31G(d,p) and aug-cc-pVDZ basis sets. For adiabatic excitations, computations were carried out using TDDFT and TDHF approaches. For the computations of the response properties (like the nonlinear optical responses), CPHF approach was used. [ABSTRACT FROM AUTHOR]

Rhodopsin is a seven-helical transmembrane protein with a retinal chromophore covalently bound to a conserved lysine in helix G via a retinal protonated Schiff base (RPSB). Microbial rhodopsins absorb light through chromophore and play a fundamental role in optogenetics. Numerous microbial rhodopsins have been discovered, contributing to diverse functions and colors. Solid-state NMR spectroscopy has been instrumental in elucidating the conformation of chromophores and the three-dimensional structure of microbial rhodopsins. This review focuses on the 15N chemical shift values of RPSB and summarizes recent progress in the field. We displayed the correlation between the 15N isotropic chemical shift values of RPSB and the maximum absorption wavelength of rhodopsin using solid-state NMR spectroscopy. [ABSTRACT FROM AUTHOR]

Previously synthesized six selected Pyridinium‐Benzimidazolate based zwitterions were investigated in this contribution. Of the selected molecules, two are TICT, two are PICT (twisted and planar intramolecular charge transfer types respectively), and the other two are PICT+TICT types. Generally, TICT vs PICT is the most widely used strategy for chromophore design by earlier researchers. In this work, impacts of PICT+TICT effects (two effects combined in one chromophore), through p‐phenylene bridges, on various fundamental properties like, dipole moments, polarizabilities, hyperpolarizabilities, adiabatic excitations were analyzed. Nonlinear optical (NLO) responses of the six molecules indicate that PICT more efficient than TICT (6‐11‐times enhanced β), and PICT+TICT more efficient than both PICT (~4 times enhanced β) and TICT (20–40 times enhanced β). Current work also shows the role of aromatic p‐phenylene bridge as an efficient communicator between the donor and acceptor, in enhancing the NLO and other response properties. This work suggests that inducing bridge aromatic control to a TICT chromophore (making it to exhibit an amalgamation of PICT and TICT effects) is an effective and efficient strategy in the designing of molecular nonlinear optical chromophores, over either PICT or TICT only. [ABSTRACT FROM AUTHOR]