Design Strategy of Infrared 4-Hydroxybenzylidene-imidazolinone-Type Chromophores based on Intramolecular Charge Transfer:a Theoretical Perspective

Partial genetically encoded 4-hy-droxybenzylidene-imidazolinone(HBI)-type chromophores are new promising fluorescent probes,which are suitable for imaging and detection of living cells.How-ever,the lack of infrared chro-mophores hinders the develop-ment seriously.Here more than 30 HBI-type chromophores with reg-ular 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-accept-ing-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 pre-dicted.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 reg-ularities and redshift mechanisms of HBI-type chromophores and provides valuable design strategy for infrared chromophores synthesis in experiment.

Spectroscopic Properties and Three-photon Absorption Induced Optical Limiting of Series of Novel Nonlinear Chromophores

Three novel nonlinear chromophores with symmetric D-π-D molecular structure and extended conjugated length were synthesized. Solvatochromism analysis shows great symmetric intramolecular charge transfer occurring in chromophores by the enhancement in the dipole moment between the ground and excited states. The properties of optical power limiting induced by three-photon absorption （3PA） are demonstrated. Large 3PA coefficients and the corresponding molecular cross sections as high as 10^-74 cm^6s^2 were obtained for nanosecond laser pulses at 1.06μm from nonlinear transmission measurements.

Synthesis and Nonlinear Optical Property of a Series of New Chromophores Containing Furan Ring as the Only Conjugation Bridge

This paper reports the synthesis and the nonlinear optical property of a series of new chromophores which contain furan ring as the only conjugation bridge for the first time. They are characterized by UV-VIS, FT-IR, H-1 NMR, MS and elemental analysis. Their dipole moment and the first-order molecular hyperpolarizability (beta) are calculated and compared with those or the analogues containing either benzene or thiophene as file conjugation bridge.

Mechanistic Insights into the Photophysics of Ortho-hydroxyl GFP Core Chromophores

Herein we have employed the MS-CASPT2//CASSCF method to study the S1 excited-state intramolecular proton transfers （ESIPTs） of recently synthesized ortho-hydroxyl GFP core chromophores, i.e. OHIM, CHBDI, and MHBID, and their excited-state relaxation pathways. We have found that in OHIM and CHBDI, the ESIPT process is associated with small barriers of 3.4 and 4.2 kcal/mol; while, in MHBDI, it becomes essentially barrierless. Moreover, we have found two main S1 excited-state radiationless channels. In the first one, the enol S1 species decays to the So state via the enol S1/S0 conical intersection after overcoming considerable barriers of 7.0 and 7.7 kcal/mol in OHIM and CHBDI （however, in MHBDI, it is nearly barrierless）. In the second one, the keto S] species is first generated through the ESIPT event; then, it is de-excited into the So state in the vicinity of the keto S1/S0 conical intersection. These energetically allowed excited-state decay channels rationalize ex- perimentally observed ultralow fluorescence quantum yields. The insights gained from the present work may help to guide the design of new ortho-hydroxyl GFP core chromophores with improved fluorescence emission and brightness.

Theoretical Studies on the First Hyperpolarizabilities of One-dimensional Donor-bridge-acceptor Chromophores

The ground-state dipole moments and second-order nonlinear optical （NLO） properties of a series of one-dimensional （1D） chromophores with donor-bridge-acceptor （D-B-A） structures have been investigated by using the second-order MФller-Plesset （MP2） and density functional theory （DFT） methods with the basis set of 6-31＋G（d）. According to the calculated results, the relationship between the molecular static first hyperpolarizability （βμ） and the directions of electron transition has been summarized. In terms of the sign of βμ, these 1D organic chromophores were classified into two categories： type Ⅰ with negative βμ and type Ⅱ bearing positive βμ. The analyses show that the remarkable difference of the first hyperpolarizabilities between Ⅰ and Ⅱ chromophores is associated mainly with the electrostatic interaction between terminal groups and the transport electrons in excited states. Moreover, different from the popular viewpoint, the obtained results also show that most of this series of 1D D-B-A molecules are more charge-separated in the ground states than in the excited states. As a whole, this theoretical investigation, to some extent, can be considered as a useful reference in designing the NLO chromophores with large first hyperpolarizabilities.

Theoretical Studies on the First Hyperpolarizabilities of One-dimensional Donor-bridge-acceptor Chromophores and New Applications of BLA in Determining Molecular First Hyperpolarizabilities

We present a quantum-chemical analysis of the relationship between the bond length alteration （BLA） and the static first hyperpolarizability of a series of one-dimensional （1D） chromophores with donor-bridge-acceptor （D-B-A） structures. The calculated results show that the parameter BLA can be considered as an indicator to evaluate the molecular first hyper- polarizability. Along the direction of molecular ground-state dipole moments, the evolutions of BLA can be classified into three categories： the first is a non-monotonic line, which represents most chromophores; the second is monotonic increasing; and the third, contrarily, is monotonic decreasing. On the whole, the first hyperpolarizabilities of these studied chromophores are the monotonic functions of BLA along the direction of dipole moments. Therefore, the first hyperpolarizability of these 1D chromophores can be preliminarily evaluated in terms of the development of BLA without a rigorous computation. In other words, one can roughly estimate the relative magnitude of the first hyperpolarizability according to the optimized geometry.

Synthesis and Non-linear Optical(NLO) Properties of a Series of Alkoxysilane Derivative Chromophores

1 Introduction Nonlinear optical materials（NLO） have drawn a great intrest of some scholars and scientists in the last dacades because of their tremendous potential application in optoelectronic. The fabrication of efficient optoelectron devices is a challenging task because such systems need to meet the stringentable requirements for high optical quality and large and sustainable electro-optical（EO） response. In pursuit of NLO materials with excellent optoelectronic property,

Nonlinear optical properties of novel H-shaped chromophores

Novel and effective H-shaped chromophores were doped into polymethyl methacrylate （PMMA） to form guest-host polymer thin films. The measurement results of Maker fringe method show that the polymer thin films containing the H-shaped chromophores as a guest exhibit high second harmonic coefficients （d33） compared with other two-dimensional chromophores.

NONLINEAR OPTICAL PROPERTIES OF X-TYPE CHROMOPHORES AND THEIR DOPED FILMS

Two X-type chromophores, 2-[4-(4,5-di(4-nitrophenyl) imidazolyl) phenyl]-4,5-di(4-methoxyphenyl)-imidazole (DNPIPDMOPI), 2-[4-(4,5-di(4-nitrophenyl)-imidazolyl) phenyl]-4,5-di(4-aminophenyl)-imidazole (DNPIPDAPI), were synthesized and characterized. The results show that they possess good nonlinearity, considerable blue-shifted absorption (385 nm and 379 nm in THF) and high decomposition temperature (377 'C and 405 'C). These mean that the X-type chromophores possess a rather good nonlinearity-transparency-thermal stability trade-off. The multi-step corona-poling technique at elevated temperature and in-situ SHG measurements were used to obtain and evaluate the poled films of these chromophores doped in PMMA. The largest SHG signals appeared at 110-120°C, which are 12.5 pm/V and 16.7 pm/V respectively. The dependence of poling induced orientation stability on temperature was measured by depoling experiments and the results indicate that the poling-induced orientation of the films is stable at about 100°C. Theoretic analyses imply that better orientation stability arises from the X-type structure of chromophore. The X-type chromophore has two crossed intramolecular CT, both β xxx and β xyy can contribute to the second-order susceptibility, and the ratio of the tensorial components (γ= β xyy /β xxx ) is about 1/3, so the orientation decay of the films induced by rising temperature will provide a certain compensation for the contribution of β xyy of chromophores.

Synthesis,Characterization,and Linear and Nonlinear Optical Properties of Phenylene-vinylene Based Chromophores for Singlet Oxygen Generation

A series of symmetrical and unsymmetrical phenylene-vinylene （PV） based chro- mophores with the molecular configuration of donor-π-donor （D-g-D） were prepared and characterized. Iodine was first introduced into the Jr-conjugation backbone of the PV based chromophores in order to study the heavy atom effect on their linear absorption, two-photon absorption （TPA） properties, as well as singlet oxygen generation properties. TPA cross-sections of these chromophores were investigated by using the two-photon excited fluorescence method. The unsymmetrical chromophores were found to have larger TPA cross-section values compared to their symmetrical counterparts. For one of the unsymmetrical chromophores with the iodine incorporation, a large TPA cross section value with quenched emission was found. The decreased fluorescence quantum yield of a molecule can be ascribed to the increased intersystem crossing, which is favorable for enhancing the singlet oxygen generation. Therefore, the unsymmetrical PV based chromophores with heavy atom incorporation are promising singlet oxygen sensitizers for the photodynamic therapy application.

Feasible Synthesis of N,O-Bidentate Difluoroboron Chromophores through Direct Functionalization of Quinoxalin-2(1H)-ones with Ketones in One Shot

Organic difluoroboron complexes are a kind of potential platforms for a wide range of applications owing to their excellent photophysical properties.Herein,we have explored a simple and direct synthesis methodology for a library of N,O-bidentate difluoroboron complexes from quinoxalin-2(1H)-ones and ketones in one shot.The photophysical properties of the generated complexes were evaluated and the application potential of these compounds on subcellular imaging was also explored.

Triphenylamine-based highly active two-photon absorbing chromophores with push-pull systems

Two triphenylamine-based star-type push-pull chromophores(T1, T2) were designed and synthesized.Triphenylamine serves as the central core and acts as an electron-donating group surrounded by electronwithdrawing pentafluorobenzene or N,N-dimethyl substituted tetrafluorobenzene, which are connected by ethylene bridges. Single-crystal X-ray diffraction confirmed the structures and molecular arrangement of two chromophores. The systematic photophysical research of T1 and T2 absorption characteristics was carried out to gain a better understanding of how structure-property relationships affect the observed nonlinear optical absorption phenomenon. Complementary calculations based on density functional theory(DFT) further confirmed the experimental results. Both chromophores exhibited excellent two-photon absorption(TPA) properties in CH_(2)Cl_(2). Notably, T2 has more remarkable nonlinear optical absorption effects with the TPA cross-section up to 4.24 × 10~7GM. By adjusting the electronic structures of the chromophores through introducing pentafluorobenzene or N,N-dimethyl as functional groups with different electron-donating or withdrawing behaviors, the TPA performance of the small organic molecule could be greatly enhanced. These molecular structures with push-pull systems were excellent candidates for different two-photon applications.

Impacts of Water-Sediment Regulation Scheme on Chromophoric Dissolved Organic Matter in the Lower Yellow River

As a river with more than 3000 reservoirs in its watershed,the Yellow River has been affected by dams not only on the sediment load,but also on the water quality.Water-sediment regulation scheme(WSRS),which has been carried out annually in the Yellow River since 2002,is a typical human activity affecting river water quality.Chromophoric dissolved organic matter(CDOM)in river is susceptible to changes in ecological and environmental conditions as well as human activities.Here,we report variations in dissolved organic carbon concentrations,compositions and sources of CDOM in time series samples in the lower Yellow River during WSRS.In addition,a parallel factor fluorescence analysis(PARAFAC)method is applied to identify different fluorescent components in water samples during WRSR,showing four major components including tryptophan-like component(C1),microbial humic-like component(C2),terrestrial humic-like component(C3)and tyrosine-like component(C4).In general,C1 increased after water regulation,while C2 and C3 increased after sediment regulation,indicating that the water and sediment released by the dam have different effects on CDOM compositions.Under the impacts of the dam,source of CDOM in the lower Yellow River is mainly autochthonous related to microbial activities,and is regulated by the terrestrial input during WSRS period.Sediment resuspension inhibits microbial activities and reduces the production of autochthonous CDOM.Overall,human activities especially WSRS,as exemplified here,significantly alter the quality and quantity of CDOM in the lower Yellow River,affecting CDOM dynamics and biogeochemical processes in the estuarine environment.

Impact of transparent exopolymer particles on the dynamics of dissolved organic carbon in the Amundsen Sea,Antarctica

The Southern Ocean is an important carbon sink pool and plays a critical role in the global carbon cycling.The Amundsen Sea was reported to be highly productive in inshore area in the Southern Ocean.In order to investigate the influence of transparent exopolymer particles(TEP)on the behavior of dissolved organic carbon(DOC)in this region,a comprehensive study was conducted,encompassing both open water areas and highly productive polynyas.It was found that microbial heterotrophic metabolism is the primary process responsible for the production of humic-like fluorescent components in the open ocean.The relationship between apparent oxygen utilization and the two humic-like components can be accurately described by a power-law function,with a conversion rate consistent with that observed globally.The presence of TEP was found to have little impact on this process.Additionally,the study revealed the accumulation of DOC at the sea surface in the Amundsen Sea Polynya,suggesting that TEP may play a critical role in this phenomenon.These findings contribute to a deeper understanding of the dynamics and surface accumulation of DOC in the Amundsen Sea Polynya,and provide valuable insights into the carbon cycle in this region.

Microporous Hypercross-linked Conjugated Quinonoid Chromophores of Anthracene: Novel Polymers for CO_2 Adsorption

Microporous hypercross-linked conjugated quinonoid chromophores represent a novel class of amorphous polymers, synthesized by the reaction of anthracene with dimethoxy methane in the presence of FeCl3 catalyst. Their N2 adsorption isotherms confirm their microporous nature. Diffuse reflectance UV-Visible（DRS UV-Vis） spectroscopy confirms their matrix built with the conjugated quinonoids by their broad light absorption characteristics extending from 1000 nm to 200 nm with the absorbance maximum close to 400 nm. The catalyst cross-linked anthracene with ―CH2― bridges and subsequently dehydrogenating them to form quinonoids. Their Fourier transform infrared（FTIR） spectra showed their characteristic quinonoid vibrations between 1600 and 1700 cm-1. The synthesis of polymers was carried out at 30, 40, 50, 60, 70 and 80 ℃, but the quinonoid content of the polymer obtained at 80 ℃ was higher than that of the others. Their scanning electron microscopy（SEM） images showed microspheres of 1 to 5 μm size built with tiny particles. Their surfaces were not smooth. The polymer synthesized at 80 ℃ showed 5.1 wt% CO2 sorption at 25 ℃ and 0.1 MPa, but when it was recross-linked, the CO2 sorption increased to 8 wt%. Hence, hypercross-linked conjugated quinonoid chromophores of anthracene are good for sorption of CO2.

Systematic study of the structure-property relationship of a series of near-infrared absorbing push-pull heptamethine chromophores for electro-optics

This study reports the facile synthesis,characterization and quantitative structure-property relationship analysis of molecular and material properties of tricyanofuran-based(TCF)dipolar heptamethines with different electron donors of indoline(F1),benzo[e]-indoline(F2),benz[cd]indoline(F3),and Michler’s base derivatives(Ml and M2).The linear and nonlinear optical(NLO)properties of these chromophores have been thoroughly investigated,and the relationship between molecular and bulk response has been analyzed and compared with dipolar tetraene AJLZ53 as one of the best chromophores for electro-optic(EO)devices.In particular,we provide responsible data collection and analysis of optical and EO properties for poled thin films using a widelyrecognized and accredited methodology of prism coupling system with the help of rigid oriented gas model.We found that these push-pull heptamethines with synthetic efficacy exhibit high near-infrared absorption,excellent chemical stability and large hyperpolarizabilities(β)varied from 1,023×10^-30 esu for F1,3,047×10^-30 esu for M1,and 3,547×10^-30 esu for F3 at 1,304 nm in poled films,respectively.Theβvalues of these molecules are among the highest ones for TCF-based dipolar chromophores,and also agree well with reported analytical results in the solutions.In poled polymers with a modest chromophoric loading density of1.3×10^20 cm^-3,Ml and M2 give a high poled-induced noncentrosymmetric order and relatively large r33 values around40 pm V^-1 at 1,304 nm,indicative of largeμβvalues and suitable structural modification for high poling efficiency.Furthermore,a binary EO polymer based on the co-loading of Ml and AJLZ53 achieve a large r33 value of 143.3 pm V^-1 at 1,304 nm.Our studies suggest that concise synthesis and molecular design of push-pull polymethines can be well guided by the tabulation of their linear and NLO properties in bulk materials,and streamline future development of high performance organic EO materials for photonic applications.

Synthesis and nonlinear optical properties of copolymers of fluoro-containing bisphenol A and chromophores

A series of new fluoro-containing copolymers have been synthesized by a Mitsunobu reaction with 4,4＇-（hexafluoroisopropylidene） bisphenol A（6FBPA） and the corresponding N,N-dihydroxyethylaminoaryl azo or ring-locked triene compounds, which have high thermal stability and good solubility in organic solvents.The nonlinear optical（NLO） measurements made by Marker fringe method at 1064 nm indicate that the copolymers embedded with the ring-locked triene and azo chromophores exhibit higher macroscopic nonlinear optical coefficient（70.2 pm/V and 26.5-34.6 pm/V,respectively）.Thermal analysis and UV-visible absorption spectra show that the copolymers have good thermal stability（T_d= 264-319℃） and optical transparency （λ_（max）500 nm）.

Electrochemical,thermal,and photophysical properties of novel two-photon absorption chromophores

Electrochemical, thermal, and photophysical properties of novel two- （BPODPA）, four- （BBPOPA）, and six-branch （TBPOA） triphenylamine chromophores are studied. The decomposition temperature of chro- mophores reaches 373 - 412 ℃. The electrochemical properties is explored by cyclic voltammetry. The ionization potential of chromophores is in the range of 5.14 - 5.18 eV. Excitation at 400 nm reveals emission peaks at 483 - 487 nm and the fluorescence quantum yields are 0.73 - 0.75 in CH2Cl2. Two-photon absorption （TPA） properties of chromophores are measured by nonlinear transmission method. The maximum TPA cross-section values are measured at 758 nm to be 20369 GM （1 GM=10^-50 cm^4 -s/photon） for TBPOA, 7024 GM for BBPOPA, and 1227 GM for BPODPA, respectively. When pumped with 800-nm laser irradiation, chromophores show strong two-photon excited blue-green fluorescence at 502 - 518 nm. These results provide a basis for understanding the electronic and optical properties of the conjugated multi-branch chromoohore in terms of the underlying molecular and electronic structures.

SECOND-ORDER NONLINEAR OPTICAL HYPERBRANCHED POLYMER CONTAINING ISOLATION CHROMOPHORE MOIETIES DERIVED FROM BOTH “H”-TYPE AND STAR-TYPE CHROMOPHORES

An NLO hyperbranched polymer （HP1） derived from both ＂H＂-type and star-type chromophores was synthesized successfully for the first time with high yield via one-pot ＂A2 ＋ B3＂ Suzuki polymerization reaction. Isolation chromophore was also introduced to further improve its performance. Although under the test conditions, the films of HP1 could not be poled completely, it still demonstrated satisfactory macroscopic NLO effect with the second harmonic generation （SHG） coefficient d33 value of 36 pm/V.

Synthesis,structure and nonlinear optical properties of two novel two-photon absorption chromophores

Two triphenylamine-based derivatives that can be used as two-photon absorption chromophore,tris{4-[4-(3-trifluoromethyl-3-oxopanoyl)]phenyl}amine (1) and tris{4-[4-(3-phenyl-3-oxopanoyl)] phenyl} amine (2) were successfully synthesized and fully characterized by elemental analysis,IR,1H NMR and MS. The single crystal X-ray diffraction analysis showed that the molecules possess D-(π-A)3 structures. One-and two-photon absorption and fluorescence in various solvents were experimentally investigated. A data recording experiment proved the potential application of these chromophores.