Synthesis, fluorescence and two-photon absorption properties of multichromophoric boron-dipyrromethene fluorophores for two-photon-excited fluorescence applications

The synthesis and the characterization of new multichromophoric boron-dipyrromethene dyes are described. Their absorption, photoluminescence as well as their two-photon absorption properties have been investigated. This work shows that assembling several dyes in conjugated multichromophoric structures is a promising strategy for improving the two-photon absorption properties of such fluorophores in the NIR region while retaining their excellent photoluminescence properties.     

Fine Tuning the Performance of DSSCs by Variation of the π‐Spacers in Organic Dyes that Contain a 2,7‐Diaminofluorene Donor

Organic dyes that contain a 2,7‐diaminofluorene‐based donor, a cyanoacrylic‐acid acceptor, and various aromatic conjugation segments, which are composed of benzene, fluorene, carbazole, and thiophene units, as a π‐bridge have been synthesized and characterized by optical, electrochemical, and theoretical investigations. The trends in the absorption and electrochemical properties of these dyes are in accordance with the electron‐donating ability of the conjugating segment. Consequently, the dyes that contained a 2,7‐carbazole unit in the π‐spacer exhibited red‐shifted absorption and lower oxidation potentials than their corresponding fluorene‐ and phenylene‐bridged dyes. However, the enhanced power‐conversion efficiency that was exhibited by the fluorene‐bridged dyes in the DSSCs was attributed to their broader and intense absorption. Despite the longer‐wavelength absorption and reasonable optical density, carbazole‐bridged dyes exhibited lower power‐conversion efficiencies, which were ascribed to the poor alignment of the LUMO level in these dyes, thereby leading to the inhibition of electron injection into the TiO₂ conduction band.     

Syntheses of Novel Asymmetric Cyclopentanone Dyes and Measurement of Two－photon Absorption Cross－section

A simple synthesis route with a high yield of novel asymmetric cyclopentanone dyes 3a—3e and their highly two-photon up-converted fluorescences are reported. The dyes have good solubilities in most of ordi-nary solvents, a wide UV absorption wavelength range from 380—540 nm, and high fluorescence quantum yields. The two-photon absorption cross-sections of dyes 3a—M were measured in chloroform by a two-pho-ton induced fluorescence method. All of these properties of the new dyes make them suitable for being used as two-photon fluorescent probes.     

Synthesis and characterization of guest-host azo dyes with broad absorption bands

Three groups of dyes were synthesized and characterized in order to examine their solubility, absorption spectrum, and order parameter in liquid crystal hosts. Our synthesis method allowed the formation of the diazonium salts and the diazo coupling in ethyl acetate instead of an aqueous medium, permitting the formation of long and neutral azo dyes. In the liquid crystal BDH-E7, they showed order parameters in the range of 0.52 to 0.76. The two dyes with the longest molecular lengths were particularly interesting due to their very broad absorption spectra in the visible region. Each of these two compounds behave as single component black dye guest/host systems, which generally require a mixture of two or three dyes in the liquid crystal host. These dyes were also evaluated for use in polymer dispersed liquid crystal films.     

Effects of heterocyclic ring and amino-ethyl-amino group on the electronic and photophysical properties of a triphenylamine-pyrimidine dye

Introduction of a heterocyclic ring and an amino-ethyl-amino group to donor-acceptor (D-A) type photosensitive dyes can modulate the lifetime of the charge separation generated in the D-A dyes as well as their electronic and UV-vis absorption properties. Here we perform density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations to study 11 derivatives of a triphenylamine-pyrimidine, namely MTPA-Pyc, in order to improve the performance of MTPA-Pyc as solar cell sensitizers. Five heterocyclic rings and an amino-ethyl-amino group were introduced on the styryl moiety of MTPA-Pyc. The results show that the introduction of heterocyclic rings generally causes an absorption red shift, but the absorption intensity reduces as a result of the increase in the dihedral angle between the donor and acceptor. Further, introduction of an amino-ethyl-amino group to these dyes with a heterocyclic ring modification disrupts the conjugation between the donor and acceptor, which does not benefit the absorption but may have the potential to increase the lifetime of charge separation of the dyes. We identify 2 out of 11 dyes that have the best potential for solar cell applications.     

Spectroscopic studies of a near-infrared absorbing pH sensitive aminodienone-carbocyanine dye system

Synthetic red and near-infrared absorbing dyes may be used as probe molecules in a large number of applications. Dyes exhibiting spectral changes with hydrogen ion concentration are useful as pH probes. Those dyes which have their absorption and fluorescence maxima in the long wavelength region of the visible spectral region are specially valuable because of decreased interference and semiconductor laser applications. In this paper we have evaluated an aminodienone dyes 1 which demostrates pH dependent absorption and fluorescence spectra as well as solvent polarity dependence. In organic solvents the long wavelength absorption band of the dye is in the reduced interference region. The absorption maximum is at 535 nm in neutral or alkaline solutions in methanol. The absorption spectra undergo a strong bathochromic shift in the presence of acids (lambda(max) = 709 nm) with a concomitant change in the fluorescence spectra. This pH sensitive dye was found to be specially especially useful for organic solvents. The analytical utility of this and similar near-infrared absorbing dyes is discussed.     

新型水溶性荧光标示剂吲哚方酸菁染料的合成及光谱性能

用方酸与不同的N烷基取代吲哚啉季铵盐缩合制备了一系列对称的水溶性方酸菁染料. 通过核磁共振氢谱和质谱对合成的染料结构进行了表征, 研究了它们在不同溶剂中的吸收和发射光谱. 结果表明, 随着溶剂极性的增大, 染料的吸收光谱发生蓝移, 表现为负向溶剂化效应, 在极性溶剂中的荧光量子产率比在水中的大. 考察了N位取代基对染料水溶液光稳定性的影响, 结果表明在吲哚环N原子上引入较大的苄基有助于提高光稳定性, 且随着苄基上取代基吸电子能力的增强, 染料的光稳定性增强.     

Singlet oxygen generation ability of squarylium cyanine dyes

The quantum yields for singlet oxygen generation of several squarylium cyanine dyes derived from benzothiazole, benzoselenazole and quinoline, displaying absorption within the so-called “phototherapeutic window” (600–1000 nm), were determined, envisioning their potential usefulness for photodynamic therapy (PDT). The determination was performed by a direct method measuring the luminescence decay of the dyes in the near infrared. Considering the absorption and the quantum yields displayed by some of the dyes, these seemed to be potential candidates as sensitizers for PDT.     

Synthesis and characterization of guest-host azo dyes with broad absorption bands

Abstract

Three groups of dyes were synthesized and characterized in order to examine their solubility, absorption spectrum, and order parameter in liquid crystal hosts. Our synthesis method allowed the formation of the diazonium salts and the diazo coupling in ethyl acetate instead of an aqueous medium, permitting the formation of long and neutral azo dyes. In the liquid crystal BDH-E7, they showed order parameters in the range of 0.52 to 0.76. The two dyes with the longest molecular lengths were particularly interesting due to their very broad absorption spectra in the visible region. Each of these two compounds behave as single component black dye guest/host systems, which generally require a mixture of two or three dyes in the liquid crystal host. These dyes were also evaluated for use in polymer dispersed liquid crystal films.     

溴化银晶体光谱敏化光电流的研究和染料增感性能的判据

本文以AgBr晶体和菁染料为对象,对AgBr晶体的光电流进行了研究。实验发现,AgBr晶体经其本征吸收波长的光辐照后,可产生新的诱导吸收带。用诱导吸收带波长范围内的光辐照AgBr晶体,在非本征吸收区可测量到自敏化光电流。若染料吸附在AgBr晶体片上,则其敏化光电流将叠加在自敏化光电流上。增感染料对AgBr晶体的阳极和阴极光电导均有不同程度的敏化作用。本文在实验研究的基础上,提出了对染料增(减)感性能的判据S_D,比现有的一些判据更具有综合性。利用S_D—λ曲线可以较直观地对染料的增(减)感性能做出预测。本文利用S_D判据对一些实用增感染料及其组合作了分析。     

Spectroscopic and thermal properties of short wavelength metal (II) complexes containing alpha-isoxazolylazo-beta-diketones as co-ligands

Two new azo dyes of alpha-isoxazolylazo-beta-diketones and their Ni(II) and Cu(II) complexes with blue-violet light wavelength were synthesized using a coupling component, different diazo components and metal (II) ions (Ni2+ and Cu2+). Based on the elemental analysis, MS spectra and FT-IR spectral analyses, azo dyes were unequivocally shown to exist as hydrazoketo and azoenol forms which were respectively obtained from the solution forms and from the solid forms. The action of sodium methoxide (NaOMe) on azo dyes in solutions converts hydrazoketo form into azoenol form, so azo dyes are coordinated with metal (II) ions as co-ligands in the azoenol forms. The solubility of all the compounds in common organic solvents such as 2,2,3,3-tetrafluoro-1-propanol (TFP) or chloroform (CHCl3) and absorption properties of spin-coating thin films were measured. The difference of absorption maxima from the complexes to their ligands was discussed. In addition, the TG analysis of the complexes was also determined, and their thermal stability was evaluated. It is found that these new metal (II) complexes had potential application for high-density digital versatile disc-recordable (HD-DVD-R) system due to their good solubility in organic solvents, reasonable and controllable absorption spectra in blue-violet light region and high thermal stability.     

新型含有多氰基受体单元的近红外敏化染料的合成及其光伏性能研究

本文分别以三苯胺、二甲基苯胺和吲哚啉单元为电子给体,设计并合成了3个新型D-π-A体系近红外敏化染料分子5C-1、5C-2和5C-3,并对其结构进行了表征,详细研究了在溶液中以及吸附到电极上的吸收光谱.该系列敏化染料在550—850 nm之间具有较强的吸收,尤其5C-3的吸收边带已达到954 nm.当该系列敏化染料吸附到TiO₂上时,吸收边带大幅红移,显示有利于染料捕获长波段区域的太阳光.通过循环伏安法,测定了染料的电化学性质,发现该系列敏化染料的最低未占有轨道(LUMO)能级与TiO₂导带并不匹配,因此选用导带能级更正的SnO₂作为阳极半导体材料进一步测试了该系列染料的光电性能,以发展具有优良性能的长波段响应的近红外敏化剂.     

Near-infrared fluorescent probes: synthesis and spectroscopic investigations of a few amphiphilic squaraine dyes

With the objective of developing near-infrared fluorescence probes for biological applications, a few squaraine dyes 3a-d, containing amphiphilic substituents, were synthesized and their photophysical properties have been investigated in the presence and absence of the organized media. These dyes exhibited absorption in the range 630-650 nm, with significant absorption coefficients (epsilon = 1-3 x 10(5) M(-1) cm(-1)) in the aqueous medium. The fluorescence spectra of these dyes showed emission maximum from 660 to 675 nm, depending on the nature of substituents. The fluorescence quantum yields were in the range from 0.15 to 0.21 in ethanol, but 10 times lower values were observed (phi(f) = 0.01-0.02) in the aqueous medium. In the presence of micelles such as cetyltrimethylammonium bromide, sodium dodecyl sulfate, and Triton X-100, these dyes showed negligible changes in their absorption properties, whereas a significant enhancement (5-10-folds) in their fluorescence yields was observed. Picosecond time-resolved studies indicated that these dyes show single-exponential decay in ethanol and ethanol-water mixtures; however, they exhibit biexponential decay with longer lifetimes in the presence of the micellar media. The results indicate that these novel amphiphilic squaraine dyes 3a-d, which exhibit favorable photophysical properties, good solubility in the aqueous medium, and interact efficiently with micelles, can have potential biological applications as near-infrared fluorescence sensors.     

紫外吸收染料研究进展

紫外线具有高能特性,能够伤害人类皮肤和破坏有机化合物,而紫外吸收染料既吸收紫外线,赋予染料抗紫外整理功能,又可提高有机染料的光稳定性,是一类新型的纤维防护功能染料,现已成为染料化学工作者的一个新的研究热点.     

Synthesis and properties of functional dyes with squaraine–naphthalene diimide hybrid structure

Naphthalene diimides (NDIs) are promising candidate for electron acceptors due to their low-lying HOMOs and LUMOs. The functinalization of soluble NDIs at the 2,6-position affects the absorption and electrochemical properties. In this study, NDI-based hybrid dyes NDI-SQ-A, B fused with squaraine chromophore were designed and synthesized in order to elucidate the effects of the substitution on their optical and electrochemical properties. These dyes were successfully synthesized by Stille coupling reactions using 3-stannylcyclobutenediones and brominated NDI derivative, followed by a condensation reaction. DFT calculation predicts that the present dyes adopt distorted structures coming from a steric hindrance between semisquaraine and NDI moieties. The hybrid dyes show low-lying LUMOs due to the introduction of electron-deficient NDI moiety and broad absorption spectra in the far-red region. The absorption spectra of their thin films were bathochromically shifted relative to those in solution, indicating that hybrid dyes formed J aggregates.     

Synthesis and Application of 2-Arylazo-3-Cyano Thieno [2,3-b]Naphthoquinones

The paper describes the synthesis of 2-amino-3-cyanothieno[2,3-b]naphthoquinone and its utilisation to prepare range of azo disperse dyes. These novel arylazo dyes were studied with respect to their color and constitution relationship. Application of these dyes on polyester fibres and their fastness properties were stated. These dyes were characterised by PMR, IR and visible absorption spectra.     

Recoordination of a metal ion in the cavity of a crown compound: a theoretical study

The absorption spectra of styrylbenzothiazolium dye derivatives were calculated by the time-dependent density functional (TD DFT) method. The dyes of interest were (p-dimethylamino)styrylbenzothiazolium dye and its protonated form as well as aza-15(18)-crown-5(6)-containing dyes and their complexes with alkali (K⁺ and Na⁺) and alkaline-earth (Ca²⁺, Sr²⁺, and Ba²⁺) cations. Several low-lying conformers of the azacrown-containing dyes were considered. The electronic and geometric structures of the excited states responsible for the appearance of the long-wave (π-π*) absorption bands are studied. Complexation causes a hypsochromic shift of the long-wave absorption band correlating with the pyramidality of the crown ether nitrogen in the complex. The interaction of the cation with 3–4 solvent molecules or a counterion (ClO₄ ^?) considerably reduces this shift, especially in the conformers without the metal-nitrogen bond. In some cases, the long-wave absorption band is close to the absorption band of the free dye. Similar results were obtained using the polarizable continuum model of solvation. Excited-state structures of the free model dye and the free azacrown-containing dyes exhibit a tendency to bond alternation. Conversely, the cationic complexes of the crown-containing dyes and the protonated model dye exhibit a tendency to bond equalization in the excited state. The changes in the excited-state geometries of the free dyes and their complexes account for the complexation-induced fluorescence enhancement observed in the experiments.     

Bischromophoric styrylpyridinium dyes. Spectroscopic properties of 1,3-bis-[4-(p-N,N-dialkylaminostyryl)pyridinyl]propane dibromides

The photophysical properties of newly synthesized bischromophoric solvatochromic stilbazolium dyes, 1,3-bis-[4-(p-N,N-dialkylaminostyryl)pyridinyl]propane dibromides (C1-C9), were studied in a series of solvents and their spectroscopic properties were compared with structurally related, monochromophoric styrylpyridinium dyes (SP1-SP9). The position of the UV-vis absorption spectra maximum of novel dyes is only slightly solvent polarity dependent in contrast to the fluorescence spectra that show pronounced solvatochromic effect demonstrated by a large Stokes shifts. The influence of the solvent on absorption and emission spectra, and the solvatochromic properties observed for both ground and first excited states for all the dyes were used for the evaluation of their excited state dipole moments. The ground state dipole moments of both mono- and bischromophoric dyes were established by applying ab initio calculations. The calculations and measurements unexpectedly show that the bischromophoric dyes are characterized by ground state dipole moments being equal to about half of that characterizing their monomeric equivalents, while the excited state dipole moments of bischromophoric dyes are about 10-25% higher in comparison to their monomeric equivalents.     

New dyes based on amino-substituted acridizinium salts--synthesis and exceptional photochemical properties

The novel amino-substituted acridizinium salts 5a and 5b represent a new class of cyanine dyes which exhibit intense color along with efficient fluorescence properties. These dyes show moderate solvatochromism in their absorption and emission spectra. The absorption and emission shifts of the two chromophores display a reasonable correlation with solvent parameters such as donor and acceptor number. It was found that the dyes 5a and 5b interact with DNA, with quenching of the band intensies accompanied with a red shift of the absorption and emission bands. Moreover, irradiation of salts 5a and 5b in the presence of DNA results in DNA damage. Solution photolysis of acridizinium salt 5a gave the head-to-tail dimers as the major products (>95%), whereas the acridizinium salt 5b afforded the anti-head-to-tail dimer along with both head-to-head isomers. The latter are thermally labile and rapidly revert to the monomer.     

Studies of 2‐Azaazulenium Derivatives: Unsymmetrical Trimethine Cyanine Dyes Bearing a 2‐Azaazulenium Moiety as One of the Terminal Groups

We report here the synthesis of a series of symmetrical and unsymmetrical trimethine cyanine dyes derived from 2‐azaazulene, combined spectral and quantum‐chemical investigations of their molecular geometry and electron structure, as well as the nature of the lowest electron transitions. Based on the analysis of both calculations and experimental data obtained from absorption and ¹³C NMR spectra, it was concluded that the 2‐azaazulene residue can be treated as a weakly basic terminal group; its donor properties are provided with the participation of the HOMO?1, in contrast to the typical Brooker’s terminal residues with their donor HOMOs. The new classification of the terminal groups of cyanine dyes, and hence the classification of types of unsymmetrical cyanines, is proposed. It is shown that the nature of the higher electron transitions (delocalized or local) in the cyanine dyes depends on their type. In the unsymmetrical trimethine cyanine of the mixed type, negative deviations are observed in their absorption spectra.