Effects of Donor and Acceptor on Optoelectronic Performance for Porphyrin Derivatives: Nonlinear Optical Properties and Dye-sensitized Solar Cells

Typical asymmetric donor-π-bridge-acceptor(D-π-A) zinc porphyrin dyes have been synthesized, and further modified by reacting the ethynyl groups of them with click reagent through a formal [2+2] click reaction. The electronic interaction between the push and pull electronic groups and the click reaction process were investigated by UV-Vis absorption spectroscopy. The nonlinear optical(NLO) properties of the dyes were studied by the Z-scan technique and clearly reverse saturable absorption to saturable absorption(RSA-SA) transition could be observed through click reaction of the dyes with TCNE. Furthermore, the photovoltaic properties of these porphyrin dyes were reaso- nably explained by the J-V curve fitting based on the equivalent-circuit model as well as the comparison between the absorption and incident-photon-to-current-conversion efficiency(IPCE) spectra. Besides, these dyes with different donors or acceptors could self-assembly into different microstructures by phase transfer methodology.     

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.     

Conformationally restricted dipyrromethene boron difluoride (BODIPY) dyes: highly fluorescent, multicolored probes for cellular imaging

Novel fluorescent, conformationally restricted dipyrromethene boron difluoride (BODIPY) dyes have been prepared by introducing a naphthalenyl group at the meso position of the BODIPY core. These BODIPY dyes exhibit increased fluorescence quantum yields compared with dyes that have a meso-position phenyl group with internal rotation. The absorption and emission wavelengths of such conformationally restricted BODIPY dyes can be easily tuned to the near-IR range by derivatization through a condensation reaction with benzaldehyde derivatives. The two-photon absorption properties of these BODIPY dyes were also investigated and the results show that they exhibit increased two-photon excited fluorescence compared to analogue dyes that contain a phenyl group. The one- and two-photon fluorescence imaging of living cells by using selected BODIPY dyes has been successfully demonstrated.     

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.     

Novel Heptamethine 3H-Indocyanines and their Spectral Properties

Novel heptamethine 3H-indocyanine dyes are synthesized and embedded into a matrix of silica gel derived from tetraethoxysilicane. The photophysical properties of these near infrared dyes in various solvents and in SiO2 sol gel were investigated. The results show that the dyes containing cyclohexenylene bridge and N-(p-carboxy)benzyl groups have better photostability and longer absorption wavelength than those containing linear heptamethine bridge and/or N-(5-carboxy)pentanyl groups. The absorption maxima of these dyes are in reverse proportion to the polarity of the solvents. The microenvironment of the dyes in SiO2 sol-gel characters medium polarity (between methanol and DMF) according to the absorption maxima.     

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.     

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.     

Carbazole- and Fluorene-Fused Aza-BODIPYs: NIR Fluorophores with High Brightness and Photostability

Three new aza-BODIPY dyes incorporating fused fluorene or carbazole moieties have been prepared. The dyes show significant enhancement of photophysical properties compared to the parent 1,3,5,7-tetraphenyl aza-BODIPY (TPAB): a bathochromic shift of the absorption maximum (up to 2700 cm⁻¹) and emission maximum (up to 2270 cm⁻¹); an almost threefold increase in molar absorption coefficients (to ca. 230 000 M⁻¹ cm⁻¹) and a significant increase in the fluorescence quantum yield to 49–66 %. Owing to the combination of these properties, the new aza-BODIPY dyes belong to the brightest NIR dyes reported. The dyes also show excellent photostability. Due to their outstanding properties, the new dyes represent a promising platform for further exploration in biomedical research. A pH indicator containing only one fused carbazole unit was also prepared and shows absorption and emission spectra that are bathochromically shifted by about 110 and 100 nm, respectively, compared to the indicator dye based on the TPAB chromophore.     

Synthesis and Modeling of Acridine Dyes as Potential Photosensitizers for Dye‐Sensitized Photovoltaic Applications †

We have synthesized novel aromatic amine‐substituted acridine dyes as potential candidates for the photosensitizers in dye sensitized nanocrystalline semiconductor based solar cells (DSSC) cells. The protonation and quaternization of the acridine nitrogen led to acridine dyes with extended absorption from 400–800 nm. Computational modeling was used to evaluate a variety of structures to achieve insights for correlating these types of molecular structures with predicted absorption spectra. Pertinent dihedral angles as well as bond lengths were evaluated to assess and compare planarity and conjugation for these dyes. Other predictions include plots of the HOMO and LUMO levels to qualitatively examine electron distributions and the potential for electron injection. The results from modeling along with the experimental data consisting of synthesis, characterization and UV‐visible absorption properties of the selected dyes are presented.     

A spectral approach to determine location and orientation of azo dyes within surfactant aggregates

The UV–vis absorption properties of azo dyes are known to exhibit a variation with the polarity and acidity of the dye environment. The spectral properties of a series of anionic azo dyes were characterized to further probe the interaction of these dyes with two types of surfactant aggregates: (1) the spherical micelles formed in aqueous solution by alkyltrimethylammonium bromide (C_nTAB) surfactants with n = 10–16 and (2) the unilamellar vesicles spontaneously formed in water from binary mixtures of the oppositely-charged double-tailed surfactants cationic didodecyldimethylammonium bromide (DDAB) and anionic sodium dioctylsulfosuccinate (Aerosol OT or AOT). The observed dye spectra reflect the solvatochromic behavior of the dyes and suggest the location and orientation of the dye within the surfactant aggregates. Deconvolution of the overall spectra into sums of Gaussian curves more readily displays any contributions of tautomeric forms of the azo dyes resulting from intramolecular hydrogen bonding. The rich variation in UV/vis absorption properties of these anionic azo dyes supports their use as sensitive tools to explore the nanostructures of surfactant aggregates.     

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.     

桥链七甲川菁的合成及光性能

菁是一种具有多功能用途的染料,除用作卤化银感光材料及有机光导材料的光谱增感剂、光记录材料中记录介质外,还可作为染料激光器中用的激光染料.我们曾合成了四甲川苯乙烯菁、五甲川(艹粦)及五甲川吡喃鎓等红外染料作为激光染料,测定了它们的光性能.本文合成了具有桥链的七甲川菁,研究了这些桥链七甲川菁的吸收光谱及荧光光谱,并以YAG激光倍频(532nm)作泵浦源,测定了它们的激光调谐范围、中心波长及激光转换效率.     

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.     

Novel Iron-Based Polynuclear Metal Complexes [FeII(L)(CN)4]2–[FeIII(H2O)3Cl]2: Synthesis and Study of Photovoltaic Properties for Dye-Sensitized Solar Cell

A series of novel polynuclear iron-based photosensitizers (1–3) with cyano-bridged to form a molecular square were synthesized and their optical, electrochemical, and photovoltaic properties were investigated. The modification of anchoring groups with 4,4'-dicarboxy-2,2'-bipyridine, 2,2'-bipyridine, and 4,4'-dimethoxy-2,2'-bipyridine does not show significant changes on the both absorption and electrochemical properties of these iron-based dyes. This indicates that the polynuclear iron-based photosensitizers have better flexibility to regulate their physical properties of solubility, surface absorption, and thin-film formation for device preparation. The polynuclear new dyes show power conversion efficiencies ranged from 0.43 to 0.48% that is almost the best system among the published iron-based photosensitizers. These iron-based dyes were able to chemisorb on TiO₂ surface efficiently and then promoting electron injection and photocurrent generation in a dye-sensitized solar cell with solar irradiation.

     

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.     

Novel Cyanine Dyes: Synthesis,Characterization and Photosensitization‐Structure Correlation

Novel furo, thieno and pyrrolo[2,3‐b]pyrazole cyanine dyes were synthesized. The structure‐photosensitization properties correlation of the dyes were examined in 95% ethanol solution by absorption spectroscopy. The chemical structure of the starting biheterocyclic compounds and their derived cyanine dyes were confirmed by elemental analysis, IR and ¹H NMR spectroscopy.     

Boron dipyrromethene analogs with phenyl, styryl, and ethynylphenyl substituents: synthesis, photophysics, electrochemistry, and quantum-chemical calculations

Seven fluorescent boradiazaindacene-based compounds with one or two phenyl, ethenylphenyl, and ethynylphenyl substituents at the 3- (or 3,5-) position(s) were synthesized via palladium-catalyzed coupling reactions with the appropriate 3,5-dichloroBODIPY derivative. The effect of the various substituents at the 3- (or 3,5-) position(s) on the spectroscopic and photophysical properties were studied as a function of solvent by means of UV/vis absorption, steady-state, and time-resolved fluorometry, and theoretical modeling. The emission maxima of the symmetrically 3,5-disubstituted dyes are shifted to longer wavelengths (by 30 to 60 nm) relative to the related asymmetrically 3,5-disubstituted ones. Introduction of styryl substituents causes the largest red shift in both the absorption and emission spectra. BODIPY derivatives with ethynylaryl groups also shift the spectral maxima to longer wavelengths compared to aryl-substituted ones but to a lesser degree than the styryl compounds. The quantum-chemical calculations confirm these trends and provide a rationale for the spectral shifts induced by substitution. The fluorescence quantum yields of the ethenylaryl and ethynylaryl analogs are significantly higher that those of the aryl-substituted dyes. The 3,5-diethynylaryl dye has the highest fluorescence quantum yield (approximately 1.0) and longest lifetime (around 6.5 ns) among the BODIPY dyes studied. The differences in the photophysical properties of the dyes are also reflected in their electrochemical properties where the symmetrically 3,5-disubstituted dyes display much lower oxidation potentials when compared to their asymmetric counterparts.     

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.     

Long-wavelength boradiazaindacene derivatives with two-photon absorption activity and strong emission: versatile candidates for biological imaging applications

Novel D-π-D-type boradiazaindacene dyes exhibit considerable two-photon absorption cross-section and strong red emission. Cell stained with these dyes show bright intracellular fluorescence. These properties qualify them as competitive candidates for fluorescent bioimaging applications     

Effect of poly-HEMA hydrophilic gel environment on the photo-physical behavior of rhodamine dyes

The absorption spectra of rhodamine B (RB) chloride, rhodamine 6G (R6G) tetrafluoroborate and rhodamine 6G chloride in poly-2-hydroxyethyl methacrylate hydrogel (PHEMA) matrix were studied using absorption spectroscopy in the visible region. The transport and aggregative properties of these ionic dyes in aqueous solution across the hydrophilic gel were also investigated. The similarities of absorption spectra of RB in aqueous solutions and in hydrogel host suggest that the hydrogel framework has a minor effect in their absorption spectra. In contrast, there is a relatively strong interaction or electrostatic forces between R6G dyes and the hydrogel matrix. The permeability of R6G chloride through hydrogel host is seen to be markedly higher than RB chloride and R6G tetrafluoroborate.