Synthesis of thiophene-substituted aza-BODIPYs and their optical and electrochemical properties

A series of novel thiophene-substituted aza-BODIPY dyes were synthesized by means of a standard procedure and complemented by a Stille-coupling of a brominated species with 2-tributylstannylthiophene. The optical as well as the electrochemical properties of the compounds were investigated and compared to result of density functional theory (DFT) calculations. The influence of the thiophene substituents is discussed in dependence of the position at the aza-BODIPY core regarding the HOMO and LUMO frontier orbitals. The different distributions of the HOMO and LUMO coefficients over the BODIPY core lead to a variable influence of the thiophene substituents on the HOMO and LUMO energies, being the origin of the tunable optical and electrochemical properties.     

Synthesis and photochromic properties of a dithia-dithienylethenophane

The thermally irreversible photochromic compound dithia-dithienylethenophane was synthesized, which is the first example of a dithienylethene bridged with benzene ring and due to the fixation to the photoactive anti-conformation the quantum yield for the photocyclization reaction became higher than that of the corresponding nonbridged type dithienylethene.     

Synthesis of soluble oligothiophenes bearing cyano groups, their optical and electrochemical properties

The synthesis and the characterization of twelve new soluble oligothiophenes, possessing two to four 3,4-dicyanothiophene units in their backbone, are described. These semiconductors are prepared through Stille coupling and/or homo-coupling reactions. Cyclic voltammetry studies have been performed to evaluate their stability as n-type semiconducting materials under ambient conditions. The measured electrochemical and optical properties are fully supported by quantum-chemical calculations.     

Synthesis and photophysical properties of porphyrins with fluorenyl pendant arms

Symmetrical-A₄-porphyrins bearing four fluorene donor moieties TOFP (5,10,15,20-tetra(4-(2 methyloxyfluorenyl)phenyl)porphyrin) as well as eight fluorene arms OOFP (5,10,15,20-octa(3,5-(2-methyloxyfluorenyl)phenyl)porphyrin) were synthesized and characterized. Preliminary photophysical properties are reported. In comparison to the reference tetraphenylporphyrin TPP, the luminescence properties are slightly improved. The fluorescence quantum yields of tetrafluorenylporphyrin TOFP (1) and octafluorenylporphyrin OOFP (2) are 0.10 and 0.13, respectively.     

Synthesis of tetra-oligothiophene-substituted calix[4]arenes and their optical and electrochemical properties

A facile and efficient approach to synthesize tetra-oligothiophene-substituted calix[4]arenes, Calix-OT(n) with n up to 4 using palladium-catalyzed Kumada coupling of thienylmagnesium bromide and bromo-substituted calix[4]arene as a key step has been developed. The close proximity of the tetra-oligothiophenes constructed within a calix[4]arene assembly leads to peak/band broadening, spectral shifting, i.e., blue-shift in absorption and red-shift in emission spectra as well as fluorescence quantum yield quenching as compared to those of monomers indicating the existence of chromophoric interaction. We have shown that the intra-chromophoric interaction lowers the first ionization (raises HOMO level) of an oligothiophene within an assembly. It also stabilizes the formation of a radical cation, which results in an increase in the subsequent voltammetric oxidation and the occurrence of the higher oxidation states as compared to the monomeric counterparts. This assembly can serve as a model for the investigation of molecular interaction of π-conjugated systems.     

Nanosized starlike molecules. Synthesis and optical properties of tris- and tetrakis[oligo(disilanylenebithienylene)dimethylsilyl]benzene

The syntheses of two types of starlike molecules with the arms that extend to three and four directions have been reported. The molecules with the arms consisting of a regular alternating arrangement of a silicon-silicon bond and bithienylene unit that extend to three directions were synthesized by the reactions of 1,3,5-tris(chlorodimethylsilyl)benzene, which was chosen as a core, with the lithio[oligo(disilanylenebithienylene)] derivatives. The starlike molecules with extended arms to four directions were prepared by the reaction of 1,2,4,5-tetrakis(fluorodimethylsilyl)benzene used as a core, with lithio[oligo(disilanylenebithienylene)]s. UV-Vis absorption and fluorescence properties of these starlike molecules have been investigated in a dioxane solution. The present molecules showed absorption maxima in a range of 321-337 nm, and revealed higher fluorescence quantum yields than that of the corresponding linear polymer, poly[(tetraethyldisilanylene)bithiophene].     

Structural,electronic, and optical properties of some new dithienosilole derivatives

Structural Chemistry - Structural, electronic, and optical properties of a series of organic semiconductors based on dithienosilole (DTS) and its derivatives were theoretically studied using...     

Synthesis of polyamines with pendant cyanoimidazole units and their electrochemical properties

The 2-(1-methyl-4,5-dicyanoimidazolyl) group was attached to poly(diallylamine) and polyethylenimine, affording polymers containing an electron-withdrawing pendant group. The key to their preparation is high reactivity of 1-methyl-2-fluoro-4,5-dicyanoimidazole (1) toward nucleophilic aromatic substitution (NAS) reactions with aliphatic amines. Cyclic voltammograms of these polymers show reduction waves at −2.6 to −2.7 V vs. Ag/Ag⁺ but no reoxidation waves, unlike those of monomeric and oligomeric model compounds, which are quasi-reversible. The cyclic voltammetry studies of oligomeric model compounds with different alkyl spacers show that the degree of quasi-reversibility decreases as dicyanoimidazoles are crowded together in a molecule, suggesting that a certain degree of chemical reaction occurs between reduced dicyanoimidazole groups. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2619–2629, 1998     

Synthesis and optical and electrochemical properties of glucose-cored ferrocenyl dendrimers

Triazole-based ferrocenyl glycoconjugates 1, 2, and 3 were synthesized by regiospecific copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) of azidoferrocenyl derivatives with glucose pentaacetylide. Higher generation ferrocenyl glycoconjugates form the stable ferrocenium cation and exhibit increased light harvesting property as revealed from cyclic voltammogram studies and ultraviolet–visible spectrum respectively due to the presence of more ferrocenyl and triazolyl units than the lower generation dendrimer.     

Synthesis and optical and electrochemical properties of core-fluorinated perylene bisimides

[reaction: see text] A series of bay position difluoro- or tetrafluoro-substituted perylene bisimides have been synthesized by nucleophilic halogen exchange reaction of the corresponding dibromo- and tetrachloro-substituted perylene bisimides, respectively, with potassium fluoride. Compared to the parent unsubstituted perylene bisimides, these compounds display hypsochromically shifted absorption and fluorescence spectra with fluorescence quantum yields up to unity enabling bright yellow emission. Their electrochemical properties and crystal structures of two perylene bisimides are also reported.     

Synthesis and properties of axially-phenoxycyclotriphosphazenyl substituted silicon phthalocyanine

An hydroxyl substituted hexa(phenoxy)cyclotriphosphazene (3) is reacted with silicon phthalocyanine (4), SiPc(Cl)₂, to give an axially-disubstituted phenoxycyclotriphosphazenyl silicon phthalocyanine (5). In this study, an axially phosphazene substituted phthalocyanine complex synthesized at the first time. Newly synthesized silicon phthalocyanine complex has been fully characterized by elemental analysis, ESI mass spectrometry, FT-IR, ¹H, ¹³C and ³¹P NMR spectroscopy. Photophysical (fluorescence quantum yield and lifetime) and photochemical (singlet oxygen generation and photodegradation quantum yield) properties of complex 5 are reported in DMSO. The fluorescence quenching behaviour of this complex by 1,4-benzoquinone (BQ) is also reported in DMSO.     

二茂铁基双酰肼化合物的制备及电化学性质

以二茂铁衍生物为原料合成了3个二茂铁基双酰肼类化合物(1,2,3);利用元素分析、红外光谱、核磁共振谱等分析了标题化合物的组成和结构,采用分光光度计测定了其紫外吸收光谱,利用循环伏安法测定了其电化学性质;并利用量子化学计算得到了1的稳定结构.结果表明,化合物1因酰基活性基团被氧化而在高电位区出现一个不可逆氧化峰;与此同时,其在低电位区出现一个不可逆的还原峰.     

Synthesis of tungsten carbide nanocrystals and their electrochemical properties

Tungsten carbide (WC) nanocrystals have been prepared by a solvothermal method with Mg as the reductant and WO₃ and anhydrous ethanol as the precursors. The effects of time and temperature on the synthesis of WC were investigated and a probable formation mechanism was discussed. The obtained WC nanocrystals were characterized by X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy and electrochemical methods. Hexagonal closepacked WC was successfully synthesized when the temperature was as low as 500°C. The content of carbon was more than that of W, indicating that the composition of the treated sample was C and WC only. The diameters of WC nanocrystals were ranged from 40 nm to 70 nm and the nanocrystals were dispersed on carbon films. The electrochemical measurements reveal that WC nanocrystals obviously promote Pt/C electrocatalytic ability for the oxygen reduction reaction. __________ Translated from Chinese Journal of Catalysis, 2008, 29(7) (in Chinese)     

Synthesis and characterization of chiral mono N-heterocyclic carbene-substituted rhodium complexes and their catalytic properties in hydrosilylation reactions

Different chiral mono-substituted N-heterocyclic carbene complexes of rhodium were prepared, starting from [Rh(COD)Cl]₂ (COD = cyclooctadiene) by addition of free N-heterocyclic carbenes (NHC), or an in-situ deprotonation of the corresponding iminium salt. All new complexes were characterized by spectroscopy methods. In addition, the structures of chloro(η⁴-1,5-cyclooctadiene)(1,3-di-[(1R,2R,3R,5S)-2,6,6-trimethylbicyclo[3.1.1]hept-3-yl] imidazolin-2-ylidene)rhodium(I) (5a), chloro(η⁴-1,5-cyclooctadiene)(1,3-di-[(1R,2S,5R)-2-isopropyl-5-menthylcyclohex-1-yl]imidazol-2-ylidene)rhodium(I) (5b) and chloro(η⁴-1,5-cyclooctadiene)(1,3-di-[(2R,4S,5S)-2-methyl-4-phenyl-1,3-dioxacyclohex-5-yl]imidazolin-2-ylidene)rhodium(I) (5i) were analyzed by DFT-calculations. The enantioselective hydrosilylation of acetophenone, ethylpyruvate and n-propylpyruvate with diphenylsilane and hydrolysis was carried out with chiral C₂-symmetrical mono-substituted N-heterocyclic carbene rhodium complexes giving for the first time an enantioselective excess of up to 74% ee in the case of the n-propylpyruvate.     

Highly selective synthesis of triptycene o-quinone derivatives and their optical and electrochemical properties

A convenient and efficient method for the selective synthesis of a series of triptycene o-quinone derivatives is described. The triptycene o-quinones, especially the ones containing the methoxy group(s) (electron donor) and the o-quinone group(s) (electron acceptor) simultaneously, show interesting intramolecular CT interactions and electrochemical properties. Moreover, DFT calculations display that introducing a strong electron-donor group into triptycene o-quinone results in an increasing of the HOMO energy level, which subsequently decreases the HOMO-LUMO energy gap.     

Synthesis and electrochemical properties of dendrimers containing meta-terphenyl peripheral groups and a 4,4′-bipyridinium core

Fréchet-type poly(arylether) dendrons carrying m-terphenyl peripheral groups were synthesized up to second generation by convergent methodology. Simple quarternisation of 4,4′-bipyridine with the dendritic bromides afforded the corresponding dendrimers containing a 4,4′-bipyridine core. The electrochemical parameters were obtained for all the dendrimers and the half-wave potentials of both the first and second redox processes shift to less-negative values as the dendrimer generation increases.     

核-壳结构CdSe/ZnS量子点的制备、硫醇修饰及其光学性能

采用高温有机相包覆技术制备了CdSe/ZnS核壳结构量子点材料,考察了包覆量对量子点材料的光学性能的影响,研究了含脂肪链和芳香基的双硫醇分子1,4-苯二甲硫醇和1,8-辛二硫醇对于具有核-壳结构的CdSe/ZnS量子点材料的修饰作用,考察了修饰作用对于量子点的量子效率和荧光强度等光学性能的影响.实验结果表明:随着硫化锌包覆量的增加,量子点的量子效率及其荧光发射强度明显提高;硫醇的修饰能显著增强量子点的发光强度,随着硫醇浓度的增加,其发光性能增强,但是达到一定程度后,光学性能基本不随硫醇浓度的变化而变化.根据固体核磁共振等实验结果推测:硫醇分子可能部分替代了量子点体系中的正三辛基氧膦配体,稳定了量子点体系,对量子点起修饰保护作用,从而提高了量子点的光学性能.     

Synthesis of picolinohydrazides and their evaluation as ligands in the zinc-catalyzed hydrosilylation of ketones

A set of picolinohydrazides was prepared by reaction between hydrazines and either 2-picolinic acid or ethyl pyridine-2-carboxylate, and characterized. These molecules were evaluated as ligands in the zinc-catalyzed hydrosilylation of ketones. Thus, several aromatic and aliphatic ketones were successfully reduced by diethoxymethylsilane as the hydride source in the presence of a catalytic system made of diethylzinc combined in situ to the picolinohydrazides described herein.     

Synthesis and characterization of electrospun PVdF-HFP/silane-functionalized ZrO2 hybrid nanofiber electrolyte with enhanced optical and electrochemical properties

A facile method to produce a hybrid of organic-inorganic nanofiber electrolyte via electrospinning is hereby presented. The incorporation of functionalized zirconium oxide (ZrO₂) nanoparticles into poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) and complexed with lithium trifluoromethanesulfonate (LiCF₃SO₃) provided an enhanced optical transmissivity and ionic conductivity. The dependence of the nanofiber's morphology, optical and electrochemical properties on the various ZrO₂ loading was studied. Results show that while nanofiller content was increased, the diameter of the nanofibers was reduced. The improved bulk ionic conductivity of the nanofiber electrolyte was at 1.96 × 10⁻⁵ S cm⁻¹. Owing to the enhanced dispersibility of the 3-(trimethoxysilyl)propyl methacrylate (MPS) functionalized ZrO₂, the optical transmissivity of the nanofiber electrolyte was improved significantly. This new nanofiber composite electrolyte membrane with further development has the potential to be next generation electrolyte for energy efficient windows like electrochromic devices.     

Synthesis of oligomers having a pendant dithienosilole unit and their applications to EL device materials

Oligomers bearing dithienosilole as a pendent were prepared by radical polymerization of the corresponding dithienosilole monomer using AIBN as an initiator. The resulting oligomers exhibited high solubility in common organic solvents and strong photofluorescences (Φ = 0.72-0.76) in THF which are a little higher than that of monomeric dithienosilole DTS(TMS)₂. Applications of the oligomers to EL devices as hole transporting materials were examined and the maximum electroluminance of 2140 cd/m² was obtained from a device composed of ITO/oligomer/Alq₃/Mg-Ag.