Structures, electronic states, photoluminescence, and carrier transport properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles

The excellent electroluminescent (EL) properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles, 1-methyl-1,2,3,4,5-pentaphenylsilole (MPPS), and 1,1,2,3,4,5-hexaphenylsilole (HPS) have been found. Despite some studies devoted to these materials, very little is known about the real origin of their unique EL properties. Therefore, we investigated the structures, photoluminescence (PL), and charge carrier transport properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles as well as the effect of substituents on these characteristics. The single crystals of the three siloles involving 1,1-dimethyl-2,3,4,5-tetraphenylsilole (DMTPS), MPPS, and HPS were grown and their crystal structures were determined by X-ray diffraction. Three siloles have nonplanar molecular structures. The substituents at 1,1-positions enhance the steric hindrance and have predominant influence on the twisted degree of phenyl groups at ring carbons. This nonplanar structure reduces the intermolecular interaction and the likelihood of excimer formation, and increases PL efficiency in the solid state. The silole films show high fluorescence quantum yields (75-85%), whereas their dilute solutions exhibit a faint emission. The electronic structures of the three siloles were investigated using quantum chemical calculations. The highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) are mainly localized on the silole ring and two phenyl groups at 2,5-positions in all cases, while the LUMOs have a significant orbital density at two exocyclic Si-C bonds. The extremely theoretical studies of luminescent properties were carried out. We calculated the nonradiative decay rate of the first excited state as well as the radiative one. It is found that the faint emission of DMTPS in solutions mainly results from the huge nonradiative decay rate. In solid states, molecular packing can remarkably restrict the intramolecular rotation of the peripheral side phenyl ring, which has a large contribution to the nonradiative transition process. This explains why the 1,1-disubstituted 2,3,4,5-tetraphenylsiloles in the thin films exhibit high fluorescence quantum yields. The charge carrier mobilities of the MPPS and HPS films were measured using a transient EL technique. We obtained a mobility of 2.1 x 10(-)(6) cm(2)/V.s in the MPPS film at an electric field of 1.2 x 10(6) V/cm. This mobility is comparable to that of Alq(3), which is one of the most extensively used electron transport materials in organic light-emitting diodes (LEDs), at the same electric field. The electron mobility of the HPS film is about approximately 1.5 times higher than that of the MPPS film. To the best of our knowledge, this kind of material is one of the most excellent emissive materials that possess both high charge carrier mobility and high PL efficiency in the solid states simultaneously. The excellent EL performances of MPPS and HPS are presumably ascribed to these characteristics.     

1,1-环丁烷二羧酸单、双核铜配合物的合成、晶体结构、热分析和磁性

Two new copper complexes, [Cu（cbdc）（phen）（H2O）]·2H2O （1） and [Cu2（cbdc）（phen）2（H2O）2]（ClO4）2·H2O （2） （cbdc= 1,1-cyclobutanedicarboxylate and phen= 1,10-phenanthroline）, were synthesized by reaction of cbdc with Cu（ClO4）2 and phen in ethanol aqueous solution. Complex 1 crystallizes in monoclinic system with space group P2（1）/c and a=0.9428（4） nm, b= 1.2183（5） nm, c= 1.6265（7） nm, β= 102.418（5）°, V= 1.8246（13） nm^3, Z=4, R=0.0445, wR2=0.0947. The structure of 1 is discretely mononuclear, which is packed by π…π interaction forming a 3D supramolecular structure where Cu（Ⅱ） ion is five-coordinated and has square-pyramidal coordination geometry. Its thermal decomposition procedure detail was studied by thermal analysis TG-DSC. Complex 2 belongs to monoclinic system with space group P2（1）/c and a=0.8897（3） nm, b= 1.9130（8） nm, c= 1.9936（8） nm,β=99.04（2）°, V=3.351（2） nm^3, Z=4, R=0.0540, wR2=0.1102. The structure of 2 is a discrete binucleus, where Cu（1） is four-coordinated by phen and cbdc in a square-planar geometry while Cu（2） is five-coordinated by phen, one O of cbdc and two H2O, which can be best described as distorted trigonal-bipyramidal geometry. Cu（1） and Cu（2） are linked by carboxylic group of cbdc in a bidentate bridging fashion. Variable-temperatttre magnetic susceptibilities of 2 in 2-300 K showed that its magnetic behavior obeyed Curie law.     

Liquid chromatographic resolution of beta-amino acids on CSPs based on optically active (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6

Two chiral stationary phases (CSPs) based on optically active (3,3′-diphenyl-1,1′-binaphthyl)-20-crown-6 covalently bonded to silica gel were utilized for the first time for the resolution of racemic β-amino acids using high performance liquid chromatography. All of the 10 β-amino acids tested were resolved on the CSP containing residual silanol-protecting n-octyl groups, while only five β-amino acids were resolved on the CSP containing residual silanol groups. The superiority of the CSP containing residual silanol-protecting n-octyl groups and the characteristic retention behaviors of the two enantiomers on the CSP were rationalized to stem from the removal of the residual silanol groups, which can otherwise induce the non-enantioselective retention of the analytes, and the improved lipophilicity of the CSP. The elution orders of the two enantiomers of β-amino acids were identical on the two CSPs and, consequently, it was concluded that the two CSPs were concluded to utilize identical chiral recognition mechanisms. The different elution orders of the analytes were proposed to be attributed to the presence or absence of π-π interactions between the CSP and analytes.     

Synthesis, Crystal Structure and Theoretical Calculation of 1,1',5,5'-Tetramethyl-2,2'-diphenyl-4,4'-[i-phenylene-bis(methylidynenitrilo)] di-1H-pyrazol-3(2H)-one

1,1',5,5'-Tetramethy1-2,2'-diphenyl-4,4'-[i-phenylenebis(methylidynenitrilo)]di1H-pyrazol-3(2H)-one was synthesized and characterized by X-ray single-crystal diffraction analysis. The crystal crystallizes in monoclinic, space group P21/c with a = 6.1375(1), b =24.6571(4), c = 17.7487(3)(A), β = 94.781(1)°, V= 2676.62(8)(A)3, C30H28N6O2, Mr= 504.58, Z = 4,Dc = 1.252 g/cm3, F(000) = 1064, μ = 0.081 mm-1, R = 0.0463 and wR = 0.1153 (I ＞ 2σ(Ⅰ)).Theoretical studies of the title compound were carried out by density functional theory (DFT) BLYP method, using ADF program package. It indicates that N(26) and N(41) are active sites of the title compound.     

两个由1,1''-环己烷二乙酸构筑的镉的配合物的合成、晶体结构和荧光性质

通过邻羧苯乙酸、1,10-邻菲啰啉及硝酸镉的溶剂热反应合成了2个配合物:[Cd(phen)(chdc)]n(1)和[Cd(phen)(chdc)(H2O)]n(2).X-射线单晶衍射显示:1是梯状双链结构;2是单链结构,单链再通过氢键连接成双链.虽然1和2的组分相似,但它们在固态条件下的荧光发射却大不一样,可能在光化学方面有潜在的应用.