环上双氟取代三联苯类液晶化合物的量子化学研究

运用AM1和PM3两种SCF-MO方法,通过能量梯度全优化计算,给出了对环上双氟取代三联苯类液晶化合物的稳定几何构型、电子结构和生成热、偶极矩、前线分子轨道能级等分子的基本性质.联系有机结构理论进行了分析和讨论.初步阐明了其分子结构与介电各向异性之间的关系,为设计和开发新型液晶分子提供了有较大价值的线索.     

1-苯基-4 -乙基( 2′-对取代苯基 )环己硅烷类液晶化合物的量子化学研究

运用AM1和PM3两种SCF-MO方法,通过能量梯度全优化计算,给出4种1-苯基-4-乙基(2′-对取代苯基)环已硅烷类液晶化合物的稳定几何构型,电子结构和分子的基本性质(生成热,偶极矩等),联系有机电子结构理论进行了细致的讨论。     

溴代作用对竹红菌乙素分子性质影响的量子化学研究

用半经验量子化学方法ＡＭ１和ＰＭ３对竹红菌乙素及其溴代物进行了对比计算,考究了溴代作用对竹红菌乙素分子性质的影响,两种方法所得结果的均表明,溴代作用使分子的生成热、前线轨道能级及偶极矩等参数都有所降低,溴代作用也影响了竹红菌乙素分子内氢健的性质,并能使其对光的吸收产生红移。『     

新型含氧亚甲基和亚胺桥键液晶化合物分子结构与光谱的密度泛函理论研究

采用密度泛函理论方法在B3LYP/6-31G*水平上对6个新型含氧亚甲基和亚胺桥键液晶化合物分子的几何结构进行优化计算,讨论了取代基H,CH3,CH3O,C2H5O,NO2,Cl对分子电荷、前线轨道能量和电子吸收光谱等性质的影响.在此基础上使用含时密度泛函理论方法计算了分子第一激发态的电子垂直跃迁能,得到最大吸收波长λmax.计算表明,取代基的引入导致最大吸收波长红移.     

手性二氢呋喃衍生物C21H21NO3的结构和性能的理论研究

用分子动力学模拟退火找出手性环丙烷螺环化合物（Ｃ２１Ｈ２１ＮＯ３）的最低能量构型后,用半经验量子化学方法ＡＭ１、ＰＭ３优化了该化合物的构型,优化计算所得的结构参数与Ｘ射线晶体测定结果基本一致,并对其进行了振动分析,指动分析,指认了该化合物各类型振 红外特征吸收峰。在此基础上用同样方法即分动力学、ＡＭ１、ＰＭ３预测了合成手性环丙烷螺环化验事物时伴随产生手性二氢呋喃衍生物（Ｃ２１Ｈ２１ＮＯ３）的结构参     

羟基四苯咪唑衍生物的空穴和电子传输性质研究

随着有机发光二极管应用范围的扩大,对发光材料的研究逐渐增多。蓝光材料因其在色温管理和显色指数方面的重要作用,促使科学家们对效率更高、性能更好的新型蓝光材料进行了大量研究。通过（含时）密度泛函理论方法,对给电子取代基9,9-二甲基-9,10-二氢吖啶（DMAC）、三苯胺（TPA）、10H-吩噁嗪（PTZ）、10H-吩嗪（PXZ）、苯基咔唑（PCz）和5H-吲哚[3,2,1-de]吩嗪（InPz）双取代的羟基四苯咪唑分别进行了结构优化,并研究了其光物理性质。理论计算结果表明,TPA、DMAC、PTZ、PXZ和InPz取代的羟基四苯咪唑可作为空穴传输材料,PTZ、PXZ和InPz取代的羟基四苯咪唑可作为电子传输材料。     

液晶冠醚4—（烯丙基氧）—4′—（4′—羧基苯并—15—冠—5）联苯的变温红外光谱和拉曼光谱研究

本文用红外光谱法和激光拉曼光谱法研究了液晶冠醚４一（烯丙基氧）一４′一（４′一羧基苯并一１５一冠一５）联苯在升温时从结晶态到液晶态再到各向同住的液态相转变过程中红外光谱和拉曼光谱的变化。对该液晶冠醚的红外和拉曼特征频串进行了初步的经验式归属，并以频率位移、相对强度及峰形的变化描述了该化合物的相转变并初步讨论了相转变过程中光谱信息与分子结构的关系。     

3∶29型Gd_3(Fe_(1-x)Co_x)_(29-y)Cr_y化合物的成相与结构

通过X射线衍射分析和磁测量研究了Gd-Fe-Co-Cr四元系中对应于化学式Gd3(Fe,Co,Cr)29且Gd含量为一定值的截面内富Fe,Co区的相关系,重点探索了高Co含量3∶29型化合物合成的可能性,研究了3∶29型Gd3(Fe1-xCox)29-yCry化合物的结构与磁性.研究结果表明,获得3∶29型单相Gd3(Fe1-xCox)29-yCry化合物的范围为：y=5,0≤x≤0.7;y=5.5,0.7≤x≤0.8和y=6,0.8≤x≤0.9.基于对Gd3(Fe1-xCox)29-yCry化合物成相条件的研究,成功地合成了纯Co基Gd3Co29-yCry化合物,其固溶范围为6.5≤y≤7.3.3∶29型单相Gd3(Fe1-xCox)29-yCry化合物的晶体结构都属于单斜晶系,Nd3(Fe,Ti)29型结构,空间群为A2/m.得到3∶29型单相Gd3(Fe1-xCox)29-yCry化合物的固溶极限即Co含量的极大值与稳定元素Cr含量有关.Co原子的含量越高,所需稳定元素Cr的含量越大.值得注意的是,用Co原子替代Fe原子会导致Gd3(Fe1-xCox)29-yCry化合物磁晶各向异性的显著改变.当x≥0.4时,化合物的磁晶各向异性从易面型转变为易轴型.     

3∶29型Gd3(Fe1-xCox)29-yCry化合物的成相与结构

通过X射线衍射分析和磁测量研究了Gd-Fe-Co-Cr四元系中对应于化学式Gd₃(Fe,Co,Cr)₂₉且Gd含量为一定值的截面内富Fe,Co区的相关系,重点探索了高Co含量3∶29型化合物合成的可能性,研究了3∶29型Gd₃(Fe_1-xCo_x)_29-yCr_y化合物的结构与磁性.研究结果表明,获得3∶29型单相Gd₃(Fe_1-xCo_x)_29-yCr_y化合物的范围为:y=5,0≤x≤0.7;y=5.5,0.7≤x≤0.8和y=6,0.8≤x≤0.9.基于对Gd₃(Fe_1-xCo_x)_29-yCr_y化合物成相条件的研究,成功地合成了纯Co基Gd₃Co_29-yCr_y化合物,其固溶范围为6.5≤y≤7.3.3∶29型单相Gd₃(Fe_1-xCo_x)_29-yCr_y化合物的晶体结构都属于单斜晶系,Nd₃(Fe,Ti)₂₉型结构,空间群为A2m.得到3∶29型单相Gd₃(Fe_1-xCo_x)_29-yCr_y化合物的固溶极限即Co含量的极大值与稳定元素Cr含量有关.Co原子的含量越高,所需稳定元素Cr的含量越大.值得注意的是,用Co原子替代Fe原子会导致Gd₃(Fe_1-xCo_x)_29-yCr_y化合物磁晶各向异性的显著改变.当x≥0.4时,化合物的磁晶各向异性从易面型转变为易轴型 关键词： 3(Fe_1-xCo_x)_29-yCr_y化合物')" href="#">Gd₃(Fe_1-xCo_x)_29-yCr_y化合物 相关系和相结构 X射线衍射 磁晶各向异性     

碳、氮和氧族元素取代对2,1,3-苯并噻二唑衍生物的电子、光谱、电荷传输性质影响的理论研究

采用量子化学方法设计并研究了一系列CH₂、NH、O和Se取代的2,1,3-苯并噻二唑衍生物的电子性质、光谱性质和电荷传输性质．采用的研究方法是从头算Hartree-Fock和密度泛函方法．研究结果表明,中心芳环的S原子分别被CH₂、NH、O和Se取代后,母体分子的电子性质、光谱性质以及电荷传输性质得到了很好的调节．根据得到的理论研究结果,在2,1,3-苯并噻二唑衍生物基础上进行结构修饰得到的一系列分子可以作为有机发光二极管中的有机发光材料.     

Growth,structural, spectral and optical studies on 2,4-dinitrophenol organic single crystal

Single crystals of 2,4-dinitrophenol were grown by slow evaporation solution growth technique in room temperature. Crystallinity of the grown crystal was confirmed by powder X-ray diffraction technique. UV transmission study shows the good optical transmission in the entire visible region. The dielectric loss is very low at high frequency which shows that the crystal contains low level defects. Photoconductivity reveals the positive nature of the photocurrent in these crystals. The powder second harmonic generation test was also carried out using Q-switched Nd:YAG laser.     

The electronic structure and crystal field of RPt3Si (R=Pr, Nd, Sm) compounds

First-principles calculations based on density-functional theory (DFT) were performed on RPt₃Si (R=Pr, Nd, Sm) for the first time. The electronic density of states (DOS) and bonding properties were studied using relativistic full-potential APW plus local orbitals calculations. The crystal-field (CF) splitting was derived for NdPt₃Si and SmPt₃Si by fitting the temperature-dependent magnetic susceptibility. The starting estimate of the CF parameters for fitting procedure was obtained from first-principles calculations based on DFT.     

Growth, optical, dielectric and ESR studies on tetrathiourea mercury(II) tetrathiocyanato manganate(II): An organometallic complex NLO crystal

Single crystals of tetrathiourea mercury(II) tetrathiocyanato manganate(II); Hg(N₂H₄CS)₄Mn(SCN)₄, (TMTM) were grown by slow solvent evaporation technique. The grown crystals were confirmed by single crystal and powder X-ray diffraction analysis. The optical absorption spectrum of TMTM in a mixed solvent of acetone and water shows the near ultra-violet cut-off wavelength corresponding to the absorption maximum as 335 nm. FT-IR spectrum identifies the characteristic absorption bands of thiourea and thiocyanate in both middle and far infrared regions, which further confirm the incorporation of both the ligands in the resulting compound. The electron spin resonance spectrum of TMTM was recorded both at room temperature and −196 °C, which reveals that the Mn environment is symmetrical with respect to the NCS ligand distribution. It is also interesting to note that there is no hyperfine coupling between Mn nucleus and its free electrons at both room temperature and −196 °C. The dielectric constant as well as dielectric loss of the sample were calculated for varying frequencies under different temperatures.     

Structural, optical and dielectric studies of glycinium trifluoroacetate single crystal

An organic material glycinium trifluoroacetate (GTFA) has been re-synthesized and large single crystals have been grown by solution technique. Complete structure of GTFA has been redetermined from single crystal XRD data. FTIR confirmed the presence of various functional groups. Melting point (152.44 °C), thermal stability and specific heat were studied from TG/ DTA and DSC. In UV absorption spectra, a lower cutoff value as 220 nm and a wide band gap as 4.86 eV for GTFA were observed. The dielectric studies, dielectric constant and loss were measured at different temperatures (30-90 °C) in the frequency range 100 Hz-2 MHz.     

Studies on the electrical, linear and nonlinear optical properties of Manganese mercury thiocyanate bis-dimethyl sulfoxide, an efficient NLO crystal

Manganese mercury thiocyanate bis-dimethyl sulfoxide (MMTD), a novel organo-metallic nonlinear optical (NLO) crystal, was grown by a slow evaporation technique over a period of 30 days. The grown crystal was subjected to single crystal X-ray diffraction to determine the unit cell parameters. The optical properties of MMTD were investigated by UV-Vis-NIR, FTIR and FT-Raman spectroscopic techniques. The second harmonic generation (SHG) efficiency of the sample was measured using a Q-switched, mode-locked Nd:YAG laser and the results were compared with urea and manganese mercury thiocyanate (MMTC). The thermal parameters, such as the thermal diffusivity (α), thermal effusivity (e), thermal conductivity (k) and heat capacity (c_p) of MMTD were measured by the photopyroelectric (PPE) technique and the results are discussed. The dielectric response and mechanical properties of MMTD have also been investigated and reported.     

吩噻嗪衍生物EL材料的结构、光谱研究及量子化学计算

本文报道了吩噻嗪系列衍生物作为电致发光(EL)材料的结构表征、光谱性能及RHF/PM3系列方法的量子化学半经验计算,并比较了实验的UV-vis,IR,FL光谱与理论计算结果,所得到的理论结果与实验结果一致.从微观上分析了该系列衍生物的光谱性能,解释了它们的差异性.     

Influence of fluorination and chain length on the static dielectric properties of nematogenic bi-cyclohexyl phenyl derivatives

Effects of fluorination and chain length of six bi-cyclohexyl phenyl compounds (3ccp-f, 3ccp-ff, 3ccp-fff, 5ccp-f, 5ccp-ff, 5ccp-fff) on their physical properties have been investigated. All the compounds exhibit nematic phase over a wide range of temperatures. Molecular mechanics calculation reveals that dipole moments of the molecules increases (1.93D to 3.37D) with fluorination in both propyl- and pentyl-based systems; increment in f to ff derivatives is more than in ff to fff derivatives. However, no change in dipole moment is observed with increased chain length. In the nematic phase, average value of dielectric constant (?_avg) is less than the extrapolated values of ?_iso in isotropic phase. Increased fluorination also decreases splay elastic constant, and thus faster response is expected in triply fluorinated compounds.     

(Nd1-xErx)3Fe273Ti17化合物的结构与磁性

通过x射线衍射分析和磁性测量对(Nd1-xErx)3Fe273Ti17化合物的结构与磁性进行了研究.单相(Nd1-xErx)3Fe273Ti17化合物的成相范围为x=00—05之间，所有化合物均属于单斜晶系、Nd3(Fe,Ti)29型结构和A2/m空间群.着Er含量的增加，(Nd1-xErx)3Fe273Ti17化合物的晶胞体积、居里温度TC和5K下的饱和磁化强度Ms均单调减小，而5K下的饱和磁化强度Ms和Er含量的关系与稀释模型所描述的结果相一致.(Nd1-xErx)3Fe273Ti1 关键词： (Nd1-xErx)3Fe273Ti17化合物 磁晶各向异性 自旋重取向 磁相图