水杨醛缩对乙酰基苯胺希夫碱的合成及其荧光性质的理论研究

以水杨醛和对乙酰基苯胺为原料,首次采用绿色环保的室温固相反应方法制备了水杨醛缩对乙酰基苯胺希夫碱,用元素分析和核磁共振氢谱对产物进行了表征。测定了产物的紫外光谱、荧光光谱和相对荧光量子效率,发现该化合物具有较强的荧光性质。利用密度泛函理论(density functional theory, DFT)方法,在B3LYP/6-311G基组水平上优化了该化合物的基态分子构型。采用相同的方法和基组计算了标题化合物的振动频率,频率数据中没有虚频,即该优化构型是稳定的。分析理论计算结果发现：标题分子具有较强的芳香性和较大共轭体系。在基态优化结构的基础上应用含时密度泛函理论(TD-DFT),在B3LYP/6-31G水平上计算并研究了此化合物的吸收光谱。用单激发组态相互作用(CIS)方法优化了标题分子的激发态构型,并在此基础上用TD-DFT//B3LYP/6-31G方法计算了这种化合物的荧光发射光谱。将理论计算的光谱性质与实验的光谱数据相比较发现二者吻合较好。分析探讨了化合物分子的结构与其荧光性质之间的关系,为进一步寻找具有荧光性质的化合物提供了理论指导。     

苋菜红分子基态和激发态结构与光谱性质的量子化学研究

应用英国Edinburgh FLS920P光谱仪对苋菜红的吸收光谱和荧光光谱进行了实验检测．同时,分别采用密度泛函理论（DFT）和含时密度泛函理论（TD-DFT）对苋菜红分子的基态和激发态构型进行优化,经振动分析合理后,比较这两种能态下分子结构的差异,并对其前线分子轨道和发光机制进行了分析．在此基础上,选用6种泛函并结合溶剂化模型（PCM）在6-311++G(d, p)水平上分别计算苋菜红的吸收光谱和荧光光谱．计算结果表明：苋菜红含有分子内氢键,基态结构非平面,两个萘环所在平面有一定的夹角,激发态时两个萘环共平面;CAM-B3LYP泛函得到光谱的理论值与实验结果基本吻合;421 nm处的荧光峰值波长对应的轨道跃迁为LUMO→HOMO-1．     

基于α-肉桂酰环乙烯酮二硫缩酮的一类新型D-A有机发光材料的理论

用密度泛函理论B3LYP方法对四种新型D-π-A分子(PKD,NKD,TKD和CKD)进行基态几何构型全优化,计算分子的电离势IP和电子亲和势EA等相关能量。用含时密度泛函(TDDFT)方法计算吸收光谱,用单组态相互作用方法(CIS)优化四种化合物分子的S₁激发态结构,分析其能量与发射光谱的关系。根据化合物组成的不同恰当地选择泛函计算分子的发射光谱,并与实验结果对照表明,计算结果比较可靠。     

苋菜红分子基态和激发态结构与光谱性质的量子化学研究

应用英国Edinburgh FLS920P光谱仪对苋菜红的吸收光谱和荧光光谱进行了实验检测.同时,分别采用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)对苋菜红分子的基态和激发态构型进行优化,经振动分析合理后,比较这两种能态下分子结构的差异,并对其前线分子轨道和发光机制进行了分析.在此基础上,选用6种泛函并结合溶剂化模型(PCM)在6-311++G(d,p)水平上分别计算苋菜红的吸收光谱和荧光光谱.计算结果表明:苋菜红含有分子内氢键,基态结构非平面,两个萘环所在平面有一定的夹角,激发态时两个萘环共平面;CAM-B3LYP泛函得到光谱的理论值与实验结果基本吻合;421 nm处的荧光峰值波长对应的轨道跃迁为LUMO→HOMO-1.     

几种2-取代-4,5-双(α-呋喃基)噁唑的结构与光谱性质

在密度泛函DFT-B3LYP/6-31+G水平上对2-甲基-4,5-双(α-呋喃基)噁唑(化合物A)、2-苯基-4,5-双(α-呋喃基)噁唑(化合物B)、2-α-呋喃基-4,5-双(α-呋喃基)噁唑(化合物C)和2-α-呋喃乙烯基-4,5-双(α-呋喃基)噁唑(化合物D)S0基态进行构型优化,并用单取代组态相互作用方法(CIS)优化其S1激发态结构。从理论上探讨了A,B,C和D四种化合物的前线分子轨道能量、吸收和发射光谱等性质与结构的关系,并与实验值进行了对比,发现理论计算数据能够与实验结果一致,特别是采用纯密度泛函DFT-OLYP方法计算发射光谱时,理论计算数据与实验结果相差比混合密度泛函DFT-B3LYP方法更小。计算结果表明,分子共轭体系越大,前线轨道间能隙越小,吸收光谱红移越显著。     

硝酸丙酯结构、振动频率和热力学性质的密度泛函理论研究

用密度泛函理论(DFT)研究硝酸丙酯化合物的分子结构、振动光谱和热力学等基本性质.取BLYP、B3LYP方法和6-31G*、6-31G**、6-311G*、6-311G**基组,对硝酸丙酯分子的几何构型进行全优化计算并分析其电子结构性质.和考虑了二级相关能校正的MP2/6-311G*计算结果比较表明,B3LYP/6-31G*是研究许多较大体系化合物卓有成效和颇有前途的方法.在B3LYP/6-31G*的水平上对优化后的结构进行了正则振动频率分析,用因子0.95校正后的振动光谱和实验结果比较,符合较好.进一步     

含苯丙氨酸席夫碱结构姜黄素衍生物的量化模拟

采用量子化学密度泛函理论在B3LYP/6-311G**水平对标题化合物可能存在的A、B、C三类互变异构体进行全优化,采用AIM 2000程序包计算了分子内氢键及相应的成键临界点电荷密度和关键原子的电荷;在计算的基础上,分析了异构体几何构型、相对稳定性和电荷分布,讨论分子内质子转移的难易程度. 采用含时密度泛函理论在相同水平上对其进行了电子吸收光谱研究. 为模拟真实条件,计算还考虑了水溶液对电子结构和光谱性质的影响. 研究结果表明：烯胺式B为最稳定结构,三个异构体稳定性为BAC. A、B、C的λmax均来源于     

B2H6分子结构和振动频率的DFT研究

用密度泛函理论(DFT)方法研究B2H6分子的几何结构、空间电子密度分布和轨道动量分布以及振动频率等基本性质.取DFT理论中的B3LYP方法和6-311++G* *基组对乙硼烷分子的几何构型进行全优化计算后分析其空间电子密度分布.利用不同方法和基组得到了轨道动量分布.在B3LYP/6-311++G* *基础上对优化后的结构进行正则振动频率分析.     

含苯丙氨酸席夫碱结构姜黄素衍生物的量化模拟

采用量子化学密度泛函理论在B3LYP/6-311G**水平对标题化合物可能存在的A、B、C三类互变异构体进行全优化，采用AIM 2000程序包计算了分子内氢键及相应的成键临界点电荷密度和关键原子的电荷；在计算的基础上，分析了异构体几何构型、相对稳定性和电荷分布，讨论分子内质子转移的难易程度. 采用含时密度泛函理论在相同水平上对其进行了电子吸收光谱研究. 为模拟真实条件，计算还考虑了水溶液对电子结构和光谱性质的影响. 研究结果表明：烯胺式B为最稳定结构，三个异构体稳定性为BAC. A、B、C的λmax均来源于     

ZnqCl2及其衍生物的电子光谱性质的含时密度泛函理论研究

采用从头算法(abinitio)和密度泛函理论(DFTB3LYP)方法,对二氯取代的八羟基喹啉锌(ZnqCl2)及其2种衍生物的基态结构进行优化,同时用abinitioHF单激发组态相互作用(CIS)法在6-31G(d)基组上优化其最低激发单重态几何结构,用含时密度泛函理论(TD-DFT/B3LYP)及6-31G(d)基组计算吸收和发射光谱。计算表明,该类物质电子在基态与激发态间的跃迁,主要是在配体8-羟基喹啉(q)环内的电荷转移,电子从含O的苯酚环转移至含N的吡啶环上,发射光谱的计算值与实验值基本符合。该类化合物的电子亲和能较大,都是优良的电子传输材料,改变中心金属原子对配合物光谱性质影响不大。     

Experimental and quantum chemical calculational studies on 2-[(4-propylphenylimino)methyl]-4-nitrophenol

The Schiff base compound 2-[(4-propylphenylimino)methyl]-4-nitrophenol has been synthesized and characterized by IR, UV–Vis, and X-ray single-crystal determination. The molecular geometry from X-ray determination of the title compound in the ground state has been compared using the Hartree–Fock (HF) and density functional theory (DFT) with the 6-31G(d) basis set. The calculated results show that the DFT and HF can well reproduce the structure of the title compound. The energetic behaviour of the title compound in solvent media was examined using the B3LYP method with the 6-31G(d) basis set by applying the Onsager and the polarizable continuum model (PCM). The results obtained with these methods reveal that the PCM method provides a more stable structure than Onsager's method. Using the TD-DFT method, electronic absorption spectra of the title compound have been predicted and good agreement with the TD-DFT method and the experimental determination was found. The predicted nonlinear optical properties of the title compound are much greater than those of urea. In addition, DFT calculations of the molecular electrostatic potential and NBO analysis of the title compound were carried out at the B3LYP/6-31G(d) level of theory.     

Molecular structure,NMR and vibrational spectral analysis of 2,4‐difluorophenol by ab initio HF and density functional theory

Quantum chemical calculations of energies, geometries and vibrational wavenumbers of 2,4‐difluorophenol (2,4‐DFP) were carried out by using ab initio HF and density functional theory (DFT/B3LYP) methods with 6‐311G(d,p) as basis set. The optimized geometrical parameters obtained by HF and DFT calculations are in good agreement with related molecules. The best level of theory in order to reproduce the experimental wavenumbers is the B3LYP method with the 6‐311G(d,p) basis set. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. A detailed interpretation of the infrared and Raman spectra of 2,4‐DFP is also reported. The entropy of the title compound was also performed at HF/6‐311G(d,p) and B3LYP/6‐311G(d,p) levels of theory. The isotropic chemical shift computed by ¹H, ¹³C NMR analyses also shows good agreement with experimental observations. The theoretical spectrograms for FT‐IR and FT‐Raman spectra of the title molecule have been constructed. Copyright © 2009 John Wiley & Sons, Ltd.     

Molecular structure,spectroscopic (FT-IR and UV-Vis) and DFT quantum-chemical studies on 2-[(2,4-Dimethylphenyl)iminomethyl]-6-methylphenol

Density functional calculations of the structure, vibrational spectra, molecular electrostatic potential and thermodynamic functions have been performed at the B3LYP/6-311++G(d,p) level of theory for the Schiff base compound 2-[(2,4-Dimethylphenyl)iminomethyl]-6-methylphenol. Experimental and theoretical Fourier transform infrared (FT-IR) studies of the title compound show the preference of enol form, as supported by X-ray analysis results. Using the time-dependent density functional theory (TD-DFT) method, electronic absorption spectra of the compound have been predicted and a good agreement is determined with the experimental ones. To investigate the tautomeric stability, optimisation calculations at B3LYP/6-311++G(d,p) level were performed for the enol and keto forms of the title compound. Calculated results show that its enol form is more stable than that of the keto form. The predicted non-linear optical properties of the title compound are much greater than those of urea. The changes in thermodynamic properties for the formation of the title compound with the temperature ranging from 200 K to 500 K have been obtained using the statistical thermodynamic method. At 298.15 K the change of Gibbs free energy for the formation reaction of the title compound is 37.03 kJ/mol. The title compound cannot be spontaneously produced from the isolated monomers at room temperature. The tautomeric equilibrium constant is also computed as 1.23×10^?3 at 298.15 K for enol ? keto tautomerisation of the title compound.     

4,6-二甲氧基-2-嘧啶氨基甲酸甲酯分子结构与光谱

运用密度泛函理论B3LYP方法,6-311G*和6-311 G*基函数对4,6-二甲氧基-2-嘧啶氨基甲酸甲酯分子结构与光谱性质进行理论研究,得到分子的平衡结构参数和最大吸收波长.4,6-二甲氧基-2-嘧啶氨基甲酸甲酯分子具有Cs对称性和较大的前线轨道能隙值.基函数对计算结果无影响.     

基于密度泛函的甲醇和乙醇荧光特性研究

使用英国爱丁堡FLS920P荧光光谱仪,对甲醇、乙醇的紫外吸收光谱和荧光光谱进行实验检测,得到二者的光谱特征参数。分别采用密度泛函理论(DFT)和单激发组态相互作用(CIS)对二者分子的基态和激发态结构进行优化,并比较两种分子在不同能态下的差异。应用含时密度泛函理论(TD-DFT)的不同泛函结合极化连续介质模型(PCM)在6-31++G(d, p)水平上分别计算了二者的紫外吸收光谱和荧光光谱,与实验结果吻合。分析了甲醇、乙醇荧光产生机理,同时分析了不同泛函对于计算光谱的影响。结果表明：甲醇、乙醇在紫外波段有微弱吸收,在紫外激发下能产生拉曼峰和微弱的荧光峰。甲醇、乙醇的吸收光谱是由里德堡激发产生,产生荧光的轨道跃迁为σ*→π*。泛函OLYP能够较好地重现实验吸收能,而泛函MPWK能够较好地重现实验发射能,并且发现不同的纯泛函计算跃迁能也具有差异性。结果可为醇类分子的分子特性研究提供参考。     

Opto-electronic properties of low band gap fused-ring thieno[3,4-b]pyrazine analogues – A theoretical study

The structural, optical and ionic properties of thieno[3,4-b]pyrazine (TP) analogues have been studied using quantum chemical methods. The density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods were employed to optimise the ground- and excited-state geometries of TP analogues. Based on the ground- and excited-state geometries, the absorption and emission spectra have been calculated by using TD-DFT method with 6-311G(d,p) basis set. All the calculations were carried out in gas phase and in acetonitrile and chloroform medium. The solvent-phase calculations were performed using the polarisable continuum model (PCM). It has been observed that the effect of medium on the calculated absorption and emission spectra of these analogues is negligible. The calculated absorption and emission spectra are in good agreement with the available experimental results. This theoretical investigation shows that the fused-ring thieno[3,4-b]pyrazine analogues dibenzo[f,h]thieno[3,4-b]quinoxalines and thieno[3′,4′:5,6]pyrazino[2,3-f][1,10] phenanthroline have lower band gap than the thieno[3,4-b]pyrazine. Hence, these analogues can be used for the production of low band gap conjugated polymers.     

Structural,Spectroscopic, Antimicrobial Activity and DFT Studies on 4-Methyl-<Emphasis Type="Italic">N</Emphasis>-(4-methylphenylsulfonyl)-<Emphasis Type="Italic">N</Emphasis>-phenylbenzenesulfonamide

This study reports the structural characterization of a disulfonimide derivative, 4-methyl-N-(4-methylphenylsulfonyl)-N-phenylbenzenesulfonamide (MPBSA), using spectroscopic and quantum chemical methods. The molecule was characterized with FT-IR, ¹H ¹³C NMR and UV-Vis spectroscopies. Quantum chemical calculations of molecular geometry, vibrational wavenumbers and gauge including atomic orbital (GIAO) ¹H and ¹³C-NMR chemical shifts of the compound were carried out by using density functional method (DFT) at B3LYP/6?311++G(d,p) level of theory. Electronic absorption spectra of the compound have been computed using the time-dependent density functional theory (TD-DFT) method at the same level. A satisfactory consistency between the experimental and theoretical findings was obtained. The antimicrobial activity screening of the compound was performed on some bacteria and fungus species using microdilution method. The results showed that the title molecule have noteworthy antibacterial and antifungal activities.     

DFT simulations and vibrational analysis of FTIR and FT‐Raman spectra of 2‐amino‐4,6‐dihydroxypyrimidine

This work deals with the vibrational spectroscopy of 2‐amino‐4,6‐dihydroxy pyrimidine (ADHP) by means of quantum chemical calculations. The mid‐ and far FTIR and FT‐Raman spectra were measured in the condensed state. The fundamental vibrational wavenumbers and intensity of vibrational bands were evaluated using density functional theory (DFT) with the standard B3LYP/6‐311 + G** methods and basis set combinations, and were scaled using various scale factors, which yielded good agreement between the observed and calculated wavenumbers. The vibrational spectra were interpreted with the aid of normal coordinate analysis based on the scaled density functional force field. The results of the calculations were applied to simulate the infrared and Raman spectra of the title compound, which showed excellent agreement with the observed spectra. Copyright © 2008 John Wiley & Sons, Ltd.     

咪唑[4, 5-f] 1, 10-邻菲罗啉及其2-取代芳基衍生物的电子结构与光谱性质

分别采用B3LYP/6-31G(d)和CIS/6-31G(d)方法对咪唑[4, 5-f] 1, 10-邻菲罗啉(ip)及其8种2-取代芳基衍生物的基态(S0)和单重激发态(S1)的几何构型进行了全优化, 并采用含时的度泛函理论(TD-DFT)计算了上述化合物的电子吸收和电子发射光谱. 分析了取代基对咪唑[4, 5-f] 1, 10-邻菲罗啉的电子结构、前线分子轨道、电离势Ip、电子亲和势EA及电子光谱的影响. 计算结果表明, 取代基使8种取代衍生物前线分子轨道(LUMO-HOMO)能隙降低,导致其最大吸收和发射波长均发生了红移. 化合物1～8的跃迁类型均为分子内电荷转移（ICT）跃迁,且1～4和5～8的电子转移方向刚好相反. 溶剂对其电子光谱也有影响, 振子强度增大, 最大发射波长红移. 另外, 8种取代衍生物的电离势降低, 电子亲和势增大, 化合物1~4易于空穴的注入, 5~8易于电子的注入.