Molecular electronegativity in density functional theory (VI) --Atom-bond electronegativity equalization model

Ｒｅｃｅｎｔｌｙ,ｄｅｖｅｌｏｐｍｅｎｔａｎｄａｐｐｌｉｃａｔｉｏｎｏｆｄｅｎｓｉｔｙｆｕｎｃｔｉｏｎａｌｔｈｅｏｒｙ(ＤＦＴ)ａｒｅｑｕｉｔｅａｔｔｒａｃｔｉｖｅｔｏｓｃｉｅｎｔｉｓｔｓ’ａｔｔｅｎｔｉｏｎ.Ｔｈｅｒｅｌｅｖａｎｔｐａｐｅｒｓａｒｅｉｎｃｒｅａｓｉｎｇｖｅｒｙｑｕｉｃｋｌｙ[1—11].ＳｉｎｃｅｔｈｅｅｌｅｃｔｒｏｎｅｇａｔｉｖｉｔｙｃｏｎｃｅｐｔｗａｓｐｒｏｐｏｓｅｄｂｙＰａｕｌｉｎｇ[12]ｔｏｄｅｓｃｒｉｂｅｔｈｅｐｏｗｅｒｏｆａｎａｔｏｍｉｎａｍｏｌｅｃｕｌｅｔｏａｔｔｒａｃｔｅｌ…     

Toward a semiempirical density functional theory of chemical binding

The new ideas ofbond electronegativity andbond hardness are introduced, and a semiempirical density functional approach to the theory of molecular electronic structure and chemical binding is outlined. There result effective electronegativity equalization procedures that permit calculation of binding energies as well as partial charges. By a modelling of the bond electronegativity and bond hardness, a density functional interpretation of earlier bond charge models is established. Some numerical results are given for diatomic molecules.Dedicated to Professor J. Koutecký on the occasion of his 65th birthday     

The reactivity of silanes in free-radical reactions: Analysis in terms of the parabolic model of the transition state

Rate constants and activation energies of free-radical reactions of silanes and silyl radicals were analyzed in terms of the parabolic model of the transition state. The kinetic parameters were estimated for 16 groups of reactions of silanes and silyl radicals. These parameters were used to calculate the activation energies for 112 free-radical reactions and to estimate the dissociation energies of the Si−H bond for 21 compounds and those of the C−Cl bond for 12 substituted benzyl chlorides. Triplet repulsion, electronegativity, and radii of atoms of the reaction center of the transition state were shown to play an important role in the formation of the activation barrier. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1311–1316, July, 1998.     

Determination of the Apparent Molar Refraction and Partial Molar Volume at Infinite Dilution of Thiophene-, Pyrrole- and Furan-2-Carboxaldehyde Phenylhydrazone Derivatives in Acetonitrile at 293.15 K

High-precision densitometry and high-accuracy refractometry measurements of extremely dilute solutions of the thiophene-2- (TCPH), pyrrole-2- (PCPH) and furan-2-carboxaldehyde-phenylhydrazone (FCPH) compounds in acetonitrile have been obtained at 293.15 K. The partial molar volumes V ₂^∞ of each compound at infinite dilution were determined. The apparent molar refraction of these solutes at infinite dilution at 293.15 K has been experimentally determined within the Kohner-Geffcken-Grunwald-Haley approximation. The volumetric and refractometric results were interpreted in terms of the Pauling electronegativity and intrinsic molar volume of the heteroatom, and the aromaticity of the heterocyclic rings. The experimental results indicate that solute-solute interactions are negligible within the concentration range studied. Theoretical calculations at the DFT-B3LYP/6−311++G(3d,3p) level of molecular volumes support the interpretation that the volumetric contribution from the solute-solvent interactions to the limiting partial molar volumes of solutes are very small and thus solute molecules are isolated in this medium.     

Acidity predictions in an electron propagator approach

An alternative way to calculate vertical ionization potentials (VIP) and vertical electron affinity (VEA) is the application of Koopman's theorem, using the electron propagator theory. In the present work, the results of the application of this theorem using the electron propagator formalism have been compared with the experiment in order to validate different basis set. Using the basis set with the best performance, the acidity tendencies in some substituted acetic acid molecules have been analyzed by correlating the proton affinity (PA) with molecular electronegativity (χ) and hardness (η); these last indexes were obtained from the calculated VIP and VEA considering the finite difference approximation. The above correlations were compared with equivalent correlations using the energy of the frontier Hartree–Fock orbitals and the corresponding Kohn–Sham orbitals, which were calculated with the B3LYP‐DFT procedure. The results indicate that the electron propagator theory could be an interesting alternative to evaluate reactivity indexes, since this theory gives reliable values of VIP and VEA. It was also found that (i) the VIP values are very close to experiment, with only a 0.38% of error; (ii) acceptable results are inferred for VEA; (iii) a triple zeta quality function works quite well in these calculations, and particularly the 6‐311G(d,p) basis set is the best, as it had been reported; and (iv) using the depronation energy (DPE), good results were obtained in the correlations δDPE‐VEA and δDPE‐χ. The results tested that P3 approximation in the electron propagator approach can be a new and interesting alternative in predicting VIP, VEA, and some reactivity indexes, such as χ and η, at least for the compounds studied. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

不同分子环境中甲基的电负性研究

建立了不同分子环境中甲基中心碳原子电负性的计算模型, 计算了一些常见的CH~3-Z分子模型中甲基中心碳原子的电负性。结果表明:不同分子环境中的甲基具有不同的诱导效应参数, 该参数表现出规律性, 并可用于结构-性能的相关分析。     

Fe(0)(CO)3(Ph2Ppy)2Mn+Cln中金属-金属成键的光谱研究

本文研究了七个以反式二（二苯基膦吡啶）－三羰基铁为三齿配体的过渡金属双核配合物，将Ｊｏｒｇｅｎｓｅｎ建议的处理电荷转移光谱的方法推广处理ＭＭＣＴ跃迁，通过光学电负性的计算取得金属－金属成键的证据。由Ｒａｍａｎ光谱羰基伸缩振动频率的蓝移进一步支持这类化合物中存在金属－金属成键相互作用的推断。     

MgCl2载体对Nd(OiPr)3-nCln-HAl(i-Bu)2催化剂性能的影响

对不含ｆ 电子的过渡金属 (Ｔｉ、Ｃｏ、Ｎｉ等 )的Ｚｉｅｇｌｅｒ Ｎａｔｔａ催化剂 ,载体化是提高催化活性的一种重要方法 ,并已经取得了成功[1,2 ] 。而对具有许多独特优点[3] 的稀土Ｚｉｅｇｌｅｒ Ｎａｔｔａ催化剂的载体化 ,虽然人们也做了一些研究[4 ,5] ,并在一定程度上提高了催化效率 (约 2～ 3倍 ) ,但与高效载体催化剂相比 ,其催化效率还是比较低 ,因此有必要进行进一步探索 ,以助于寻找提高催化活性和定向性的途径。1　实验部分1 1　催化剂的制备1 1 1　ＭｇＣｌ2 载体的制备[6] 　将 2 0 0ｇＭｇＣｌ2 ·6Ｈ2 Ｏ与 5 5ｇＮ…     

氧化物碱标与Sanderson电荷分数

目前的酸碱理论中，以Lewis酸碱理论最具概念上的广泛性和本质上的深刻性．但其应用还局限于定性，为使这一方法定量化，并解决固体体系酸碱性的表征问题，miffy提出了光学碱度概念D’．对一些氧化物的光学碱度值，在理论上可由Pauling电负性进行计算，实验中通过探针离子光谱跃迁测定．但DUffy的方法还仅限于对主族氧化物体系的应用．在Pauling电负性基础上发展起来的Sanderson电负性能更好地表示化合物中原子的特征，在标度氧化物特性方面应比Pauling电负性具有更精确的意义．本文从Sanderson电负性均衡原理“咄发，由Sanderson电荷分…