Evaluation of Two- and Three-center Overlap Integrals Over Complete Orthonormal Sets of Ψ<Superscript><Emphasis Type="Italic">α</Emphasis></Superscript>-ETOs using their Addition Theorems

With the help of addition theorems for complete orthonormal sets of Ψ^α-ETOs in momentum space (α = 1,0,−1,−2,...) introduced by the author, the general expansion formulas are established for the two- and three-center overlap integrals occurring when Hartree-Fock–Roothaan and explicitly correlated methods, respectively, are employed. The relationships obtained are valid for the arbitrary quantum numbers, screening constants and location of Ψ^α-ETOs.     

Two-Dimensional Gas Chromatography. Concepts,Instrumentation, and Applications – Part 1: Fundamentals,Conventional Two-Dimensional Gas Chromatography,Selected Applications

The writer of this review published in 1978 a three-part article on two-dimensional gas chromatography in the first three issues of this journal [1]. The review was written at a time when capillary column GC was still in its infancy. Commercial columns were (essentially) unavailable and sample introduction into capillary columns was done exclusively in the split mode. Two-dimensional separations were explored in only a few laboratories. The limitations of capillary column technology made this exercise rather difficult. The introduction of fused silica capillary columns in the early eighties drastically changed the landscape in which gas chromatography was practiced. It took the chromatographic community just a few years to convert from packed columns to capillary columns. Instrumentation and accessories specifically designed for capillary column use came onto the market. This writer had great hopes that the revolution in capillary column GC would be mirrored in the development of instrumentation for Two-Dimensional Gas Chromatography. This never materialized. On the contrary, tentative steps taken by a few manufacturers and suppliers of chromatographic equipment fizzled out. It was perhaps the introduction of relatively inexpensive and user friendly GC/MS instrumentation, in combination with nearly indestructible fused silica capillary columns that took away the incentive to develop commercially viable Two-Dimensional Gas Chromatography. Much of the thinking went like this: why insist on good chromatography if mass spectrometry can do the job without the need for complete separation. Some progress in the further development of conventional Two-Dimensional Gas Chromatography has certainly been made over the last 20 years but there has not been a great deal of excitement. Applications have also been relatively sparse and they are limited to just a few areas. Science does not remain static and chromatography is no exception. Progress in gas chromatography is driven by new technology and ideas. Substantial improvements in two-dimensional GC were not forthcoming until Phillips and his research group introduced and implemented an entirely new form of Two-Dimensional Gas Chromatography, called comprehensive two-dimensional GC, or GC×GC. This breakthrough occurred only in 1991 [2]. It does take some time before scientists change attitudes and habits. There is always a time lag between the introduction of new technology and its general acceptance. The public's attitude toward comprehensive Two-Dimensional Gas Chromatography is probably no exception. The number of scientists who are actively pursuing this new branch of gas chromatography is still very small. It is often a single individual who carries the torch. J.B. Phillips' name is synonymous with comprehensive Two-Dimensional Gas Chromatography. He is not only its inventor and proponent but his fertile mind has initiated research in other related areas. Sadly, he passed away shortly before this review was written. This contribution is dedicated to his memory.     

Spectrochemical Properties of Cobalt(II) Complex with Bidentate Schiff Base in Various Solvents

As a continuation of our previous studies on copper(II) complexes with a bidentate Schiff base derived from 5-bromosalicylaldehyde and -aminopyridine, we have investigated the electronic spectra of the cobalt(II) complex with this ligand. The complex is a red crystalline compound soluble in common solvents, such as chloroform, dioxane, dimethyl formamide, dimethyl sulfoxide, and methanol. The time-elapsed spectral measurements of the complex and ligand, as well as conductivities of the complex in chloroform and dioxane solutions, are presented and discussed. Molar conductivities indicate that the complex exists as a nonelectrolyte in nonpolar solvents and as a 1:1 or 1:2 electrolyte in polar solvents. The ligand-field parameters (CFM/AOM) for the complex in chloroform solution are estimated and discussed.     

聚甲基丙烯酸(N-羟基琥珀酰亚胺)酯的簇聚诱导发光研究

不含普通发光单元的非典型生色团发光化合物因其基础研究重要性和广泛的应用前景引起了人们的极大兴趣.其中许多化合物还具有独特的聚集诱导发光（Aggregation-induced emission,AIE）特性.然而其发光机理仍然存在争议.在此前的研究中,提出了簇聚诱导发光（clustering-triggered emission,CTE）机理,即非典型生色团的簇聚和电子共享来解释这些体系的发光和AIE现象.为进一步验证这一假说,设计合成了不含传统生色团的聚甲基丙烯酸（N-羟基琥珀酰亚胺）酯（PNHSMA）.其稀溶液基本不发光,但浓溶液,纳米聚集体,固体粉末均发射蓝光,呈现出AIE性质.通过与其单体甲基丙烯酸（N-羟基琥珀酰亚胺）酯（NHSMA）的发光行为对比及单体单晶结构解析,利用CTE机理很好地解释了其光物理行为.     

On the calculation of arbitrary multielectron molecular integrals over Slater‐type orbitals using recurrence relations for overlap integrals. II. Two‐center expansion method

Using expansion formulas for the charge‐density over Slater‐type orbitals (STOs) obtained by the one of authors [I. I. Guseinov, J Mol Struct (Theochem) 1997, 417, 117] the multicenter molecular integrals with an arbitrary multielectron operator are expressed in terms of the overlap integrals with the same screening parameters of STOs and the basic multielectron two‐center Coulomb or hybrid integrals with the same operator. In the special case of two‐electron electron‐repulsion operator appearing in the Hartree–Fock–Roothaan (HFR) equations for molecules the new auxiliary functions are introduced by means of which basic two‐center Coulomb and hybrid integrals are expressed. Using recurrence relations for auxiliary functions the multicenter electron‐repulsion integrals are calculated for extremely large quantum numbers. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 117–125, 2001     

Synthesis and spectroscopic studies of highly fluorescent,solvatochromic diastereomers with differentially stacked bithiophene-substituted quinoxaline rings

Diastereomeric C-shaped molecules containing closely stacked bithiophene-substituted quinoxaline rings were synthesized and characterized by NMR, UV–vis absorption, and fluorescence spectroscopy. The unique geometry of each diastereomer resulted in different degrees of π-overlap between the bithiophene-substituted quinoxaline ring chromophores, modulating their spectroscopic properties. The donor-acceptor nature of this chromophore gave rise to its positive solvatochromism. ¹H NMR and UV–vis absorption spectroscopy confirmed the existence of π-π interactions in the ground state between the quinoxaline rings in both molecules but between the bithiophene rings only in the syn isomer. They exhibited significant emission maxima bathochromic shifts, a strong, positive solvatochromism, increased band broadening, and larger Stokes shifts when compared to a compound with an unstacked chromophore. Additionally, the syn isomer consistently showed λ_max,em value red-shifts and larger band broadening and Stokes shifts compared to the anti isomer due to the greater π-overlap in the syn isomer.     

Direct quantum chemical integral evaluation

Performing quantum chemical integral evaluation directly, without recursion and without direct coupling of angular momenta according to the rotation group is analyzed. The rotation group limits the structure of these closed‐form expressions. The result of all cross differentiation is a rotational invariant. Closed‐form expressions are obtained for the general three‐ and four‐center Gaussian integral. The solid harmonic addition formula can be used to express these integrals as sums of products of an exponent‐independent (angular) factor and a molecular‐orientation‐independent (exponential) factor in a variety of ways. The results are products of two such factors summed over the set of distinct, relevant polynomials of the exponents. The coefficients of these polynomials, angular factors, are complicated but common to all n‐center matrix elements and independent of any type of contraction. Derivatives must be obtained using the product rule. An implementation in the Solid Spherical Harmonic Gaussian (SSHG) computer code is outlined and preliminary comparison is made. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 373–383, 2001     

Calculation of bridge function coefficients via modified Mayer-samplings

Two modified Mayer-sampling methods are described based on Transition Matrix Monte Carlo (TMMC) and overlap sampling for calculating the integrated diagrams appearing in the coefficients of the bridge function; b_n (r) constructed in terms of the total correlation function h(r) for a hard-sphere system. Calculations are performed using prescribed h(r) for reduced densities at 0.2, 0.5 and 0.8 up to the third-order expansion in density. The results from these methods compared with the generic Monte Carlo Mayer-sampling are analysed in detail. It was found that the TMMC Mayer-sampling approach shows better precision over core and tail regions of b ₂(r) and b ₃(r), and the overlap sampling method shows overall improvement in the precision of the bridge coefficients. Both methods can be straightforwardly applied to calculate higher order bridge function coefficients and to any model systems with relatively simple modifications.     

定向结晶合金材料全部工程弹性常数的超声测定

采用超声脉冲回波重合法（ＰｕｌｓｅＥｃｈｏＯｖｅｒｌａｐ）对一种定向结晶耐高温合金材料进行了研究，精确测试了该材料中沿不同方向传播的超声纵波及横波的声速，计算出慢度曲线，并确定了材料的全部工程弹性常数．通过对工程弹性常数及慢度曲线对材料进行评价，为其工程应用提供重要依据     

Electronic Couplings for Singlet Oxygen Photosensitization and Its Molecular Orbital Overlap Description

The reaction of triplet fusion, also named triplet-triplet annihilation, has attracted a lot of research interests because of its wide applications in photocatalytic, solar cells, and bio-imaging. As for the singlet oxygen photosensitization, the reactive singlet oxygen species are generated through the energy transfers from photosensitizer (PS) to ground triplet oxygen molecule. In this work, we computed the electronic coupling for singlet oxygen photosensitization using the nonadiabatic coupling from the quantum chemical calculation. Then we utilized the molecular orbital (MO) overlaps to approximate it, where the MOs were computed from isolated single molecules. As demonstrated with quantitative results, this approach well describes the distribution of the coupling strength as the function of the intermolecular distance between the sensitizer and O\begin{document}$ _2 $\end{document}, providing us a simple but effective way to predict the coupling of triplet fusion reactions.