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Three-center integrals over Gaussian orbital and Kohn-Sham (KS) basis sets are reviewed. An orbital basis function carries angular momentum about its atomic center. That angular momentum is created by solid harmonic differentiation with respect to the center of an s-type basis function. That differentiation can be brought outside any purely s-type integral, even nonlocal pseudopotential integrals. Thus the angular factors associated with angular momentum and differentiation with respect to atom position can be pulled outside loops over orbital and KS Gaussian exponents. Key words: Gaussian orbital, solid harmonics, molecular integrals, pseudopotential. On examine les integrales a trois centres sur des bases d'orbitales gaussiennes et de Kohn-Sham (KS). Une fonction de base (orbitale) presente un moment angulaire autour de son centre atomique. Ce moment angulaire est cree par derivation des harmoniques solides par rapport au centre d'une fonction de base de type s. Cette derivation peut etre sortie de toute integrale purement de type s, meme d'integrales portant sur des pseudopotentiels non locaux. Donc, les facteurs angulaires associes au moment angulaire et la derivation par rapport a la position de l'atome peuvent etre sortis de la boucle sur les exposants orbitalaires et KS gaussiens. [Traduit par la Redaction] Mots-cles: orbitale gaussienne, harmoniques solides, integrales moleculaires, pseudopotentiel., Introduction Sambe and Felton (SF) started the process of bringing density functional theory (DFT) to chemistry. In quantum chemistry, the molecular orbitals are expanded in a finite number of Gaussian [...]

The electronic structures of the bis(dithiolene) anions [M(mnt)(sub 2)](super n-) (M = Ni, Pd, Pt; mnt = 1,2-S(sub 2)C(sub 2)(CN)(sub 2); n = 0-2) were examined by a combination of photodetachment photoelectron spectroscopy (PES) and functional theory calculations. The combined experimental and theoretical data provide insight into the molecular orbital energy levels of [M(mnt)(sub 2)](super 2-) and the ground and excited states of [M(mnt)(sub 2)](super 1-) and [M(mnt)(sub 2)].

The description of analogies between the symmetries of the bonding molecular orbitals in octahedral cages involving p-orbital delocalization, such as B(sub 6)H(sub 6)(super 2-), and those in analogues coinage metal cages involving d-orbital delocalization. The magnetic properties reveal that the copper cages are likely to be most stable among coinage metal cages.

The potential energy hypersurfaces (PESs) of heptasulfer (S7) and of [LiS7](super +) are investigated by ab initio molecular orbital calculations at the G3X(MP2) level theory. It is shown that the S7 molecule like the related S6 and S8 species forms at least six isomers on the potential energy surface that are more stable than open-chain isomers.

A quantum chemical study is conducted to assess changes in aromaticity along the T1 state Z/E-isomerization pathways of annulenyl-substituted olefins. The minimum on the T1 potential energy surface (PES) corresponds to the olefin structure with highest substituent aromaticity for olefins with annulenyl substituents.

Potential energy surfaces for the alkaline hydrolysis of sarin and O,S-dimethyl methylphosphonothiolate, a VX model compound, and the perhydrolysis of the latter are computed at the MP2/6-31+G(d)//mPW1K/MIDI level of theory. Excellent agreement with the experimental enthalpy of activation for alkaline hydrolysis of sarin was found.

Ab initio molecular orbital theory was employed to study base-catalyzed hydrogenation, to better understand and to rationalize the limitations of the catalytic reaction. A good balance between polarity and catalyst solubility is required in selecting the optimum solvent for the base-catalyzed hydrogenation reaction.

Pd K-edge X-ray absorption near-edge spectroscopy (XANES) probes different molecular orbitals and consequently the charge distribution in a series of bidentate diphosphine ligands (PP) Pd coordinating moieties (XX) complexes. A full interpretation of the Pd K-edge XANES data is presented.

Kinetic experiments and high-level ab initio molecular orbital calculations were used to study the cumyl dithiobenzoate (CDB)-mediated reversible addition fragmentation chain-transfer (RAFT) polymerization of styrene at 30 degree Celsius. The kinetic data indicates the delayed onset of steady-state behavior.

The aromaticity of the hydrosilver(I) and hydrogold(I) analogues of aromatic hydrocarbons is verified by a number of established criteria of aromaticity, such as structural, energetic, magnetic, and chemical criteria. The comprehensive study of the structural, energetic, spectroscopic, and bonding properties of the novel classes of inorganic compounds containing bonds that are characterized by a common ring-shaped electron density, more commonly seen in organic molecules, is presented.

The electrochemical properties of 1,2, and 3 are rationalized by molecular orbital (MO) calculations using the density functional theory (DFT) method. Specifically, the molecular orbital (MO) calculation suggests that significant contribution of the metal cluster center to unoccupied molecular orbitals in 3, which is consistent with the experimental result of strong interfullerene electronic communication via the Rh6 metal cluster spacer.

Metal complex is significant for knowing its chemical reaction and its function as mediators in the reactions that take place photochemically to thoroughly understand the attitude of excited state of transition. The spin depth is importantly localized on the Pt atoms, which provide an idea about the capability of the triplet excited state to remove hydrogen and halogen atoms from organic substrates.

The novel fused Zn(II)porphyrin arrays (Tn, porphyrin tapes) have been investigated by steady-state and time-resolved spectroscopic measurements along with theoretical MO calculations. The overall relaxation dynamics of the porphyrin tapes show a systematic change as the number of porphyrin pigments increase in the array

The electronic structures of key species involved in methane hydroxylation performed by the hydroxylase component of soluble methane monoxygenase (sMMO), as proposed previously on the basis of high level density functional theory, were investigated. The molecular orbital and Mulliken spin density analyses suggest that the first electron transfer occurs between the C-H sigma-orbital and O3 orbital.

Research has been conducted on the neutral in-plane tris-homoaromaticity. The study of this homoaromaticity in tris(bismethano)benzene has been carried out and the hypothesis that the pi-orbitals might interact in the plane via the unsaturated carbon atoms has been tested and discussed.

Research has been conducted on the 2,3-cis/trans pairs of 2,3-disubstituted aziridines. The stabilities of these compounds investigated theoretically via molecular orbital calculations and the role of the functional group on the aziridine ring's nitrogen atom are discussed.

Research has been conducted on the supramolecular trimetallic complexes with ruthenium light absorbers and rhodium metal center. The effect of bridging and terminal ligands on the electrochemical and spectroscopic properties of these complexes has been investigated and discussed.

Research has been conducted on fluorocarbonyl sulfenyl chloride, methylfluorocarbonyl disulfide and bis(fluorocarbonyl) trisulfide. The photoelectron spectroscopy study of these compounds and the results of the molecular orbital analysis and ionization energy calculations are presented.

Research has been conducted on the s,p mixing and group trends in electron-rich three-center bonding. The stability of this bonding in triatomic electron anions has been investigated and the results of the perturbational molecular orbital analysis of the s,p mixing are discussed.

Research has been conducted on the nitridorhenium(V) complexes. The synthesis of these complexes, their excited states and their energy trend studied via the use of the molecular orbital analysis have been investigated and are discussed.

Research has been conducted on the penta- and hexa-coordinated silicon. The results of the ab initio molecular orbital calculations of (super)29 Si NMR chemical shifts and relative stabilities of the monocyclic and spirocyclic silicon-polyalcohol complexes are reported.

A homologous series of para-substituted phenyl octadecyl ethers (X-POEs, where X = H, Cl, Br, I) was prepared using the Williamson ether synthesis and characterized by [sup.1]H NMR and GC/MS. Scanning tunneling microscopy images acquired from these ethers revealed a bias-dependent contrast corresponding to electron density contours of various X-POE molecular orbitals. Images reflecting the electron density contour of the highest occupied molecular orbital exhibited four bright spots--one for the halogen atom, two representing the pair of lobes of the phenyl ring, and one for the oxygen/[alpha]-carbon atoms. For each X-POE, the intensities ([Z.sub.max]) of the spots for the halogen atom and the lobe of the phenyl ring closest to the halogen were measured and their ratio was calculated (Cl-POE 0.49 [+ or -] 0.06; Br-POE 0.59 [+ or -] 0.06; I-POE 0.75 [+ or -] 0.07). Analysis of variance at the 95% confidence level revealed that the intensity ratios were consistent from molecule to molecule, image to image, and day to day. According to the Student t-test, the average [Z.sub.max] ratios for Cl-POE, Br-POE, and I-POE are different at the 95% confidence level. In addition, they follow a trend that corresponds favorably with that of the atomic radii of the halogens. The probability of classifying a single X-POE molecule as Cl-POE, Br-POE, or I-POE is variable and depends on the magnitude of the [Z.sub.max] ratio.

Research describing the microscopy and spectroscopy of tetraphenylporphyrin is presented. The paper describes the use of scanning tunneling microscopy and orbital-mediated tunneling spectroscopy to study molecular orbitals of porphyrin rings.

Research has been conducted on the (super)19 F NMR chemical shifts and (super)19 F NMR shielding for alkyl fluorides from methyl fluoride to tert-butyl fluoride. The study of the shielding changes based on the molecular orbital calculations is presented.

Ab initio molecular orbital (MO) calculations are carried out for base-hydrogen fluoride (HF) complexes (base = O3 and SO2) in order to elucidate the structures and energetics of the complexes. It was seen that the harmonic vibrational frequencies calculated for cis O3-HF and cis SO2-HF complexes and the calculated rotation constants for cis SO2-HF are in good agreement with the experimental values.

C2-C7 and C2-C6 cyclization pathways of 1,2,4-heptatrien-6-ynes were studied using a density functional molecular orbital method.

The photoelectron spectrum of the dirhodium tetracarboxylate Rh2(O2CCF3)4 is reported.

Ab initio calculations of the highest occupied molecular orbitals of several guanine-containing sequences with cobalt ion and benzoyl peroxide are presented.

Ab initio molecular orbital calculations were undertaken on species linked with the bimolecular reaction of protonated methylamine with methylcalcium, forming the valence-Rydberg bonded complex.

Spatial extensions of excited states of metal complexes are discussed relative to tunability by chemical variation. The metal d and/or MLCT character of triplet states is related positively to the size of zero-field splitting (zfs). Increasing metal character changes many properties. Ligand-ligand coupling changes as does the tendency to delocalize excitation, both being more exaggerated. For the first time properties of partially and completely deuterated Pt(2-thpy)(sub.2) compounds have been studied and results have been compared with those for a perprotonated compound.

Bis(phenoxyl)metal complexes of copper(II) and zinc(II) are discussed relative to their intramolecular spin interactions. Two complexes which contain two coordinated phenoxyl ligands in cis position relative to each other are described. Electronic structures have been studied with EPR spectroscopy. Spin interactions are different from those reported for analogous bis(semiquinonato)metal complexes.

Trigonometric basis set functions can be applied to orbital symmetry and to the C-H stretching and deformation motions of benzene for undergraduate chemistry courses. It is difficult to show the form of the corresponding symmetry coordinates when dealing with the relatively simple group theoretical treatment that gives the symmetry species of the vibrational modes of a molecule and their infrared and Raman activities. Without the form of the symmetry coordinates the discussion is rather abstract. Thus a simple way to get the symmetry coordinates is valuable. The basis functions in this form can be applied to all axial groups. With a second angular variable the cubic and icosahedral groups can be covered.

The selectivity of 5'-TGGGT-3' and 5'-CGGGC-3' sequences toward photoinduced one-electron oxidation was studied experimentally and by ab initio molecular orbital computations. It was experimentally verified that G2 of 5'-TG1G2G3T-3' is more reactive than G1, while for 5'-CG1G2G3C-3' the selectivity is reversed. Also, it was concluded that the 5'-CG1G2G3-3' is unique, with high G1 selectivity, and that the radical orbitals in states of radical cations and neutral radicals of 5'-TGGG-3' and 5'-CGGG-3' are not the highest occupied molecular orbitals.

A detailed ab initio molecular orbital calculations for the mechanisms of the 1,3-migrations of group-14 element groups in HC(=O)CH2MH3 and HC(=NH)CH3SiH3 were conducted. Results indicate that the retention 1,3-silyl migration in formylmethylsilane can be best described as an intramolecular nucleophilic substitution at silicon while the corresponding migration in allylsilane is as an electrocyclic sigmatropic rearrangement controlled by subjacent orbital interactions.

High-spin polyphenoxyl with poly(1,4-phenyleneethynylene) as the basis is discussed. The first synthesis of a poly(1,4-phenyleneethynylene) bearing pendantly 2-substituted phenoxyl radicals has been carried out. Structure and high-spin state are compared to the corresponding diphenyoxyl compound.

Singlet-triplet gaps and addition of singlet carbenes to alkenes are discussed relative to hard-soft acid-base and density functional theory (DFT) analysis. Good correltation was seen between the singlet-triplet energy gap and the condensed softness for elebrophilic attack at the triplet carbene carbene. The level of carbene stability on electron donation.

Photoinduced single electron transfer in 5-aryl-1,2,4-oxadiazoles is discussed based on some mechanistic investigations into synthesis of quinazolin-4-ones in connection with study of photoinduced rearrangements of the O-N bond with 5-membered heterocycles. Photoreactivity may be exploited and a given photochemical reaction may be useful in synthetic efforts.

Synthesis, intramolecular charge transfer, and redox properties are discussed for 9-(1,2-dithiol-3-ylidene)-, 9-(1,3-dithiol-2-ylidene)-, and 9-(1,3-selenathio-2-2ylidene)fluorenes derivatives. Novel push-pull compounds of the D-pi-A type with intramolecular charge transfer have been characterized. The qualities of the heteroatom in the donor fragment do not affect the maxima of intramolecular absorption bands. Electronic absorption spectra in the ICT region and effect of donor moiety.

Reduction of 4,4'-(1,3-propanediyl)bis(N-methylpyridinium) dibromide proceeds to formation of 3,10-diaza-N,N, dimethyldispiro(5.0.5.3)-pentadeca-1,4,8,11-tetraene, which is a novel heterocyclic dispiro compound and is discussed relative to its structural and chemical properties. The experimental and theoretical perspectives are dealt with.

The ab initio molecular orbital theory was used to examine the mechanism of lithium ion migration in Li+-(diglyme)2 and LiClO4-diglyme complexes. Results revealed several local minima on the potential energy surfaces of the complexes. The migration of lithium cation from one coordination site to another were found to occur with the making or breaking of Li-O bonds even if the cation is not attached to the ClO4- anion. Results further showed that the smallest Li+ migration barriers are located between structures with the highest coordination numbers.

A two-step, high-yield synthesis of (RhCl2-(Ph)(PPh3)2) starting from RhCl3*3H2O and SbPh3 through (RhCl2(Ph)(SbPh3)3), a density functional analysis with geometry optimization of the model molecule (RhCl2(PH)(PH2CHCH2)2) and an X-ray analysis of the monoclinic crystals is described. Results demonstrate a new efficient, synthetic route to stable organometallic compounds which can serve as starting materials for various preparative strategies.

Research was conducted to examine the remarkable influence of axial pi* coordination on the Cr-Cr quadruple bond in dichromium paddlewheel complexes. The study focused on new, definitive examples that demonstrate how donation of electrons to the pi* orbitals can weaken and lengthen the Cr-Cr bond. Results indicate that the cumulative effect of donation from four nitrogen atoms is very large, which is 0.4 angstrom in the Cr-Cr distance.

Research was conducted to extend the theoretical approach toward understanding the essential features of pi-facial stereoselection based on the exterior frontier orbital extension (EFOE) model. The EFOE analysis of the imines and iminium ions of cyclohexanone and tropinone have demonstrated that the facial stereoselection of the systems is most likely to be dictated by steric effect and by the extension of LUMO. The ground-state skeletal deformation arising from the enhanced resonance effect in iminium ions was found to be most likely responsible for the changes of facial stereoselection of nucleophilic additions to the systems investigated.

Research was conducted to examine the conditions under which X-ray magnetic circular dichroism (XMCD) spectroscopy can be utilized to follow the magnetic properties of each element in paramagnetic polynuclear complexes. XMCD was used to measure the local Ni(super II) and Mn(super II) magnetization in the two paramagnetic high-spin molecules (Cr((CN)Ni(tetren))6)(ClO4)9 and (Cr((CN)Mn(TrispipcMeen))6)(ClO4)9*3THF. Results show that the use of XMCD makes it possible to compute the electronic structure of the different metallic ions in the paramagnetic polymetallic systems.

Research was conducted to examine the reactions catalyzed by the B12-dependent enzyme diol dehydratase by means of ab initio molecular orbital theory. The calculations reveal that the radical rearrangement step is largely assisted by partial protonation of the migrating hydroxyl group. The application of the partial-proton-transfer concept makes a substantial contribution to the understanding of the mechanism of action of diol dehydratase. Results confirm that the enzyme is likely to use a suitable hydrogen-bond donor to bind the migrating hydroxyl group to the substrate.

Research was conducted to examine the chirality content of molecular orbitals in general using a computational method. A further objective was to evaluate the extent of desymmetrization induced by common chiral auxiliaries used in asymmetric syntheses. Results demonstrate that the molecule as a whole to which chiral auxiliaries are attached can be very chiral despite the fact that some chiral auxiliaries themselves have very little chirality content.

Research was conducted to examine the degree of charge delocalization in 4-fluoromethylphenoxide anions using ab initio molecular calculations at the Hartree-Fock and MP2 levels and with the B3LYP density functional. The AM1-SM2 solvation model was used to investigate the effect of aqueous solvation on the rotational profiles. Results suggest that the placement of an electron-donating group (O-) in the para ring position acts to increase the fluoride character of the fluoromethyl group.

Research was conducted to examine various spectroscopic studies of WOs and MoRu porphyrin dimers using variable-temperature 1H NMR, resonance Raman, magnetic susceptibility and X-ray crystallography. The objective was to determine a proper molecular orbital diagram for the dimers. Results demonstrate an unusual molecular orbital diagram which has never been observed before in metal-metal bonded metalloporphyrin dimers.

Research was conducted to measure Kohn-Sham orbitals an eigenvalues using gradient-corrected functionals for a set of varying basis sets, functionals and small molecules, namely, H2O, N2, CrH(sub 6)(super 6-) and PdCl(sub 4)(supper 2-). A comparison of the calculated shapes, symmetries and the order and absolute energy of the eigenvalues was performed with those of Hartree-Fock and one-electron extended Huckel calculations. Results suggest that applying a suitable ax + b scaling would be appropriate if the density functional theory calculations are done with commonly used potentials.

Research was conducted to examine the role of adjacent onium cations and remote substituents on the H-A+ bond equilibrium acidities in dimethyl sulfoxide solution. The study is an extension of previous investigation on ylide thermodynamic stability scale and its implication for the importance of resonance effect on ylide stabilities. Results suggest that part of the stabilization in the phosphonium and sulfonium ylide cases arises from the backbonding stabilization involving the o* and/or 3d orbital participation.