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EuL[[gamma].sub.4] emission spectra of EuS, Eu[F.sub.3], Eu[Cl.sub.3], and [Eu.sub.2][O.sub.3] were measured using a multicrystal, multidetector spectrometer. Splitting of the EuL[[gamma].sub.4] band was observed in the EuS spectra and attributed to exchange interactions between Eu5p and Eu4f. It was shown that because of this splitting, the EuL[[gamma].sub.4] emission could be used for performing spin-selective measurements. This emission exhibited a large chemical shift (~5 eV), depending on the valence state of a compound. The applicability of this emission to valence-selective X-ray absorption fine structure spectroscopy was demonstrated through partial fluorescence yield measurements performed on a 1:1 mixture of EuS and [Eu.sub.2][O.sub.3] and on a valence-fluctuating compound [Eu.sub.3][Pd.sub.20][Ge.sub.6].

A general interpretation is provided for the valency interaction formula (VIF), which applies for VIF pictures as one-electron Hamiltonian operators as well as VIF pictures as one-electron density operators. The VIF method has provided the accurate VIF pictures for hydrocarbons and it can also be used to predict thermal barriers to chemical reactions.

Density functional theory (DFT)/ab initio/symmetry adapted cluster-configuration interaction (SAC-CI) techniques are used to investigate the oxyallyl substructure and the near-infrared (NIR) transition. The results have shown that the mixture of an intermediate diradical character and some zwitterionic character in the molecule along with a large coupling between these two valence band (VB) resonance forms, are responsible for large [gamma] values.

An automated method for systematic hierarchical fragmentation of large molecules is presented utilizing isodesmic reactions. It is shown that by taking appropriate linear combination of fragment energies, it is possible to obtain highly accurate total energies when compared to total energy of full molecule.

A method for expressing the wave function in terms of Lewis structures is proposed and tested on the allyl cation. This method gives results that are consistent with the breathing orbital valence bond (BOVB) calculations for the energy and with the natural resonance theory (NRT) analysis for the weights of the Lewis structures.

The evaluation of ab inito QM/MM free-energy surfaces and activation free energies of reactions in enzymes and in solutions is carried out by using the empirical valence bond (EVB) method as a reference potential and then using linear response approximation (LRA). This new method evaluates the free energy associated with both the substrate and the solvent and helps in obtaining a free-energy barrier that reflects the solute entropy properly.

The perfect pairing approximation from generalized valence bond theory is formulated in an unrestricted fashion for both closed- and open-shell systems using a coupled cluster ansatz. Active electron pairs are correlated but the unpaired or radical electrons remain uncorrelated, leading to a linear number of decoupled cluster amplitudes that can be solved for analytically.

The applicability of the scaled quantum mechanical force field (SQM FF) method to the vibrational spectra of a charged molecule is studied by the example of acetate ion (CH3CO2)(super -)) in sodium acetate for which an empirical valence force field (SVFF) based on IR spectra of six isotopomers of sodium acetate. SQM calculations were done by simple structural models of sodium acetate testing using different QM methods.

The first examples of high-dimensional mixed-valence homometallic cyano-bridged copper complexes were synthesized and characterized. The diverse structural nature of these complexes is governed by the capping amines and the content of water in the reaction media and it is concluded that magnetic interactions are negligible in these mixed valence complexes.

A study deals with the selection and pattern of trianionic symmetrical heptadentate ligands and the binding of these to vanadium. The research work presented offers an invaluable understanding of the synthetic approach in the field of mixed-valence chemistry of vanadium.

The existing uncertainties concerning the beta band of NO as well as to test the adequacy of the molecular quantum defect orbital (MQDO) procedure to describe the vibronic levels of a valence state that is subject to the interaction with Rydberg state (3ppi(C(sub 2)pi)--B(super 2)pi) or of the Rydberg--valence state of NO is studied. The high ratio between the quality of results and the computational effort of this procedure is undoubtedly linked to its analyticity.

An efficient algorithm for the computation of density functional-based orbital reactivity indices, such as the orbitally resolved hardness and softness tensors, total hardness and softness, and Fukui indices, is proposed and implemented in the deMon-2003 code. The theory accounts for all valence orbitals in the computations of the hardness, thus allowing direct and relatively easy computations of the local reactivity indices.

The nonidentify hydrogen transfer reactions between H and strongly electronegative groups is modeled by the reactions X(super one dot)+H-H'->X-H+H'(super one dot), (X=F,C1,Br,I), which exhibit a wide spectrum of barriers and endo-or exothermicities. The semiempirical expressions are useful for the model reactions, and other nonidentity and identity hydrogen abstraction reactions.

The valence bond self-consistent field (VBSCF) calculations explain the qualitative properties of the complexes and transition structures for proton transfer processes. The VBSCF calculations also provide satisfactory analyses of the elements contributing to the barrier heights.

The computation of orbital Fukui indices was considered where all valence orbitals are taken into account. The atomic Fukui Function (FF) and atom in molecule (AIM) softness values were useful in rationalizing the regioselectivity and direction effects, whereas the indicators in orbital resolutions were needed to explain reactivity effects.

A valence bond (VB) is presented and applied to calculate the hidden excited states, 2(super 1)A(sub g) and other covalent excited states of polyenes from C4H6 to C28H30. The VBDFTs method presented enables to gain an insight into a variety of properties of various covalent states of polyene, such as excitation energies and their convergence.

The singlet-singlet electronic spectrum of the anti conformer of n-tetrasilane is studied using multiconfigurational wave functions (CASSCF), second-order perturbation theory (CASPT2), and its multi-state extension (MS-CASPT2) in conjunction with large ANO-type basis sets including Rydberg functions. The results are consistent with the available experimental data and are easily understood in terms of a simple Huckel model of sigma-delocalization.

It is demonstrated that for each of N2O and HCNO, with minimal basis sets, one-electron delocalizations of oxygen 2ppi(sub x) and 2ppi(sub y) electrons into bonding pi(sub x)(ON) and pi(sub y)(ON) LMOs are preferred energetically to electron-pair [2ppi(sub x)](super 2) - -> [pi(sub x)(ON)](super 2) and [2ppi(sub y)](super 2) - -> [pi(sub y)(ON)](super 2) and [2ppi(sub y)](super 2) - -> [pi'(sub y)(ON)](super 1)[pi'(sub y)(ON)](super 1) delocalizations.

Issues concerning a quantitative relationship (interference effect) between basis set truncation errors in MP2 energies and basis set truncation errors in CCSD(T) energies are discussed. It is clear that a new generation of model chemistry methods will no longer need significant error cancellation.

An all-electron STO-6G valence bond investigation of the source of the long, weak N-N bond of asym-N2O3 is presented. Further evidence is found to support the view that the lengthening and weakening of the N-N bond of N2O3 is linked mainly with the nature of the hybridization of the NO-moiety nitrogen atomic orbitals, and the delocalization of the odd electron of the NO2 moiety.

Density functional, broken symmetry techniques have been used to assess exchange coupling constants for di-mu-oxo-bridged copper(II) dimers with varying Cu-O-Cu bond angles. It is demonstrated that O. Kahn's antiferromagnetic term can be ferromagnetic.

Valence bond theory has been used to investigate the transition metal hydride cations TMH+. It was established that modern valence bond methods are valuable for studies involving transition metals.

An analytical expression of varDeltaP2-(Cu) for two bridged Cu(II) dimers is presented.

Single-crystal structure analyses, theoretical calculations and electrical resistivity measurements were used to uncover the phase Zr1-xTixSb.

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.

An examination of the ability of a number of computational methods to forecast the vertical excitation and perhaps also symmetric relaxation energies for 14 excited electronic states of pyrazine is presented. It seems that the most reliable results are provided by B3LYP, EOM-CCSD(T) and CASPT2 methods.

Research is presented describing the back-bonding effects which dominate vibrational frequency variations for NO and O2, and CO adducts of heme. The interactions of heme and its bound ligands with the surrounding matrix of protein may explain the activation of small-molecules.

Ultraviolet photoelectron spectroscopy has been used to study the work function and density of states of multiwall carbon nanotubes. Results indicate that oxidative treatments increase the work function and influence the valence bands DOS.

A study of a heterosupermolecule assembly by covalently linking a TiO (sub)2 ruthenium complex and a viologen has been investigated. Long-lived light-induced charge separation function and its potentiostatic modulation have been demonstrated.

The predictions of the two-valence bond state model for molecular nonlinear optical properties are compared with experimental data on polarizabilities. The values of micro(sub g)(super 2)alpha(sub zz)(0) and micro(g)beta(sub zzz)(0) in different solvents are calculated from the model and compared to experimental measurements for a variety of push-pull polyene molecules in different solvents. Calculations from the two-valence bond state model are shown to be in qualitative agreement with experimental results, although quantitatively the results are mixed.

Research was conducted to examine the synthesis of a compound (ImH)(L1OV-(mu-O)-VOL2) containing two dissimilar tridentate ONS ligands, H2L1 and its bromo derivative H2L2, bound to the metal centers. To understand the molecular and electronic structures of the compounds, X-ray crystallography, EPR, 51V NMR and FT-IR spectroscopic studies were performed. The spectra demonstrate 15-line features with asymmetric distortions that smooth out with the lowering of temperature which may have originated from a solvent-dependent equilibrium.

A bond valence sum (BVS) study of 221 KOn complexes (n = 3-9) obtained from the Cambridge Structural Database was conducted. A new R0 value of 2.113(57) angstroms was computed. Using BVS computations, an interaction between the K+ ion and negatively charged organic groups is suggested. The BVS for K in the K(18-crown-6)+ moiety is usually less than 1. The K+ ion interacted with other ligands so that the final BVS = 1, indicating that the match between the 18-crown-6 and the K+ is not suitable in terms of the electron distribution.

The influence of doping on the host crystal structure of yttrium aluminum garnet (YAG) was investigated using x-ray photoelectron spectroscopy. The consequences of doping were observed indirectly through an analysis of the peaks and variations of the chemical shifts of the main ions forming the YAG crystal. The presence of only one independent oxygen ion was proven, even though the O(1s) spectra of all YAG systems exhibit two readily discerned peaks. This dichotomy is linked to the possible polarization of the oxygen valence electron density between aluminum and yttrium.

The mixed-valent species Fc(4-Py)Ru(NH3)5 super 3+ and Fc(3-Py)Ru(NH3)5 super 3+ exhibit Robin and Day class II behavior, with the oxidized sites ruthenium-centered. The intervalence transfer bands are solvent-dependent and vary almost exclusively with delta/epsilon/sub 1/2degrees, epsilon/sub 1/2degrees Fe(super III)/Fe(super II) - epsilon/sub 1/2degrees Ru(super III)/Ru(super II) that decrease linearly with Gutmann solvent donor number. Experimental values of solvent reorganization energies agree well with those from Hush theory calculations.

The synthesis of a series of cyanide-bridged mixed-valence compounds is reported. These compounds holding the form {[dmbRe(super I)(CO)3](sub n)-Fe(super III)(CN)6} (super 3-n) were examined and their MM'CT absorptions analyzed with Marcus-Hush theory. The shift observed in the MM'CT bands with increasing n is attributed to the rise in the redox potential of the Fe(III) center since there is a corollary increase in Re(I) species linked to it.

The hole-transfer superexchange in dinuclear mixed-valence ruthenium complexes was investigated in a quantitative study. The free energy of resonance exchange was determined from metal-metal coupling elements produced from Hush and Creutz, Newton and Sutin (CNS) models and compared to experimental values that were factored from the free energy of comproportionation. Results showed that the CNS model is an effective technique for predicting the magnitude of hole-transfer superexchange for the Class II mixed-valence complexes of ruthenium.

The role of multivalency in high-affinity lectin-cell interactions was examined in human type A erythrocytes. Isolectins in Griffonia simplicifolia I were purified through a nondenaturing polyacrylamide gel electrophoresis at pH of 8.9. The lectins exhibited greater affinity to cells than to haptenic sugars for which they are specific such as Helix pomatia, lentil lectin and Phaseolus vulgaris. Moreover, cooperative binding was observed in lectin interactions with erythrocytes, while the monosaccharide haptens inhibited isolectin-erythrocyte interaction.

The multitemperature resonance diffraction and structure of the trinuclear mixed-valence complex (Fe3O(OOCC(CH3)3)6(C5H5N)3) were investigated. It was found that the iron-oxygen and iron-nitrogen bond lengths at two iron sites of the complex exhibit significant temperature dependence. In contrast, the bonds to the axial pyridine ligand display the opposite dependence. The order of the absorption edges at each temperature corresponds to that of the bond lengths. These findings indicate the close association between the changes in coordination geometry and the oxidation states of the iron atoms.

Research was conducted to examine the photoionization of SiBr4 in the valence shell and the Br(3d) and Si(2p) inner shell excitation/ionization regions using a time-of-flight mass spectrometer and synchrotron radiation over the range 30-133 eV. Photoelectron-photoion coincidence and photoion-photoion coincidence techniques were employed to investigate the dissociation processes of SiBr4. Results provide information on energy dissipation processes of the core-excited states.

The syntheses and structures of a series of pentanuclear bow-tie clusters, [(Cp*Ir)2(mu3-S)2M(mu3-S)2(IrCp*)2]n+ (M = Fe, Co, Ni), illustrating the correlation between the cluster electron counts and the core structures of 78-81 valence electron clusters are described. The potential order Fe

Experiments were performed to examine a group of cyanide-bridged mixed-valence translation metal complexes using Stark (electroabsorption) spectroscopy. While the Stark spectrum observed for compounds two and four exhibited two overlapping bands, compounds one and three displayed a broad absorption band and an unstructured and broad absorption band respectively. The existence of ground stage charge delocalization influenced the presence of an effective charge-transfer distance of less than 100% of the metal-metal separation distance.

The structural properties of a series of compounds based on Sb(sub 3) as a nuclear unit were investigated using ab initio analysis. Specifically, the suitability of the Zintl-Klemm-Busmann principle on alkali-antimony clusters of the form A(sub 3)Sb(sub 3) and A(sub 4)Sb(sub 3)(super +) (A = Na, K, Rb) was analyzed. It was found that the structure of the 18 valence electron units pertaining to bonding, geometry and stability is analogous to the respective properties of the isoelectronic ozone molecule.

Electroabsorption and related spectroscopic studies were conducted on bimetallic tetraiminoethylenedimacrocyclic complexes. Additional near-infrared Raman investigations on mixed valent and isovalent diiron species support the observed delocalized mixed-valence ion behavior. Results also show that electroabsorption causes anomalous polarizability and that metal-to-ligand charge transfer excitation causes the blue green electronic absorption band in the mixed-valent complex.

The different methods for calculating the transfer integral in mixed valence compounds were evaluated. The different physical properties which influence the electron transfer such as overlap, through bond delocalization, relaxation and polarization of molecular orbutals were described. The ability of the various methods of calculations to integrate these physical effects has been evaluated.

Hartree-Fock, density functional and second-order Moller-Plesset perturbation theory were used to calculate relaxed potential energy surface scans of 1.6-methano(10)annulene and its derivatives to explore nonclassical structures conforming to a very long C1-C6 bond (~1.8 A). The findings indicate that methanofullerenes may exist and that constraints regarding the bookfolding angle were strong in methano(10)annulenes but moderate in methanofullerenes.

A study was conducted to analyze the electronic mechanism for the gas-phase Diels-Alder cycloaddition reaction using valence-bond theory in its spin-coupled form and intrinsic reaction coordinate computations. Carbon-carbon bond lengths of the reactions were determined through geometrical computations. Results indicated that the best schematic representation of the Diels-Alder reaction was through a homolytic mechanism.

Ab initio calculations of the electron-transfer matrix element V(sub ab) in CuI-CuII mixed-valence compounds were conducted for some cluster models intended to mimic the characteristics of the (NEt4)(Cu2Cl4). Based on the theoretical analysis, both V(sub ab) and the potential energy profiles versus an idealized electron-transfer reaction coordinate were calculated for different scenarios. Results indicate that both V(sub ab) and the energy profiles are largely dependent on the nature of X.

Research was conducted to examine site valencies and spin coupling in the 3Fe and 4Fe(S=1/2) clusters of Pyrococcus furiosus ferredoxin by 57Fe electron nuclear double resonance (ENDOR) spectroscopy at cryogenic temperature. The addition of excess cyanide ion to the reduced 4Fe protein yields a unique Fe which can form a 3Fe cluster that, in turn, can form 4Fe when reconstituted. This fourth Fe provides for the preparation of a series of 57 Fe cluster isotopologs. Experiment shows that cyanide binding leads to a valency switch from F25+ to Fe2+.

A study was conducted on the electronic interactions between pi-bridged mixed valence compounds' nitrogen-centered charge-bearing units. The E(sub op) of the Hush theory was employed in equating the transition energy of the longest wavelength band. Results show that charge delocalization is larger in pi systems than in transition metal-centered units because of high V values in nitrogen-centered units.

The magnetic properties of LaT(sub 13-x)Al(sub x) were measured using the empirical electron theory. The hybridization in various atomic states were examined. A conformity between the experimental findings and calculated data on the magnetic properties of the compounds were observed. Meanwhile, the valence electronic structures revealed a correlation between the electronic structures and magnetic properties of the samples. The electronic properties of the cobalt atoms and the magnetic properties of the whole compound were influenced by the aluminum content of LaCo(Sub 13-x)Al(sub x).