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Three pathways for the reaction of bispidine-iron(II) complexes are studied where bispidine is a rigid tetradentate amine/pyridine ligand with [H.sub.2][O.sub.2]. The findings reveal that there is a direct conversion of the dispidine-iron(II)-hydrogen peroxide complex to the corresponding iron(IV)-dihydroxo compound which is a novel possible oxidant for the dihyroxylation of olefins.

A combination of molecular mechanics (MM), electron paramagnetic resonance spectrosocpy (EPR) and spectra simulation (MM-EPR) are used to determine the solution structures of di- and tri-nuclear copper(ll) complexes of melamine-based oligomacrocyclic ligands. The spin Hamiltonian parameters of the mononuclear, melamine-appended macrocyclic ligand copper(II) complex are determined by EPR spectroscopy and were also studied with DFT methods.

The hexadentate dispidine-based ligand 2,4-bis(2-pyridyl)-3,7-bis(2-methylenepyridine)-3,7-diazabicyclo[3.3.1]nonane-9-on-1,5-bis(carbonic acid methyl ester), L(super m), with four pyridine and two tertiary amine donors, based on a very rigid diazaadamantane-derived backbone, is coordinated to a range of metal ions. On the basis of experimental and computed structural data, the ligand is predicted to form very stable complexes.

The molecular and electronic structures of mixed-valence face-shared (Cr, Mo W) d(super 2)d(super 3) and (Mn, Tc, Re) d(super 3)d(super 4) [M2Cl9](super 2-) are calculated by density functional methods in order to investigate metal-metal bonding in this series. Results of the investigation are presented.

Research has been conducted on the tetradentate ligand copper(II) and copper(I) complexes. The preparation and analysis of these complexes carried out spectroscopically, electrochemically and structurally are described.

Research has been conducted on the tetradentate ligand. The results of the density-functional theory calculations indicate that this ligand enforces strong binding of a co-ligand to the copper(II) center.

Azurin, pseudoazurin and nitrite reductase, blue copper proteins are examined.

The syntheses of a series of bismacrocyclic systems with two ferrocenyl end groups and two cavities with mixed imine thia donor sets are described. These bismacrocyclic ligands are ideal for copper(I) coordination chemistry, producing heterotetranuclear Cu(sub 2)Fe(sub 2) compounds. Schiff-base ligands with ferrocenyl groups are produced through the reaction of ferrocenylamine with a suitable aldehyde or with derrocenecarboxaldehyde and suitable amines.

Research was conducted to examine the structural properties of the four-coordinate dinickel(II) and the (4+1)- coordinate dicopper(II) compounds of two bis(diamine-diamide) ligands, based on the condensation of 1,8-diamino-3,6-diazaoctane or ethane-1,2-diamine with bismalonic esters. Methodologies used included X-ray crystallography, molecular modeling and EPR spectroscopy. Results suggest that the most stable conformations are those in the solid state and in solution.

The synthesis of a novel cyclic octapeptide related to patellamide A, cyclo(Ile-Ser-(Gly)Thz-Ile-Thr-(Gly)Thz) (PatN), was described. The octapeptide was reacted with copper(II) and base to form mono- and dinuclear complexes while the coordination environments around copper(II) were characterized by electron paramagnetic resonance spectroscopy. Weakly dipole-dipole coupled electronic paramagnetic resonance spectra based on structural properties obtained from force field measurements were simulated to analyze the solution structure of the purple dicopper(II) compound.

X-ray crystal structural analyses and solution hydrogen nuclear magnetic resonance were used to analyze the syntheses of a variety of large macrocylic ligands and the corresponding dicopper(I) compounds. Findings showed that the structures of the dicopper(I) compounds of the ligands were similar to the solid-state structures. The structural similarity indicated that ligand preorganization is not a prerequisite for double-helical figure-of-eight structures.

Research was conducted to study the preparation, structure, and electronic properties of (Fe(trans-diammac))2+ (trans-diammac) = exo-6-13-diamino-6,13-dimethyl-1,4,8,11-tetraazatetradecane, a low-spin iron(II) hexaamine compound. A crystal structure analysis shows that the iron(II) coordination geometry is distorted octahedral with very short in-plane Fe-N distances. Results of model studies are compared to the spectroscopic, structural and magnetic properties of the compound.

Research was conducted to investigate the binuclear copper(II) complexes of bis(pentadiene) ligands derived by attaching 2-pyridylmethyl arms to the four secondary nitrogens of bis(tacn) macrocycles. Structural, electrochemical and electron paramagnetic resonance studies reveal interesting variations in the preferred configuration of Cu(II) complexes of the series of bis(pentadentate) ligands. Findings also showed varying reduction potentials with Cu***Cu separation.

Molecular mechanics can be an efficient approach for the design of new organophosphate ligands with metal ion specific lanthanoid(II) extractability properties. This is evidenced by a molecular mechanics force field for lanthanoid complexes coordinated to organophosphate and aqua ligands, whose parameters were fitted to all relevant X-ray crystal structures available in existing literature. A quantitative structure-property relationship between the complexation strain energy difference between the lanthanoid cations and La(III) and their extractability is also presented.

Chlorination of (14)aneS4-ol (1,4,8,11-tetrathiatetradecan-6-ol) and cis/trans-(14)aneS4-diol (cis/trans-1,4,8,11-tetrathiatetradecane-6,13-diol) produces the corresponding dichloro-substituted macrocycles (14)aneS4-Cl (1,4,8,11-tetrathiatetradecane 6-chloride) and cis/trans-(14)aneS4-Cl2 (cis/trans-1,4,8,11-tetrathiatetradecane 6,13-dichloride) in good yield. Thiomethylation of the chlorides leads to ring-contracted-pendent thioether macrocycles (13)aneS4-CH2SCH3 (1,4,7,10-tetrathiatridecane-5-(methylthio)methane) and cis/trans-anti-(12)aneS4-(CH2SCH3)2 (1,4,7,10-tetrathiadodecane-5,11-bis((methylthio)methane)).

The thermodynamics and kinetics of (hexaamine)cobalt(III/II) redox couples are analyzed based on steric strain caused by the ligand systems. The intersections of the oxidized and reduced forms of a large number of (hexaamine)cobalt(III/II) redox couples are related to the inner sphere reorganization and correlated with empirically obtained electron self-exchange rates. The calculation of redox characteristics can be used for the design of new reductants and oxidants with specific potentials and electron transfer rates.

A force field had been developed and utilized for the design of a spacer group for bis[tris(2-pyridylmethylamine)]-type ligands that stabilized the end-on (mu-peroxo)dicopper(II) product. The force field was mainly based on structural data and did not allow accurate thermodynamic analysis. The experimentally determined energy difference was also related to the difference between the two unlinked mononuclear and ethyl-linked dinuclear compounds.

The angular overlap model (AOM), based on molecular mechanics calculations (MM-AOM), helps determine and interpret EPR spectra of low-spin iron (III) complexes. Calculated EPR spectra of complexes agree with the experimental data, and model AOM calculations help determine the modes responsible for inaccuracies. MM-AOM approach shows that a highly distorted species, C1, is responsible for the observed EPR spectrum of (Fe(terpy)2)(3+).

Molecular mechanics calculations facilitate the determination of solution structures and isomer ratios of various bis(beta-diketonato)titanium(IV) and -cobalt(III) complexes. Titanium(IV) structures exhibit a trans effect. Calculated isomer distributions agree with the NMR spectroscopic data. Molecular structures calculated through strain energy minimization give more information about budotitane, a drug for cancer chemotherapy.

The development of a dynamic mass budget for the concentrations of mirex, a flame retardant and pesticide known for its high lipophilicity and extreme persistence, is presented. The organochlorine has entered the food chain of Lake Ontario from its sources in Niagra and Oswego Rivers. Mirex's removal is due to outflowing water and migrating lifeforms. Results indicate over 2700 kg of Mirex has entered Lake Ontario and 550 kg have been removed.

The Ni(III), Co(III) and Cr(III) complexes of hexaamine cis-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane-6, 13-diamine (cis-diammac) were synthesized and characterized. The spectroscopic and structural analyses using angular overlap model and molecular mechanics computations show that the (M(cis-diammac))n+ complexes have trigonally twisted configuration and possess relatively more positive M(super II/III) redox couples than their trans-diammac analogues. In addition, crystallographic analysis of the complex (Cr(cis-diammac))(ClO4)3.2H2O was performed.

The d-d electronic transitions of hexaamine complexes of Cr(III), Co(III) and Ni(II) complexes were obtained by molecular mechanics and angular overlap model calculations. The results showed a proportionality constant, C, for all the M-N bonds. In addition, the C values were determined to increase with the increasing substitution with alkyl groups for all the transition metal systems.

The transition metal complexes (M(dipa)2)n+, where dipa = di-2-pyridylmethanamine and M = Fe(III), Fe(II), Co(III), Ni(II) and Cu(II) were synthesized. An equilibrated mixture of rac and meso isomers were identified in (M(dipa)2)n+. Pyridyl groups were found to stabilize more types of complexes than its triamine analog. Moreover, molecular mechanics calculations showed that steric effects determined preference for the rac isomer.

Force field parameters for the Cr(III), Fe(III) (S = 1/2), Co(III), Ni(II) (S = 1), Cu(II), Zn(II) and Rh(III) with amine, pyridine, carboxylate and thia ether ligands were determined via molecular mechanics calculations. Calculations involved the refinement of the positions of the axial donor atoms to allow the prediction of the structures of the complexes without restrictions imposed on the coordination sphere.

The determination of the solution structures of the binuclear copper(II) complexes of the ligands 5,5'-bis(3,7-dehydro-3,7-diazanonane-4,6-dione-1,9-diamine), 5,5'-bis(3,7-diazanonane-1,9-diamine) and 5-methyl-5-nitro-3,7-diazanonanedioate were undertaken via the combination of molecular mechanics and EPR spectroscopy. The calculated structures of the first two complexes revealed a close correspondence with the structures determined by X-ray spectroscopy.

Three ligand exchange techniques lead to enantiomeric separation of Co(III) and Ni(III) complexes with chiral quadridentate ligands combined with racemic bidentate ligands. The R/S ratios obtained agree within 5% of those predicted by molecular mechanics calculations using minimized strain energy equations. The ligands involved are N,N'-bis(2S-2-pyrrolidinylmethyl)ethane-1,2-diamine (S,S-epm) and -propane-1,3-diamine (S,S-ppm) combined with the bidentate propane-1,2-diamine, 2-pyrrolidinylmethanamine and alanine. The system exhibiting the best separation is the Ni(S,S-epm)(L)(2+) complex although the Ni(S,S-ppm)(L)(2+) system is more amenable to large scale separation.

Pentacoordinate complexes of the divalent metal ions [M.sup.2] = [Mn.sup.II] (S = 5/2), [Ni.sup.II] (S = 1) and [Cu.sup.II] (S = 1//2) with the pentadentate bispidine ligands [L.sup.1] and [L.sup.2] are useful building blocks for the assembly of trinuclear cyanide-bridged complexes based on hexacyanometalates. The absence of single-molecule magnetic behavior in all spin clusters is due to the large angular distortion of the [[Fe[(CN).sub.6]].sup.3-] center and the concomitant quenching of orbital angular momentum of the [Fe.sup.III] ([super 2][T.sub.2g]) ground state.

Magnetic anisotropy in cyanide-bridge single-molecule magnets (SMMs) with [Fe.sup.III]-CN-[M.sup.II] (M = Cu, Ni) exchange-coupled pairs is analyzed by using a density functional theory (DFT)-based ligand field model. Spin Hamiltonian parameters derived for linear Fe-M subunits are combined by using a vector-coupling scheme to yield the spin Hamiltonian for the entire spin cluster.

The epoxidation and 1,2-dihydroxylation of cyclooctene with the bispidine/iron(II)/[H.sub.2][O.sub.2] catalyst system is studied using density functional theory calculations. The radical intermediate formed reacts with [O.sub.2] to form epoxide or with OH radical to form a diol, showing a spin-crossover in the ferryl oxygen transfer path.

Linear and quadratic Jahn-Teller coupling models in the five-dimensional space of the [[epsilon].sub.g] and [[tau].sub.2g] octahedral vibrations Jahn-Teller (JT) coupling problem are used for studying the ground-state potential energy surface of M[(CN).sub.6]. The implications of pseudo and dynamic JT coupling are explored with [[Fe[(CN).sub.6]].sup.3-] as a model complex.

The geometry and electronic structure of a range of [Fe.sup.IV][double bond]O complexes with two terta- and two isomeric pentadentate dispidine ligands are examined using density functional theory (DFT) calculations. The Jahn-Teller-type distortion in the high-spin state of the two isomers is very different due to the rigidity of the bispidine ligands and the orientation of the Jahn-Teller axis.

Exchange coupling across the cyanide bridge in a series of novel cyanometalate complexes with [Cu.sup.II]-NC-[M.sub.III] fragments is explored using the broken-symmetry DFT approach and an empirical model. The DFT values of the exchange coupling parameters resulting from different occupations of the [t.sub.2g] oribtals of low-spin [[t.sub.2g].sup.5] [Fe.sup.III] are employed to discuss the influence of spin-orbit coupling on the isotropic and anisotropic exchange coupling in linear Cu-NC-Fe pairs.

The magnetic properties of the assemblies, dependent on monocation A (A = [Li.sup.+], [Na.sup.+], [K.sup.+], [Rb.sup.+], [Cs.sup.+], [NH.[sub.4].sup.+] is discussed and pathways for ferromagnetic exchange between [Ni.sup.II] and [Fe.sup.III] or [Cr.sup.III] are demonstrated. Variation of A monocations, used for charge neutralization, does not lead to changes in the over-all geometry of {M-CN-Ni(L)} building blocks.

The iron(II) complex of a tetradentate bispidine ligand with two tertiary amines and two pyridine groups was oxidized with tert-butyl hydroperoxide to the corresponding end-on tert-butylperoxo complex. Characterization of the compound with UV-vis, resonance Raman, and EPR spectroscopy, as a function of the solvent, showed that the compound to be a spin-crossover with both low-spin and high-spin isomers in good agreement as computed by DFT.

Research has been conducted on 2,3,2-tet (3,7-siazanonane-1,9-diamine). The authors have investigated copper(II)-assisted condensation of this compound with formaldehyde and cyclopentanone, and report that this condensation has led to mono- and bis-macrocyclic Mannich condensation products with cyclam-type tetraaza macrocycles coordinated to copper(II).

Tetraazamacyrocyclic ligands are of special interest for various applications, and coordinating side chains may increase the stability of the metal complexes and tune the selectivity between various metal ions. The template synthesis of the diammac derivative pypymac (pypymac = 6,13-bis(2-pyridinyl1)-1,4,8,-11-tetraazacyclotetradecane together with a structural study of the metal-free ligands and their copper(II), cobalt(III), nickel(II) and zinc(II) complexes are presented.