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Ab initio unrestricted Hartree-Fock calculations with a 6-31G* basis set on 2,6-dimethylphenol (DMP or monomer) and 4-(2,6-dimethylphenoxy)-2,6-dimethylphenol (dimer) indicate that, in the case of the monomer, the only aromatic carbon atom bearing a partial positive atomic charge is the para carbon in the cation in the singlet state. For the dimer, the presence of a p-phenoxy substituent leads to a partial positive charge for the para carbon in the first aromatic ring in all states. This charge is considerably greater for the singlet cation.

The X-ray crystal structures of the two title compounds demonstrate the large stability of the dinuclear paddle-wheel unit in copper(II) carboxylates and the versatility of the carboxylate ligands. The latter are involved in additional coordination to another paddle-wheel unit, with or without additional bridging ligands, producing novel polynuclear structures. These compounds have unusual spectroscopic and magnetic characteristics.

The effect of the asymmetric coordination geometry on the electrochemical, electronic and photochemical properties as well as the electronic properties of the intervalence compounds were characterized. Spectroelectrochemical studies indicated the presence of a weak interactions between the metal centers and the dinuclear species. A strong pi-acceptor, pyrazine, interacted with a strong sigma-donor, triazole ring in the ligand.

A novel method for the synthesis of two novel[Fe3(4-isopropyl-1,2,4-triazole)6(H2O)6](tosylate)6.2H2O were developed based on the reaction of triethyl orthoformate and monoformylhydrazine with iptrz. X-ray crystallographic analysis of the resulting [Fe3(4-isopropyl-1,2,4-triazole)6(H2O)6](tosylate)6.2H2O linear trinuclear iron(II) compounds indicated the presence of spin-transition behavior. Furthermore, Mossbauer spectral analysis of [Fe3(4-isopropyl-1,2,4-triazole)6(H2O)6](tosylate)6.2H2O indicated the presence of a strong interaction between the central and end iron ions.

A novel pyrazole and imidazole containing dinucleating ligand, 1,5-bis(1-pyrazolyl)-3-(bis(2-imidazolyl)methyl) azapentane (Hbpzbbiap) and two dicopper(II) complexes containing the Hbpzbiap ligand were designed and synthesized in an attempt to come up with a copper-zinc superoxide dismutase (SOD). The compounds were characterized using X-ray crystallography, magnetic susceptibility testing, electron paramagnetic resonance spectrometry, cyclic voltammetry, electronic spectroscopic studies and SOD-like activity measurement. The results indicated that the copper complex (Cu2(bpzbiap)Cl3) exhibits properties similar to superoxide dismutase and thus considered a good model for the enzyme.

The kinetics of formation and structure of the (Pt,Pt) intrastrand adduct were investigated through the monitoring of the interaction of ((trans-PtCl(NH3)2)2(mu-H2N(CH2)nNH2))(super 2+) (1,1/t,t,n = 2-6) with d(GpG) using nuclear magnetic resonance spectroscopy and molecular modeling. Relatively fast initial coordination to either the 5'-G or the 3'-G was noted, compared to the second binding step, ring closure to the macrochelate adduct. Faster reaction and greater yield of macrochelate were observed for complexes linked by a longer diamine chain, as against shorter n=2,3 diamine linkers.

Copper(II) ions are coordinated in a didentate fashion by bima and bimam ligands due to the steric effect of its subunits. The formation of an intramolecular chelate hydrogen bond between the nitrogen and chloride anion produces three complexes. A ion-exchange resin ratio of 1:1 is exhibited by the coordination compounds. Cu(II) uptake is high at low pH due to the coordination of only two imidazole nitrogens of the ligands around the Cu(II). Resin uptake capacity for Cu(II) remains unaffected by several different competing diamine ligands except tartrate in the solution.

Three dinuclear copper(II) complexes and one mixed-valence tetranuclear cluster with asymmetric imidazole-containing ligand bis(1,1'-imidazole-2-yl)(4-imidazole-4 5 -yl)-2-azabutane have been prepared and characterized. The results showed that all the four complexes contain a dinuclear unit with the two copper(II) ions being held by ligand sharing. The copper(II) ions are coordinated in a square-pyramidal geometry with three imidazole nitrogens, one amine nitrogen and a weakly coordinated anion BF(sub 4)(super -), ClO(sub4)(super -), NO(sub3)(super -), or CuIBr(sub 3)(super 2-).

The FE(II) complex Fe(abpt)2(TCNQ)2 has coordinated radical anions characterized by spin-crossover behavior, where TTCNQ represents the organic radical 7,7'8,8'-tetracyanoquinodimethane. The spin-crossover variables have displayed potential applications in molecular electronics and in biological systems. The TCNQ case is defined by the involvement of the radical anion in coordination.

The effect of the molecular structures on the Jahn-Teller active centers was determined by X-ray diffraction on Cu(mtz)6(BF4)2, mtz = 1-methyltetrazole. The structure of the copper complex was composed of two independent pairs of centrosymmetric molecules per unit cell. The big discrepancies in the Cu-N distances on the two Cu(mtz)6(super 2+) complexes markedly affected the Jahn-Teller activites at the two sites. The different Jahn-Teller effects were found to be influenced by the temperature-dependency of the site strains which accounted for the differences in Cu-N bond lengths.

The synthesis and characterization of the antitumor active platinum compound (bis N-methylimidazol-2yl carbinol)dichloroplatinum(II) are described. The complex showed preference for G-N7 binding based on its interaction with short DNA fragments. The inactivity of its analog dichloro(N1,N1'-dimethyl-2,2'-biimidazole)platinum(I) has been attributed to differences in steric and kinetic properties.

The transition metal coordination compounds are prepared from 1,9-bis(3,5-dimethyl-1-pyrazolyl)-3,7-dithia-5-nonanol (Hbdnol), which acts as a pentadentate ligand. IR, ligand field spectroscopy and EPR reveal that Ni(bdnol)Cl3 exhibits ferromagnetic intramolecular interaction and an antiferromagnetic ordering between adjacent dimers. The dinculear copper complex are antiferromagnetically coupled and are EPR silent at room temperature. The syntheses of Co(bdnol)(NCS)3, Zn2(bdnol)Cl(NCS)2, Cu2(bdnol)(NO3)3 and Cu2(Hbdnol)(NCS)2 are discussed.

The 4,4'-bis(2-picolinimino)-2,2'-bibenzimidazoles (L) are synthesized from 1,1'-disubstituted 4,4'-diamino-2,2'-bibenzimidazoles and 2-pyridinecarboxaldehyde as models for type 3 sites of hemocyanin and tyrosinase. Tuning of metal-metal distance occurs through polymethylene bridge in the ligand's backbone. The resulting complex exhibits an open conformation with distinct (4 + 2) copper coordination. Two oxygenation products dicopper complexes, Cu(II)4(H2(L3)O2(super 2-))2(ClO4)4 and (Cu(I)2(L3')2)(ClO4)2 are synthesized and the structures are analyzed.

Single crystal electron paramagnetic resonance analysis of (Cu2(abpt)(SO4)2(H2O)4).H2O (abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) (1) reveals that it contains asymmetric dinuclear motifs with copper(I) ions attached in equatorial plane via a didentate bridging sulfate anion and a N1, N2 bridging chelating abpt ligand. The stability of the asymmetric dinuclear unit depends on the extent of hydrogen bonding. The EPR spectra of 1 is discussed.

The chloropolypyridyl ruthenium complexes display cytotoxicity in murine and human tumor cell lines, and complexation to DNA at guanine residues forms interstrand crosslinks involved in the biological effects of ruthenium complexes. The ruthenium complexes investigated have the structural formulas Ru(terpy)(bpy) Cl Cl, cis- Ru(bpy)2Cl2 and mer- Ru(terpy) Cl3 (terpy = 2,2':6'2'-terpyridine, bpy = 2,2'-bipyridyl).

X-ray analysis of the synthesis and magnetic properties of Cu(L)(sol-)(A)(Hsol) compounds, Cu2(tbz)2(CH3O)2(ClO4)2(CH3OH)2, Cu2(tbz)2(NO3)(CH3OH)2(NO3)(CH3OH)2, and Cu(tbz)(N3)22(CH3OH)2 shows that copper(II) alkoxy dimers are produced with tbz and qbz in the presence of weakly coordinating compounds. Monomeric species are obtained in the presence of chlorides whereas, bis-mu-(1,1)-bridging dimers are formed with azido anion. The dinuclear motifs are EPR silent and reveal a weak signal of monomeric impurities. The magnetic properties of the compounds are discussed.

Colorless cubic crystals of a polymeric bismuth citrate may be synthesized by slow evaporation of an aqueous solution of bismuth citrate and ammonia. The polymer is a collection of dodecanuclear oxo-bismuth anionic units (Bi12O8cit4-8)12- bridged by carboxylate to citrates to form (NH4)12(Bi12O8cit8)(H2O)10. At higher concentrations, the solution is relatively homogeneous for Bi(12) aggregations, but at lower concentrations anionic clusters of Bi(12), Bi(24) and (Bi12)n are found. On adding citrate to the solution, a ligand exchange is observed resulting in dissociation of the clusters. The aqueous solution of the compound is compared to bismuth subcitrate, an ulcer healing agent.

X-crystallographic studies of two prepared complexes, (guanidinium)(Ni(dmit)2)2 (dmit = 2-thioxo-1,3-dithiole-4, 5-dithiolate) and (1,1-dimethylguanidinium)(Ni(dmit)2)2, reveal that these complexes belong to a space group P1 and they have a triclinic structure. The layers of Ni(dmit)2 units have weak two-dimensional conduction pathways, as revealed by intermolecular orbital overlap calculations. Conductivity studies of these compounds reveal their semiconducting behaviors.