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The synthesis, magnetic, electrochemical, spectroscopic, and physical studies of group of homo- and heterometal complexes is reported. The complexes were generated by using the metal complex [Ni.sup.II][(oximato).sub.3] monoanions as tridentate ligands.

Several studies are conducted to explain the monoanionic [pi]-radical redox state observed in various [alpha]-iminoketones in bis(ligand)metal complexes of nickel and cobalt. These complexes are shown to consist of a high-spin divalent metal center that is strongly coupled to two ligand radicals.

The preparation and full characterization of the mononuclear neutral complexes [P[t.sup.II]([super t]bpy)(A)] and [P[t.sup.II]([super t]bpy)(B)] (where bpy = 4,4'-di-tert-butylbipyridine, (A) = 3,6-bis(trimethylsilyl)benzene-1,2-(dithiolate(2-) and (B) = 1,2-bis(4-tert-butylphenyl)ethylene-1,2-dithiolate(2-)) is described. The cations are shown to dimerize in C[H.sub.2]C[l.sub.2] solution affording diamagnetic dimers.

A synthesis of a series of mononuclear square-based pyramidal complexes of iron having two 1,2-diaryl-ethylene-1,2-dithiolate ligands in various oxidation levels is conducted. This showed that redox noninnocent ligands exist in at least two oxidation levels, namely, the diamagnetic closed-shell dianionic form and paramagnetic open-shell monoanionic form.

Dinickel(II) complexes of the ligands N,N'-di-p-anisylformamidinate (DAniF) and N,N',N'-tripheynlguanidinate (TPG) are synthesized and crystallographically characterized, along with their one-electron oxidized analogues. In both systems, the Ni-Ni distances become shorter by ~0.1 A upon oxidation and it is proposed that this species contains a [Ni.sub.2.sup.6+] core with a single Ni-Ni sigma bond.

The electronic structure of [Ni(super II)(L(sub N)(super ISQ))2] and of [Pt(super II)-(L(sub O)(super ISQ))2] is calculated by density functional theoretical and correlated ab initio methods. Electronic and resonance spectra is reported, and the electronic structures of all members of this electron-transfer series is established.

Ligating properties of four potentially tridentate bisphenol ligands containing [O, X, O] donor atoms (X = S, Se, P, or P=O) toward the vanadium ions in +IV or +V oxidation states are studied. A combination of density functional theory calculations and experimental electron paramagnetic resonance (EPR) investigations indicates a dramatic effect of the heteroatoms on the electronic structure of (X = S, Se, P, or P=O) with consequent reordering of the energy levels.

The preparation of seven new bis(o-iminosemiquinonato)copper(II) complexes from differently substituted N-phenyl-2-aminophenol-based ligands are described. The copper(II) complexes containing redox-active ligands exhibit oxidase-like reactivity based on a primarily ligand-derived redox mechanism.

The strongly electron-donating ligand composed of two tert-amines and two phenolate donor groups were utilized to prepare two mononuclear [Fe.sup.III] complexes [LFe([[eta].sup.2]-N[O.sub.3]) and [LFeCl]. The results showed that the ligand could be adopt a cis and a trans conformation to oxidize [LFeCl] at moderate potentials to yield the monophenoxyl-radical complex [[LFeCl].sup.+] and the bisphenonoxyl-radical complex [[LFeCl].sup.2+].

An example of a hexacoordinated bis(o-iminobenzoquinone)copper(II) complex (complex 2) with [Cu.sup.II]-iminobenzoquinone bonds is prepared by oxidizing a square-planar bis(iminobenzosemiquinone)copper(II) compound with molecular bromine. Electrochemical measurements have shown two successive one-electron reductions of the ligand and the reactivity of the complex 2 as an oxidizing agent toward ethanol and triethylamine is examined.

The synthesis and the coordination chemistry of a tetracopper(II)-tetraradical cuboidal core are described. The analysis reveals that the complex can also be easily be used to study the synthesis of phenoxazinone.

A combination of experimental, as well as density functional theoretical study is employed to analyze the electronic structures of the tris(dioxolene)chromium and tris(dithiolene)chromium complexes of the electron-transfer series [[Cr[(dioxolene).sub.3]].sup.z] (z = 0, 1-, 2-, 3-).

The synthesis and characterization of the gold cluster compound [[Au.sub.18][(P).sub.2][(PPh).sub.4](PHPh)[(dppm).sub.6]][Cl.sub.3] (where dppm = [Ph.sub.2]PC[H.sub.2]PP[h.sub.2]) which shows a central [Au.sub.7[P.sub.2] unit formed by two P centered gold tetrahedra sharing the central gold corner is presented.

The isolation of four members of the electron-transfer series [[Fe(NO)[(L).sub.2].sop's] (z = 1+, 0, 1-, 2-) as solid materials (R = p-tolyl) is presented. The results show that the monocationic, neutral, and monoanionic species possess an [{FeNO}.sup.6] (S = 0) moiety where the redox chemistry is sulfur ligand-based.

The synthesis of [Ni([.sup.3.L.sup.ISQ])2], [Pd([.sup.3.L.sup.ISQ])2], and [Co([.sup.3.L])2], where [([.sup.3.L]).sup.R] represents the o-phenylenediimide (n = 2-), the corresponding radical (n = 1-), and the diimine (n = 0) derivative of the bulky ligand N,N'-bis(3,5-di-tert-butylphenyl)-1,2-phenylenediamine, H2[[.sup.3.L].sub.PD1] is reported. The electro- and spectroelectrochemistry of the tetrahedral complexes [Ni([.sup.3.L.sup.ISQ])2] and [Co([.sup.3.L])2] are compared with those of nearly square planar [Pd([.sup.3.L.sup.ISQ])2] and the electronic structure of tetrahedral 1 is elucidated by broken symmetry (BS) density functional theory (DFT) calculations.

Imido complexes with the tridentate Schiff base N-salicylidene-2-aminophenol (sapH2) were synthesized using Ni(NAr)2Cl2(dme) (NAr = 2,6-dimethyl phenylimido, 2,4,6-trimethylphenylimido, 2-tert-butyl-phenylimido). The intermediate Mo(NAr)(sap) (OCH3)2 formed during the synthesis of such compounds can be reacted with bidentate aromatic ligands to form complexes in which, the bidentate ligand occupies an equatorial and axial position.

Oxidative cyclodehydrogenation is an important process in the formation of the new graphene, N-1/2HSB, which results from the FeCl3-catalyzed oxidative cyclodehydrogenation of 1,2-dipyrimidyl-3,4,5,6-tetra-(4-tert-butylphenyl)benzene. The new ligand N-1/2HSB, its Ru(II) complexes and also the half-cyclized N-1/2HSB are characterized by (super 1)H, NMR, infra-red (IR), ESI-MS, and accurate aromatic ligands.

A series of new S-methyl-1-pehnyl-isothiosemicarbazones H2[L(super 2)], H2[L(super 3) is synthesized. and different ligand oxidative products of the ligands H2[L(super 5)] and H2(L(super 6)] are characterized and isolated. The density functional theoretical (DFT) and correlated ab initio calculations are also presented.

The synthesis of the tetradentate ligand N, N' -bis(3,5-di-tert-butyl-2-hydroxyphenyl)ethylenediamine, H4[L(super 1)], and its unsaturated counterpart glyoxal-bis(2-hydroxy-3,5-di-tert-butylanil), H2[L(super 2)] is described.

A series of mononuclear, octahedral first-row transition metal ion complexes mer-[M(super II)L(super 0)-(sub 2)]PF9sub 6) containing the tridentate ligand 2,6-bis[1-(4-methoxyphenylimino)ethyl]pyridine (L-(super 0) and a divalent Mn, Fe, Co, Ni, Cu, Zn ion have been synthesized and characterized by X-ray crystallography. The ligand is noninnocent and can be reduced by one-electron (L(super 1))(super 1-).

The reaction of [M(tren)Cl[sub2]]Cl(M=Co(III), Cr(III)) with benzene-1,2-dithiol, H[sub2](dbt), and 3,6-bis(trimethylsilyl)benzene-1,2-dithiol, H[sub2](tmsdt), in a water/methanol mixture in the presence of potassium tert-butoxide produced green crystals of [M(tren)(bdt)](PF[sub6])[sub½](Cl)[sub½]∙H[sub2]O (1(PF[sub6])[sub½](Cl)[sub½]∙H[sub2]O, M = Co; 2(PF[sub6])[sub½]](Cl)[sub½]∙H[sub2]O, M = Cr) and [M(tren)(tmsdt)](PF[sub6])[sub½](CI)[sub½]∙H[sub2]O (1a(PF[sub6])[sub½](Cl)[sub½]∙H[sub2]O, M = Co; 2a(PF[sub6])[sub½](Cl)[sub½]∙H[sub2]O, M = Cr), respectively, upon addition of KPH[sub6]. The structures of 1(PF[sub6])[sub½](CI)[sub½]∙H[sub2]O and 2(PF[sub6])[sub½](CI)[sub½]∙H[sub2]O have been determined by X-ray crystallography. Octahedral 1 and 1a are diamagnetic whereas 2 and 2a possess an S=¾ ground state. Cyclic voltammetry of 1a and 2a in CH[sub2]Cl[sub2] solution established that both species undergo a reversible one-electron oxidation generating the stable dications [Co[supII](tren)(tmsdt[sup∙])][sup2+] (S=½) and [Cr[supIII](tren)(tmsdt[sup∙])][sup2+] (S=1) where (tmsdt[sup∙])[sup1-] represents the π radical monoanion of oxidized (tmsdt)[sup2-]. The electrochemical oxidations are ligand centered processes. These dictations have been investigated by UV-vis and EPR spectroscopy an d density functional calculations using the B3LYP functional. The S,S'-coordinated benzene-1,2-dithiolate(1-) radical has been identified and ambiguously characterized. Comparison with the corresponding o-benzosemiquinonate(1-) complexes shows that the S,S'-coordinated benzene-1,2-dithiolate(1-) radical is a sulfur centered radical whereas its oxygen containing analogue carries ∼65% of the spin density on the six-membered ring. [ABSTRACT FROM AUTHOR]

From the reaction mixture of 3,6-di-tert-butylcatechol, H2[3,6Lcat], [CrCI3(thf)3], and NEt3 in CH3CN in the presence of air, the neutral complex [CrIII(3,6L·sq)3] (S = 0) (1) was isolated. Reduction of 1 with [Co(Cp)2] in CH2CI2 yielded microcrystals of [Co(Cp)2)[CrIII(3,6L·sq)2(3,6Lcat)] (S = 1/2) (2) where (3,6L·sq)1- is the π-radical monoanionic o-semiquinonate of the catecholate dianion (3,6Lcat)2-. Electrochemistry demonstrated that both species are members of the electron-transfer series [Cr(3,6LO,O)]z (z = 0, 1-, 2-, 3-). The corresponding tris(benzo-1,2-dithiolato)chromium complex [N(n-Bu)4][CrIII(3,5L·s,s)2(3,5LS,S)] (S = 1/2) (3) has also been isolated; (3,5LS,S)2- represents the closed-shell dianion 3,5-di-tert-butylbenzene-1,2-dithiolate(2-), and (3,5L·S,S)1- is its monoanionic < radical. Complex 3 is a member of the electron-transfer series [Cr(3,5LS,S)3]z (z = 0, 1-, 2-, 3-). It is shown by Cr K-edge and S K-edge X-ray absorption, UV-vis, and EPR spectroscopies, as well as X-ray crystallography, of 1 and 3 that the oxidation state of the central Cr ion in each member of both electron-transfer series remains the same (+III) and that all redox processes are ligand-based. These experimental results have been corroborated by broken symmetry density functional theoretical calculations by using the B3LYP functional. [ABSTRACT FROM AUTHOR]

The reaction of 3 equiv of the ligand 2-mercapto-3,5-di-tert-butylaniline, H2[LN,S], or 3,5-di-tert-butyl-1,2-benzenedithiol, H2[LS,S], with 1 equiv of [MoO2(acac)2] or WCI6 (acac = acetonylacetate(1-)) in methanol or CCI4 afforded the diamagnetic neutral complexes [MoV(LN,S)2(L*N,S)]0 (1), [MoV(LS,S)2(L*S,S)1 (2), and (WV(LS,S)2(L*S,S)] (3), where (L*N,S)- and (L*S,S)- represent monoanionic π-radical ligands (Srad = 1/2), which are the one-electron oxidized forms of the corresponding closed-shell dianions (LN,S)2- and (LS,S)2-. Complexes 1-3 are trigonal-prismatic members of the electron-transfer series [ML3]z (z = 0, 1-, 2-). Reaction of 2 and 3 with [N(n-Bu)4](SH) in CH2Cl2 under anaerobic conditions afforded paramagnetic crystalline [N(n-Bu)4](MoV(LS,S)3] (4) and [N(n-Bu)4][WV(LS,S)3] (5). Complexes 1-5 have been characterized by X-ray crystallography. S K-edge X-ray absorption and infrared spectroscopy prove that a π-radical ligand (L*S,S)- is present in neutral 2 and 3, whereas the monoanions [MV(LS,S)3]- contain only closed-shell dianionic ligands. These neutral species have previously been incorrectly described as [MVI(L)3)0 complexes with a MoVI or WVI (d0) central metal ion; they are, in fact MV (d¹) (M = Mo, W) species: [MoV(LS,S)2(L*S,S)] and [WV(LS,S)2(L*S,S)] with a diamagnetic ground state St = 0, which is generated by intramolecular, antiferromagnetic coupling between the MV (d¹) central ion (SM = 1/2) and a ligand π radical (L*S,S) (Srad = 1/2). [ABSTRACT FROM AUTHOR]

The reaction of 2 equiv of the bulky ligand N,N′-bis(3,5-di-tert-butylphenyl)-1,2-phenylenediamine, H2[3LPDI], excess triethylamine, and 1 equiv of M(CH3CO2)2•4H2O (M = Ni, Co) in the presence of air in CH3CN/CH2CI2 solution yields violet-black crystals of [NiII(3LISQ)2] CH3CN (1) or violet crystals of [Co(3L)2] (3). By using Pd(CH3CO2)2 as starting material, green-blue crystals of [PdII(3LISQ)2]•CH3CN (2) were obtained. Single-crystal X-ray crystallography revealed that 1 and 3 contain (pseudo)tetrahedral neutral molecules [M(3L)2] (M = Ni, Co) whereas in 2 nearly square planar, neutral molecules [PdII(3LISQ)2] are present. Temperature-dependent susceptibility measurements established that 1 and 2 are diamagnetic (S = O) whereas 3 is paramagnetic with an S = 3/2 ground state. It is shown that 1 contains two π radical benzosemiquinonate(1-)-type monoanions, ((3LISQ)1-•, Stad = ½), and a central Ni(II) ion (d8; S = 1) which are antiferromagnetically coupled yielding the observed St = 0 ground state. This result has been confirmed by broken symmetry DFT calculations of 1. In contrast, the St = 3/2 ground state of 3 is more difficult to understand: the two resonance structures [CoIII(3LISQ)(3LPDI)] ⃡ [CoII(3LPDI)(3LIBQ)] might be invoked (for tetrahedral [CoII(3LISQ)2] containing an SCo = 3/2 with two antiferromagnetically coupled π-radical ligands an St = ½ is anticipated). Complex 2 is diamagnetic (S = O) containing a PdII ion (d8, SPd = 0 in an almost square planar ligand field) and two antiferromagnetically coupled ligand radicals (Srad = ½). The electrochemistry and spectroelectrochemistry of 1, 2, and 3 have been studied, and electron-transfer series comprising the species [M(L)2]I (z = 2+, 1+, 0, 1-, 2-) have been established. All oxidations and reductions are ligand centered. [ABSTRACT FROM AUTHOR]

Dinickel(II) complexes of the ligands N,N′-di-p-anisylformamidinate (DAniF) and N,N′,N″-triphenylguanidinate (TPG) have been synthesized and crystallographically characterized, along with their one-electron-oxidized analogues. In both systems, the Ni-Ni distances become shorter by ~0.1 Å upon oxidation, in accord with the proposal that the resulting Ni25+ complexes are appropriately described as having one electron removed from a metal-based σ* orbital and an overall Ni-Ni bond order of 1/2. Although conventional DFT calculations on the model compounds Ni2(HNCHNH)4 and [Ni2(HNCHNH)4]+ appear to predict that the lowest energy state of the latter species would have one unpaired electron in an essentially ligand-based orbital. A single-point calculation of Ni2(DAniF)4 employing the geometry of its crystal structure with the full ligand included reveals a reversal of the previously predicted order of the HOMO and HOMO-1, and suggests that the unpaired electron in [Ni2(DAniF)4]+ is in a metal-based orbital of σ* symmetry. This is verified by the axial EPR spectrum of the compound in solution. The compound Ni2(DAniF)4 shows an unexpectedly rich cyclic voltammogram with four stepwise reversible oxidation waves. Coulometric experiments show that the doubly oxidized species has a significant lifetime at -25 °C, and by spectroelectrochemistry, its UV-vis spectrum was recorded. We propose that this species contains a Ni26+ core with a single Ni-Ni σ bond. [ABSTRACT FROM AUTHOR]

Oxidative cyclodehydrogenation is an important process in the formation of the new graphene, N-½HSB 2. This heteropolyaromatic results from the FeCl3-catalyzed oxidative cyclodehydrogenation of 1,2-dipyrimidyl-3,4,5,6-tetra(4-tert-butylphenyl)benzene. Three new C-C bonds are formed that lock the two pyrimidines in a molecular platform comprising eight fused aromatic rings flanked by two remaining "uncyclized" phenyl rings. Mechanistically intriguing is the fact that N-HSB 1, the product of six C-C bond fusions, is co-synthesized with its "half-cyclized" daughter in this reaction. 1 and 2 have the same bidentate N-atom arrangement. This facilitates formation of the heteroleptic Ru(II) complexes, [Ru(bpy)2(2)](PF6)2 4 and [Ru(bpy)2(1)](PF6)2 3, which differ in the size and planarity of their aromatic ligands. The new ligand 2 and its complex 4 are characterized by ¹H NMR, IR, ESI-MS, and accurate mass methods. 2 exhibits photophysical properties that are consistent with a reduction of the π/π* framework, a concomitant increase in the energy of the LUMO, and a blue-shift of the solvent-dependent fluorescence (λem = 474 nm, &#x03D5;F = 0.55, toluene) as compared to its parent. Complex 4 absorbs throughout the visible region and borders on near-IR emitter character, exhibiting a slightly blue-shifted ³MLCT emission (868 nm, CH3CN) as compared to that of [Ru(bpy)2(1)](PF6)2 3 (880 nm, CH3CN). Electrochemical analyses permit further elucidation of the intermolecular interactions of 3 and 4. These and the concentration and temperature-dependent NMR spectra of 4 confirm it to be nonaggregating, a direct result of the two uncyclized and rotatable phenyl rings in 2. [ABSTRACT FROM AUTHOR]

Discusses the synthesis and characterization of mono-, di- and trinuclear manganese complexes. Antiferromagnetic electronic coupling between manganese atoms; Covalent linkage of a ruthenium unit to the manganese cluster.

Examines the synthesis and properties of a macrocyclic Ruthenium (Ru) III complex. Chemical and electrochemical oxidation of monoclear blue complex; Characteristics of dinoclular species and trinuclear species; Analysis on electro- and spectroelectrochemistry of macrocyclic ruthenium.

Presents a study of the tetranuclear complexes and the tetracyanoethene which were studied by a variable temperature susceptometry. Purpose of the study; Methodology used to conduct the study; Results of the study.