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The treatment of the 90 degree angular precursor trans-[Ru[Cl.sub.2][(dmso-S).sub.4]] with an equivalent amount of the linear and rigid pyrazine (pyz) linker has produced the molecular triangle [[{trans,cis-Ru[Cl.sub.2][(dmso-S).sub.2]([mu]-pyz)}.sub.3]] instead of the molecular squares. The results have shown that the entropically favored molecular triangles are preferred over the expected molecular squares with metal corner fragments that have favored [N.sub.pyz]-M-[N.sub.pyz] angles narrower than 90 degrees due to the presence of ancillary ligands.

The syntheses and characterization of the crystal and magnetic structures of the mixed-anion coordination polymer Cu(HC[O.sub.2])(N[O.sub.3])(pyz) (where pyz = pyrazine) was characterized. The Cu(HC[O.sub.2])(N[O.sub.3])(pyz) undergoes a long-range magnetic ordering due to the one-dimensional Cu[(N[O.sub.3]).sub.2](pyz) and three-dimensional Cu[(HC[O.sub.2]).sub.2](pyz) compounds which display linear chain antiferromagnetism with no long-range magnetic ordering down to 2 K.

A series of pyrazine (pz) complexes containing cis-(NH3)(sub 2)Pt(super II), (tmeda)Pt(super II), and trans-(NH3)(sub 2)Pt(super II) entities are synthesized and characterized by X-ray crystallography and/or (super 1)H NMR spectroscopy. The formation of the cyclic tetramer [Pt(super II)](sub 4) complex conforms to expectations of the molecular library approach, which predicts a molecular box when two ditopic building blocks with 90 degree and 180 degree angles, respectively, are combined.

Several experimental and first-principles studies are conducted to explain the 1D to 3D magnetic transformation taking place in the copper pyrazine dinitrate S = 1/2 antiferromagnetic crystal. The magnetic susceptibility and heat capacity curves of the crystal are shown to remain unchanged with the spin and magnetic chains.

The synthesis and physicochemical properties of newly obtained palladium(II) complexes of the free-base tetrakis(2,3-(5,6-di-2-pyridylpyrazino)porphyrazine], [Py.sub.8]TPyzPz[H.sub.2] is described. The results provide insights into the behavior of palladium(II) species as photosensitizers for the production of singlet oxygen.

The report presents the structural, magnetic and surface studies of the supramolecular self-assembled polynuclear complexes, including 2,6-picolyldihydrazone (tritopic and pentatopic) and 3,6-pyridazinedihydrazone (tetratopic) cores.

Two flexible thioether-containing heterocyclic ligands bis(2-pyrazylmethyl)sulfide and 2-benzylsulfanylmethylpyrazine have arene rings with changing [pi]-acidities that are used to probe anion-[pi] binding in five 1-dimensional (1-D) coordination polymers formed from the metal salts. The comparison between the polymers formed with these ligands has shown that only the more [pi]-acidic ring is involved in the anion-[pi] interactions.

The wave function-based method namely the CASSCF/MS-CASPT2 method was used to study the Creutz-Taube complex [[[(N[H.sub.3]).sub.5]-Ru-pyrazine-Ru-[(N[H.sub.3]).sub.5]].sup.5+]. The g-factors of the CT ion are shown to be independent of the coupling between the centers and to be the same as in the monomer, because the coupling acts in symmetry different from the one of the ground state.

The reaction of the electronically unsaturated tetrahedral cluster [[Re.sub.4][([mu].sub.3]-H).sub.4][(CO).sub.12] with pyridazine (pydz) has provided the main initial product the tetranuclear cluster [[Re.sub.4][([mu]-H).sub.4]([mu].pydz)[(pydz).sub.2][(CO).sub.12]], with 64 ve and four hydrogen-bridged metal-metal interactions, with a spiked-triangle geometry. The quantum yields are [[Re.sub.4][([mu].sub.3]-H).sub.4][(CO).sub.12] order of magnitude higher for the squares than for the dinuclear complexes.