Coordination of the 2,6-bis(8′-quinolinyl)pyridine (bqp) ligand to a cobalt (Co) core and its influence to electron spin and configuration on the structures and properties of the resulting complexes has been investigated. The homoleptic complexes Co(mer-bqp-κ3N,N′,N″)]2+ (1) and [Co(mer-bqp-κ3N,N′,N″)]3+ (2) were prepared and characterized. X-ray structure determinations of complexes 1 and 2 revealed twisted, near-octahedral arrangements relative to the cobalt center. The magnetic data for 1 is typical of those for distorted octahedral (i.e., D4h symmetry) high-spin d7 species despite the near-ideal octahedral coordination of the bqp ligand around the Co(II) core. Electronic spectra for 1 and 2 have been investigated and assigned. Both complexes exhibit intense π–π∗ bqp ligand centered transitions in the UV region and low intensity mixed charge transfer transitions in the visible region. Neither complex strongly absorbs in visible spectral region. The electrochemistry of these compounds has been studied and compared to that of similar cobalt terpyridine compounds. A metal-centered Co2+/3+ redox wave and ligand-based reduction processes were observed for 1 and 2 in acetonitrile. The metal-centered redox potentials were reversible with potentials more positive than comparable cobalt-terpyridine complexes. Density functional theory (DFT) calculations of the electronic and ground state properties are in good agreement with the experimental data.

A homologous series of meridionally-coordinated tridentate 2,2':6',2''-terpyridine Re(I) dicarbonyl complexes have been prepared and investigated. The complexes mer,cis-[Re(tpy-κ(3)N)(CO)2(L)](n) (L = Cl(-) (1), OSO2CF3(-) (2), NCCH3 (3), CN(-) (4), NC5H5 (5), PMe3 (6), PEt3 (7), PPh3 (8), P(OMe)3 (9) and P(OEt)3 (10); n = 0 or +1) have been synthesized and characterized by elemental analysis, (1)H NMR and infrared spectroscopy. The electrochemistry of these compounds has been studied and compared to that of other known rhenium compounds using an electrochemical parameterization model. Cyclic voltammetry measurements have shown that the first oxidation of the complexes varies systematically in potential as the ligand L is altered. Many of these one-electron oxidations occur at lower potentials compared to more familiar bidentate diimine Re(I) tricarbonyl complexes. A correlation exists between CO, a strong π-acidic ligand, and deviations of the observed reduction potentials from the calculated values. Many of the complexes absorb light throughout a significant portion of the visible spectrum. Two of these complexes, mer,cis-Re(tpy-κ(3)N)(CO)2Cl (1) and mer,cis-Re(tpy-κ(3)N)(CO)2CN (4), absorb light throughout the entire visible spectrum. Low temperature emission spectra were obtained for the compounds mer,cis-Re(tpy-κ(3)N)(CO)2Cl (1) and mer,cis-[Re(tpy-κ(3)N)(CO)2(P(OEt)3)](+) (10) at 77 K in a 4 : 1 methanol-ethanol glass matrix and give metal-to-ligand charge transfer ((3)MLCT) luminescence. Density functional theory (DFT) calculations of the electronic structure are in good agreement with the experimental data.