Bryan D. Koivisto

Magnetostructural studies of copper(II)–verdazyl radical complexes

The synthesis, structures, and magnetic properties of several Cu(II) complexes of verdazyl radicals are presented. Reactions of chelating verdazyl radicals with either CuCl2·2H2O or Cu(hfac)2·2H2O produced 1 ∶ 1 Cu ∶ verdazyl complexes with either chloride or hfac ancillary ligands. Structural characterization reveals that the CuCl2 complexes of N,N′-dimethyl-3-(2-pyridyl)-6-oxoverdazyl or N,N′-bis(isopropyl)-3-(2-pyridyl)-6-oxoverdazyl have pseudo-square pyramidal copper ions with verdazyl rings bound in equatorial positions, while the Cu(hfac)2 complex of N,N′-dimethyl-3-(N-methyl-2-imidazolyl)-6-oxoverdazyl is Jahn–Teller distorted pseudo-octahedral and has the verdazyl nitrogen axially bound. Variable temperature magnetic susceptibility studies reveal that equatorially bound verdazyls are strongly antiferromagnetically coupled, while the axially bound radicals are weakly ferromagnetically coupled. Intermolecular magnetic interactions are also an important component of the overall magnetism in these systems.

Derivatization of Bichromic Cyclometalated Ru(II) Complexes with Hydrophobic Substituents

The syntheses and physical properties of cyclometalated Ru(II) complexes containing a triphenylamine (TPA) unit bearing aliphatic groups are reported. Each member of the series consists of an octahedral Ru(II) center coordinated by a tridentate polypyridyl ligand and a tridentate cyclometalating ligand. One of the chelating ligands contains electron-deficient methyl ester groups, while a TPA unit is attached to the central ring of the adjacent chelating ligand through a thiophene bridge. This study builds on our previous work (Inorg. Chem. 2011, 50, 6019-6028; Inorg. Chem. 2011, 50, 5494-5508) by (i) outlining a synthetic protocol for installing aliphatic groups on the TPA substituents, (ii) examining the role that terminal -O-hexyl and -S-hexyl groups situated on the TPA have on the electrochemical properties, and (iii) demonstrating the potential benefit of installing the TPA on the neutral chelating ligand rather than the anionic chelating ligand. The results reported herein provide important synthetic advances for our broader goal of developing bis-tridentate cyclometalated Ru(II) complexes for light-harvesting applications.