Bipyridine: the most widely used ligand. A review of molecules comprising at least two 2,2'-bipyridine units.

The ligand 2-anilino-4,6-di-tert-butylphenol and its 2-(3,5-dichloroanilino)-4,6-di-tert-butylphenol analogue react in CH3CN or CH3OH solutions with divalent transition metal ions in the presence of air and triethylamine. Depending on the metal:ligand ratio (1:1, 1:2, or 1:3) and the presence (or absence) of the cyclic amine 1,4-dimethyl-1,4,7-triazacyclononane (dmtacn), the following complexes have been isolated as crystalline solids:  [CoIII(LISQ)3] (1); [CuII(dmtacn)(LISQ)]PF6 (2); [CuII(LISQ)2] (3); [NiII(LISQ)2] (4a); [NiII(ClLISQ)2] (4b); [PdII(LISQ)2] (5). (LISQ)- represents the monoanionic o-iminobenzosemiquinonate radical (Srad = 1/2). Compounds 1−5 have been characterized by single-crystal X-ray crystallography at 100(2) K. For all complexes it is unambiguously established that the O,N-coordinated o-iminobenzosemiquinonato(1−) ligand is present. Complexes 3, 4b, and 5 are square planar molecules which possess an St = 1/2, 0, and 0 ground state, respectively, as was established by 1H NMR and EPR ...

Electronic Structure of Bis(o-iminobenzosemiquinonato)metal Complexes (Cu, Ni, Pd). The Art of Establishing Physical Oxidation States in Transition-Metal Complexes Containing Radical Ligands

https://escholarship.org/content/qt1kp1t47g/qt1kp1t47g.pdf?t=o0hb1w

Radical ligand-containing single-molecule magnets

Molecular Magnetism: A basis for new materials

Valence tautomeric complexes combine redox-active ligands and transition metal ions with two or more accessible oxidation states, exhibiting two nearly degenerated electronic states with localized electronic structures Charge distribution in such electronic isomers has an appreciable sensitivity to the environment so an external perturbation, like photons, temperature and/or pressure, may lead to an intramolecular electron transfer between both redox active units and therefore to a reversible interconversion between the two degenerated electronic states Moreover, since each electronic isomer exhibits different optical, electronic and/or magnetic properties, these complexes are being proposed as candidates for future use in molecular electronic devices and switches Most of the valence tautomeric complexes reported thus far are based on quinone or quinone-type ligands with a series of transition metal ions such as Co, Cu, Ni and Mn Nevertheless, in the last few years, the number of electroactive ligands identified to be active in valence tautomeric complexes is being expanded by including new radical ligands such as polychlorotriphenylmethyl, phenoxyl or tetraphenylporphyrin radicals (© Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2005)

Andrea Dei

Papers

Controlling Valence Tautomerism of Cobalt Complexes Containing the Benzosemiquinone Anion as Ligand

Superexchange through orthogonal magnetic orbitals in π-type organic triradicals : quartet ground state in Ga(3,5-dtbsq)3

Kontrollierte valenztautomerie bei cobalt-komplexen mit semichinon-anion-liganden

Superaustausch über orthogonale magnetische Orbitale in organischen Triradikalen vom π‐Typ: Quartettgrundzustand in [Ga3,5‐dtbsq)3]