title: Indirect Magnetic Exchange between o-Iminosemiquinonate Ligands Controlled by Apical Substituent in Pentacoordinated Gallium(III) Complexes.
abstract: A number of pentacoordinated gallium complexes iSQ2GaR (1-7) (R = Et (1), Me (2), N3 (3), Cl (4), Br (5), I (6), NCS (7)) where iSQ is a radical anion of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone were synthesized, and crystalline samples of 1-7 were characterized using magnetic susceptibility measurements. The character of magnetic exchange interaction between spins of o-iminosemiquinonate radicals was found to be strongly influenced by the nature of the apical substituent. The antiferromagnetic coupling is predominant when the apical position is occupied by halogens or other tested inorganic anions, and the value of exchange interaction parameter varies from -99 to -176 K for R = I and NCS, respectively. In the case of alkyl groups the ferromagnetic exchange prevails and, as the result, the triplet ground state for pentacoordianted biradical compounds was observed. Compounds 1-7 demonstrate a biradical X-band EPR spectrum in frozen toluene matrix. The molecular structures of 4, 6, and 7 have been established by single-crystal X-ray analysis. A computational DFT UB3LYP/6-31G(d,p) study was performed on complexes 1-7 in order to understand the reason for changes in the magnetic behavior of the related diradical gallium compounds. The calculations showed that the magnetic behavior of the complexes with inorganic anions is conditioned by the presence of antiferromagnetic exchange channel formed as a consequence of overlapping between donor atomic orbitals of iminoquinone with π-orbitals of halogen atoms (4-6) or nitrogen atom (3, 7).
authors.affiliation: †G. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, Tropinina str. 49, Nizhny Novgorod 603950, Russian Federation.|‡Nizhny Novgorod State University, Gagarina ave. 23, Nizhny Novgorod 603950, Russian Federation.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Piskunov
authors.affiliation: †G. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, Tropinina str. 49, Nizhny Novgorod 603950, Russian Federation.
authors.forename: Irina V
authors.initials: IV
authors.lastname: Ershova
authors.affiliation: §International Tomography Center, Siberian Branch of the Russian Academy of Sciences, 3a Institutskaya str., 630090 Novosibirsk, Russian Federation.
authors.forename: Artem S
authors.initials: AS
authors.lastname: Bogomyakov
authors.affiliation: ⊥Southern Scientific Center of Russian Academy of Sciences, 41 Chehova Ave., 344006 Rostov on Don, Russian Federation.
authors.forename: Andrey G
authors.initials: AG
authors.lastname: Starikov
authors.affiliation: †G. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, Tropinina str. 49, Nizhny Novgorod 603950, Russian Federation.|‡Nizhny Novgorod State University, Gagarina ave. 23, Nizhny Novgorod 603950, Russian Federation.
authors.forename: Georgy K
authors.initials: GK
authors.lastname: Fukin
authors.affiliation: †G. A. Razuvaev Institute of Organometallic Chemistry of Russian Academy of Sciences, Tropinina str. 49, Nizhny Novgorod 603950, Russian Federation.|‡Nizhny Novgorod State University, Gagarina ave. 23, Nizhny Novgorod 603950, Russian Federation.
authors.forename: Vladimir K
authors.initials: VK
authors.lastname: Cherkasov