title: Lattice-Modulated Phase Transition Coupled with Redox-Isomeric Interconversion of o-Semiquinone-Catecholato into Bis(o-semiquinonato) Cobalt Complexes.
abstract: Two redox-isomeric (valence tautomeric) complexes (2,2'-bpy)Co(3,6-DBSQ)2 (1) and (1,10-phen)Co(3,6-DBSQ)2 (2) (where 2,2'-bpy = 2,2'-dipyridine; 1,10-phen = 1,10-phenanthroline; 3,6-DBSQ = 3,6-di-tert-butyl-benzosemiquinone-1,2) reveal phase transitions that accompany redox-isomeric interconversions of semiquinone-catecholato isomer into a bis-(semiquinonato) one. Phase transitions differ one from another by thermodynamic parameters (transition temperature and interval, enthalpy, and entropy). Complexes 1 and 2 have the same crystal system and space group, and they form solid solutions with any molar ratio. The number of solid solutions with the molar ratios of 2:1, 1:1, 1:2, 1:4, 1:8, and 1:16 of 1 per 2, respectively, were obtained. Product with 1:1 ratio was studied by precise calorimetry, by variable-temperature magnetic susceptibility, and by X-ray structural analysis. All solid solutions were investigated by means of differential scanning calorimetry. Each solid solution possesses phase transition whose parameters depend on its composition. Transition temperature and enthalpy gradually grow with increasing of molar fraction of 1. The diagram "enthalpy-composition" is linear, whereas phase diagram "transition temperature-composition" is the bent-up arc.
authors.affiliation: †G. A. Razuvaev Institute of Organometallic Chemistry of RAS, 49 Tropinina str., GSP-445, 603950 Nizhny Novgorod, Russia.|‡Lobachevsky State University of Nizhny Novgorod Gagarina av. 23/5, Nizhny Novgorod, 603950 Russia.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Bubnov
authors.affiliation: †G. A. Razuvaev Institute of Organometallic Chemistry of RAS, 49 Tropinina str., GSP-445, 603950 Nizhny Novgorod, Russia.
authors.forename: Nina A
authors.initials: NA
authors.lastname: Skorodumova
authors.affiliation: †G. A. Razuvaev Institute of Organometallic Chemistry of RAS, 49 Tropinina str., GSP-445, 603950 Nizhny Novgorod, Russia.
authors.forename: Alla V
authors.initials: AV
authors.lastname: Arapova
authors.affiliation: ‡Lobachevsky State University of Nizhny Novgorod Gagarina av. 23/5, Nizhny Novgorod, 603950 Russia.
authors.forename: Natalia N
authors.initials: NN
authors.lastname: Smirnova
authors.affiliation: †G. A. Razuvaev Institute of Organometallic Chemistry of RAS, 49 Tropinina str., GSP-445, 603950 Nizhny Novgorod, Russia.
authors.forename: Maxim A
authors.initials: MA
authors.lastname: Samsonov
authors.affiliation: †G. A. Razuvaev Institute of Organometallic Chemistry of RAS, 49 Tropinina str., GSP-445, 603950 Nizhny Novgorod, Russia.|‡Lobachevsky State University of Nizhny Novgorod Gagarina av. 23/5, Nizhny Novgorod, 603950 Russia.
authors.forename: Georgy K
authors.initials: GK
authors.lastname: Fukin
authors.affiliation: †G. A. Razuvaev Institute of Organometallic Chemistry of RAS, 49 Tropinina str., GSP-445, 603950 Nizhny Novgorod, Russia.|‡Lobachevsky State University of Nizhny Novgorod Gagarina av. 23/5, Nizhny Novgorod, 603950 Russia.
authors.forename: Vladimir K
authors.initials: VK
authors.lastname: Cherkasov
authors.affiliation: †G. A. Razuvaev Institute of Organometallic Chemistry of RAS, 49 Tropinina str., GSP-445, 603950 Nizhny Novgorod, Russia.|‡Lobachevsky State University of Nizhny Novgorod Gagarina av. 23/5, Nizhny Novgorod, 603950 Russia.
authors.forename: Gleb A
authors.initials: GA
authors.lastname: Abakumov