Valence-Tautomeric Interconversion in a Bis(dioxolene)cobalt Complex with Iminopyridine Functionalized by a TEMPO Moiety. Phase Transition Coupled with Monocrystal Destruction

Alexey A Zolotukhin; Michael P Bubnov; Alla V Arapova; Georgy K Fukin; Roman V Rumyantcev; Artem S Bogomyakov; Alexander V Knyazev; Vladimir K Cherkasov

doi:10.1021/acs.inorgchem.7b02597

Valence-Tautomeric Interconversion in a Bis(dioxolene)cobalt Complex with Iminopyridine Functionalized by a TEMPO Moiety. Phase Transition Coupled with Monocrystal Destruction

Inorg Chem. 2017 Dec 18;56(24):14751-14754. doi: 10.1021/acs.inorgchem.7b02597. Epub 2017 Nov 29.

Authors

Alexey A Zolotukhin¹, Michael P Bubnov¹, Alla V Arapova¹, Georgy K Fukin¹, Roman V Rumyantcev¹, Artem S Bogomyakov², Alexander V Knyazev³, Vladimir K Cherkasov¹

Affiliations

¹ G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences , 49 Tropinina Str., GSP-445, 603950 Nizhny Novgorod, Russia.
² International Tomography Center, Siberian Branch of the Russian Academy of Sciences , Institutskaya Str. 3a, Novosibirsk 630090, Russia.
³ Lobachevsky State University of Nizhny Novgorod , Gagarin Prospekt 23/2, 603950 Nizhny Novgorod, Russia.

PMID: 29185722
DOI: 10.1021/acs.inorgchem.7b02597

Abstract

Iminopyridine modified by TEMPO nitroxide was utilized for the synthesis of an octahedral bis(o-semiquinonato)cobalt complex. Variable-temperature magnetic susceptibility measurements detect a valence tautomeric transformation in the temperature range 200-300 K. A reproducible hysteresis loop of about 40 K width is observed on the magnetic moment temperature dependence in the transition region. Differential scanning calorimetry measurements confirm different temperatures of phase transitions accompanying a valence-tautomeric transformation upon heating and cooling. Attempts to study the structural changes associated with the valence-tautomeric transformation by single-crystal X-ray diffraction failed because of the crystal destruction taking place upon cooling from 220 K. The powder X-ray diffraction pattern indicated an essential change of the unit cell upon cooling from 240 K.