Synthesis, crystal polymorphism and spin crossover behavior of adamantylboron-capped cobalt(II) hexachloroclathrochelate and its transformation into the CoIIICoIICoIII-bis-macrobicyclic derivative

Alexander S Belov; Valentin V Novikov; Anna V Vologzhanina; Alexander A Pavlov; Artem S Bogomyakov; Yan V Zubavichus; Roman D Svetogorov; Genrikh E Zelinskii; Yan Z Voloshin

doi:10.1039/d2dt03300c

Synthesis, crystal polymorphism and spin crossover behavior of adamantylboron-capped cobalt(II) hexachloroclathrochelate and its transformation into the Co^IIICo^IICo^III-bis-macrobicyclic derivative

Dalton Trans. 2023 Jan 3;52(2):347-359. doi: 10.1039/d2dt03300c.

Authors

Alexander S Belov^{1

2}, Valentin V Novikov³, Anna V Vologzhanina², Alexander A Pavlov^{2

4}, Artem S Bogomyakov⁵, Yan V Zubavichus⁶, Roman D Svetogorov⁷, Genrikh E Zelinskii^{1

2}, Yan Z Voloshin^{1

2}

Affiliations

¹ Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, 31 Leninsky pr., 119991 Moscow, Russia. voloshin@ineos.ac.ru.
² Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences, 28-1 Vavilova st., 119334 Moscow, Russia.
³ Moscow Institute of Physics and Technology, 141700 Moscow Region, Russia.
⁴ National Research University Higher School of Economics, 101000 Moscow, Russia.
⁵ International Tomography Center, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia.
⁶ Synchrotron Radiation Facility SKIF, G.K. Boreskov Institute of Catalysis of the Siberian Branch of the Russian Academy of Sciences, 1 Nikolskii pr., 630559 Koltsovo, Russia.
⁷ National Research Center Kurchatov Institute, 123182 Moscow, Russia.

PMID: 36511081
DOI: 10.1039/d2dt03300c

Abstract

Fast crystallization of the monoclathrochelate cobalt(II) intracomplex [Co(Cl₂Gm)₃(BAd)₂] (where Cl₂Gm^2- is a dichloroglyoxime dianion and BAd is an adamantylboron capping group, 1), initially obtained by the direct template condensation of the corresponding chelating α-dioximate and cross-linking ligand synthons on the Co²⁺ ion as a matrix, from benzene or dichloromethane afforded its structural triclinic and hexagonal polymorphs. Its prolonged recrystallization from dichloromethane under air atmosphere and sunlight irradiation unexpectedly gave the crystals of the Co^IIICo^IICo^III-trinuclear dodecachloro-bis-clathrochelate intracomplex [[Co^III(Cl₂Gm)₃(BAd)]₂Co^II] (2), the molecule of which consists of two macrobicyclic frameworks with encapsulated low-spin (LS) Co³⁺ ions, which are cross-linked by a μ₃-bridging Co²⁺ ion as a bifunctional Lewis-acidic center. The most plausible pathway of such a 1 → 2 transformation is based on the photoinitiated radical oxidation of dichloromethane with air oxygen giving the reactive species. Cobalt(II) monoclathrochelate 1 was found to undergo a temperature-induced spin crossover (SCO) both in its solutions and in the solid state. In spite of the conformational rigidity of the corresponding quasiaromatic diboron-capped tris-α-dioximate framework, the main parameters of this SCO transition (i.e., its completeness and gradual character) are strongly affected by the nature of the used solvent (in the case of its solutions) and by the structural polymorphism of its crystals (in the solid state). In the latter case, the LS state (S = 1/2) of this complex is more thermally stable and, therefore, the cobalt(II)-centered 1/2 → 3/2 SCO is more gradual than that in solutions.