Structural investigation of one- and two-dimensional coordination polymers based on cobalt-bis(dioxolene) units and 1-hydroxy-1,2,4,5-tetrakis(pyridin-4-yl)cyclohexane

Abstract

The combination of cobalt, 3,5-di-tert-butyldioxolene (3,5-dbdiox) and 1-hydroxy-1,2,4,5-tetrakis(pyridin-4-yl)cyclohexane (tpch) yields two coordination polymers with different connectivities, i.e. a one-dimensional zigzag chain and a two-dimensional sheet. Poly[[bis(3,5-di-tert-butylbenzene-1,2-diolato)bis(1,5-di-tert-butyl-4-oxocyclohexa-2,5-dien-1-yl-3-olato)[μ₄-1-hydroxy-1,2,4,5-tetrakis(pyridin-4-yl)cyclohexane]cobalt(III)]-ethanol-water 1/7/5], {[Co₂(C₁₄H₂₀O₂)₄(C₂₆H₂₄N₄O)]·7C₂H₅OH·5H₂O}_n or {[Co₂(3,5-dbdiox)₄(tpch)}·7EtOH·5H₂O}_n, is the second structurally characterized example of a two-dimensional coordination polymer based on linked {Co(3,5-dbdiox)₂} units. Variable-temperature single-crystal X-ray diffraction studies suggest that catena-poly[[[(3,5-di-tert-butylbenzene-1,2-diolato)(1,5-di-tert-butyl-4-oxocyclohexa-2,5-dien-1-yl-3-olato)cobalt(III)]-μ-1-hydroxy-1,2,4,5-tetrakis(pyridin-4-yl)cyclohexane]-ethanol-water (1/1/5)], {[Co(C₁₄H₂₀O₂)₂(C₂₆H₂₄N₄O)]·C₂H₅OH·5H₂O}_n or {[Co(3,5-dbdiox)₂(tpch)]·EtOH·5H₂O}_n, undergoes a temperature-induced valence tautomeric interconversion.

Keywords: cobalt; crystal structure; metal-organic frameworks; one-dimensional zigzag chain; polypyridyl ligands; redox-active ligands; two-dimensional coordination polymer; valence tautomerism.