One Dimensional Chain and Ribbon Cobalt-Dioxolene Coordination Polymers: A New Valence Tautomeric Compound

The combination of the divergent tetrakis-pyridyl linking ligand 1,2,4,5-tetra(4-pyridyl)benzene (tpb) with cobalt and 3,5-di-tert-butyldioxolene (3,5-dbdiox) ligands has afforded the complexes [Co(3,5-dbdiox)(2)(tpb)](infinity) (1) and [Co(3,5-dbdiox)(2)(tpb)(0.5)](infinity) (2). Both species are 1D coordination polymers that crystallize as the hydrated compounds 1 center dot 3H(2)O and 2 center dot 9H(2)O. While the tpb in complex 1 is a 2-connecting linker, affording a conventional 1D chain, the tpb in 2 is a 4-connecting linker, giving rise to a ribbon topology. Single crystal X-ray structural analysis indicates that 1 center dot 3H(2)O and 2 center dot 9H(2)O both possess the {Co-III(3,5-dbcat)(3,5-dbsq)} (3,5-dbcat = 3,5-di-tert-butylcatecholate; 3,5-dbsq = 3,5-di-tert-butyl-semiquinonate) charge distribution at 100 or 130 K, respectively. Variable temperature magnetic susceptibility studies of partially dehydrated 1 center dot H2O indicate a thermally induced valence tautomeric (VT) transition above 300 K.