Substituent dependent topologies in cobalt isophthalate coordination polymers with bis(pyridylmethyl)piperazine coligands

Article abstract of DOI:10.1016/j.ica.2011.03.009

Divalent cobalt coordination polymers containing bis(4-pyridylmethyl) piperazine (4-bpmp) or bis(3-pyridylmethyl)piperazine (3-bpmp) ligands and 5-substituted isophthalate ligands have been hydrothermally prepared and structurally characterized by single-crystal X-ray diffraction. [Co(OHip)(4-bpmp)]_n (1, OHip = 5-hydroxyisophthalate) manifests a (4,4) grid 2D coordination polymer structure, with anti-syn bridged {Co ₂(OCO)₂} dimers serving as connecting nodes. Similar dinuclear {Co₂(OCO)₂} clusters are evident in [Co(OMeip)(4-bpmp)]_n (2, OMeip = 5-methoxyisophthalate). However, the lack of hydrogen-bonding capability of the methoxy substituent promotes formation of a rarer 6-connected (3,6) triangular net. {[Co(H₂O) ₄(H₂3-bpmp)](NO₂ip)₂·6H ₂O}_n (3, NO₂ip = 5-nitroisophthalate) possesses cationic [Co(H₂O)₄(H₂3-bpmp)]n4n+ chains connected into a supramolecular lattice by unligated NO₂ip dianions and water molecules of crystallization. The variable temperature magnetic susceptibility behavior of 1 and 2 is ascribed to cooperation between single-ion effects and weak ferromagnetic superexchange.