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

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 {Co2(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)2·6H2O}n (3, NO2ip = 5-nitroisophthalate) possesses cationic [ Co ( H 2 O ) 4 ( H 2 3 -bpmp ) ] n 4 n + 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.