Co(II) coordination polymers derived from α,α-disubstituted analogues of zoledronic acid and 4,4'-bipyridine: Synthesis, structures and characterization

Abstract Two isomorphous Co(II) coordination polymers were hydrothermally prepared using analogues of zoledronic acid functionalized at Cα carbon by a cyclobutane ring (H4cbtZol) or methyl groups (H4dmtZol), 4,4'-bipyridine (4,4'-bpy) and cobalt(II) acetate. The resulting crystalline materials, Co3(HcbtZol)2(4,4'-bpy)(H2O)4⋅10H2O (1) and [Co3(HdmtZol)2(4,4’-bpy)(H2O)4]·0.2NaOH⋅9.8H2O (2), were analysed by means of single-crystal X-ray diffraction, IR spectroscopy and thermal techniques. Both 1 and 2 feature similar zig-zag [Co3(HcbtZol/HdmtZol)2(H2O)4] chains with crystallographically distinct Co1 and Co2 in slightly distorted octahedral geometries, assembled into 2D coordination layers by 4,4’-bpy. In both compounds, 3D supramolecular architecture is sustained by hydrogen bonds involving water of crystallization filling the cavities inside the network. Furthermore, in 2, an additional support provide Na1 ions linked by phosphonate O atoms and molecules of coordinated and crystallization water. The vibrational spectra of both compounds are in good agreement with crystal data. Similarities in chain architectures of 1 and 2 and previously reported 1D M3(HL)2(H2O)6⋅6H2O (M = Co, Ni, HL3- = HdmtZol3-, HcbtZol3-) coordination polymers are discussed and differences in their thermal behavior explained in term of different 3D architectures.