Synthesis, structure and properties of Ni(II) coordination polymer based on α,α-dimethyl substituted zoledronate

• Published in: Polyhedron Vol. 141; pp. 44 - 51
• Main Authors: Rojek, Tomasz, Goldeman, Waldemar, Ślepokura, Katarzyna, Duczmal, Marek, Wojciechowska, Agnieszka, Matczak-Jon, Ewa
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-02-2018
• Subjects: Coordination polymers; Magnetic properties; Thermal stability; Transition metals; X-ray crystallography; Zoledronic acid; X-ray crystallography; Zoledronic acid; Coordination polymers; Transition metals; Thermal stability; Magnetic properties
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2017.11.018

Novel 1D coordination polymer based on α,α-dimethyl substituted zoledronate with spectroscopically and magnetically distinct Ni1 and Ni2 centers. Temperature to which partly dehydrated complex retains its architecture was determined. The magnetic susceptibility measurements revealed antiferromagnetic Ni1⋯Ni2 interactions within trimers and ferromagnetic Ni2⋯Ni2 intertrimers coupling.
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The reaction of α,α-dimethyl substituted derivative of zoledronic acid with Ni(II) afforded 1D coordination polymer, Ni3(HL)2(H2O)6·6H2O (1). The title compound possess crystallographically and spectroscopically distinct Ni1 and Ni2 centers characterized by tetragonality distortion parameter T = 0.97 and 1.04, respectively, and is isomorphous with recently reported Co3(HL)2(H2O)6·6H2O complexes based on α,α-dimethyl and cyclopropyl substituted zoledronate derivatives.
Detailed analysis of thermal stability of 1 revealed that partly dehydrated [Ni3(HL)2(H2O)3] still retains its architecture and structural integrity of coordinated ligands. Exploring supramolecular interactions that build up the crystal of 1 and related Co(II) complexes allowed a conclusion that distinct dehydration pathways observed for each compound may be correlated with subtle differences in 3D crystals packing. Ni2(P2O7) salt was identified as the major final product of thermolysis of 1.
The magnetic properties of 1 analyzed in term of a spin-1 Heisenberg Ni2Ni1Ni2 trimer chains model revealed antiferromagnetic Ni1⋯Ni2 interactions within the trimers (J1 = −7.32 cm−1) and ferromagnetic Ni2⋯Ni2 intertrimers coupling (ΘW = 1.72 K). Furthermore, different values of the axial zfs D parameters and the g-factors were assigned to the Ni1 and Ni2 centers.