Low pH constructed Co(ii) and Ni(ii) 1D coordination polymers based on C α -substituted analogues of zoledronic acid: structural characterization, and spectroscopic and magnetic properties

• Published in: RSC advances Vol. 9; no. 54; pp. 31497 - 31510
• Main Authors: Rojek, Tomasz, Goldeman, Waldemar, Ślepokura, Katarzyna, Duczmal, Marek, Wojciechowska, Agnieszka, Matczak-Jon, Ewa
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 07-10-2019; The Royal Society of Chemistry
• Subjects: Antiferromagnetism; Architecture; Bridges; Chemistry; Coordination compounds; Coordination polymers; Couplings; Crystallography; Cyclobutane; Cyclopropane; Ferromagnetism; Heat exchange; Infrared spectroscopy; Magnetic properties; Single crystals; Structural analysis
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/c9ra05673d

Three novel coordination compounds based on α,α-disubstituted analogues of zoledronic acid with a cyclopropane (cpp) or cyclobutane (cbt) ring on the C
carbon, isomorphous [Co(H
cppZol)(H
O)]·H
O (1a), [Ni(H
cppZol)(H
O)]·H
O (1b) and [Co(H
cbtZol)(H
O)]·H
O (2a), were synthesized under hydrothermal conditions at low pH. Single-crystal X-ray diffraction analysis revealed that all the compounds had a 1D double zig-zag chain architecture with an 8 + 8 ring motif formed by alternately arranged symmetrical (-O-P-O-)
bridges linking equivalent octahedral metal centres. Both the ligand coordination mode and chain architecture displayed by 1a, 1b and 2a are unique among 1D [M(H
L)(H
O)
]·
H
O coordination polymers based on nitrogen-containing bisphosphonates reported so far. All the compounds exhibit similar decomposition pathways upon heating with thermal stabilities decreasing in the order 1b > 1a > 2a. The IR spectra revealed that lattice water release above 227, 178 and 97 °C, respectively, does not change the chain architecture leaving them intact up to
320, 280 and 240 °C. Magnetic behaviour investigations indicated that 1a, 2a and 1b exhibit weak alternating antiferromagnetic-ferromagnetic exchange interactions propagated between the magnetic centres through double (-O-P-O-)
bridges. The boundary between antiferro- and ferromagnetic couplings for the Co-O⋯O-Co angle in 1a and 2a was estimated to be
80°. This value is also applicable for recently reported [M
(HL)
(H
O)
]·6H
O (M = Co, Ni) complexes based on α,α-disubstituted analogues of zoledronic acid and can be used to the explain magnetic behaviour of 1b.