Coordination Driven Self-Assembly in Co(II) Coordination Polymers Displaying Unprecedented Topology, Water Cluster, Chirality, and Spin-Canted Magnetic Behavior

The
present work reports facile synthesis, full characterization,
and architectural diversity of seven Co­(II) coordination polymers,
namely, [{Co­(H2MBP)2­(12-CDA)}·​CH3OH]∞ (1), [{Co­(H2MBP)­(12-CDA)­(H2O)}]∞ (2), [{Co0.5(H2MBP)­(14-CDA)0.5}·​(H2O)2.5]∞ (3), [{Co­(H2MBP)­(14-CDA)­(H2O)2}]∞ (4), [{Co­(H2MBP)­(13-ADA)0.5}]∞ (5), [{Co­(H2MBP)2­(135-CTA)­(H2O)}­(H2O)3.5]∞ (6), and [{Co2(μ2O)­(H2MBP)3­(1245-CHA)}­(H2O)12]∞ (7), derived from a 4,4′-methylene
bispyrazole (H2MBP) ligand and various flexible dicarboxylate
coligands. The type of alicyclic flexible carboxylate coligand used
in the synthesis and its coordination to the metal center play a key
role in controlling the dimensionality and topology of the frameworks.
Topological analysis of the simplified nets reveals that 1 and 3 possess a 4-connected sql topology, 2 features a 3-connected uninodal hcb topology, 5 contains a 3D cds topology, and 7 possesses an unprecedented new 3D topology. Interestingly, a well-resolved
1D water chain is found within 3 and the presence of
a heptanuclear water cluster assisted via a free carboxylate group
is observed in 6. Chirality associated with 5 has been supported by solid-state CD spectra, and variable-temperature
magnetic studies indicate that 7 exhibits canted magnetic
coupling between the carboxylate bridged Co­(II) ions.