Supramolecular interactions mediated conformational modulation of flexible linker leading to the isolation of a metallo-macrocycle in a polyoxometalate matrix: Hirshfeld surfaces and 2D fingerprint plots

Abstract

A novel polyoxometalate-based ion-pair compound, [Cu(1,4-bpimb)(H₂O)]₂[Mo₈O₂₆]·4H₂O (1), has been synthesized starting from the copper nitrate, flexible linker 1,4-bis[2-(2-pyridyl)imidazol-1-ylmethyl]benzene (1,4-bpimb) and sodium molybdate under hydrothermal conditions. The title compound was unambiguously characterized by single-crystal X-ray diffraction analysis, elemental analysis, IR spectroscopy, and thermogravimetric analysis, and bulk homogeneity has been proved by powder X-ray diffraction studies. The supramolecular interactions governed by the octamolybdate anion mediate the conformational modulation of the 1,4-bpimb linker to its thermodynamically unfavorable cis conformation, which coordinates to the copper ion, leading to the formation of a metallo-macrocycle. The existence of the cationic metallo-macrocycle [Cu(1,4-bpimb)(H₂O)]₂⁴⁺ in the polyoxometalate matrix as ion-pair compound 1 represents a rare example. Hirshfeld surface analyses have been studied to gain deep insight into the interactions around the metallo-macrocyclic cation. Theoretical calculations have been performed partly to establish the experimental results.