Moisture-induced single-crystal-to-powder structural transformation in cadmium coordination compounds containing electron-deficient ligand: coordinated solvent exchange and retention of dimension

Abstract

Two cadmium coordination compounds and one cadmium coordination polymer containing electron-deficient 3,6-bis(pyridin-3-yl)-1,2,4,5-tetrazine (3,3′-pytz) ligand, namely, [Cd(3,3′-pytz)2(EtOH)2(ClO4)2] (1), [Cd(3,3′-pytz)2(H2O)2(ClO4)2] (2) and {[Cd(3,3′-pytz)(EtOH)2(ClO4)2](1,4-Dioxane)}n (3) have been successfully synthesized by using solvent effect in solvent diffusion method. The single-crystal X-ray diffraction (SC-XRD) analysis of compounds 1 and 2 represent formation of zero-dimensional coordination compounds, whereas compound 3 exhibits 1D linear chain coordination polymer. Our further investigation shows that by the absorption of moisture from the air, while maintaining their structural dimensions, compounds 1 and 3 underwent single-crystal-to-powder structural transformation to compounds 2 and [Cd(3,3′-pytz)(H2O)2(ClO4)2]n (3T) (Inorg. Chem., 2024, 63, 983-999), respectively. Our finding was confirmed through powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), elemental analysis and FT-IR studies. Also, Hirshfeld surface analysis was used to show detailed investigation of the intermolecular interactions especially semilocalized (η2) and delocalized (η6) anion-π interaction formed between electron-deficient tetrazine rings and perchlorate anions in 1-3 compounds. We find that several combined supramolecular synthons such as anion-π-π-anion (ClO4-···πtet···πtet···ClO4-) and π-sandwich anion-π-anion (ClO4-···πtet···ClO4-) in these structures.