Synthesis, characterization, thermal studies, Hirshfeld surface analysis and DFT study of a strontium(II) thiocyanate complex templated by hexamethylenetetramine

The synthesis and structural characterization of a strontium thiocyanate coordination compound with hexamethylenetetramine [Sr(H2O)6(SCN)2]·2HMTA has been reported. The complex crystallizes in the monoclinic space group P21/c. This air-stable and water-soluble complex undergoes thermal decomposition in several steps. The molecules are assembled into a stable 3D supramolecular assembly via O–H···S and O–H···N stacking interactions. The supramolecular contacts in the complex were investigated and visualized through a detailed analysis of the Hirshfeld surface (HS) analysis and 2D fingerprint plots to quantify the interactions within the crystal structure. The noncovalent interactions were analysed using the Bader's quantum theory of "atoms in molecules" (QTAIM) and the noncovalent interaction plot (NCI plot) and rationalized using molecular electrostatic potential surface calculations. The binding energies associated with the noncovalent interactions observed in the crystal structures and the interplay between them have been calculated using theoretical DFT calculations. The AIM, NCI and HOMO-LUMO profiles substantiate the H-bond classification. This study demonstrated a good correlation between experimental and theoretical data.