Exploring weak intermolecular interactions in thiocyanate-bonded Zn(II) and Cd(II) complexes with methylimidazole: crystal structures, Hirshfeld surface analysis and luminescence properties

ALEJANDRO DI SANTO; HIRAM PEREZ; GUSTAVO A. ECHEVERRÍA; OSCAR E. PIRO; RODRIGO A. IGLESIAS; RAÚL E. CARBONIO; AIDA BEN ALTABEF; DIEGO M. GIL

RSC Advances

The Royal Society of Chemistry

Lugar: Londres; Año: 2018 vol. 8 p. 23891 - 23902

Four new thiocyanate-Zn(II) and -Cd(II) complexes with 1-methylimidazole (1-MeIm) and 2-methylimidazole (2-MeIm), namely, Zn(1-MeIm)2(SCN)2 (1), Zn(2-MeIm)2(SCN)2 (2), Cd(1-MeIm)4(SCN)2(3) and polymeric [Cd(2-MeIm)2(SCN)2]n (4), have been synthesized and characterized by IR, Raman andUV-Vis spectroscopy. The thermal behavior for all complexes was evaluated by thermo-gravimetricanalysis and differential thermal analysis. The crystal structures of complexes 1?4 were solved by singlecrystalX-ray diffraction methods. A study of intermolecular interactions in the solid state compoundsrevealed that molecules are linked by weak N?H/S and C?H/S hydrogen bonds and also by C?H/pinteraction in the case of structures 2?4, which are responsible for the formation and stability of themolecular assemblies. Hirshfeld surfaces and 2D-fingerprint plots allowed us to visualize theintermolecular contacts and their relative contributions to the total surface for each compound. Acomparative analysis against similar halogen-bonded complexes was carried out to investigate thetendency of inter-molecular interactions to form contacts in crystals by using the enrichment ratiodescriptor. The emission spectra of the free imidazole derivatives and their Zn(II) and Cd(II) complexeswere recorded in acetonitrile solutions. The emissions observed in the spectra of complexes wereascribed to the intra-ligand transitions and ligand-to-metal charge transfer and we have observed aninteresting correlation between the fluorescence intensities and C?H/p interactions.