Synthesis, crystal structure, and optical properties of benzyl isoquinolinium dibromo-bis(isothiocyanate)zinc(II)

Abstract

The title inorganic-organic hybrid material containing a mixed anion, [BzIQl]2[Zn(NCS)2Br2] (1) (BzIQl = benzyl isoquinolinium, NCS− = isothiocyanate), crystallizes with a benzyl isoquinolinium cation and half of a bis(bromo)-bis(isothiocyanate)zinc(II) anion in the asymmetric unit. It was characterized by elemental analysis, Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), electrospray ionization mass spectrometry (ESI-MS), and powder and single crystal X-ray diffraction (PXRD and SC-XRD). The organic cation exhibits a Λ-shaped configuration in which two aromatic rings form an inclined dihedral angle of 90.12°. The ZnII ion in the anion is coordinated by two Br ions and two isothiocyanate ions, and two contiguous anions forms a dimer through S···Br interactions. The thermal stability of the hybrid crystal analyzed by thermogravimetric-differential thermal analysis (TG-DTA) reveals that the title crystal was stable up to 170 °C. The PXRD study confirms the phase purity of the crystalline sample. The band gap energy between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) explains the eventual charge transfer interaction that take place mainly between the anion and [BzIQl]+ cation, and the low value (0.46 ev) indicates the suitability of the crystal for optical application. The first hyperpolarizability predicted using density functional theory (DFT) is more than 720 times that of the reference potassium dihydrogen phosphate crystal (KDP).