Single crystal growth, x-ray structure analysis, optical band gap, raman spectra, strain tensor and photoluminscence properties in [HgCl<sub>4</sub>]<sup>-</sup> [R]<sup>+</sup> and [ZnCl<sub>4</sub>]- [R]+ (R= 2-amino-5- chloropyridine) hybrid materials

Abstract

The single crystal growth of tetrachloromercurate (II) [HM-1] and tetrachlorozincate (II) [HM-2] with 2-amino-5-chloropyridine has been performed by slow cooling (SC) crystal growth technique of solution growth methodin which needle shaped transparent single crystals (0.5 x 0.2 x 0.2)mm were obtained. The crystal structures of these hybrid materials have been studied by X-ray diffraction, experimental and computational methods. [HgCl 4 ] 2- anions have a distorted tetrahedral geometry and the tetrahedra hybrid structure exhibit interwoven inorganic-organic layers mingled through N-H δ+ ...Cl δ- hydrogen bonding interactions. The mercurophilic interactions [Hg...Hg = 3.984(5)A] and halogen interactions [Cl...Cl = 3.406(2)A] form 2D parallelogram pattern of secondary interactions in [HM-1] whereas for [HM-2] crystal structure is stabilized by Cl...Cl = 3.357(2)A interactions. UV-vis absorption spectra depict the change in optical band gap from 3.01 eV to 3.42 eV on replacing the metal halide group, could be due to increase in optical absorption as a function of wavelength. The Raman and Hyper-Raman tensors calculations were performed based on single crystal X-ray data and the Lagrangian strain tensor calculations show the degree of lattice distortion = 1.794 between [HM-1] and [HM-2] which are useful tools for the optical response properties of inorganic-organic hybrid derivatives. The photoluminescence emission spectra peaks were observed in the wavelength range of 371 to 598 nm for material [HM-1] and in the wavelength range of 384 to 600 nm for material [HM-2] and lie in the visible range for both materials.