Synthesis, crystal structure, photoluminescence and dielectric properties of a new organic–inorganic compound: tetrachlorocadmate (II) 2.2′-bipyridinium

Single crystals of a new organic–inorganic compound (C 10 H 10 N 2 ) CdCl 4 were grown by the slow evaporation technique and characterized by X-ray diffraction, Hirshfeld surface, Infrared absorption, Solid state 13 C NMR, photoluminescence (PL) properties, differential scanning calorimetry (DSC) and dielectric measurements. The title compound belongs to the monoclinic space group P2 1 /c with the following unit cell parameters: a = 7.29420(1), b = 13.9206(3), c = 14.3880(3) Å, β = 100.247(2)° and Z = 4. The structure can be described by the alternation of two different cationic-anionic layers. It consists of isolated [CdCl 4 ] 2− tetrahedral anions and 2.2′ bipyridinium (C 10 H 10 N 2 ) 2+ cations, which are connected via N–H⋯Cl hydrogen bonds. The Hirshfeld surface analysis was conducted to investigate intermolecular interactions and associated 2D fingerprint plots, revealing the relative contribution of these interactions in the crystal structure quantitatively. Furthermore, the room temperature infrared (IR) spectrum of the title compound was recorded and analyzed on the basis of detailed vibrational studies found in the literature; the detailed assignment confirms the presence of the organic groups. Solid state 13 C NMR spectrum shows four signals, confirming the solid state structure determined by X-ray diffraction. Besides, photoluminescence measurements showed a strong emission line at 2.95 eV associated with radiative recombinations of excitons confined within the [CdCl 4 ] 2− which were investigated at room temperature. Finally, the thermal analysis studies were performed, and phase transition was found in the temperature range between 300 and 550 K, while the electrical measurements were performed to discuss the phase-transition mechanism.