Fascinating Physical Properties of 2D Hybrid Perovskite [(NH3)(CH2)7(NH3)]CuClxBr4-x, x=0, 2 and 4

The 2-D organic-inorganic hybrid perovskites of the formula [(NH3)(CH2)(7)(NH3)]CuClxBr4-x, x=0, 2 and 4 were prepared by slow evaporation from ethanolic solution in stoichiometric ratio 1:1 (organic/inorganic). Microchemical analysis and x-ray diffraction (XRD) were used to confirm the formation of the presently investigated hybrids. Differential scanning calorimetry (DSC) indicated order-disorder transitions at T-1=357K, T-2=388K, and T-3=398K for x=0, 2 and 4 of the three heptain diammonium Cu hybrid perovskites, respectively. These transitions are in good agreement with the electrical permittivity results at different frequencies and temperatures. Optical properties and estimated band gap energy reveal that the band gap energy decreases sharply with replacement of Cl ion by Br ion where the band gap energy of [(NH3)(CH2)(7)(NH3)]CuBr4, x=0 (denoted 2C7CuBr) is 1.6eV (brown color) and for [(NH3)(CH2)(7)(NH3)]CuCl4, x=4 (denoted 2C7CuCl) is 2.6eV (yellow color). The differential magnetic susceptibility of 2C7CuBr in the temperature range 80-300K indicates the effective magnetic moment (eff)=2.05 BM.