Structural and optical diversity in copper halide-based ferromagnetic inorganic-organic layered hybrids

Self-assembled two-dimensional lead-free inorganic-organic hybrids, (C12H25NH3)(2)Cu(Cl1-xBrx)(4) and (C6H9C2H4NH3)(2)Cu(Cl1-xBrx)(4) have been investigated for various compositions 0 <= x <= 1. Uniformly crystalline single phase (C12H25NH3)(2)Cu(Cl1-xBrx)(4) systems are grown layer by layer along the c-axis. In the case of (C6H9C2H4NH3)(2)Cu(Cl1-xBrx)(4), we find binary crystalline phase for the composition 0 < x <= 1 and structural frustration is indicated through the observation of split in the (00l) diffraction peaks. For both the systems, Raman vibrational modes in the range of 70-400 cm(-1)are related to buckling of distorted octahedra of CuX6 (X = Cl and Br) in the inorganic planes. The Raman frequencies compositional red-shift is due to the reduced bonding strength of the Cu-X vibrations by the replacement of higher electronegative Cl atoms with lower electronegative Br atoms. In the infrared spectrum also, symmetric (similar to 1491 cm(-1)) and asymmetric (similar to 1582 cm(-1)) deformations of NH3-X bonds show a redshift in the frequency with the increasing Br-content in both types of systems. The optical absorption spectra, typical d-d transitions in Cu2+ and consistent band-edge related redshift features have been discussed in detail.