Crystallographic characterisation, linear and nonlinear optical studies of DABCO family hybrid crystal: 1,4-diazabicyclo[2.2.2]octane-hexaaqua cobalt (II)

Abstract A new semi organic crystal 1,4-diazabicyclo[2.2.2]octane-hexaaqua cobalt (II) (DHAC) was synthesised using slow evaporation solution technique. Single crystal X-ray diffraction (SCXRD) confirmed that the compound crystallizes in the triclinic space group P 1 ¯ , featuring a slightly distorted CoO 6 coordination that is stabilized through strong hydrogen bonding with protonated DABCO. FTIR analysis confirms the coordination of water and nitrate ligands, validating the molecular framework. UV-Visible spectroscopy revealed a sharp absorption edge and a band gap of 3.78 eV, indicating good transparency in the visible region and minimal lattice defects. The thermal analysis indicated good stability with finite major decomposition steps, signifying a well-ordered structure with a strong intermolecular bond. Since, the crystal synthesised is centrosymmetric in nature, the nonlinear optical characteristics was investigated by Z Scan technique which revealed significant nonlinear absorption and third order nonlinear susceptibility. Furthermore, the crystal exhibited a high laser damage threshold, reflecting resistance to optical stress.