Bulk crystal growth and optical properties of a novel organic–inorganic hybrid nonlinear optical thiocyanate: [Mn(CH3CONH2)2] [Hg(SCN)4]

Abstract

The growth of bulk nonlinear optical (NLO) crystals that exhibit robust second harmonic generation (SHG) is currently an intriguing and rapidly advancing field for laser and photonic applications. Among the various options available, organic–inorganic hybrid materials offer numerous possibilities due to their distinctive amalgamation of inorganic coordinate frameworks and organic molecules. Herein, we have successfully developed a novel non-centrosymmetric (NCS) organic–inorganic hybrid NLO material, manganese mercury thiocyanate-bis(acetamide), [Mn(CH₃CONH₂)₂][Hg(SCN)₄] (MMTA), by synergistically incorporating inorganic polyhedra and organic conjugated molecules. The crystal displays a polar architecture comprising an asymmetric [HgS₄] tetrahedron and [MnN₄O₂] octahedron, which are connected by four π-conjugated –S–CN– ligands. More intriguingly, inch-sized single crystals with dimensions up to 50 × 50 × 12 mm³ have been easily grown from aqueous solutions by a temperature-lowering method. The optical property investigation suggests that MMTA is a phase-matching NLO material with a large SHG response approximately 2.5 times that of KH₂PO₄, demonstrating its potential for NLO applications. Based on a combination of structural analysis and theoretical calculations, it is suggested that the significant SHG response can be attributed to the cooperative interaction between conjugated organic molecules and a highly asymmetric inorganic distorted octahedron. This work introduces an effective approach for the discovery of high-performance quadratic NLO materials, with a particular focus on organic–inorganic hybrid compounds.