Organic-Inorganic Hybrid Noncentrosymmetric (Morpholinium)2Cd2Cl6 Single Crystals: Synthesis, Nonlinear Optical Properties, and Stability

To design nonlinear optical (NLO) materials, we focused on combinations of d10metal cation (Cd2+)-based chlorideand morpholine molecules to form organic-inorganic hybrids. The O of morpholine containing lone-pair electrons can be integratedwith Cd2+by a ligand-to-metal charge transfer (LMCT) strategy to build acentric structures benefiting from the second-order Jahn-Teller effect. Introduction of the high-electronegativity chlorine can make polyhedrons of acentric crystals more distorted andconducive to a strong second harmonic generation (SHG) response. Therefore, (Morpholinium)2Cd2Cl6crystals were constructedand synthesized by a solvent evaporation method. (Morpholinium)2Cd2Cl6belongs to the orthorhombicP212121space group andshows a one-dimensional (1D) structure with distorted [CdCl6] and [CdCl4O2] octahedrons. The short cutoffedge of(Morpholinium)2Cd2Cl6was determined to be about 230 nm. The SHG response of (Morpholinium)2Cd2Cl6exhibited an intensityof approximately 0.73xKDP as estimated by the powder second harmonic generation technique. Furthermore, related theoreticalcalculations were performed to study the relationship of the band structure, refractive anisotropy, electronic state, and nonlinearoptical response. Besides, (Morpholinium)2Cd2Cl6showed relatively good thermal stability. This work can serve as a guide for thedesign and synthesis of new large NLO hybrid crystals with d10transition metals.

Automated summary

By combining d10 metal cation (Cd2+) with morpholine molecules, organic-inorganic hybrid materials for nonlinear optical (NLO) applications have been designed. The resulting structures exhibit centric structures with the second-order Jahn-Teller effect, resulting in strong second harmonic generation (SHG) responses.