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

Abstract

To design nonlinear optical (NLO) materials, we focused on combinations of d10 metal cation (Cd2+)-based chloride and morpholine molecules to form organic–inorganic hybrids. The O of morpholine containing lone-pair electrons can be integrated with 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 and conducive to a strong second harmonic generation (SHG) response. Therefore, (Morpholinium)2Cd2Cl6 crystals were constructed and synthesized by a solvent evaporation method. (Morpholinium)2Cd2Cl6 belongs to the orthorhombic P212121 space group and shows a one-dimensional (1D) structure with distorted [CdCl6] and [CdCl4O2] octahedrons. The short cutoff edge of (Morpholinium)2Cd2Cl6 was determined to be about 230 nm. The SHG response of (Morpholinium)2Cd2Cl6 exhibited an intensity of approximately 0.73 × KDP as estimated by the powder second harmonic generation technique. Furthermore, related theoretical calculations were performed to study the relationship of the band structure, refractive anisotropy, electronic state, and nonlinear optical response. Besides, (Morpholinium)2Cd2Cl6 showed relatively good thermal stability. This work can serve as a guide for the design and synthesis of new large NLO hybrid crystals with d10 transition metals.

New Low-Dimensional Lead-Free Perovskite (2-AMP)2BiX7·H2O (X = Cl, Br) Crystals: Synthesis, Stability, and Nonlinear Optical Properties

“…Organic–inorganic hybrid metal halide perovskites, as an upcoming generation of functional materials, have currently intrigued tremendous interest due to their potential application in photovoltaics, optoelectronics, piezoelectrics, and ferroelectrics. − The abundant functionality of these materials is favored by their tunable structures, chemical compositions, morphologies, and dimensionality. Among them, the rapidly developing solar cells based on the light-absorbing materials organolead halides APbX 3 (where A is an organic cation, X is a halogen anion) have increased the power conversion efficiency more than 20% in merely several years. , However, the toxicity of lead to the environment and poor stability in the presence of moisture, heat, and extended light exposure have become key bottlenecks toward future commercialization and industrialization .…”

(C4H10NO)PbX3 (X = Cl, Br): Design of Two Lead Halide Perovskite Crystals with Moderate Nonlinear Optical Properties

“…The second-order nonlinear optical (NLO) crystals that can broaden output wavelengths play a significant function in modern optical techniques, such as precise micromanufacturing, electro-optical amplitude modulation, photoetching, biological tissue imaging, and optical data storage. − The majority of the commercial NLO materials are inorganic crystals, such as KBe 2 BO 3 F 2 (KBBF), β-BaB 2 O 4 (β-BBO), LiB 3 O 5 (LBO), KH 2 PO 4 (KDP), and AgGaS 2 (AGS), etc. However, because of the enormous cost and time-consuming preparation of some NLO inorganic crystals, they cannot fill the fast-growing requirements of laser techniques, and continuous endeavors have been made to design and seek novel crystals with noncentrosymmetric (NCS) structuresa fundamental requirement for the SHG effect for the development of fundamental research as well as practical applications. − …”

A novel 2-(aminomethyl)pyridineH2PO4 crystal with second-order nonlinear optical performance

“…Using the Kurtz-Perry method, 41,42 the powder SHG responses were acquired using a Q-switched Nd:YAG laser at 1064 nm. The crystal samples of (2-Ampy)H 2 PO 4 and KDP, as the reference, were ground and sieved into six distinct particle sizes of 38-55, 55-85, 85-105, 105-150, 150-200 and 200-250 μm.…”