Crystal Engineering of NLO Materials Based on Metal−Organic Coordination Networks

TLDR

Crystal engineering enables the prediction and control of molecular packing in solids, attracting attention for creating technologically important materials. The study aims to develop crystal‑engineering strategies to synthesize noncentrosymmetric infinite coordination networks as second‑order nonlinear optical materials. The authors synthesize these networks by combining unsymmetrical bridging ligands and metal centers with well‑defined coordination geometries. They have demonstrated that such networks can be rationally synthesized, achieving high predictability for 3D diamondoid and 2D grid structures, and also producing 1D chain and helical analogues.

Abstract

Crystal engineering, the ability to predict and control the packing of molecular building units in the solid state, has attracted much attention over the past three decades owing to its potential exploitation for the synthesis of technologically important materials. We present here the development of crystal-engineering strategies toward the synthesis of noncentrosymmetric infinite coordination networks for use as second-order nonlinear optical (NLO) materials. Work performed mainly in our laboratory has demonstrated that noncentrosymmetric solids based on infinite networks can be rationally synthesized by combining unsymmetrical bridging ligands and metal centers with well-defined coordination geometries. Specifically, coordination networks based on 3D diamondoid and 2D grid structures can be successfully engineered with a high degree of probability and predictability to crystallize in noncentrosymmetric space groups. We have also included noncentrosymmetric solids based on 1D chains and related helical structures for comparison.