Chiral Ligand‐Driven Systematic Synthesis of Coordination Polymers with Non‐centrosymmetric Structures

Abstract

Chirality is an important concept in chemistry revealing intriguing optical properties such as circular dichroism (CD), circularly polarized luminescence (CPL), etc. As one of the non-centrosymmetric (NCS) classes, chiral materials with extended structures may exhibit unique nonlinear optical (NLO) properties, such as second-harmonic generation (SHG). In this Concept article, a series of recently discovered NCS coordination polymers (CPs) from use of carefully designed chiral organic ligands are reviewed. Combining several metal cations such as lanthanides, lead, zinc, and cadmium with rigid chiral ligands has resulted in interesting CPs with both polar and nonpolar structures. Detailed structures, SHG properties, and structure-property relationships are provided. The importance of hyperpolarizability formed by intermolecular hydrogen boding interactions to SHG is emphasized.

Achieving Large Second Harmonic Generation Effects via Optimal Planar Alignment of Triangular Units

“…[ 34,35 ] Very recently, introducing chiral amino acids as templates or ligands proved to be an effective and promising synthetic strategy to achieve new solids with NCS structures, and a series of novel targeting chiral coordination compounds with strong SHG efficiency were obtained. [ 36–38 ] The above‐mentioned hybrid materials, integrating the merits of both organic and inorganic moieties, are potentially promising NLO materials.…”

Enantiomeric Hydrogen-bonded Chains Driving Ferroelectric and Nonlinear Optical Behavior

“…Remarkably, to our knowledge, [HDABCO]­[ l - and d -MA] show the most outstanding SHG intensity among the organic ferroelectrics, such as MDABCO-NH 4 I 3 , [DDABCO]­[TFSA], and nopinic acid (Table S1). The hydrogen bonds in these neutral one-dimensional chains may play a crucial role in enhancing the SHG intensity. − The SHG intensity of [HDABCO]­[ l - and d -MA] gradually decreased with increasing temperature before T c and suddenly dropped to zero at T c , which supports the 32F2-type ferroelectric/ferroelastic phase transition. Furthermore, the anisotropy of the SHG intensity for the crystals of [HDABCO]­[ l - and d -MA] was verified through polarization SHG measurement (Figures a and S6b).…”

Multifunctional Chiral d10‐Metal Coordination Polymers: Tunable Photoluminescence and Efficient Second‐Harmonic Generation with Circular Dichroic Response

“…nurturing NCS structures, birthing a new era in NLO materials synthesis. [38][39][40][41][42][43] The synthetic approach, involving the introduction of homochirality into structural components to induce NCS structures, enhances the chiroptical properties of NLO materials. SHG circular dichroism (SHG-CD) is defined as the normalized difference between the SHG counts observed when excited with left-and right-circularly polarized light.…”