Unveiling\nNoncentrosymmetric Pyridine Carboxylates\nfrom Centrosymmetric Templates through Motif Configuration Modulation\nin Zero-Dimensional System

Developing approaches to induce noncentrosymmetric (NCS)\nframeworks\nthrough atomic-scale structural optimizations is crucial due to the\ngrowing need for new ultraviolet (UV) nonlinear optical (NLO) materials.\nHerein, the first two new NCS pyridine carboxylates, ZnBr(C<sub>6</sub>H<sub>3.5</sub>FNO<sub>2</sub>)<sub>2</sub> (<b>1</b>) and\nCd(C<sub>6</sub>H<sub>3</sub>FNO<sub>2</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub> (<b>2</b>), were successfully synthesized using\ncentrosymmetric (CS) templates and rational structural reconstructions\ninduced by different ionic radius. Both compounds crystallize in the\northorhombic system and feature metal-centered zero-dimensional (0D)\nisolated clusters. Substituting the [ZnO<sub>2</sub>N<sub>2</sub>O]\npyramid in the CS pyridine carboxylate with the [ZnO<sub>2</sub>N<sub>2</sub>Br] pyramid in compound <b>1</b> breaks the centrality,\nleading to an NCS framework with a second harmonic generation (SHG)\nresponse of 1.7 × KH<sub>2</sub>PO<sub>4</sub> (KDP). Introducing\na larger Cd<sup>2+</sup> cation results in a <i>trans</i>-to-<i>cis</i> transition of the [MO<sub>4</sub>N<sub>2</sub>] (M = Zn, Co, and Ni in CS templates, Cd in <b>2</b>) octahedra,\nforming a wing-shaped asymmetric 0D cluster with an SHG response of\n2.1 × KDP. These findings indicate an approach that can effectively\ninduce NCS structures of 0D organic–inorganic hybrid materials.