l‑Homoproline-Directed Synthesis of\nOrganic–Inorganic Metal Iodides for Second Harmonic Generation

Three organic–inorganic metal iodides, namely,\n(NH<sub>4</sub>)(l-hp)ZnI<sub>3</sub> (<b>1</b>), [Cd(l-hp)<sub>4</sub>]Cd<sub>3</sub>I<sub>8</sub> (<b>2</b>), and (l-Hhp)(l-hp)PbI<sub>3</sub> (<b>3</b>), have been synthesized\nusing l-homoproline (l-hp) as the structure-directing\nagent. These compounds feature different noncentrosymmetric structures\nand optical properties. In particular, compound <b>3</b> shows\na large second-harmonic-generation response of 3.4 times that of KH<sub>2</sub>PO<sub>4</sub>. Density functional theory calculations were\nperformed to gain insight into its structure–property relationship.