Crystal structure and Hirshfeld surface analysis of chiral catena-poly[l-histidinediium [[diiodido-cuprate(I)]-μ-iodido] monohydrate].

The title compound, {(C6H11N3O2)[CuI3]·H2O} n or (l-HisH2)CuI3·H2O (1), is a chiral organic-inorganic compound that crystallizes in the monoclinic P21 space group. The asymmetric unit of 1 consists of one diprotonated l-histidinium cation {4-[(2S)-2-aza-niumyl-2-carb-oxy-eth-yl]-1H-imidazol-3-ium}, one Cu+ cation, three iodide anions, and one co-crystallized water mol-ecule. The Cu+ cations is four-coordinated by iodide anions forming a [CuI4] unit. Structural analysis of the [CuI4] unit using the Baur, τ4, and τ4' indices reveals its slight deviation from ideal tetra-hedral geometry. Two iodide anions from each [CuI4] unit bridge adjacent Cu+ centers, forming chiral left-handed helical [CuI3] n 2n- polymeric chains. The biprotonated l-histidinium cations balance their negative charge and form N-H⋯I, O-H⋯I, and weak C-H⋯I hydrogen bonds with the [CuI3] n 2n- chains. According to the Hirshfeld surface analysis, the main contributions to the crystal packing arise from H⋯I and H⋯O contacts, while C⋯I and N⋯I inter-actions indicate the presence of I⋯π contacts. The compound reported here represents the first example of a chiral A 2CuX 3-type metal halide, which shows potential for second-harmonic generation, polarized blue-light emission, and other non-linear optical applications.