Crystal structure and vibrational analyses of nonlinear optical L-histidinium trifluoroacetate single crystals

Abstract

L-histidinium trifluoroacetate {LHTFA; [(C₃N₂H₄) CH₂CH (NH₃) (CO₂)]⁺ CF₃COO⁻}, single crystals were grown by slow evaporation of an aqueous solution at room temperature. It crystallizes in a noncentrosymmetric space group of P₁ of the triclinic system, with a = 5.1724(6) Å, b = 8.8183(12) Å, c = 12.481(3) Å, α = 96.193(17)°, β = 99.853(13)°, γ = 102.106(13)° and V = 542.26(16) ų. The structure was solved from 2063 unique reflections with a final residue factor ‘R’ of 0.038. There are two histidine cations and two trifluoroacetate anions in the asymmetric unit. The protonated cations and deprotonated anions are linked by a number of intermolecular N–H ... O hydrogen bonds to form a three-dimensional network. The relative powder second harmonic generation (SHG) efficiency has been evaluated and found as d_eff = 0.84 d_eff (KDP).