An ionic compound containing molecular iodine (ipq)4(Cu2I6)·2I2: Synthesis and theoretical investigation

Dark-red block-shaped crystals of the ionic compound (ipq)4[(Cu2I6)·2I2] (1) (ipq+ = N-(isopentyl)-quinolinium) were obtained by the reaction of ibq·I, CuI with I2 in polar solvent DMF. Compound 1 crystallizes in triclinic system [space group P1¯Z = 2, a = 10.4236(8) Å, b = 12.1950(9) Å, c = 15.6214(10) Å, α = 95.879(2)°, β = 102.174(2)° and γ = 113.757(2)°]. As indicated by structural analysis, 1 is constituted by ipq+ cations, [Cu2I6]4− anions and molecular iodine [dI−I = 2.8499(5) Å]. In 1, dimer Cu2I64− anion is composed by two edge-sharing CuI4 tetrahedra. Cu2I64− anions interact with I2 via strong I⋯I interaction to give [(Cu2I6)·2I2]4− clusters. Furthermore, electrostatic interactions between organic cations and inorganic clusters could be observed and contribute to the crystal packing. Finally, quantum chemistry calculation with DFT method was carried out to reveal the electronic structure of 1.