Synthesis, crystal structures, second harmonic generation response and temperature phase transitions of two noncentrosymmetric Cu(II)-hybrid halides compounds: [(R)-C7H16N2][CuX4] (X = Cl or Br)

Abstract (R)-(+)-3-aminoquinuclidine was used in the synthesis of [(R)-C 7 H 16 N 2 ][CuCl 4 ] (1) and [(R)-C 7 H 16 N 2 ][CuBr 4 ] (2) , which both contain similar [CuX 4 ] 2- anions (X = Cl or Br). The structures of the two compounds were determined using single-crystal X-ray diffraction. The use of enantiomerically pure sources of (R)-C 7 H 14 N 2 forces crystallographic noncentrosymmetry. These materials crystallize in the chiral space group P 2 1 2 1 2 1 (No. 19), which exhibits the enantiomorphic crystal class 222 ( D 2). In the molecular arrangement, the [CuX 4 ] 2- anions are linked to the organic cations through N H … X and C H … X hydrogen bonds to form cation-anion-cation molecular units, which are held together by means of offset face-to-face interactions giving a three-dimensional network. Thermal stability of the crystals was ascertained by TG measurement. Compounds (1) and (2) display several phases transition with higher transition temperature at T = 100 °C. The Kurtz and Perry powder method using Nd:YAG laser shows that their second harmonic generation (SHG) efficiencies are about 0.81 and 0.82 times as large as that of KH 2 PO 4 (KDP), respectively. Such a chiral hybrid metal halides skeleton could provide a new platform for future engineering in the areas including information storage, light modulators and optoelectronic functionalities.