Reversible color changes of chiral double salts of d-(+)-camphoric diammonium and transition-metal sulfates via gain and loss of crystalline and coordination water molecules

• Published in: Inorganica Chimica Acta Vol. 378; no. 1; pp. 224 - 230
• Main Authors: Zhang, Kun, Cao, Kou-Sen, Wang, Gang, Peng, Yu-Xin, Chu, Zhao-Lian, Huang, Wei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.11.2011
• Subjects: Chiral complexes; Double salts; Supramolecular interactions; Vibrational circular dichroism; Double salts; Chiral complexes; Vibrational circular dichroism; Supramolecular interactions
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2011.09.015

Six chiral double salts ( 1– 6), formulated as {[M(SO 4) 2(H 2O) 4](LH 2)}·2H 2O [M = Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II), LH 2 = d-(+)-camphoric diammonium], are prepared and characterized by single-crystal X-ray diffraction and FT-IR/VCD spectra. Co(II), Ni(II) and Cu(II) complexes ( 2– 4) exhibit reversible color changes via gain and loss of two crystalline and four coordination water molecules, which can be proved by their TG and PXRD analyses. [Display omitted] ► Six chiral double salts of d-(+)-camphoric diammonium and metal sulfates are characterized. ► FT-IR/VCD spectra are used to characterize the chirality of metal complexes. ► Co(II), Ni(II), Cu(II) compounds show reversible color changes via gain or loss of water molecules. ► This is the first report on chiral double salts exhibiting chromotropism properties. Six novel chiral double salts ( 1– 6) composed of d-(+)-camphoric diammonium (LH 2) and transition-metal sulfates, formulated as {[M(SO 4) 2(H 2O) 4](LH 2)}·2H 2O [M = Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)], have been prepared and fully characterized including single-crystal X-ray diffraction, Fourier transform infrared (FT-IR) and vibrational circular dichroism (VCD) spectral investigations. Co(II), Ni(II) and Cu(II) compounds 2– 4 exhibit reversible color changes between 20 and 140 °C via gain and loss of two crystalline and four coordination water molecules, which can be proved by their thermogravimetric (TG) and powder X-ray diffraction (PXRD) analyses. To the best of our knowledge, this is the first report on chiral double salts showing chromotropism properties.