Synthesis of thermochromic salts containing guanidinium(1(+)) cations and copper(II) chloro complexes; Crystal and molecular structure of (CH6N3)(2)[Cu(H2O)Cl-4]

Reaction of CuCl2 with guanidine hydrochloride (G . HCl) in hydrochloric ac id gave the (GH)CuCl3 and (GH)(2)[Cu(H2O)Cl-4] compounds exhibiting reversi ble thermochromism. The (GH)(2)[Cu(H2O)Cl-4] compound was X-ray stracturall y characterized; unit cell parameters: a = 8.097 (2), b = 18.517(4), c = 16 .959(3) Angstrom, beta = 91.44(3)degrees, V = 2541.9(9) Angstrom(3), space group P2(1)/c, Z = 4, rho(calcd) = 1.795 g/cm(3), R-1 = 0.0246. The crystal structure is built from the GH(+) cations and [Cu(H2O)Cl-4](2-) anions. A nearly square-planar environment of each of the two crystallographically in dependent copper atoms includes three Cl atoms (Cu-Cl 2.2531-2.3168 Angstro m) and O atom of water molecule (Cu-O 1.986 and 2.002 Angstrom). One of the two Cl atoms completing square-bipyramidal (4 + 1 + 1) surrounding of the copper atom is at a distance of 2.8148 and 2.6375 Angstrom, while the trans -positioned atom is at a longer distance of 3.2184 and 3.471 Angstrom from Cu(1) and Cu(2), respectively. With allowance made for the long Cu-CI bonds , the [Cu(H2O)Cl-4](2-) anions can be considered as forming zigzag chains l inked to the cations by strong hydrogen bonds. Measurements of magnetic sus ceptibility of (GH)CuCl3 over the temperature range 2-300 K and the IR and Raman spectroscopy data give evidence for the dimeric structure of the comp lexed anion.