Synthesis, crystal structures and thermal behaviour of organic-inorganic hybrids incorporating a chiral diamine

A series of noncentrosymmetric metal sulfates [R-C5H14N2][M-II(H2O)(6)](SO4)(2) and [S-C5H14N2][M-II (H2O)(6)](SO4)(2) (M-II = Mn (1, 2), Fe (3, 4), Co (5, 6) and Ni (7, 8)) have been synthesized by slow evaporation conditions through the use of enantiomorphically pure sources of either R-2-methylpiperazine (R)-C5H12N2 or S-2-methylpiperazine (S)-C5H12N2. These materials crystallize in the polar, noncentrosymmetric space group P2(1) (No. 4), crystal class 2 (C-2). Isolated [M-II(H2O)(6)](2+), [(R)-C5H14N2](2+) or [(S)-C5H14N2](2+) cations and (SO4)(2-) anions linked together via two types of hydrogen bonds, O-w-H-w center dot center dot center dot O and N-H center dot center dot center dot O, from which supramolecular structures are formed. The use of single enantiomer of either R-2-methylpiperazine or S-2-methylpiperazine precludes inversion symmetry within the crystal lattices and forces crystallization in noncentrosymmetric structures. Compounds 1-8 were characterized using single crystal X-ray diffraction, infrared spectroscopy and thermal analyses. The structural arrangements and the intermolecular interactions such as hydrogen-bonding are discussed. (C) 2011 Elsevier B. V. All rights reserved.