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

Abstract A series of noncentrosymmetric metal sulfates [R-C 5 H 14 N 2 ][M II (H 2 O) 6 ](SO 4 ) 2 and [S-C 5 H 14 N 2 ][M II (H 2 O) 6 ](SO 4 ) 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)-C 5 H 12 N 2 or S-2-methylpiperazine (S)-C 5 H 12 N 2 . These materials crystallize in the polar, noncentrosymmetric space group P 2 1 (No. 4), crystal class 2 ( C 2 ). Isolated [M II (H 2 O) 6 ] 2+ , [(R)-C 5 H 14 N 2 ] 2+ or [(S)-C 5 H 14 N 2 ] 2+ cations and (SO 4 ) 2− anions linked together via two types of hydrogen bonds, O w –H w ⋯O and N–H⋯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.