Structural characterization of the {3[ΗBPMTU]+ · 3[X]- · nH2O} salts (BPMTU = 1,3-bis(3-pyridylmethyl)-2-thiourea and X = Cl, Br, I). A polychlorine network based on O ··· Cl- and OH ··· Cl- interactions

Ionic salts with the formulae {3[ΗBPMTU]+ · 3[X]- · nH2O} (BPMTU = 1,3-bis(3-pyridylmethyl)-2-thiourea, X = Cl- and n = 1.5 (1), X = Br-and n = 1 (2), X = I- and n = 1 (3)) were synthesized. The compounds have been characterized by elemental anaylses, TG-DTA, FT-IR, far-IR, Raman, ESI-MS and 1H, 13C-NMR spectroscopic methods, and X-ray powder diffraction techniques. The crystal structures of 1 and 2 have also been determined by X-ray diffraction at 120(2) and 100(2) K, respectively. In 1, weak lp(Cl-) → σ*(O-Η) hyperconjugative interactions and OH ··· Cl- hydrogen-bonding interactions lead to the formation of 1-D zigzag tetrameric complexes consisting of four chlorides bridged by four waters. Two oxygens of the bridging waters are also coordinated to Cl- of the complex forming a parallelogram-shaped ring. Two chlorides are also anchored by NH ··· Cl- hydrogen bonds in the free space between four tetrameric complexes. Heating 1 at 100°C for 4 h does not remove lattice water and the framework structure is retained. In 2, NH ··· Br- hydrogen-bonding interactions stabilize the supramolecular architecture. In this case, however, only two bromides are bridged by one water through OH ··· Br- hydrogen bonds. The supramolecular interactions existing in the crystal packing of the ionic salts have been analyzed at the density functional theories and ab initio CCSD(T) levels of the theory. [ABSTRACT FROM AUTHOR]