Structural dependence of π–π interactions in dithiocarbazato and thiosemicarbazato nickel complexes

Abstract

Structures and stabilization due to π–π interactions of N₂S₂ coordinated nickel(II) complexes NiL₂ have been investigated by ESI-MS spectrometry and X-ray diffraction methods. For the systems with HL = 4,5-diazafluoren-9-one thiosemicarbazone (HL¹), fluoren-9-one thiosemicarbazone (HL²), fluoren-9-one dithiocarbazone (HL³) and 4,5-diazafluoren-9-one dithiocarbazone (HL⁴), the Ni(II) atom in each complex is coordinated in a distorted square-planar geometry with two aromatic rings positioned on the same side. This cis configuration is stabilized by π–π stacking interactions between the aromatic rings. Detailed structural analyses reveal that whereas the intermolecular π–π stacking interactions connect NiL¹₂ molecules into a one-dimensional screw chain, the intermolecular π–π stacking interactions and the C–H···π interactions link NiL²₂ molecules into a dimer. The π–π stacking interactions and the C–H···π interactions among the two phenyl rings and two fluorene rings of NiL³₂ form a closed hydrophobic brick. In NiL¹₂ one of the two phenyl rings interacts with the two 4,5-diazafluorene rings to give an opened hydrophobic cavity; the edge-to-face interactions about another phenyl ring arrange the molecules into a one-dimensional network.