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

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.