Solvent dependent supramolecular interactions in two 5-chloro thiophene 2-carboxylate bridged dinuclear copper(II) complexes

The synthesis, spectral characterization and crystal structures of two Cu(II) complexes namely [Cu2(5-TPC)4(DMF)2] (1) and [Cu2(5-TPC)4(DMSO)2] (2) where (5-TPC = 5-chloro thiophene 2-carboxylate, DMF = dimethyl formamide, DMSO = dimethyl sulfoxide) are reported. The complexes were obtained by using the same starting materials and reaction conditions except the solvents. Both (1) and (2) form dinuclear units of paddle wheel. In (1) a whole of the paddle wheel unit forms the asymmetric unit while in (2) two halves of paddle wheel unit forms the asymmetric unit and each paddle wheel unit is formed around the crystallographic inversion centre. The Cu⋯Cu distances in both the complexes are 2.6525(7) Å in (1) and 2.6809(4) Å, 2.6854(4) Å in (2). The Cu(II) ions are bridged by four (5-TPC) ligands in syn,syn-η1:η1 arrangement with DMF in (1) and DMSO in (2) coordinated at the apical positions. Further, the EPR data for both the compounds were taken in solid state as well as by dissolving the complex. Observed EPR spectra shows isotropic nature of copper (symmetrical) with distorted octahedral geometry and gη > g⊥ says that d x 2 - y 2 is ground state. Selected geometric parameters are compared with similar typed dimeric Cu(II) carboxylates with apical DMF, DMSO and other O donating ligands. The molecules of (1) are linked by C–H⋯O interactions. C–H⋯O and C–H⋯S interactions are found in crystal structure of (2).