Polymeric polymorphs and a monomer of pseudohalide incorporated Cu(II) complexes of 2,4-dichlorido-6-((2-(dimethylamino)ethylimino)methyl)phenol]: Crystal structures and spectroscopic behavior

• Two polymeric polymorphs and a monomeric Cu(II) complex of a Schiff base system is discussed.
• The polymorphs are one-dimensional helical coordination polymers with azide in single asymmetric equatorial-axial end-on bridging mode.
• An attempt to investigate the involvement of various supramolecular forces and halogen interactions in crystal packing and stability is carried out.
• Charge transfer bands exhibit negative solvatochromism while the d–d bands show positive effect.
• The complexes luminesce in the blue region.

In the present investigation, copper(II) complexes of tridentate 2,4-dichlorido-6-((2-(dimethylamino)ethylimino)methyl)phenol] (HL) Schiff base system incorporating azido [Cu(L)(N3)]n (1a and 1b) and cyanato groups [Cu(L)(NCO)] (2) are prepared and characterized by elemental analysis, IR, UV–Vis and single crystal X-ray diffraction studies. While the polymeric polymorphs, 1a and 1b have a square-pyramidal geometry for the basic unit, complex 2 exhibits square planar topology. The polymorphs are one-dimensional helical coordination polymers with azido group in single asymmetric equatorial–axial end-on bridging mode. The interestingly different combinations of intermolecular interactions have resulted in polymorphs 1a and 1b. Based on the angular preference, intermolecular distance and the size of Cl atom, type I halogen interactions which is rather rarely observed is also discussed. Solvent effect on the charge-transfer bands and d–d bands were analyzed and the former exhibits negative solvatochromic effect while latter a positive effect with increasing polarity of solvents.Solid and solution state optical emission properties are analyzed. All the copper complexes emit in the blue region. Thermal analyses have been performed in order to understand the thermal decomposition pattern of the complexes. Spin Hamiltonian and bonding parameters have been calculated from EPR analysis. The g values, calculated for the complexes 1a, 1b in frozen DMF, indicate the presence of the unpaired electron in the dx2-y2dx2-y2 orbital consistent with a square pyramidal topology whereas that of complex 2 corresponds to a rhombic symmetry.

Two polymeric polymorphs and a monomeric system of tridentate 2,4-dichlorido-6-((2-(dimethylamino)ethylimino)methyl)phenol] Schiff base system is discussed. The polymeric polymorphs are one-dimensional helical coordination polymers with azide in a rather rare single asymmetric equatorial–axial end-on bridging mode. An attempt to investigate the involvement of various supramolecular forces and halogen interactions in crystal packing and stability is carried out. Charge transfer bands exhibit negative solvatochromism while the d–d bands show positive effect. The complexes luminesce in the blue–violet region of the visible spectrum and therefore applicable in LEDs. The polymorphs have almost similar spectroscopic behavior and the polymorphism is due to the difference in the packing forces involved.Figure optionsDownload as PowerPoint slide