Inclusion, pseudo-inclusion compounds and coordination polymer of Pd(II), Zn(II) and Cd(II) from salen-type Schiff base ligand with a 1,3-diimino spacer group: Crystal structures, spectroscopic and thermal studies

Novel complexes of palladium(II), zinc(II), cadmium(II) derived from salen-type Schiff base ligand 6,6′-diethoxy-2,2′-[2,2-dimethylpropane-1,3-diylbis(nitrilomethylidyne)]-diphenol (H2L), have been prepared and characterised by single crystal XRD, elemental analysis, electronic, IR, UV–Vis and thermal studies. While compounds 1 and 2 crystallize in the monoclinic crystal system with P21/c space group, compound 3 crystallizes in orthorhombic Pbca space group. Compounds 1 and 2 are supramolecular dimers while compound 3 is a 1D coordination polymer which spreads into a 3D supramolecular network. When checked with solvents of different polarities all the compounds showed negative solvatochromism. Luminescent properties were tracked and all the complexes showed blue luminescence with zinc being the most intense. TG–DTG studies were done to track the thermal behaviour of the complexes.

Graphical abstractInclusion compound, pseudo-inclusion compound and 1D coordination polymer from 6,6′-diethoxy-2,2′-[2,2-dimethylpropane-1,3-diylbis(nitrilomethylidyne)]-diphenol are discussed. Both the inclusion and pseudo-inclusion compounds form 1D supramolecular chains while the coordination polymer opens up into a 3D supramolecular network. The IR spectra of inclusion compound has two medium intensity ν(OH) bands due to the asymmetric and symmetric stretching of encapsulated water molecule. Charge transfer bands of all the compounds exhibit negative solvatochromism. All the compounds emit in blue region with zinc and cadmium having greater intensity when compared to that of ligand.Figure optionsDownload full-size imageDownload as PowerPoint slide