Dinuclear, star-shaped tetranuclear and trinuclear-based two-dimensional metal complexes derived from a less investigated Schiff base ligand: Syntheses, crystal structures and spectroscopic correlation

• One rare example for each of CuII(UVIO2) and star-shaped CuII3CdII compounds.
• First examples of CuIIMIICuII-based, dicyanamide-bridged polymers (M = Zn, Ni, Co).
• Star-shaped system here is the best star-shaped system in terms of bond distances.
• Exploration of a less investigated Schiff base ligand.
• An excellent correlation of d–d band position with structural parameter.

The work in this paper deals with five new complexes of composition [CuII(MeCN)L(UVIO2)(NO3)2]⋅MeCN (1), [(CuIIL)3CdII](ClO4)2 (2) and [(CuIIL)2MII(μ1,5-dicyanamide)2]n (M = Co (3), M = Ni (4) and M = Zn (5)) derived from a single-compartment Schiff base ligand H2L, which is the [2 + 1] condensation product of salicylaldehyde and 1,4-diaminobutane. Single crystal X-ray structures of all the five complexes have been determined. Compound 1 is a diphenoxo-bridged CuII(UVIO2) system, compound 2 is a star-shaped tetranuclear system where the cadmium(II) center is encapsulated in between three [CuIIL] moieties and the three isomorphous compounds 3–5 are trinuclear CuIIMIICuII-based (M = Co, Ni, Zn) two-dimensional, square-grid systems where the trinuclear units are bridged by μ1,5-dicyanamide ligands. In addition to the exploration of much less investigated Schiff base ligand family having four carbon atoms between the two imine nitrogen atoms, the types of structures presented here either have some novelties or are new examples and therefore deserves importance. The d–d spectra of copper(II)-diamagnetic metal ion complexes (1, 2 and 5) and the corresponding mononuclear copper(II) compound have been recorded with the aim to shed light on the correlation of d–d band position with the displacement of copper(II) from the least-squares basal plane, revealing excellent correlation.

This paper deals with the syntheses, characterization, crystal structures and electronic spectroscopy of one diphenoxo-bridged CuII(UVIO2) compound, one star-shaped highly symmetric CuII3CdII compound and three trinuclear CuIIMIICuII-based (M = Co/Ni/Zn), dicyanamide-bridged two-dimensional square-grid coordination polymers, derived from a less investigated Schiff base ligand. Unique examples, interesting structural aspects and excellent spectral correlation are described.Figure optionsDownload as PowerPoint slide