Spectral, magnetic, thermal and biological studies on Ca(II) and Cu(II) complexes with a novel crowned Schiff base

A series of complexes [Ca(HL)(OH2)4]Cl2·4H2O (1), [CuL2]·2H2O (2) and [Cu{Ca(L)(OH2)2}2]Cl4·H2O (3) (HL: 2-hydroxy-8-methyl-tricyclo[7.3.1.02.7]tridec-13-N-4′(benzo-15-crown-5-ether)-imine) were synthesised and characterised. The features of complexes have been assigned from microanalytical data, IR, UV–Vis–NIR and EPR spectra, magnetic data at room temperature as well as thermal analysis. The ligand coordinates through azomethinic nitrogen and hydroxylic oxygen at Cu(II) and through etheric oxygen at Ca(II). The electronic and EPR spectra suggest a square planar stereochemistry for Cu(II). The thermal analysis evidenced that thermal transformations are complex processes according to DTG and DTA curves including (crystallisation or coordination) water elimination, thermolyses and oxidative degradation of Schiff base. The results of the biological assays revealed that the complexes exhibited good antimicrobial activity against planktonic and sessile bacterial and fungal strains.