Structural and thermal studies on some morpholine complexes

Abstract A series of mono metallic and hetero-metallic morpholine complexes were synthesized and characterized by elemental analysis, spectral (IR, UV-VIS and ESR) studies, room-temperature magnetic susceptibility and thermal analysis techniques(TG, DTG, DTA, DSC). IR spectra showed, that morpholine behaves as a monodentate ligand in all the complexes through nitrogen atom only except in case of [CuZn(MOR) 3 Cl 4 ]·2H 2 O and [CoZn(MOR) 5 (H 2 O) 2 Cl 4 ]·H 2 O complexes morpholine acts as a bidentate ligand through nitrogen and oxygen atoms. ESR was studied for copper complexes, were of isotropic nature. The geometry suggested to be octahedral in all complexes except in [CuZn(MOR) 3 Cl 4 ]·2H 2 O and [CuNi(MOR) 2 Cl 4 ]·4H 2 O complexes were tetrahedral. Molecular modeling techniques and quantum chemical methods have been done for morpholine to calculate charges, bond lengths, bond angles, dihedral angles, electronegativity (χ), chemical potential (μ), global hardness (η), softness (σ), and the electrophilicity index (ω). The thermal decomposition of the complexes and the ligand were monitored by TGA, DTG, DTA and DSC techniques under N 2 atmosphere. The decomposition mechanisms were suggested. Studying the effect of pH on the electronic absorption spectra of morpholine, combined with determination of dissociation constants of morpholine (pKa 1  = 5.283 ± 0.01, pKa 2  = 8.373 ± 0.01). The biological activities of morpholine and all the complexes are tested against Gram positive and Gram negative bacteria. The results showed a well considerable activity for some complexes against different organisms.