Thermal studies of 1,2-Propanediamine complexes of zinc (II) and cadmium (II) in the solid phase

Abstract

[ML₃]X₂•nH₂O, where M = Zn^II and Cd^II; L =1,2-propanediamine; X = Cl⁻, Br⁻, 0.5SO₄²⁻ and 0.5SeO_42- and n =1, 1.5, and 2, have been synthesized and their thermal investigations carried out. ZnL_1.5 Cl₂, CdL_1.5X₂ (X = Cl⁻ and Br⁻) and CdLX₂ (X = Cl⁻, 0.5SO₄²⁻ and 0.5SeO₄²⁻) have been synthesized pyrolytically in solid state from their parent diamine complexes. These ML_1.5X₂ complexes are expected to exist as [ML₃][MX₄]. Only [CdL₃][CdBr₄] species has been synthesized from solution. Syntheses of ZnLCl₂, CdLCl₂ and CdLBr₂ from solution have also been reported. IR spectra suggest that symmetry of the chelate ring in mono (diamine) complexes is lowered in comparison to the other complexes. ML_1.5Cl₂ show isomorphism with each other. Thermal stability sequence of [ML₃]X₂ (X = Br⁻, 0.5SO₄²⁻ and 0.5SeO₄²⁻) is SO₄²⁻ <SeO₄²⁻ ≤Br⁻. [ZnL₃]X₂ and ZnLX₂ appear thermally more stable than those of cadmium complexes. All these complexes are thermally less stable than those of 1,2-ethanediamine complexes reported by us earlier.