Thermally-induced phase transition of zinc(II) diamine complexes in the solid state

Abstract

ZnLCl 2·0.5H 2O and ZnL 2X 2· nH 2O (L = N-2(hydroxyethyl)-1,2-ethanediamine: X = Br, 0.5SO 4, 0.5SeO 4 and n = 0.5–2) have been synthesized and thermal investigations have been carried out in the solid state. ZnLCl 2·0.5H 2O and ZnL 2Br 2·0.5H 2O show endothermic reversible phase transitions (135.0–152.0° C; Δ H = 1.6 kJ mol −1 and 127.0–144.5 ° C; Δ H = 10.4 kJ mol −1, respectively) after dehydration. ZnL 2SO 4·2H 2O becomes dehydrated at 100° C and on further heating undergoes an exothermic irreversible phase transition (109.5–146.0° C; Δ H = −9.5 kJ mol −1), whereas ZnL 2SeO 4· H 2O first undergoes dehydration at 134° C and then an endothermic irreversible phase transition occurs (141.5–171.5° C; Δ H = 14.2 kJ mol −1)