KINETIC-STUDY OF THE THERMAL DEHYDRATION OF COPPER(II) DIPICOLINATES - CRYSTAL AND MOLECULAR-STRUCTURE OF CU(II) (PYRIDINE 2,6-DICARBOXYLATO) DIHYDRATED AND TRIHYDRATED
Ee. Sileo et al., KINETIC-STUDY OF THE THERMAL DEHYDRATION OF COPPER(II) DIPICOLINATES - CRYSTAL AND MOLECULAR-STRUCTURE OF CU(II) (PYRIDINE 2,6-DICARBOXYLATO) DIHYDRATED AND TRIHYDRATED, Journal of physics and chemistry of solids, 58(7), 1997, pp. 1127-1135
As a basis for the description of dehydration mechanisms, the molecula
r structures of two copper(II) dipicolinates, Cu(dipic).2H(2)O (tricli
nic) and Cu(dipic).3H(2)O, are presented and compared with those of ot
her copper(II) dipicolinates. The kinetics of the isothermal dehydrati
on of the monoclinic and triclinic polymorphs of Cu(dipic).2H(2)O were
measured. The monoclinic variety dehydrates in a two-step process; a
linear cult relationship is found for the first step and a two-dimensi
onal diffusion-controlled reaction (D2) law ((1 - alpha) In(1 - alpha)
+ alpha = kt) for the second. Triclinic Cu(dipic).2H(2)O dehydrates i
n a one-step process. The relation between alpha and time is linear at
lower temperatures but gradually changes to an Avrami-Erofe'ev (A(2))
model (- 1n(1 - alpha)(1/n) = kt) at higher temperatures. A qualitati
ve model based on optical microscopic observations, structural determi
nations and thermogravimetric data is proposed. The general relationsh
ip between dehydration behavior and structure in this series of compou
nds is discussed. (C) 1997 Elsevier Science Ltd. All rights reserved.