The influence of alkaline cations on the mechanism and kinetics of dehydration of polymeric phthalatocuprate(II) dihydrates

Abstract

Thermal dehydration of two heterometallic complexes containing dianion of phthalic acid, pht, Na2[Cu(pht)2] · 2H2O, 1, and K2[Cu(pht)2] · 2H2O, 2, was investigated under non-isothermal conditions. Mechanism and kinetics of dehydration were analyzed in detail using TG/DSC/MS measurements, XRPD analysis and FT-IR spectroscopy. The reversibility of dehydration processes was identified. According to XRPD, dehydrated product of 1 maintains original structure, but dehydration of 2 undergoes structural transformation giving a dehydrated product of different crystal structure. In both cases dehydration process involves more than one elementary step, which was confirmed using isoconversional methods Deconvolution of this process using Fraiser-Suzuki function yielded two single step processes for 1 and 2. Subsequent kinetic analysis was performed using Màlek algorithm, resulting in the determination of kinetic triplets (Ea, A and f(α)) for each individual step. In addition, the dehydrated complexes were investigated as possible candidates for H2 adsorption, using molecular simulations.