The physico-chemical properties and thermal stability in air of rare earth element 4-chloro-2-nitro- and 4-chloro-3-nitrobenzoates of the general formulae Ln(C7H3NO4Cl)3
2H2O were compared and the influence of the position of the Cl and NO2 substituents on their thermal stabilities was investigated. The complexes of both series are crystalline, hydrated salts with colours typical of Ln3+. The carboxylate group in these complexes is a bidentate, chelating ligand. The NO2 group in the chloronitro complexes does not undergo isomerization. The thermal stabilities of the 4-chloro-3-nitrobenzoates of rare earth elements were studied in the temperature range 293–1173 K, but those of 4-chloro-2-nitrobenzoates of those elements were studied only at 293–523 K because they decompose explosively above 523 K. The positions of the Cl and NO2 substituents on the benzene ring influence the thermal properties of the complexes and their decomposition mechanisms. The different thermal stabilities of the complexes are connected with various inductive and mesomeric effects of the Cl and NO2 substituents on the electron density in benzene ring.
The physico-chemical properties and thermal stability in air of light lanthanide 2,3-, 2,4- and 3,4-dimethoxybenzoates were
compared and the influence of -OCH3 substituent on their thermal stability was investigated. The complexes of these series are crystalline, hydrated or anhydrous
salts with colours typical of Ln3+ ions. The carboxylate group is a bidentate, chelating (2,4- and 3,4-dimethoxybenzoates) or tridentate chelating and bridging
ligand (2,3- dimethoxybenzoates). The thermal stability of 2,4- , 3,4- and 2,3- dimethoxybenzoates of light lanthanides was
studied in the temperature range 273-1173 K. The positions of methoxy groups in benzene ring influence the thermal properties
of the complexes and their decomposition mechanism.
Authors:W. Ferenc, B. Bocian, and A. Walków-Dziewulska
The conditions of the formation of yttrium(III) and lanthanide(III) 2-chloro-5-nitrobenzoates were studied and their quantitative
composition and solubilities in water at 298 K were determined. The compounds are dihydrates and their solubilities are of
the order of 10-3 mol dm-3. The FTIR, FIR and X-ray spectra for the complexes were recorded. All complexes are crystalline compounds. Their thermal
decomposition was studied only in the range 293-523 K since on heating above 523 K the complexes decompose explosively. Hydrated
2-chloro-5-nitrobenzoates of rare earth elements lose two crystallization water molecules in one step. The enthalpy of dehydration
process was established and the magnetic moments of the complexes were determined in the range 77-300 K. The compounds obey
the Curie-Weiss law. The 4f electrons do not participate in the formation of the Ln-O bonds.