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Spectrochemical and thermal behaviours of the 2,4- and 3,4-dimethoxybenzoates of rare earth elements

Ferenc Wieslawa (Maria Curie-Sklodowska University, Department of Inorganic and General Chemistry, Lublin, Poland)
Walków-Dziewulska Agnieszka (Maria Curie-Sklodowska University, Department of Inorganic and General Chemistry, Lublin, Poland)

The physicochemical properties and thermal stability in air of the 2,4- and 3,4-dimethoxybenzoates of rare earth elements were compared in order to observe the influence of the position of the -OCH3 substituent on their thermal stability. The complexes of these two series are crystalline, hydrated or anhydrous salts with colours typical of trivalent rare earth ions. The carboxylate group is a bidentate, chelating ligand. The thermal stability of the 2,4- and 3,4-dimethoxybenzoates of the lanthanide elements was studied in the temperature range 273-1173 K. The positions of methoxy- groups in the benzene ring influence the number of crystallization water molecules in the complexes and their thermal stability, which is connected with the varying influence of inductive and mesomeric effects of the -OCH3 substituent on the electron density in the benzene ring.

Keywords: 2,4- and 3,4-dimethoxybenzoates of rare earth elements, thermal stability of complexes, influence of methoxy-groups on the properties of dimethoxybenzoates, influence of substituents