Synthesis, structure, magnetic properties and thermal behaviour of Ba–MII (MII = Mn, Co, Cu, and Zn) allylmalonates

Abstract

A series of Ba–M^II complexes with allylmalonic acid anions (Amal) [BaM^II(Amal)₂(H₂O)₃]_n (M^II = Mn (1), Co (2), Cu (3), and Zn (4)) were synthesized by the reaction of the corresponding transition metal sulfates and barium allylmalonate. The complexes were characterized by IR and EPR spectroscopy, elemental analysis, magnetochemical and solid phase thermal decomposition studies as well as powder and single-crystal X-ray crystallography. The main structural block {M^II(Amal)₂(H₂O)_x} (x = 1 for M = Cu, x = 2 for M = Mn, Co, and Zn) in 1–4 is formed by two chelate allylmalonate anions and water molecule(s), which are surrounded by Ba²⁺ ions. The magnetic measurements of paramagnetic compounds revealed weak ferromagnetic interactions between copper(II) ions in 3, and slow magnetic relaxation in non-zero field (H_DC = 1500 Oe) for 2. According to the TGA data of 1–4, they are decomposed via different pathways in the case of Mn^II, Co^II, Cu^II, and Zn^II since the metal ions catalyze different types of processes. However, all the complexes undergo polymerization of the allyl fragment.