Europium(ii) compounds: Simple synthesis of a molecular complex in water and coordination polymers with 2,2′-bipyrimidine-mediated ferromagnetic interactions

Reaction between EuCl₂ and 2,2′-bipyrimidine (bpm) in de-oxygenated water afforded a cationic molecular complex [EuCl(bpm) ₂(H₂O)₄][Cl]·H₂O (1). When performed in an organic solvent such as THF or methanol, the same reaction yielded a 3-dimensional coordination polymer of formula [EuCl ₂(bpm)(MeOH)_0.5]_∞ (2) in which both bpm and the chloride ions act as linkers between the Eu(II) ions. Upon replacing Cl^- by I^-, two coordination polymers of formula {[Eu(bpm)₂(H₂O)₃][I]₂·0.5bpm} _∞ (3) and {[Eu(I)(bpm)(MeOH)][I]}_∞ (4) were obtained from reaction in water and methanol, respectively. All these compounds were characterized by X-ray crystallography. Investigations of the magnetic properties revealed a weak antiferromagnetic coupling in 2, while 3 and 4 showed a weak ferromagnetic coupling at low temperature.