Carboxylate-bridged complexes of transition metals, M^II = Mn^II, Fe^II, Co^II, Ni^II, Cu^II, were synthesized by reaction of M^II salts with (R)-mandelic acid ((R)-2-hydroxyphenylacetic acid), methoxymandelic acid (racemic) (2-methoxyphenylacetic acid) and (R)-malic acid ((R)-2-hydroxybutanedioic acid) under hydrothermal conditions. A wide variety of structures has been obtained, with various dimensionalities: 3D networks when the malic diacid is used, 2D networks with the mandelic acid, 1D isolated chains organised in planes for the Co and Cu compounds with MeOmandelic acid and monomers for the Ni analogue. These complexes have been fully characterized structurally and magnetically. During the reaction process, the (R)-mandelic ligand undergoes a racemisation reaction but the compounds obtained with (R)-malic acid are chiral and exhibit metal-centred circular dichroism. Extensive magnetic characterization of all compounds indicates rather weak coupling interactions between paramagnetic centres linked through carboxylate bridges. Curie-like paramagnetic, antiferromagnetic, ferromagnetic or weak ferromagnetic behaviour was observed and is discussed on the basis of the structural features. The bimetallic compounds Mn_0.63Co_0.37(R)-malate monohydrate (12) and Mn_0.79Ni_0.21(R)-malate monohydrate (13) are new examples of chiral magnets.

A luminescent Zn₂Dy single-molecule magnet.

Discrete and extended architectures based on the association of lanthanide ions with two derivatives of cinnamic acid (2-methoxycinnamic acid and 3-methoxycinnamic acid) have been synthesized and characterized by IR spectroscopy, elemental analyses, X-ray diffraction and magnetic measurements. The use of the 2-methoxycinnamic ligand enables the synthesis of a series of dinuclear complexes (Ce³⁺ (1), Nd³⁺ (2), Gd³⁺ (3), Dy³⁺ (4)), while the presence of 3-methoxycinnamic acid induces the formation of one-dimensional coordination polymers (Ce³⁺ (5), Nd³⁺ (6), Dy³⁺ (7)). Investigations of the magnetic properties of the complexes reveal that they all exhibit field-induced slow relaxation of the magnetisation, mainly induced by Raman and direct relaxation processes.