An imidazolidine-phenolate ligand HL yields quadruple-bridged (μ-NCN)(μ-O) ferromagnetic dinuclear nickel and cobalt complexes. Both kinds of bridges contribute to the ferromagnetic coupling, but the ferromagnetism of these samples is mainly ascribed to the double μ-O links, on the basis of density functional theory calculations. These studies demonstrate not only that the short M-O-M angles of the MO cores favors the parallel alignment of the electrons but also that these angles are the optimal ones for maximizing the ferromagnetic contribution in these complexes. And these acute angles, close to 90°, are predetermined by the geometrical constrictions imposed by the ligand itself. Thus, HL is an uncommon polydentate donor that induces ferromagnetism per se in its metal complexes by strict control of one geometric parameter, the M-O-M angle.

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Octanuclear [Ni 2 (L)(H 2 O) 2 ] 4 •7CH 3 OH•12H 2 O (1•7CH 3 OH•12H 2 O) and tetranuclear [Cu 2 (HL)(CH 3 OH) 1.5 (H 2 -O) 1.5 ] 2 (ClO 4 ) 2 •2CH 3 OH (2•2CH 3 OH) (H 4 L = 4-carboxysalpn or N,N′-bis(4-carboxysalicylidene)-1,3-propylenediamine) are obtained from similar reactions, the main difference coming from the slightly higher pH of the medium for the nickel reaction vessel. This small disparity of the pH leads to full deprotonation of the ligand in 1 while one of the carboxylic functions remains protonated in 2, making it unable to act as a donor and, therefore, justifying the different nuclearity of both compounds. In any case, the isolation of complexes of H 4 L with limited nuclearity is remarkable, given that similar carboxysalen-based ligands lead to coordination polymers when the carboxylic functions are partially or fully deprotonated. This indicates that not only the pH of the medium but also the longer propylene spacer of the Schiff base have a fundamental role in the nuclearity of the isolated products.metalloligands, joined through the fully deprotonated carboxylic functions. 2•2CH 3 OH is a molecular rhomboid, built from two [Cu 2 (HL)(CH 3 OH) 1.5 (H 2 O) 1.5 ] + metallotectons, linked through the only deprotonated carboxylic group of the ligand, the protonated carboxylic moiety remaining uncoordinated. In addition, the magnetic analysis of both polynuclear compounds shows that they are antiferromagnetic in nature and that the magnetic interaction between dinuclear metallotectons is negligible.

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2,2´-(2-(2-hydroxyphenyl)imidazolidin-1,3-diyl)diethanol (H 3 L) was obtained by condensation between 2-hydroxybenzaldehyde and N,N'-bis(2-hydroxyethyl) [3]. In spite of this, the ability of this kind of donor to bind to metal atoms is still scarcely explored. As a continuation of our studies in the interaction of imidizolidine ligands with d-block metal ions [4], we describe herein the synthesis of the H 3 L (Scheme 1) and its stability in the presence of Zn