Novel Binuclear Chromium(III) Complexes with Potential Application as Building Blocks in Single Molecule Magnets Synthesis

Single-Molecule Magnets (SMMs) exhibit a large range of novel properties that arouse the interest of the technological and scientific communities. However, there is a lack of rational synthetic routes, since the majority of descriptions mostly involve one-pot and uncontrolled self-assembly routes, preventing the rationalization of the synthetic process, thus raising many difficulties in the study and improvement of the desired properties. The objective of this work is to develop a rational synthetic route for SMMs based on building blocks using RC(CH2OH)3 type pre-ligands in reaction with chromium(III) ions and to characterize the obtained products by spectroscopic and structural techniques. The building block approach is known by its large possibility of chemical tailoring, and while combined with the redox stability of chromium(III) ion, demonstrates an ability to direct the route into a high yield single-product route. We report the synthesis and characterization of three novel binuclear complexes of general formula [Cr2Cl4{RC(CH2O)(CH2OH)2}2], where R = Me (complex 1, Fig.1), Et (complex 2, Fig.2) or NH2 (whose structure is under refinement) obtained in mild synthetic conditions. For all products, FTIR spectroscopy suggests the obtainment of novel products whose structures were confirmed by single-crystal X-ray diffraction while the electronic and EPR spectra are compatible with the expected for the structures. Also, they are already being employed in a, still ongoing, synthesis of SMMs directed by the chemical stability of the chromium(III) ion to yield strictly one product.