Functional Hybrid Materials Based on Layered Simple Hydroxide Hosts and Dicarboxylate Schiff Base Metal Complex Guests

The insertion of carboxysalen-type complexes into magnetic layered transition-metal simple hydroxides has provided new hybrid compounds. Three kinds of carboxysalen ligands have been used: an ethylenediamine bridge (SED-H2), a chiral cyclohexanediamine bridge [(S,S)-SCD-H2 and (R,R)-SCD-H2], and an aromatic o-phenylenediamine bridge (SBD-H2). The ccorresponding CuII, NiII, CoII, ZnII, MnIII, and AlIII complexes were synthesized and inserted into layered cobalt and copper hydroxides. The structural and spectroscopic investigations confirmed the successful insertion-grafting of the complexes leading to new layered hybrid materials in which the inserted complexes act as pillars between the inorganic layers. The use of carboxylate anchoring functions enabled some of the difficulties encountered during the previously reported insertion of sulfonatosalen complex analogues to be overcome, namely hydrolysis and decomplexation during the insertion reaction. Hence, in this work it was possible to insert a wide variety of complexes into layered simple hydroxides, including MIII complexes, for the first time. The insertion of chiral carboxysalen complexes led to the formation of chiral magnets in which chirality transfer to the inorganic layers was evidenced and seems to be favored by the carboxylate anchoring groups. Finally, magnetic characterization showed that the copper hydroxide hybrids exhibit overall antiferrimagnetic behavior, whereas the cobalt hydroxide hybrids present ferromagnetic ordering, with ordering temperatures ranging from 6.5 to 12.8 K. In this case the nature of the cation inserted between the layers influences the magnetic behavior of the hybrid, contrary to what was observed in the case of the sulfonate analogues.