Toward Heteronuclear Molecular Re(I)-Cu(II) Boxes: Structural, Luminescent, and Magnetic Properties.

The bifunctional ligands of isonicotinic acid (Py-4-COOH) and 4-pyrid-4-ylbenzoic acid (Pybz-4-COOH) instead of polypyridines were therefore reacted with (Re(CO))(CNS) (CNS = cyanurate trianion), resulting in the formation of two trinuclear [(Re(CO))(CNS)(Py-4-COOH)] () and [(Re(CO))(CNS)(Pybz-4-COOH)] (), respectively. In the meantime, both complexes and are connected by three bifurcated hydrogen bonds between their carboxylic acid moieties Py-4-COOH and Pybz-4-COOH to form the supramolecular trigonal-prismatic and -antiprismatic structures, respectively. It is noted that complex can further react with copper(II) nitrate upon deprotonation to give nonanuclear [(Re(CO))(CNS)(Py-4-COO)]Cu(HO) (), where two trinuclear [(Re(CO))(CNS)(Py-4-COO)] moieties are connected by three penta-coordinate copper(II) ions, each coordinating to two carboxylates and three water molecules, to form the trigonal-prismatic structure. Surprisingly, addition of pyrazine (pz) in the synthetic process of complex resulted in serendipitous isolation of a rare example of octadecanuclear {[(Re(CO))(CNS)(Py-4-COO)]Cu(HO)(pz)} (), which can be regarded as a dimer of complex , connected by two bridging pz ligands. Interestingly, both complexes and are heteronuclear molecular Re(I)-Cu(II) boxes, constructed by a complex-as-a-ligand strategy. Furthermore, complexes and can exhibit respective low-energy luminescence at . 561 and 534 nm at room temperature upon photoexcitation, and complex is found to display antiferromagnetic coupling of -127.68 and -134.70 cm, possibly due to multiple hydrogen bonds inducing significant Cu(II)···Cu(II) coupling.