Self-assembly, structures, and photophysical properties of 4,4′-bipyrazolate-linked metallo-macrocycles with dimetal clips

Abstract

By employing functional diimine ligands coordinated dipalladium(II,II) or diplatinum(II,II) clips as corners and the coplanar 4,4′-bipyrazolate dianion (L 2-) ligand as linker, a series of bipyrazolate-bridged metallo-macrocycles, namely, [M 8L 4](NO 3) 8 (M = Pd(dmbpy), 1; Pd(bpy), 2; Pt(bpy), 3a; Pd(phen), 4; Pt(phen), 5; Pd(15-crown-5-phen), 6; Pd(18-crown-6-phen), 8; Pd(benzo-24-crown-8-phen), 10a; Pt(15-crown-5-phen), 7a, Pt(18-crown-6-phen), 9a; Pt(benzo-24-crown-8-phen) , 11a) and [M 6L 3](NO 3) 6 (M = Pt(bpy), 3b; Pt(15-crown-5-phen), 7b; Pt(18-crown-6-phen), 9b; Pd(benzo-24-crown-8-phen), 10b; Pt(benzo-24-crown-8-phen), 11b), have been synthesized through a directed self-assembly approach that involves spontaneous deprotonation of the 1H-bipyrazolyl ligands in aqueous solution. All these compounds have a crown-shaped cavity that can serve as host to solvent molecules and anions. The structures are characterized by elemental analysis, 1H and 13C NMR, ESI-MS, and in the cases of 1a (the BF 4 - salt of 1), 2a (the BF 4 - salt of 2), and 3b by single-crystal X-ray diffraction analysis. Photophysical properties for complexes 1 and 2 are discussed. © 2008 American Chemical Society.