Structure and luminescence properties of monomeric and dimeric Re(I) complexes with dicarboxylic acid-2,2'-bipyridine ligands.

The luminescence properties of Re(I) complexes incorporating the dcbpy ligand (dcbpy = n,n'-dicarboxylic acid-2,2'-bipyridine; n = 3, 4) were investigated as well as their utility as Pb(2+) sensors. An unusual binuclear complex of the 3,3'- species was isolated. The emission intensity and lifetime for all complexes were found to be highly temperature-dependent, with quantum yields and lifetimes dramatically greater at 77 K than at room temperature. The monomeric 3,3'-dcbpy Re(I) complex demonstrates nearly 1:1 binding with Pb(2+). The effect of this lead binding on the emission intensity is great, but the low quantum yields allow only for detection of the metal at the micromolar level. The binding of Pb(2+) to the 4,4'-dcbpy complex is modeled and the interaction is demonstrated to involve two binding sites.