Synthesis, Binding Studies, and The Photophysics of Rhenium(I) Diimine Surfactant Complexes with Serum Albumins

Rhenium(I) tricarbonyl diimine complexes have emerged as promising tools in bioinorganic chemistry due to their tunable photophysical properties and potential for biomolecular interaction. This study reports the synthesis of four amphiphilic Re(I) diimine complexes, fac-[Re(CO)<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>(α-diimine)(4-C<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf>py)]CF<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>SO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>(1a-1d), using different substituted bipyridines as a-diimine ligands. Their binding affinity toward Human serum albumin (HSA) and Bovine serum albumin (BSA) was systematically evaluated using spectroscopic techniques. Absorption and emission spectra suggest that these complexes exhibit MLCT (metal-to-ligand charge transfer) transitions, while binding constants (K) obtained from Hill's equation indicate strong interactions, especially for the more hydrophobic complexes. These findings support the potential of Re(I) complexes as effective protein-targeting agents in drug delivery and diagnostic imaging applications.