Development of metal-based luminescent probes for applications in biomolecular structure and dynamics

New transition-metal complexes containing luminescent properties have been designed and synthesized for application as structural probes for biomolecules. Potential DNA intercalators, 2- amino-anthracene substituted triosmium clusters, were synthesized by the reactions of 2-aminoanthracene with [Os3(CO)10(CH3CN)2]. The products [Os3(CO)10(μ-η2-(N-C(1))-NH2C14H8)(μ- H)], [Os3(CO)10(μ-η2-(N-C(3))-NHC14H9)(μ-H)], [Os3(CO)9(μ-η2-(N-C(3))-NHC14H8)(μ-H)2] and [Os3(CO)9(μ3-η2-(N-C(3))-NHC10H9)(μ-H)] obtained from this reaction have been structurally characterized by spectroscopic, photophysical and electrochemical techniques. Solid state structures are also reported for the complexes [Os3(CO)10(μ-η2-(N-C(3))-NHC14H9)(μ-H)] and [Os3(CO)9(μ-η2-(N-C(3))-NHC14H8)(μ-H)2]. To investigate bio-macromolecular dynamics on the sub-microsecond-to-microsecond timescale, a series of ruthenium based mono-nuclear metalligand charge-transfer complexes (MLCs) of formula [XRu(CO)(L–L)(L′)2][PF6] (X = H, TFA, Cl; L–L = 2,2′-bipyridyl, 1,10-phenanthroline, 5-amino-1,10-phenanthroline and 4,4′- dicarboxylic-2,2′-bipyridyl; L′2 = 2PPh3, Ph2PC2H4PPh2, Ph2PCH=CHPPh2) have been synthesized from the starting complex K[Ru(CO)3(TFA)3] (TFA = CF3CO2) by first reacting with the phosphine ligand, followed by reaction with the L–L and anion exchange with NH4PF6. In the case of L–L = phenanthroline and L′2 = 2PPh3, the neutral complex Ru(Ph3P)(CO)(1,10- phenanthroline)(TFA)2 is also obtained and its solid state structure is reported. Solid state structures are also reported for the cationic complexes where L–L = phenanthroline, L2 = 2PPh3 and X = Cl and for L–L = 2,2′-bipyridyl, L2 = 2PPh3 and X = H. All the complexes were characterized in solution by a combination of 1H and 31P NMR, IR, mass spectrometry and elemental analyses. These complexes contain only one chelating heterocycle, which decreases the molecular symmetry and thereby increases the luminescence anisotropy. The photophysical and structural properties of these complexes indicated that these complexes can be used as potential probes to study bio-macromolecular dynamics in the presence of oxygen. The carboxy- and amine-substituted diimine ligands in [HRu(CO)(4,4’-dicarboxy-bipyridyl)(PPh3)2][PF6] and [(TFA)Ru(CO)(dppene)(5-amino-1,10phen)][PF6] have been covalently-conjugated with biomolecules by simple ligand modifications. Complex [HRu(CO)(4,4’-dicarboxybipyridyl)( PPh3)2][PF6] has been conjugated to dipalmitoylphosphatidylethanolamine (DPPE) and complex [(TFA)Ru(CO)(dppene)(5-amino-1,10-phen)][PF6] conjugated to DPPE and cholesterol. The lipid and cholesterol conjugates were characterized by spectroscopic and photophysical techniques. These conjugates were incorporated in 100 nm-diameter-unilamellar lipid-membrane vesicles to investigate the photophysical properties of the probes in a model membrane environment and to evaluate the utility of these probes for investigating the physical properties of lipid membranes. These studies revealed an unusual blue shift in their luminescence in the case of the lipid conjugates while the cholesterol conjugate did not. Anisotropy studies of the conjugates revealed details about the probe dynamics in the vesicle environment