Deciphering the role of neutral diruthenium complexes in protein binding.

The charge of paddlewheel diruthenium complexes has a major role in defining their interaction with proteins: negatively charged complexes bind proteins non-covalently, while cationic complexes form adducts where the Ru core binds to Asp side chains at the equatorial sites, or to the main chain carbonyl groups or the side chains of His, Arg or Lys residues at the axial sites. Here we study the interactions of the neutral compound [Ru(D-p-FPhF)(OCCH)(OCO)]·3HO (D-p-FPhF = N,N'-bis(4-fluorophenyl)formamidinate), a very rare example of a paddlewheel diruthenium compound with three different equatorial ligands, with the model protein bovine pancreatic ribonuclease (RNase A) by means of UV-visible absorption spectroscopy, circular dichroism (CD), electrospray ionization mass spectrometry (ESI-MS) and X-ray crystallography. It is the first attempt to investigate the binding of a neutral diruthenium compound to a protein.

Mitochondria Targeting with Luminescent Rhenium(I) Complexes.

Two new neutral -[Re(CO)₃(phen)L] compounds (,), with phen = 1,10-phenanthroline and L = O₂C(CH₂)₅CH₃ or O₂C(CH₂)₄C≡CH, were synthetized in one-pot procedures from -[Re(CO)₃(phen)Cl] and the corresponding carboxylic acids, and were fully characterized by IR and UV-Vis absorption spectroscopy, ¹H- and C-NMR, mass spectrometry and X-ray crystallography. The compounds, which display orange luminescence, were used as probes for living cancer HeLa cell staining. Confocal microscopy revealed accumulation of both dyes in mitochondria.