Photoactivatable CO-Releasing Properties of {Ru(CO)2}-Core Pyridylbenzimidazole Complexes and Reactivity towards Lysozyme

5 years ago

Photoactivatable CO-Releasing Properties of {Ru(CO)2}-Core Pyridylbenzimidazole Complexes and Reactivity towards Lysozyme

Ahmed M. Mansour, Ola R. Shehab

The photoinduced CO-releasing properties of [RuLPy(CO)2Cl2] (1), [Ru(LPy2Bz-ĸ2N1,N2)(CO)2Cl2] (2), and [Ru(LPy2Bz–Et-ĸ3N1,N2,N3)(CO)2(Cl)]·PF6 (3) [LPy = 2-(2-pyridyl)benzimidazole, LPy2Bz = 2,6-bis(benzimidazole-2′-yl)pyridine, and LPy2Bz–Et = 2,6-bis(1-ethyl-benzimidazol-2′-yl)pyridine] in both DMSO and reduced myoglobin solution are reported. Complexes 1 and 2 release CO upon illumination at 365 nm. The bidentate chelation mode of LPy2Bz in 2 is changed into a meridional tridentate mode upon the ethylation of the benzimidazolic NH groups, 3. The extension of the conjugation system and the shift of the MLCT band into the visible region in 3 give rise to the RuII dicarbonyl complex capable of releasing CO at 468 nm. During illumination of 2, the chelation mode of LPy2Bz is changed from ĸ2N1,N2 to ĸ3N1,N2,N3, as monitored by solution NMR spectroscopic studies. The spectral properties were studied by TD-DFT calculations. The interaction of 1–3 with hen-egg-white lysozyme, as a biocompatible carrier, has been studied by ESI-MS and UV/Vis spectroscopy in the dark and upon illumination. Stable protein adducts containing the RuII(CO)2 moiety, capable of photoinduced release of CO, are formed. The photoinduced CO-releasing properties of three Ru complexes are reported. The presence of a free arm close to the RuII ion prevents, by its coordination, the back-coordination to CO π* orbitals, making the release process irreversible. The characteristic signals of the bidentate mode disappear and a new group of signals, corresponding to a meridional tridentate mode, grow during illumination.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/ejic.201700898