NO Photorelease from a Ruthenium Complex Assisted by Formation of a Supramolecular Dimer

Douglas Mateus,Ana Paula Batista,Sofia Nikolaou,Renata Rodrigues

doi:10.21577/0103-5053.20200090

Douglas Mateus, Ana Paula Batista + Show 2 more

Open Access

https://doi.org/10.21577/0103-5053.20200090

Copy DOI

Abstract

This work presents the NO release from compound [Ru(biq)2(H2O)(NO)](PF6)3 (biq = 2,2’-biquinoline) with visible light irradiation (λirrad = 660 nm), assisted by the low-absorbing photosensitizer [Ru(biq)2Cl2]. The structure of both compounds were characterized by means of ESI-MS (electrospray ionization mass spectrometry). The NO+ stretching, ν(NO) = 1995 cm-1, is atypically shifted to higher energy. This observation, along with the E1/2 = 0.49 V (vs. Ag/AgCl) assigned to the Ru2+/3+ redox pair observed for compound [Ru(biq)2Cl2] and its photoreactivity in solution suggest that the RuII ion, when coordinated to two biquinolines, behaves as a hard Pearson acid. Molecular modelling results confirmed the typical geometry distortion of ruthenium-polypyridine complexes bearing sterically hindered ligands. They also suggest the formation of a supramolecular dimer, assembled by weak interaction between biquinoline ligands from each compound, that is claimed to be responsible for the high efficiency of the NO photorelease bimolecular sensitization.

Highlights

Ruthenium complexes combined with polypyridines have captured the interest of the scientific community for many years, especially those combined with the 2,2’-bipyridine ligand
The photolability of biquinoline coordination complexes are observed for compound 1 and it has been atributted mostly to geometry distortions of the octahedral geometry rather than to electronic effects
Due to the high lability of the chloro ligands introduced by the steric bulk biquinoline ligand in compound 1, the actual photosensitizer was the solvated complex [Ru(biq)2(AN)2]2+

Summary

Introduction

Ruthenium complexes combined with polypyridines have captured the interest of the scientific community for many years, especially those combined with the 2,2’-bipyridine ligand. Far fewer reports are available on the synthesis and characterization of 2,2’-biquinoline analogs: searching for “ruthenium” and “2,2’-biquinoline” yields modest 74 results. More π-acid ligands than 2,2’-bipyridine are attractive to biological applications, since they lower the energy of the charge transfer states. On the other hand, using bulk ligands such as 2,2’-biquinoline or 2,2’-terpyridine introduces an exacerbated lability of monodentate ancillary ligands. That can make it challenging to handle such complexes in solution but can be explored to control the delivery of relevant molecules.[10,11]

Methods

Results

Conclusion