Photophysical Properties of Ruthenium(II) Polypyridyl DNA Intercalators: Effects of the Molecular Surroundings Investigated by Theory

• Published in: Chemistry : a European journal Vol. 20; no. 40; pp. 12901 - 12909
• Main Authors: Véry, Thibaut, Ambrosek, David, Otsuka, Miho, Gourlaouen, Christophe, Assfeld, Xavier, Monari, Antonio, Daniel, Chantal
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 26.09.2014; WILEY‐VCH Verlag; Wiley Subscription Services, Inc; Wiley-VCH Verlag
• Subjects: 2,2'-Dipyridyl - chemistry; 2,2'-Dipyridyl - pharmacology; Acetonitrile; Chemical Sciences; Chemistry; Density; Deoxyribonucleic acid; DNA; DNA - chemistry; Electronics; Environment effects; Excitation; Intercalating Agents - chemistry; Intercalating Agents - pharmacology; intercalations; Ligands; Luminescence; Mathematical analysis; Models, Molecular; Organometallic Compounds - chemistry; Organometallic Compounds - pharmacology; Phenanthrenes - chemistry; Phenanthrenes - pharmacology; Phenanthrolines - chemistry; Phenanthrolines - pharmacology; Phenazines - chemistry; Phenazines - pharmacology; photophysics; quantum chemistry; ruthenium; Ruthenium - chemistry; Ruthenium - pharmacology; Theory; quantum chemistry; ruthenium; photophysics; DNA; intercalations
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201402963

The environmental effects on the structural and photophysical properties of [Ru(L)2(dppz)]2+ complexes (L=bpy=2,2′‐bipyridine, phen=1,10‐phenanthroline, tap=1,4,5,8‐tetraazaphenanthrene; dppz=dipyrido[3,3‐a:2′,3′‐c]phenazine), used as DNA intercalators, have been studied by means of DFT, time‐dependent DFT, and quantum mechanics/molecular mechanics calculations. The electronic characteristics of the low‐lying triplet excited states in water, acetonitrile, and DNA have been investigated to decipher the influence of the environment on the luminescent behavior of this class of molecules. The lowest triplet intra‐ligand (IL) excited state calculated at λ≈800 nm for the three complexes and localized on the dppz ligand is not very sensitive to the environment and is available for electron transfer from a guanine nucleobase. Whereas the lowest triplet metal‐to‐ligand charge‐transfer (3MLCT) states remain localized on the ancillary ligand (tap) in [Ru(tap)2(dppz)]2+, regardless of the environment, their character is drastically modified in the other complexes [Ru(phen)2(dppz)]2+ and [Ru(bpy)2(dppz)]2+ upon going from acetonitrile (MLCTdppz/phen or MLCTdppz/bpy) to water (MLCTdppz) and DNA (MLCTphen and MLCTbpy). The change in the character of the low‐lying 3MLCT states accompanying nuclear relaxation in the excited state controls the emissive properties of the complexes in water, acetonitrile, and DNA. The light‐switching effect has been rationalized on the basis of environment‐induced control of the electronic density distributed in the lowest triplet excited states. Get in there! The environmental effects on the structural and photophysical properties of [Ru(L)2(dppz)]2+ complexes (L=bpy=2,2′‐bipyridine, phen=1,10‐phenanthroline, tap=1,4,5,8‐tetraazaphenanthrene; dppz=dipyrido[3,3‐a:2′,3′‐c]phenazine), used as DNA intercalators, have been studied theoretically (see figure).