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Photophysical Properties of Ruthenium(II) Polypyridyl DNA Intercalators: Effects of the Molecular Surroundings Investigated by Theory
Author(s) -
Véry Thibaut,
Ambrosek David,
Otsuka Miho,
Gourlaouen Christophe,
Assfeld Xavier,
Monari Antonio,
Daniel Chantal
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201402963
Subject(s) - excited state , ruthenium , chemistry , phenazine , photochemistry , ligand (biochemistry) , nucleobase , acetonitrile , intercalation (chemistry) , bipyridine , triplet state , luminescence , molecule , electron transfer , crystallography , dna , crystal structure , materials science , inorganic chemistry , atomic physics , organic chemistry , biochemistry , physics , receptor , catalysis , optoelectronics
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 ( 3 MLCT) 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 (MLCT dppz/phen or MLCT dppz/bpy ) to water (MLCT dppz ) and DNA (MLCT phen and MLCT bpy ). The change in the character of the low‐lying 3 MLCT 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.