Unusual photophysics of a rhenium(I) dipyridophenazine complex in homogenous solution and bound to DNA

• Published in: Journal of the American Chemical Society 1995-07, Vol.117 (27), p.7119-7128
• Main Authors: Stoeffler, H D, Thornton, N B, Temkin, S L, Schanze, K S
• Format: Article
• Language: English
• ISSN: 0002-7863
• DOI: 10.1021/ja00132a012

The photophysics of [fac-(dppz)Re super(I)(CO) sub(3)(4-MePy)][Cl] (1, where dppz = dipyrido[3,2-a:2',3'-c]phenazine and 4-MePy = 4-methylpyridine) have been examined in organic solvents and in aqueous solution with and without calf thymus DNA. Emission and nanosecond to microsecond transient absorption studies of 1 in organic solvents such as MeOH, MeCN, and CH sub(2)Cl sub(2) indicate that the lowest excited state of the complex is a dppz-based intraligand triplet state ( super(3)IL sub(dppz)). The super(3)IL sub(dppz) state is characterized by weak room temperature phosphorescence and a strong T sub(0) arrow right T sub(n) absorption band with lambda sub(max) = 470 nm. Absorption and emission studies of 1 in aqueous solution with added DNA indicate that the complex binds to the biopolymer, persumably by intercalation of the dppz ligand. Complex 1 is non-luminescent in aqueous solution; however, super(3)IL sub(dppz) phosphorescence is observed from the DNA-bound form of the complex in aqueous solution. The super(3)IL sub(dppz) assignment for the emission from the DNA-bound complex is supported by the observation of the characteristic T sub(0) arrow right T sub(n) transient absorption feature at 470 nm in the absorption-difference spectrum of the DNA-bound complex.