Photophysical and photobiological properties of [Re(CO)3(phen)(nHo)]CF3SO3 complex, nHo = norharmane

FRANCO M. CABRERIZO; BERN EPE; IVAN MAISULS; GUILLERMO FERRAUDI; PEDRO M. DAVD GARA; GUSTAVO T. RUIZ

Santiago

Congreso; 25th Inter-American Photochemical Conference; 2016

?À-carbolines are a group of naturallyoccurring alkaloids derived from 9H-pyrido[3,4-b]indole or norharmane (nHo).These alkaloids are widespread in biological systems, having an active role indifferent photosensitizing processes. Tricarbonyl rhenium complexes withpolypyridyl and bioactive molecules as ligands have an excellent thermal andphotochemical stability being, thus, appealing candidates for diverseapplications such as photodynamic therapy, anti-cancer drugs and radiotherapy.We show herein preliminary results about emissionspectroscopy and flash photolysis studies of anovel Re(CO)3(phen)(nHo)+ complex in different solvents. Also we show how this complexinteracts with DNA under UVA light. UV-Vis absorptionspectra show intense bands in the UV region of the spectra. These spectralfeatures are almost identical with those found in the electronic spectrum ofthe free nHo ligand and are therefore assigned to IL excitations in the nHoligand. The absorption band observed in the visible region exhibit typicallyintense and solvatochromic MLCT transitions from the metal dp to the lowest lying ligand p* orbital.Emission spectrum of the complex, recorded in methanol, shows an emitting bandat ~ 450 nm due to the deactivation of thelower nHo ligand-localized state, as it was described for free nHo. Emissionfrom MLCTRe?¨phen excited state have been observed in 530-560 nmrange. Moreover, the observed luminescence shows a strong dependence on theoxygen concentration. Both emission quantum yield and lifetime values, obtainedin all solvents tested, are compared with those reported for free nHo.The absorption patternsof the transient were registered by laser flash photolysis experiments, lexc = 351 nm. The absorption spectra in MeOH of the transient showed twomaxima at 380 and 460 nm, lifetime ~ 780 ns(oxygen free solution of the complex) The redox activity of the exited statewas measured by reductive quenching using TEA. Additionally, the efficiency of singletoxygen production was determined in acetonitrile.DNA photoinduced damage profile wasmeasured using the plasmid PM2 in presence of Re(CO)3(phen)(nHo)+ complex. After irradiation with an UVA lamp, the DNA wasincubated with a few reparation enzymes to find out the different DNA lesions.We could identify some kinds of damage, which were made by the complex, such assingle strand breaks (SSB), double strand breaks (DSB) and oxidized pyrimidines.