INVESTIGADORES
CABRERIZO franco Martin
congresos y reuniones científicas
Título:
Photophysical, photochemical and photosensitizing properties of Re(CO)3(dppz)(nHo)+ complex (where dppz and nHo represent dipyrido[3,2-a:2,3-c]phenazine and norharmane ligands, respectively). A Laser Flash Photolysis study
Autor/es:
IVÁN MAISULS; GUILLERMO J. FERRAUDI; FRANCO M. CABRERIZO; GUSTAVO T. RUIZ
Lugar:
Villa Carlos Paz
Reunión:
Encuentro; XIII Encuentro Latinoamericano de Fotoquímica y Fotobiología (XIII ELAFOT); 2017
Resumen:
The formation of adducts between complexes of Re(I) andbiological macro-molecules such as DNA has been a subject of considerableinterest, mainly because of the potential biomedical and/or biotechnologicalapplications [1], among others. In this types of adducts, cationic transition metalcomplexes strongly interact with the negatively charged DNA backbone (i.e., phosphategroups). The intrinsic environment-sensitive photophysical and photochemicalproperties of Re(I) complexes make them suitable as DNA probes and/or TypeI-photosenzitizers [2].            Inthis work we present the first laser-flash photolysis characterization of theliving transient states involved when a novel Re(I)-complex, Re(CO)3(dppz)(nHo)+(with 9H-Pyrido[3,4-b]indole or nHoand dipyrido[3,2-a:2,3-c]phenazine ordppz as ligands) is subject to photoexcitation. Briefly, in neat MeOH, laser pulses(at 351 nm) induce the formation of a transient with λmax value of 460nm, assigned to the dppz triplet state, 3IL. The transientabsorbance decay was monoexponential with a τ = 3.54 μs. In pure H2O, this state is shutdownand, in consequence, the formation of such a transient was not observed. Theinteraction of photo-excited Re(CO)3(dppz)(nHo)+ with calf-thymusDNA (DNAct) was also investigated. Results show that, upon DNActaddition to the aqueous solution, and subsequent laser irradiations anabsorbance transient is observed, centered also at λmax = 460 nm. Thecontrast between the of [Re(CO)3(dppz)(nHo)]+ whensubject to irradiation in the absence and in the presence of DNA suggests adistinctive micro-environment for the investigated complex. The latterobservation might be accounted for the well-known intercalative properties ofdppz ligand. Therefore, the intercalation of [Re(CO)3(dppz)(nHo)]+in the DNAct double-helix would provide a hydrophobic environment tothe complex. In addition, TEA (electrondonor) and MV+2 (electron acceptor) were used as scavengers tofurther ascertain wheter the 3MLCTRe→dppz, 3MLCTRe→nHoand/or 3IL excited states of the intercalated [Re(CO)3(dppz)(nHo)]+ have a role in the photoredox procceses.