Fluorescence emission and enhanced photochemical stability of Zn(II)-5-triethyl ammonium methyl salicylidene ortho-phenylendiiminate interacting with native DNA.
The photophysical and photochemical properties of the cationic Zn(II) complex of 5-triethyl ammonium methyl salicylidene ortho-phenylendiimine (ZnL(2+)) interacting with native DNA were investigated by steady state and time-resolved fluorescence spectroscopies. Experimental results indicate that, in the presence of DNA, ZnL(2+) is efficiently protected from a photochemical process, which occurs when it is in the free state dispersed in aqueous solution. The analysis of the absorption and emission spectra of ZnL(2+), both stored in the dark and after exposure to tungsten lamp light for 24 h, corroborated by quantum chemical calculations, allowed us to point out that ZnL(2+) undergoes a photoinduced two-electron oxidation process. According to this picture, the protective action of DNA toward the intercalated ZnL(2+) was attributed to an effective inhibition of the ZnL(2+) photooxidation. In this context, it can be considered that DNA-intercalated ZnL(2+) is located in a region more hydrophobic than that sensed in the bulk water solvent. Moreover, by a thorough analysis of steady state and time-resolved fluorescence spectra, the interaction process can be consistently explained in terms of a complete intercalation of the complex molecules and that the polarity of the environment sensed by intercalated ZnL(2+) is comprised between that of methanol and ethanol.
Barone
Giampaolo
G
Dipartimento di Chimica Inorganica e Analitica S. Cannizzaro, Università di Palermo, Viale delle Scienze, Parco d'Orleans II, Edificio 17, 90128, Palermo, Italy. gbarone@unipa.it
Ruggirello
Angela
A
Silvestri
Arturo
A
Terenzi
Alessio
A
Liveri
Vincenzo Turco
VT
D004247:DNA / Q000378:metabolism; D005453:Fluorescence; D007364:Intercalating Agents / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D012997:Solvents; D013057:Spectrum Analysis; D015032:Zinc / Q000737:chemistry*
D007364:Intercalating Agents; D009942:Organometallic Compounds; D012997:Solvents; D004247:DNA; D015032:Zinc