Proton-Dependent Switching of a Novel Amino Chlorin Derivative as a Fluorescent Probe and Photosensitizer for Acidic Media

HEREDIA, DANIEL A.; GSPONER, NATALIA S.; MILANESIO, MARÍA E.; DURANTINI, ANDRÉS M.; FERREYRA, DARÍO D.; DURANTINI, EDGARDO N.; SAROTTI, ARIEL M.; BERTOLOTTI, SONIA G.

CHEMISTRY-A EUROPEAN JOURNAL

WILEY-V C H VERLAG GMBH

Año: 2018 vol. 24 p. 5950 - 5961

0947-6539

A novel chlorin derivative (TPCF20-NMe2) has been synthesized as a syn adduct of a pyrrolidine-fused chlorin bearing a C-linked N,N-dimethylaminophenyl residue. Theabsorption spectrum of TPCF20-NMe2 is essentially identical to that of TPCF20 in N,N-dimethylformamide, indicating a very weak interaction between the chlorin macrocycle and the amine group in the ground state. However, the fluorescence emission of the chlorin moiety in TPCF20-NMe2 is effectively quenched by the attached amine unit. Moreover, TPCF20-NMe2 is unable to attain a triplet excited state or to photosensitize singlet molecular oxygen. Spectroscopic and redox properties indicate that intramolecular photoinduced electron transfer can take place from the N,N-dimethylaminophenyl group to the chlorin macrocycle. Thus, in an acid medium, protonation of the amino group leads to a considerable increase in the fluorescence emission, triplet excitedstate formation, and singlet molecular oxygen production. Photodynamic inactivation of Escherichia coli sensitized by TPCF20-NMe2 is negligible at neutral pH. However, this chlorin becomes highly effective innactivating E. coli cells under acidic conditions. Therefore, these results indicate that TPCF20-NMe2 is an interesting molecular structure, in which protonation of the amino group can be used as an off/on molecular switch activating red fluorescence emission and photodynamic activity capable of eradicating bacteria.