Photochemical properties of hepta-coordinated tin(IV) complexes

ELBA N. RUIZ PEREYRA,; WALTER J. PELÁEZ; GUILLERMO M. CHANS; CECILIO ÁLVAREZ TOLEDANO; ELIZABETH GÓMEZ; GUSTAVO A. ARGÜELLO

Encuentro; XIII Encuentro Latinoamericano de Fotoquímica y Fotobiología (ELAFOT); 2017

Organotin(IV) complexes have gained recognition because of their remarkable biological applications; their industrial potential, and the ability of tin to form stable bonds both with carbon as well as with heteroatoms. As one of the representative organotin(IV) compounds, carboxylates have called attention in the last few decades due to their broad use as catalysts, stabilizers, antimicrobial,[1] anti-inflammatory,[2] antifungal,[1] and antituberculosis agents. Having synthesized since a couple of years, some nobel hepta-coordinated complexes, in this work we present the first study about their photochemical properties. Our goal was to characterize their behavior when a 254 nm photon is absorbed. The different paths that the excited state will follow, was probed under different conditions (solvents, presence or absence of molecular oxygen, temperature, etc.). We recorded UV-Vis as well as fluorescence emission spectra (figure 2 a and b) that were further analyzed. Though the complexes studied show all considerable molar absorptivity coefficients (, figure 2a) in acetonitrile (ACN), our results show that, the fluorescence quantum yields (calculated relative to the reference tris-(bipyridine)-ruthenium(II) chloride) ranged between 0.1 to 2.3 10-2. Other processes, like photo-degradation, are occurring. We measured the rate constant coefficients for the disappearance under different temperatures and solvents. In all cases the processes are first order and independent of temperature. Furthermore, the rate coefficients were compared in the presence as well as in the absence of O2, to discern whether an intersystem crossing to the triplet state is operative (see table 1). As it is well known, O2 can act as an efficient quencher in photodegradation reactions. Nevetheless, no quenching was observedfor these tin compounds. Finally, all photoproducts were identified unequivocally through NMR and CG-MS analysis