PH indicator and rotary fluorescent properties of the Sn(IV)-octaetylporphyrin-(BODIPY)2 triad

Abstract

A triad of two 1,3,5,7-tetramethyl-8-(4-hydroxyphenyl)BODIPY ligands (BODIPY) axially linked to Sn(IV)-octaethylporphyrin [Sn(BODIPY)2OEtP] is synthesized. The structure of the triad is optimized by quantum chemical calculations and confirmed by a combination of physicochemical methods. The spectral luminescent properties of the triad and its components in DMF solution are studied. Using a model system of the DMF-glycerol binary solvent, the sensitivity of the photophysical characteristics of the triad to the concentration-dependent viscosity of the solution, as well as to the addition of acids and alkalis, is studied. Sn(BODIPY)2OEtP photoexcitation leading to photoinduced energy transfer from donor fragments of BODIPY to the porphyrinate acceptor is observed. As a result, upon excitation of the triad at λex = 490 nm both BODIPY fluorescence and porphyrin fluorescence are recorded. When the triad is excited at λex = 400 nm, the fluorescence of the porphyrin increases compared to the initial Sn(IV)-octaethylpophyrin. This energy transfer, which depends on both the mobility of the medium and its acidity, provides the Sn(BODIPY)2OEtPtriad with the properties of a molecular rotor, a pH indicator and very high photostability (resistance to photobleaching), as well as antibacterial activity against the Staphylococcusaureus ATCC strain.