1,7-Di-tert-butyl-Substituted aza-BODIPYs by Low-Barrier Rotation to Enhance a Photothermal-Photodynamic Effect

1,7-Di-tert-butyl-substituted aza-BODIPYs (tBu-azaBDP) were successfully obtained for the first time. The structures of tBu-azaBDP and Ph-azaBDP were confirmed by X-ray crystal analysis, and tBu-azaBDP 2 is more twisted than Ph-azaBDP 5. tBu-azaBDPs have significant photo-stability and enhanced water solubility. tBu-azaBDPs possess excellent optical properties, such as high molar extinction coefficients, broad full width half maxima, and large Stokes shifts, which is comparable to those of the parent dye Ph-azaBDP. Although the low-barrier rotation of the distal -tBu groups in tBu-azaBDPs results in low quantum yield, photothermal conversion efficiency and singlet oxygen generation ability of tBu-azaBDPs are more effective than those of Ph-azaBDP, which is highly desirable for a photothermal-photodynamic therapy agent.

Effect of thiophene substitution on the intersystem crossing of arene photosensitizers

Thiophene substitution gives energy level-matched S₁/T₂ states and the ISC is enhanced, which was not observed with phenyl substitution.

A combined theoretical and experimental investigation on the influence of the bromine substitution pattern on the photophysics of conjugated organic chromophores

Two-photon photosensitizers with heavy atom substituents were synthesized and evaluated through a combined photophysical and computational study.

Synthesis and Properties of Covalently Linked AzaBODIPY-BODIPY Dyads and AzaBODIPY-(BODIPY)2 Triads

The azaBODIPYs containing one and two formyl functional groups on the 1,7-aryl groups present at the azaBODIPY core were synthesized over sequence of steps and characterized by mass, NMR, absorption, and electrochemical techniques. The monoformylated and diformylated azaBODIPYs are very useful synthons to prepare a wide variety of new fluorescent compounds. The mono- and diformylated azaBODIPYs were treated with pyrrole under mild acidic conditions followed by column chromatographic purification to afford azaBODIPYs appended with one and two dipyrromethanyl groups. The dipyrramethanyl groups of azaBODIPYs were oxidized with DDQ and complexed with BF₃·Et₂O to obtain covalently linked azaBODIPY-BODIPY dyads and azaBODIPY-(BODIPY)₂ triads. The dyads and triads were characterized in detail by HR-MS, 1D and 2D NMR, absorption, fluorescence, and electrochemical techniques and the structure of one of the triads was deduced by X-ray crystallography. The crystal structure of azaBODIPY-(BODIPY)₂ triad revealed that the two BODIPY units were in perpendicular orientation with azaBODIPY unit. The absorption and electrochemical studies indicated a weak interaction among the BODIPY and azaBODIPY moieties and the moieties retain their independent characteristic features in dyads and triads. The preliminary fluorescence studies supported an efficient energy transfer from BODIPY unit(s) to azaBODIPY unit in dyads and triads.