S2 emission from chemically modified BODIPYs.

Novel boron dipyrromethene (BODIPY) derivatives having significant absorption and emission in the longer wavelength region were synthesized. BODIPY showed anomalous S(2) emission from the second excited (S(2)) state at shorter wavelength. The photodynamics of the S(2) state was investigated by fluorescence up-conversion and transient absorption spectroscopic measurements. The decay time of the S(2) emission was dependent on the internal conversion and the intersystem crossing process. The assignments of transitions were supported by a theoretical calculation based on the time-dependent density functional theory. This journal is © The Royal Society of Chemistry 2012