Publication

Real-time observation of intersystem crossing induced by charge recombination during bimolecular electron transfer reactions

Real-time observation of intersystem crossing induced by charge recombination during bimolecular electron transfer reactions
Amani A. Alsam, Shawkat M. Aly, Manas R. Parida, Erkki Alarousu, Zhen Cao, Luigi Cavallo, and Omar F. Mohammed
Dyes and Pigments, 2017, Vol. 136, pages 881-886
Amani A. Alsam, Shawkat M. Aly, Manas R. Parida, Erkki Alarousu, Zhen Cao, Luigi Cavallo, Omar F. Mohammed
Bimolecular electron transfer; Charge recombination; Intersystem crossing; Triplet state; Pump-probe experiments
2017

 

 

 

Real-time probing of intersystem crossing (ISC) and triplet-state formation after photoinduced electron transfer (ET) is a particularly challenging task that can be achieved by time-resolved spectroscopy with broadband capability. Here, we examine the mechanism of charge separation (CS), charge recombination (CR) and ISC of bimolecular photoinduced electron transfer (PET) between poly[(9,9-di(3,3'-N,N’-trimethyl-ammonium) propyl fluorenyl-2,7-diyl)-alt-co-(9,9-dioctyl-fluorenyl-2,7-diyl)] diiodide salt (PFN) and dicyanobenzene (DCB) using time-resolved spectroscopy. PET from PFN to DCB is confirmed by monitoring the transient absorption (TA) and infrared spectroscopic signatures for the radical ion pair (DCB-•-PFN+•). In addition, our time-resolved results clearly demonstrate that CS takes place within picoseconds followed by CR within nanoseconds. The ns-TA data exhibit the clear spectroscopic signature of PFN triplet-triplet absorption, induced by the CR of the radical ion pairs (DCB-•-PFN+•). As a result, the triplet state of PFN (3PFN*) forms and subsequently, the ground singlet state is replenished within microseconds.

DOI: 10.1016/j.dyepig.2016.09.049