The ability of quantum dots (QDs) to photocatalyze organic
reactions
is gaining attention because of their distinct light harvesting properties
over traditional precious metal- and small molecule-based catalysts.
However, establishing the potency of QD photocatalysts in diverse
and useful organic transformations, as well as deciphering the charge
transfer mechanism, is essential to cement their place as an efficient
photocatalyst in synthetic chemistry. Here, we report the use of QDs
in efficiently catalyzing a series of olefination reactions under
visible-light irradiation at room temperature (90% yield). Spectroscopic
and electrochemical studies reveal intriguing insights on the charge
transfer mechanism involved in QD-photocatalyzed olefination. Interestingly,
the dual role of triphenylphosphineas a surface passivating
agent and nucleophileturned out to be decisive in directing
the charge transfer process from the QD to the reactant. Benzyl triphenylphosphonium
bromide salt was accepting the electrons from the photoexcited QDs,
thereby initiating the catalytic olefination reaction. QD-photocatalyzed
olefination was demonstrated with formaldehyde as well, resulting
in the formation of industrially relevant terminal alkene, namely
styrene. Moreover, the environmentally friendly indium phosphide (InP)
QD also photocatalyzed the olefination reaction under mild reaction
conditions, which proves the practical suitability of our study. This
work presents an attractive and efficient way to introduce double
bonds in organic molecules using QDs and visible light at room temperature.