posted on 2016-01-08, 00:00authored byTing Qi, Hua-Qing Yang, Dennis M. Whitfield, Kui Yu, Chang-Wei Hu
The formation mechanism of CdSe monomers
from the reaction of cadmium
oleate (Cd(OA)2) and SePPh2H in the presence
of HPPh2 and RNH2 was studied systematically
at the M06//B3LYP/6-31++G(d,p),SDD level in 1-octadecene solution.
Herein, SePPh2H, HPPh2, and RNH2 act
as hydrogen/proton donors with a decreased capacity, leading to the
release of oleic acid (RCOOH). The longer the radius of the coordinated
atom is, the larger the size of the cyclic transition state is, which
lowers the activation strain and the Gibbs free energy of activation
for the release of RCOOH. From the resulting RCOOCdSe–PPh2, for the formation of Ph2P–CdSe–PPh2 (G), SePPh2H acts as a catalyst,
in which the turnover frequency determining transition state (TDTS)
is characteristic of the Se–P bond cleavage. For the formation
of RHN–CdSe–PPh2 (H), SePPh2H also serves as a catalyst, in which the TDTS is representative
of the N–H bond cleavage. For the formation of Ph2PSe–CdSe–NHR (I), HPPh2 behaves
as a catalyst, in which the TDTS is typical of the Se–P and
N–H bond cleavage. The rate constants increase as kI < kH < kG, which is
in good agreement with our previous experimental observations reported.
The present study brings insight into the use of additives such as
HPPh2 and RNH2 to synthesize colloidal quantum
dots.