Affiliation:
1. State Key Laboratory of Fine Chemicals, Frontiers Science Center for Smart Materials Oriented Chemical Engineering, School of Chemical Engineering, Dalian University of Technology, E-208 West Campus, 2 Ling Gong Rd., Dalian 116024, China
Abstract
We prepared a rhodamine (RB)–perylene (Pery) compact electron donor/acceptor dyad (RB–Pery) to study the spin-orbit charge-transfer intersystem crossing (SOCT–ISC). The UV–vis absorption spectrum indicates a negligible electronic interaction between the donor and acceptor at ground state. However, the fluorescence of both the RB and Pery units are quenched in the dyad, which is attributed to the photoinduced electron transfer, supported by the electrochemical studies. Nanosecond transient absorption (ns-TA) spectra show delocalized triplet states, i.e., there is an excited-state equilibrium between Pery and the RB triplet states. The triplet state lifetime was determined as 109.8 μs. With intermolecular triplet–triplet energy transfer, monitored using ns-TA spectra, the triplet-state energy balance between RB and Pery in RB–Pery was confirmed. The proposed cascade photophysical processes of the dyad are 1RB*-Pery→RB–Pery+•→[3RB*-Pery↔RB-3Pery*]. Moreover, long-lived rhodamine radical cation (in milliseconds) was detected in both deaerated/aerated non-polar or low-polarity solvents (i.e., p-xylene, toluene). The potential energy curve of the dyad against the variation in the dihedral angle between the two units indicates large torsional freedom (53°~128°) in RB–Pery, which leads to inefficient SOCT–ISC; consequently, low singlet-oxygen quantum yields (ΦΔ = 2~8%) were observed.
Funder
Ministry of Science and Technology
NSFC
Research and Innovation Team Project of the Dalian University of Technology
Fundamental Research Funds for the Central Universities
State Key Laboratory of Fine Chemicals
Subject
General Earth and Planetary Sciences,General Environmental Science