| Autor: |
Yadagiri B; Department of Polymers and Functional Materials, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500007, India.; Academy of Scientific and Innovative Research, CSIR-IICT, Tarnaka, Hyderabad 500007, India., Kaswan RR; Department of Chemistry, University of North Texas, 1155 Union Circle, #305070, Denton, Texas 76203-5017, United States., Tagare J; Department of Polymers and Functional Materials, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500007, India., Kumar V; Department of Polymers and Functional Materials, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500007, India.; Academy of Scientific and Innovative Research, CSIR-IICT, Tarnaka, Hyderabad 500007, India., Rajesh MN; Department of Polymers and Functional Materials, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500007, India.; Academy of Scientific and Innovative Research, CSIR-IICT, Tarnaka, Hyderabad 500007, India., Singh SP; Department of Polymers and Functional Materials, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500007, India.; Academy of Scientific and Innovative Research, CSIR-IICT, Tarnaka, Hyderabad 500007, India., Karr PA; Department of Physical Sciences and Mathematics, Wayne State College, 111 Main Street, Wayne, Nebraska 68787, United States., D'Souza F; Department of Chemistry, University of North Texas, 1155 Union Circle, #305070, Denton, Texas 76203-5017, United States., Giribabu L; Department of Polymers and Functional Materials, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500007, India.; Academy of Scientific and Innovative Research, CSIR-IICT, Tarnaka, Hyderabad 500007, India. |
| Abstrakt: |
We have designed, synthesized, and characterized a donor-acceptor triad, SPS-PPY-C 60 , that consists of a π-interacting phenothiazine-linked porphyrin as a donor and sensitizer and fullerene as an acceptor to seek charge separation upon photoexcitation. The optical absorption spectrum revealed red-shifted Soret and Q-bands of porphyrin due to charge transfer-type interactions involving the two ethynyl bridges carrying electron-rich and electron-poor substituents. The redox properties suggested that the phenothiazine-porphyrin part of the molecule is easier to oxidize and the fullerene part is easier to reduce. DFT calculations supported the redox properties wherein the electron density of the highest molecular orbital (HOMO) was distributed over the donor phenothiazine-porphyrin entity while the lowest unoccupied molecular orbital (LUMO) was distributed over the fullerene acceptor. TD-DFT studies suggested the involvement of both the S 2 and S 1 states in the charge transfer process. The steady-state emission spectrum, when excited either at porphyrin Soret or visible band absorption maxima, revealed quenched emission both in nonpolar and polar solvents, suggesting the occurrence of excited state events. Finally, femtosecond transient absorption spectral studies were performed to witness the charge separation by utilizing solvents of different polarities. The transient data was further analyzed by GloTarAn by fitting the data with appropriate models to describe photochemical events. From this, the average lifetime of the charge-separated state calculated was found to be 169 ps in benzonitrile, 319 ps in dichlorobenzene, 1.7 ns in toluene for Soret band excitation, and ∼320 ps for Q-band excitation in benzonitrile. |
