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Distance-Dependent Electron Transfer Kinetics in Axially Connected Silicon Phthalocyanine-Fullerene Conjugates |
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| Authors: | Dr Luis Martín-Gomis Sairaman Seetharaman David Herrero Prof Dr Paul A Karr Prof Dr Fernando Fernández-Lázaro Prof Dr Francis D'Souza Prof Dr Ángela Sastre-Santos |
| Institution: | 1. División de Química Orgánica, Instituto de Bioingeniería, Universidad Miguel Hernández, Avda. de la Universidad s/n, 03203 Elche, Spain;2. Department of Chemistry, University of North Texas at Denton, 1155 Union Circle, #305070, Denton, TX 76203-5017 USA
These authors contributed equally to this work.;3. División de Química Orgánica, Instituto de Bioingeniería, Universidad Miguel Hernández, Avda. de la Universidad s/n, 03203 Elche, Spain These authors contributed equally to this work.;4. Department of Physical Sciences and Mathematics, Wayne State College, 1111 Main Street, Wayne, Nebraska 68787 USA;5. Department of Chemistry, University of North Texas at Denton, 1155 Union Circle, #305070, Denton, TX 76203-5017 USA |
| Abstract: | The effect of donor-acceptor distance in controlling the rate of electron transfer in axially linked silicon phthalocyanine-C60 dyads has been investigated. For this, two C60-SiPc-C60 dyads, 1 and 2 , varying in their donor-acceptor distance, have been newly synthesized and characterized. In the case of C60-SiPc-C60 1 where the SiPc and C60 are separated by a phenyl spacer, faster electron transfer was observed with kcs equal to 2.7×109 s−1 in benzonitrile. However, in the case of C60-SiPc-C60 2 , where SiPc and C60 are separated by a biphenyl spacer, a slower electron transfer rate constant, kcs=9.1×108 s−1, was recorded. The addition of an extra phenyl spacer in 2 increased the donor-acceptor distance by ∼4.3 Å, and consequently, slowed down the electron transfer rate constant by a factor of ∼3.7. The charge separated state lasted over 3 ns, monitoring time window of our femtosecond transient spectrometer. Complimentary nanosecond transient absorption studies revealed formation of 3SiPc* as the end product and suggested the final lifetime of the charge separated state to be in the 3–20 ns range. Energy level diagrams established to comprehend these mechanistic details indicated that the comparatively high-energy SiPc.+-C60.− charge separated states (1.57 eV) populated the low-lying 3SiPc* (1.26 eV) prior returning to the ground state. |
| Keywords: | axial binding motif energy transfer fullerene photoinduced charge separation phthalocyanines |