Modulation of Energy Transfer into Sequential Electron Transfer upon Axial Coordination of Tetrathiafulvalene in an Aluminum(III) Porphyrin-Free-Base Porphyrin Dyad.
Axially assembled aluminum(III) porphyrin based dyads and triads have been constructed to investigate the factors that govern the energy and electron transfer processes in a perpendicular direction to the porphyrin plane. In the aluminum(III) porphyrin-free-base porphyrin (AlPor-Ph-H2Por) dyad, the AlPor occupies the basal plane, while the free-base porphyrin (H2Por) with electron withdrawing groups resides in the axial position through a benzoate spacer. The NMR, UV-visible absorption, and steady-state fluorescence studies confirm that the coordination of pyridine appended tetrathiafulvalene (TTF) derivative (TTF-py or TTF-Ph-py) to the dyad in noncoordinating solvents afford vertically arranged supramolecular self-assembled triads (TTF-py→AlPor-Ph-H2Por and TTF-Ph-py→AlPor-Ph-H2Por). Time-resolved studies revealed that the AlPor in dyad and triads undergoes photoinduced energy and/or electron transfer processes. Interestingly, the energy and electron donating/accepting nature of AlPor can be modulated by changing the solvent polarity or by stimulating a new competing process using a TTF molecule. In modest polar solvents (dichloromethane and o-dichlorobenzene), excitation of AlPor leads singlet-singlet energy transfer from the excited singlet state of AlPor ((1)AlPor*) to H2Por with a moderate rate constant (k(EnT)) of 1.78 × 10(8) s(-1). In contrast, excitation of AlPor in the triad results in ultrafast electron transfer from TTF to (1)AlPor* with a rate constant (k(ET)) of 8.33 × 10(9)-1.25 × 10(10) s(-1), which outcompetes the energy transfer from (1)AlPor* to H2Por and yields the primary radical pair TTF(+•)-AlPor(-•)-H2Por. A subsequent electron shift to H2Por generates a spatially well-separated TTF(+•)-AlPor-H2Por(-•) radical pair.
Department of Chemistry, University of Prince Edward Island , 550 University Avenue, Charlottetown, PE C1A 4P3, Canada.
Prashanth K
PK
Poddutoori
Department of Chemistry, University of Prince Edward Island , 550 University Avenue, Charlottetown, PE C1A 4P3, Canada.
Lucas P
LP
Bregles
Department of Chemistry, University of North Texas , 1155 Union Circle, #305070, Denton, Texas 76203-5017, United States.
Gary N
GN
Lim
Department of Chemistry, University of Prince Edward Island , 550 University Avenue, Charlottetown, PE C1A 4P3, Canada.
Patricia
P
Boland
Department of Chemistry, University of Prince Edward Island , 550 University Avenue, Charlottetown, PE C1A 4P3, Canada.
Russ G
RG
Kerr
Department of Chemistry, University of North Texas , 1155 Union Circle, #305070, Denton, Texas 76203-5017, United States.
Francis
F
D'Souza
D000535:Aluminum / Q000737:chemistry*; D004579:Electron Transport; D004735:Energy Transfer; D006571:Heterocyclic Compounds / Q000737:chemistry*; D008665:Metalloporphyrins / Q000138:chemical synthesis / Q000737:chemistry*; D015394:Molecular Structure
D006571:Heterocyclic Compounds; D008665:Metalloporphyrins; D000535:Aluminum; C063887:tetrathiafulvalene