Supramolecular donor–acceptor hybrids of porphyrins/phthalocyanines with fullerenes/carbon nanotubes: electron transfer, sensing, switching, and catalytic applications

Abstract

Since the three-dimensional electron-accepting fullerene has been found to be an excellent building block for self-assembled supramolecular systems, we have investigated photoinduced electron transfer processes in supramolecular fullerene systems with porphyrins and phthalocyanines as electron donors to mimic natural photosynthesis. We have successfully formed self-assembled supramolecular dyads and triads via metal-ligand coordination, crown-ether inclusion, ion pairing, hydrogen-bonding, or pi-pi stacking interactions. Although the single mode of binding gives usually flexible supramolecular structures, the newly developed strategy of multiple modes of binding results in conjugates of defined distance and orientation between the donor and acceptor entities, which influences the overall electron transfer reactions. In these conjugates, we observe the anticipated acceleration of the charge separation process and deceleration of the charge recombination process. Applications of these supramolecular systems for reversible photoswitching of inter- and intramolecular electron transfer events open up new opportunities in the area of photosensors. Extension of the self-assembly approaches to single wall carbon nanotubes (SWNT) results in SWNT-porphyrin/phthalocyanine nanohybrids capable of undergoing photoinduced electron transfer. These photochemical processes lead to photocatalytic reactions accumulating redox active substances of electron acceptor/mediator entities with the help of a sacrificial electron donor. Studies on these self-assembled supramolecular dyads, triads, tetrads, etc., are only in the beginning stages and future studies anticipate involvement of more complex systems targeted for better performances in light-driven devices.

Isotopic effect and temperature dependent intramolecular excitation energy transfer in a model donor–acceptor dyad

“…For example, deuteration dramatically increases the triplet lifetime of various deuteronapthalene systems as observed in ESR experiments by Hutchenson 33 . Similar effects have been reported for the 3 B 1u → 1 A 1g triplet to singlet conversion in benzene and benzene-d 6 with k (H) /k (D) ranging between 2 and 4 34 . For example, in Ar matrix at 4K, k (H) /k (D) = 5.9 31,35 while in EPA glass at 77K k (H) /k (D) = 1.7 34 .…”

“…Other theoretical work using saddle point methods to numerically evaluate the rate constant in the statistical limit give ratios of k (H) /k (D) = 24 36 to k (H) /k (D) = 1.1 × 10 4 and 2.2 × 10 2 depending upon the parameters for the e 2g mode 37 . Finally, recent work by Zamstein using an ab initio parameterization and a phase-space approach for the non-radiative 3 B 1u → 1 A 1g triplet to singlet conversion in benzene and benzene-d 6 gives a k (H) /k (D) = 3.7 − 7.8 38 .…”

“…In this study, we focus on supramolecular donor-acceptor (D-A) unit 6 , which is made up of a donor molecule "LPPP5" (Ladder-type poly-(para-phenylene)) and an acceptor molecule "PDI" (perylenediimide) linked by a single covalent bond. The chemical structure of the D-A unit are shown in Fig.…”

Formation of a long-lived electron-transfer state in mesoporous silica-alumina composites enhances photocatalytic oxygenation reactivity

“…copper complex catalyst | donor-acceptor dyad | nanosized silica-alumina | p-xylene | photoinduced electron transfer E xtensive efforts have been devoted to develop a variety of electron donor-acceptor linked molecules, which mimic charge-separation processes in the photosynthetic reaction center (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11); however, long-lived charge separation has been attained only in frozen media at low temperature (12)(13)(14)(15)(16)(17)(18) because intermolecular back electron transfer in solution is predominant as compared to the corresponding intramolecular process. For example, photoexcitation of a charge-shift type donor-acceptor dyad, 9-mesityl-10-methylacridinium ion (Acr þ -Mes) affords the electron-transfer (ET) state (Acr • -Mes •þ ) with an extremely long lifetime (e.g., 2 h at 203 K) in frozen media (18,19).…”

Photoinduced Electron Transfer of SWCNT-Based Supramolecular Nanoarchitectures with Photosensitizing Molecules

“…Usage of pigment-connected molecules can avoid direct interaction, preserving the direct -electronic structures of individual components. The electron aromatic compounds, to which the desired grips are appended, can be employed as adsorbent on the SWCNTs surface via  stacking [1][2][3]. These three-component architectures are found to be a highly viable and versatile approach.…”