Thousand-Fold Enhancement of Charge-Separated State Lifetimes Caused by an Adamantane Bridge in Dimethylaniline-Anthracene and Dimethylaniline-Pyrene Dyads.

A long-standing challenge in photoinduced electron transfer research is the design of compact donor-acceptor dyads that can generate long-lived charge-separated (CS) states for use as sensitizers in solar energy harvesting. Reports of dyads exhibiting CS state lifetimes in the microsecond time domain are very rare. Herein, we report two compact donor-bridge-acceptor dyads exhibiting lifetimes in the microsecond domain.

Self-Assembly and Photochemistry of a Pyrene-Methyl Viologen Supramolecular Fiber System.

This paper reports the self-assembly of a donor-acceptor system into nanoscopic structures and the photo processes taking place within these structures. The donor employed is pyrene linked to two β-cyclodextrin molecules (CD-PY-CD), and adamantane-linked methyl viologen attached to the three arms of mesitylene (Ms-(MV-AD)) is the acceptor. CD-PY-CD and Ms-(MV-AD) when dissolved in water self-assembled into vesicles, which joined together to give long fibers.

Photoinduced Electron Transfer in a Self-Assembled Bis(β-cyclodextrin)-Linked Pyrene/Bis(adamantane)-Linked Methyl Viologen Donor-Acceptor System in Aqueous Solution.

Pyrene linked to two β-CD (CD = cyclodextrin; PY = pyrene) molecules (CD-PY-CD) and methylviologen (MV) linked to two adamantane (AD) groups (AD-MV-AD) self-assembled in water to give toroidal nanostructures. Photoprocesses taking place in the femtosecond and nanosecond time ranges within the assembly are reported. Fluorescence of the pyrene chromophore was quenched in the toroid, suggesting very efficient electron transfer.

Generation of Long-Lived Photoinduced Charge Separation in a Supramolecular Toroidal Assembly.

Efficiencies of artificial photosynthetic and photocatalytic systems depend on their ability to generate long-lived charge-separated (CS) states in photoinduced electron transfer (PET) reactions. PET, in most cases, is followed by an ultrafast back electron transfer, which severely reduces lifetime and quantum yield of CS states. Generation of a long-lived CS state is an important goal in the study of PET reactions.

Self-Assembly of a β-Cyclodextrin Bis-Inclusion Complex into a Highly Crystalline Fiber Network. An Effective Strategy for Null Aggregate Design.

The present work deals with the tight molecular packing of a bis-inclusion complex into rigid, 1D nanofibers. The bis-adamantane (AD) linked anthracene derivative AD-AN-AD readily formed the β-CD bis-inclusion complex, β-CD⊂AD-AN-AD⊃β-CD, which spontaneously assembled into a nanofiber network. The wide angle X-ray scattering pattern of the dried nanofibers indicated that these are highly crystalline in nature.