An Anthracene‐Appended β‐Cyclodextrin‐Based Dyad: Study of Self‐Assembly and Photoinduced Electron‐Transfer Processes

Abstract

The self-assembly of a beta-cyclodextrin (beta-CD)-based supramolecular dyad is reported, in which the donor anthracene moiety is covalently linked to the smaller rim of the beta-CD and the acceptor pyromellitic diimide (PMDI) is encapsulated within the beta-CD cavity. Encapsulation of the PMDI into the beta-CD cavity was studied by a variety of techniques, which suggested that PMDI is encapsulated so as to position the aromatic part at the centre of the cavity with the 2-propyl end at the narrower rim among the overhanging primary OH groups and the N-ethylpyridinium end situated at the wider rim exposed to water. Photoinduced electron transfer (PET) in the system was studied by fluorescence quenching and laser flash photolysis techniques. At [PMDI]<10(-4) M, the equilibrium is in favour of the free molecules, and under these conditions fluorescence quenching is negligible and diffusion-mediated electron transfer involving the triplet excited state of anthracene predominates. At higher concentrations of PMDI, the equilibrium is largely in favour of the supramolecular dyad and intra-ensemble PET processes predominate. The experimentally determined electron-transfer rate constant agrees very well with that calculated by using the Marcus equation. It was observed that a fraction of the ion pairs survived for more than 200 micros.

Observation of Supramolecular Chirality in a Hierarchically Self‐Assembled Mixed‐Stack Charge‐Transfer Complex

“…Synthesis of compound 2 : PIAD was synthesised by modifying a reported procedure . Pyromellitic dianhydride 1 (6.0 g, 27.5 mmol) was dissolved in dry DMF (60 mL) and 1‐adamantylamine (4.14 g, 27.5 mmol) was added.…”

Phenanthroline bridged bis(β-cyclodextrin)s/adamantane-carboxylic acid supramolecular complex as an efficient fluorescence sensor to Zn2+

“…Due to the supramolecular cooperativity between CD and AdCA, the phenanthroline unit of 1 was forced out of the β-CD cavity to facilitate the multivalent binding of the phenanthroline, triazole, and carboxylic sites with Zn 2+ . 13 Consequently, combining all the characteristic data from NMR and circular dichroism spectroscopy, we can reasonably deduce the possible binding modes of 1/Zn 2+ and 1/AdCA/Zn 2+ , as illustrated in Scheme 2. In addition, the energy minimization structure of the 1/AdCA/ Zn 2+ system was obtained by a molecular modeling study, which is consistent with the proposed recognition mode (Fig.…”

Self-assembly and photoinduced electron transfer in a donor- $$\upbeta $$ β -cyclodextrin-acceptor supramolecular system $$^{\S }$$ §

“…As per the scheme both static and dynamic quenching pathways exist and this leads to the observed bi-exponential decay profiles. 8,30,31,35,61 The bi-exponential profiles were fitted using equation 3 to obtain lifetimes τ 1 and τ 2 and their respective contributions χ 1 and χ 2 .…”

“…Cyclodextrins (CDs), which are cyclic oligosaccharides with hydrophobic cavities, are ideal molecular receptors for building water-soluble supramolecular functional assemblies. [15][16][17][18][19] Recently others [20][21][22][23][24][25][26][27][28][29] and we 30,31 have employed chromophore-appended CDs to assemble supramolecular D-A systems for PET reactions in water. The hydrophobic nature of the CD cavity acts as the assembler of the D-A system here.…”