Transforming a Fluorochrome to an Efficient Photocatalyst for Oxidative Hydroxylation: A Supramolecular Dimerization Strategy Based on Host‐Enhanced Charge Transfer

Abstract

The development of non‐covalent synthetic strategy to fabricate efficient photocatalysts is of great importance in theranostic and organic materials. Herein, a fluorochrome N,N′‐dimethyl 2,5‐bis(4‐pyridinium)thiazolo[5,4‐d]thiazolediiodide (MPT) was transformed into an efficient photocatalyst through supramolecular dimerization in the cavity of cucurbit[8]uril (CB[8]). The host‐enhanced charge transfer interaction within the supramolecular dimer 2MPT‐CB[8] dramatically promoted intersystem crossing to produce triplet. In addition, the staggered conformation of 2MPT‐CB[8] facilitated the energy transfer and electron transfer of the triplet. As a result, 2MPT‐CB[8] could serve as a high‐efficiency photocatalyst for the oxidative hydroxylation of arylboronic acids. This supramolecular dimerization strategy enriches the supramolecular engineering of functional π‐systems. It is anticipated that this strategy can be extended to fabricate various π‐systems with tailor‐made functions.

Uncommon Supramolecular Phosphorescence‐Capturing Assembly Based on Cucurbit[8]uril‐Mediated Molecular Folding for Near‐Infrared Lysosome Imaging

“…On the basis of charge recombination mechanism, the enhanced ISC efficiency of G could be attributed to CB [8]enhanced charge transfer interaction. [25,51] The UV-vis absorption spectrum of G showed two absorption peaks at around 260 and 340 nm (Figure 1a), respectively ascribed to naphthalene and methoxyphenyl pyridinium (Figure S16, Supporting Information). Then the original absorption peaks of G almost disappeared and a new absorption peak at 367 nm appeared after G binding with CB [8], suggesting the formation of CB [8]mediated ICT assembly.…”

Molecular Engineering of Noncovalent Dimerization

“…If a dimer is sustained with strong restriction, as will be introduced later, its pseudostatic excited state can remain as a dimeric form before relaxation to the ground state. On account of the restriction, the relaxation will mainly choose a radiative pathway of high efficiency, which could lead to dimerization-induced enhanced emission (DIEE) ,− or room-temperature phosphorescence (RTP). , If a dimer is dynamically and loosely held with weak restriction, its excited dimer may have more chances to dissociate into an excited monomer, which then behaves as a supramolecular catalyst to trigger subsequent reactions. , Similar profiles could also be found for the redox products of noncovalent dimers, working either as stable near-infrared (NIR) probes or catalytic supramolecular radicals depending on oxygen content. , …”

“…Zhang et al reported a supramolecular dimerization of two MPT 2+ guests with one CB[8], yielding a 2MPT 2+ -CB­[8] dimer with two guests arranged in a parallel and staggered conformation (Figure ). Owing to their acceptor–donor–acceptor structures, two MPT 2+ guests were coupled with each other as a discrete charge-transfer (CT) pair inside cavity. Upon excitation, the CT interaction was known to promote the intersystem crossing process and generated triplets through a charge separation and recombination mechanism. ,, The supramolecular CT dimer of 2MPT 2+ -CB­[8] thereby behaved as a triplet generator, displaying an increasing yield of triplets upon photoexcitation.…”

“…The release of triplet species is favored by the dynamic nature of this supramolecular dimer loosely restricted by one macrocycle. Adapted with permission from ref . Copyright (2021) Wiley-VCH.…”

Color‐Tunable Supramolecular Luminescent Materials

“…In addition, CB [8] is a relatively large homologue within the CB[n] family. It can bind [76,77] simultaneously two fluorescent molecules inside its cavity as J-aggregates, leading to a red-shifted emission of the guests. Ma and co-workers [78] have synthesized a color-tunable host-guest complex, which is composed of thiazolothiazole methyl viologen (TMV 2+ ) guests and CB [8].…”