A Boron Difluoride Hydrazone (BODIHY) Polymer Exhibits Aggregation‐Induced Emission

Abstract

Polymers that exhibit aggregation‐induced emission (AIE) find use, for example, as cell‐imaging agents and as fluorometric sensors due to their unique optical properties. However, the structural diversity of AIE‐active polymers has not necessarily advanced at the same rate as their applications. In this work, ring‐opening metathesis polymerization is used to synthesize the first example of a polymer (Mn = 61,600 g mol−1, Đ = 1.32) containing boron difluoride hydrazone (BODIHY) heterocycles in its repeating unit. The BODIHY monomer and polymer described absorb and emit in the visible region in solution (λabs = 428 and 429 nm, λem = 528 and 526 nm) and as thin films (λabs = 443 and 440 nm, λem = 535 and 534 nm). Monomer (ΦFilm = 10%) and polymer (ΦFilm = 6%) exhibit enhanced emission as thin films compared to solution (ΦSoln ≤ 1%) as well as AIE upon the addition of water to DMF solutions as a result of restriction of intramolecular motion. Enhancement factors for the monomer and polymer are determined to be 58 and 15, respectively. The title BODIHY polymer exhibited an earlier onset of AIE and enhanced sensitivity to solution viscosity when compared to the parent monomer.

Boron difluoride hydrazone (BODIHY) complexes: A new class of fluorescent molecular rotors

“…Republished with permission of John Wiley and Sons—Books, from Ref. 57, copyright year 2021; permission conveyed through Copyright Clearance Center, Inc.…”

“…Cappello and coworkers have also employed ringopening metathesis polymerization (ROMP) to introduce BODIHY units as pendants in AIE-active polymers. [57] Monomer 23 (Figure 8A) was synthesized in 78% yield through conventional methods. [32,37] ROMP, catalyzed with 1 mol% of a derivatized Grubbs' third-generation catalyst, was used to synthesize BODIHY polymer 24.…”

Controlling Molecular Aggregation-Induced Emission by Controlled Polymerization

“…In addition, ROMP is another type of controlled polymerization based on olefin metathesis [ 35 ]. It has also demonstrated great ability in the synthesis of well-defined fluorescent polymers [ 49 ], including AIE polymers [ 100 , 101 , 102 , 103 , 104 ] and ladderphanes [ 105 ]. Although ROMP-based single-fluorophore AIE polymers have not been reported so far, end-group functionalization may provide an approximate method for this [ 106 , 107 ] if the incorporation of AIE fluorophores can be precisely controlled with high conversion rates.…”

Tuning the Properties of Donor–Acceptor and Acceptor–Donor–Acceptor Boron Difluoride Hydrazones via Extended π-Conjugation

“…BODIHYs ( e.g. , 5 ) are BF 2 -containing heterocycles based on chelating pyridylhydrazone ligands, and these materials exhibit aggregation-induced emission and interesting redox chemistry. − We recently developed triphenylamine–BODIHY conjugates ( e.g. , 6 ) that exhibit dual emission, AIE, multiple redox waves, and charge-transfer characteristics .…”