Long-Lived Charge-Transfer State from B–N Frustrated Lewis Pairs Enchained in Supramolecular Copolymers

Abstract

The field of supramolecular polymers is rapidly expanding; however, the exploitation of these systems as functional materials is still elusive. To become competitive, supramolecular polymers must display microstructural order and the emergence of new properties upon copolymerization. To tackle this, a greater understanding of the relationship between monomers’ design and polymer microstructure is required as well as a set of functional monomers that efficiently interact with one another to synergistically generate new properties upon copolymerization. Here, we present the first implementation of frustrated Lewis pairs into supramolecular copolymers. Two supramolecular copolymers based on π-conjugated O -bridged triphenylborane and two different triphenylamines display the formation of B–N pairs within the supramolecular chain. The remarkably long lifetime and the circularly polarized nature of the resulting photoluminescence emission highlight the possibility to obtain an intermolecular B–N charge transfer. These results are proposed to be the consequences of the enchainment of B–N frustrated Lewis pairs within 1D supramolecular aggregates. Although it is challenging to obtain a precise molecular picture of the copolymer microstructure, the formation of random blocklike copolymers could be deduced from a combination of optical spectroscopic techniques and theoretical simulation.

Living supramolecular polymerization of fluorinated cyclohexanes

“…While there has been remarkable progress recently with preparing supramolecular block copolymers under thermodynamic control [60][61][62] or by slow cooling of monomer mixtures [63][64][65] , a growing number of such precision polymers has been prepared by LSP, which can provide superior structural and sequence control. However to date, these LSP approaches either rely on the modification of the polymerizable core, e.g., substituents are attached to the core of rylene dyes 16,66 or the complexation of different metal ions to identical ligands 67,68 .…”

Face‐to‐Face Orientation of Quasiplanar Donor and Acceptor Enables Highly Efficient Intramolecular Exciplex Fluorescence

“…[11] Further, DPXZ-BO was designed by replacing TRZ with a rigid O-bridged triphenylborane (BO) which has an ideal matching shape with the DPXZ donor and may incur charge transfer within the intramolecular FLP. [12] A control compound CTZ was designed for comparative study. Their syntheses are provided in the Supporting Information.…”

Supramolecular Systems Containing B–N Frustrated Lewis Pairs of Tris(pentafluorophenyl)borane and Triphenylamine Derivatives

“…Decreasing the temperature quenches and red-shifts the emission of both TPA derivatives, which could be caused by polymerization and/or charge transfer to TFPB (Figures 2c, S10 and S11, blue lines). 19,24 This trend is accompanied by the growth of the charge transfer emission, where the red-shift is an indication of a shorter distance between B and N components in the mixed systems. 34,36 Both amide-based TPA derivatives form stable gels in decalin (20 mM for TPA-amide and 2 mM for TPA-amide9) and emit purple/blue light when excited with light of λ ex ¼ 365 nm.…”

“…The emission band at 502 nm can arise from a charge transfer excited state of a B-N complex. 15,19 This emission wavelength is an indicator of the energy of the charge transfer interaction and can be correlated to the energetic difference between the donor's HOMO and the acceptor's LUMO. The broadening and disappearance of peaks located in the aromatic regions of 1 H and 13 C NMR spectra of this B-N mixture in deuterated chloroform further support the complexation between TPA-alkyne and TFPB (Figure S4).…”

“…This was most likely caused by strong competition between the noncovalent forces to form a polymer and the B-N interactions. 19 Thus, designing a stronger B-N pair will be highly beneficial to increase the degree of B-N mixing, hereby enhancing the effect of B-N interaction. Taking inspiration from the classic triphenylborane-triphenylamine FLP, we wonder whether a more simple B-N dimer can be extended into a one-dimensional (1D) array, with the aim to achieve long-range ordering for optoelectronic applications.…”