Twisting and piezochromism of phenylene-ethynylenes with aromatic interactions between side chains and main chains

Abstract

This paper describes a series of three-ring phenylene-ethynylenes (PEs) in which specific, non-covalent arene-arene interactions control conformation in the solid-state. As determined by single crystal X-ray structures, edge-face interactions between benzyl ester side chains and conjugated main chains are observed. In contrast, perfluorobenzyl ester side chains interact cofacially with main chains, resulting in $60 torsional angles between neighboring aryl rings in crystalline PEs. Absorbance and fluorescence spectra of films of these compounds reflect these conformational effects, with the spectra of perfluorobenzyl-substituted compounds shifting hypsochromically from solution-to solid-state. In a demonstration of how balancing non-covalent interactions can open the way to new responsive materials, a main chain twisted derivative with octyloxy substituents displayed significant piezochromic behavior.

Small Changes With Big Consequences: Swapping Two Atoms In Side Chains Changes Phenylene‐Ethynylene Packing And Fluorescence

“…Moreover, emission spectra of these regioisomers shift in opposite directions upon application of force . Similar to other twisted PEs we reported, fluorescence of 2 , 4 , 6‐OMe thin films (Figure ) shifts bathochromically from 454 to 486 nm upon applying shear force manually with a spatula. This shift reverses with thermal annealing, and is consistent over multiple cycles (Figures S4–S6, Supporting Information).…”

Reversible fluorescence switching and topochemical conversion in an organic AEE material: polymorphism, defection and nanofabrication mediated fluorescence tuning

“…2c, S7). [38][39][40][41][42][43][44][45] PXRD studies also confirm the amorphous phase for grounded DPAMBM powder (Fig. 2d, S8).…”

“…In both crystals, the phenyl groups of triphenyl amine 80 adopted different orientation (Fig. [38][39][40][41][42] Interestingly, heating/solvent 40 exposure of strongly grounded DPAMBM-1 powder further blue shifted the fluorescence that matches with DPAMBM-2 (λ max = 545 nm, Fig. The acceptor malononitrile (A) and donor aminophenyl (D) adopted nearly a linear conformation (dihedral angle = 1.0°) and the other two phenyl groups are nearly eclipsed with each other in DPAMBM-2 (Fig.…”

“…[30][31][32][33] External stimuli such as heat, mechanical force and solvent exposure often changes the molecular conformation or phase of the materials (crystalline to amorphous) and switches the fluorescence. [38][39][40][41][42][43][44][45] For example, conformationally twisted cyanostilbene based AEE materials showed dramatic fluorescence switching with external force. [38][39][40][41][42][43][44][45] For example, conformationally twisted cyanostilbene based AEE materials showed dramatic fluorescence switching with external force.…”

Piezochromism and hydrochromism through electron transfer: new stories for viologen materials

“…Recently there have been intense studies on piezochromic luminescence, where pressure induced a change in the photoluminescence color of the material. 10 In this paper, we are focused on innocent piezochromism, where pressure can induce a change in the natural color of the material. The phenomenon has been observed for various materials, including metal oxides/complexes (such as molybdates, 11 Cu( ii ) complexes, 2a,12 Ni( ii ) glyoximates 13 and Fe( ii ) spin-crossover compounds 14 ), polymers (such as polysilanes 15 and polythiophenes 16 ), organic molecules in polymer matrices, 17 and crystalline organic molecular solids.…”