Fluorescent N‐Heteroacene‐Based π‐Conjugated Liquid Responsive to HCl Vapor

Abstract

In this paper, we describe here the first room temperature π‐conjugated liquid based on N‐heteroacene framework showing a fluorescent property. This π‐conjugated liquid N‐heteroacene molecule is composed of branched‐long alkoxy chains and thiophene moieties. Also, N‐heteroacene‐based liquid itself can function as a stimuli‐responsive photofunctional material unlike room temperature π‐conjugated liquids reported previously. When a coated film prepared from this liquid was exposed to HCl vapor, an adsorption of HCl molecules occurred accompanied to the change in color of film from yellow to deep yellow. Moreover, emission colors of a coated film markedly changed from blue to yellow. This result indicates that this π‐conjugated liquid N‐heteroacene can function as stimuli‐responsive functional material.

Tuning the Electronic Properties and Acid‐Response Behavior of N‐Heteroacene‐Based π‐Conjugated Liquids by Changing the Number of π‐Conjugated Substituents

“…[18][19][20][21][22][23] We previously reportedt hat a p-conjugated liquid that was composed of an N-heteroacene framework respondedt oH Cl vapor,t hereby resultingi nad ramatic change in the color of its photoluminescence. [15] Herein, we report the synthesis of an ew stimuli-responsive p-conjugated liquid (1) that was composed of an N-heteroacene framework with finely tuned electronic properties as well as acid-responsive capabilities.…”

“…We had previouslyr eportedt hat the electronic properties of fluidic liquid 2 could be tuned by its exposure to HCl vapor,w hich causedi ts fluorescencet oc hange from blue to yellow. [15] However,t his system encountered ac rucial problem with the volatilization of HCl molecules from the fluidic liquid. Herein, we chose as eries of nonvolatile solid-state acids ubstances with variouspK a values:benzenesulfonic acid (a;pK a = À2.5), benzoic acid (b;p K a = 4.2), and 1-adamantanecarboxylic acid( c; pK a = 6.8).…”

“…Recently, room‐temperature π‐conjugated liquids have emerged as new functional fluidic liquid materials, and have exhibited photoluminescence, transport carrier, molecular recognition, redox, and stimuli‐responsive properties . In general, these intrinsic electronic properties depend on the functional π‐conjugated framework.…”

“…N‐Heteroacenes are capable of recognizing Brønsted acids through the lone‐pair electrons of the imino N atoms, which are characteristic of Lewis‐basic sp 2 ‐hybridized orbitals . We previously reported that a π‐conjugated liquid that was composed of an N‐heteroacene framework responded to HCl vapor, thereby resulting in a dramatic change in the color of its photoluminescence . Herein, we report the synthesis of a new stimuli‐responsive π‐conjugated liquid ( 1 ) that was composed of an N‐heteroacene framework with finely tuned electronic properties as well as acid‐responsive capabilities.…”

“…[7,8] Recently,r oom-temperature p-conjugated liquidsh ave emerged as new functional fluidic liquid materials, [6] andh ave exhibited photoluminescence, [9,10] transport carrier, [11] molecular recognition, [12] redox, [13] and stimuli-responsivep roperties. [14,15] In general, these intrinsic electronic properties depend on the functional p-conjugated framework. Until now,t he conventional method for designing room-temperature photofunctional pconjugated liquids has been to introduce multiple flexible alkyl chains ontot he terminio fp-conjugated frameworks.…”