Rational Design of a Green-Light-Mediated Unimolecular Platform for Fast Switchable Acidic Sensing

Abstract

A controllable sensing ability strongly connects to complex and precise events in diagnosis and treatment. However, imposing visible light into the molecular-scale mediation of sensing processes is restricted by the lack of structural relevance. To address this critical challenge, we present the rational design, synthesis, and in vitro studies of a novel cyanostyryl-modified azulene system for green-light-mediated fast switchable acidic sensing. The advantageous features of the design include a highly efficient green-light-driven Z/E-isomerization (a quantum yield up to 61.3%) for fast erasing chromatic and luminescent expressions and a superior compatibility with control of ratiometric protonation. Significantly, these merits of the design enable the development of a microfluidic system to perform a green-light-mediated reusable sensing function toward a gastric acid analyte in a miniaturized platform. The results may provide new insights for building future integrated green materials.

Involving Synergy of Green Light and Acidic Responses in Control of Unimolecular Multicolor Luminescence

“…[8] Cyanostilbene is at ypical light-activem oiety,w hich can exhibit ap owerful push-pull effect through derivation and isomerization, accompanied with itsp hotophysical property tuning. [10] By this modification strategy,t he absorption band of cyanostyrylmodified azulene moiety can cover an apparent visible-light regioni na cidic environmenta nd ensure ah igh-efficient visible-light driven photoisomerization.O nt he other hand, naphthalimide derivatives are typical donor-p-acceptor emitters, the emissioni ntensitya nd wavelength of whicha re sensitive to pH and polarity. [10] By this modification strategy,t he absorption band of cyanostyrylmodified azulene moiety can cover an apparent visible-light regioni na cidic environmenta nd ensure ah igh-efficient visible-light driven photoisomerization.O nt he other hand, naphthalimide derivatives are typical donor-p-acceptor emitters, the emissioni ntensitya nd wavelength of whicha re sensitive to pH and polarity.…”

“…[13] Next, the resonances of proton1 on the 5-membered ring of azuleneu nderwent ad ownfield shift upon addition of ar elative large amount of TFA, whereas the proton 4o n7 -membered ring experienced an upfield shift (Figure 2d-g). [10,15] To furthere xplore the mechanism of the progressive protonation process, we turned to investigate the photophysical properties. [8d, 14] Thus, we can see ap rogressive acidic response with as equential protonation of piperazine and azulenew as exhibited in our system.W ith the employmento ft he 1 H-1 H COSY spectrat oa ssist the characterizations, the two-stage proton resonance changec an be additionally confirmed (see Figure S15).…”

“…[9] Recently,w ed eveloped af ascinating structure by connecting cyanostyryl unit onto 6-position of azulene. [10] By this modification strategy,t he absorption band of cyanostyrylmodified azulene moiety can cover an apparent visible-light regioni na cidic environmenta nd ensure ah igh-efficient visible-light driven photoisomerization.O nt he other hand, naphthalimide derivatives are typical donor-p-acceptor emitters, the emissioni ntensitya nd wavelength of whicha re sensitive to pH and polarity. [11] In this work, we synthesized an ovel multiemissived yad by bridging cyanostyryl azulene moiety and 4piperazinyl-1,8-naphthalimidew ith 1,10-decylene as as pacer (compound AZU-NA,see Figure 1).…”

“…Direct photoisomerization is inaccessible firstly (see those photodegradation curves under 254 nm irradiation and unchangeable ones under 365 nm irradiation in Figure S3), because azulene form is pronetoquenchthe intermediate triplet state and makes the photoisomerization processi nsensitivea sc onsisted with those earlier findings. [10,12] However,the dyad can exhibit aunique light-responsive behaviour after the protonation process. And this property readilyc auses the orthogonal operations of acidic response and photoirradiation in our single molecular system.…”

“…The presentation of such ap rogressive protonation process is resulted from distinct equilibrium constantso ft he proton to the different binding sites. [10,15] To furthere xplore the mechanism of the progressive protonation process, we turned to investigate the photophysical properties. By monitoring the UV/ Vis absorption of the dyad, we can clearly denote a two-stage optical signal change upon addition of TFA.…”