Smart Organic Materials with Acidochromic Properties

Abstract

Smart materials displaying changes in colour and optical properties in response to acid stimuli are known as acidochromic materials. The recent progress and emerging trends in the field of smart organic materials with acidochromic properties reported in last seven years are presented herein. The molecular design of acidochromic organic materials, origin of the chromic and fluorochromic response to acid stimuli and related mechanisms are also discussed. Materials and systems covered in the review are divided according to the presence of basic moiety undergoing reversible protonation/ deprotonation, such as pyridine, quinoline, quinoxaline, azole, amine derivatives etc. in the molecules. Many donoracceptor molecules displaying acidochromic behaviour are cited. Alterations in visual colour change and optical properties supporting acidochromism are discussed for each example. Mechanistic studies based on the theoretical calculations, single crystal X-ray diffraction analysis and powder pattern diffraction analysis are also discussed. The application of these acidochromic molecules as acid-base switches, sensor films, self-erasable and rewritable media, data security inks, data encryption, molecular logic gates etc., are also reported. Thus, the review article aims at giving an insight into the design, characterization, mechanism and applications of organic acidochromic materials which will guide the researchers in designing and fine-tuning new acidochromic materials for desired applications

pH-Responsive N^C-Cyclometalated Iridium(III) Complexes: Synthesis, Photophysical Properties, Computational Results, and Bioimaging Application

“…550 nm ( Figure 2 B,D) to give a white color emission ( Figure 2 F, spectrum iii). A similar effect of generation of the white color emission was observed upon protonation of closely analogous push–pull azaheterocyclic systems [ 36 , 37 ]. At high TFA concentration, the emission spectrum displays strong bright-green band with the maximum at 510 nm ( Figure 2 D,F, spectrum iv).…”

1,7/8-Substituted isoquinoline derivatives: position isomerism caused by HIO3-induced dehydrogenation and solid-state fluorescence stimulus-responsive properties

“…Solid-state fluorescent stimulus-responsive compounds, which are regarded as smart materials, have aroused great interest because of the extensive applications in information storage, fluorescent sensors, and security devices. 1 Mechanofluorochromic (MFC) 2 and solid-state acidochromic 3 compounds can exhibit obvious fluorescence color changes upon pressure and acid vapor in the solid state, respectively. Furthermore, the phenomenon of mechanofluorochromism is often accompanied by vaporchromism and thermochromism, 2 which makes it possible to develop multi-stimulus-responsive fluorescent materials.…”

Multi Stimuli Responsive Non‐Doped Red Emitting AIEE Active Phenothiazine‐Based Chalcones: Crystal Structure, Solvatochromism, Turn‐on Mechanofluorochromism and Acidochromism

“…Therefore, we envisaged that the compounds containing carbonyl oxygen might also be utilized as probes for acidochromism. [58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73] In this work, we have designed and synthesized a series of three symmetrical red-colored chalcone derivatives containing two non-planar electron-rich phenothiazine units linked together through a cross-conjugated system, giving a D-π-A-π-D type push-pull molecular arrangement (Figure 1). To fine tune the photophysical properties, different alkyl chains (n = 2À 4) were substituted at position 10 of the phenothiazine units.…”