Sensory memory is capable of recording information and giving feedback based on external stimuli. Haptic memory in particular can retain the sensation of the interaction between the human body and the environment and help humans to describe the physical quantities in their environment and manipulate objects in daily activities. Although sensitive and accurate tactile sensors have been produced on optical and electronic devices, their rigorous operation and equipment requirements seriously limit their further applicability. In addition, their poor retainability after the removal of external stimuli also warrants further improvements. Thus, haptic memory materials, having simple structures and high sensitivity, are highly desired. Herein, we successfully developed two piezochromic assemblies assisted by halogen bonding for haptic memory. The halogen bond not only contributes to the fabrication of the network and enhances integrative stability but also broadens the natural piezofluorescent range, thus promoting sensory sensitivity. Moreover, the colorimetric change of the assemblies could be well-retained after the stimulus was removed. Upon mild heating treatment, the piezochromic response could be recovered to its original state, confirming the recyclability of this haptic memory material for use in practical applications. The present work enriches the library of piezochromic materials with enhanced performance for haptic memory.

Two thiourea and urea based indole conjugated ligands show selective color changes with fluoride along with an absorbance band at 936 nm and 904 nm respectively.

Tris(2‐aminoethyl)amine (tren) based 4‐cyanophenyl‐substituted tripodal L, tris{[(4‐cyanophenyl)amino]ethyl}thiourea receptor, was synthesized and explored thoroughly for anion recognition in solution by NMR spectroscopy and isothermal titration calorimetry (ITC) as well as in the solid state by single‐crystal X‐ray diffraction studies. Anion recognition properties of L were further exploited toward the extraction of sulfate as well as fluoride from aqueous media using a liquid–liquid extraction technique. A solution‐state anion binding study using NMR spectroscopy in [D6]DMSO and ITC measurements in dry acetonitrile show a relatively higher association constant of L with halides (F– and Cl–) over oxyanions (H2PO4– and HSO4–). The single‐crystal X‐ray structural analysis of complex 1 reveals a monotopic encapsulation of fluoride in L through six N–H···F– interactions with a distorted trigonal‐prismatic geometry, whereas sulfate and carbonate induce dimeric assemblies of L in complexes 2 and 3, respectively. In the case of sulfate, a tight dimeric capsular assembly of ca. 9.5 Å is observed through 15 N–H···O interactions, whereas carbonate forms a sandwich‐like dimeric molecular aggregation through 14 N–H···O interactions. In the presence of tetrabutylammonium iodide as the phase transfer agent, L has shown ca. 70 % extraction of fluoride (based on L) and ca. 40 % extraction of sulfate (based on L) from aqueous solutions using an anion‐exchange‐based liquid–liquid extraction strategy. Extraction of these anions is unambiguously demonstrated by 1H NMR, 19F NMR and FTIR spectroscopy, PXRD and single‐crystal X‐ray diffraction studies.

Fluorescent and electron-rich polymer threaded into porous framework provides a scaffold for sensing acceptor molecules through noncovalent interactions. Herein, poly(9-vinylcarbazole) (PVK) threaded MIL-101 with confined nanospace was synthesized by vinyl-monomer impregnation, in situ polymerization, and interpenetration. The pore size of the resulted hybrid could be controlled by varying the time of polymerization and interpenetration. The interaction of PVK-threaded MIL-101 with guest molecules showed a charge-transfer progress with an obvious red shift in the optical spectra. Depending on the degree of the interaction, the solution color changed from blue to green or to yellow. In particular, electron-rich PVK-threaded MIL-101 could effectively probe electron-poor nitro compounds, especially 1,3,5-trinitrobenzene (TNP), a highly explosive material. This sensing approach is a colorimetric methodology, which is very simple and convenient for practical analysis and operation.

A series of N-heterocyclic quinoxaline derivatives was successfully synthesized and applied as hole transport layers in quantum dot light-emitting diodes (QLEDs). By inducing sp(2) N-atoms into the quinoxaline backbone, the electron affinity of the obtained material was enhanced, and its optical properties and bandgap became tunable. Quinoxaline based N-heteroacenes show a narrow bandgap, high thermal stability, and aligned film morphology. The resulting N-heteroacene polymer based QLED exhibits superior performance to poly(9-vinylcarbazole) based QLED. This study presents a strategy towards the design of novel N-rich molecules for the fabrication of QLEDs with improved performance.

A series of new symmetrically functionalized guanidinium chlorides (S1-S10) are synthesized in good yields and their sensing ability toward anions is studied in MeCN-DMF (24 : 1) (v/v). The absorption bands of these molecules in the presence of anions are tuned by varying the functional groups attached to the guanidinium moiety (which resembles urea) with respect to (i) aromaticity (S1-S4), (ii) electron induction effect (S1, S5-S9), (iii) positional isomeric effect (S7-S9), (iv) indole functionality (S10) of the conjugated aryl units. Anions that are above Cl(-) in the Hofmeister series (F(-), AcO(-), H(2)PO(4)(-)) are eligible as an analyte in this series of molecules whereas less basic anions than Cl(-) do not cause any interference. Thus, this series of molecules are suitable for the detection of anions in the narrow window of the Hofmeister series. Out of all the anions, only fluoride causes vivid colour changes from yellow to red to reddish orange and finally to blue, irrespective of the increasing aromaticity, induction and positional isomeric effect of the substituent that is attached to the guanidinium moiety. Interestingly, S9 has shown the ability to sense distinctly both F(-) and AcO(-) colourimetrically. Further S10, a sensor attached with indole functionality shows selective sensing of F(-) colourimetrically with a NIR signature at ∼930 nm though both these outputs are very unstable in nature. Stability constants for complex formation of S1-S10 (except S5) with F(-), AcO(-) are calculated by UV-vis titration experiments. Finally single crystal X-ray structural studies on the species 1 formed upon treating S6 with sodium fluoride confirms -NH deprotonation, whereas the reaction of S6 and S2 with sodium benzoate shows 1:1 host:guest binding that results in complexes 2 and 3 respectively.

The tris(2-aminoethyl)amine-based (tren-based) 3-cyanophenyl-substituted tripodal urea L1, one of the familiar ureabased anion receptors, has shown encapsulation of CO 3 2ions as the carbonate capsule [(L1) 2 ·(CO 3 )·(TBA) 2 ] (1, TBA = tetrabutylammonium) by the fixation of aerial carbon dioxide from basic dimethyl sulfoxide (DMSO) solution. Single-crystal X-ray structural analysis confirmed the encapsulation of CO 3 2ions in the cavity of a dimeric capsular assembly of L1 (9.62 Å) through the formation of twelve strong N-H···O hydrogen-bonding interactions. The excellent CHCl 3 and CH 2 Cl 2 solubility of 1 has been exploited for the liquid-liquid (L-L) extraction of CrO 4 2-, SO 4 2-, and S 2 O 3 2ions from water by anion-exchange metathesis. The extraction of these anions from water was unambiguously confirmed by 1 H NMR spectroscopy, IR spectroscopy, powder XRD (PXRD), and single-crystal X-ray diffraction analysis. The 1 H NMR spectroscopic analysis of the bulk extracts supports the formation of 2:1 (host-guest) complexes. For the CrO 4 2ion, the 53 Cr NMR spectrum of the bulk extract shows a characteristic[a]

Water-soluble metal–organic complex array 1, bearing Ru(ii), Pt(ii) and Rh(iii) complexes at the side residues of the short peptide, exhibits anion and pH-responsive self-assembling behaviours in aqueous media.