1,2,3-Triazoles: Controlled Switches in Logic Gate Applications

A 1,2,3-triazole-based chemosensor is used for selective switching in logic gate operations through colorimetric and fluorometric response mechanisms. The molecular probe synthesized via "click chemistry" resulted in a non-fluorescent 1,4-diaryl-1,2,3-triazole with a phenol moiety (PTP). However, upon sensing fluoride, it TURNS ON the molecule's fluorescence. The TURN-OFF order occurs through fluorescence quenching of the sensor when metal ions, e.g., Cu2+, and Zn2+, are added to the PTP-fluoride ensemble. A detailed characterization using Nuclear Magnetic Resonance (NMR) spectroscopy in a sequential titration study substantiated the photophysical characteristics of PTP through UV-Vis absorption and fluorescence profiles. A combination of fluorescence OFF-ON-OFF sequences provides evidence of 1,2,3-triazoles being controlled switches applicable to multimodal logic operations. The "INH" gate was constructed based on the fluorescence output of PTP when the inputs are F- and Zn2+. The "IMP" and "OR" gates were created on the colorimetric output responses using the probe's absorption with multiple inputs (F- and Zn2+ or Cu2+). The PTP sensor is the best example of the "Write-Read-Erase-Read" mimic.

Excitation wavelength as logic operator

Multiple molecular logic gates were harvested on a single synthesized material, (E)-2-(2-hydroxy-3-methoxybenzylideneamino)phenol (MBAP), by combining excitation wavelength dependent multi-channel fluorescence outputs and the same chemical inputs. Interestingly, the effortless switching of logic behavior was achieved by simply tweaking the excitation wavelength and sometimes the emission wavelengths with no alteration of chemical inputs and the main device molecule, MBAP. Additionally, new generation purely optically driven memory units were designed on the same system supporting an almost infinite number of write-erase cycles since inter-conversion of memory states was completely free from chemical interferences and impurity issues. Two-way memory functions ("erase-read-write-read" and "write-read-erase-read") worked simultaneously on the same system and could be accessed by simple optical switching between two excitation and emission wavelengths. Our optically switchable device might outperform traditional multifunctional logic gates and memory devices that generally employ chemical triggers to switch functionality and memory states. These optically switchable multifunctional molecular logic gates and memory systems might drive smart devices in the near future with high energy efficiency, extended life span, structural and functional simplicity, exclusive reversibility and enhanced data storage density.

Diaminomaleonitrile-functionalized gelators in F−/CN− sensing, phase-selective gelation, oil spill recovery and dye removal from water

Diamiomaleonitrile-based gelators 1 and 2 were designed and synthesized. Toluene and 1,2-dichlorobenzene gels of 1 and 2, respectively sense F⁻ and CN⁻ anions. Both 1 and 2 show phase-selective gelation (PSG) with distinguishable feature. Toluene gel of 1 acts as injectable material and is applied in environmental remediation.

Chemosensing properties and logic gate behaviors of graphene quantum dot-appended terpyridine

Graphene quantum dot-covalently appended terpyridine, GQDs-tpy, was synthesized and characterized by X-ray photoelectron spectroscopy, FTIR spectroscopy and transmission electron microscopy. GQDs-tpy was found to act as multifunctional chemosensors: a highly selective colorimetric chemosensor for Fe²⁺ as evidenced by an obvious color change from colorless to pink, and a typical fluorescence enhanced probe for Zn²⁺ over 13 metal cations even in practical water samples. Moreover, two-input XOR, INHIBIT and IMPICATION logic gates as well as four-input OR and NOR logic gates were constructed according to the characteristic responses of GQDs-tpy to a sequence of cations.

A benzimidazole-based non-symmetrical tripodal receptor for the ratiometric fluorescence sensing of fluoride ions and solid state recognition of sulfate ions

A novel tripodal receptor has been reported as a fluorescent chemosensor for fluoride ions. Moreover, in solid state, seven units of the protonated receptors form a pseudo-capsular cavity to encapsulate two pairs of sulphate anions.

A2B corroles: Fluorescence signaling systems for sensing fluoride ions

Four free base corroles, 1-4, A₂B, (where A = nitrophenyl, and B = pentafluorophenyl, 2, 6-difluoro, 3, 4, 5-trifluoro and 4-carboxymethylphenyl group) have been synthesized, characterized and demonstrated as excellent chemosensor for the detection of fluoride ions selectively in toluene solution. The reported corroles shows highest quantum yield in free base form of porphyrinoid systems so far. All these corrole, 1-4, have the excellent ability to sense fluoride ion. Cumulative effect of static and dynamic factors is responsible for the quenching of fluorescence which indicates the detection of fluoride ion in solution.

Substituent directed selectivity in anion recognition by a new class of simple osmium-pyrazole derived receptors

The present article deals with the structurally, spectroscopically and electrochemically characterised osmium-bipyridyl derived complexes [(bpy)2Os(II)(HL1)Cl]ClO4 [1]ClO4 and [(bpy)2Os(II)(HL2)Cl]ClO4 [2]ClO4 incorporating neutral and monodentate pyrazole derivatives (HL) with one free NH function (bpy = 2,2'-bipyridine, HL1 = pyrazole, HL2 = 3,5-dimethylpyrazole). The crystal structures of [1]ClO4 and [2]ClO4 reveal intramolecular hydrogen bonding interactions between the free NH proton of HL and the equatorially placed Cl(-) ligand (N-HCl) with donor-acceptor distances of 3.114(7) Å and 3.153(6) Å as well as intermolecular hydrogen bonding interactions between the NH proton and one of the oxygen atoms of ClO4(-) (N-HO) with donor-acceptor distances of 2.870(10) Å and 3.024(8) Å, respectively. The effect of hydrogen bonding interactions has translated into the less acidic nature of the NH proton of the coordinated HL with estimated pKa > 12. 1(+) and 2(+) exhibit reversible Os(II)/(III) and irreversible Os(III)/(IV) processes in CH3CN within ± 2.0 V versus SCE. The effect of 3,5-dimethyl substituted HL2 on 2(+) has been reflected in the appreciable lowering (40 mV) of the Os(II/III) potential, along with the further decrease in the acidity of the NH proton (pKa > 13.0) with regard to HL1 coordinated 1(+) (pKa: ∼ 12.3). The electronic spectral features of Os(ii) (1(+)/2(+)) and electrochemically generated Os(III) (1(2+)/2(2+)) derived complexes have been analysed by TD-DFT calculations. The efficacy of the 1(+) and 2(+) encompassing free NH proton towards the anion recognition process has been evaluated by different experimental investigations using a wide variety of anions. It however establishes that receptor 1(+) can recognise both F(-) and OAc(-) in acetonitrile solution, while 2(+) is exclusively selective for the F(-) ion.

C 3v-symmetric anion receptors with guanidine recognition motifs for ratiometric sensing of fluoride

Two new tripodal receptors 3 and 4 derived from a trindane framework having guanidine groups acting as hydrogen bond acceptors are synthesized and characterized for the selective recognition of anions.

Novel structurally tuned DAMN receptor for “in situ” diagnosis of bicarbonate in environmental waters

A novel receptor for specific and prompt bicarbonate anion (HCO₃⁻) recognition is presented. HCO₃⁻ triggers facile ICT, which provides “in situ” recognition of water soluble carbonates. For the first time, “on-site” estimation of HCO₃⁻ in environmental waters is demonstrated.

Two and three input molecular logic operations mediated by a novel azo-azomethine based chromogenic probe through intramolecular charge transfer processes

A novel azo-azomethine based chromogenic receptor has been successfully designed and synthesized for the construction of multifunctional molecular logic circuits.

A naphthalimide-based ‘Pourbaix sensor’: a redox and pH driven AND logic gate with photoinduced electron transfer and internal charge transfer mechanisms

A molecular logic gate with a ‘receptor–spacer–fluorophore–spacer–redox-unit’ format emits a fluorescent signal on simultaneous oxidation and protonation in aqueous methanol solution.

An imidazolyl-pyreno-imidazole conjugate as a cyanide sensor and a set–reset memorized sequential logic device

A pyrenyl-bisimidazole system can act as an efficient cyanide sensor and a ‘set–reset’ memory device.