Selective Detection of Trinitrophenol by Amphiphilic Dimethylaminopyridine-Appended Zn(II)phthalocyanines at the Near-Infrared Region

Aza-BODIPY-based logic gate chemosensors and their applications

Dimethylaniline-substituted aza-BODIPY dyes (DA, DM, DP) were designed and synthesized aiming for ion detection. The Zn2+ recognition ability was found in all compounds and the binding mechanism was possibly via dimethylaniline sites linked to the aza-BODIPY core. Upon Zn2+ addition, the new absorption band and the color change occurred due to the altered charge transfer of the adducts. The custom-made colorimeter was successfully integrated into the dye's application, demonstrating a good linear relationship between resistance values and Zn2+ concentration. The chromophore test strips were fabricated and exhibited distinct color changes upon aqueous Zn2+ exposure. The compound DA also exhibits logical behavior with DA-Zn2+-Cu2+ system. In terms of environmental hazards, the compounds exhibited no adverse effect on Pseudomonas putida at the concentration level of 0.2 mg/mL. These findings indicated that all synthesized aza-BODIPYs might be suitable for chemosensor probes for Zn2+ detection with possibly low environmental risk.

Tellurium Containing Long Lived Emissive Fluorophore for Selective and Visual Detection of Picric Acid through Photo-Induced Electron Transfer

A novel tellurium (Te) containing fluorophore, 1 and its nickel (2) and copper (3) containing metal organic complex (MOC) have been synthesized to exploit their structural and optical properties and to deploy these molecules as fluorescent probes for the selective and sensitive detection of picric acid (PA) over other commonly available nitro-explosives. Furthermore, density functional theory (DFT) and single crystal X-ray diffraction (SCXRD) techniques revealed the inclusion of "soft" Tellurium (Te) and "hard" Nitrogen (N), Oxygen (O) atoms in the molecular frameworks. Owing to the presence of electron rich "N" and "O" atoms along with "Te" in the molecular framework, 1 could efficiently and selectively sense PA with more than 80 % fluorescence quenching efficiency in organic medium and having detection limit of 4.60 μM. The selective detection of PA compared to other nitro-explosives follows a multi-mechanism based "turn-off" sensing which includes photo-induced electron transfer (PET), electrostatic (π-π stacking and π-anion/cation) interaction, intermolecular hydrogen bonding and inner filter effect (IFE). The test strip study also establishes the sensitivity of 1 for detection of PA.

Fluoranthene-terminated terpyridine ensemble for fluorescence light up and ratiometric chemical sensor for multi toxic metals

A novel π-electron rich fluoranthene embellished with a phenyl spacer and coupled with terpyridine (TS1) was developed through Diels-Alder reaction. Single crystal X-ray structure evidences the variations in dihedral angles between the fluoranthene and the phenyl unit responsible for development of non-coplanar interactions and stabilized by a wave-like molecular packing in the crystal lattice with weak π-π interaction of 4.125 Å. The peripheral terpyridine of TS1 endows an efficient binding with multiple metal ions by colorimetric and fluorometric methods. TS1 exhibits a ratiometric fluorescence response from sky blue to yellow colour upon the addition of Zn²⁺ ions with a limit of detection (LOD) of 0.05 ppm. The other metal ions such as Cu²⁺, Co²⁺ and Fe²⁺ demonstrate fluorescence quenching behaviour with LODs of 0.1, 0.3 and 0.7 ppm, respectively. The intramolecular charge transfer (ICT) shows the variation in TS1 emission behaviour upon metal ions interaction and quantitatively discriminates the metal ion concentrations. TS1 conferred a visual colorimetric change from colourless to magenta, enabling naked-eye detection of Fe²⁺ and showing clear discrimination between Fe²⁺ and Fe³⁺ ions for the real-time water samples. Furthermore, we have investigated the effect of TS1 in Zebrafish larvae/embryos and cytotoxicity in human urinary tract transitional cell carcinoma cells (UM-UC-3).

A Gelation-Induced Enhanced Emission Active Stimuli Responsive and Superhydrophobic Organogelator: "Turn-On" Fluorogenic Detection of Cyanide and Dual-Channel Sensing of Nitroexplosives on Multiple Platforms

A pyrene-based highly emissive low-molecular-weight organogelator, [2-(4-fluorophenyl)-3-(pyren-1-yl)acrylonitrile] (F1), is presented, which divulges thixotropic and thermochromic fluorescence switching via reversible gel-to-sol transition and tremendous superhydrophobicity (mean contact angles: 149-160°), devoid of any gelling and/or hydrophobic units. The rationale for the design strategy reveals that the restricted intramolecular rotation (RIR) in J-type self-assembly promotes F1 for the prolific effects of aggregation- and gelation-induced enhanced emission (AIEE and GIEE). Meanwhile, hindrance in charge transfer via the nucleophilic reaction of cyanide (CN^-) on the C═C unit in F1 facilitates the selective fluorescence "turn-on" response in both solution [9:1 (v/v) DMSO/water] and solid state [paper kits] with significantly lower detection limits (DLs) of 37.23 nM and 13.4 pg/cm², respectively. Subsequently, F1 discloses CN^- modulated colorimetric and fluorescence "turn-off" dual-channel response for aqueous 2,4,6-trinitrophenol (PA) and 2,4-dinitrophenol (DNP) in both solution (DL = 49.98 and 44.1 nM) and solid state (DL = 114.5 and 92.05 fg/cm²). Furthermore, the fluorescent nanoaggregates of F1 in water and its xerogel films permit a rapid dual-channel "on-site" detection of PA and DNP, where the DLs ranged from nanomolar (nM) to sub-femtogram (fg) levels. Mechanistic insights reveal that the ground-state electron transfer from the fluorescent [F1-CN] ensemble to the analytes is responsible for anion driven sensory response, whereas the unusual inner filter effect (IFE) driven photoinduced electron transfer (PET) was responsible for self-assembled F1 response toward desired analytes. Additionally, the nanoaggregates and xerogel films also detect PA and DNP in their vapor phase with reasonable percentage of recovery from the soil and river water samples. Therefore, the elegant multifunctionality from a single luminogenic framework allows F1 to provide a smart pathway for achieving environmentally benign real-world applications on multiple platforms.

One-pot synthesis of poly(vinylpyrrolidone)-encapsulated color-emitting silicon quantum dots for sensitive and selective detection of 2,4,6-trinitrophenol

Here, we illustrate an efficient, convenient, and simple method for the sensitive and selective detection of nitro explosive 2,4,6-trinitrophenol (TNP) in 100% water medium by bright cyan-blue color emitting colloidal...

Combinatorial selectivity with an array of phthalocyanines functionalized TiO2/ZnO heterojunction thin film sensors

The development of electronic noses requires the control of the selectivity pattern of each sensor of the array. Organic chemistry offers a manifold of possibilities to this regard but in many cases the chemical sensitivity is not matched with the response of electronic sensor. The combination of organic and inorganic materials is an approach to transfer the chemical sensitivities of the sensor to the measurable electronic signals. In this paper, this approach is demonstrated with a hybrid material made of phthalocyanines and a bilayer structure of ZnO and TiO₂. Results show that the whole spectrum of sensitivity of phthalocyanines results in changes of the resistance of the sensor, and even the adsorption of compounds, such as hexane, which cannot change the resistance of pure phthalocyanine layers, elicits changes of the sensor resistance. Furthermore, since phthalocyanines are optically active, the sensitivity in dark and visible light are different. Thus, operating the sensor in dark and light two different signals per sensors can be extracted. As a consequence, an array of 3 sensors made of different phthalocyanines results in a virtual array of six sensors. The sensor array shows a remarkable selectivity respect to a set of test compounds. Principal component analysis scores plot illustrates that hydrogen bond basicity and dispersion interaction are the dominant mechanisms of interaction.

Azine Steric Hindrances Switch Halogen Bonding to N-Arylation upon Interplay with σ-Hole Donating Haloarenenitriles

An interplay between 4-bromo- and 4-iodo-5-nitrophthalonitriles (XNPN, X=Br or I) and any one of the azines (pyridine 1, 4-dimethylaminopyridine 2, isoquinoline 3, 4-cyanopyridine 4, 2-methylpyridine 5, 2-aminopyridine 6, quinoline 7, 1-methylisoquinoline 8, and 2,2'-bipyridine 9) proceeds differently depending on steric and electronic effects of the heterocycles. Sterically unhindered azines 1-3 underwent N-arylation to give the corresponding azinium salts (characterized by ¹ H and ¹³ C{H} NMR and high-resolution ESI-MS). In contrast, azines 4-9 with sterically hindered N atoms or bearing an electron-withdrawing substituent, form stable co-crystals with XNPN, where two interacting molecules are bound by halogen bonding. In all obtained co-crystals, X⋅⋅⋅N structure-directed halogen bonds were recognized and theoretically evaluated including DFT calculations (PBE0-D3/def2-TZVP level of theory), QTAIM analysis, molecular electrostatic potential surfaces, and noncovalent interaction plot index. Estimated energies of halogen bonding vary from -7.6 kcal/mol (for 6 ⋅ INPN) to -11.4 kcal/mol (5 ⋅ INPN).

Dually directional glycosylated phthalocyanines as extracellular red-emitting fluorescent probes

The development of new non-aggregated phthalocyanines bearing multivalent saccharide moieties on their macrocyclic rims is of great interest. Many characteristics, including water-solubility, non-toxicity and others, can be feasibly obtained by these amphiphiles which can be considered as a key solution for demonstrating highly efficient photoactive materials in water. Herein, a family of five newly prepared dually directional Zn(ii) containing phthalocyanines (PcG1-4) and azaphthalocyanine (AzaPcG1) glycoconjugates is described. The unique spatial arrangement of the glucoside units based on peripherally hexadeca-(PcG1) and nonperipherally octa-(PcG4) macrocycles provides a fully monomeric behaviour along with a high fluorescence (Φ_F∼ 0.21) in aqueous solution. These amphiphiles were characterized by low toxicity, and an extremely low cellular uptake was obtained due to the highly polar nature of the glucoside substituents. Accordingly, their potential as suitable photoactive chromophores for red-emitting extracellular fluorescent probes has been confirmed upon the evaluation of paracellular transport using a layer of MDCKII cells with the permeability coefficient fully comparable with an established evaluator of the integrity of the monolayer.

Multivalent Allyl-Substituted Macrocycles as Nonaggregating Building Blocks

Based on the concept of dual-directionality, the synthesis of two novel zinc(II)-containing phthalocyanine (Pc-ene1) and azaphthalocyanine (AzaPc-ene1) macrocycles bearing dual directional (up/down) allyl moieties on their rims is reported. Their structural identification, that is, NMR, FT-IR, UV-vis, MALDI-TOF spectral data, single crystal X-ray diffraction, and CHN elemental analyses, along with their nonaggregating behaviors in solvated media and crystalline forms has been confirmed.

Polyhydroquinoline nanoaggregates: A dual fluorescent probe for detection of 2,4,6-trinitrophenol and chromium (VI)

Fluorescent polyhydroquinoline (PHQ) derivative was fabricated utilizing one-pot engineered course. The PHQ derivative indicated aggregation induced emission enhancement (AIEE) with arrangement of nanoaggregates of size 11-13 nm in 95% watery DMF medium. The fluorescence emission of PHQ nanoaggregates was extinguished by including TNP and Cr (VI). They indicated prevalent fluorescence quenching towards both TNP and Cr (VI) over other meddling nitro-compounds and metal particles. In light of results got we presumed that both photo-induced fluorescence quenching of PHQ nanoaggregates by TNP, while Inner Filter Effect (IFE) was in charge of fluorescence quenching of PHQ nanoaggregates by Cr (VI). The PHQ nanoaggregates empowered identification of TNP and Cr (VI) down to 0.66 μM (TNP) and 0.28 μM (Cr (VI)). The use of PHQ nanoaggregates were reached out for location of TNP and Cr (VI) in genuine water tests.

A phthalocyanine sensor array based on sensitivity and current changes for highly sensitive identification of three toxic gases at ppb levels

The first phthalocyanine-based sensor array by the combination of two parameters, namely current change direction and sensitivity, for accurate discrimination and wide range of detection of three toxic gases at ppb levels.