Search

Two novel fluorescent probes namely 3-(2,4-dinitrophenoxy)-2-(4-(diphenylamino)phenyl)-4H-chromen-4-one (P1) and 3-(2,4-dinitrophenoxy)-2-(pyren-1-yl)-4H-chromen-4-one (P2) were designed and synthesized here. The probes (P1 and P2) were found to be highly selective and sensitive towards hydrogen sulfide (H2S) in presence of wide range of anions. The new probes (P1 and P2) were fully characterized by analytical, NMR spectroscopy (1H and 13C) and ESI mass spectrometry. The sensing capability of chemodosimeters (P1 and P2) towards H2S was confirmed by fluorescence studies. The ‘turn-on’ fluorescence was used to calculate detection limit of probes (LOD) which were found to be 2.4 and 1.2 μM for P1 and P2 respectively. Moreover, the probes were tested for their cytotoxicity against HeLa cells using MTT assay and found to be non-cytotoxic in nature and hence the probes P1 and P2 were successfully utilized to visualize H2S in living cells.

In this work we report on new heteroleptic coordination compounds [Pb2(LI)2](NO3)2∙2MeOH (1), [Pb2(LII)2](NO3)2 (2), [Pb2(LIII)2](NO3)2∙MeOH∙H2O (3) and [Pb2(LIII)2(H2O)](NCS)2 (4), which were obtained through self-assembling of 2-(amino(pyridin-2-yl)methylene)hydrazine-1-carbothioamide (HLI), 2-(amino(pyrazin-2-yl)methylene)hydrazine-1-carbothioamide (HLII) or 2-(amino(pyridin-2-yl)methylene)-N-methylhydrazine-1-carbothioamide (HLIII) with Pb(NO3)2 or a mixture of Pb(ClO4)2 and KNCS, respectively. In all the obtained complexes the lead(II) cation is N,N',S-chelated by the tridentate pincer type monodeprotonated ligand LI–III. In addition to the thiosemicarbazone chelation, the sulfur atom in each structure acts as bridging to connect two [Pb(LI–III)]+ units to form a dinuclear dimeric species having a centrosymmetric geometry, so that the ligands are directed either at different, in 1 and 2, or the same, in 3 and 4, side of the coplanar Pb2S2 core. In the latter structures two metal centers are additionally linked with each other through the oxygen atom of the bridging water molecule. The dimeric units in 1–4 are further linked through the Pb–N tetrel bonds, yielding 1D supramolecular polymeric chains, which, in turn, are interlinked though a myriad of other intermolecular noncovalent inetaractions, including tetrel bonds, hydrogen bonds and π-stacking. Counterions (NO3– and NCS–) as well as co-crystallized solvent molecules (MeOH and H2O) are also responsible in further stabilization of the overall crystal packing of the obtained complexes as a source of either tetrel and/or hydrogen bonds. The observation of the recurrent tetrel bonds in compounds 1–4 has been rationalized using DFT calculations and molecular electrostatic potential (MEP) surface plots. Moreover, coordination bonds (covalent character) and tetrel bonds (noncovalent character) between the complexes and their conterions (and water moelcule) have been differentiated using the quantum theory of «atoms-in-molecules» (QTAIM) and the noncovalent interaction index (NCI index) computational methods.

A novel fluorescent probe 2-(4-(diethylamino)-2-hydroxybenzylidene)-N-(2,3,3-trimethylbicyclo[2.2.1]heptan-2-yl)hydrazinecarbothioamide (HT) was prepared in this study by a condensation reaction. HT has been confirmed to possess high specificity toward Ga3+ over other metal ions (including Al3+ and In3+) via a distinct fluorescence light-up response. Moreover, HT exhibited good detection performances for Ga3+ including high selectivity, excellent anti-interference ability, a wide working pH range, and good reversibility. The association constant and limit of detection (LOD) were calculated to be 5.34 × 103 M-1 and 1.18 × 10-6 M, respectively. The detection mechanism of HT toward Ga3+ was proposed and confirmed by 1H NMR analysis, HRMS analysis, and DFT calculations. A simple test strip-based portable detecting device and a molecular INHIBIT logic circuit were established for improving its practical applicability. Furthermore, the desirable sensing performance of HT for Ga3+ was successfully reconfirmed in MCF-7 cells and zebrafish.

A microcrystalline Cd(II)-MOF, [Cd(NH2-bdc)(azp)]·DMF (NH2-H2bdc = 2-amino-1,4-benzenedicarboxylic acid and azp = 4,4′-azopyridine), namely 1-NH2 was rationally designed and synthesized as a fluorescent sensor in the off state utilizing the photo-induced electron transfer (PET) process. The crystal structure of 1-NH2 features a porous 2-fold interpenetrated 3D framework with 1D channels decorated with open Lewis basic amino and azo groups for recognizing the target species. Time-dependent density functional theory (TD-DFT) calculations were performed to gain insight into the PET process that induces the fluorescent quenching of 1-NH2. The proposed 1-NH2 is the first MOF that presents highly selective and sensitive visual turn-on fluorescence detection of glyphosate and Cr3+ with very low detection limits of 25 nM and 0.6 μM, respectively. The amino moiety in 1-NH2 plays a key role for the selective binding of Cr3+ to facilitate the sensitivity and selectivity of the detection. The fluorescent enhancement mechanism is associated with the inhibition of the PET process stimulated by the dissociation of the framework of 1-NH2 in the presence of glyphosate and Cr3+.

An unsymmetrical diphenylphosphino-pyridinyl-triazole ligand was synthesized and characterized through IR, NMR and MS and the corresponding earth-abundant metal complex (cobalt) was prepared. Considering energy consumption and environmental friendliness, it is necessary to turn this diphenylphosphino-pyridinyl-triazole cobalt complex into a recyclable catalyst, which could easily be reused. Therefore, a heterogeneous catalyst was synthesized through Co-doping of C3N4, and the Co-nanoparticles on C3N4 revealed high catalytic activity for the synthesis of quinolines with good recovery performance.

Aggregation-caused quenching (ACQ) and aggregation-induced emission (AIE) are dictated by the molecular aggregation which in turn is decided by the chemical features present in a molecule. The photophysical properties of bis(pyrenyl)-di-imines were investigated in solution as well as the solid state. It was observed that the light-emitting properties are dependent on the type of spacer group present in the compound. The presence of an alkylene spacer [ethylene (L3), butylene (L4), and hexylene (L5)] in bis(pyrenyl)-di-imines showed AIE at higher concentrations as well as in the solid state whereas the presence of a phenylene (L1) spacer and the absence of any alkyl/aryl spacer (L2) in the compound have resulted in ACQ in the solid state. Crystal structure analysis of L1 has explained its non-emissive nature in the solid state, while the AIE in the compounds, L3–L5, where flexible alkylene spacers are present, provided an idea about the solid-state arrangement of the molecules.

σ-hole and lone-pair (lp) hole interactions of trivalent pnicogen-bearing (ZF3) compounds were comparatively scrutinized, for the first time, under field-free and external electric field (EEF) conditions. Conspicuously, the sizes of the σ-hole and lp-hole were increased by applying an EEF along the positive direction, while the sizes of both holes decreased through the reverse EEF direction. The MP2 energetic calculations of ZF3⋯FH/NCH complexes revealed that σ-holes exhibited more impressive interaction energies compared to the lp-holes. Remarkably, the strengths of σ-hole and lp-hole interactions evolved with the increment of the positive value of the considered EEF; i.e., the interaction energy increased as the utilized EEF value increased. Unexpectedly, under field-free conditions, nitrogen-bearing complexes showed superior strength for their lp-hole interactions than phosphorus-bearing complexes. However, the reverse picture was exhibited for the interaction energies of nitrogen- and phosphorus-bearing complexes interacting within lp-holes by applying the high values of a positively directed EEF. These results significantly demonstrate the crucial influence of EEF on the strength of σ-hole and lp-hole interactions, which in turn leads to an omnipresent enhancement for variable fields, including biological simulations and material science.

Cysteine is widely used as a stabilizer for the preparation of fluorescent gold nanoclusters (Au NCs) with different fluorescence properties. Herein, by using cysteine as a stabilizer and controlling the synthesis conditions, a new non-fluorescent cysteine stabilized gold nanocluster (Cys-Au NCs) probe was prepared and a new strategy for "turning on" the fluorescence of the Cys-Au NCs was studied for rapid and selective detection of silver ions. In this strategy, the addition of silver ions to non-fluorescent Cys-Au NCs solution could quickly induce a visible fluorescence "turn on" phenomenon in 30 s. Further studies indicated that this fluorescence "turn on" phenomenon is specific for silver ions and the "turn on" fluorescence intensity has a linear relationship with the amount of silver ions in the range from 3.0 to 30.0 μM. Therefore, the non-fluorescent Cys-Au NCs were applied to the detection of silver ions in environmental water samples and a limit of detection (LOD) of 0.26 μM was obtained. This research sheds light on new applications of Au NCs and proposes a simple, rapid, sensitive, and visual method for the detection of metal ions.

Homochiral metal-organic frameworks (HMOFs) have garnered considerable attention due to their extrachiral properties and broad application for chiral recognition. However, assembling a pair of high-quality chiral MOFs for sensing enantiomers precisely is a formidable challenge because of the complicated chiral environment and uncontrollable coordinated conditions. Herein, one pair of homochiral UiO-66 analogues, S-1 (l-AP@UiO-66-(COOH)2) and R-1 (d-AP@UiO-66-(COOH)2), are reported for chiral recognition. They were fabricated via a condensation reaction between the carboxyl groups of UiO-66-(COOH)2 and amino groups of l/d-amino propanol (l/d-AP). These novel fluorescent probes exhibited highly enantioselective fluorescence enhancement towards l/d-phenylalaninol (l/d-PA). For example, when S-1 and R-1 were treated with l-PA or d-PA, they displayed different fluorescence responses: the enantiomeric fluorescence enhancement ratio (ef) was 2.51 and 0.41 for S-1 and R-1, respectively. Hence, a visible difference in fluorescence enhancement for l-PA and d-PA and excellent enantioselective behavior between S-1 and l-PA (or R-1 and d-PA) was displayed. Measurements of fluorescence lifetime, powder X-ray diffraction, molecular-dynamic simulations and Benesi-Hildebrand plots were employed to determine the observed high enantioselectivity for l/d-PA. In brief, we found that two post-modified HMOFs, S-1 and R-1, were outstanding enantioselective sensors for detecting l-PA and d-PA. They had a prominent difference in ef and remarkable enantioselectivity factor α and ΔΔG based on steric hindrance and stereochemical difference.

The dioxomolybdenum(VI) complex MoO2Cl2(dmf)2 reacts with Pb(DOPOQ)2 (DOPO = 2,4,6,8-tetra-tert-butyl-1,9-dioxophenoxazinate) to give MoO2(DOPOQ)2, which has an eight-coordinate structure with normal molybdenum-oxo bond distances and angles but elongated distances to the dioxophenoxazine ligand. The dioxo complex is deoxygenated by phosphines to produce octahedral Mo(DOPOCat)2, in which reduction has taken place at the ancillary ligands. This compound in turn reacts with trimethylamine-N-oxide to regenerate MoO2(DOPOQ)2, allowing a catalytic cycle for phosphine oxidation. This represents an example of four-electron nonclassical oxygen atom transfer in which both the oxidized and reduced forms of the metal complexes can be observed.

The “turn-on” probe PIA(OH)-Py responds to Cu2+ in living cells and can determine the concentration of Cu2+ in blood samples.

The development of turn-on detection sensors for methanol vapor remains challenging in materials science. Methanol sensing materials are generally based on vapor-triggered color changes or are turn-off types. Additionally, in general, the selectivity for methanol is limited, and the recyclability is low. Turn-on type sensing, high selectivity, rapid response time, and recyclability are favorable for achieving real-time detection systems. Herein, platinum(ii) dihalide (PtX2, X = Cl, Br, and I) complexes with 21-dibenzoarsacrown-7 were synthesized and their structures were characterized by single-crystal diffraction analysis. The PtCl2 complex showed intense emission when capturing methanol molecules in the crystalline matrix. In addition, this sensing system possessed high selectivity for methanol vapor and required facile recycling procedures.

The effective detection of Al3+ and antibiotics pollutants is crucial for environmental protection and human health due to their high toxicity and nondegradability, but it is still currently challenging. In this work, a methyl-decorated acylamide-containing dicarboxylate ligand H2L was elaborately designed and successfully synthesized, which was further employed to react with Zn(II) ions and dpe ligands to construct a new luminescent Zn-MOF, namely {[Zn(L)(dpe)]·DMF·3H2O}n (1). X-ray crystallography reveals that MOF 1 is a 3D 8-fold [4 + 4] interpenetrated diamondoid framework with isolated DMF and water molecules in the pores, in which the uncoordinated acylamide groups are found and facilitate the Zn-MOF to recognize analyte molecules. The activated solvent-free MOF sample (denoted as 1a) exhibits excellent water stability and good luminescent performance. The luminescence sensing experiments show that 1a could behave as a bi-responsive chemical sensor for “turn-on” and “turn-off” luminescent detection of Al3+ and SNT in aqueous media, respectively. The sensing mechanisms have also been discussed. Furthermore, MOF 1a was successfully applied to the effective determination of Al3+ and SNT in real water samples. This represents, to our knowledge, the first example of a MOF material for “turn-on” and “turn-off” luminescent detection of Al3+ and SNT in water, which will promote the practical application of water-stable luminescent MOF sensors in monitoring metal ions and antibiotics pollutants in the environmental water matrices.

Fluorescence imaging plays an important role in researching the biological function of lipid droplets (LDs). However, the short-wave emission, tedious synthesis process and insufficient specificity have significantly limited the applications of commercially available probes. Herein, we have prepared a novel one-step synthesized near-infrared (NIR) fluorescent probe, TNBD, with a very low emission in aqueous solution and the solid state, but a significantly enhanced fluorescence emission is exhibited in oleic acid. Moreover, TNBD exhibited an impressive lipid droplet (LD) specific fluorescence turn-on ability in cells, fatty liver and atherosclerosis (AS) samples with a good biocompatibility and high signal-to-noise ratio. Our study not only establishes a novel LD turn-on fluorescence probe, but also provides a novel way to prepare a NIR LD targeted fluorescence probe.

Metal–organic frameworks (MOFs) have attracted significant attention as sorbents due to their high surface area, tunable pore volume and pore size, coordinatively unsaturated metal sites, and ability to install desired functional groups by post-synthetic modification. Herein, we report three new MOFs with pillar–paddlewheel structures that have been synthesized solvothermally from the mixture of the carboxylate–pyrazole flexible linker (H2L), 4,4-bipyridine (BPY)/triethylenediamine (DABCO), and Zn(II)/Cu(II) ions. The MOFs obtained, namely [ZnII(L)BPY], [CuII(L)BPY], and [CuII(L)DABCO], exhibit two-fold interpenetration and dinuclear paddle–wheel nodes. The Zn(II)/Cu(II) cations are coordinated by two equatorial L linkers that result in two-dimensional sheets which in turn are pillared by BPY or DABCO in the perpendicular direction to obtain a neutral three-dimensional framework that shows one-dimensional square channels. The three pillar-layered MOFs were characterized as microporous materials showing high crystalline stability after activation at 120 °C and CO2 adsorption. All MOFs contain uncoordinated Lewis basic pyrazole nitrogen atoms in the framework which have an affinity toward CO2 and hence could potentially serve as CO2 adsorption material. The CO2 uptake capacity was initially enhanced by replacing Zn with Cu and then replacing the pillar, going from BPY to DABCO. Overall, all the MOFs exhibit low isosteric heat (Qst) of adsorption which signifies an advantage due to the energy required for the adsorption and regeneration processes.

A novel activity-based Cu2+ fluorescent probe featuring multidentate binding sites was synthesized. It functions through chelation with Cu2+, which in turn specifically triggers hydrolysis of the probe to release a near-infrared emission with AIE + ESIPT properties. The probe was found to be capable of ratiometric imaging of Cu2+ in living HeLa cells.

A turn-on optoacoustic and NIR-II fluorescent probe for imaging antituberculotic drug-induced liver injury has been developed. Probe TC-H2O2 responds to hepatic H2O2, thus releasing chromophore TC-NN, which displays prominent NIR-II fluorescence and optoacoustic signals for diagnosing liver injury.

A new tetrapyrazole-modified tetraphenylethene (TPE) ligand L was designed and found to display “turn-on” fluorescence when it combines with Ag+ ions in dilute solution by restricting intramolecular rotation of TPE. A series of Ag complexes 1–7 were obtained, and they exhibit excellent fluorescence properties in the solid state. Compared with PF6−, the silver complex with the CF3SO3− anion can further enhance its fluorescence due to the transformation of its structure from Ag2L (2) to Ag4L2 (3). As zero-dimensional complexes, 1 and 3 have excellent piezochromic properties with a color change from blue to green. Furthermore, structural changes of 1 and 3 to the corresponding three-dimensional frameworks 4 and 5 occur upon immersing in ethanol. In addition, 1 can act as a potential fluorescent probe for sensing nitrile compounds.

We report a chemiluminescent probe (CLPT1) that permits the paired detection of tyrosinase (Tyr) and biological thiols. Tyr only leads to a poor chemiluminescence response, a finding ascribed to the formation of a stable o-benzoquinone intermediate. The addition of glutathione (GSH), or ascorbate to the o-benzoquinone intermediate results in thiol conjugation or reduction to this intermediate, respectively. This produces a strong chemiluminescence response. Thiol co-dependence was demonstrated in live cells using the cell permeable analogue, CLPT3. The present chemiluminescence-based strategy allows the concurrent detection of tyrosinase activity and biological thiols.

Cyclopenta[d]isoxazoline aminols were used for the synthesis of β-turn mimics. The peptide chain choice ascertained the influence of their structural features on the applicability/reliability/robustness of these scaffolds as β-turn inducers and their limitations. The amino acid selection as well as steric demands can favor or disfavor the structure folding and the correct design of the peptide chains deeply influences the potential use of these nitrosocarbonyl-based compounds as turn-inducers.

A supramolecular dye-capture system comprising anionic amidosquaraine guest and macrocyclic tetralactam host exhibits nanomolar affinity and “turn on” visible fluorescence. Utility is demonstrated with a new fluorescent assay for liposome leakage induced by the biomedically important enzyme phospholipase A(2).

A series of unnatural tripeptides, each consisting of two aromatic γ-amino acid residues and an ϖ-amino acid residue, are designed to probe their folding into hairpin conformations. The ϖ-amino acid residues, with aliphatic or aromatic spacers of different sizes, serve as the loop of the hairpins. Studies based on one-dimensional (1D) 1H NMR performed at different concentrations, solvent polarity, and temperature, along with 2D-NMR studies, demonstrated that the doubly H-bonded aromatic γ-amino acid residues play important roles in driving these tripeptides into the hairpin conformation. The loop based on 5-aminovaleric acid, which offers a four-carbon (CH2)4 spacer, enhanced the stability of the corresponding hairpin, while loops having a shorter, a longer and a more rigid spacer disfavored the formation of the hairpins. Results from computational studies are in good agreement with the experimental observations. Furthermore, the crystal structure of peptide 1b revealed the expected hairpin conformation in the solid state. This turn motif, which contains H-bonded aromatic γ-amino acid residues as the core unit and an ϖ-amino acid residue serving as the loop, provides a new platform that can be used to obtain a variety of turn conformations by incorporating diverse amino acids into the loops.

Four isostructural and isomorphous coordination polymers, {[Zn2(OH)(NO2-1,4-bdc)1.5(Cz-3,6-bpy)]·2H2O}n (1), {[Zn2(OH)(NO2-1,4-bdc)1.5(Cz-Pr-3,6-bpy)]·0.5H2O}n (2), {[Zn2(OH)(Br-1,4-bdc)1.5(Cz-3,6-bpy)]·H2O}n (3), and {[Zn2(OH)(Br-1,4-bdc)1.5(Cz-Pr-3,6-bpy)]·0.5H2O}n (4), where NO2-1,4-bdc = 2-nitrobenzene-1,4-dicarboxylate, Br-1,4-bdc = 2-bromobenzene-1,4-dicarboxylate, Cz-3,6-bpy = 3,6-bis(pyridin-4-yl)-9H-carbazole, and Cz-Pr-3,6-bpy = 3,6-bis(pyridin-4-yl)-9-n-propyl-9H-carbazole, have been hydro(solvo)thermally synthesized. Compounds 1–4 have similar two-dimensional layer structures simplified to rhombus grid-like sql nets in topology. Both nitro-substituted 1 and 2 are fluorescence silent, behaving as visual fluorescence turn-on sensors for the detection of Fe3+, Cr3+, and Al3+ in water. Both bromo-substituted 3 and 4 emit strong cyan fluorescence and can be treated as visually ratiometric fluorescent sensors for the detection of Fe3+, Cr3+, and Al3+ and visual fluorescence turn-off sensors for the detection of CrO42− and Cr2O72− in water, with high selectivity and sensitivity. The work clearly shows that the substituent (nitro and bromo) on the benzene-1,4-dicarboxylate linker has a great impact not only on essential luminescence properties but also the fluorescence responsive performances of coordination polymers.

Nucleobase mismatches can jeopardize DNA polymerization specificity, causing mutations and errors in DNA replication and detection. Herein we report the first synthesis of novel 2-Se-thymidine triphosphate (SeTTP), describe the single-selenium atom-specific modification strategy (SAM) against T/G mismatches, and demonstrate SAM-assisted polymerization and detection with much higher specificity and sensitivity. SAM can effectively suppress the formation of non-specific products in DNA polymerization and detection. Thus, SAM enhances the specificity of DNA synthesis by approximately 10 000 fold, and in turn, it allows the detection of clinical COVID-19 viral RNA in low copy numbers (single-digit copies), while the conventional RT-qPCR does not.

The dimetallic fulvalene-bridged dysprosium complex [{Dy(Cp*)(μ-BH4)}2(Fvtttt)] (1, Cp* = C5Me5) is converted into the trimetallic borohydride-bridged species [{Dy(Cp*)(Fvtttt)}2Dy(μ-BH4)3] (2). In turn, 2 is reacted with a silylium electrophile to give [{Dy(Cp*)(μ-BH4)(Fvtttt)}2Dy][B(C6F5)4] ([3][B(C6F5)3]), the first trimetallic dysprosocenium cation. Compound [3][B(C6F5)3] can also be formed directly from 1 by adding two equivalents of the electrophile. A three-fold enhancement in the effective energy barrier from 2 to 3 is observed and interpreted with the aid of ab initio calculations., The first trimetallic dysprosocenium single-molecule magnet is described. This material signposts a polycationic dysprosium metallocene SMM with properties that could surpass those of leading systems.

A new chelation-controlled hydrofuranization of unactivated olefins with α-alkynyl arylols is reported for the first time, and used to produce a wide range of C3-alkylated benzofurans with generally good yields under mild conditions. A bidentate directing group is used to suppress β-hydride elimination and in turn facilitate a protodepalladation event. In addition to 100% atom utilization, good functional group tolerance and mild conditions, the present catalysis did not demand any additional ligand, additives and bases/acids, making the transformation simple and facile and it thus opens new avenues for catalytic difunctionalization of alkynes and olefins.

Herein we report a multifunctional high performance metal organic framework (Zn-DHNDC MOF) based chemosensor that displays an exceptional excited state intramolecular proton transfer (ESIPT) tuned fluorescence turn-on–off response for OH−, Al3+ and Fe3+ ions along with mitochondria targeted bio-imaging. Properly tuning ESIPT as well as the hydroxyl group (–OH) allows Zn-DHNDC MOF to optimize and establish chelation enhanced fluorescence (CHEF) and chelation enhanced quenching (CHEQ) based sensing mechanisms. The MOF benefits from acid-base interactions with the ions which generate a turn-on bluish green fluorescence (λEm 492 nm) for OH−, an intense turn-on green fluorescence (λEm 528 nm) for Al3+ and a turn-off fluorescence quenching response for Fe3+ ions. The aromatic –OH group indeed plays its part in triggering CHEF and CHEQ processes responsible for the turn-on-off events. Low limits of detection (48 nM of OH−, 95 nM for Al3+, 33 nM for Fe3+ ions), high recyclability and fast response time (8 seconds) further assist the MOF to implement an accurate quantitative sensing strategy for OH−, Al3+ and Fe3+ ions. The study further demonstrates the MOF's behaviour in cellular medium by subjecting it to live cell confocal microscopy. Along with a bio-compatible nature the MOF exhibited successful accumulation inside the mitochondria of MCF7 cancer cells, which defines it as a significant bio-marker. Therefore the present work successfully represents the multidisciplinary nature of Zn-DHNDC MOFs, primarily in sensing and biomedical studies.

Terpyridinium salts of hydracids [PTPH3](Br)3·H2O (1), [PTPH3](Cl)3·2H2O (2) and oxoacid [PTPH3](ClO4)3·H2O (3) (PTP = 4′-(3-pyridyl)-4,2′:6′,4′′-terpyridine) were synthesized and characterized using single crystal X-ray diffraction analyses. The crystallographic analysis reveals that the π+⋯π, π+⋯π+, anion⋯π and anion⋯π+ interactions play a crucial role in the stabilization of the self-assembled structure, which in turn is responsible for enhancing the dimensionality of all the compounds. All the compounds confirm their usefulness as optoelectronic devices owing to the pronounced electrical conductivity and photosensitivity. Experimental and theoretical observations clarify an increase in the electrical conductivity on irradiation compared to dark conditions, especially in 3.

A novel strategy to design "turn-on" fluorescent receptors for G-quadruplexes of DNA is presented, which relies on the connection of phosphate binding macrocycles (PBM) with naphthalimide dyes. A new PBM-dye family was synthesized and evaluated in terms of binding and detection of nucleotides and DNA G-quadruplexes of different topologies.

The endogenous H2S-driven theranostic H2S-Gem has been invented. The theranostic prodrug H2S-Gem is selectively activated in cancer cells, releasing active gemcitabine with a simultaneous fluorescence turn-on. H2S-Gem selectively inhibited cancer cell growth compared to the mother chemotherapeutic gemcitabine. Overall, it is a unique protocol for tracking and transporting chemotherapeutic agents to tumor areas without the guidance of tumor-directive ligands.

The thiol group is known to have a high affinity for gold nanoparticles and is capable of displacing other capping agents. We report a fluorescent indicator displacement technique for the detection of biothiols based on this principle. The displacement of BODIPY from the surface of gold nanoparticles served as a sensitive method for the detection of cysteine, homocysteine, and glutathione under a variety of conditions. It is noteworthy that the turn-ON fluorescence mechanism enabled the differentiation of normal cells from cancer cells because of the inherently higher concentrations of biothiols in the latter.

The structure, energy and spectral properties of neutral end substituted seleno[n]helicenes (n = 1–10) are presented. Equilibrium structures are calculated by applying the B3LYP-D/6-311++G(d,p) method in DCM solvent considering a macroscopic solvent model. Single point energy calculations are also performed at the MP2 level to improve the energy parameters. The study reveals that non-planar structures are preferred for neutral seleno[n]helicenes, n = 3–10, and seleno[8]helicene has a helical structure with one complete turn. Excited state calculations are performed using Time-Dependent Density Functional Theory (TDDFT) to predict UV-visible spectra in DCM solvent. Calculations suggest that the dimerization of an end substituted neutral seleno[7]helicene system is not a favourable process; unsubstituted systems have a fair chance of dimerization though. Similar calculations are extended to radical cations of end substituted seleno[n]helicenes (n = 1–10). Similar to neutral selenohelicene systems, it is predicted that the radical cations of seleno[n]helicenes do prefer a non-planar structure leading to a helical structure for n ≥ 3. In the charged system also one turn of helicality gets completed in the case of the seleno[8]helicene radical cation. Excited state studies suggest that seleno[n]helicene radical cations have strong absorption in the far IR to near IR range. Energy parameters clearly indicate that the dimerization of even the radical cation of the end substituted seleno[7]helicene system is not a favorable process in DCM solvent. The presence of a PF6− counter ion in DCM solvent also does not have much effect on dimerization. Overall, this study explores the effect of charge, size and substitution on the molecular and electronic properties of seleno[n]helicenes in search of Se based suitable materials for applications as near infrared (NIR) electronic devices.

The efficiency of the fluorescence sensitivity of a sensor may be tuned by the modulation of the steric and electronic parameters in the structure. In this study, the thiophenyl Schiff base (E)-N1-(phenyl(pyridin-2-yl)methyl)-N2-(thiophen-2-ylmethylene)benzene-1,2-diamine (HL′) exhibited very high selectivity and a sensitive fluorescence enhancement towards Fe3+ with violet emission (λem, 385 nm; LOD, 3.8 nM). On the other hand, the naphthyl Schiff base (E)-1-(((2-((phenyl(pyridin-2-yl)methyl)amino)phenyl)imino)methyl)naphthalen-2-ol (H2L′′) exhibited fluorescence sensitivity towards Al3+, showing blue emission (λem, 502 nm; LOD, 3.3 nM) in H2O (HEPES buffer, pH 7.4) medium. The emission enhancement of HL′ upon binding to Fe3+ may be considered to be due to the restriction of intramolecular rotation, while the selectivity of H2L′′ towards Al3+ may be due to the turn on emission through the restriction of excited state intramolecular proton transfer (ESIPT) and the introduction of chelation enhanced fluorescence (CHEF). Furthermore, DFT computation supported the sensing strategy and the probes were applied for intracellular detection of Fe3+ and Al3+ in HepG2 cell lines.

Co-based metal organic frameworks (ZIF-67), working as an oxidase-mimicking nanozyme, can simultaneously catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) and Amplex red, exhibiting a high catalytic activity. For Amplex red, two consecutive redox reactions are reported, which is specifically applied for fluorescence "turn-on" detection of biothiols.

The realization of tunable and functionalized MOFs is a winning strategy for CO2 capture. Here we report on a series of robust Fe-MOFs with triangular channels constructed by rod-like fluorinated pyrazolate ligands, comprising an increasing number of fluorine atoms on the central p-phenylene core (F = 1, 2, and 4). This yielded a series of isoreticular frameworks, engineered with orientational flexibility of the fluorinated aryl rings pivoted on ethynyl groups with an sp2–sp soft rotary barrier, providing a stable axel, which supported reorientable C–F dipoles. A combined approach, including powder X-ray diffraction, multinuclear solid-state NMR (2D 1H–13C, 19F, hyperpolarized 129Xe NMR and distance measurements by paramagnetic shift), gas-adsorption and microcalorimetry, enabled the exhaustive description of the fluorinated ring arrangement and the organization of functionalized sites for accommodating CO2. In the tetrafluoro-aryl-derivative MOF, protrusion of perfluorinated rings towards the channel space plays a major role in CO2 capture. Partially fluorinated aryl rings of mono- and di-fluoro MOFs turn to retract into the channel-walls to form continuous ribbons of inter-strut supramolecular interactions, contributing to the robustness of the overall architecture. Detailed computational models obtained using GCMC and DFT of CO2 diffusion and interactions in MOFs showed how the gas molecules approach the channel walls. The highly occupied sites are aligned at the corners of the triangular channels, wherein fluorine atoms participate in host–CO2 interactions. A CO2–matrix adsorption enthalpy of 33 kJ mol−1, suitable for capture/delivery cycles, was accurately measured in situ by simultaneous acquisition of microcalorimetric and volumetric-isotherm data. Thus, the designed advantages of rotationally flexible fluorinated moieties were successfully explored.

Unlike the O2 neighboring group participation in glycosylation, the participating effect of esters located on more remote positions of glycopyranosyl donors has not been unambiguously established and provokes plenty of questions. Here we systematically trapped the participation intermediates on three common pyranoses based on a ‘bis-trichloroacetimidates method’, which showed that trichloroacetimidate group participations from O4 and O6 are all quite possible except for D-mannopyranosyl O4. Besides, with the trapped participation intermediates in hand, the NMR data was collected to assist the DFT calculations to build up the most possible participating conformations, which, in turn, predicted the potentials of remote participation by trichloroacetimidates at different positions on the same donor. Finally, the ‘tris-trichloroacetimidates method’ was employed to support the computational calculations. This work provided a conformational perspective on understanding the potent remote acyl group participation in glycosylation reaction.

WOS:000542111600035 PubMed ID: 32427230 A near-infrared ratiometric fluorescent probe CR-Ac based on a coumarin-benzopyrylium platform has been developed for selective detection of Cu2+. The cell imaging data revealed the capabilities of CR-Ac in monitoring the dynamic changes of subcellular Cu2+ and the quantification of Cu2+ levels in living cells. We thank the National Science Foundation (CHE-1213838 and CHE-1229339) and NIH (1R15GM126576-01) for funding.

We have developed a propargylamine-selective dual fluorescence turn-on system, using ylidenemalononitrile enamines, for post-synthetic DNA labeling, allowing the direct and accurate monitoring of DNA using dual emission in living cells.

A new, simple and easy-to-manufacture highly selective and sensitive dual-mode sensor A1, is used for CN− colorimetric and fluorescence detection. Interestingly, the solid powder of sensor A1 emits a strong green fluorescence, and has aggregation-induced emission properties. Single crystal diffraction analysis results prove that the generation of AIE properties is based on the J-aggregation mechanism. Simultaneously, A1 showed high selectivity and sensitivity to CN− in many interfering anions. The sensing mechanism of cyanide is carried out by deprotonation of the –OH group by the cyanide ion, and has been confirmed by spectroscopic studies, 1H NMR spectroscopy, Job's plot analyses and DFT calculation. The practicality of the sensor has been well proven by filter paper strips and small molecule smart fluorescent display materials. In addition, the sensor is used to detect cyanide in food materials (such as germinated potatoes, cassava and bitter almonds) with satisfactory results. The most important thing is considering the colorimetric and fluorescent dual modes, the ultra-fast response, excellent selectivity and recyclability that demonstrate its excellent value in practical applications.

Herein, we have presented a phenyl thiadiazole-based Schiff base receptor, 2-[(Z)-(5-phenyl-1,3,4-thiadiazol-2-ylimino)methyl]-6-methoxy-4-nitrophenol (L) for the first time for turn-on fluorescent, colourimetric detection of Al3+ ions. The chemosensor L displayed very quick responses, excellent selectivity and sensitivity towards Al3+ ions in methanol–Tris–HCl buffer medium (10 mM, pH 7.2, and 1 : 1 v/v) with colourimetric and fluorometric detection limit values of 1.43 × 10−7 M and 1.15 × 10−7 M, respectively. The binding stoichiometry was obtained as 2 : 1 from the Job plot analysis and ESI-MS spectra with the association constant value of 1.76 × 102 M−1/2. The experimental results have further been supported by thorough DFT and TD-DFT studies. The chemosensor L can be applied for the formation of binary logical devices, recovery of contaminated water samples and smartphone-based chemical analysis.

Currently, fluorescent sensors for the detection of H2O in D2O are still quite rare. Herein, we present a dual-site controlled fluorescent sensor (CF-D2O) for the detection of H2O in D2O. As the H2O content in D2O decreases (namely, the purity of D2O increases), sensor CF-D2O provides two turn-on fluorescence signals. The response mechanism of sensor CF-D2O to H2O is based on the deprotonation of the two hydroxyl groups, as well as the FRET process between coumarin and xanthene units.

A novel hemicyanine-based fluorescent probe was developed for the fast, selective, and reversible detection of Cu2+ ions with "turn-on" fluorescence response in the aqueous solution. The sensing mode was demonstrated through fluorescence, UV-vis, HRMS, 1H NMR, and DFT calculations. The probe was successfully used for the imaging of Cu2+ ions in living cells.

Using an exciton as a carrier was examined as a possible solution to the problem of signal transmission between molecular logic gates. A tetrathiafulvalene chain was chosen as a model for a molecular logic system and its distinct logic states were described as excitons located at certain tetrathiafulvalene units. The parameters of the exciton transfer between the units of the chain were studied. The transfer rate between the two adjacent units was calculated using the Plotnikov-Bixon-Jortner theory basing on molecular parameters calculated using TD-DFT. The order of electronic states was studied at the MCQDPT and TD-DFT levels of theory. It was found that certain functional groups in the chain can make exciton transfer faster than its recombination. The exciton can effectively carry a signal through the chain, which in turn can be enlarged and modified.

A highly selective and sensitive nanoprobe with fluorescence turn-on sensing properties for recognizing Cd2+ was developed through replacing Mn2+ near the surface of Mn:ZnSe quantum dots (QDs). The similar ionic radii of Cd2+ and Zn2+ make the replacement of superficial Zn2+ by Cd2+ possible, followed by the replacement of external Mn2+ by Cd2+. Thus, this fluorescence turn-on strategy possesses great selectivity for the determination of Cd2+. Based on this strategy, the limit of detection (LOD) for Cd2+ is 18 nM, which is superior to the LOD of most reported fluorescent nanomaterial-based probes.

The reaction between aryl substituted sodium 1,2,3-triphospholides or disodium bis(1,2,3-triphospholide) and [Fe(η6-(C6H5CH3)Cp]+[PF6]- in boiling diglyme results in pure 1,2,3-triphosphaferrocenes 1-3 or bis(1,2,3-triphosphaferrocene) 4, respectively, in good yields. The structure of all obtained 1,2,3-triphosphaferrocenes 1-4 has been extensively studied experimentally (NMR, UV-Vis spectroscopy, and X-ray analysis for 1 and 4) and quantum chemically. The electrochemical properties of 1,2,3-triphosphaferrocenes 1-4 in the solid state were studied for the first time and a reversible one-electron oxidation (E1/2 = 0.52-0.92 V vs. Fc+/Fc) was demonstrated for 1, 3, and 4. In the case of 1,4-bis(5-phenyl-4-(1,2,3-triphospaferrocenyl))benzene 4, consecutive oxidation in the solid state is observed in contrast to other 1,2,3-triphosphaferrocenes 1-3. According to the ESR data, the g-factor of the oxidized bis(1,2,3-triphosphaferrocene), 4 (g = 2.12) is different from the g-factors of oxidized 1,2,3-triphosphaferrocenes 1-3 (g = 2.01). This is the first example of multi(ferrocenyl) systems based on the phosphaferrocene motif, which in turn opens up a new fundamental platform for the preparation of compounds with stimuli-responsive properties.

In this work, were synthesized for the first time a series of new lipophilic β-alkyl substituted GABA derivatives from fatty alkyl chains. The synthesis of these GABA analogues was investigated by two different bicomponent approaches as a key step. The results showed low yields in the path from aliphatic nitroolefins and Meldrum's acid, whereas the Knoevenagel condensation between aliphatic aldehydes and Meldrum's acid afforded fatty alkylidenes in good yields (75–97%). These compounds were subsequently subjected to a conjugate addition reaction with nitromethane, resulting in the fatty Michael adducts (in 87–97% yields) which were in turn submitted to a one pot domino hydrolysis-decarboxylation, leading to the isolation of β-alkyl-substituted γ-nitro acids in good yields (78–92%). Finally, the reduction of the fatty γ-nitro acids allowed for the access to new lipophilic β-alkyl substituted GABA analogues, which were isolated in high yields (90–98%). The new methodology was also applied to the synthesis of antiepileptic drug (+/−)-Pregabalin, which was obtained after four steps in high overall yield.

The homoleptic homodinuclear nickel carbonyl anions Ni2(CO)n- (n = 4-6) are mass-selected in the gas phase and examined with anion photoelectron velocity-map imaging spectroscopy combined with density functional calculations. The doubly carbonyl-bridged structures are found to be favorable for Ni2(CO)n- (n = 4-6). The nature of Ni-Ni bonding in these complexes is analysed with the aid of a range of state-of-the-art quantum chemistry methods. Despite the absence of direct multiple Ni-Ni bonds, the two nickel atoms in Ni2(CO)n- (n = 4-6) complexes are joined by two bridging carbonyl ligands via the sharing three-center two-electron Ni-C-Ni bond in turn to achieve the (16,16), (16,18), and eventually the favored (18,18) configurations.

Sensor materials that undergo a change in fluorescence behaviour upon binding with cations and anions are one of the most widely used analytical tools and they can be used for various molecular switches and logic gates. Here, we have designed a photolabile chemosensor for both anions and cations by using a simple acyclic molecule, diformyl diaryldipyrromethane, and integrated it as a molecular keypad lock system. The molecular keypad lock works with respect to three inputs, with UV irradiation as input 1, where diformyl diaryldipyrromethane undergoes a photoenolization process to generate the dienol with intense green fluorescence. Further, the addition of anions such as F− or CN− (input 2) promotes deprotonation to yield the corresponding mono and dianions followed by emission changes from green to red and yellow, respectively. The generated dianions can effectively complex with Zn2+ ions to result in “turn on” fluorescence at 444 nm (yellow to blue) and thus Zn2+ ions are used as input 3. The output signal (λem = 444 nm) depends not only on the proper combination but also on the correct sequence of input signals, i.e., UV, F− (or CN−) and finally Zn2+ ions, mimicking a keypad.

Water-soluble cationic and anionic oligofluorenes bearing N1-alkylcytosine side chains, namely OF-1 and OF-2, were synthesized. The photoluminescence (PL) intensity of an aqueous solution of OF-1 decreased on the addition of (TTAGGG)m as telomere DNA models. In contrast, the PL intensity of OF-2 increased on the addition of DNA.

Excess iron ions are harmful to human health; therefore, it is essential to develop efficient methods to detect Fe3+. Herein, a new aggregation-induced emission (AIE) ligand (L), 4,4′-((9H-fluoren-9-ylidene)-methylene)dipyridine, was successfully synthesized and applied to construct a luminescent Cd(II)–organic framework [Cd(NDA)(L)(H2O)2]n (1) with a two-dimensional architecture (H2NDA = 1,4-naphthalenedicarboxylic acid). Specially, 1 possesses good water stability and exhibits superior luminescence enhancement (“turn-on”) sensing of Fe3+ with high sensitivity and selectivity in a water suspension. This represents the first example of a LMOF-based “turn-on” Fe3+ sensor in aqueous medium.