Electrogenerated Chemiluminescent Anion Sensing: Selective Recognition and Sensing of Pyrophosphate

Selective pyrophosphate detection via metal complexes

Pyrophosphate (PPi) anions are crucial in numerous biological and ecological processes involved in energy conversion, enzymatic reactions, and metabolic regulation along with adenosine. They are also significant biological markers for various processes related to diseases. Fluorescent PPi sensors would enable visual and/or biological detection in convenient settings. However, the current availability of commercial sensors has been limited to costly enzymes that are not compatible for imaging. Sensor development has also encountered challenges such as poor selectivity and stability, and limited practical applications. In this review, we analyze the situation of PPi sensing via commercial kits and focus on sensors that use metal complexes. We address their designs, sensing mechanisms, selectivities and detection limits. Finally, we discuss limitations and perspectives for PPi detection and imaging.

A photoluminescent and electrochemiluminescent probe based on an iridium(III) complex with a boronic acid-functionalised ancillary ligand for the selective detection of mercury(II) ions

Exposure to mercury(II) ions (Hg2+) can cause various diseases such as Minamata disease, acrodynia, Alzheimer's disease, and Hunter-Russell syndrome, and even organ damage. Therefore, real-time and accurate monitoring of Hg2+ in environmental samples is crucial. In this study, we report a photoluminescent (PL) and electrochemiluminescent (ECL) probe based on a cyclometalated Ir(III) complex for the selective detection of Hg2+. The introduction of a reaction site, o-aminomethylphenylboronic acid, on the ancillary ligands allowed a prompt transmetalation reaction to take place between Hg2+ and boronic acid. This reaction resulted in significant decreases of the PL and ECL signals due to the photo-induced electron transfer from the Ir(III) complex to the Hg2+ ions. The probe was applied to the selective detection of Hg2+, and the signal changes revealed a linear correlation with Hg2+ concentrations in the range of 0-10 μM (LOD = 0.72 μM for PL, 8.03 nM for ECL). The designed probe allowed the successful quantification of Hg2+ in tap water samples, which proves its potential for the selective detection of Hg2+ in environmental samples.

A novel AIE-active imidazolium macrocyclic ratiometric fluorescence sensor for pyrophosphate anion

An imidazolium bridged macrocyclophane was synthesized as a ratiometric fluorescence sensor with aggregation-induced emission (AIE) characteristic to detect pyrophosphate anion with high selectivity among various anions. In the presence of zinc ion, macrocyclophane can form aggregates through complexation with pyrophosphate anion and emit ratiometric fluorescence, resulting from an enhancement in its aggregate-state emission and a reduction in its monomer emission. This AIE-active macrocycle showed great potential as a ratiometric fluorescence receptor.

Efficient synthesis of 6,6′-diamido-2,2′-dipicolylamine ligands for potential phosphate anion sensing

Through retrosynthetic analysis, functionalized 6,6′-diamido-2,2′-dipicolylamines (DA-DPAs) have been efficiently synthesized, which may accelerate the development of selective probes towards phosphate anions.

Electrochemiluminescent detection of glucose in human serum by BODIPY-based chemodosimeters for hydrogen peroxide using accelerated self-immolation of boronates

BODIPY-based ECL chemodosimeters were developed for the detection of hydrogen peroxide. The reactivity of boronate towards hydrogen peroxide was enhanced by adjacent fluorine atoms. In combination with glucose oxidase, a fluorine-substituted probe successfully quantified the glucose level in human serum, providing its potential as a versatile tool in point-of-care testing applications.

The Power of Assemblies at Interfaces: Nanosensor Platforms Based on Synthetic Receptor Membranes

Synthetic sensing materials (artificial receptors) are some of the most attractive components of chemical/biosensors because of their long-term stability and low cost of production. However, the strategy for the practical design of these materials toward specific molecular recognition in water is not established yet. For the construction of artificial material-based chemical/biosensors, the bottom-up assembly of these materials is one of the effective methods. This is because the driving forces of molecular recognition on the receptors could be enhanced by the integration of such kinds of materials at the 'interfaces', such as the boundary portion between the liquid and solid phases. Additionally, the molecular assembly of such self-assembled monolayers (SAMs) can easily be installed in transducer devices. Thus, we believe that nanosensor platforms that consist of synthetic receptor membranes on the transducer surfaces can be applied to powerful tools for high-throughput analyses of the required targets. In this review, we briefly summarize a comprehensive overview that includes the preparation techniques for molecular assemblies, the characterization methods of the interfaces, and a few examples of receptor assembly-based chemical/biosensing platforms on each transduction mechanism.

Ditopic binuclear copper(II) complexes for DNA cleavage

Herein we present the synthesis of two ligands containing two di(2-picolyl)amine (DPA) units linked by either a 1,1'-(pyridine-2,6-diyl)bis(3-ethylurea) (L1) or a 1,1'-(1,3-phenylene)bis(3-ethylurea) (L2) spacer. The corresponding binuclear Cu^II and Zn^II complexes were prepared and isolated. The X-ray structures of the L1 ligand and the [Cu₂L1Cl₂]²⁺ complex evidence an unusual cis/trans conformation of one of the urea groups stabilized by an intramolecular hydrogen bond with the nitrogen atom of the pyridyl spacer. The Cu^II complexes form rather strong ternary complexes with phosphorylated anions. The [Cu₂L1]⁴⁺ complex presents a rather high affinity for pyrophosphate (logK₁₁ = 8.19 at pH 7, 25 °C), while [Cu₂L2]⁴⁺ stands out because of its strong binding to AMP^2- (logK₁₁ = 9.3 at pH 7, 25 °C). The interaction of the Cu^II complexes with deoxyribonucleic acid from calf thymus (ct-DNA) was monitored using circular dichroism (CD) and luminescence spectroscopies. These studies revealed a quite strong interaction of the complexes with ct-DNA (K_b = (6.4 ± 0.7) × 10³ for [Cu₂L1]⁴⁺ and K_b = (6.3 ± 1.0) × 10³ for [Cu₂L2]⁴⁺). Competition experiments carried out in the presence of methyl green and BAPPA (N¹,N³-Bis(4-amidinophenyl)propane-1,3-diamine) as major and minor groove competitors, respectively, confirm that the interaction of both complexes with DNA takes place through the minor groove, in agreement with docking studies. The [Cu₂L2]⁴⁺ complex is quite efficient in promoting the cleavage of the double-stranded pUC19 plasmid DNA, by favoring the conversion of the supercoiled form to the nicked form following a hydrolytic mechanism.

Conformational Re-engineering of Porphyrins as Receptors with Switchable N-H⋅⋅⋅X-Type Binding Modes

The selectivity and functional variability of porphyrin cofactors are typically based on substrate binding of metalloporphyrins wherein the pyrrole nitrogen units only serve to chelate the metal ions. Yet, using the porphyrin inner core system for other functions is possible through conformational engineering. As a first step towards porphyrin “enzyme‐like” active centers, a structural and spectroscopic study of substrate binding to the inner core porphyrin system shows that a highly saddle‐distorted porphyrin with peripheral amino receptor groups (1, 2,3,7,8,12,13,17,18‐octaethyl‐5,10,15,20‐tetrakis(2‐aminophenyl)porphyrin) coordinates analytes in a switchable manner dependent on the acidity of the solution. The supramolecular ensemble exhibits exceptionally high affinity to and selectivity for the pyrophosphate anion (2.26±0.021)×10⁹  m⁻¹. ¹H NMR spectroscopic studies provided insight into the likely mode of binding and the characterization of atropisomers, all four of which were also studied by X‐ray crystallography.

Electrogenerated chemiluminescence aptasensor for lysozyme based on copolymer nanospheres encapsulated black phosphorus quantum dots

Black phosphorus quantum dots (BPQDs) can react with Ru(bpy)₃²⁺ to generate strong anodic electrogenerated chemiluminescence (ECL). However, the instability and the lack of functional groups on BPQDs limit its further application in the fabrication of ECL biosensor. In the present work, uniform BPQDs-styrene-acrylamide (St-AAm) nanospheres (BSAN) are synthesized by encapsulating BPQDs into St-AAm copolymer nanospheres. Sufficient amount of BPQDs can be embedded into nanospheres, and react with Ru(bpy)₃²⁺ to generate strong anodic ECL which is comparable to that of pure BPQDs. Amino group of polymer endows BPQDs the ability to connect with DNA, and can be used to fabricate ECL aptasensor for the sensitive detection of lysozyme. The proposed aptasensor shows high sensitivity, good selectivity and stability for the detection of lysozyme in the range of 0.1-100 pg mL^-1 with a detection limit of 0.029 pg mL^-1 (3σ). The proposed method reveals the promising ECL sensing application of BP nanomaterials in the detection of various proteins.

Spectrophotometric, fluorimetric and electrochemical selective pyrophosphate/ATP sensing based on the dimethyltin(IV)-tiron system

Sensing of pyrophosphate anion (PPi) in the presence of nucleotide triphosphates allows the real time monitoring of the polymerase chain reaction. To get a deeper understanding of the factors involved in PPi/nucleotide triphosphate discrimination, a detailed study on the performance of a dimethyltin (IV)-catecholate complex capable of both separate fluorimetric or electrochemical detection of PPi in the presence of adenosine triphosphate (ATP) has been undertaken. Dimethyltin (IV) tightly binds PPi or ATP, and forms a stable 1:1 complex with tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid) in water. The complexation equilibria with all components are characterized quantitatively by potentiometric and spectroscopic titrations. Pyrophosphate anion can be detected owing to its ability to release free tiron from the complex by measuring either a fluorimetric or an electrochemical signal. On the contrary, ATP does not displace tiron but causes an interference with PPi in the fluorimetric detection method due to the formation of a ternary Me₂Sn(IV)-tiron-ATP complex with optical properties intermediate between those of free and bound tiron. In the electrochemical (square wave voltammetry) method, the ternary ATP complex shows a separate peak which does not coincide with the peaks of neither free nor bound tiron, thus making possible the simultaneous detection of ATP in addition to PPi.

An AIE-based metallo-supramolecular assembly enabling an indicator displacement assay inside living cells

We report a novel metallo-supramolecular assembly (Z/E-TPE2CyZn-PV), which consists of a tetraphenylethene (TPE)-based dinuclear Zn2+-cyclen complex and pyrocatechol violet (PV). The assembly is developed for indicator-displacement assays (IDAs) inside living cells.

Color-Coded Single-Particle Pyrophosphate Assay with Dark-Field Optical Microscopy

In this work, we demonstrate a convenient yet sensitive color-coded single-particle detection method for the quantification of pyrophosphate (PPi) by using single gold nanoparticle (GNP) as the probe. The design is based on GNP-dependent catalytic deposition of Cu onto the surface of GNPs with reduced nicotinamide adenine dinucleotide (NADH). Without PPi, Cu²⁺ can be directly reduced to Cu⁰ through the gold-catalyzed oxidization of NADH. In the presence of PPi, the coating process is impeded due to the strong coordination capability of PPi with Cu²⁺. The selective coating of Cu shell onto the GNPs surface results in the extraordinary red-shift of localized surface plasmon resonance from individual GNPs. By quantitatively counting the fraction of yellow particles with color-coded dark-field optical microscopy, the trace amounts of PPi in solution can be accurately quantified. The limit-of-detection is as low as 1.49 nM with a linear dynamic range of 0-4.29 μM, which is much lower than the spectroscopic measurements in bulk solution. In artificial urine sample, good recovery efficiency was achieved. As a consequence, the method demonstrated herein will find promising applications for the ultrasensitive detection of target biomolecules under biological milieu in the future.

Design and Synthesis of Pyrophosphate-Targeting Vancomycin Derivatives for Combating Vancomycin-Resistant Enterococci

As the last resort for intractable Gram-positive bacterial infections, vancomycin is losing efficacy with the emergence of vancomycin-resistant bacteria, especially vancomycin-resistant Enterococci (VRE). To combat this threat, we rationally designed and synthesized 39 novel vancomycin derivatives by respective or combined modifications using metal-chelating, lipophilic, and galactose-attachment strategies for extensive structure-activity relationship (SAR) analysis. In a proposed mechanism, the conjugation of dipicolylamine on the seventh amino acid resorcinol position or C-terminus endowed the vancomycin backbone with binding capacity for the pyrophosphate moiety in lipid II while maintaining the intrinsic binding affinity for the dipeptide terminus of the bacterial cell wall peptidoglycan precursor. The in vitro antibacterial activities were evaluated, and the optimal compounds indicated 16- to 1024-fold higher activity against VRE than that of vancomycin. Compound 11 b (3',5'-bis(dipicolylaminomethyl)tyrosine [1,2,3]triazolylmethoxylethyoxyl ethylaminomethyl-N-decylvancomycin) was found to have particularly potent activity against VRE through synergistic effects brought about by combining two peripheral modifications.

Pyrophosphate-Induced Intramolecular Excimer Formation in Dinuclear Zinc(II) Complexes with Tetrakisquinoline Ligands

Dinuclear Zn²⁺ complexes with HTQHPN ( N,N,N' ,N'-tetrakis(2-quinolylmethyl)-2-hydroxy-1,3-propanediamine) derivatives have been prepared, and their pyrophosphate (PPi, P₂O₇^4-) sensing properties were examined. The ligand library includes six HTQHPN derivatives with electron-donating/withdrawing substituents, an extended aromatic ring, and six-membered chelates upon zinc binding. Complexation of ligand with 2 equiv of Zn²⁺ promotes small to moderate fluorescence enhancement around 380 nm, but in the cases of HTQHPN, HT(6-FQ)HPN ( N,N,N' ,N'-tetrakis(6-fluoro-2-quinolylmethyl)-2-hydroxy-1,3-propanediamine), and HT(8Q)HPN ( N,N,N' ,N'-tetrakis(8-quinolylmethyl)-2-hydroxy-1,3-propanediamine), subsequent addition of PPi induced a significant fluorescence increase around 450 nm. This fluorescence enhancement in the long-wavelength region is attributed to the conformational change of the bis-(quinolylmethyl)amine moiety which promotes intramolecular excimer formation between adjacent quinolines upon binding with PPi. The structures of PPi- and phosphate-bound dizinc complexes were revealed by X-ray crystallography utilizing phenyl-substituted analogues. The zinc complex with HT(8Q)HPN exhibits the highest signal enhancement ( I_PPi/ I₀ = 12.5) and selectivity toward PPi sensing ( I_ATP/ I_PPi = 20% and I_ADP/ I_PPi = 25%). The fluorescence enhancement turned to decrease gradually after the addition of more than 1 equiv of PPi due to the removal of zinc ion from the ligand-zinc-PPi ternary complex, allowing the accurate determination of PPi concentrations at the fluorescence maximum composition. The practical application of the present method was demonstrated monitoring the enzymatic activity of pyrophosphatase.

Recognition of AMP, ADP and ATP through Cooperative Binding by Cu(II) and Zn(II) Complexes Containing Urea and/or Phenylboronic-Acid Moieties

We report a series of Cu(II) and Zn(II) complexes with different ligands containing a dipicolyl unit functionalized with urea groups that may contain or not a phenylboronic acid function. These complexes were designed for the recognition of phosphorylated anions through coordination to the metal ion reinforced by hydrogen bonds involving the anion and NH groups of urea. The complexes were isolated and several adducts with pyrophosphate were characterized using X-ray diffraction measurements. Coordination of one of the urea nitrogen atoms to the metal ion promoted the hydrolysis of the ligands containing 1,3-diphenylurea units, while ligands bearing 1-ethyl-3-phenylurea groups did not hydrolyze significantly at room temperature. Spectrophotometric titrations, combined with ¹H and ³¹P NMR studies, were used in investigating the binding of phosphate, pyrophosphate (PPi), and nucleoside 5′-polyphosphates (AMP, ADP, ATP, CMP, and UMP). The association constants determined in aqueous solution (pH 7.0, 0.1 M MOPS) point to a stronger association with PPi, ADP, and ATP as compared with the anions containing a single phosphate unit. The [CuL⁴]²⁺ complex shows important selectivity for pyrophosphate (PPi) over ADP and ATP.

Quinoline containing acetyl hydrazone: An easily accessible switch-on optical chemosensor for Zn2

A simple chemosensor, namely, N-((quinolin-8-yl)methylene)acetohydrazide (1) was synthesized and used as an off-on fluorescence sensor, which exhibits high selectivity toward Zn²⁺ in aqueous media. The probe has large Stokes shift of >200nm, and its detection limit for Zn²⁺ is 89.3nM. The binding process was confirmed through UV-vis absorption analysis, fluorescence measurements, mass spectroscopy study, ¹H NMR spectra and density functional theory calculation. The crystal structures of Zn²⁺, Ni²⁺, and Cu²⁺ complexes based on 1 were determined through X-ray crystallographic analysis. The fluorescent probe was then applied to monitor intracellular Zn²⁺ in HeLa cells.

Selective detection of pyrophosphate anion by a simple Cd(II) based terpyridine complex

A simple ratiometric terpyridine-Cd(ll) complex was synthesized by the treatment of CdCl₂ with terpyridine ligand 4'-(4-N,N'-dimethylaminophenyl)-2,2':6',2″-terpyridine. The synthesized complex was found to act as a selective fluorescent chemosensor for pyrophosphate P₂O₇^4- (PPi) over other anions like F^-, Cl^-, Br^-, CO₃^2-, SO₃^2-, AcO^-, NO₂^-, and H₂PO₄^-. Furthermore, the receptor probe was also successfully employed in HeLa cell for PPi detection, which indicates this can be used as a chemosensor for cells.

A novel glucosamine-linked fluorescent chemosensor for the detection of pyrophosphate in an aqueous medium and live cells

A glucosamine-linked Cu²⁺ ensemble has been successfully developed for detection of pyrophosphate (PPi) in aqueous medium and in live MD-AMB-231 cells.

Electrogenerated chemiluminescence of Ru(bpy)32+at a black phosphorus quantum dot modified electrode and its sensing application

Strong anodic electrogenerated chemiluminescence (ECL) of Ru(bpy)₃²⁺can be obtained under neutral conditions at a black phosphorus quantum dot (BPQD) modified electrode due to the catalytic effect of BPQDs. Dopamine exhibits an apparent inhibiting effect on the ECL signal, and as a result, can be sensitively detected.

High-affinity and selective detection of pyrophosphate in water by a resorcinarene salt receptor

Pyrophosphate (PPi) is a byproduct of DNA and RNA synthesis, and abnormal levels are indicative of disease. We report the high-affinity binding of PPi in water by N-alkyl ammonium resorcinarene chloride receptors. Experimental analysis using ¹H and ³¹P NMR, isothermal titration calorimetry, mass spectrometry, and UV-vis spectroscopy all support exceptional selectivity of these systems for PPi in water. The measured affinity of K₁ = 1.60 × 10⁷ M^-1 for PPi is three orders of magnitude larger than that observed for binding to another phosphate, ATP. This exceptional anion-binding affinity in water is explored through a detailed density functional theory computational study. These systems provide a promising avenue for the development of future innovative medical diagnostic tools.

Electrogenerated Chemiluminescence Resonance Energy Transfer between Ru(bpy)3(2+) Electrogenerated Chemiluminescence and Gold Nanoparticles/Graphene Oxide Nanocomposites with Graphene Oxide as Coreactant and Its Sensing Application

In the present work, strong anodic electrogenerated chemiluminescence (ECL) of Ru(bpy)3(2+) was observed at a graphene oxide modified glassy carbon electrode (GO/GCE) in the absence of coreactants. The electrocatalytical effect of GO on the oxidation of Ru(bpy)3(2+) suggested that GO itself can act as the coreactant of Ru(bpy)3(2+) ECL, which can be used to fabricate the ECL biosensor. Thiol group terminated adenosine triphosphate (ATP) aptamer was immobilized on the GO film via DNA hybridization. When gold nanoparticles/graphene oxide (AuNPs/GO) nanocomposites were modified on the aptamer through the S-Au bond to form a sandwich-like structure, the ECL resonance energy transfer (ECL-RET) could occur between Ru(bpy)3(2+) and AuNPs/GO nanocomposites, resulting in an apparent decrease of ECL signal. After the ECL sensor was incubated in ATP solution, the AuNPs/GO nanocomposites were released from the electrode due to the specific interaction between aptamer and ATP, leading to the increased ECL signal. On the basis of these results, an ECL aptasensor was fabricated and could be used in the sensitive and selective detection of ATP in the range of 0.02-200 pM with a detection limit of 6.7 fM (S/N = 3). The proposed ECL aptasensor can be applied in the detection of ATP in real samples with satisfactory results.

A sensitive electrogenerated chemiluminescence biosensor for galactosyltransferase activity analysis based on a graphitic carbon nitride nanosheet interface and polystyrene microsphere-enhanced responses

An electrogenerated chemiluminescence biosensor for galactosyltransferases activity analysis was developed based on g-C₃N₄ nanosheet interface and polystyrene microsphere enhanced responses.

One-pot synthesis of highly greenish-yellow fluorescent nitrogen-doped graphene quantum dots for pyrophosphate sensing via competitive coordination with Eu(3+) ions

Highly fluorescent nitrogen-doped graphene quantum dots (N-GQDs) with greenish-yellow emission and quantum yield of 13.2% have been synthesized via a one-pot hydrothermal method. The obtained N-GQDs displayed excellent optical properties, high photostability and resistance to strong ion strength. Based on the higher affinity of pyrophosphate (PPi) than carboxyl and amido groups on the surface of the N-GQDs to Eu(3+), a Eu(3+)-modulated N-GQD off-on fluorescent probe for PPi detection was constructed with a detection limit of 0.074 μM. The detection process was simple in design, easy to operate, and showed a highly selective response to PPi in the presence of co-existing anions. This work widens the applications of N-GQDs with versatile functionality and reactivity in clinical diagnostics and as biosensors.

Nanomolar Zn(ii) sensing and subsequent PPi detection in physiological medium and live cells with a benzothiazole functionalized chemosensor

Nanomolar zinc detection and subsequent pyrophosphate sensing in physiological media using a benzothiazole modified conjugated ligand and their application in paper strip and live cell imaging is demonstrated.

Tetraphenylethylene imidazolium macrocycle: synthesis and selective fluorescence turn-on sensing of pyrophosphate anions

A novel tetraphenylethylene imidazolium macrocycle was found to be able to form an aggregate with a pyrophosphate anion in water, which gives a characteristic aggregation-induced emission fluorescence.

Biothiols as chelators for preparation of N-(aminobutyl)-N-(ethylisoluminol)/Cu(2+) complexes bifunctionalized gold nanoparticles and sensitive sensing of pyrophosphate ion

In this work, chemiluminescence (CL) reagent and catalyst metal ion complexes bifunctionalized gold nanoparticles (BF-AuNPs) with high CL efficiency were synthesized via an improved synthesis strategy. Biothiols, such as cysteine (Cys), cysteinyl-glycine (Cys-Gly), homocysteine (Hcy), and glutathione (GSH), instead of 2-[bis[2-[carboxymethyl-[2-oxo-2-(2-sulfanylethylamino)ethyl]amino]ethyl]amino]acetic acid (DTDTPA), were used as new chelators. N-(aminobutyl)-N-(ethylisoluminol) (ABEI) was used as a model of CL reagents and Cu(2+) as a model of metal ion. In this strategy, biothiols were first grafted on the surface of ABEI-AuNPs by Au-S bond. Then, Cu(2+) was captured onto the surface of ABEI-AuNPs by the coordination reaction to form BF-AuNPs. The CL intensity of Cu(2+)-Cys/ABEI-AuNPs was 1 order of magnitude higher than that of DTDTPA/Cu(2+)-ABEI-AuNPs synthesized by the previous work. Moreover, strong CL emission of Cu(2+)-Cys/ABEI-AuNPs was also observed in neutral pH conditions. In addition, the present BF-AuNPs synthesis method exhibited advantages over the previous method in CL efficiency, simplicity, and synthetic rate. Finally, by virtue of Cu(2+)-Cys/ABEI-AuNPs as a platform, a simple CL chemosensor for the sensitive and selective detection of pyrophosphate ion (PPi) was established based on the competitive coordination interactions of Cu(2+) between Cys and PPi. The method exhibited a wide detection range from 10 nM to 100 μM, with a low detection limit of 3.6 nM. The chemosensor was successfully applied to the detection of PPi in human plasma samples. It is of great application potential in clinical analysis. This work reveals that BF-AuNPs could be used as ideal nanointerface for the development of novel analytical methods.

A Benzothiazole-Based Sensor for Pyrophosphate (PPi) and ATP: Mechanistic Insight for Anion-Induced ESIPT Turn-On

A benzothiazole derivative 2 bearing two 2,2'-dipicolylamine (DPA) groups was examined for its zinc-binding and subsequent anion sensing properties. The study revealed the anion sensing mechanism of polyphosphate anions via sequential binding to two zinc centers, on the basis of both 1H NMR and mass spectral evidences. The mechanistic insight would provide valuable information for the future design of new excited state intramolecular proton transfer (ESIPT) sensors. In addition, the zinc complex exhibited the solvent-switchible selectivity, responding to pyrophosphate (PPi) in EtOH but adenosine 5'-triphosphate (ATP) in water.

A binuclear Zn(II)-Zn(II) complex from a 2-hydroxybenzohydrazide-derived Schiff base for selective detection of pyrophosphate

A hydroxybenzohydrazide-based Schiff base ligand was conveniently synthesized. Upon addition of Zn(2+) cations, the ligand exhibited a high tendency to form a binuclear structure with a 2 : 2 ligand-to-zinc ratio, which was accompanied by a large fluorescence turn-on (λem = 507 nm, ϕfl≈ 0.28). The reactivity of the zinc complex was examined using different phosphate anions, which reveals a higher response to acid pyrophosphate anions. Detailed spectroscopic studies show that the pyrophosphate response is based on the ligand displacement mechanism.

Ratiometric fluorescence recognition for pyrophosphate on the basis of terpyridine derivative

Diphosphate (pyrophosphate, PPi) is vital for organisms, and therefore its detection is of special importance. In this paper, one cadmium complex of terpyridine (tpy) derivative, 4'-(aminomethylphenyl)-2,2':6',2"-terpyridine (aptpy), has been reported for the ratiometric fluorescence recognition of PPi. When added with cadmium, the emission of aptpy at 358 nm was greatly enhanced and red shifted to 397 nm due to the complexation-induced ICT process, which then blue shifted to 349 nm upon the further addition of PPi. Based on the different response of dual fluorescence emissions at 349 and 397 nm, a ratiometric fluorescence method could be successfully established for the fluorescence recognition of PPi. With that, PPi could be successfully discriminated from other structurally similar anions, including nucleotide triphosphates.

Design, synthesis and photophysical studies of dipyrromethene-based materials: insights into their applications in organic photovoltaic devices

This review article presents the most recent developments in the use of materials based on dipyrromethene (DPM) and azadipyrromethenes (ADPM) for organic photovoltaic (OPV) applications. These chromophores and their corresponding BF2-chelated derivatives BODIPY and aza-BODIPY, respectively, are well known for fluorescence-based applications but are relatively new in the field of photovoltaic research. This review examines the variety of relevant designs, synthetic methodologies and photophysical studies related to materials that incorporate these porphyrinoid-related dyes in their architecture. The main idea is to inspire readers to explore new avenues in the design of next generation small-molecule and bulk-heterojunction solar cell (BHJSC) OPV materials based on DPM chromophores. The main concepts are briefly explained, along with the main challenges that are to be resolved in order to take full advantage of solar energy.