Dipyrrolyl-Functionalized Bipyridine-Based Anion Receptors for Emission-Based Selective Detection of Dihydrogen Phosphate

Development and Application of Ruthenium(II) and Iridium(III) Based Complexes for Anion Sensing

Improvements in the design of receptors for the detection and quantification of anions are desirable and ongoing in the field of anion chemistry, and remarkable progress has been made in this direction. In this regard, the development of luminescent chemosensors for sensing anions is an imperative and demanding sub-area in supramolecular chemistry. This decade, in particular, witnessed advancements in chemosensors based on ruthenium and iridium complexes for anion sensing by virtue of their modular synthesis and rich chemical and photophysical properties, such as visible excitation wavelength, high quantum efficiency, high luminescence intensity, long lifetimes of phosphorescence, and large Stokes shifts, etc. Thus, this review aims to summarize the recent advances in the development of ruthenium(II) and iridium(III)-based complexes for their application as luminescent chemosensors for anion sensing. In addition, the focus was devoted to designing aspects of polypyridyl complexes of these two transition metals with different recognition motifs, which upon interacting with different inorganic anions, produces desirable quantifiable outputs.

Substituent-Dependent Divergent Synthesis of 2-(3-Amino-2,4-dicyanophenyl)pyrroles, Pyrrolyldienols and 3-Amino-1-acylethylidene-2-cyanopyrrolizines via Reaction of Acylethynylpyrroles with Malononitrile

An efficient method for the synthesis of pharmaceutically and high-tech prospective 2-(3-amino-2,4-dicyanophenyl)pyrroles (in up to 88% yield) via the reaction of easily available substituted acylethynylpyrroles with malononitrile has been developed. The reaction proceeds in the KOH/MeCN system at 0 °C for 2 h. In the case of 2-acylethynylpyrroles without substituents in the pyrrole ring, the reaction changes direction: instead of the target 2-(3-amino-2,4-dicyanophenyl)pyrroles, the unexpected formation of pyrrolyldienols and products of their intramolecular cyclization, 3-amino-1-acylethylidene-2-cyanopyrrolizines, is observed.

Development of a nickel oxide/oxyhydroxide-modified printed carbon electrode as an all solid-state sensor for potentiometric phosphate detection

This work describes the preparation, characterization and use of a nickel oxide/oxyhydroxide-printed carbon electrode as an efficient potentiometric phosphate sensor.

2,2'-Bipyrrole-Based Porphyrinoids

A large number of porphyrinoids containing 2,2'-bipyrrole subunits have appeared since they were originally found as a component of sapphyrin and corrole, and it was found that the bipyrrole subunit endowed macrocycles with specific geometric features and electronic properties. Synthetic methods for bipyrrole-containing precursors for porphyrinoid are summarized in this review; these include coupling reactions of pyrrole rings, pyrrole ring-forming reactions leading directly to bipyrrole units, and synthetic reactions for oligopyrrolic compounds. Some hybrid oligopyrroles having nonpyrrole (hetero)aromatic ring(s) are also included. This review also describes porphyrinoids composed of bipyrrole subunits. Interesting electronic properties derived from strong cyclo-π-conjugation are highlighted in the bipyrrole-based porphyrinoids with or without meso-like carbons. Anion-binding chemistry is one of the main topics for bipyrrole-based macrocycles with less efficient or deficient cyclo-π-conjugation, such as those linked with electronically localized aromatic ring(s), with sp³ carbon(s), and with amido or imine connection(s). The principal concern in this review is porphyrinoids of relatively large ring size, composed of more than five units of pyrroles and (hetero)aromatic substitutes in total, and so bipyrrole-based porphyrinoids up to five pyrrolic units, such as corroles, porphycenes, sapphyrins, and smaragdyrin, will not be covered here except for some special cases.

Potentiometric sensing of aqueous phosphate by competition assays using ion-exchanger doped-polymeric membrane electrodes as transducers

Using Zn(2+)-BPMP or Cu(2+)-BPMP as a receptor and o-mercaptophenol as an indicator, potentiometric sensing of aqueous phosphate by competition assays was achieved. With attractive features of portability, low cost and resistance to interference from turbidity and color, this sensor was successfully used for phosphate detection in biological and water samples.

A 1,3-Capped Calix[4] Conjugate Possessing an Amine Moiety as an Anion Receptor: Reversible Anion Sensing Detected by Spectroscopy and Characterization of the Supramolecular Features by Microscopy

A phenylenediamine-capped conjugate of calix[4]arene (Lamino ) was synthesized by reducing its precursor, Limino , with sodium borohydride in methanol. The Lamino sample binds to anions due to the more flexible and bent conformation of the capped aminophenolic binding core, compared to the precursor Limino . The Lamino sample showed selectivity towards H2 PO4 (-) by exhibiting a ratiometric increase in emission by about 11-fold with a detection limit of (1.2±0.2) μm ((116±20) ppb) over 15 anions studied, including other phosphates, such as P2 O7 (4-) , adenosine monophosphate (AMP(2-) ), adenosine diphosphate (ADP(2-) ), and adenosine triphosphate (ATP(2-) ). The Lamino sample shows an increase in the absorbance at λ=315 nm in the presence of H2 PO4 (-) , CO3 (2-) , HCO3 (-) , CH3 CO2 (-) , and F(-) . The (1) H NMR spectroscopic titration of Lamino with H2 PO4 (-) , F(-) , and CH3 CO2 (-) showed major changes in the phenylene-capped and salicyl moieties, and thereby, confirming the aminophenolic region as the binding core. However, the binding strength of these anions followed the trend H2 PO4 (-) >F(-) ≫CH3 CO2 (-) >HSO4 (-) . The heat changes observed by isothermal titration calorimetry support this trend. The Lamino sample showed reversible sensing towards H2 PO4 (-) and F(-) in the presence of Mg(2+) and Ca(2+) , respectively. NOESY studies of Lamino , in comparison with its anionic complexes, revealed that major conformational changes occurred in the capping region to facilitate the binding of anion. ESI-MS and the Job's method revealed 1:1 stoichiometry between Lamino and H2 PO4 (-) or F(-) . In the SEM micrographs of Lamino , the spherical particles are converted into spherical aggregates and further form large agglomerates and even branched sheets in the presence of anions, depending upon their binding strength.

Ruthenium(II) Complexes of Aryl Triazole Foldamers as Receptors for Anions

Ruthenium(II) complexes of oligo(bipyridine-phenyl triazole)s were synthesized as receptors for anions. The receptors, which are partially preorganized through metal-ligand interactions, can fold into a helical conformation to bind chloride, bromide, iodide, or nitrate anions in their inner cavities in acetone or competitive H-bonding media such as 5% water in acetone and DMSO. The short oligomer 1 can sandwich the studied anions with high affinity in acetone. Addition of 5% water to acetone results in overall decreases in the binding strength due to the binding competition from water, but does not change the basic binding mode. The highly competitive H-bonding solvent DMSO causes the receptor-anion interactions to become even weaker. However, in DMSO, the short receptor 1 is still able to bind the halide anions with moderate affinities in a 1:1 stoichiometry, whereas the longer oligomer 2 forms double-strand helices with an anion wrapped inside for all anions investigated so far.

A functional ruthenium(ii) complex for imaging biothiols in living bodies

A functional ruthenium(ii) complex that can act as a luminescent probe for imaging biothiols in living bodies has been successfully developed.

Is metal metathesis a framework-templating strategy to synthesize coordination polymers (CPs)? Transmetallation studies involving flexible ligands

Framework-templating strategy, where Cd-CP acted as template to preorganise the linkers, resulted in a Cu-CP, which was not obtained by direct reaction of Cu(ii) and the ligand.

α-Monoacylated and α,α'- and α,β'-diacylated dipyrrins as highly sensitive fluorescence "turn-on" Zn2+ probes

With the purpose of developing readily synthesized CHEF (chelation-enhanced fluorescence) type Zn(2+) probes with relatively simple molecular structures and excellent sensing behavior, p-anisoyl chloride was used for the acylation of 5-(pentafluorophenyl)dipyrromethane. Interestingly, the α,β'-diacylated product PS2 with a unique substitution mode was obtained in high yield in addition to the normal α-substituted mono- and diacylated products PS1 and PS3. Further oxidation of PS1-PS3 afforded dipyrrins S1-S3. Crystal structure and (1)H NMR measurements of S2 demonstrate the existence of a pure tautomer, which is consistent with DFT calculations. S1-S3 show highly Zn(2+) selective "turn-on" fluorescence based on a CHEF mechanism by the formation of 2:1 (probe:metal) Zn(2+) complexes. The emission colors can be easily tuned from green to red by changing the dipyrrin substitution modes. Furthermore, these probes demonstrate fast responses and wide applicable pH ranges. Among them, S2 shows the highest Zn(2+) sensitivity, with a detection limit of 4.4 × 10(-8) M.

Ortho-phenylenediamine-based open and macrocyclic receptors in selective sensing of H2PO4(-), ATP and ADP under different conditions

Ortho-phenylenediamine-based open and macrocyclic receptors have been designed and synthesized. The open receptor 1 and the macrocyclic receptor 2 fluorimetrically distinguish H(2)PO(4)(-) from the other anions examined in CH(3)CN with appreciable binding constant values. As practical applications, they are also sensible to nucleotides in aq. CH(3)CN (1 : 1, v/v). The receptor 1 shows significant emission change upon complexation of ATP and ADP. ADP is selectively distinguished by a ratiometric change in emission. In contrast, the macrocyclic receptor 2, under similar conditions, shows good binding with ATP over the others.

Toward unidirectional switches: 2-(2-Hydroxyphenyl)pyridine and 2-(2-methoxyphenyl)pyridine derivatives as pH-triggered pivots

The pH-induced switching process of 2-(2-hydroxyphenyl)pyridine and 2-(2-methoxyphenyl)pyridine derivatives was investigated with the help of UV spectroscopy. Quantum chemical calculations at the B3LYP/6-31G* level of theory were performed to show that in the case of 2-(2-methoxyphenyl)-3-methylpyridine and 2-(2-hydroxyphenyl)-3-methylpyridine the rotation during the switching process proceeds unidirectionally at the molecular level. If a 2-(2-methoxyphenyl)pyridine derivative is fixed to a chiral cyclopeptidic scaffold, a unidirectional progress of the rotation is achieved macroscopically.

Synthesis of 2,3,4-trisubstituted pyrroles via a facile reaction of vinyl azides and tosylmethyl isocyanide

A facile synthesis of polysubstituted pyrroles from tosylmethyl isocyanide (TOSMIC) and readily synthesized vinyl azides was developed. The reaction proceeded under mild conditions in the presence of base. 2-Tosyl-substituted pyrroles were obtained in moderate to good isolated yields. Additionally, a base-initiated one-pot pyrrole synthesis also was developed using carboxaldehydes, ethyl 2-azidoacetate, and TOSMIC.

Tetrathiafulvalene diindolylquinoxaline: a dual signaling anion receptor with phosphate selectivity

Incorporation of tetrathiafulvalene into the backbone of a known neutral phosphate receptor, diindolylquinoxaline, yields a dual optical-electrochemical chemosensor for dihydrogen phosphate that functions in dichloromethane. This system shows selectivity for dihydrogen phosphate over other small anions and can be used to detect the presence of this analyte via fluorescence quenching or cyclic voltammetry.