Solvent effect and fluorescence response of the 7-tert-butylpyrene-dipicolylamine linkage for the selective and sensitive response toward Zn(II) and Cd(II) ions

The different binding behaviour of 7-tert-butylpyrene based chemosensors bearing dipicolylamine (Dpa) linkages at the 1,3-positions was investigated in various solvents for the sensing of Zn(II) and Cd(II).The potential mono-chelating ligand L1 follows the same binding pattern in both THF and methanol–water solvent systems, exhibiting higher selectivity and sensitivity for Cd(II) over Zn(II) mainly in THF solvent system. The potential bis-chelate ligand L2 can selectively bind both Zn(II) and Cd(II) in a 1:1 ratio in THF, whereas in methanol–water (7:3) at pH = 7.0; a 1:2 binding ratio was observed. In THF, two sites of ligand L2 can only selectively and sensitively bind one Zn(II) or Cd(II). The different complexation behaviour of L1 and L2 in different solvents were studied by means of fluorescence spectra and ¹H-NMR titration experiments in the presence of Zn(II) and Cd(II)

Positive allosteric binding behavior of pyrene-appended triazole-modified thiacalix[4]arene-based fluorescent receptors

The novel heteroditopic receptors 5a∼c have been synthesized, which bear a thiacalix[4]arene in the 1,3-alternate conformation. Two urea moieties possessing various aryl groups with either electron-donating or -withdrawing groups at their p-positions function as anion-binding sites. At the opposite side of the cavity are two pyrene-appended triazole rings, which act as cation-binding sites. The binding property of receptor 5c was investigated by means of 1H NMR and UV–vis spectroscopy and by fluorescence titration experiments in the presence of various transition metal cations and anions in CH2Cl2–DMSO (10:1, v/v) solution. Interestingly, it was found that receptor 5c possessing two p-nitrophenyl ureido moieties, most efficiently complexes in the urea cavity or bistriazoles; the plausible allosteric effect of receptor 5c was also investigated

Synthesis and conformational studies of chiral macrocyclic [1.1.1]metacyclophanes containing benzofuran rings

Macrocyclic [1.1.1]metacyclophanes (MCPs) containing benzene and benzofuran rings linked by methylene bridges and which can be viewed as calixarene analogues, have been synthesized by demethylation of [3.3.1]MCP-diones with trimethylsilyl iodide (TMSI) in MeCN. The [3.3.1]MCP-diones are synthesized by using (p-tolylsulfonyl)methyl isocyanide (TosMIC) as the cyclization reagent in N,N-dimethylformamide (DMF) with an excess of sodium hydride. ¹H NMR spectroscopy revealed that the remaining hydroxyl group on the phenyl ring is involved in intramolecular hydrogen bonding with the oxygen of one of the benzofuran rings. O-Methylation at the lower rim of monohydroxy[1.1.1]MCP in the presence of K₂CO₃ in acetone afforded a novel and inherently chiral calixarene analogue, namely the macrocyclic [1.1.1]MCP, possessing C₁ symmetry. The inherent chirality of the two conformers was characterized by ¹H NMR spectroscopy by addition of an excess of Pirkle's chiral shift reagent, which caused a splitting of the corresponding methylene protons to AB patterns. Single crystal X-ray analysis revealed the adoptation of a hemisphere-shaped cone isomer. DFT calculations were carried out to investigate the energy-minimized structures and the hydrogen bonds of the synthesized MCPs

A study of allosteric binding behaviour of a 1,3-alternate thiacalix[4]arene-based receptor using fluorescence signal

A novel heteroditopic thiacalix[4]arene receptor L possessing 1,3-alternate conformation, which contains two pyrene moieties attached to the lower rim via urea linkages together with a crown ether moiety appended at the opposite side of the thiacalix[4]arene cavity, has been synthesized. The complexation behaviour of receptor L was studied by means of fluorescence spectra and ¹H NMR titration experiments in the presence of K⁺ ions and a variety of other anions. The results suggested that receptor L can complex efficiently via the urea cavity or the crown ether moiety, and a positive/negative allosteric effect operating in receptor L was observed

Regio-selective substitution at the 1,3- and 6,8-positions of pyrene for the construction of small dipolar molecules

© 2015 American Chemical Society. This article presents a novel asymmetrical functionalization strategy for the construction of dipolar molecules via efficient regioselective functionalization along the Z-axis of pyrene at both the 1,3- and 6,8-positions. Three asymmetrical ly substituted 1,3-diphenyl-6,8-R-disubsituted pyrenes were fully characterized by X-ray crystallography, photophysical properties, electrochemistry, and density functional theory calculations

Synthesis and evaluation of a novel ionophore based on a thiacalix[4]arene derivative bearing imidazole units

O-Alkylation of the flexible thiacalix[4]arene 1 with 2-chloromethyl-1-methyl-1H-imidazole 2 in the presence of Na₂CO₃ or K₂CO₃ afforded mono-O-alkylation product 3 in 29–51% yield, along with recovery of the starting compound. In contrast, the same reaction in the presence of Cs₂CO₃ gave only one pure stereoisomer, namely 1,3-alternate-4; other possible isomers were not observed. Alkali metal salts such as Na₂CO₃ and Cs₂CO₃ can play an important role in the conformer distribution via a template effect. The conformations of the receptors, mono-O-alkylation product 3 and that of 1,3-alternate-4, have been confirmed by X-ray crystallography. Furthermore, the complexation properties of the receptor 1,3-alternate-4 toward selected alkali/transition metal cations are reported. The two-phase solvent extraction data indicated that 1,3-alternate-4 exhibited a stronger extraction efficiency for transition metals over alkali metals. The dichromate anion extraction ability of 1,3-alternate-4 showed that it could serve as an efficient extractor of HCr₂O₇⁻/Cr₂O₇²⁻ anions at low pH

Iron(III) bromide catalyzed bromination of 2-tert-butylpyrene and corresponding position-dependent aryl-functionalized pyrene derivatives

The present work probes the bromination mechanism of 2-tert-butylpyrene (1), which regioselectively affords mono-, di-, tri- and tetra-bromopyrenes, by theoretical calculation and detailed experimental methods. The bromine atom may be directed to the K-region (positions 5- and 9-) instead of the more reactive 6- and 8-positions in the presence of iron powder. In this process, FeBr₃ plays a significant role to release steric hindrance or lower the activation energy of the rearrangement. The intermediate bromopyrene derivatives were isolated and confirmed by ¹H NMR spectrometry, mass spectroscopy and elemental analysis. Further evidence on substitution position originated from a series of aryl substituted pyrene derivatives, which were obtained from the corresponding bromopyrenes on reaction with 4-methoxy-phenylboronic acid by a Suzuki–Miyaura cross-coupling reaction. All position-dependent aryl-functionalized pyrene derivatives are characterized by single X-ray diffraction, ¹H/¹³C NMR, FT-IR and MS, and offered straightforward evidence to support our conclusion. Furthermore, the photophysical properties of a series of compounds were confirmed by fluorescence and absorption, as well as by fluorescence lifetime measurements

Synthesis and photophysical properties of novel butterfly-shaped blue emitters based on pyrene

Synthesis and photophysical properties of novel butterfly-shaped blue emitters based on pyren

Synthesis and conformational studies of calixarene analogue chiral [3.3.1]metacyclophanes

Trihydroxy[3.3.1]metacyclophane, which can be regarded as an unsymmetrical or incomplete “homocalix[3]arene”, has been prepared from trimethoxy[3.3.1]metacyclophane by demethylation with trimethylsilyl iodide in MeCN. Di-O-methylation at the lower rim of trihydroxy[3.3.1]metacyclophane in the presence of K₂CO₃ in acetone afforded a novel, inherently chiral calixarene–analogue, namely a macrocyclic [3.3.1]metacyclophane, possessing C₁ symmetry. The inherent chirality of the two conformers was characterized by ¹H NMR spectroscopy by addition of an excess of Pirkle's chiral shift reagent [(S)-(+)-1-(9-anthryl)-2,2,2-trifluoroethanol], which caused a splitting of the OMe group and AB patterns corresponding to the methylene protons

An efficient approach to the synthesis of novel pyrene-fused azaacenes

An efficient approach to the synthesis of novel pyrene-fused azaacene