Highly Reversible "On-Off-On" Fluorescence Switch Governed by pH, Utilizing Bis(Benzimidazole) Derivatives with Varied Link Groups.

In this work, a series of dibenzimidazole derivatives 1-4, act as highly reversible colorimetric and fluorescent pH chemosensor, were designed and synthesized. Excellent reversible pH response of these sensors could be found by a specific pH change through obvious fluorescent color changes. The response is not affected by common cations (including Al3+, Cu2+, Ca2+, Cd2+, Co2+, Cr3+, Mg2+, Na+, K+, Ni2+, Pb2+ and Zn2+) and anions (including F-, Cl-, Br-, I-, ClO4-, H2PO4-, HSO4-, HCO3- and CH3COO-). Notably, these sensors can be reused more than 10 times without losing functionality. Unlike previous reports, the distinct properties of 1-4 are attributed to the varied link groups. Based on comprehensive experimental data and mechanistic analyses, it is concluded that sensors 1-4 are promising candidates for use as highly reversible "on-off-on" fluorescence switches under precise pH control.

A Sensitive Fluorescent Sensor for Highly Sensitive Detection of Water in Organic Solvents Based on Substituted Imidazole.

A novel substituted imidazole derivative 1a with carboxyl and quinoline structure has been designed and synthesized. And our initial discovery is that this compound can effectively detect water in ethanol. And the metal in solution couldn't affect the absorption and fluorescence Spectra of 1a. With the addition of water, the energy band appears a red-shift from 330nm to 355nm in the absorption spectra. And the emission spectrum undergoes an important change in its fluorescent effect in the presence of water. Furthermore, absorption peak of 1a displays a red-shift with increasing pH from 2.31 to 10.72. All available data (absorption and emission) strongly support the possible mechanism. Due to the pronounced fluorescence changing property, the substituted imidazole derivative 1a could be utilized as fluorescent probes for detecting water in ethanol.

Pillar[n]MaxQ: A New High Affinity Host Family for Sequestration in Water.

We report the synthesis, X-ray crystal structure, and molecular recognition properties of pillar[n]arene derivative P[6]AS, which we refer to as Pillar[6]MaxQ along with analogues P[5]AS and P[7]AS toward guests 1-18. The ultratight binding affinity of P[5]AS and P[6]AS toward quaternary (di)ammonium ions renders them prime candidates for in vitro and in vivo non-covalent bioconjugation, for imaging and delivery applications, and as in vivo sequestration agents.

Triazole functionalized acyclic cucurbit[n]uril-type receptors: host·guest recognition properties.

We report the synthesis of three new triazole functionalized acyclic CB[n]-type receptors (2-4) by click chemistry. The compounds have good solubility in water (≥8 mM) and do not undergo strong self-association (Ks ≤ 903 M-1). We measured the binding constants of 2-4 toward guests 9-24 and compared the results to those obtained for the prototypical acyclic CB[n]-type receptor 1. The X-ray crystal structure of 4 is also described.

Acyclic Cucurbit[n]uril Type Receptors: Secondary Versus Tertiary Amide Arms.

Two acyclic CB[n]-type hosts (1 and 2) which possess four 2° or 3° amide arms are reported; 1 and 2 are slightly soluble in water and do not self-associate. Host 2 has four 3° amide arms that exist as a mixture of E- and Z-isomers. 1H NMR was used to qualitatively investigate the binding properties of 1 and 2 which indicates they retain the essential binding features of macrocyclic CB[n] hosts (e.g. cavity binding of hydrophobic residues and portal binding of cationic groups). We measured the Ka values of 1 and 2 toward guests 6 - 12, methamphetamine, and fentanyl by ITC to evaluate their potential as in vivo sequestration agents. Neutral hosts 1 and 2 bind less tightly than tetraanionic hosts M1, ACB1, and ACB2. We attribute the lower Ka values to the absence of secondary ion-ion (ammonium•••sulfonate or ammonium•••carboxylate) electrostatic interactions for host•guest complexes of 1 and 2. The secondary amide functionality on 1 decreases affinity by formation of intramolecular NH•••O=C H-bonds. Tertiary amide host 2 binds even more weakly than 1 due to backfolding of the amide N-CH3-groups of 2 into its own cavity. The x-ray crystal structure of 2 supports this conclusion.

Hybrid Molecular Container Based on Glycoluril and Triptycene: Synthesis, Binding Properties, and Triggered Release.

We designed and synthesized a "hybrid" molecular container 1, which is structurally related to both cucurbit[n]uril (CB[n]) and pillar[n]arene type receptors. Receptor 1 was fully characterized by 1 H NMR, 13 C NMR, IR, MS and X-ray single crystal diffraction. The self-association behavior, host-guest recognition properties of 1, and the [salt] dependence of Ka were investigated in detail by 1 H NMR and isothermal titration calorimetry (ITC). Optical transmittance and TEM measurements provide strong evidence that receptor 1 undergoes co-assemble with amphiphilic guest C10 in water to form supramolecular bilayer vesicles (diameter 25.6±2.7 nm, wall thickness ≈3.5 nm) that can encapsulate the hydrophilic anticancer drug doxorubicin (DOX) and the hydrophobic dye Nile red (NR). The release of encapsulated DOX or NR from the vesicles can be triggered by hexamethonium (8 c) or spermine (10) which leads to the disruption of the supramolecular vesicles.

Pillar[6]MaxQ: A Potent Supramolecular Host for In Vivo Sequestration of Methamphetamine and Fentanyl.

Pillar[6]MaxQ (P6AS) functions as an in vivo sequestration agent for methamphetamine and fentanyl. We use 1H NMR, isothermal titration calorimetry, and molecular modelling to deduce the geometry and strength of the P6AS•drug complexes. P6AS forms tight complexes with fentanyl (Kd=9.8 nM), PCP (17.1 nM), MDMA (25.5 nM), mephedrone (52.4 nM), and methamphetamine (101 nM). P6AS has good in vitro biocompatibility according to MTS metabolic, Adenylate Kinase cell death, and hERG ion channel inhibition assays, and the Ames fluctuation test. The no observed adverse effect level for P6AS is 45 mg/kg. The hyperlocomotion of mice treated with methamphetamine (0.5 mg/kg) can be ameliorated by treatment with P6AS (35.7 mg/kg) 5-minutes later, whereas the hyperlocomotion of mice treated with fentanyl (0.1 mg/kg) can be controlled by treatment with P6AS (5 mg/kg) up to 15-minutes later. P6AS has significant potential for development as a broad spectrum in vivo sequestration agent.

(3,6-Dibromo-o-phenyl-ene)dimethanol.

The title compound, C(8)H(8)Br(2)O(2), was synthesized from the hydrolysis of 1,4-dibromo-2,3-bis-(bromo-meth-yl)benzene. One intra-molecular O-H⋯O and two intra-molecular C-H⋯Br inter-actions occur. In the crystal, mol-ecules are linked into a chain running parallel to [010]. Adjacent chains are linked into a two-dimensional layer by a combination of inter-molecular O-H⋯O hydrogen bonds and C-H⋯π inter-actions.

4,6-Dibromo-2,3-dimethyl-phenol.

The mol-ecule of the title compound, C(8)H(8)Br(2)O, is approximately planar with a maximum deviation of 0.063 (1) Šfor one of the Br atoms. In the crystal, adjacent mol-ecules are joined inter-molecular O-H⋯O hydrogen bonds, forming chains parallel to [010]. The structure also features a short Br⋯Br inter-action of 3.362 (1) Å.

2,7-Bis(prop-2-yn-1-yl-oxy)naphthalene.

The title compound, C(16)H(12)O(2), was synthesized from naphthalene-2,7-diol and prop-2-ynyl 4-methyl-benzene-sulfonate in the presence of sodium hydride. The crystal packing exhibits inter-molecular non-classical C-H⋯O hydrogen bonds and C-H⋯π inter-actions.

A novel self-sequence reaction network involving a set of six reactions in one pot: the synthesis of substituted benzothiazoles from aromatic ketones and anilines.

Employing simple and readily available aromatic ketones and anilines as starting materials resulted in the construction of 2-acylbenzothiazoles via a novel self-sequence reaction network, which assembles six reactions in one pot. The reaction network not only supplied a novel method for constructing complex molecules but also provided a typical example for logical self-organization synthesis.

Novel furo[2,3-d] pyrimidine derivative as fluorescent chemosensor for HSO4⁻.

A class of novel heterocyclic compounds 1a-1c has been designed and synthesized. And our initial discovery is that these compounds can effectively recognize HSO(4)(-). With the addition of HSO(4)(-), a new energy band appears at 360-390nm in the absorption spectra. The emission spectrum (λ(ex)=328 nm) undergoes an important change in its fluorescent effect in the presence of HSO(4)(-). All available data (absorption and emission) strongly support the formation of hydrogen-bonded complexes between 1a and 1c and HSO(4)(-).

Convergent integration of two self-labor domino sequences: a novel method for the synthesis of oxazole derivatives from methyl ketones and benzoins.

A highly efficient method for the synthesis of oxazole derivatives from methyl ketones, benzoins and ammonium acetate has been established via a novel strategy-convergent integration of two self-labor domino sequences. Owing to the simple and readily available starting materials, mild reaction conditions, facile operation, and the high bioactivity of oxazole derivatives, this reaction promises diverse applications in medical chemistry. Additionally, this reaction could provide an efficient example for self-labor synthesis strategy of organic compounds.

Diversity-oriented synthesis of chromenes via metal-free domino reactions from ketones and phenols.

Functionalized chromenes have been synthesized via highly selective metal-free domino reactions from ketones and phenols. 2H-Chromenes, 4H-chromenes, spiran and benzocyclopentane can be respectively prepared starting from the corresponding cyclic ketones, aryl methyl ketones, acetone, and 3-pentanone.

Direct synthesis of substituted naphthalenes from 1,3-dicarbonyl compounds and 1,2-bis(halomethyl)benzenes including a novel rearrangement aromatization of benzo[c]oxepine.

An unexpected rearrangement aromatization of benzo[c]oxepine has been revealed to synthesize substituted naphthalenes. This observation was further exploited to develop an efficient approach for the construction of naphthalenes from simple and commercially available 1,3-dicarbonyl compounds and 1,2-bis(halomethyl)benzene compounds via a new domino reaction sequence.