Thiourea–isothiouronium conjugate for strong and selective binding of very hydrophilic H2PO4− anion at the 1,2-dichloroethane–water interface

Synthesis and crystal structure of (E)-2-benzyl-1,3-di-phenyl-iso-thio-uronium iodide

In the title mol-ecular salt, C₂₀H₁₉N₂S⁺·I^-, prepared by the reaction of 1,3-di-phenyl-thio-urea and benzyl iodide, the C-S-C thio-ether bond angle is 101.66 (9)° and electrons are delocalized over the N⁺= C-N skeleton. The dihedral angle between the aromatic rings attached to the N atoms is 40.60 (9)°. In the crystal, N-H⋯I hydrogen bonds link the components into [100] chains.

Crystal structure of 2-(3-((carbamimidoylthio)methyl)benzyl)isothiouronium hexafluorophosphate monohydrate, C10H17F6N4OPS2

C10H17F6N4OPS2, orthorhombic, P212121 (no. 19), a = 8.7848(9) Å, b = 9.8894(11) Å, c = 18.8020(19) Å, V = 1633.4(3) Å3, Z = 4, R gt (F) = 0.0348, wR ref (F 2) = 0.0943, T = 150 K.

New uranium(vi) and isothiouronium complexes: synthesis, crystal structure, spectroscopic characterization and a DFT study

U(vi) and isothiouronium salts create a strong charge-assisted network of hydrogen bonds and ionic interactions.

Novel phenyl(thio)ureas bearing (thio)oxothiazoline group as potential BACE-1 inhibitors: synthesis and biological evaluation

We report the synthesis and the β-site amyloid precursor protein cleaving enzyme-1 inhibitory properties of novel phenyl(thio)ureas bearing 2-(thio)oxothiazoline derivatives. A library of analogues was prepared according to specific synthetic schemes and the inhibitory activity was monitored using a fluorescence resonance energy transfer assay. Several analogues show potent inhibitory activities ranging between 1 and 0.01 µM and the activity is related to the NH acidity of the (thio)urea motif. Our results illustrate once again the close relationship between molecular recognition, complexation of the active site in enzymatic system, and organocatalysis utilizing explicit hydrogen bonding.

The role of the ring nitrogen and the amino group in the solvent dependence of the excited-state dynamics of 3-aminoquinoline

The nonradiative rate in 3-aminoquinoline is found to exhibit anomalous solvent dependence, being rather fast in nonpolar solvents and remarkably slower in more polar and especially, more protic ones. The cause of such behavior is investigated by studying the dependence of fluorescence spectral and temporal parameters on the solvent properties such as polarity and hydrogen bonding ability. Complementary quantum mechanical calculations have been performed and the picture that emerges from these studies is that of an excited state with a short radiative lifetime due to the flipping of the amino group. This state is selectively populated in nonpolar, nonhydrogen bonding solvents, but is destabilized with respect to the more polar intramolecular charge transfer (ICT) state in polar solvents and even more so in protic solvents and dimethylsulfoxide. The slower nonradiative rates in the ICT state is attributed to the more restricted motion of the amino group in this state. The role of hydrogen bonding of the amino group and the ring nitrogen in stabilization/destabilization of the ICT state and therefore on the nonradiative rate is also explored.

Model systems for flavoenzyme activity: recognition and redox modulation of flavin mononucleotide in water using nanoparticles

We have used mixed monolayer protected gold clusters (MMPCs) to provide flavoenzyme model systems with a high affinity and ability to modulate cofactor reduction potential.

Colorimetric "naked eye" sensing of anions in aqueous solution

[structure: see text] The synthesis and UV-vis and NMR spectroscopic studies of thiourea-based colorimetric sensors for anions are presented. These sensors can recognize anions through hydrogen binding even in competitive pH-buffered aqueous solutions, giving rise to large color changes that are clearly visible to the naked eye.

Recent analytical methodologies on equilibrium, kinetics, and dynamics at liquid/liquid interface

The form of liquid/liquid interface is flexible and it cannot be fixed at a spatial position. Also the interface is prevented from any physical contact by the organic phase and aqueous phase. In addition, analytical methods operated in vacuo cannot be applied. These restrictions depressed the development of liquid/liquid interfacial chemistry. However, the modification of liquid/liquid interfacial form and original analytical methods have been invented interdependently. The present review classifies the forms of liquid/liquid interface first, and it arrays the related analytical methods with brief explanations. It dominantly deals with recent reports of analytical methodologies, which were published in 2001-2004, on equilibrium, kinetics, and dynamics of substances at liquid/liquid interface, but it also includes historically important studies.

Visual Detection of Anions by a Novel Isothiourea-based Chromophore

S-Methyl-N-methyl-N'-(4-(N",N"-dimethylamino)phenyl)isothiourea, a novel isothiourea-based chromoionophore for anions, was synthesized. The reactivity for several anions was estimated by a visual method and UV-vis spectroscopy. By the addition of acetate ion, a blue shift in the absorption spectrum was observed in CHCl3, and the solvent color changed from yellow to colorless. These changes indicated that bound acetate ion interfered with the intramolecular charge transfer from the nitrogen atom of the diethylamino group to the isothiourea moiety. The addition of chloride ion caused a red shift of the chromophore and solvent color remained yellow. By the addition of dihydrogenphosphate ion, the precipitate was formed immediately. These anion-dependent natures of the chromoionophore allowed us to detect acetate and phosphate ions easily.

Adsorption behavior of lauric acid at heptane/water interface as studied by second harmonic generation spectroscopy and interfacial tensiometry

Interfacial tensiometry and second harmonic generation (SHG) spectroscopy were applied to examine the adsorption behavior of lauric acid (LA) at a heptane/water interface. From interfacial tensiometry measurements, the adsorption kinetics of LA was revealed to be diffusion-controlled, and the adsorption constant of LA was estimated to be 9.6 x 10(4) M(-1). The adsorption isotherms obtained by SHG measurements were analyzed by taking account of both the molecular orientation of LA at the interface and a surface electric field generated by the adsorbed LA layer. It was confirmed that the carboxylic groups of adsorbed LA molecules were well ordered at the heptane/water interface and the orientation of the carboxylate group was invariant during the adsorption process.

Facilitated Sulfate Transfer across the Nitrobenzene-Water Interface as Mediated by Hydrogen-Bonding Ionophores

Facilitated SO4(2-) transfers by hydrogen bond-forming ionophores are investigated across the nitrobenzene (NB)-water interface by using polarography with a dropping electrolyte electrode. Bis-thiourea 1, alpha,alpha'-bis(N'-p-nitrophenylthioureylene)-m-xylene, is found to significantly facilitate the transfer of the highly hydrophilic SO4(2-) whereas its counterpart, N-(p-nitrophenyl)-N'-propylthiourea (ionophore 2), cannot. In contrast to the predominant formation of a 1:1 complex with SO4(2-) in the bulk NB phase, the SO4(2-) transfer assisted by 1 is indeed based on the formation of a 1:2 complex between SO4(2-) and ionophore, even under the condition of [SO4(2-)]aq >> [1]org. Such an exclusive formation of the 1:2 (SO4(2-) to ionophore) complex at the NB-water interface is not observed with structurally similar bis-thiourea 3, alpha,alpha'-bis(N'-phenylthioureylene)-m-xylene, where p-nitrophenyl moietes of bis-thiourea 1 are simply replaced by phenyl groups. The facilitated transfer of SO4(2-) with bis-thiourea 1 is further compared to that of HPO4(2-) and H2PO4- across the NB-water interface, which was previously shown to be assisted by 1 through the formation of the 1:1 and 2:1 (anion to ionophore) complexes, respectively. On the basis of these examinations, unique binding behaviors of hydrogen bond-forming ionophores at the NB-water interface are discussed, with a view towards development of ionophore-based anion-selective chemical sensors.