HBr or not HBr? That is the question: crystal structure of 6‐hydroxy‐1,4‐diazepane‐1,4‐diium dibromide redetermined

Liu et al. [Chin. J. Struct. Chem. (1996). 15 , 371–373] reported the structure of 6‐hydroxy‐1,4‐diazepane di(hydrogen bromide), C₅H₁₂N₂O·2HBr, which was interpreted in terms of neutral diazepane and HBr molecules. We found, however, ample evidence that the formation of an organic salt, consisting of a diammonium cation and two bromide anions, is more plausible. This interpretation is also in agreement with thermogravimetric analysis and with the observed solution behaviour. The crystal structure of 6‐hydroxy‐1,4‐diazepane‐1,4‐diium dibromide, C₅H₁₄N₂O²⁺·2Br^?, measured at 142 K, crystallized in the orthorhombic space group P2₁2₁2₁. The structure displays O—H…Br and N—H…Br hydrogen bonding. Contact distances are given. A search in the Cambridge Structural Database for the singly‐bonded H—Br moiety revealed a total of 69 structures. The question, whether these structures really include HBr as neutral molecules or rather Br^? anions and a protonated substrate such as an amine, is addressed.     

Volumetric Properties for the Electrolyte (NaCl,NaBr and NaI) Monosaccharide (D‐Mannose and D‐Ribose)‐Water Systems at 298.15 K

Densities have been measured for the electrolyte (NaCl, NaBr and NaI)‐monosaccharide (D ‐mannose and D‐ribose)‐water solutions at 298.15 K. These data have been used to calculate the apparent molar volumes of the saccharides (V_Φ,S) and electrolytes (V_Φ,E) in the studied solutions. Infinite dilution apparent molar volumes, V_Φ,S⁰ and V_Φ,E⁰, have been evaluated, together with the standard transfer volumes of the saccharides (Δ_tV_S⁰) from water to aqueous electrolyte solutions and those of the electrolytes (Δ_tV_E⁰) from water to aqueous saccharide solutions. It was shown that both the Δ_tV_S⁰ and Δ_tV_E⁰ values are positive and increase with increasing molalities of sodium halides and saccharides, respectively. Overall, the Δ_tV_S⁰ and Δ_tV_E⁰ values have the order of NaCl > NaBr > NaI except for NaI‐ribose and NaI‐ribose. Volumetric interaction parameters for the electrolyte‐monosaccharide pairs in water were obtained and interpreted by the stereochemistry of the monosaccharide molecules and the structural interaction model.     

Mechanistic insight into the reactivity of oxotransferases by novel asymmetric dioxomolybdenum(VI) model complexes

The asymmetric molybdenum(VI) dioxo complexes of the bis(phenolate) ligands 1,4‐bis(2‐hydroxybenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐4‐methylbenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐3,5‐dimethylbenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐3,5‐di‐tert‐butylbenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐4‐flurobenzyl)‐1,4‐diazepane, and 1,4‐bis(2‐hydroxy‐4‐chlorobenzyl)‐1,4‐diazepane (H₂(L1)–H₂(L6), respectively) have been isolated and studied as functional models for molybdenum oxotransferase enzymes. These complexes have been characterized as asymmetric complexes of type [MoO₂(L)] 1–6 by using NMR spectroscopy, mass spectrometry, elemental analysis, and electrochemical methods. The molecular structures of [MoO₂(L)] 1–4 have been successfully determined by single‐crystal X‐ray diffraction analyses, which show them to exhibit a distorted octahedral coordination geometry around molybdenum(VI) in an asymmetrical cis‐β configuration. The Mo? O_oxo bond lengths differ only by ≈0.01 Å. Complexes 1 , 2 , 5 , and 6 exhibit two successive Mo^VI/Mo^V (E_1/2, ?1.141 to ?1.848 V) and Mo^V/Mo^IV (E_1/2, ?1.531 to ?2.114 V) redox processes. However, only the Mo^VI/Mo^V redox couple was observed for 3 and 4 , suggesting that the subsequent reduction of the molybdenum(V) species is difficult. Complexes 1 , 2 , 5 , and 6 elicit efficient catalytic oxygen‐atom transfer (OAT) from dimethylsulfoxide (DMSO) to PMe₃ at 65 °C at a significantly faster rate than the symmetric molybdenum(VI) complexes of the analogous linear bis(phenolate) ligands known so far to exhibit OAT reactions at a higher temperature (130 °C). However, complexes 3 and 4 fail to perform the OAT reaction from DMSO to PMe₃ at 65 °C. DFT/B3LYP calculations on the OAT mechanism reveal a strong trans effect.     

Determination and pharmacokinetics of [6]-gingerol in mouse plasma by liquid chromatography-tandem mass spectrometry

This study describes the development of a rapid and sensitive high‐performance liquid chromatography–electrospray ionization tandem mass spectrometry (LC‐MS/MS) assay for the quantification of [6]‐gingerol in mouse plasma and application to a pharmacokinetic study after dose ranging in mice. The assay involved a protein precipitation step with acetonitrile and an isocratic elution using a mobile phase consisting of acetonitrile and water containing 0.1% formic acid (80:20 v/v). The multiple reaction monitoring was based on the transition of m/z = 277.2 → 177.1 for [6]‐gingerol and 294.2 → 137.1 for nonivamide (internal standard). The assay was validated to demonstrate the specificity, linearity, recovery, accuracy, precision and stability. The calibration curves were linear over the wide concentration range of 10–10,000 ng/mL (r ≥ 0.9988). The lower limit of quantification was 10 ng/mL using a small volume of mouse plasma (20 μL). The method was successfully applied to a pharmacokinetic study in mice after intravenous injection of [6]‐gingerol at 1.5, 3 and 6 mg/kg doses. The pharmacokinetics of [6]‐gingerol were linear over the dose range studied as demonstrated by the linear increase in area under the concentration‐time curve (AUC_inf) with no significant change in the systemic clearance (Cl_s), volume of distribution (V_ss) and elimination half‐life (t_1/2) as a function of dose. Copyright © 2011 John Wiley & Sons, Ltd.     

ZrIV‐ und TaV‐Komplexe mit methanoverbrückten Bis(aryloxy)‐Liganden

Zr^IV and Ta^V Complexes with Methano‐Bridged Bis(aryloxy) Ligands The bis(aryloxy) ligand precursor compounds bis(2‐trimethylsiloxy‐5‐tbutylphenyl)methane (L–SiMe₃) and its bromoderivative (2‐trimethylsiloxy‐3‐bromo‐5‐tbutylphenyl)(2′‐trimethylsiloxy‐5′‐tbutylphenyl)methane (L^Br–SiMe₃) are prepared in analogy to the corresponding calixarenes in excellent yields. X‐ray structure analysis for L^Br–SiMe₃: space group P2₁/c, a = 12.462(7), b = 10.466(6), c = 23.315(14) Å, β = 105.02(4)°, V = 2937(3) ų, Z = 4. L–SiMe₃ and L^Br–SiMe₃ react with Zr^IV and Ta^V chlorides in very good yields forming di‐ and trinuclear complexes. From the reaction of CpZrCl₃ with L^Br–SiMe₃ in the ratio of 3 : 2 a Zr₃ complex ( 7 ) is obtained, with one L^Br ligand only, which Zr atoms are bridged by a μ₃‐oxygen. The X‐ray structure analysis of 7 (space group R 3, a = 33.23(6), c = 24.47(8) Å, V = 23405(128) ų, Z = 18) additionally reveals that one phenolato oxygen atom of the L^Br ligand is terminally bound to a distorted tetragonal‐pyramidal coordinated Zr atom, while the second phenolato oxygen atom of the L^Br ligand forms a bridge to another Zr atom with a distorted octahedral coordination. The third Zr atom is also found in a distorted octahedral coordination mode. The reactions of L–SiMe₃ and L^Br–SiMe₃ with CpTaCl₄ and TaCl₅ yield dinuclear Ta complexes with a bridging bis(aryloxy) ligand. NMR spectroscopic data point out that the coordination of the bis(aryloxy) ligands in the Ta complexes very much resembles that in the Zr₃‐complex with one terminal and one bridging phenolato oxygen atom. The Zr₃ and the Ta complexes L^BrTa₂Cp₂Cl₆ and LTa₂Cl₈ were tested with respect to their catalytic properties in olefin polymerisation reactions in the presence of MAO.     

Mechanistic Insights into an Unexpected Carbon Dioxide Insertion Reaction through the Crystal Structures of Carbamic Diphenylthiophosphinic Anhydride and l‐[(4‐Nitrophenyl)‐sulfonyl]‐trans‐2,5‐pyrrolidinedicarboxylic Acid Methyl Ester

The crystal structures of an unexpected carbon dioxide inserted carbamidiphenylthiophosphinic anhydride and l‐[(4‐nitrophenyl) sulfonyl]‐trans‐2, 5‐pyrrolidinedicarboxylic acid methyl ester were determined by X‐ray analysis. They crystallized in the space group P2₁(#4) with a =0.9550(2), b = 0.9401(4), c= 1.2880(2) nm, β= 107.74°, V= 1.1013 (5) nm³, D_caled= 1.349 g/cm³, Z = 2 and P2₁2₁2₁(# 19) with a = 1.4666(2), b = 0.7195(2), c = 1.6339(2) nm, V = 1.7240(7) nm³, D_caled = 1.434 g/cm³, Z = 4, respectively. Through the investigation of these two crystal structures, the mechanistic insights into this unexpected carbon dioxide insertion in the reaction of trans‐2,5‐disubstituted pyrrolidine with diphenylthiophosphoryl chloride in the presence of potassium carbonate were disclosed.     

Synthesis,self‐assembly,and formation of photo‐crosslinking‐stabilized fluorescent micelles covalently containing zinc(II)‐bis(8‐hydroxyquinoline) for ABC triblock copolymer bearing cinnamoyl and 8‐hydroxyquinoline side groups

Triblock copolymers (MPEG‐b‐PCEMA‐b‐PHQHEMA) bearing cinnamoyl and 8‐hydroxyquinoline side groups with different block length are synthesized by a two‐step reversible addition fragmentation chain transfer polymerization of cinnamoyl ethyl methacrylate (CEMA) and 2‐((8‐hydroxyquinolin‐5‐yl)methoxy)ethyl methacrylate (HQHEMA), respectively. The self‐assembly of MPEG‐b‐PCEMA‐b‐PHQHEMA in mixture of THF and ethanol is investigated by varying the ratio of THF and ethanol. Spheric micelles with diameter of 63.7 nm and polydispersity of 0.128 are obtained for MPEG₁₁₃‐b‐PCEMA₁₅‐b‐PHQHEMA₁₇ in THF/ethanol with a volume ratio (v/v) of 5/5. The PCEMA inner shell of the resulted micelles is photo‐crosslinked under UV radiation to give stabilized micelles. The complex reaction of the stabilized micelles with Zn(II) is investigated under different conditions to give zinc(II)‐bis(8‐hydroxyquinoline)(Znq₂)‐containing micelles. When the complex reaction is carried out in THF/ethanol (v/v = 5/5) or THF/toluene (v/v = 6/4) with zinc acetate, fluorescent Znq₂‐containing micelles are obtained without obvious change in diameters and morphologies. The fluorescent micelles exhibit green emission with λ_max at 520 nm. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1056–1064     

Heterodinukleare Komplexe: Synthese und Kristallstrukturen von [RuRh(μ‐CO)(CO)4(μ‐PtBu2)(tBu2PH)], [RuRh(μ‐CO)(CO)3(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] und [CoRh(CO)4(μ‐H)(μ‐PtBu2)(tBu2PH)]

Heterobinuclear Complexes: Synthesis and X‐ray Crystal Structures of [RuRh(μ‐CO)(CO)₄(μ‐P^tBu₂)(^tBu₂PH)], [RuRh(μ‐CO)(CO)₃(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)], and [CoRh(CO)₄(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)] [Ru₃Rh(CO)₇(μ₃‐H)(μ‐P^tBu₂)₂(^tBu₂PH)(μ‐Cl)₂] ( 2 ) yields by cluster degradation under CO pressure as main product the heterobinuclear complex [RuRh(μ‐CO)(CO)₄(μ‐P^tBu₂)(^tBu₂PH)] ( 4 ). The compound crystallizes in the orthorhombic space group Pcab with a = 15.6802(15), b = 28.953(3), c = 11.8419(19) Å and V = 5376.2(11) ų. The reaction of 4 with dppm (Ph₂PCH₂PPh₂) in THF at room temperature affords in good yields [RuRh(μ‐CO)(CO)₃(μ‐P^tBu₂)(μ‐dppm)] ( 7 ). 7 crystallizes in the triclinic space group P 1 with a = 9.7503(19), b = 13.399(3), c = 15.823(3) Å and V = 1854.6 ų. Moreover single crystals of [CoRh(CO)₄(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)] ( 9 ) could be obtained and the single‐crystal X‐ray structure analysis revealed that 9 crystallizes in the monoclinic space group P2₁/a with a = 11.611(2), b = 13.333(2), c = 18.186(3) Å and V = 2693.0(8) ų.     

Synthesis and Structural Characterization of Three New Inorganic ＂Host-gues＂ Polyoxomolybdates

Since two interesting inorganic “host‐guest” polyoxomolybdates 1 and 2 have been reported previously, we have now succeeded in selectively isolating three new acetated “host‐guest” polyoxomolybdates 3–5, which considerably extend the range of structures in the cyclic polyoxomolybdate catalogue. 3 crystallizes in the triclinic space group P‐1 with a = 1.22235(1) nm, b = 1.52977(2) nm, c = 1.54022(1) nm, a = 113.746(1)°, β = 96.742(1)°, γ = 101.564(1)°, V = 2.51892(4) nm³, Z =1, D_c = 2.568 g. cm^?3. 4 and 5 crystallize in the monoclinic system: P2(1)/n, a = 1.08298(2) nm, b = 1.54029(1) nm, c = 2.78893(5) nm, β =94.2730(10)°, V = 4.63929(12) nm³, Z = 2 and D_c = 2.671 g. cm^?3 for 4, and C2/c, a =2.59907(8) nm, b = 1.65992(3) nm, c = 2.28473(7) nm, β‐93.4370(10)°, V = 9.8392(5) nm³, Z = 4 and D_c = 2.556 g. cm^?3 for 5. The structures of 3, 4 and 5 consist of 18‐membered “host‐guest” polyoxoanions [ Na (X)₂| ∈ |(μ_3‐OH)₄Mo^y₈Mo^VI₁₀52(μ₂‐CH₃COO)₂]^?(R+9 (X = CH₃COO^?for 3, DMF for 4 and H₂O for 5), which are connected via Na* ions or hydrogen bonds into infinite extended frameworks.     

Volumetric Properties and Volumetric Interaction Parameters of the CsCl‐saccharides (D‐glucose,D‐fructose)‐water Solutions at 298.15 K

Densities have been measured for the CsCl‐saccharide (D‐glucose, D‐fructose)‐water systems at 298.15 K. These data were used to calculate the apparent molar volume of CsCl (V_φ,E) and the saccharides (V_φ,S), and the infinite dilution apparent molar volume V_φ,E⁰ and V_φ,S⁰ in the studied solutions. In addition, the standard transfer volume Δ_tV_φ,E⁰ of CsCl from water to aqueous saccharides solutions, and Δ_tV_φ,S⁰ of saccharides from water to CsCl solutions have been evaluated and discussed using the structural interaction model. The volumetric interaction parameters for CsCl with saccharide in water were obtained and analyzed by the group additivity principle and the stereochemistry of the saccharide molecules.     

Photodetachment dynamics from closed‐shell anions in the presence of a bichromatic field

I have studied the dynamics of photodetachment from closed‐shell anions in the presence of a two‐color (bichromatic) laser field. The electronic states of halide ions are modeled by a 1‐D Hamiltonian with a potential V(x) = ?V₀e. The two parameters V₀ and σ are fixed by requiring V(x) to reproduce the experimentally observed ground‐state ionization energy of the halide ions concerned. The potentials so generated are shown to support only one bound state in each case. The time‐dependent Fourier grid Hamiltonian method is used to follow the detachment dynamics with fairly high intensities of light. The environmental effects on the dynamics are sought to be modeled by allowing the well depth (V₀) to fluctuate randomly (V₀(t) = V₀[1 + ΔVR(t)]; R(t) randomly fluctuates between +1 and ?1 with time, when ΔV is fixed). The average detachment rate constants k_av are seen to increase with increase in the intensities of used bichromatic field. An alternative model potential, V(x) = ?V₀e^?σx, is also shown to yield similar results. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Synthesis and Crystal Structure of 4,7‐Diaryl‐5‐oxo‐4H‐benzo[b]pyran Derivatives

A green and convenient approach to the synthesis of a series of 4,7‐diaryl‐5‐oxo‐4H‐benzo[b]pyran derivatives from appropriate aromatic aldehydes and 5‐aryl‐1,3‐cyclohexanedione with malononitrile in the presence of dilute HCl as catalyst (30 mmol/L) is described. This method provides several advantages such as environmental friendliness, low cost, high yields, and simple work up procedure. The structures of all compounds were characterized by infrared (IR), mass spectrometry (MS), ¹H NMR, and elemental analysis. The crystal structure of trans/cis‐2‐amino‐3‐cyano‐7‐(4′‐methoxo‐phenyl)‐4‐phenyl‐5‐oxo‐4H‐benzo[b]pyran, g , was determined by single crystal X‐ray diffraction analysis. The crystal of compound g belongs to monoclinic with space group P 21/c, a = 8.477(3) nm, b = 18.948(6) nm, c = 24.915(7) nm, α = 90.00°, β = 107.388(11)°, γ= 90.00°, Z = 8, V = 3.819(2) nm³, R₁ = 0.0754, wR₂ = 0.2042.     

Modeling quantum dynamics of photodetachment from closed‐shell anions: Static versus fluctuating well‐depth models

The electronic states of halide ions are modeled by a one‐dimensional Hamiltonian with a potential V(x)=−V₀e. The two parameters V₀ and σ are fixed by requiring V(x) to reproduce the experimentally observed ground‐state ionization potentials of the halide ions concerned. The potentials so generated are shown to support only one bound state in each case. The time‐dependent Fourier grid Hamiltonian method is used to follow the ionization dynamics in monochromatic light of fairly high intensities. The total Hamiltonian, in the most general case, reads H(t)=P/2m−V₀e−ϵ₀s(t)ex sin(ωt). For pulsed fields [s(t)=sin²(πt/t_p)], the computed ionization rate constants are seen to increase with increase in the peak intensity (ϵ₀) of the electric field of light. The possibility of additional transient bound states being generated at the high intensities of light and its possible consequences on the observed ionization rates are explored. The environmental effects on the dynamics are sought to be modeled by allowing the well depth (V₀) to fluctuate randomly [V₀(t)=V₀+ΔVR(t); R(t) randomly fluctuates between +1 and −1 with time, ΔV is fixed]. The ionization rate constants (k_ϵ) are shown to be significantly affected by fluctuations in V₀ and pass through a well‐defined minimum in each case for a certain specified frequency of fluctuation. An alternative model potential V(x)=−V₀e^−σx is also shown to yield similar results. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 73: 469–478, 1999     

Synthesis and Crystal Structure of Two One—dimensional Chain Copper Complexes [Cu（TTA）2（4,4‘’—azpy）] and [Cu（TTA）2（3,3‘’—azpy）

Two copper complexes [Cu(TTA)₂(4,4′‐azpy)] (1) and [Cu‐(TTA)₂(3,3′‐azpy)] (2) (HTTA = 1,1,1‐trifluoro‐3‐(2‐thenoyl)‐acetone, 4,4′‐azpy = 4,4′‐azobispyridine, 3,3′‐azpy = 3,3′‐azobispyridine) were synthesized and characterized. The crystal structures were determined by X‐ray diffraction analysis. The crystal 1 belongs to triclinic with space group P1 , a = 0.8515(2) nm, b = 0.9259(2) nm, c = 0.9468(2) nm, a = 66.126(9)°, β = 79.667(9)°, γ = 90.13(1)°, Z = 1, V = 0.6692(2) nm³, D_c = 3.425 g/cm³, γ = 2.113 mm^?1, F(000) = 694, R₁ = 0.0594, wR₂ = 0.1499. The crystal 2 belongs to monoclinic with space group P2₁/c, a = 1.0661(2) nm, b = 1.4296(3) ran, c = 1.0041(3) nm, β = 114.50(3)°, V = 1.3926(5) nm³, Z = 2, D_c = 1.646 g/ cm³, μ = 1.015 mm^?1, F(000) = 694, R₁, = 0.0535, wR₂ = 0.1113. In the crystals of complexes 1 and 2, the copper atoms have distorted octahedral symmetry. The two compounds possess very similar one‐dimensional linear chains linked through the rodlike 4,4′‐azpy ligands or 3,3′‐azpy ligands.     

Synthesis of 1‐Methyl‐3‐aryl‐substituted Titanocene and Zirconocene Dichlorides and Crystal Structure of Bis[η5‐1‐methyl‐3‐(α, α‐dimethylbenzyl) cyclopentadienyl] titanium Dichloride

The syntheses of a series of l‐methyl‐3‐aryl‐substituted titanocene and zirconocene dichlorides are reported. These complexes are synthesized by the reaction of 2‐ and 3‐methyl‐6, 6‐dimethylfulvenes (1:4) with aryllithium, followed by the reaction with TiCl₄·2THF, ZrCl₄ and (CpTiCl₂)₂O respectively, to give complexes 1–5. The complex [η⁵‐1‐methyl‐3‐(α, α‐dimethylbenzyl) cyclopentadienyl] titanium dichloride has been studied by X‐ray diffraction. The red crystal of this complex is monoclinic, space group P2_t/C with unit cell parameters: a =6.973(6) × 10^?1 nm, b =36.91(2) × 10^?1 nm, c = 10.063(4) × 10^?1 nm, α=β= γ = 93.35(5)°, V = 2584(5) × 10^?3 nm³ and Z = 4. Refinement for 1004 observed reflections gives the final R of 0.088. There are four independent molecules per unit cell.     

Synthesis, Structure and Biological Activities of S-[α-（ 4-Methoxyphenylcarbonyl ）-2-（1,2,4-triazole-l-yl） ethyl-N, N-dime-thyldithiocarbamate

The title compound was prepared by reaction of N, N‐dimethyldithiocarbamate sodium with l‐bromo‐l‐(4‐methoxyphenylcarbonyl)‐2‐(1, 2, 4‐triazole‐l‐yl) ethane. Its crystal structure has been determined by X‐ray diffraction analysis. The crystal belongs to triclinic with space group Pī, a = 0.7339(2) nm, b = 1.1032(2) nm, c = 1.1203(2) nm, a = 90.27(3)°, β = 102.03(3)°, γ = 104.91(3)°, Z=2, V = 0.8556(3) nm³, D_c = 1.360 g/cm³, μ =0.325 mm^?1, F(000)=368, final R₁ =0.0475. The planes of 4‐methoxybenzyl group and triazole ring are nearly perpendicular to each other. The dihedral angle is 83.97°. There is an obvious π‐π stacking interaction between the molecules in the crystal lattice. The results of biological test show that the title compound has fungicidal and plant growth regulating activities.     

Validated Method for the Simultaneous Determination of Gemifloxacin and H2‐receptor Antagonists in Bulk,Pharmaceutical Formulations and Human Serum by RP‐HPLC; In‐vitro Applications

Simple, isocratic and rapid RP‐HPLC method has been developed for the simultaneous analysis of gemifloxacin and H₂‐receptor antagonists i.e. Cimetidine, Famotidine and Ranitidine, in bulk, pharmaceutical formulation and human serum. Separation was achieved on the RP‐Mediterranea column [C18 (250 × 4.6 mm, 5 μ)] at ambient temperature using mobile phase consisting of acetonitrile: methanol: water (20:28:52 v/v/v pH 2.8 adjusted by phosphoric acid). Flow rate was 1.0 mL/min with an average operating pressure of 180 kg/cm². Gatifloxacin (GATI) was used as an internal standard (IS). Quantitation was achieved with UV detection at 221, 256 and 267 nm, respectively. Linear calibration curves, at concentration ranges of 0.05‐37.5 μgmL^‐L with a correlation coefficient of ±0.9994. The detection and quantification limits were in the ranges of 0.023‐0.250 μgmL^‐L and 0.071‐0.756 μgmL^‐L, respectively. Friedman's and Student's t‐test were applied to correlate these results. Method was validated in terms of selectivity, linearity, precision, robustness, recovery, limits of detection and quantitation and is applicable to the routine analysis of GFX and H₂‐receptor antagonists, alone or in combination.     

Green synthesis and crystal structure of 4,7‐diaryl‐2‐oxo(thio)‐1,2,3,4,5,6,7,8‐octahydroquinazoline‐5‐one derivatives

A green and convenient approach to the synthesis of novel 4,7‐diaryl‐2‐oxo(thio)‐1,2,3,4,5,6,7,8‐octahydroquinazoline‐5‐one derivatives from appropriate aromatic aldehydes and 5‐aryl‐1,3‐cyclohexanedione with urea or thiourea in the presence of dilute HCl as catalyst in water is described. This method provides several advantages such as environmental friendliness, low cost, high yields, and simple workup procedure. The structures of all compounds were characterized by elemental analysis, IR, MS, and ¹H NMR. The crystal and molecular structure of 4‐(4′‐chlorophenyl)‐7‐(4′‐methoxyphenyl)‐1,2,3,4,5,6,7,8‐octahydroquinazoline‐2,5‐dione 5m have been determined by single crystal X‐ray diffraction analysis. The crystal of compound 5m belongs to monoclinic with space group P‐2₁/c, a = 1.4353 (4) nm, b = 1.4011 (4) nm, c = 0.9248 (3) nm, α = 90.00°, β = 101.242 (6)°, γ = 90.00°, Z = 4, V = 1.8241 (9) nm³, R₁ = 0.0448, and wR₂ = 0.1022. J. Heterocyclic Chem., (2011).     

4- (4,6-二甲基嘧啶-2-基)-3-硫代脲酸甲酯的合成晶体结构及量子化学研究

4-（4,6-Dimethylpyrimidin-2-yl）-3-thio-allophanic acid methyl ester was synthesized with mixing 2-amino-4,6- dimethylpyrimidine, potassium thiocyanate and methyl chloroformate in ethyl acetate. Single crystals suitable for X-ray diffraction measurement were obtained by recrystallization from dimethylformamide at room temperature. The crystal belongs to monoclinic symmetry with space group C2/m, and crystal parameters of a= 1.7537（5） nm, b= 0.6759（2） nm, c=1.1148（3） nm, β=118.557（4）°, V=1.1605（6） nm^3, Z=4, De= 1.375 g/cm^3,μ=0.271 mm^-1, F（000）=504, and 1519 [1〉2σ（I）] observable independent reflections were used for the determination and refmement of the crystal structures with final R1 of 0.0372 and wR2 of 0.0992. The theoretical investigation of the title compound was carried out with DRT-B3LYP/6-311G, HF/6-311G and MP2/6-311G methods, and the atomic net charges and the population were discussed.     

Gold‐Nanoparticle‐Loaded Carbonate‐Modified Titanium(IV) Oxide Surface: Visible‐Light‐Driven Formation of Hydrogen Peroxide from Oxygen

Gold nanoparticle‐loaded rutile TiO₂ with a bimodal size distribution around 10.6 nm and 2.3 nm (BM‐Au/TiO₂) was prepared by the deposition precipitation and chemical reduction (DP‐CR) technique. Visible‐light irradiation (λ>430 nm) of the BM‐Au/TiO₂ plasmonic photocatalyst yields 35 μm H₂O₂ in aerated pure water at irradiation time (t_p)=1 h, and the H₂O₂ concentration increases to 640±60 μm by the addition of 4 % HCOOH as a sacrificing electron donor. Further, a carbonate‐modified surface BM‐Au/TiO₂ (BM‐Au/TiO₂‐CO₃^2?) generates a millimolar level of H₂O₂ at t_p=1 h with a quantum efficiency (Φ) of 5.4 % at λ=530 nm under the same conditions. The recycle experiments confirmed the stable performance of BM‐Au/TiO₂.