Solid-phase luminescence determination of tetracycline in bottled water using chemically modified silica

Possibility of using chemically modified silica (CMS) with covalently immobilized sulfonic and ethylenediaminetriacetate (ED3A) groups for the adsorption preconcentration and extraction of tetracycline (TC) from aqueous solutions is studied. The conditions of complex formation by europium(III) ions on the surface of these adsorbents are optimized. The effect of citrate and Eu³⁺ ions on the luminescence intensity of the Eu–TC complex is shown. The luminescence properties of SiO₂ED3AEu and SiO₂SO₃HEu systems with tetracyclines are studied depending on the acidity of the medium, time of phase contact, the ratio of the volume of the solution to the weighed portion of the adsorbent, and concentrations of the adsorbed substances. It is found that tetracycline is quantitatively extracted by CMS as a complex with europium(III) ions in pH range 6.5–8.0; adsorption capacity to tetracycline in the Henry region is as high as 0.07–0.09 mmol/g and partition coefficients are 10³–10⁴ mL/g. A procedure is developed for the solid-phase luminescence determination of tetracycline using SiO₂SO₃HEu and SiO₂ED3AEu systems with limits of detection of 0.8 and 2.0 nM, respectively; linearity range is 1 × 10^–9–1 × 10^–5 M. The procedure is tested in the analysis of model mixtures and samples of bottled water.     

The role of copper(II) ions in the oxidation of 5-hydroxy-6-methyluracil in the ground and electronically excited states with molecular oxygen in aqueous solutions

A spectral fluorescence study of photoinduced reactions in aqueous solutions has been carried out in order to examine the mechanisms of the oxidation of 5-hydroxy-6-methyluracil (I) in the ground and electronically excited states by molecular oxygen in the presence of copper(II) chloride. It has been found that 5,5,6-trihydroxy-6-methylpyrimidine-2,4-dione (II) is formed upon the photolysis of I. The spectral parameters (λ_max) and the quantum yields (φ) of fluorescence (FL) of compounds I (φ = 8 × 10^–4; λ_max = 362 nm) and II (φ = 17 × 10^–4; λ_max = 306, 330 nm) have been determined. A reaction scheme was proposed, according to which the photooxidation of I occurs through the steps of the generation of the radical cation I ^?+ and the superoxide anion О ₂ ^?- with the subsequent formation of 5,5,6-trihydroxy-6-methylpyrimidine-2,4-dione. The catalytic and inhibitory effects of Cu(II) ions on the oxidation of 5-hydroxy-6-methyluracil in the ground and electronically excited states, respectively, by the oxygen radical anion О ₂ ^?- have been revealed.     

Synthesis and properties of novel stilbene-twelve alkyl quaternary ammonium salts as antibacterial optical whitening agents

Four novel stilbene-twelve alkyl quaternary ammonium salts 5a–d were synthesized. All synthesized compounds were characterized by FT-IR, ¹H-NMR and elemental analysis. Compounds 5a–d showed efficient whitening effect on cotton fiber and high fastness. Furthermore, compound 5c showed better stability to light than C186 in aqueous solution. The preliminary biological experiment demonstrated compounds 5a–d possessed significant antibacterial activities. Among them, compound 5d turned out to be the most active compound against Candida albicans with MIC₅₀ 4 μg/mL as well as E. coli with MIC₅₀ 16 μg/mL.     

μ<Subscript>2</Subscript>-Oxobis[(aroxo)tris(<Emphasis Type="Italic">para</Emphasis>-tolyl)antimony]: Synthesis and Structure

µ₂-Oxobis[(2,4,6-tribromophenoxo)tris(para-tolyl)antimony] (I), µ₂-oxobis[(2,3,4,5,6-pentachlorophenoxo) tris(para-tolyl)antimony] (II), and µ₂-oxobis(2,4-dinitrophenoxo)tris(para-tolyl)antimony] (III) have been synthesized with high yields by the reaction of tris(para-tolyl)antimony with 2,4,6-tribromo-, 2,3,4,5,6-pentachloro-, and 2,4-dinitrophenol, respectively, in ether in the presence of tert-butylhydroperoxide. The Sb atoms in complexes I, II, and III have a distorted trigonal bipyramidal coordination with the aroxyl ligands and the bridging oxygen atom in axial positions. The central Sb–O–Sb moiety in molecules of complexes I–III has an angular structure.     

Gold nanoparticles,capped by carboxy-calix[4]resorcinarenes: effect of structure and concentration of macrocycles on the nanoparticles size and aggregation

Small (d_core?≈?2–5 nm) well-dispersed gold nanoparticles (AuNPs) stabilized by amphiphilic octacarboxy-calix[4]resorcinarenes with different substituents on the lower rim—methyl (С₁–CR), pentyl (С₅–CR) and undecyl (С₁₁–CR)—in an aqueous solution were obtained. The nanoparticles were studied by spectrophotometry, transmission electron microscopy, FTIR-spectroscopy, dynamic light scattering, small angle X-ray scattering and X-ray powder diffraction. The influence of HAuCl₄/macrocycle ratio during the synthesis on the nanoparticles size and aggregation only for weakly associated С₁–CR and С₅–CR was achieved. The self-association effect of С₁₁–CR on the nanoparticles stabilization is found. The existence of gold in the form of crystallites and their average sizes were defined. The average nanoparticle sizes were determined and the structure of macrocyclic shells on the surface of nanoparticles in an aqueous solution was proposed. The formation of cooperative calix[4]resorcinarene associates on the AuNPs surface due to the multiple supramolecular interactions leads to the creation of functional gold nanoparticles.     

Crystal structure,luminescent sensing and photocatalytic activity of a multifunctional hydrazone-based zinc(II) coordination polymer

A Zn(II)-based coordination polymer [Zn₃(L)₂(dpp)₂]_n (1) has been solvothermally constructed from a combination of a multifunctional Schiff base 3,5-dibromosalicylaldehyde salicylhydrazone (H₂L) and 1,3-di(4-pyridyl)propane (dpp). The photoluminescence properties of the complex have been exploited to use 1 as a dual detection probe for the selective sensing of Cu²⁺ and 2,4,6-trinitrotoluene (TNT) in the aqueous phase from among a variety of cations and a pool of aromatic nitro compounds, respectively. Competitive fluorometric experiments involving mixtures of cations or nitro compounds established 1 as an efficient and selective sensor for both Cu²⁺ and TNT in aqueous solutions. The limits of detection for Cu²⁺ and TNT in aqueous solutions were found to be 1.05 and 49.9 μM, respectively. Additionally, the activity of complex 1 as a photocatalyst for degradation of rhodamine B has been investigated.     

New Thiocyanatocadmate and Halo-thiocyanatocadmates Modified by Imidazole or Triazole Derivatives: Synthesis,Structural Characterization,and Photoluminescence Property

At pH 2, the simple room-temperature self-assemblies between Cd²⁺ salts, SCN^? and organic bases created one new thiocyanatocadmate as [H₂(L1)][Cd₂(SCN)₆] (L1?=?1,4-bis(2-methyl-1H-imidazol-1-ylmethyl)benzene) 1, and two new halo-thiocyanatocadmates as [H₂(L2)][CdI₂(SCN)₂]·H₂O (L2?=?3,5-bis (4-pyridyl)-1,2,4-triazole) 2, and [CdCl(SCN)(L3)] (L3?=?3-pyrazinyl-1,2,4-triazole) 3. X-ray single-crystal diffraction analysis reveals that (a) in 1, with H₂(L1)²⁺ as the countercation, the SCN^? groups tri-bridge the Cd²⁺ centers into a 1-D chained thiocyanatocadmate; (b) 2 is only a mononuclear iodo-thiocyanatocadmate, and H₂(L2)²⁺ acts as the countercation. But via the π···π and N_pyridyl–H···N_SCN interactions, H₂(L2)²⁺ and CdI₂(SCN) ₂ ^2? aggregate together to form a 1-D supramolecular tube. Amongst the tubes, a chained water cluster with a zig-zag shape is observed; (c) 3 is an organically extended chloro-thiocyanatocadmate. Note that the report on this type of material is rather rare. It possesses a 3-D network structure with a dia topology, in which a castellated CdCl⁺ single chain is observed. L3 and Cl^? act as a mixed bridge, whereas SCN^? just serves as a terminal ligand in 3. The photoluminescence analysis indicates that the title compounds 1–3 all emit light (green light for 1, blue light for 2 and 3), which should be attributed to the ligand-centered electronic excitations.     

Hydrides,alkalides, and halides of calcium metal chain: electronic structure and NLO property

The ground state structure and stability of linear calcium chains Ca _n X ₂ , XCa _n Y (X,Y?=?H, Li, Na, K; n?=?1–8), Ca ₈ Y ₂ , and Ca ₈ XY (X?=?H, K; Y?=?F, Cl, Br) have been calculated at the B3LYP/6-311++G(d,p) level. The hyperpolarizabilities of these metal complexes are calculated by employing B2PLYP, BHHLYP, and CAM-B3LYP functionals. The electron correlation at the MP2, CCSD, and CCSD(T) levels and the effect of basis set on the second hyperpolarizability of some representative molecules are also examined. Among the chosen functionals, the CAM-B3LYP method with POL basis set shows fair agreement with the CCSD(T)/POL γ _zzzz . The chosen species are found to be sufficiently stable. The dialkalide calcium chains possess larger magnitude of linear polarizability and second hyperpolarizability compared to dihydrides and dihalides. The highest value of first hyperpolarizability has been obtained for the complex Ca ₈ HK. Among the investigated metal complexes, the substantially larger second hyperpolarizability is obtained for alkalides, Ca ₈ LiK, Ca ₈ NaK, Ca ₈ K ₂ in which charge transfer is significantly larger. The calculated transition energy and transition moment associated with the most crucial electronic transition play a significant role in modulating the magnitude of hyperpolarizabilities. The TD-CAMB3LYP calculated transition energy shows increasing red shift following the power law ?E _ng  =?bn ^?c with c value varying in the order Ca _n H ₂ >> Ca _n Li ₂ = Ca _n Na ₂ ≥ Ca _n K ₂ . The most interesting feature is that no saturation limit of γ can be realized on increasing the length of calcium metal chains but ?E _ng approaches to a limiting value for n?→?∞.     

Molecular and crystal structure and stability of triiodides of quinolinium derivatives

1,2,4-Trimethylquinolinium triiodide (I) and 1-ethyl-2,4-dimethylquinolinium (II) triiodide are synthesized and studied by X-ray diffraction analysis. The layered structures of compounds I and II are formed by mixed stacks of cations and anions. Crystals of compound II consist of two types of anionic chains. The coordinating ability of the corresponding organic iodides toward molecular iodine in chloroform solutions is studied.     

Crystal structure,spectroscopic and thermal properties of copper(II) and manganese(II) coordination polymers based on triazole-benzoic acid ligands

Two transition metal coordination polymers {[Cu(tba)₂(H₂O)]·2H₂O} _n (1) and {[Mn(Htta)₂(H₂O)₂]·2H₂O} _n (2) {Htba = 3-[1,2,4]triazol-1-yl-benzoic acid, H₂tta = 2-[1,2,4]triazol-1-yl-terephthalic acid} have been synthesized under solvothermal conditions. Both complexes have been characterized by single-crystal X-ray diffraction, X-ray powder diffraction, elemental analysis and FTIR spectroscopy. Complex 1 has a 1-D chain structure in which Cu(II) atoms are doubly bridged by tba^? ligands, which is further stabilized by hydrogen bonding and π–π stacking interactions to give a 3-D supramolecular framework. In complex 2, Mn(II) atoms are doubly bridged by Htta^? ligands to form 1-D chains, which are further connected by intermolecular hydrogen bonds to form a 3-D supramolecular framework. The electronic spectra and thermal behaviors of complexes 1 and 2 are also reported.     

Synthesis,antibacterial activity,and fluorescence properties of a novel series from [2,4-dioxochromen-3(4<Emphasis Type="Italic">H</Emphasis>)methyl]amino acid

A new solvent-free method for synthesis of starting compounds 2,4-dioxochromen-3(4H)methyl amino acetic acid derivatives 1a–e via a green approach is reported. Also, the behavior of compound 1a towards various nitrogen nucleophiles such as primary amines, hydrazine hydrate, and hydroxylamine hydrochloride to give corresponding compounds 2–4 was studied. Furthermore, chlorination of compound 1a using a mixture of PCl₅/POCl₃ to yield acid chloride derivative 5 and the reaction of the latter compound 5 with various amino acids to obtain dipeptide compounds 6a–e are described. Moreover, cyclization of compound 1a in alkaline medium to afford dihydrochromeno[3,4-c]pyrrole-1-carboxylic acid 7 and cyclization of 6b in acidic medium, namely Ac₂O, to yield piperazine derivative 8 are reported. Also, reaction of compound 1a with maleic anhydride in dioxane to afford Diels–Alder adduct 9, which posteriorly reacted with hydrazine hydrate to give 10, was investigated. Most of the newly synthesized compounds were screened against Gram-positive and Gram-negative bacteria, with compound 5 exhibiting the maximum inhibition zone towards all four types of bacteria. In addition, the absorption and fluorescence emission of some of the substituted coumarins were studied in dioxane, revealing that the substituents altered both the absorption and fluorescence emission maxima.     

The role of substituents in a bidentate <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-chelating ligand on the substitution of aqua ligands from mononuclear Pt(II) complexes

The rate of substitution of aqua ligands from three mononuclear platinum(II) complexes, namely [Pt{2-(pyrazol-1-ylmethyl)pyridine}(H₂O)₂](ClO₄)₂, [Pt(H ₂ Py)]; [Pt{2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine}(H₂O)₂](ClO₄)₂, [Pt(dCH ₃ Py)] and [Pt{2-[(3,5-bis(trifluoromethyl)pyrazoly-1-ylmethyl]pyridine}(H₂O)₂](ClO₄)₂, [Pt(dCF ₃ Py)] by thiourea, N,N-dimethylthiourea and N,N,N′,N′-tetramethylthiourea, was studied in aqueous perchloric acid medium of constant ionic strength. The substitution reactions were investigated under pseudo-first-order conditions as a function of nucleophile concentration and temperature using UV/Visible and stopped-flow spectrophotometries. The observed pseudo-first-order rate constants, \( k_{{{\text{obs }}\left( {1/2} \right)}} \), for the stepwise substitution of the first and second aqua ligands obeyed the rate law: \( k_{{{\text{obs}}\left( {1/2} \right)}} = k_{{2 \left( { 1 {\text{st/2nd}}} \right)}} \left[ {\text{Nu}} \right] \). The first substitution reaction takes place trans to the pyrazole ligand, while the second entering nucleophile is stabilised at the reaction site trans to the pyridine ligand. The rate of substitution of the first aqua ligand from the complexes followed the order: Pt(dCF ₃ Py) > Pt(H ₂ Py) > Pt(dCH ₃ Py), while that of the second was Pt(H ₂ Py) ≈ Pt(dCF ₃ Py) > Pt(dCH ₃ Py). Lower pK _a values were found for the deprotonation of the aqua ligand cis to the pyrazole ring. Density functional theory calculations were performed to support the interpretation of the experimental results.     

Directed assembly of cobalt(II) 1-H-indazole-3-carboxylic acid coordination networks by bipyridine and its derivatives: structural versatility,electrochemical properties,and antifungal activity

This paper describes the hydrothermal synthesis, full characterization, and architectural diversity of three intriguingly bioactive cobalt–organic frameworks, namely, 3D [Co(HL ^? )₂(BPY)] _n ·4nH₂O (1), 2D [Co(HL ^? )₂(BPE)] _n (2), and 2D [Co(HL ^? )₂(DPP)] _n (3) coordination polymers, synthesized through a mixed ligand strategy using H ₂ L (1-H-indazole-3-carboxylic acid) as a main structural block and the flexible bipyridine and its derivatives (BPY = 4,4′-bipydine, BPE = 1,2-bis(4-pyridyl)ethane, DPP = 1,3-bis(4-pyridyl)propane) as auxiliary ligand sources. Complexes 1–3 were isolated as air stable and slightly soluble crystalline solids and characterized using elemental analysis, FT-IR, electrochemical technique, thermogravimetric analysis, powder X-ray diffractometer, and single-crystal X-ray crystallography. The bipyridine derivatives played key roles in defining the structural space group and dimensionality feature of the obtained networks. The abundant H-bonding and π–π stacking interactions in complexes 1–3 gave rise to their intricate metal–organic structures of 3D (1), 2D (2), and 2D (3). In addition, the solutions of complexes 1–3 showed profound antifungal activities against the selected strain of Colletotrichum musae compared with the controlled group using benomyl as a traditional agrochemical fungicide.     

Improved synthesis and low-temperature performance of a series of saturated α-branched fatty acids

Five saturated α-branched fatty acids, also known as Guerbet acids, including α-propylhexyl acid (G ₁ ), α-butylhexyl acid (G ₂ ), α-propyloctyl acid (G ₃ ), α-butyloctyl acid (G ₄ ), and α-hexyloctyl acid (G ₅ ), were synthesized in high yields by four-step reaction. Colorless, almost odorless, and oily products were obtained with high purity, whose structures were confirmed by GC, ¹H/¹³C NMR, and ESI–MS characterization. G ₁ , G ₃ , and G ₄ had pour points lower than ?60 °C, while G ₂ and G ₅ showed higher pour points (?42 °C and 6 °C, respectively) because of their molecular symmetry. Considering the low-temperature properties, G ₁ , G ₃ , G ₄ , and even G ₂ held great potential applications in the lubricant and oilfield.     

Synthesis and structures of organoantimony and organobismuth derivatives of 4-sulfophenol and 2,4-disulfophenol

Tetraphenylbismuth 4-hydroxybenzenesulfonate (I) and tetraphenylantimony 4-hydroxybenzenesulfonate (II) are synthesized in yields up to 80% by the reaction of pentaphenylbismuth and pentaphenylantimony, respectively, with 4-sulfophenol. Compounds I and II are also prepared by the ligand redistribution reaction from pentaphenyl compounds of bismuth and antimony and triphenylbismuth bis(4-hydroxybenzenesulfonate) and triphenylantimony bis(4-hydroxybenzenesulfonate), respectively, in yields up to 87%. The recrystallization of compounds I and II from water gives crystalline hydrates Ph₄BiOSO₂C₆H₄(OH-4) · H₂O (III) and Ph₄SbOSO₂C₆H₄(OH-4) · H₂O (IV). Pentaphenylbismuth and pentaphenylantimony react with 2,4-disulfophenol in acetone, regardless of the ratio of the starting reactants, to form bis(tetraphenylbismuth) 4-hydroxybenzene-1,3-disulfonate (V) and bis(tetraphenylantimony) 4-hydroxybenzene-1,3-disulfonate (VI) in yields up to 74%. According to X-ray diffraction data, coordination of the bismuth atoms in compound I is trigonal-bipyramidal with the axial oxygen atom of the 4-hydroxybenzenesulfonate group (Bi···O 2.764 Å). In compound II, coordination of the Sb atom is tetrahedral (CSbC angles 106.2°–112.3°). In crystal III, the distances between the central atom and the nearest oxygen atoms of the arenesulfonate group and the hydrate water molecule are 3.094 and 3.125 Å, respectively. Crystals V and VI consist of doubly charged anions of 2,4-disulfophenol and several distorted tetrahedral cations of tetraphenylbismuthonium (CBi(1)C, CBi(2)C angles and Bi(1)-C, Bi(2)-C bond lengths vary in the intervals 102.1°–122.7°, 105.4°–114.0° and 2.103–2.230, 2.187–2.209 Å, respectively) and tetraphenylantimonium (CSb(1)C, CSb(2)C angles and Sb(1)-C, Sb(2)-C bond lengths 106.3°–112.2°, 101.3°–122.4° and 2.095–2.110, 2.092–2.123 Å, respectively). The Bi(1) and Sb(2) atoms are coordinated by one of the oxygen atoms of the 2,4-disulfophenol anions (distances Bi(1)···O(3) 2.803, Sb(2)···O(1), 2.704 Å).     

Regioselective Friedel–Crafts deacylations of polycyclic aromatic ketones in the pyrene series

1,3,6,8-tetrabenzoylpyrene (1,3,6,8-Bz ₄ PY) and 1,3,6-tribenzoylpyrene (1,3,6-Bz ₃ PY) were synthesized and their crystal structures were determined. The Friedel–Crafts deacylations in PPA of 1,3,6,8-Bz ₄ PY (at 120–200 °C) and of 1,3,6-Bz ₃ PY (at 80–160 °C) have been studied. The mono-deacylation of 1,3,6-Bz ₃ PY was regioselective and led to three dibenzoylpyrenes in the following order of relative amounts: 1,8-Bz ₂ PY > 1,6-Bz ₂ PY > 1,3-Bz ₂ PY. 1,3,6,8-Bz ₄ PY was resistant to deacylation at 120–160 °C. The deacylations of 1,3,6,8-Bz ₄ PY at 200 °C gave the polycyclic aromatic ketone (PAK) 8H-dibenzo[def,qr]chrysen-8-one (DBCO) via an intramolecular Scholl reaction. Two plausible pathways of the Friedel–Crafts deacylation of 1,3,6,8-Bz ₄ PY to give DBCO are proposed. A density functional theory (DFT) B3LYP/6-311(d,p) computational study of the conformational spaces of 1,3,6-Bz ₃ PY and 1,3,6,8-Bz ₄ PY was performed. The estimated energy barriers of formation of dibenzoylpyrenes by deacylation of 1,3,6-Bz ₃ PY increase in the following order: 1,8-Bz ₂ PY < 1,3-Bz ₂ PY < 1,6-Bz ₂ PY. A mechanism of the Friedel–Crafts deacylation of 1,3,6-Bz ₃ PY in PPA via the respective O-protonated ketone and σ-complexes is presented.     

Substitution of aqua ligands from <Emphasis Type="Italic">cis</Emphasis>-platinum(II) complexes bearing 2-(phenylthiomethyl)pyridine spectator ligands

Cis-Pt(II) complexes, namely [Pt{2-(phenylthiomethyl)pyridine}(H₂O)₂](CF₃SO₃)₂ Pt(pyS ^Ph ), [Pt{2-(4-tert-butylphenylthiomethyl)pyridine}(H₂O)₂](CF₃SO₃)₂ Pt(pyS ^{Ph( t -But)} ) and [Pt{2-(4-fluorophenylthiomethyl)pyridine}(H₂O)₂](CF₃SO₃)₂ Pt(pyS ^PhF ), were synthesised and characterised. The pK _a1 and pK _a2 values of the complexes were determined titrimetrically. Substitution of the aqua ligands from these complexes by thiourea nucleophiles was studied at a pH of 2 and ionic strength of 0.1 M under pseudo-first-order conditions using stopped-flow and UV–visible spectrophotometric techniques. Substitution of the aqua ligands depends on both the nature and concentration of the incoming ligand, with low enthalpy and negative entropy of activation values. Substitution of the first and second aqua ligands occurs sequentially and fits the rate laws: k _{obs (1/2)} = k _(1/2) [Nu]. The second-order rate constant, k ₁, relates to the substitution trans to sulphur, while k ₂ is the second-order rate constant for the subsequent substitution of the aqua ligand trans to pyridine. The rate of substitution of the first aqua ligand decreases in the order: Pt(pyS ^{Ph( t -But)} ) > Pt(pyS ^PhF ) > Pt(pyS ^Ph ), while that of the second decreases in the order: Pt(pyS ^{Ph( t -But)} ) > Pt(pyS ^Ph ) > Pt(pyS ^PhF ), reflecting the influence of the substituents on the spectator ligands. ¹⁹⁵Pt NMR spectra of aged solutions of complexes with the thiourea nucleophile suggest a subsequent but rapid concentration-independent ring opening of the N,S-bidentate ligand to form a PtS ₄ species. The crystal structure of Pt(pyS ^PhF )Cl ₂ was elucidated by X-ray diffraction analysis.     

Structure of binuclear platinum(III) acetamidate complexes in solutions as probed by <Superscript>195</Superscript>Pt, <Superscript>13</Superscript>C,and <Superscript>1</Superscript>H NMR spectroscopy

¹⁹⁵Pt, ¹H, and ¹³C NMR spectroscopy was used to study the structure of binuclear platinum(III) acetamidate complexes with 1,10-phenanthroline and 2,2′-bipyridine ligands [Pt₂(phen)₂(acam)₄](NO₃)₂ (1) and [Pt₂(bipy)₂(acam)₄](NO₃)₂ (2) in aqueous solutions. The ¹⁹⁵Pt NMR spectra of solutions of complexes 1 and 2 in D₂O exhibit two signals with satellites due to the ¹⁹⁵Pt–¹⁹⁵Pt spin-spin coupling (¹ J(Pt–Pt) ≈ 6345 Hz), whereas their ¹H and ¹³C NMR spectra contain four sets of signals for the protons and the carbon atoms of the heterocyclic and acetamidate ligands. The signals were assigned using the COSY, NOESY, and HSQC/ HMBC experiments and comparing the coordination shifts of the signals for the protons of heterocycles. These data allowed us to draw a conclusion that binuclear complexes 1 and 2 in solution have a head-to-head structure with nonequivalent platinum(III) atoms (coordination cores PtN₅ and PtN₃O₂), the axial-equatorial coordination of the bidentate heterocyclic molecules, and two bridging and two terminal acetamidate ligands.     

Synthesis and in vitro cytotoxic evaluation of some novel hexahydroquinoline derivatives containing benzofuran moiety

A series of new ethyl 4-(2-(benzofuran-2-yl)-4-substituted-1,4,5,6,7,8-hexahydroquinolin-1-yl)-benzoate 3a–c was synthesized by Michael condensation of benzofuran chalcones 1a–c and cyclohexanone to give 2-(2-benzofuranyl)-4-substituted-5,6,7,8-tetrahydro-4-H -chromene 2a–c, followed by reaction of the latter with ethyl 4-aminobenzoate. Condensation of 3a–c with different amines afforded the corresponding amides 4a–e. On the other hand, upon treatment compounds 3a–c with hydrazine hydrate gave the benzohydrazide derivatives 5a–c. The reaction of compounds 5a–c with different thio/isocyanate gave the corresponding thiosemicarbazide and semicarbazide derivatives 6a–c. Meanwhile compounds 5a–c were reacted with ethyl cyanoacetate and different β-dicarbonyl compounds such as acetyl acetone, ethyl acetoacetate, and diethyl malonate to afford pyrazolyl derivatives 7a, b; 8a, b; 9a, b; and 10a–c, respectively. Moreover, 5a–c were reacted with carbon disulfide to synthesize the corresponding oxadiazolyl derivatives 11a–c, while their condensation with different aromatic aldehydes gave the corresponding Schiff bases 12a–d. Cytotoxic evaluation of some of the newly synthesized compounds against human hepatocellular carcinoma cell lines (HepG-2) revealed that the tested compounds produce promising inhibitory effect against the growth of HepG-2 cells with IC₅₀ values ranged from 11.9 to 19.3 µg/mL.     

Tetraphenylphosphonium carboxylates and sulfonates. Synthesis and structure

The reaction of the pentaphenyphosphorus solvate Ph₅P·1/2PhH (I) with carboxylic and sulfonic acids was used to synthesize tetraphenylphosphonium carboxylates Ph₄POC(O)R, R = C₆H₄(2-OH) (II), C₆H₄ (2-COOH) (III), H (IV), Me (V), CCl₃ (VI), Ph (VII), PhCH=CH (VIII), CH₂CH₂C(O)OH (IX), CH=CHC(O) OH(X), and CH₂C(O)OH (XI) and tetraphenylphosphonium sulfonates Ph₄POSO₂Ar, Ar = Ph (XII), C₆H₄Me₄ (XIII), and C₆H₃(-COOH)(4-OH) (XIV). Compound XII was also prepared from compound I and SO₃ in benzene. According to X-ray diffraction data, the crystals of I contain two types of crystallographically independent molecules with a slightly distorted trigonal-bipyramidal configuration [Ia, CaxPCax 178.44(8)°, P- C_ax 1.985(2), 1.987(2) Å, P-C_eq 1.854(2), 1.846(2), 1.840(2) Å; Ib, C_axPC_ax 178.45(9)°, P-C_ax 1.980(2), 1.975 (2) Å, P-C_eq 1.840(2), 1.846(2), 1.854(2) Å]. In the cations of compounds II, III and XIV, the coordination of the phosphorus atom is tetrahedral [CPC angle: II, 106.2(2)?111.6(1)°; III, 104.01(6)?113.03(6)°; XIV, 107.54 (6)?112.79(6)°]; the anions contain intramolecular O-H?O hydrogen bonds between the hydroxyl hydrogen atom and carboxyl oxygen atom (II, 1.34; III, 1.23; and XIV, 1.83 Å).