Complexes of tantalum with triaryloxides: Ligand and solvent effects on formation of hydride derivatives

A family of tantalum compounds supported by the triaryloxide [R-L]³⁻ ligands are reported [H₃(R-L) = 2,6-bis(4-methyl-6-R-salicyl)-4-tert-butylphenol, where R = Me or ^tBu]. The reaction of H₃[Me-L] with TaCl₅ in toluene gave [(Me-L)TaCl₂]₂ (1). The [^tBu-L] analogue [(^tBu-L)TaCl₂]₂ (2) was synthesized via treatment of TaCl₅ with Li₃[^tBu-L]. A THF solution of LiBHEt₃ was added to 1 in toluene to provide [(Me-L)TaCl(THF)]₂ (3), while treatment of 2 with 2 equiv of LiBHEt₃ or potassium in toluene followed by recrystallization from DME resulted in formation of [M(DME)₃][{(^tBu-L)TaCl}₂(μ-Cl)] [M = Li (4a), K (4b)]. When the amount of MBHEt₃ (M = Li, Na, K) was increased to 5 equiv, the analogous reactions in toluene afforded [{(bit-^tBu-L)Ta}₂(μ-H)₃M] [M = Li(THF)₂ (5a), Na(DME)₂ (5b), K(DME)₂ (5c)]. During the course of the reaction, the methylene CH activation of the ligand took place. Dissolution of 5a in DME produced [{(bit-^tBu-L)Ta}₂(μ-H)₃Li(DME)₂] (6), indicating that the coordinated THF molecules are labile. When the 2/LiBHEt₃ reaction was carried out in THF, the ring opening of THF occurred to yield [(^tBu-L)Ta(OBuⁿ)₂]₂ (7) along with a trace amount of [Li(THF)₄][{(^tBu-L)TaCl}₂(μ-OBuⁿ)] (8). Treatment of 2 with potassium hydride in DME yielded [{(^tBu-L)TaCl₂K(DME)₂}₂(μ-OCH₂CH₂O)] (9), in which the ethane-1,2-diolate ligand arose from partial C-O bond rupture of DME. The X-ray crystal structures of 2, 3, 4, 5a, 6, 7, and 9 are described.     

A ring-fission/C–C bond cleavage reaction with an N-alkyl-N-methyl-N-[(5-phenyl-1,2,4-oxadiazol-3-yl)methyl]amine

The reaction of N-(3,4-dichlorophenethyl)-N-methylamine (1) with 3-chloromethyl-5-phenyl-1,2,4-oxadiazole (2) was investigated. Employment of an equimolar amount of 1 and 2 in the presence of potassium carbonate led to the expected tertiary amine 3 (N-[(3,4-dichlorophenyl)ethyl]-N-methyl-N-[(5-phenyl-1,2,4-oxadiazol-3-yl)methyl]amine), whereas an excess of 1 and prolonged reaction time resulted in ring fission of the oxadiazole system in 3 and finally in the formation of N′-benzoyl-N-[(3,4-dichlorophenyl)ethyl]-N-methylguanidine (4) and N,N′-bis[(3,4-dichlorophenyl)ethyl]-N,N′-dimethylmethanediamine (5). The structures of products 3–5 were determined by means of ¹H and ¹³C NMR-spectroscopy, mass spectrometry and IR-spectroscopy, for 3 (as picrate) and 4 also X-ray structure analysis was employed. A possible mechanism of the reaction pathway leading to compounds 4 and 5 is proposed.     

FABRICATION OF SELF-ASSEMBLY DNA-C_(60) MULTILAYER FILMS

Electrostatic layer-by-layer self-assembly multilayer films were successfully fabricated from C_(60)-ethylenediamineadduct (C_(60)-EDA) and DNA. Under visible light irradiation, DNA is ready to be cleaved and the films are destroyed.     

Synthesis and reactivity of 2-(porphyrin-2-yl)-1,3-dicarbonyl compounds

A simple and efficient procedure for the synthesis of porphyrins bearing 1,3-dicarbonyl moieties at the β-position is described. The new compounds were further functionalized and new derivatives containing an heterocyclic ring, an ethyl acetate residue or a 2-oxopropyl group at the β-position have been obtained.     

Synthesen,Einkristall-Röntgenstrukturanalysen und 29Si-Festkörper-NMR-Untersuchungen eines zwitterionischen λ5-Spirosilicats und eines käfigartigen Octa(silasesquioxans)

Syntheses, Single-Crystal X-Ray Analyses and Solid-State ²⁹Si NMR Studies of a Zwitterionic λ⁵-Spirosilicate and a Cage-like Octa(silasesquioxane) The zwitterionic λ⁵-spirosilicate bis[2,3-naphthalenediolato(2 ?)][2-(dimethylammonio)phenyl]silicate ( 1 ; isolated as 1 · 1/2 CH₃CN) was synthesized by reaction of the [2-(dimethylamino)phenyl]dimethoxyorganosilanes 5, 6 and 7 [2-(Me₂N)C₆H₄Si(OMe)₂R: R = Ph ( 5 ), cyclo? C₆H₁₁ ( 6 ), Me ( 7 )] with 2,3-dihydroxynaphthalene in acetonitrile at room temperature. Reaction of 1 · 1/2 CH₃CN or [2-(dimethylamino)phenyl]trimethoxysilane ( 3 ) with water in acetonitrile yielded the cage-like octa{[2-(dimethylamino)phenyl]silasesquioxane} ( 2 ). The crystal structures of 1 · 1/2 CH₃CN and 2 were studied by X-ray diffraction. In addition, 1 · 1/2 CH₃CN and 2 were characterized by solid-state (²⁹Si CP/MAS) and solution NMR studies (¹H, ¹³C, ²⁹Si).     

Novel biotransformation of pentacyclic triterpenoid acids by Nocardia sp. NRRL 5646

Six pentacyclic triterpene acids, ursolic acid, oleanolic acid, betulinic acid, 23-hydroxybetulinic acid, glycyrrhetinic acid, and senegenin, were metabolized by the microbe Nocardia sp. NRRL 5646 to selectively furnish their corresponding 28-methyl esters. Notably, ursolic acid (1) was converted to oleanolic acid methyl ester (4) via two intermediates, oleanolic acid (2), and ursolic acid methyl ester (3), which are formed by participation of ‘retro-biosynthetic’ methyl migration from C-19 to C-20. Senegenin (11) was selectively converted to a nortriterpene methyl ester, senegenic acid methyl ester (12), via an unprecedented C-C bond cleavage. The stereochemical assignments of compounds 11 and 12 were made unambiguously for the first time using 2D NMR spectroscopy.     

Fe3(CO)12与P(NEt2)2Cl的反应--两核和三核铁羰基簇合衍生物的合成和晶体结构

Fe_3(CO)_(12)与配位基前体P(NEt_2)_2Cl反应,给出4个新的两核和三核铁羰基簇合衍生物:Fe_2(CO)_6(μ-Cl)[μ-P(NEt_2)_2](Ⅰ),Fe_2(CO)_6[μ-P(NEt_2)_2]_2(Ⅱ),Fe_3(CO)_9(μ-CO)(μ_3-PNEt_2)(Ⅲ)和Fe_3(CO)_9(μ_3-PNEt_2)[P(NEt_2)_3](Ⅳ)。在反应期间,配前体分子中的P-Cl和P-N键劈开,形成的分子片Cl、PNEt_2、P(NEt_2)_2和P(NEt_2)_3作为配体与铁羰合物重新组建成上述簇合物。利用X射线衍射法测定了它们的晶体结构。Ⅰ属三斜晶系,P1空间群,晶胞参数a=0.8745(6)nm,b=0.9601(7)nm,c=1.3996(10)nm,α=74.131(11)°,β=79.480(12)°,γ=69.727(12)°,V=1.0553(13)nm~3,D_c=1.543g·cm~(-3),Z=2,R=0.0443,wR=0.0831。Ⅱ属正交晶系,Pbcn空间群,晶胞参数a=1.0153(3)nm,b=1.7543(5)nm,c=1.6860(5)nm,V=3.0031(15)nm~3,D_c=1.394g·cm~(-3),Z=4,R=0.0519,wR=0.1035。Ⅲ属单斜晶系,P2_1/c空间群,晶胞参数a=1.0280(5)nm,b=1.2113(5)nm,c=1.9192(7)nm,β=93.560(7)°,V=2.1366(16)nm~3,D_c=1.712g·cm~(-3),Z=4。Ⅳ属单斜晶系,Cc空间群,晶胞参数a=1.5875(7)nm,b=1.0359(5)nm,C=2.1919(9)nm,β=101.266(8)°,V=3.535(3)nm~3,Dc=1.443g·cm~(-3),Z=4。Ⅰ和Ⅱ为两核铁簇,其簇骨架Fe_2PCl和Fe_2P_2呈蝶状。Ⅲ和Ⅳ     

Synthesis,characterization and biological screening studies of mixed ligand complexes using flavonoids as precursors

Flavonoids are a group of plant phenolics that provide various health benefits through cell signalling pathways and antioxidant effects. In the present study, a new series of mixed ligand complexes of Co(II), Ni(II), Cu(II) and Zn(II) were synthesized by incorporating curcumin and quercetin flavonoid precursors. The structural features of the synthesized complexes were explored using elemental analysis, thermogravimetric analysis, UV–visible, infrared, NMR, mass and electron paramagnetic resonance spectral analyses and conductivity measurements. These data support an octahedral geometry of the synthesized complexes. In silico biological activity score for the ligand was predicted using PASS online software. ADMET properties were studied using VLS3D online software. Anti‐inflammatory and antioxidant activities were experimentally validated which prove that theoretical predictions are in agreement with the experimental results. Interestingly the synthesized complexes interact with calf thymus DNA through groove binding mode. Moreover, they have good potential to cleave pUC19 DNA. Minimum inhibitory concentration values of the synthesized complexes reveal that they have better antimicrobial efficacy than the ligands.     

Structures,DNA binding,DNA cleavage,and antitumor investigations of a series of molybdenum(VI) complexes with some N(4) methyl and ethyl thiosemicarbazone ligands

Four dioxomolybdenum(VI) complexes were synthesized by reaction of [MoO₂(acac)₂] with thiosemicarbazones derived from 5-allyl-2-hydroxy-3-methoxybenzaldehyde (1), 2-hydroxynaphthaldehyde (2), 2,3-dihydroxybenzaldehyde (3), or 5-tert-butyl-2-hydroxybenzaldehyde (4). The ligands were coordinated to molybdenum as tridentate ONS donors. X-ray crystallography showed that the distorted octahedral coordination of molybdenum is completed by methanol (D) in 1a, 3a, and 4a or H₂O in 2a. The molecular structures of 1, 3, and 4, and the complexes were determined by single-crystal X-ray crystallography. Binding of the ligand and complexes with calf thymus DNA were investigated by UV, fluorescence titrations, and viscosity measurements. Gel electrophoresis revealed that all the complexes can cleave pBR322 plasmid DNA. The cytotoxic properties of the complexes against human colorectal (HCT 116) cell line showed strong antiproliferative activities in relative order 4a?>?3a?>?1a?>?2a with IC₅₀ values of 1.6, 4.0, 4.8, and 6.7?μM, respectively. The complexes exhibited more activity than the standard reference drug, 5-fluorouracil (IC₅₀ 7.3?μM). These studies show that dioxomolybdenum(VI) complexes have potential use in chemotherapy.