About a quarter of a century ago a review article having almost the same title appeared in this journal[1]. Since then many hundreds of new fluorides and oxides of metals have been synthesized, and repeatedly subjected to detailed investigation. Why, and to what end are such compounds still studied[2]? Has our knowledge been not only widened but also deepened? What advances have been made in synthetic chemistry in this sector? Have new ideas led to unforeseen results and have unexpected findings forced the revision of tested concepts? This area of research belongs to solid state chemistry, and in the meantime has become almost unsurveyable even for a committed researcher. In this paper, therefore, an attempt is made to outline any relevant advances that have been made and to present open questions and new aspects using selected examples, mainly from the chemistry of the first row of the transition metal series. Those not directly involved in this area may be surprised to find that even substances with a simple composition are also cited. They might ask whether such compounds mentioned in text books are not already understood. Although it is a widely-held view that such compounds are well known, this is incorrect: Probably no-one has ever prepared a sample of CrF2 or Na2O whose composition “adequately” exactly corresponded to the quoted formula[3]. Typical examples which demonstrate the considerable effort necessary for finally proving what others long ago already assumed to know, can be taken from the area of inorganic chemistry (e.g.: As2O) as well as from organic chemistry (e.g. C4[C(CH3)3]). 相似文献
Two new natural products, samroiyotmycins A (1) and B (2), along with two naturally new novclobiocin 101 (3) and 4-hydroxy-3-(3-methylbut-2-enyl)benzamide (5), and five known substances including neoantimycin, clorobiocin (4), 29-O-methylabierixin, daidzein, and 1-(3-indolyl)-2,3-dihydroxypropan-1-one have been isolated from Streptomyces sp. BCC33756. Their chemical structures were determined based on NMR spectral information and the relative stereochemistry of compound 1 was determined by X-ray crystallographic data. Both samroiyotmycins A and B exhibited antimalarial activity against Plasmodium falciparum K1—multi-drug resistant strain, with IC50 values of 3.65 and 3.16 μg/mL, respectively. Compound 1 was inactive against both cancerous (MCF-7, KB) and non-cancerous (Vero) cells, while compound 2 displayed cytotoxicity against Vero cell with IC50 value of 29.57 μg/mL. 相似文献
Considerations of TLC process optimization have been based on the thermodynamic theory of adsorption from multicomponent solvents using experimental and theoretical RM1, 2 = f (Φ1) relationships. It was found that a relationship exists between the Az parameter (log k where k is the partition coefficient of the substance chromatographed) of the above theory and pKa values of substances as well as the solubility parameter δ of the mobile phase components. Analysis of the Az values of substances shows that a slight variation therein is associated with lower selectivity of chromatographic separation. 相似文献
The new complexes mer-Cr(py)3(N3)3, NaCr(py)4(N3)4, KCr(py)4(N3)4, and RbCr(py)3(N3)4 (py = pyridine) have been prepared. Infrared (4000-50 cm−1) and diffuse reflectance spectra (region 300-77 K) of powdered samples have been measured and discussed on bases of the known structures of these complexes. Single crystal absorption spectra for the mer-complex were obtained in the temperature range from 300 to 10 K revealing extensive vibronic structure associated with the 2Eg(Oh) and 2T1g(Oh) electronic origins. Crystal field calculations were used to assign the bands in the vibronic region and to obtain estimates for the crystal field and Racah parameters for this class of substances. The parameters found for the mer-complex at 10 K are 10 Dq = 17906 cm−1, B = 387 cm−1 and C = 3381 cm−1. 相似文献
Phase formation in CaF2–HoF3 system has been studied by coprecipitation followed by X-ray powder diffraction. Aqueous nitrate solutions have been used as initial substances, while hydrofluoric acid has been employed as fluorinating agent. Formation of hydrated nanophases: solid solution Ca1–xHoxF2 + x (х ≤ 0.1) and HoF3 has been revealed. Dehydration proceeds on heating to 600°C. 相似文献
A number of sesquiterpenoid mold metabolites have been isolated and characterized recently. One important class of these naturally occurring substances, the trichothecane group, possesses an eminent degree of phytotoxic activity against certain pathogenic fungi.1 The least structurally complicated member of this important class of mold metabolites is (-)-trichodermin (1). The structure and absolute stereochemistry of this unique phytotoxic metabolite was determined from chemical, spectroscopic, and X-ray diffraction data.2,3,4 Recently Colvin, Raphael, and Roberts reported an elegant total synthesis of racemic trichodermin via (±)-lactone 2b (R[dbnd]CH3).5 We wish to report, herein, a synthesis of optically active (+)-lactone 2b (R[dbnd]CH3).6相似文献
The mono- and binuclear hydride compounds fac-[ReH(CO)3L] (1a) and [{ReH(CO)4}2(μ-L)] (1b) have been prepared by reaction of [ReH(CO)5] with Ph2PN(CH3)(CH2)2N(CH3)PPh2 (L) under UV light. Protonation reactions of the hydride compound 1a with equimolar amounts of HSO3CF3 or HCl yielded the triflato or the chlorido compounds fac-[Re(OSO2CF3)(CO)3L] (2) and fac-[ReCl(CO)3L] (3), respectively. The compounds have been characterised by elemental analysis, IR and NMR spectroscopic data, and mass spectrometry. Their structures have been confirmed by X-ray crystallography. 相似文献
d- and l-Serine have been used for the enantioselective synthesis of tosylates 7a and 7b, useful building blocks for the synthesis of triols 5a and 5b which have already been obtained via a diastereoselective synthesis and used for the synthesis of 2a, 2b and 2c. We have thus performed a formal synthesis of 24S,25-(OH)2-D3, 24R,25-(OH)2-D3 and 1α,24R,25-(OH)3-D3. 相似文献
Two cobalt(II) and cadmium(II) complexes, [Co(H2DMOPhIDC)2(H2O)2] ? 2H2O (H3DMOPhIDC = 2-(3,4-dimethoxyphenyl)-1H-imidazole-4,5-dicarboxylic acid) (I), [Cd(H2MOPhIDC)2-(Phen)] ? C2H5OH (H3MOPhIDC = 2-(3-dimethoxyphenyl)-1H-imidazole-4,5-dicarboxylic acid, Phen = 1,10-phenanthroline) (II), have been hydro(solvo)thermally synthesized by employing two kinds of organic ligands, H3DMOPhIDC or H3MOPhIDC, respectively. The molecular structures of I and II have been characterized by IR spectra, elemental analyses and single-crystal X-ray diffraction (CIF files CCDC nos. 935845 (I), 935846 (II)). Both complexes show three-dimensional supramolecular structures supported by intermolecular H-bonds. Furthermore, the thermogravimetric and photoluminescent properties of two complexes have been investigated as well. 相似文献
Chiral and racemic Salen-type Schiff-base ligands (H2L1, H2L2 and H2L3), condensed between D-(+)- and D,L-camphoric diamine (also known as (1R,3S)-1,2,2-trimethylcyclopentane-1,3-diamine) and 2-hydroxybenzaldehyde or 3,5-dibromo-2-hydroxybenzaldehyde with a 1:2 molar ratio, have been synthesized and characterized. A series of new nickel(II), palladium(II) and copper(II) complexes of these chiral and racemic ligands exhibiting different coordination number (4, 5 and 6) have been characterized with the formulae [NiL1]·CH3OH (3), [NiL1]·H2O (4), [NiL2] (5), [PdL2] (6), [Cu2(L2)2(H2O)] (7) and [NiL3(DMF)(H2O)] (8). Different solvent molecules in 3 and 4 (methanol and water molecules) as well as different apical ligands in 7 and 8 (water and DMF molecules) are involved in different O–H···O hydrogen bonding interactions to further stabilize the structures. UV–Vis (UV–Vis), circular dichroism (CD) spectra and thermogravimetric (TG) analyses for the metal complexes have also been carried out. 相似文献
We have studied the thiolysis of (2R,1′S)- or (2S,1′S)-2-(1-aminoalkyl)epoxides 1 or 2 in the presence of BF3·OEt2. The ring opening took place at C-3 with complete regioselectivity, affording the corresponding enantiopure (2R,3S)- or (2S,3S)-3-amino-1-(alkylthio)alkan-2-ols 3 or 4 in good or high yield. The structures of compounds 3 and 4 have been proposed based on HMBC NMR experiments. 相似文献
The fluorides KF, RbF and CsF have been known to serve as catalysts for the reaction CF2O + F2→ CF3OF. The list of catalysts for this process has now been enlarged to include NaF, MgF2, CaF2, SrF2, BaF2 and LaF3. Lithium fluoride and thorium fluoride also give CF3OF but are less active. Perhaps the substances CsF·HF, KAgF4 and NiF2 should be included in this list. Silver fluoride, usually as a mixture of AgF2 with AgF, has been known to catalyze the reaction of CF2O with F2 to give both CF3OF and CF3OOCF3. The proportion of the latter in the mixture of products increases with decreasing temperature. At 25°, the reaction is slow and the yield of CF3OOCF3 is very high. It has now been shown that TIF3 behaves like silver fluoride. It has also been shown that many other fluorides of metals give higher yields of CF3OOCF3 than of CF3OF but require higher temperatures than AgF2 (100-ca. 150°) to be effective. Various possible mechanisms for these catalytic processes are discussed. 相似文献
Some niobium and tantalum phosphates have been prepared and their infra-red spectra have been recorded and compared with those of reference substances. It has been possible to identify P04-3, P2O7-4 and possibly P3O10-5 groups in different samples of niobium and tantalum phosphates. 相似文献
Contributions to the Chemistry of Phosphorus. 117. Synthesis and Properties of the Hexaorganyl-octaphosphanes(6) P8R6, R = Me, Et, Pri The Hexaorganyl-octaphosphanes(6) P8Me6 ( 1 ), P8Et6 ( 2 ), and P8Pr ( 3 ) have been obtained by reacting mixtures of the corresponding organyldichlorophosphanes and phosphorus(III) chloride with magnesium. In the case of 1 and 2 the organyl-cyclophosphanes (PR)n can also be used in the reaction with phosphorus(III) chloride and magnesium. Besides, mainly P7R5 as well as other polycyclic organylphosphanes are formed. 2 and 3 have been isolated as pure substances, whereas 1 was concentrated to ?50 mol-% in the product mixture. According to their 31P-NMR spectra the three compounds possess a pentalane-analogous P8-skeleton with the substituents within each five-membered ring in trans position and the substituents of different five-membered rings next to the zero bridge in cis position; the organyl groups in the 3, 7 position are trans oriented with respect to the free electron pairs of the bridgehead atoms. Therefore, the structures of 1 – 3 differ from the known tert-butyl compound P8Bu, whereas the corresponding phosphorus hydride P8H6 has the same pentalane-analogous P8-skeleton, thus being a bicyclo[3.3.0]octaphosphane. 相似文献
The authors have coupled ultrafine α-Fe2O3 nanocrystals to N-doped graphene (NG) to obtain a novel material for use in a photoelectrode. The presence of NG is shown to strongly affect the morphology and size of the α-Fe2O3 nanocrystals formed on the NG sheets, and to improve their photoelectrochemical (PEC) activity. Interestingly, the PEC performance of the nanocomposite is closely correlated to the size of the α-Fe2O3 nanocrystals in that small nanocrystals display better PEC properties. The photocurrent of α-Fe2O3-NG is nearly 3.3-fold stronger than that of α-Fe2O3 nanocrystals. Based on the remarkable PEC performance of this nanocomposite, a PEC sensor was constructed for the sensitive determination of 1,4-dihydroxybenzene (HQ). Its photocurrent increases with the HQ concentration in the range from 3.0 nM to 3.3 μM, and the detection limit is 1.0 nM (at an S/N ratio of 3). In our perception, the study presented here can serve as a basis for a better understanding of the relationship between morphologies and PEC performance of such nanomaterials. Conceivably, it may be extended to other PEC sensing system and to other fields associated with nanotechnology.
Graphical abstract Ultrafine α-Fe2O3 nanocrystals were prepared via coupling with N-doped graphene (NG) substances (α-Fe2O3-NG). They exhibit superior photoelectrochemical (PEC) performance and have been successfully utilized for PEC-based sensing.
The reactions of [ReX3(MeCN)(PPh3)2] (X = Cl or Br) with 1-(2-pyridylazo)-2-naphthol (HPAN) have been examined and the [ReBr(PAN)2] · 2CHCl3 (1) and [ReCl(PAN)2] (2) complexes have been obtained. The both complexes have been structurally and spectroscopically characterized, and compound 1 has been additionally studied by magnetic measurements. The magnetic behavior is characteristic of mononuclear seven-coordinated Re(III) complex with d4 low-spin configuration, which gives diamagnetic ground state. 相似文献
The first examples of doubly bridged calix[7]arenes 2a-h have been obtained by base-promoted O-alkylation of p-tert-butylcalix[7]arene 1 or 1,4-tetramethylene-bridged calix[7]arene 3a with a variety of bis-electrophiles including BrCH2Cl, oligoethylene glycol ditosylates, and 1,2-bis(bromomethyl)benzene. In the presence of Cs2CO3 as the base, in acetone, the syn-1,4:2,3-bis-bridged regioisomer was obtained in yields up to 76%. Assignment of bridging pattern was based on chemical shift of OH groups in conjunction with chemical correlations with known compounds. Stereochemical and conformational features were investigated with the aid of 2D and Dynamic NMR studies and MM3 calculations. 相似文献
The novel bidentate ligand, C5H4CPh2CH2-(1-Me-C3H4N2) (3), has been prepared and characterized as its lithium salt LiC5H4CPh2CH2-(1-Me-C3H4N2) (3-Li). Cyclopentadiene HC5H4CPh2CH2-(1-Me-C3H4N2) (3-H) has been obtained from 6,6-diphenylfulvene and 1,2-dimethylimidazoline (1). In THF-d8 solution in the presence of 1, (1-methylimidazoline-2-yl)methyllithium (2) has been proved to undergo gradual conversion into a dilithium derivative of N1-methyl-N2-[(1E,2E)-1-methyl-2-(1-methylimidazolidine-2-idene)ethylidene]ethane-1,2-diamine (2a). In a solution, cyclopentadiene 3-H has been shown to undergo isomerization into 3-{N-[2-(N-methylamino)ethyl]amino}-1,1-diphenyl-1,2-dihydropentalene (4) and, further, into a mixture of 4 and two rotameric 3-[N-(2-aminoethyl)-N-methylamino]-1,1-diphenyl-1,2-dihydropentalenes (5a) and (5b). Treatment of the lithium salt 3-Li with Me3SiCl has lead to 3-{N-[2-(N-trimethylsilylamino)ethyl]amino}-1,1-diphenyl-1,2-dihydropentalene (6) as the dominant component in the reaction mixture. In the latter case the expected Me3Si-C5H4CPh2CH2-(1-Me-C3H4N2) (3-Si) was not observed. Stannylation of 3-Li with 1 equiv. of Me3SnCl has resulted in formation of a mixture of Me3Sn-C5H4CPh2CH2-(1-Me-C3H4N2) (3-Sn), (Me3Sn)2-C5H3CPh2CH2-(1-Me-C3H4N2) (3-Sn2), and cyclopentadiene 3-H in a ca. 2:1:1 molar ratio. Monocyclopentadienyl complexes {[η5:η1-κN-C5H4CPh2CH2-(1-Me-C3H4N2)]MCl3 (M = Ti (7), Zr (8)) have been prepared starting from the organotin and organolithium compounds 3-Sn and 3-Li, respectively. The dynamic behavior of complexes 7 and 8 has been investigated by means of variable-temperature NMR spectroscopy in solutions. The molecular structures of the dihydropentalene 4, binuclear complex {[η5:η1-κN-C5H4CPh2CH2-(1-Me-C3H4N2)]ZrCl2}2(μ-Cl)28, and a coordination dimer of the dilithium salt 2a have been established by X-ray diffraction analysis. In the crystal structure of the 2a-dimer, the shortest known Li-Li contact has been found. 相似文献
The [Pd(N-N∗)Cl2] complexes have been obtained, as yellow solids, in almost quantitative yields; N-N∗ indicate bidentate chiral ligands (Sa)-1, (Sa)-2, (S,S)-3, (R,R)-4, containing the rigid 2-pyridinyl or 8-quinolinyl building block skeleton and the C2-symmetric chiral framework trans-2,5-dimethylpyrrolidinyl or (S)-(+)-2,2′-(2-azapropane-1,3-diyl)-1,1′-binaphthalene. The ligands pairs have the same C2-symmetric chiral framework but different building block skeleton, beyond that for the basicity in the N-donor atoms, for rigidity and flexibility features. The N-N∗ ligands act as chelating ligands leading a square planar geometry. The compounds [Pd(S,S-3)Cl2] and [Pd(R,R-4)Cl2] have been also characterised by X-ray diffraction. The rigidity and flexibility features of (S,S)-3 and (R,R)-4 ligands induce a different orientation of the trans-2,5-dimethylpyrrolidinyl moiety with respect to the pyridinyl and quinolinyl plane. This work shows that intrinsic rigidity and flexibility are not enough to define the ligand properties and to preview the effects that they induce on the reactivity of the metal complex. 相似文献
The pathophysiological roles of the endogenous signaling molecule, carbon monoxide (CO), have been extensively studied and validated in cell culture and animal models. Further, evidence supporting the therapeutic effects of CO in various human diseases has been mounting over the last two decades. Along this line, there has been intensive interest in developing various delivery forms including CO gas, CO in solution, metal–carbonyl complexes widely known as CO-releasing molecules (CO-RMs), and organic CO prodrugs. Among them, two ruthenium-based carbonyl complexes, CORM-2 and -3, occupy a very special place because they have been used in over 500 published studies. One of the mechanisms for CO''s actions is known to be through attenuation of oxidative stress and regulation of production of reactive oxygen species (ROS). For this reason, it is important that CO delivery forms do not have intrinsic chemical redox properties. Herein, we describe our findings of catalase-like activities of CORM-2 and -3 in a CO-independent fashion, leading to the rapid degradation of hydrogen peroxide (H2O2) in PBS buffer (pH = 7.4) and in cell culture media. Further, we have found that CORM-2 and CORM-3 possess potent radical scavenging abilities. We have also studied two other widely used CO donors: CORM-401 and CORM-A1. Both showed chemical reactivity with ROS, but to a lesser degree than CORM-2 and -3. Because of the central role of ROS in some of the proposed mechanisms of actions for CO biology, the discovery of intrinsic chemical redox properties for these CO-RMs means that additional attention in designing proper controls is needed in future biological experiments using these CO-RMs for their CO-donating functions. Further, much more work is needed to understand the true implications of the chemical reactivity of these CO-RMs in cell-culture and animal-model studies of CO biology.Four CO-releasing molecules are found to degrade H2O2 and free radicals either catalytically (CORM-2 and -3) or through direct reactions (CORM-401 and -A1) in solution under near-physiological conditions.相似文献