首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
方宗杰 《古生物学报》2022,61(4):662-663
1993年, 于菁珊和董国义为辽宁上三叠统的非海相双壳类化石建立了一个新属辽宁蚌Liaoningia Yu and Dong, 1993, 以Liaoningia opima Yu and Dong, 1993作为模式种。然而, 早在1979年, 邢裕盛和刘桂芝就已为辽宁晚前寒武纪南关岭组所产的化石标本创建了新属名辽宁水母属Liaoningia Xing and Liu, 1979, 模式种是Liaoningia fuxianensis Xing and Liu, 1979。然而, 多数学者反对将它视为水母类化石, 有人怀疑辽宁水母属是假化石, 迄今学术界并无统一意见, 故本文暂将它归为疑问化石(Problematica)。根据“国际动物命名法规”, 我们提出一个新的属名Liaoningoconcha nom. nov., 用以替代Liaoningia Xing and Liu, 1979的次同义名Liaoningia Yu and Dong, 1993, 仍使用于菁珊和董国义在1993年指定的模式种, 中文译名不变。  相似文献   

2.
The trinuclear complex [L2Cu3(CF3CO2)4] (1) has been synthesized and its crystal structure determined. It consists of a linear arrangement of Cu(II) centers. The central copper atom is bonded to six oxygen atoms and has a tetragonally distorted octahedral geometry, while the terminal copper atoms are bonded to three oxygen and two nitrogen atoms and show a distorted square pyramidal geometry. The complex shows di-μ(O,O′) syn-syn carboxylate bridging as well as monoatomic (μ-O) bridging, along with phenolate (μ-O) oxygen bridging. Cryomagnetic investigations in the range 2-300 K revealed an antiferromagnetic spin exchange interaction with J = −95.7 cm−1, based on the isotropic exchange model Hex = −2J[S1 · S2 + S2 · S3].  相似文献   

3.
The unusual 18e seven-coordinate Mo(II) complex [Mo(NO)(H2NO-κ2N,O)(TpMe2)I] (1; [TpMe2] is hydrotris(3,5-dimethylpyrazol-1-yl)borate) has been synthesised and characterised by IR, 1H NMR and ESI-MS spectroscopies and by a single crystal X-ray diffraction study. The complex has a distorted pentagonal bipyramid structure with equatorial κ2-NH2O ligand (dN-O = 1.387 Å, dMo-N and dMo-O equal 2.049 and 2.092 Å, respectively). In the solid state 1 exists as a dimer (the point group Ci) due to the formation of two NH?O hydrogen bonds (dN-H?O = 2.064 Å) between the adjacent NH2O ligands, whilst in solution at/or above RT it resolves itself giving a monomer, which readily isomerises to more thermodynamically stable diastereoisomer.  相似文献   

4.
王成源 《古生物学报》1992,31(5):621-622
Nieper(1969)依据澳大利亚 Queenslaad 西部 Nora 组(下奥陶统)的标本以 Trigonodus triangularius Nieper 1969 为模式种,建立了牙形刺新属 Trigonodus. Cooper(1981)将 Nieper 的形式属 Trigonodus 修正为器官属,包括 PM Sa Sb Sc Sd 分子,并将此属的模式种改为 Trigonodus larapintinensis (Crespin, 1943). Cooper 的观点被很多牙形刺专家接受, Trigonodus 属名也被广泛引用在牙形刺文献中 (Stauge, 1984;安泰庠、郑昭昌,1990),  相似文献   

5.
Two novel tetranuclear compounds with an unprecedented mode of a hydrogenphosphato bridge, [Cu4(dpyam)443-HPO4)2(μ-X)2]2+ (in which dpyam = di-2-pyridylamine and X = Cl (1), Br (2)) have been synthesised and characterised structurally and magnetically. The Cu(II) ions in the structures each display a square-pyramidal geometry, with two tridentate hydrogenphosphato groups bridging four copper atoms in a μ43 coordination mode which is rarely found in hydrogenphosphate metal compounds. Each (different) pair of Cu(II) ions is additionally bridged by halide ions, with relatively long Cu-X distances (2.551(3)-2.604(3) Å for 1 and 2.707(1)-2.766(2) Å for 2) and subsequently also a small Cu-X-Cu angle (65.7(1)° and 65.1(1)° for 1 and 61.6(1)° and 62.4(1) for 2) and a large Cu-X-Cu angle (95.5(1)° and 96.5(1)° for 1 and 91.1(1)° and 92.6(1)° for 2). Cu?Cu distances in the tetranuclear units varies from 2.802(3) to 5.232(3) Å for 1 and from 2.834(1) to5.233(1) Å in 2. The lattice structures are stabilised by extensive intermolecular hydrogen bonds. The magnetic susceptibility measurements down to 5 K revealed a weak ferromagnetic interaction between the outer pairs of Cu(II) ions which vary from 22 to 46 cm−1 in 1 and 12 to 33 cm−1 in 2 and a moderately strong antiferromagnetic interaction between the inner Cu(II) ions of −79 cm−1 in 1 and −83 cm−1 in 2, via the Cu-O-P-O-Cu pathway.  相似文献   

6.
最常见的人类X染色体的结构异常是长臂等臂X染色体,以及X染色体与常染色体之间的易位。关于idic(X)染色体结构异常的病例较为罕见。国外Chapella等曾有研究,国内周氏等首次报道了有关idic(X)染色体结构异常的病例。  相似文献   

7.
Saponification of the bis(carbamic acid ester) 1,3-C6H4(CMe2NHCO2Me)2 (1), made by the addition of methanol to commercial 1,3-C6H4(CMe2NCO)2, yielded the meta-phenylene-based bis(tertiary carbinamine) 1,3-C6H4(CMe2NH2)2 (2). Dinuclear [{(η4-1,5-C8H12)RhCl}2{μ-1,3-C6H4(CMe2NH2)2}] (3) resulted from the action of 2 on [{(η4-1,5-C8H12)Rh(μ-Cl)}2] in toluene. Combination of 2 with PdCl2 or K2[PdCl4] gave the dipalladium macrocycle trans,trans-[{μ-1,3-C6H4(CMe2NH2)2}2(PdCl2)2] (4) along with cyclometalated [{2,6-C6H3(CMe2NH2)2NC1N′}PdCl] (5). Substitution of PEt3 for the labile chlorido ligand of 5 afforded [{2,6-C6H3(CMe2NH2)2NC1, κN′}Pd(PEt3)]Cl (6). The crystal structures of the following compounds were determined: bis(carbamic acid ester) 1, ligand 2 as its bis(trifluoroacetate) salt [1,3-C6H4(CMe2NH3)2](O2CCF3)2, 2 · (HAcf)2, complexes 3 and 6, as well as 1,3-C6H4(CMe2OH)2 (the diol analogue of 2).  相似文献   

8.
A fossil fish fauna from an erratic Wealden clay deposit in the tillitic cliff of Lobber Ort (Isle of Rügen/GDR) is described (Hybodus sp.,Polyacrodus sp.,Lissodus rugianus n. sp.,Lepidotes cf.mantelli Agassiz,Lepidotes sp., Pycnodontiformes fam., gen. et sp. indet). The fauna indicates brackish-fresh water conditions and resembles those from British Purbeck and Wealden deposits and from the Wealden deposits of Hannover. The exceptional environmental features within the depositional area of the NW-European Wealden facies have obviously accelerated speciation processes within the genusLissodus Brough 1935 during the Earliest Cretaceous.  相似文献   

9.
Novel, thermally stable, dark-red to orange Pt02-N,N′-diazadiene)(η2-alkene) compounds have been synthesized in good yields from Pt0(COD)2 or Pt0(NBE)3, by stepwise substitution of the respective dienes or alkenes by an electron-poor alkene (dimethyl fumarate, maleic anhydride or fumaronitrile), followed by the appropriate diazadiene ligand in dry diethyl ether at 20 °C (diazadiene=various N,N′-disubstitued-1,4-diaza-1,3-dienes). The complex Pt(DBA)2 is less suited as a precursor for the synthesis of Pt02-N,N′-diazadiene)(η2-alkene) compounds. These zerovalent Pt(diazadiene)(η2-alkene) compounds constitute a useful category of starting materials for synthetic organoplatinum chemistry and catalysis.  相似文献   

10.
Pt(II) complexes of the types cis- and trans-Pt(amine)2I2 with amines containing a phenyl group were synthesized and studied mainly by IR and multinuclear (195Pt, 1H and 13C) magnetic resonance spectroscopies. The compounds are not very soluble. In 195Pt NMR spectroscopy, the cis isomers were observed at slightly lower fields than the trans analogues (average Δδ = 11 ppm) in acetone. In 1H NMR, the NH groups were also found at slightly lower fields in the cis isomers. The coupling constants 2J(195Pt-1HN) varied from 53 to 85 Hz and seem slightly smaller in the trans configuration. The 13C NMR spectra of most of the complexes were measured. No coupling constants J(195Pt-13C) were detected due to the low solubility of the compounds. The cis isomers containing a phenyl group on the N atom could not be isolated except for Ph-NH2 which was shown to be a mixture of isomers in acetone. The tetrasubstituted ionic compounds [Pt(amine)4]I2 for the less crowded ligands were also studied mainly by NMR spectroscopy in aqueous solution. The 195Pt chemical shifts vary between −2855 and −2909 ppm. The coupling constants 3J(195Pt-1H) are about 40 Hz. The iodo-bridged dinuclear species I(amine)Pt(μ-I)2Pt(amine)I were also synthesized and characterized. Two isomers are present in acetone solution for most of the compounds. Their δ(Pt) signals were observed at about −4000 ppm and their coupling constants 2J(195Pt-1HN) are around 69 Hz.  相似文献   

11.
Reactions of a benzylidyne-capped tricobalt cluster, [Co3Cp33-CPh)2] (1), with halogens (X2 = Cl2, Br2, and I2) in CH2Cl2 afforded halogen-adducts of 1. The structure of four isolated salts [Co3Cp33-CPh)2(μ-Cl)]PF6 · MeCN (2PF6 · MeCN), [Co3Cp33-CPh)2(μ-Br)]SbF6 (3SbF6), [Co3Cp33-CPh)2(μ-I)]SbF6 · CH2Cl2 (4SbF6 · CH2Cl2), and [Co3Cp33-CPh)2(μ-I)]I3 (4I3) determined by X-ray diffraction can be regarded formally as halide-adducts of 12+. The halogen atom in each structure lies in the Co3 plane. The halogen-bridged Co-Co edge was elongated (in 2PF6 · MeCN = 2.6072(4), in 3SbF6 = 2.6106(7), in 4SbF6 · CH2Cl2 = 2.622(2), and in 4I3=2.6718(9) Å), and the Co-Co distances that had no halogen-bridge remained unchanged from the Co-Co distance of 1 (2.382(8) Å), (in 2PF6=2.4037(8) and 2.3948(7), in 3SbF6=2.3888(6) and 2.4017(7), in 4SbF6 · CH2Cl2 = 2.393(2) and 2.388(1), and in 4I3 = 2.397(1) and 2.3868(9) Å). The UV-Vis absorption spectra of 2+, 3+, and 4+ had characteristic absorption peaks at 796, 819, and 844 nm, respectively. Cyclic voltammograms of 2PF6 in CH2Cl2 with 0.1 M nBu4NPF6 as the supporting electrolyte showed a chemically reversible oxidation (at a potential of 0.75 V versus Fc/Fc+), and an irreversible reduction wave at −0.57 V. The irreversible reduction resulted in the recovery of 1. The redox properties of 3+ and 4+ are very similar to that of 2+. Cyclic voltammetry of 1 in 0.1 M nBu4NCl/MeCN indicates that the formation of 2+ is a multi-step reaction. Initially, 1 is oxidized to 1+, and then, 1+ is coordinated by Cl followed by immediate oxidation to 2+.  相似文献   

12.
The racemic total synthesis of elegansidiol, farnesiferol B, and farnesiferol D has been obtained following a Diels–Alder approach. Gillman addition, cross metathesis reaction are the other key steps involved in the target synthesis.  相似文献   

13.
Three Mn(III,III) complexes containing dibenzoylmethane (dbm), Mn2(OMe)2(dbm)2(ClH2CCOO)2 (1), Mn2(OMe)2(dbm)2(Cl2HCCOO)2 (2) and Mn2(OMe)2(dbm)2(Cl3CCOO)2 (3) were synthesized. Crystal structure determination and magnetic characterization were done for 2. The Mn?Mn distance in complex 2 is 2.865 Å. It exhibits antiferromagnetic coupling with exchange parameter |J| = 20.4 cm−1 (H = −2JSASB). All three complexes, though insoluble in common solvents, catalyse the disproportionation of hydrogen peroxide when dispersed on silica gel with turnover numbers ∼150-300. DFT simulations showed that bridging moieties have remarkable effect on intermetallic distances in dimanganese(III,III) complexes.  相似文献   

14.
A new heteronuclear NMR pulse sequence for the measurement of nJ(C,H) coupling constants, the /selective HC(C)H-TOCSY, is described. It is shown that the S3E element (Meissner et al., 1997a,b) can be used to obtain spin state selective coherence transfer in molecules, in which adjacent CH moieties are labeled with 13C. Application of the / selective HC(C)H-TOCSY to a 10nt RNA tetraloop 5-CGCUUUUGCG-3, in which the four uridine residues are 13C labeled in the sugar moiety, allowed measurement of two bond and three bond J(C,H) coupling constants, which provide additional restraints to characterize the sugar ring conformation of RNA in cases of conformational averaging.  相似文献   

15.
The number of species in the freshwater mussel genus Cristaria Schumacher, 1817 recognized from Far East Russia has varied over the last several decades. While some authors consider the occurrence of only one species, Cristaria plicata (Leach, 1815), widespread in East Asia, others, recognize two separate species Cristaria herculea (Middendorff, 1847) and Cristaria tuberculata Schumacher, 1817 from Far East Russia, distinct from C. plicata. For the present study, freshwater mussels, identified as C. herculea, were collected in the Upper Amur basin (Transbaikalia, Russia). The shell morphology and the whole soft body anatomy were analysed in detail and compared with previously published information on other Cristaria spp.. Additionally, a cytochrome oxidase subunit 1 (CO1) gene fragment was sequenced from foot tissue samples of selected animals, collected from the same region, and compared with published data. Based upon morphological similarities of glochidia and adult morphology and anatomy as well as the mitochondrial DNA sequence analysis, we consider C. herculea as a synonym of C. plicata. Further analysis of Far East Russia C. herculea and C. tuberculata specimens using both molecular and morphological characters should be carried in the future to enhance our knowledge about the taxonomy within the Cristaria genus. Moreover, a comprehensive revision of the genus Cristaria is needed, restricting the type locality and comparing topotypic specimens for both C. plicata and C. tuberculata, and including all recognized Cristaria species.  相似文献   

16.
Direct reaction of copper(I) chloride with triphenylphosphine (tpp) in molar ratio 2:3 and 1:3, results in the formation of the [(tpp)Cu(μ2-Cl)2Cu(tpp)2] (1) and {[CuCl(tpp)3]·(CH3CN)} (2) complexes. The complexes have been characterized by melting point, FT-IR, UV-Vis spectroscopic data and X-ray crystallography. Complex 1 is di-nuclear. Two μ2-Cl atoms bridge two copper(I) ions with tetrahedral and trigonal geometry respectively. The short copper-copper bond distance of 2.9039(6) ? in case of 1 indicates d10-d10 interaction between metal centers. Thus, our studies were extended here in the determination of the quasi-aromaticity, which results in strong Cu-Cu interactions, using the computational method of nucleus-independent chemical shifts (NICS). The NICS calculated at the inner region of the Cu2Cl2P3 core in complex 1 is shielded up to −6.05 ppm. Complex 2 is mono-nuclear where three phosphorus and one chloride atoms form a tetrahedron around the copper(I) ion. Photolysis of both complexes 1 and 2, results in the formation of triphenylphosphine oxide.The complexes 1 and 2, were tested for their in vitro cytotoxic activity against leiomyosarcoma cells (LMS) and human breast adenocarcinoma cells (MCF-7). The type of LMS cell death caused by the complexes was also evaluated by use of a flow cytometry assay. The results show that at concentration of 5 μΜ of complexes 1 and 2, 34.1% (1) and 19.6 (2)% of LMS cells undergo programmed cell death (apoptosis), while at 10 μΜ, 80.4% (1) and 65.2% (2) of LMS cells undergo apoptosis. The light sensitivity of the complex is discussed in relation with the biological activity.  相似文献   

17.
New types of Pt(II) mixed-ligand complexes containing a pyridine derivative (Ypy) and pyrazine (pz) were synthesized. The compounds were characterized by infrared spectroscopy and by multinuclear (1H, 13C and 195Pt) magnetic resonance. The complexes cis-Pt(Ypy)(pz)Cl2 were synthesized from the reaction of K[Pt(Ypy)Cl3] with pyrazine (1:1 proportion) in water. When the reaction was carried on in a 2:1 ratio, a mixture of compounds was obtained, which was refluxed in CH2Cl2 for several days. The final product was found to be pure and it was identified as trans,trans-Cl2(Ypy)Pt(μ-pyrazine)Pt(Ypy)Cl2. The cis monomers isomerize to the trans isomers in organic solvents. Different methyl derivatives of pyridine were studied in order to determine the influence of substitution in ortho position on the pyridine ligand in the complexes. In IR spectroscopy, the cis monomers showed two ν(Pt-Cl) bands, while the trans monomers and dinuclear species showed only one ν(Pt-Cl) band. The NMR results were interpreted in relation to the solvent effect, which seems important in these complexes. The 195Pt NMR signals of the cis monomers were found at slightly higher fields than those of the corresponding trans isomers. The coupling constants J(195Pt-1H) and J(195Pt-13C) are larger in the cis geometry. The δ(195Pt) of the dinuclear species were found close to those of the trans monomers and the coupling constants are similar to those of the trans monomers, strongly suggesting a trans-trans configuration for the dinuclear compounds. The pyrazine-bridged complex K2[Cl3Pt(μ-pz)PtCl3] was also synthesized and spectroscopically studied. The crystal structures of the compounds cis-Pt(3,5-lut)(pz)Cl2 and trans-Pt(2,4,6-col)(pz)Cl2 were determined by X-ray diffraction methods.  相似文献   

18.
The reaction of [ZnLI,II2] (LI = [NH2C(S)NP(O)(OiPr)2]; LII = [PhNHC(S)NP(O)(OiPr)2]) or [Cd2LIV4] (LIV = [PhC(S)NP(O)(OiPr)2]) with 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen) leads to the heteroligand complexes [Zn(bpy)LI,II2], [Zn(phen)LI,II2], [Cd(bpy)LIV2] or [Cd(phen)LIV2], respectively. The introduction of the diimine ligands into the coordination sphere of the metal cation provokes a change from 1,5-O,S- to 1,3-N,S-coordination of the anionic ligands for Zn but not for the Cd species. The reaction of [Zn(phen)LIV2] (LIV = PhC(S)NP(O)(OiPr)2) with CH2Cl2 cleaves the chlorine atoms from CH2Cl2 and leads to the formation of [Zn(phen)LIVCl] and S,S′-bis(benzimidothio-N-diisopropoxyphosphoryl)methane (LIV-CH2-LIV) in high yields. Using CHCl3 or CCl4 instead of CH2Cl2 does not lead to the formation of chlorine substituted products even under reflux conditions. The new compounds were investigated by 1H and 31P{1H} NMR, IR spectroscopy and microanalysis. Crystal structures of [ZnLII2], [Cd(phen)LIV2]·CH2Cl2, [Zn(bpy)LI2] and [Zn(phen)LIVCl] were elucidated by X-ray diffraction.  相似文献   

19.
20.
Ituarte S  Papeschi AG 《Genetica》2004,122(2):199-206
Male karyotype and meiosis of Tenagobia fuscata (Corixoidea, Micronectidae) are studied. The species possesses a male diploid chromosome number 2n = 28 + XY, holokinetic chromosomes, absence of m chromosomes and an achiasmatic male meiosis. Autosomes divide pre-reductionally while the sex chromosomes do so post-reductionally. Banding techniques (C, DAPI and CMA) show that large heterochromatic AT-GC rich bands are generally terminally located, although some interstitial bands are also detected. Many bivalents are heteromorphic for heterochromatin amount and location. This is the first report of a species with achiasmatic male meiosis within the Nepomorpha. These cytogenetic features markedly differ from all previous reports for 26 species of the superfamily Corixoidea. T. fuscata occurs in permanent shallow water bodies, and most known individuals are brachypterous. Their dispersion depends on occasional floodings of the water bodies they occupy. Since achiasmatic meiosis maintains groups of co-adapted genes, this feature could be an adaptive strategy of the species to the particular type of habitat and ecological niche it occupies.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号