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1.
D'Angelo P De Panfilis S Filipponi A Persson I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(10):3045-3055
This is the first systematic study exploring the potential of high-energy EXAFS as a structural tool for lanthanoids and third-row transition elements. The K-edge X-ray absorption spectra of the hydrated lanthanoid(III) ions both in aqueous solution and in solid trifluoromethanesulfonate salts have been studied. The K-edges of lanthanoids cover the energy range from 38 (La) to 65 keV (Lu), while the corresponding energy range for the L(3)-edges is 5.5 (La) to 9.2 keV (Lu). We show that the large widths of the core-hole states do not appreciably reduce the potential structural information in the high-energy K-edge EXAFS data. Moreover, for lanthanoid compounds, more accurate structural parameters are obtained from analysis of K-edge than from L(3)-edge EXAFS data. The main reasons are the much wider k range available and the absence of double-electron transitions, especially for the lighter lanthanoids. A comparative K- and L(3)-edge EXAFS data analysis of nonahydrated crystalline neodymium(III) trifluoromethanesulfonate demonstrates the clear advantages of K-edge analysis over conventionally performed studies at the L(3)-absorption edge for structural investigations of lanthanoid and third-row transition metal compounds. The coordination chemistry of the hydrated lanthanoid(III) ions in aqueous solution and solid trifluoromethanesulfonate salts, based on the results of both the K- and L(3)-edge EXAFS data, is thoroughly discussed in the next paper in this series (I. Persson, P. D'Angelo, S. De Panfilis, M. Sandstr?m, L. Eriksson, Chem. Eur. J. 2008, 14, DOI: 10.1002/chem.200701281). 相似文献
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Lindqvist-Reis P Persson I Sandström M 《Dalton transactions (Cambridge, England : 2003)》2006,(32):3868-3878
The structures of the hydrated scandium(III) ion and of the hydrated dimeric hydrolysis complex, [Sc2(mu-OH)2]4+, in acidic aqueous solutions have been characterized by X-ray absorption fine structure (XAFS) and large-angle X-ray scattering (LAXS) methods. Comparisons with crystalline reference compounds containing hydrated scandium(III) ions in well characterized six-, seven- and eight-coordinated polyhedra have been used to evaluate the coordination numbers and configurations in aqueous solution. In strongly acidic aqueous solution the structure of the hydrated scandium(III) ion is found to be similar to that of the eight-coordinated scandium(III) ion with distorted bicapped trigonal prismatic coordinating geometry in the crystalline [Sc(H2O)(8.0)](CF3SO3)3 compound. The EXAFS data reveal for the solution, as for the solid, a mean Sc-O bond distance of 2.17(1) Angstrom to six strongly bound prism water molecules, 2.32(4) Angstrom to one capping position, with possibly another capping position at about 2.5 Angstrom. The LAXS study supports this structural model and shows furthermore a second hydration sphere with approximately 12 water molecules at a mean Sc...O(II) distance of 4.27(3) Angstrom. In less acidic concentrated scandium(III) aqueous solutions, the dimeric hydrolysis product, [Sc2(mu-OH)2(H2O)10]4+, is the predominating species with seven-coordinated scandium(III) ions in a double hydroxo bridge and five terminal water molecules at a mean Sc-O bond distance of 2.145 Angstrom. Hexahydrated scandium(III) ions are found in the crystal structure of the double salt [Sc(H2O)6][Sc(CH3SO3)6], which crystallizes in the trigonal space group R3[combining macron] with Z = 6 and the unit cell dimensions a = 14.019(2) and c = 25.3805(5) Angstrom. The Sc-O distances in the two crystallographically unique, but nearly identical, [Sc(H2O)6]3+ entities (both with 3[combining macron] imposed crystallographic symmetry) are 2.085(6) and 2.086(5) Angstrom, while the mean Sc-O distance in the near octahedral [Sc(OSO2CH3)6]3- entities (with three-fold symmetry) is 2.078 Angstrom. 相似文献
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The local structure of the double perovskite (Sr2‐xCax)FeMoO6 (0 ≤ × ≤ 2.0) and Sr2CrMO6 (M = Mo, W) systems have been probed by extended X‐ray absorption fine structure (EXAFS) spectroscopy at the Fe and Cr K‐edges. We found Fe‐O (ave) distance apparently decreases from 1.999 Å (x = 0) to 1.991 Å (x = 1.0) in (Sr2‐xCax)FeMoO6 (tetragonal structure). When x is increased further from 1.5 to 2.0, the Fe‐O bond distance decreased from 2.034 Å to 2.012 Å (monoclinic structure). In addition, Cr‐O, Sr‐Cr, and Cr‐Mo bond distances in Sr2CrWO6 are all slightly larger than the bond distances of Sr2CrMoO6, which is due to the ionic radius of the W5+ (0.62 Å) which is larger than the ionic radius of Mo5+ (0.61 Å). The results are consistent with our XRD refinements data. 相似文献
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Rabinovich E Goldberg I Gross Z 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(44):12294-12301
Corrole complexes with gold(I) and gold(III) were synthesized and their structural, photophysical, and electrochemical properties investigated. This work includes the X-ray crystallography characterization of gold(I) and gold(III) complexes, both chelated by a corrole with fully brominated β-pyrrole carbon atoms. The mononuclear and chiral gold(I) corrole appears to be the first of its kind within the porphyrinoid family, while the most unique property of the gold(III) corrole is that it displays phosphorescence at ambient temperatures. 相似文献
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Tomoko Hashida Kohji Tashiro Yoshiaki Inaki 《Journal of Polymer Science.Polymer Physics》2003,41(22):2937-2948
The thermal behavior of poly(ethylene imine) (PEI) hydrates in a water vapor atmosphere was investigated through temperature‐dependent measurements of infrared spectra and X‐ray diffraction. Almost perfectly dried anhydrate melted at about 60 °C during the heating process. Anhydrate containing a small amount of water showed a phase transition to a mixture of hemihydrate and sesquihydrate around 40 °C, at which point the ethylene imine (EI)/water ratio was 1/0.5 in the hemihydrate and 1/1.5 in the sesquihydrate. The hemihydrate transferred to the sesquihydrate around 60 °C, and the latter melted above 80 °C. When the starting PEI sample contained a greater amount of water and consisted of hemihydrate and sesquihydrate, the hemihydrate transferred to the sesquihydrate via heating, and the latter melted around 75 °C. For a sample of dihydrate (EI/water ratio = 1/2) containing an appreciably large amount of water, it transferred to the sesquihydrate around 65 °C, and the latter melted above 90 °C. A sample of dihydrate with a much higher water content existed up to 110 °C and then melted; during this period, no transition to the sesquihydrate was observed. In this way, the starting crystalline phases were found to change for anhydrate and various types of hydrates. Their transition behaviors varied according to the water content. From these data, a phase diagram was successfully derived as a function of the temperature and water content. This phase diagram allowed us to predict the transition behavior during the hydration process at various constant temperatures. For example, at 60 °C, a molten sample should crystallize into a mixture of hemihydrate and sesquihydrate at first, and the hemihydrate should transfer to the sesquihydrate with increasing water content. The latter should change to the dihydrate in the final stage. This prediction was checked with time‐resolved measurements of X‐ray diffraction and infrared spectra during the hydration process at the corresponding temperature; this led to the establishment of the phase diagram. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2937–2948, 2003 相似文献
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The β‐pyranose isomer of D ‐galactosylamine ( 1 ) formed complexes with three different cobalt(III) fragments. Crystals containing the dication [Co(tren)(β‐D ‐Galp1N2H–1‐κ2N1,O2)]2+ ( 3 ) showed coordination through the anomeric amino group (N1) and the deprotonated hydroxy group (O2) of the 4C1 β‐pyranose form, which is also the major isomer of free galactosylamine. The cationic complexes [Co(fac‐dien)(β‐D ‐Galp1N2H–1‐κ2N1,O2)]2+ ( 4 ) and [Co(phen)2(β‐D ‐Galp1N2H–1‐κ2N1,O2)]2+ ( 5 ) were analysed by NMR spectroscopy and showed the same coordination mode as 3 . In terms of available ligand isomers it was shown that 1 exhibits an anomeric equilibrium in solution of both pyranose and both furanose forms as is typical for the parent glycose, galactose. 相似文献
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Eulgem PJ Klein A Maggiarosa N Naumann D Pohl RW 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(12):3727-3736
From the two nitrogen-rich ligands BT(2-) (BT=5,5'-bitetrazole) and BTT(3-) (BTT=1,3-bis(1H-tetrazol-5-yl)triazene), a series of novel rare earth metal complexes were synthesised. For the BT ligand, a vast number of these complexes could be structurally characterised by single-crystal XRD, revealing structures ranging from discrete molecular aggregates to salt-like compounds. The isomorphous complexes [La2(BT)3]14 H2O (1) and [Ce2(BT)3]14 H2O (2) reveal discrete molecules in which one BT(2-) acts as a bridging ligand and two BT groups as chelating ligands. The complexes, [M(BT)(H2O)7]2[BT] x (x) H2O (3-5), (M=Nd (3), Sm (4), and Eu (5)), are also isomorphous and consist of [M(BT)(H2O)7]+ ions in which only one BT(2-) acts as a chelate ligand for each metal centre. [Tb(H2O)8]2[BT]3 x H2O (6) and [Er(H2O)8](2)[BT](3)x H2O (7) are salt-like compounds that do not exhibit any significant metal-nitrogen contacts. In the BTT-samarium compound 9, discrete molecules were found in which BTT(3-) acts as a tridentate ligand with three Sm--N bonds. 相似文献
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1-Boraadamantane 1 was treated with alkyn-1-ylsilanes 2 containing one or two Si[bond]H functions. Under mild conditions, the reaction gave 4-methylene-3-borahomoadamantane derivatives 4 quantitatively and selectively by 1,1-organoboration. An electron deficient Si-H-B bridge was present in the product. The analogous reaction of 1 with an alkyn-1-yl-disilane 3 gave the corresponding alkene derivative 5, however, without the Si-H-B bridge. Evidence for the Si-H-B bridge in 4 was given by IR data, an extensive set of NMR spectroscopical data ((1)H, (11)B, (13)C, (29)Si NMR) including various unusual isotope effects on chemical shifts and coupling constants, as well as from the molecular structure of one example, 4 e, in the solid state. The precursor of 4 e, alkyne 2 e, Ph(2)Si(H)C[triple bond]CSi(H)Ph(2), was also studied by X-ray analysis. 相似文献
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Facially amphiphilic (FA) phenylene ethynylene (PE) polymers that self-assemble in aqueous solution were studied by small-angle X-ray diffraction (SAXD) and found to self-assemble into bilayers with a fully extended backbone. The resulting bilayers have long-range liquid-crystalline order. This self-assembly is programmed into the molecule by placing polar and nonpolar groups at precise locations so that they segregate onto opposite sides of the molecular structure. The absence of FA patterning generated an amorphous sample confirming the importance of this programmed amphiphilicity in the self-assembly process. Facially amphiphilic patterning represents a new design criterion for supramolecular chemistry, illustrated here in the observation of molecular ordering into bilayers reminiscent of self-assembled structures commonly found in biology, including amphiphilic beta-sheet polypeptides and phospholipid bilayers. 相似文献
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Cover Picture: Isolatable Organophosphorus(III)–Tellurium Heterocycles (Chem. Eur. J. 3/2014)
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Andreas Nordheider Tristram Chivers Oliver Schön Konstantin Karaghiosoff Kasun S. Athukorala Arachchige Alexandra M. Z. Slawin Prof. Dr. J. Derek Woollins 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(3):613-613
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Schäfer A Winter F Saak W Haase D Pöttgen R Müller T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(39):10979-10984
The reactivity of aryl‐substituted stannylenes, Ar2Sn ( 4 ), towards silylarenium borates, [R3SiArH][B(C6F5)4] ( 3 ), was investigated. The reaction with 2,3,4‐trimethyl‐6‐tert‐butylphenyl (mebp)‐substituted stannylene gave silyl‐substituted stannylium ions 2 a , b , which were characterized by NMR spectroscopy supported by the results of quantum‐mechanical computations of molecular structures and magnetic properties. The tri‐iso‐propylphenyl‐substituted stannylium ions 2 c , d undergo a decomposition reaction in toluene to give the dicationic tin–arene complex [Sn(C7H8)3]2+ ( 5 ) in the form of the [B(C6F5)4] salt in high yields. The 5 [B(C6F5)4]2 salt was identified by single crystal X‐ray diffraction analysis and by Mössbauer spectroscopy. The bonding situation was investigated by using natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) calculations. The substitution of the weakly coordinating borate anion by the carboranate [CB11H6Br6]? results in replacement of the toluene ligands and formation of tin(II) carboranate with only weak Sn2+–anion interactions as suggested by the solid‐state structure of the isolated salt. 相似文献
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Spectroscopic Observation of the Hydroxy Position in Butanol Hydrates and Its Effect on Hydrate Stability
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In this study, we investigate the crystal structures and phase equilibria of butanols+CH4+H2O systems to reveal the hydroxy group positioning and its effects on hydrate stability. Four clathrate hydrates formed by structural butanol isomers are identified with powder X‐ray diffraction (PXRD). In addition, Raman spectroscopy is used to analyze the guest distributions and inclusion behaviors of large alcohol molecules in these hydrate systems. The existence of a free OH indicates that guest molecules can be captured in the large cages of structure II hydrates without any hydrogen‐bonding interactions between the hydroxy group of the guests and the water‐host framework. However, Raman spectra of the binary (1‐butanol+CH4) hydrate do not show the free OH signal, indicating that there could be possible hydrogen‐bonding interactions between the guests and hosts. We also measure the four‐phase equilibrium conditions of the butanols+CH4+H2O systems. 相似文献
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Single crystals of [Yb(NCS)3(H2O)5] · H2O were synthesized from a salt‐metathesis reaction between stoichiometric amounts of aqueous solutions of Yb2(SO4)3 · 8H2O and Ba(NCS)2 · 3H2O driven by the precipitation of Ba(SO4), followed by isothermic evaporation of the filtered‐off solution at room temperature under atmospheric conditions. These crystals of the title compound came as transparent, colorless and hygroscopic needles. According to the X‐ray diffraction structure analysis [Yb(NCS)3(H2O)5] · H2O crystallizes in the monoclinic space group P21 with the lattice parameters a = 845.38(5), b = 719.26(4), c = 1219.65(7) pm, β = 103.852(3)° for Z = 2. The acentric crystal structure contains crystallographically unique Yb3+ cations, each surrounded by three thiocyanate anions, all grafting with their nitrogen atoms, and five water molecules forming a neutral [Yb(NCS)3(H2O)5] complex with square antiprismatic shape, completed by a sixth interstitial water molecule. ATR‐FT infrared and single‐crystal Raman spectra of [Yb(NCS)3(H2O)5] · H2O confirm these findings. 相似文献