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 491 毫秒
1.
The ligand 2,6-bis(1-methylbenzimidazol-2-yl)pyridine (mbzimpy, 1 ) reacts with EuIII to give [Eu(mbzimpy)(NO3)3(CH3OH)] [ 4 ] whose crystal structure (EuC22H21N8O10, a = 7.658(3) Å, b = 19.136(2) Å, c = 8.882 Å, β = 104.07(1)°, monoclinic, P21, Z = 2) shows a mononuclear structure where EuIII is ten-coordinate by a meridional tridentate mbzimpy ligand, three bidentate nitrates, and one CH3OH molecule, leading to a low-symmetry coordination sphere around the metalion. Essentially the same coordination is found in the crystal structure of [Eu(obzimpy)(NO3)3] ( 8 ) (EuC35H45N8O9, a = 9.095(2) Å, b = 16.624(2) Å, c = 26.198(6) Å, β = 95.85(1)°, monoclinic, P21/c, Z = 4) obtained by reaction of 2,6-bis(1-octylbenzimidazol-2-yl)pyridine (obzimpy, 2 ) with EuIII. Detailed photophysical studies of crystalline [Ln(mbzimpy)(NO3)3(CH3OH)] and [Ln(obzimpy)(NO3)3] complexes (Ln = Eu, Gd, Tb, Lu) show that 1 and 2 display 1ππ* and 3ππ* excited states very similar to those observed in 2,2′:6′,2″-terpyridine, leading to efficient ligand to LnIII intramolecular energy transfer. Spectroscopic results show that an extremely efficient mbzimpy-to-EuIII transfer occurs in [Ln(mbzimpy)(NO3)3(CH3OH)] and in the case of TbIII, a TbIII-to-mbzimpy back transfer is also implied in the deactivation process. The origin of these peculiar effects and the influence of ligand design by going from mbzimpy to obzimpy are discussed. 1H-NMR and luminescence data indicate that the structure found in the crystal is essentially maintained in solution.  相似文献   

2.
Magneto optical devices based on the Faraday effects of lanthanide ion have attracted much attention. Recently, large Faraday effects were found in nano‐sized multinuclear lanthanide complexes. In this study, the Faraday rotation intensities were estimated for lanthanide nitrates [LnIII(NO3)3?n H2O: Ln=Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm) and EuIII complexes with β‐diketone ligands, using magnetic circular dichroism. Eu ions exhibit the largest Faraday rotation intensity for 7F05D1 transitions, and high‐symmetry fields around the Eu ions induce larger Faraday effects. The molecular design for the enhancement of Faraday effects in lanthanide complexes is discussed.  相似文献   

3.
Anhydrous solutions of Eu(ClO4)3 and Eu (NO3)3 0.05m in N, N-dimethyl formamide (DMF) are investigated by means of conductometric measurements, vibrational spectroscopy, electronic absorption and emission spectra, and fluorescence lifetime determinations. Eu (ClO4)3 is completely dissociated and no inner-sphere interaction takes place between ClO4 and Eu3+ ions. The solvated species Eu (DMF) has a C2v-symmetry and x is probably equal to 8. A more complicated situation occurs for Eu (NO3)3, the solutions of which contain at least three different solvates; the predominant species is [Eu (NO3)2 (DMF)x?4]+ (≈80% of the total Eu-concentration) and it is more stable than the mononitrato complex [Eu (NO3) (DMF) X?2]2+; the neutral complex Eu (NO3)3 (DMF) x?6 is also present, as can be inferred from a high-resolution analysis of the 5D07F0 emission band. The absence of emission from the excited 5D1-level can be rationalized in terms of an efficient non-radiative deexcitation path through a vibrational mode of the DMF-molecules bonded to the central metal ion.  相似文献   

4.
The interaction between lanthanide ions LnIII (Ln = La, Nd, Sm–Dy, Er, Yb) and nitrate ions is investigated by FT-IR spectroscopy in dilute anhydrous MeCN solution. The work is performed for ratios R = [NO]t/[LnIII]t ranging from 0 to 8 and for solutions generally 0.05M in LnIII, prepared from anhydrous lanthanide perchlorates Ln(ClO4)3. When nitrate is progressively added to the Ln(ClO4)3 solutions, the formation of [Ln(NO3)n](3?n)+ species is clearly evidenced by the FT-IR spectra. All the NO3? ions are coordinated and bidentate. A quantitative study was performed using the v1 and v6 vibrational modes for coordinated NO ions. The average coordination numbers estimated for Nd, Eu, Tb, and Er in solutions of trinitrates are 9.0, 9.1, 8.3 and 8.2, respectively (±0.3 unit). In presence of an excess NO, these numbers become 9.8, 10.2, 10.0, 9.8, 9.9, and 9.9 (±0.3 unit) for La, Nd, Eu, Tb, Er, and Yb, respectively. No hexanitrato species forms under the experimental conditions used (R up to 8). The structural aspect of the various nitrato species is also investigated. In the pentanitrato species, all the ligands appear to be equivalent, while large inequivalences are observed for Ln(NO3)3 solutions. Since for the latter most of the absorption bands assigned to nitrate vibrations contain several components, a curve-fitting procedure has been used for decomposing the v2, v4 and v6 vibrations. There is a considerable difference between LnIII ions, the nitrate inequivalences being larger in the middle of the series.  相似文献   

5.
Synthesis and Structure of the Ternary Ammonium Nitrates (NH4)2[M(NO3)5] (M = Tb? Lu, Y) Single crystals of the ternary ammonium nitrates (NH4)2[M(NO3)5] (M = Tb? Lu, Y) are obtained from the solution of the sesquioxides in a melt of NH4NO3 and sublimation of the excess NH4NO3. In the crystal structure of (NH4)2[Tm(NO3)5] (trigonal, P31, Z = 3; a = 1 123.76(8), c = 930.1(1) pm; R = 0.062; Rw = 0.034) Tm3+ is surrounded by five bidentate nitrate ligands. The isolated [Tm(NO3)5]2? groups are held together by ammonium ions.  相似文献   

6.
IR. and Raman spectra of LnONO3 (50–4,000 cm?1, Ln?La, Gd, Eu, and Dy) are reported and discussed. The low frequency region of the spectra reflects the cubic structure of these compounds. The dimensions of the cubic unit cells determined by X-Ray powder diagrams are: 12.81 ± 0.05 Å for EuONO3, 12.69 ± 0.05 Å for GdONO3, and 12.67 ± 0.05 Å for DyONO3. The vibrational frequencies of the nitrato group are consistent with a bidentate nitrate of C2v symmetry. The synthesis of anhydrous Ln (NO3)3 (Ln?La, Gd, Eu, and Dy) by dehydration of the corresponding penta- or hexahydrates is described. The IR. and Raman spectra (50-4,000 cm?1) are analysed. Splitting of the bands point to a complex structure of these compounds. All six vibrational modes of the nitrato group are observed and the data are again consistent with bidentate NO?3 moieties. Finally, an analytical control of the purity of Ln (NO3)3 is suggested.  相似文献   

7.
The compounds of Eu(III) with nicotinic acid and enrofloxacin are synthesized. Their composition and structure are proved by the data of elemental analysis, IR and luminescence spectroscopy, powder and single crystal X-ray diffraction. By single crystal X-ray diffraction, the structure of the compound of Eu with nicotinic acid is identified as a centrosymmetric dimer with 4 carboxylate bridges of the composition Eu2(C6H4NO2)6·4H2O. The Stark structure of the 5 D 0-7 F j transitions in the mixed-ligand compounds of Eu(III) with nicotinic acid and enrofloxacin is determined. The bands of IR spectra are assigned; the conclusion about the bidentate coordination of ligands is made.  相似文献   

8.
The crystal and molecular Structure of bis[dinitrato-(2,5,8,15,18,21-hexaoxatricyclo[20.4.0.09,14]hexa-consane)europium(III)]pentakis(nitrato) europiate(III) ([Eu(NO3)2·LA]2[Eu(NO3)5]) has been determined from single-crystal X-ray diffraction. The complex crystallizes in the monoclinic space group P21/c (ITC No. 14): a = 13.614(3)Å, b = 21.697(4)Å, c = 22.591(5)Å, β = 107.15(2)°, Z = 4. The structure was refined to a final R value of 0.055 (Rw = 0.055). The asymmetric unit contains three independent ions with approximate C2 symmetry: [Eu(NO3)5]2? and two distinct [Eu(NO3)2.La]+ cations with the macrocyclic ligand in the cis-syn-cis-conformation (A-isomer). The Eu(III) ions are 10-coordinated with the following mean bond lengths: Eu? O(nitrate) = 2.46(3)Å in the anion and the two cations, Eu? O(ether) = 2.55(9)Å in both cations. For the uncomplexed A-and B-isomers, as well as for their complexes with various metal ions, a conformational analysis has been made on the six O-atoms of the ligand which can be considererd as a fluxional ring. In the presently reported europium complex cations, the oxygen-ring conformation is almost a perfect boat with the metal ions lying in the least-sqiares plane of the O-atoms (deviation: 0.02–0.05Å). The same conformation prevails in all the complexes containing the A-isomer(exception: dimethylthallium complex) and in most of the complexes with the B-isomer. For this isomer, a chair conformation is found in the uncomplexed ligand, in the sodium complex, and in the complex with dimethylthallium. The occurrence of these conformations is discussed with respect to the crystallographic symmetry of the complexes and the relative mean M? O and O? O distances.  相似文献   

9.
The metal ion sites of the 3:2 complex between europium nitrate and the A -isomer of dicyclohexyl-18-crown-6, [Eu(NO3)2(DC18C6)]2[Eu(NO3)5], have been probed by high-resolution excitation and emission spectra at 296 and 77 K. The [Eu(NO3)5]2? anion gives rise to a luminescent spectrum dominated by the 5D07F2 transition. The crystal-field splitting of the 7Fj levels is close to that observed for (Phe4As)2[Eu(NO3)5], pointing to a structurally similar pentakis(nitrato) species. The 5D07F0 excitation spectrum of the two crystallographically independent complex cations displays five maxima. A detailed analysis of the corresponding and selectively excited emission spectra leads to the following conclusions. Well differentiated spectra are assigned to different conformations of the complex cation, in which half of the ligand atoms, including O-atoms, Present large thermal motions. The other spectra are very similar and arise from slightly unequivalent [Eu(NO3)2(DC18C6)]+ moieties differing in the conformation of their ethylene bridges. This dimonstrates the sensitivity of the Eu(III) ion as conformational probe in the solid state.  相似文献   

10.
《Polyhedron》2001,20(15-16):2045-2053
Two new poly(pyrazolyl)borate ligands have been prepared: potassium tris[3-{(4-tbutyl)-pyrid-2-yl}-pyrazol-1-yl]hydroborate (KTpBuPy) which has three bidentate arms and is therefore hexadentate; and potassium bis[3-(2-pyridyl)-5-(methoxymethyl)pyrazol-1-yl]-dihydroborate (KBp(COC)Py) which has two bidentate arms and is therefore tetradentate. The crystal structures of their lanthanide complexes [La(TpBuPy)(NO3)2] and [La(Bp(COC)Py)2X] (X=nitrate or triflate) have been determined. In [La(TpBuPy)(NO3)2] the metal ion is ten-coordinate, from the hexadentate N-donor podand ligand and two bidentate nitrates. [La(Bp(COC)Py)2(NO3)] is also ten-coordinate, from two tetradentate ligands and a bidentate nitrate, but in [La(Bp(COC)Py)2(CF3SO3)] the metal ion is nine-coordinate because the triflate anion is monodentate. Two unexpected new complexes which arose from partial decomposition of the poly(pyrazolyl)borate ligands have also been characterised structurally. In [La(BuPypzH)3(O3SCF3)3] the metal ion is nine-coordinate from three bidentate pyrazolyl-pyridine arms (liberated by decomposition of KTpBuPy) and three triflate anions; there is extensive NH· · · O hydrogen-bonding between the pyrazolyl and triflate ligands. [Nd(TpPy)(BpPy)][Nd(PypzH)(NO3)4] was isolated from the reaction of hexadentate tris[3-(2-pyridyl)-pyrazol-1-yl]hydroborate (TpPy) with Nd(NO3)3. One of the TpPy ligands has lost one bidentate pyrazolyl-pyridine ‘arm’ (PypzH) to leave tetradentate tris[3-(2-pyridyl)-pyrazol-1-yl]dihydroborate (BpPy). In this structure, the cation [Nd(TpPy)(BpPy)]+ is ten-coordinate from inter-leaved hexadentate and tetradentate ligands, and the anion [Nd(PypzH)(NO3)4] is also ten-coordinate from the bidentate N-donor ligand PypzH and four bidentate nitrates.  相似文献   

11.
Synthesis and Structure of the First Anhydrous Ternary Lithium Nitrates of the Lanthanides, Li2[M(NO3)5] (M = La, Pr? Eu). Single crystals of the ternary lithium nitrates of the lanthanides, Li2[M(NO3)5] (M = La, Pr? Eu), are obtained by dissolving the respective anhydrous nitrate, previously obtained by dehydration of M(NO3)3 · 6 H2O at 180°C under vacuum, in a melt of LiNO3. In the crystal structure of Li2[Pr(NO3)5] (orthorhombic, Pnnm, Z = 4, a = 899.6(2), b = 1 052.7(2), c = 1 178.6(2)pm; R = 0.072, Rw = 0.034) there are two crystallographically different Pr3+ ions, each surrounded by six bidentate nitrate ligands. One nitrate group is bridging between Pr1 and Pr2 resulting in a winded chain, [(O2/2NO2/1)Pr1(NO3)4(O2/2NO2/1)Pr2(O2/2NO2/1)(NO3)4]5?, running along [010]. The chains are packed hexagonally and held together by lithium ions. The coordination polyhydron of Li+ may be described as a bicapped trigonal prism.  相似文献   

12.
Bi(NO3)3 reacts with cucurbit[8]uril, (Q8), in 3M HNO3 to give the title complex whose structure includes three discrete Bi complexes: [{Bi(NO3)(H2O)5}2(Q8)]4+ (CN of Bi = 9, both NO3 and cucurbit[8]uril are bidentate), [Bi(NO3)5]2— (CN of Bi = 10, all NO3 are bidentate), and [Bi(NO3)3(H2O)4] (CN of Bi = 10, all NO3 are bidentate).  相似文献   

13.
A mesogenic Schiff-base, N,N′-di-(4-decyloxysalicylidene)-1′,3′-diaminobenzene, H2ddsdbz (abbreviated as H2L), that exhibits a nematic mesophase was synthesized and its structure was studied by elemental analysis, mass spectrometry, NMR, and IR spectral techniques. The Schiff-base, H2L, upon condensation with hydrated lanthanide(III) nitrates yields LnIII complexes, [Ln2(LH2)3(NO3)4](NO3)2, where Ln?=?La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Ho. Analyses of the IR and NMR spectral data imply bidentate Schiff-base through two phenolate oxygen atoms in its zwitterionic form to LnIII, rendering the overall geometry of the complexes as a seven-coordinate polyhedron – possibly distorted mono-capped octahedron. Polarizing optical microscope and differential scanning calorimetry studies reveal that despite H2L being mesogenic, none of the LnIII complexes synthesized under this study exhibits mesomorphism.  相似文献   

14.
Seven lanthanide complexes [Ln(OPPh3)3(NO3)3] ( 1 – 3 ) (OPPh3 = triphenylphosphine oxide, Ln = Nd, Sm, Gd), [Dy(OPPh3)4(NO3)2](NO3) ( 4 ), [Ln(OPPh3)3(NO3)3]2 ( 5 – 7 ) (Ln = Pr, Eu, Gd) were synthesized by the reactions of different lanthanide salts and OPPh3 ligand in the air. These complexes were characterized by single‐crystal X‐ray diffraction analysis, elemental analysis, IR and fluorescence spectra. Structure analysis shows that complexes 1 – 4 are mononuclear complexes formed by OPPh3 ligands and nitrates. The asymmetric units of complexes 5 – 7 consist of two crystallographic‐separate molecules. Complex 1 is self‐assembled to construct a 2D layer‐structure of (4,4) net topology by hydrogen bond interactions. The other complexes show a 1D chain‐like structure that was assembled by OPPh3 ligands and nitrate ions through C–H ··· O interactions. Solid emission spectra of compounds 4 and 6 are assigned to the characteristic fluorescence of Tb3+ (λem = 480, 574 nm) and Eu3+ (λem = 552, 593, 619, 668 nm).  相似文献   

15.
Synthesis, Structure, and Thermolysis of the (NH4)3[M2(NO3)9] (M ? La? Gd) The ternary ammonium nitrates (NH4)3[M2(NO3)9] (M ? La-Gd) are obtained as single crystals from a solution of the respective sesquioxides in a melt of NH4NO3 and sublimation of the excess NH4NO3. In the crystal structure of (NH4)3[Pr2(NO3)9] (cubic, P4332, Z = 4, a = 1 377.0(1) pm, R = 0.038, Rw = 0.023) Pr3+ is surrounded by six bidentate nitrate ligands of which three are bridging to neighbouring Pr3+ ions. This results in a branched folded chain, held together by the NH4+ ions which occupy cavities in the structure. (NH4)3[Pr2(NO3)9] is the first intermediate product of the thermal decomposition of (NH4)2[Pr(NO3)5(H2O)2] · 2H2O.  相似文献   

16.
The crystal and molecular structure of bis[dinitrato-(2,4,8,15,18,21-hexaoxatricyclo[20.4.0.09,14]hexacosane)europium(III)]pentakis(nitrato)europiate(III) [Eu(NO3)2LB]2([Eu(NO3)5]), has been determined at 170 K from single-crystal X-ray diffraction. The complex crystallizes in the monoclinic space group P21/n (ITC No. 14): a = 16.338(3) Å, b = 15.704(3) Å, c = 24.474(4) Å, β = 97.73(1)°, Z = 4. The structure was refined to a final R value of 0.058 (Rw = 0.060). The asymmetric unit contains three independent ions lying on general positions: [Eu(NO3)5]2? and two distinct [Eu(NO3)2LB]+ cations with the macrocyclic ligand in the cis-anti-cis conformation (B-isomer). The EuIIIions are 10-coordinate with the following mean bond lengths: Eu–O(nitrate) = 2.48(2) Å in the anion and 2.45(2) Å in the two cations, Eu–O(ether) = 2.56(8) and 2.55(5) Å. Small but significant differences are observed between the two complex cations, especially with respect to the positions of the cyclohexyl substituent. A conformational analysis performed on the six O-atoms of the complex cations confirms the predictions of a simple model. The metal ion sites of the complex have been probed by high-resolution excitation and emission spectra at 296 and 77 K. The 5D07F0 excitation spectrum displays two main bands along with several other minor components. A detailed analysis of the corresponding and selectively excited emission spectra leads to the observation of three types of spectra corresponding to the three crystallographically different EuIII ions. Moreover, three minor sites are identified, one anionic and two cationic, with a population equal to ca. 10% of the population of the main sites. We interpret this finding as reflecting the presence of molecules with slightly different conformations.  相似文献   

17.
Abstract

A quaternary mixed ligand europium complex, [Eu(FA)2NO3bipy]2, has been synthesized, where FA = α-furancarboxylic acid anion and bipy=2,2′-bipyridine. The europium complex crystallizes in the triclinic system, space group P1. Its structure was determined by X-ray diffraction methods. The two europium ions in the dimer are held together by four carboxylate groups of furancarboxylic acid and each europium ion is further bonded to one chelated bidentate nitrate and one 2,2′-bipyridine molecule. The coordination modes of the four carboxylate groups are divided into two types, bidentate bridging and tridentate bridging, making a coordination number of 9. Excitation and luminescence spectra observed at 77 K show that the europium ion site in the crystal has low symmetry and emission 5D 17 FJ of the Eu3+ ion disappears after 20 μs.  相似文献   

18.
Double nitrates of Na and K having the composition 2MINO3·LnIII(NO3)3·2H2O(LnIII=Pr, Nd, Sm, Eu, Gd, Tb and Dy) and of Ni and Cu with the composition 3MII(NO3)2·2LnIII(NO3)3·24H2O (LnIII=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy) have been prepared and their -radiolytic decomposition studied up to 500 kGy. G(NO 2 ) values of K double nitrates at 230 kGy follow the order Dy3+>Pr3+=Nd3+=Sm3+>Tb3+>Eu3+> Gd3+·G(NO 2 3+ ) for NI double nitrates are higher than those of Cu double nitrates. Variation of G(NO 2 ) with cationic radii and the number of f electrons in lanthanide ion show a minimum at Eu. Thermal decomposition studies of double nitrates were also carried out.  相似文献   

19.
Two new complexes {[Eu(2, 4-DFBA)3 · (H2O)2] · H2O} n (1) and [Eu(2-BrBA)3 · H2O] n (2) (2, 4-DFBA = 2, 4-difluorobenzoate, 2-BrBA = 2-bromobenzoate) have been synthesized and characterized by single crystal X-ray diffraction. 1 has a 1-D chain structure, in which Eu(III) ions are bridged by single COO? groups and a 2-D supramolecular network is formed by hydrogen bond interactions. In 1, each Eu(III) is eight-coordinate with six oxygens from four 2,4-DFBA ligands and two waters. 2 has a 1-D chain structure, in which Eu(III) ions are bridged by bridging-chelating-bridging COO? groups. In 2, each Eu(III) ion is nine-coordinate with eight oxygens from five 2-BrBA ligands and one water. The two complexes exhibit intense luminescence at room temperature. The 5D07F j (j = 0–4) transition emissions of Eu(III) have been observed.  相似文献   

20.
The lanthanide complexes L2Ln(NO3)3 ( 3 ) and L′ 3[Ln(NO3)3]2 ( 5 ) (Stewart and Siddall III. J Inorg Nucl Chem 1971, 33, 2965–2970) were obtained, where L is the tetraethyl ester of ethylenediphosphonic acid ( 2 ), L′ is the tetraisopropyl ester of ethylenediphosphonic acid ( 4 ), and Ln is La, Ce, Sm, Eu, and Er. In extension of a former study, they were characterized additionally with NMR spectroscopy. In contrast to the compounds of type 3 , the erbium complex of the ligand L is consistent with the formula L3[Er(NO3)3]2. The crystal structure of the complex 3a (Ln = La) is determined by single crystal X‐ray diffraction. The complex is found to crystallize in the monoclinic space group C2/c with a = 15.1415(4) Å, b = 14.9749(4) Å, c = 18.3887(5) Å, β = 114.129(1)ˆ, T = 153 K, V = 3805.2(2) Å3, Z = 4, ρcalc = 1.622 g/cm3, R1 = 0.023, R2w = 0.058, S = 1.08 for all 6823 reflections. The complex 3a consists of polymer chains with bridged bidentate phosphonate ligands. The lanthanum atom is coordinated by ten oxygen atoms, six of them from the three bidentate nitrate ions, and four from the two phosphonate ligands. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:36–46, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20188  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