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971.
972.
Mizukami S Houjou H Kanesato M Hiratani K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(7):1521-1528
Control of self-assembled nanostructures is a promising technique for nanotechnology. We have examined as to whether nanostructures could be controlled by the size of the central metal ion. Lanthanides are a natural choice for such a study as the size of their trivalent ions changes with atomic number gradually. For this investigation, a series of rare earth complexes ([LaL(1)], [CeL(1)], [SmL(1)], [TbL(1)], [YL(1)], and [LuL(1)]) with a tripodal heptadentate ligand L(1) were synthesized, and their X-ray crystallographic analysis was performed. Although the structures of the ligand (H(3)L(1)) and of the metal complex ([ML(1)]) were quite different, all complexes were almost isostructural pseudohelices. The result of the crystallographic studies demonstrated that the twist angles of helices in the complexes depend on the ionic size of the central metal. A detailed analysis helped determine which portion of the helical strand contributed to the total helicity, and the major cause for the difference in helicity among the lanthanides is discussed. Moreover, this result is the first example showing that La(I) (II) and Lu(I) (II) complexes with the same tripodal heptadentate ligand are isostractural. 相似文献
973.
974.
本文应用14个镧系元素(Ⅲ)对有机化合物中的磷和氟进行了测定,阐明了影响测定的因素。测定的误差:磷为±0.20%,氟为±0.30%。 相似文献
975.
We investigate the luminescent properties of potassium wolframylphosphate glasses doped with Eu3+, Tb3+, and Dy3+ ions whose luminescence is excited by donor-acceptor interaction between the active WO
2
2+
and Ln3+ ions, as well as the migration of energy in the subsystems of each type of the active ions. Comparison of the obtained data
with the results of investigation of the spectroscopic properties of Ln3+ in uranylphosphate materials shows that a sufficiently high degree of the ionicity of bonds of Ln3+ with the atoms of its first coordination sphere is preserved in wolframylphosphate matrices. We show that three stages of
the decomposition of electron excitations are typical of the WO
2
2+
ions in wolframylphosphate glasses doped with Ln3+ and two stages in nonactivated glasses. The electron excitation energy transfer in the WO
2
2+
−Ln3+ system occurs due to induction-resonance interaction.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 620–625, September–October, 1997. 相似文献
976.
Svetlana B. Meshkova 《Journal of fluorescence》2000,10(4):333-337
The influence of -diketone forms on the luminescence intensity of lanthanide compounds in a series of ligands, acetylacetone (trifluoroacetylacetone, benzoylacetone)—their unsaturated analogues (monomeric form)—copolymers of the latter with styrene (methylmethacrylate), was studied. Lanthanides in compounds with copolymers have been established to demonstrate the brightest luminescence. It was found that its intensity depends not only on the character of the substituent (CH3, CF3, C6H5) in the -diketone molecule, but also on the distance between the -diketone fragments in the copolymer. Reasons explaining the high intensity of luminescence in lanthanide–copolymer compounds are considered. 相似文献
977.
A. Ke¸dziorski 《Journal of luminescence》2007,127(2):552-560
978.
Violeta A. Vetsova Dr. Katherine R. Fisher Dr. Henning Lumpe Alexander Schäfer Erik K. Schneider Dr. Patrick Weis Prof. Dr. Lena J. Daumann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(39):10087-10098
Understanding the role of metal ions in biology can lead to the development of new catalysts for several industrially important transformations. Lanthanides are the most recent group of metal ions that have been shown to be important in biology, that is, in quinone-dependent methanol dehydrogenases (MDH). Here we evaluate a literature-known pyrroloquinoline quinone (PQQ) and 1-aza-15-crown-5 based ligand platform as scaffold for Ca2+, Ba2+, La3+ and Lu3+ biomimetics of MDH and we evaluate the importance of ligand design, charge, size, counterions and base for the alcohol oxidation reaction using NMR spectroscopy. In addition, we report a new straightforward synthetic route (3 steps instead of 11 and 33 % instead of 0.6 % yield) for biomimetic ligands based on PQQ. We show that when studying biomimetics for MDH, larger metal ions and those with lower charge in this case promote the dehydrogenation reaction more effectively and that this is likely an effect of the ligand design which must be considered when studying biomimetics. To gain more information on the structures and impact of counterions of the complexes, we performed collision induced dissociation (CID) experiments and observe that the nitrates are more tightly bound than the triflates. To resolve the structure of the complexes in the gas phase we combined DFT-calculations and ion mobility measurements (IMS). Furthermore, we characterized the obtained complexes and reaction mixtures using Electron Paramagnetic Resonance (EPR) spectroscopy and show the presence of a small amount of quinone-based radical. 相似文献
979.
980.
Nag A Lotsch BV Schmedt Auf der Günne J Oeckler O Schmidt PJ Schnick W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(12):3512-3524
The rare-earth tricyanomelaminates, [NH(4)]Ln[HC(6)N(9)](2)[H(2)O](7)xH(2)O (LnTCM; Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy), have been synthesized through ion-exchange reactions. They have been characterized by powder as well as single-crystal X-ray diffraction analysis, vibrational spectroscopy, and solid-state (1)H, (13)C, and (15)N MAS NMR spectroscopy. The X-ray powder pattern common to all nine rare-earth tricyanomelaminates LnTCM (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy) indicates that they are isostructural. The single-crystal X-ray diffraction pattern of LnTCM is indicative of non-merohedral twinning. The crystals are triclinic and separation of the twin domains as well as refinement of the structure were successfully carried out in the space group P1 for LaTCM (LaTCM; P1, Z=2, a=7.1014(14), b=13.194(3), c=13.803(3) A, alpha=90.11(3), beta=77.85(3), gamma=87.23(3) degrees , V=1262.8(4) A(3)). In the crystal structure, each Ln(3+) is surrounded by two nitrogen atoms from two crystallographically independent tricyanomelaminate moieties and seven oxygen atoms from crystal water molecules. The positions of all of the hydrogen atoms of the ammonium ions and water molecules could not be located from difference Fourier syntheses. The presence of [NH(4)](+) ions as well as two NH groups belonging to two crystallographically independent monoprotonated tricyanomelaminate moieties has only been confirmed by subjecting LaTCM to solid-state (1)H, (13)C, and (15)N{(1)H} cross-polarization (CP) MAS NMR and advanced CP experiments such as cross-polarization combined with polarization inversion (CPPI). The (1)H 2D double-quantum single-quantum homonuclear correlation (DQ SQ) spectrum and the (15)N{(1)H} 2D CP heteronuclear-correlation (HETCOR) spectrum have revealed the hydrogen-bonded (N--HN) dimer of monoprotonated tricyanomelaminate moieties as well as H-bonding through [NH(4)](+) ions and H(2)O molecules. The structures of the other eight rare-earth tricyanomelaminates (LnTCM; Ln=Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy) have been refined from X-ray powder diffraction data by the Rietveld method. Photoluminescence studies of [NH(4)]Eu[HC(6)N(9)](2)[H(2)O](7)xH(2)O have revealed orange-red (lambda(max)=615 nm) emission due to the (5)D(0)-(7)F(2) transition, whereas [NH(4)]Tb[HC(6)N(9)](2)[H(2)O](7)xH(2)O has been found to show green emission with a maximum at 545 nm arising from the (5)D(4)-(7)F(5) transition. DTA/TG studies of [NH(4)]Ln[HC(6)N(9)](2)[H(2)O](7)xH(2)O have indicated several phase transitions associated with dehydration of the compounds above 150 degrees C and decomposition above 200 degrees C. 相似文献