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81.
Busby M Hartl F Matousek P Towrie M Vlcek A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(23):6912-6923
Two multifunctional photoactive complexes [Re(Cl)(CO)(3)(MeDpe(+))(2)](2+) and [Re(MeDpe(+))(CO)(3)(bpy)](2+) (MeDpe(+)=N-methyl-4-[trans-2-(4-pyridyl)ethenyl]pyridinium, bpy=2,2'-bipyridine) were synthesized, characterized, and their redox and photonic properties were investigated by cyclic voltammetry; ultraviolet-visible-infrared (UV/Vis/IR) spectroelectrochemistry, stationary UV/Vis and resonance Raman spectroscopy; photolysis; picosecond time-resolved absorption spectroscopy in the visible and infrared regions; and time-resolved resonance Raman spectroscopy. The first reduction step of either complex occurs at about -1.1 V versus Fc/Fc(+) and is localized at MeDpe(+). Reduction alone does not induce a trans-->cis isomerization of MeDpe(+). [Re(Cl)(CO)(3)(MeDpe(+))(2)](2+) is photostable, while [Re(MeDpe(+))(CO)(3)(bpy)](2+) and free MeDpe(+) isomerize under near-UV irradiation. The lowest excited state of [Re(Cl)(CO)(3)(MeDpe(+))(2)](2+) has been identified as the Re(Cl)(CO)(3)-->MeDpe(+ 3)MLCT (MLCT=metal-to-ligand charge transfer), decaying directly to the ground state with lifetimes of approximately 42 (73 %) and approximately 430 ps (27 %). Optical excitation of [Re(MeDpe(+))(CO)(3)(bpy)](2+) leads to population of Re(CO)(3)-->MeDpe(+) and Re(CO)(3)-->bpy (3)MLCT states, from which a MeDpe(+) localized intraligand (3)pipi* excited state ((3)IL) is populated with lifetimes of approximately 0.6 and approximately 10 ps, respectively. The (3)IL state undergoes a approximately 21 ps internal rotation, which eventually produces the cis isomer on a much longer timescale. The different excited-state behavior of the two complexes and the absence of thermodynamically favorable interligand electron transfer in excited [Re(MeDpe(+))(CO)(3)(bpy)](2+) reflect the fine energetic balance between excited states of different orbital origin, which can be tuned by subtle structural variations. The complex [Re(MeDpe(+))(CO)(3)(bpy)](2+) emerges as a prototypical, multifunctional species with complementary redox and photonic behavior. 相似文献
82.
Larissa R. Cohen Laura A. Pe?a Anton J. Seidl Janet M. Olsen Jennifer Wekselbaum Patrick E. Hoggard 《Monatshefte für Chemie / Chemical Monthly》2009,34(2):1159-1165
Abstract
Near-UV irradiation of solutions of (Bu4N)AuCl4 in aerated ethanol-stabilized chloroform causes the continuous decomposition of chloroform, as evidenced by the production of many equivalents of HCl and peroxides. At the outset of irradiation, most of the AuCl4 − is reduced to AuCl2 −, but the reduction stops and is reversed. The same experiments done in ethanol-free chloroform cause chloroform decomposition only until the irreversible reduction of the gold is complete. In deoxygenated ethanol-free chloroform, irreversible reduction to AuCl2 − is accompanied by the formation of HCl and CCl4, while the main decomposition products in deoxygenated ethanol-stabilized chloroform are HCl and C2Cl6. It is proposed that, in ethanol-free chloroform, photoreduction of AuCl4 − begins with the concerted elimination of HCl from an association complex of CHCl3 with AuCl4 −, and that ethanol suppresses { \textCHCl3 ·\textAuCl4 - } \{ {\text{CHCl}}_{3} \cdot {\text{AuCl}}_{4}^{ - } \} complex formation, leaving a slower radical process to carry out the photoreduction of AuCl4 − in ethanol-stabilized chloroform. In the presence of oxygen, the radical process causes a build-up of CCl3OOH, which reoxidizes AuCl2 − to AuCl4 − and allows the photodecomposition of CHCl3 to continue indefinitely. 相似文献83.
Matic Lozinšek Evgeny Goreshnik Anton Meden Gašper Tav?ar 《Journal of solid state chemistry》2009,182(10):2897-2903
In the system BaF2/BF3/PF5/anhydrous hydrogen fluoride (aHF) a compound Ba(BF4)(PF6) was isolated and characterized by Raman spectroscopy and X-ray diffraction on the single crystal. Ba(BF4)(PF6) crystallizes in a hexagonal space group with a=10.2251(4) Å, c=6.1535(4) Å, V=557.17(5) Å3 at 200 K, and Z=3. Both crystallographically independent Ba atoms possess coordination polyhedra in the shape of tri-capped trigonal prisms, which include F atoms from BF4− and PF6− anions. In the analogous system with AsF5 instead of PF5 the compound Ba(BF4)(AsF6) was isolated and characterized. It crystallizes in an orthorhombic Pnma space group with a=10.415(2) Å, b=6.325(3) Å, c=11.8297(17) Å, V=779.3(4) Å3 at 200 K, and Z=4. The coordination around Ba atom is in the shape of slightly distorted tri-capped trigonal prism which includes five F atoms from AsF6− and four F atoms from BF4− anions. When the system BaF2/BF3/AsF5/aHF is made basic with an extra addition of BaF2, the compound Ba2(BF4)2(AsF6)(H3F4) was obtained. It crystallizes in a hexagonal P63/mmc space group with a=6.8709(9) Å, c=17.327(8) Å, V=708.4(4) Å3 at 200 K, and Z=2. The barium environment in the shape of tetra-capped distorted trigonal prism involves 10 F atoms from four BF4−, three AsF6− and three H3F4− anions. All F atoms, except the central atom in H3F4 moiety, act as μ2-bridges yielding a complex 3-D structural network. 相似文献
84.
Dostál L Jambor R Růzicka A Lycka A Holecek J 《Magnetic resonance in chemistry : MRC》2006,44(2):171-173
The 17O chemical shifts of substituted benzyl ethers and a set of organotin(IV) derivatives containing O,C,O-chelating ligands were studied. Measured 17O chemical shifts were correlated with the additivity substituent increments for carbon atoms in the alkyl groups, and intramolecular Sn-O distance was obtained by X-ray diffraction techniques in the solid state. 相似文献
85.
86.
Ignat'eva DV Goryunkov AA Tamm NB Ioffe IN Avdoshenko SM Sidorov LN Dimitrov A Kemnitz E Troyanov SI 《Chemical communications (Cambridge, England)》2006,(16):1778-1780
Two isomers of C70(CF3)12 have been isolated from a mixture obtained by trifluoromethylation of C70 with CF3I; their molecular structures determined by X-ray crystallography are in good agreement with the results of theoretical DFT calculations for the most stable C70(CF3)12 isomers. 相似文献
87.
Myron S. Huzan Manuel Fix Matteo Aramini Peter Bencok J. Frederick W. Mosselmans Shusaku Hayama Franziska A. Breitner Leland B. Gee Charles J. Titus Marie-Anne Arrio Anton Jesche Michael L. Baker 《Chemical science》2020,11(43):11801
Large single-ion magnetic anisotropy is observed in lithium nitride doped with iron. The iron sites are two-coordinate, putting iron doped lithium nitride amongst a growing number of two coordinate transition metal single-ion magnets (SIMs). Uniquely, the relaxation times to magnetisation reversal are over two orders of magnitude longer in iron doped lithium nitride than other 3d-metal SIMs, and comparable with high-performance lanthanide-based SIMs. To understand the origin of these enhanced magnetic properties a detailed characterisation of electronic structure is presented. Access to dopant electronic structure calls for atomic specific techniques, hence a combination of detailed single-crystal X-ray absorption and emission spectroscopies are applied. Together K-edge, L2,3-edge and Kβ X-ray spectroscopies probe local geometry and electronic structure, identifying iron doped lithium nitride to be a prototype, solid-state SIM, clean of stoichiometric vacancies where Fe lattice sites are geometrically equivalent. Extended X-ray absorption fine structure and angular dependent single-crystal X-ray absorption near edge spectroscopy measurements determine FeI dopant ions to be linearly coordinated, occupying a D6h symmetry pocket. The dopant engages in strong 3dπ-bonding, resulting in an exceptionally short Fe–N bond length (1.873(7) Å) and rigorous linearity. It is proposed that this structure protects dopant sites from Renner–Teller vibronic coupling and pseudo Jahn–Teller distortions, enhancing magnetic properties with respect to molecular-based linear complexes. The Fe ligand field is quantified by L2,3-edge XAS from which the energy reduction of 3dz2 due to strong 4s mixing is deduced. Quantification of magnetic anisotropy barriers in low concentration dopant sites is inhibited by many established methods, including far-infrared and neutron scattering. We deduce variable temperature L3-edge XAS can be applied to quantify the J = 7/2 magnetic anisotropy barrier, 34.80 meV (∼280 cm−1), that corresponds with Orbach relaxation via the first excited, MJ = ±5/2 doublet. The results demonstrate that dopant sites within solid-state host lattices could offer a viable alternative to rare-earth bulk magnets and high-performance SIMs, where the host matrix can be tailored to impose high symmetry and control lattice induced relaxation effects.Taking advantage of synchrotron light source methods, we present the geometric and electronic structure of iron doped in lithium nitride. 相似文献
88.
Berendsen CW Zeegers JC Kruis GC Riepen M Darhuber AA 《Langmuir : the ACS journal of surfaces and colloids》2012,28(26):9977-9985
Thin liquid films on partially wetting substrates are subjected to laminar axisymmetric air-jets impinging at normal incidence. We measured the time at which film rupture occurs and dewetting commences as a function of diameter and Reynolds number of the air-jet. We developed numerical models for the air flow as well as the height evolution of the thin liquid film. The experimental results were compared with numerical simulations based on the lubrication approximation and a phenomenological expression for the disjoining pressure. We achieved quantitative agreement for the rupture times. We found that the film thickness profiles were highly sensitive to the presence of minute quantities of surface-active contaminants. 相似文献
89.
Busby M Gabrielsson A Matousek P Towrie M Di Bilio AJ Gray HB Vlcek A 《Inorganic chemistry》2004,43(16):4994-5002
The nature and dynamics of the lowest excited states of fac-[Re(I)(L)(CO)(3)(phen)](+) and fac-[Re(I)(L)(CO)(3)(5-NO(2)-phen)](+) [L = Cl(-), 4-ethyl-pyridine (4-Etpy), imidazole (imH); phen = 1,10-phenanthroline] have been investigated by picosecond visible and IR transient absorption spectroscopy in aqueous (L = imH), acetonitrile (L = 4-Etpy, imH), and MeOH (L = imH) solutions. The phen complexes have long-lived Re(I) --> phen (3)MLCT excited states, characterized by CO stretching frequencies that are upshifted relative to their ground-state values and by widely split IR bands due to the out-of-phase A'(2) and A"nu(CO) vibrations. The lowest excited states of the 5-NO(2)-phen complexes also have (3)MLCT character; the larger upward nu(CO) shifts accord with much more extensive charge transfer from the Re(I)(CO)(3) unit to 5-NO(2)-phen in these states. Transient visible absorption spectra indicate that the excited electron is delocalized over the 5-NO(2)-phen ligand, which acquires radical anionic character. Similarly, involvement of the -NO(2) group in the Franck-Condon MLCT transition is manifested by the presence of an enhanced nu(NO(2)) band in the preresonance Raman spectrum of [Re(I)(4-Etpy)(CO)(3)(5-NO(2)-phen)](+). The Re(I) --> 5-NO(2)-phen (3)MLCT excited states are very short-lived: 7.6, 170, and 43 ps for L = Cl(-), 4-Etpy, and imH, respectively, in CH(3)CN solutions. The (3)MLCT excited state of [Re(I)(imH)(CO)(3)(5-NO(2)-phen)](+) is even shorter-lived in MeOH (15 ps) and H(2)O (1.3 ps). In addition to (3)MLCT, excitation of [Re(I)(imH)(CO)(3)(5-NO(2)-phen)](+) populates a (3)LLCT (imH --> 5-NO(2)-phen) excited state. Most of the (3)LLCT population decays to the ground state (time constants of 19 (H(2)O), 50 (MeOH), and 72 ps (CH(3)CN)); in a small fraction, however, deprotonation of the imH.+ ligand occurs, producing a long-lived species, [Re(I)(im.)(CO)(3)(5-NO(2)-phen).-]+. 相似文献
90.