Structure-chiroptical property relationship of kinetically labile camphor-derivative beta-diketone Yb(III) complexes: do the adducts coexist as diastereomers or not?

The present work examines the relationship between the crystal structures and chiroptical properties of four chiral Yb(III) complexes with camphor-derivative beta-diketone ligands by means of solid-state circular dichroism (CD) spectroscopy. For the seven-coordinate complexes, [Yb(H(2)O)(d-hfc)(3)] (I) and [Yb(H(2)O)(l-hfc)(3)] (II) (d/l-hfc(-) = 3-heptafluorobutyryl-(+)/(-)-camphorate), the Lambda- and Delta-diastereomers coexist in their crystals and no apparent bisignate couplets are observed in their solid-state CD spectra. A theoretical study indicates that the ground-state energy difference between the two diastereomers I and II is only 0.913 kcal mol(-1), which explains why they could coexist in a crystal environment with the ratio of 1:1. While, eight-coordinate complexes Delta-[Yb(TPPO)(2)(d-hfc)(3)]center dot CHCl(3)center dot 3C(6)H(12) (III) and Lambda-[Yb(TPPO)(2)(l-hfc)(3)]center dot CHCl3 center dot 3C(6)H(12) (IV) (TPPO = triphenylphosphine oxide) are enantiopure in the solid-state, and typically negative and positive exciton splitting patterns around 330 nm are observed in their solid-state CD spectra. The solid-state CD spectra of these four complexes are in accordance with their X-ray single-crystal analyses. Besides, their solution CD spectra show that no particular isomer predominates in solution.NSFC[20973136, 20773098, 20673069]; NSF of Shanxi province[2007011021

Luminescent Materials for Volumetric Three-Dimensional Displays Based on Photoactivated Phosphorescence

True three-dimensional (3D) displays are the best display technologies and their breakthrough is primarily due to advancements in display media. In this paper, we propose two luminescent materials for a static volumetric 3D display based on photoactivated phosphorescence. The luminescent materials include (1) dimethyl sulfoxide (DMSO)/1-methyl-2-pyrrolidinone (NMP) or tetramethylene sulfoxide (TMSO) as the solvent and photochemically-deoxygenating reagent; (2) a metal phthalocyanine complex as the sensitizer; (3) a phosphorescent platinum complex as the emitter. The metal phthalocyanine complex, PdPrPc (PdBuPc), absorbs the light beam of 635 nm and the solvent scavenges the sensitized singlet oxygen. Light beams pass through a deoxygenated zone. The phosphorescent emitter, PtNI, absorbs the 440 nm light beam and phosphoresces only in the deoxygenated zone generated by the sensitizer. Phosphorescent voxels and high-contrast 3D images are well-defined at the intersection of 635 and 440 nm light beams

Dynamic chiral-at-metal stability of tetrakis(d/l-hfc)Ln(III) complexes capped with an alkali metal cation in solution

NSFC [20973136, 20773098]; NSF of Fujian Province [2010J01048]Chiral tetrakis(beta-diketonate) Ln(III) complexes Delta-[NaLa(d-hfc)(4)(CH3CN)] (1) and Delta-[NaLa(l-hfc)(4) (CH3CN)] (2) (d/l-hfc(-) = 3-heptafluo-robutylryl-(+)/(-)-camphorate) are a pair of enantiomers and crystallize in the same Sohncke space group (P2(1)2(1)2(1)) with dodecahedral (DD) geometry. Typically positive and negative exciton splitting patterns around 320 nm were observed in the solid-state circular dichroism (CD) spectra of complexes 1 and 2, which indicate that their shell configurational chiralities are. and., respectively. The apparent bisignate couplets in the solid-state CD spectra of [CsLn(d-hfc)(4)(H2O)] [Ln = La (3), Yb (5)] and [CsLn(l-hfc)(4)(H2O)] [Ln = La (4), Yb (6)] show that they are a pair of enantiomers and their absolute configurations are denoted. and., respectively. The crystallographic data of 5 reveals that its coordination polyhedron is the square antiprism (SAP) geometry and it undergoes a phase transition from triclinic (alpha phase, P1) to monoclinic (beta phase, C2) upon cooling. The difference between the two phases is brought about by the temperature dependent behaviour of the coordination water molecules, but this did not affect the configurational chirality of the Delta-SAP-[Yb(d-hfc)(4)](-) moiety. Furthermore, time-dependent CD, UV-vis and F-19 NMR were applied to study the solution behavior of these complexes. It was found that the chiral-at-metal stability of the three pairs of complexes is different and affected by both the Ln(3+) and M+ ion size. The results show that the Cs+ cation can retain the metal center chirality and stablize the structures of [Ln(d/l-hfc)(4)](-) or the dissociated tris(d/l-hfc) Ln(III) species in solution for a longer time than that of the Na+ cation, and it is important that the Cs+ ion successfully lock the configurational chirality around the Yb3+ center of the complex species in solution. This is reasoned by the short Cs+center dot center dot center dot FC, Cs+center dot center dot center dot O-Yb and Cs+center dot center dot center dot Yb3+ interactions observed in the crystal structure of alpha-5 and further confirmed by the chiral self-assembly of 5 or 6 from [Yb(H2O)(d/l-hfc)(3)] induced by CsI in a CHCl3 solution

A Investigation of Hydrogen-storage Alloy as Catalytic Electrode for Hydrogenation of Nitrobenzene

贮氢合金用作硝基苯电解加氢的催化电极研究卢世刚，杨汉西，王长发（武汉大学化学系，武汉１３００７２）混合稀土贮氢合金是近年来发展起来的新型功能材料。在室温下它可以吸收比自身体积大几百倍的氢原子形成金属氢化物．这种金属氢化物可作为氢源提供高反应活性的氢原...Since hydrogen.storage alloy ean not only absorb hydrogen atoms to form highlyreactive metal hydride as hydrogen source by electrolysis but also possesses a certain catalytic activityfor hydrogenation,it is thus feasible to utilize the allov as a novel electrOde for electrolvtichydrogenation in organic electrored uction. This work employed misch metal AB_5 type alloy as acatalytic electrode and studied the electrochemical hydrogenation of nitrobenzene. The hydrogen-storage electrede(MH)was a plastic bonded electrede sheet made from a paste ofMm(NiCoMnAl)_5 alloy powder and teflon emulsion. The electrolysis was performed at constantcurrent and controlled potential in a three electrede cell of H-type configuration. The electrolyte was0.5 mol/L KOH aqueous solution and 0.5 mol/L KOH in CH_3OH+H_2O(80:20 by vol.). Changes in the concentrations of nitrobenzene(NB)and its reaction pred ucts were monitored bysampling at different d uration of electrolysis and then analysed by HPLC and UV spectroscopy. The CV cruve of a powder microelectrode of hydrogen-storage alloy in alkaline solution showed apair of distinct oxidation-reduction current peaks of hydride formation at E=-1.1V and hydrogendesorption at E=-0.9V.In addition of NB, a strong reduction peak appeared at E=-0.7 V oncathodic scan,and the anodic peak of hydride oxidation completely disappeared on reverse scan tosuggest the participation of absorbed hydrogen in the NB red uction(Fig.3). In the electrolysis of NB-saturated alkaline solution,we used UV spectroscopy monitoring the compositional changes of theelectrolvte. It was found that with increasing the electrolysis time the concentration of NB dropedsteadily and instead the concerntration of the main product aniline (AN)went up contineously as seenby the decreasing 278 nm and increasi ng 230nm UV peaks both characteristic of nitrobenzene andaniline. By HPLC seperation and analyse of the electrolyte after electrolysis,the electrolysis yield ofAN reached up to 90%and the current efficiency calculated also exceeded 85%. Except for a verysmall amount of azoxvbenzene and azobenzene(totally about 2%content)there were no any otherside reaction products or intermediates found in the course of electrolysis,indicating the high selectivityof MH electrede for nitrobenzene hydrogenation. In order to increase the dissolubility of NB in electrolyte,we tried to use the methanol-watermixed solvent instead of aqueous solvent for the electrolytic hydrogenation of NB. In the case of usingthe mixed solvent,the main electrolysis preduct was still AN,and the AN yield and current efficiencywere 86%and 85%both almost equal to the values measured in alkaline solution. Comparising of theMH electredes before and after electrolvsis there were no any discernible changes observed in thehydrogen-storage capacity and charge-discharge properties,suggesting a quite catalytic stability in theorganic media. In summay it could be concluded that the use of MH electrode in the electrochemicalhydrogenation of nitrobenzene offers a number of advantages of high selectivity,high currentefficiency and excellent catalytic stability,this shows a great promise for ind ustrial applications.作者联系地址：武汉大学化学系Author's Address: Department of Chemistry, Wuhan University, Wuhan 43007

Stereochemistry and solid-state circular dichroism spectroscopy of eight-coordinate chiral lanthanide complexes

Eight-coordinate chiral lanthanide complexes [Eu(dbM)(3)L-RR] (1), [Eu(dbM)(3)L-SS (2) and [Tb(dbm)(3)L-RR] (3) (L-RR/L-SS= (-)-/(+)-4,5-pineno-2,2'-bipyridine, Hdbm = dibenzoylmethane) were synthesized stereoselectively, which were characterized by UV-vis, CD spectra and X-ray single-crystal diffraction. The mirror-image structure features of complexes 1 and 2 were obtained by combination of the solid-state CD spectra and the crystal structure analysis. After further comparison with the solid-state CID spectra of six-coordinate and seven-coordinate metal complexes containing beta-diketone ligands, the CD spectra-absolute configuration correlation rule for the eight-coordinate beta-diketonate lanthanide complexes was proposed through the exciton chirality method for the first time. The Delta or Lambda absolute configurations of complexes 1 - 3 with the distorted square antiprism geometry were confirmed by the X-ray single-crystal analysis.National Natural Science Foundation of China [20773098, 20973136]; Innovation Foundation of Xiamen University (Series 2) [XDKJCX20061027