The compounds Ni,(form), (1) and Pdz(form), (2), where form = (p-CH3C6H4)NCHN(p-CH3c6H4)-, have been prepared and characterized by several physical methods, including X-ray crystallography. Both 1 and 2 form cubic crystals from CHzClz/hexane in the presence of moist air, with the composition M,(form),.2H20. The space group is Pn% and the unit cell edges are 20.841 ( 5 ) A for 1 at 20 "C, 20.649 (2) A for 1 at -105 "C, and 21.067 (4) A for 2 at 25 "C. With 6 molecules in the unit cell, crystallographic symmetry 42 (D4) is imposed. The principal dimensions of 1 (at 20 "C) and 2, respectively, are as follows: torsion angles, 16.85", 15.03"; M-M distances, 2.485 (2), 2.622 (3) A; mean M-N distances, 1.904 (9, 2.063 (14) A. The palladium compound was also crystallized as Pd2 (form),.(C2H5),0 and its structure determined: space group P4/ncc with a = 16.416 (2) A, c = 23.827 (4) A, and 2 = 4. Refinement was not entirely successful because of disorder but the dimensions of the complex agreed well with those found in the H,O-containing cubic crystals. Cyclic voltammetry showed that both compounds can be reversibly oxidized to the +1 state with Ellz values (vs Ag/AgCl) of +0.73 V for Ni and 0.81 V for Pd. For the palladium compound a second reversible oxidation was seen at +1.19 V but a second oxidation at ca. +1.25 V for the Ni compound was irreversible. Chemical oxidations to the [M,(form),]+ ions with [Ag(C-H3CN),]BF4 and AgPF6 allowed the isolation of the crystalline products [Ni,(f~rm)~]BF, (3) and [Pd(form),]PF6 (4), whose structures were determined; for 3, space group P4/n with a = 14.078 (3) A, c = 13.379 (4) A, and Z = 2; for 4, space group P4/ncc with a = 13.871 ( 5 ) A, c = 29.180 (6) A, and 2 = 4. The [Ni2(form),]+ ion has an appreciably shorter Ni-Ni bond length, 2.418 (4) A, than the neutral molecule and a much greater torsion angle, 27.4". The [Pd,(form),]+ ion has a slightly longer Pd-Pd bond, 2.637 (6) A, and slightly greater torsion angle, 17", than the neutral molecule. SCF-Xa-SW calculations (1) (a) Cotton, F. A.; Walton, R.

Currently, high-energy rechargeable batteries are being intensively pursued to meet the increasing energy requirements of our modern life and industrial society. Alkali metals are considered some of the most promising anodes for nextgeneration high-energy batteries because of their superior theoretical specific capacities and low reduction potentials. Here, we provide an overview of the recent development of alkali metal anodes. First, we highlight that their high reactivity, unstable solid electrolyte interphase, dendrite formation, and huge volume change bring great challenges for the safety and lifespan of alkalimetal-based batteries. Then, we summarize various advanced strategiesincluding the micro-and/or nanostructuring of alkali metals, introduction of stable hosts, structural modification of current collectors, construction of artificial anode-electrolyte interfaces, separator modification, and electrolyte optimization-to address these challenges. Lastly, we present the remaining challenges and possible research directions for further developments.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Recent research has shown that the corrosivity of naphthenic acids is related to their molecular mass and that the "total acid number" (TAN), traditionally used as an indicator of the naphthenic acid content of an oil, is not as reliable as first believed. The presence of naphthenic acids in crude oils leads to the corrosion of oil refinery equipment, with the oil industry incurring costs that will ultimately be passed on to the consumer. With regard to these concerns, mass spectrometry has been increasingly applied to the investigation of the naphthenic acid content of crude oils. To ascertain the nature of the species present, however, it is necessary to utilize an ionization technique that does not result in fragmentation, ensuring the detection only of molecular species which provide useful information about the sample constitution. In the following investigation, negative ion mode nanospray Fourier transform ion cyclotron resonance (FTICR) mass spectrometry has been applied to the analysis of crude oil samples, providing insight into the different acidic species that were present. Use of the negative ion mode to allow the selective observation of the naphthenic acids and the inherent high mass accuracy and ultrahigh resolution of FTICR mass spectrometry ensure that this technique is very well suited to the characterization of naphthenic acids within a crude oil sample. Determination of the nature of the naphthenic acids present provides vital information, such as the acids' sizes and composition, which may be used in the battle against corrosion and also used to fingerprint samples from different oil fields.

Fluorescent bisretinoids, such as A2E and all-trans-retinal dimer, form as a by-product of vitamin A cycling in retina and accumulate in retinal pigment epithelial (RPE) cells as lipofuscin pigments. These pigments are implicated in pathological mechanisms involved in several vision-threatening diseases including age-related macular degeneration. Efforts to understand damaging events initiated by these bisretinoids have revealed that photoexcitation of A2E by wavelengths in the visible spectrum leads to singlet oxygen production and photooxidation of A2E. Here we have employed liquid chromatography coupled to electrospray ionization mass spectrometry together with tandem mass spectrometry (MS/MS), to demonstrate that A2E also undergoes photooxidation-induced degradation and we have elucidated the structures of some of the aldehyde-bearing cleavage products. Studies in which A2E was incubated with a singlet oxygen generator yielded results consistent with a mechanism involving bisretinoid photocleavage at sites of singlet molecular oxygen addition. We provide evidence that one of the products released by A2E photodegradation is methylglyoxal, a low molecular weight reactive dicarbonyl with the capacity to form advanced glycation end products. Methylglyoxal is already known to be generated by carbohydrate and lipid oxidation; this is the first report of its production via bisretinoid photocleavage. It is significant that AGE-modified proteins are detected in deposits (drusen) that accumulate below RPE cells in vivo; drusen have been linked to age-related macular degeneration pathogenesis. Whereas various processes play a role in drusen formation, these findings are indicative of a contribution from lipofuscin photooxidation in RPE.advanced glycation end products | lipofuscin | photofragmentation | photooxidation | retinal pigment epithelial cells F luorescent bisretinoid pigments are amassed as lipofuscin in retinal pigment epithelial (RPE) cells in association with aging although individuals vary with respect to the extent of accumulation (1). The excessive deposition of these compounds in RPE cells is also considered to lead to retinal degeneration in early onset blinding disorders associated with mutations in the genes encoding ABCA4 (ATP-binding cassette subfamily A member 4) (2, 3), ELOVL4 (4), and BEST-1 (5). Moreover, the deposition of these pigments likely also contributes to the etiology of agerelated macular degeneration (AMD) (6, 7). Whereas these bisretinoids constitute a complex mixture, all appear to originate from reactions of all-trans-retinal and some have been identified, including A2E (Fig. 1) and its isomers (8); A2-dihydropyridinephosphatidylethanolamine (A2-DHP-PE) and A2-dihydropyridine-ethanolamine (A2-DHP-E) (9); and all-trans-retinal dimer, all-trans-retinal dimer-phosphatidylethanolamine (all-transretinal dimer-PE), and all-trans-retinal dimer-ethanolamine (alltrans-retinal dimer-E) (10, 11). Structural features common to all of these pigments are the alternating single and double carbon...

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Density functional theory (DFT) calculations have been carried out on a number of compounds in which multiple bonds are formed by or between main group elements. The calculated and observed structures agree very well for P2, P4, P⋮C−R, R−PP−R, As⋮C−R, R−AsAs−R‘, R−BiBi−R, and R2−GeGe−R2. For a recently reported compound alleged to contain a Ga⋮Ga (triple) bond the calculations point to a different formulation in which there is only a double bond and a significant role for noncovalent interactions.

The structure of a new dibenzodiazepine alkaloid, diazepinomicin (1), isolated from the culture of a marine actinomycete of the genus Micromonospora was characterized using spectroscopic methods. Diazepinomicin represents a unique molecular class composed of a dibenzodiazepine core linked to a farnesyl side chain.