An aqueous rechargeable Zn//Co3 O4 battery is demonstrated with Zn@carbon fibers and Co3 O4 @Ni foam as the negative and positive electrodes, respectively, using an electrolyte of 1 m KOH and 10 × 10(-3) m Zn(Ac)2 . It can operate at a cell voltage as high as 1.78 V with an energy density of 241 W h kg(-1) and presents excellent cycling. The battery is also assembled into a flexible shape, which can be applied in flexible or wearable devices requiring high energy.

Aluminum switches: The addition of AlMe3 to the isoprene polymerization catalyst 1/[Ph3C][B(C6F5)4] switches the regio‐ and stereoselectivity from 3,4‐isospecific to 1,4‐cis selective (see scheme). A heterotrinuclear Y/Al complex obtained from the reaction of 1 with AlMe3 shows 1,4‐cis selectivity under similar conditions in the presence of [Ph3C][B(C6F5)4]. PI=polyisoprene.

The creation of new polymer materials with well-controlled microstructures and desired properties relies on the development of new generations of polymerization catalysts. cis-1,4-Regulated polyisoprene (PIP) and polybutadiene (PBD) are among the most important elastomers used for tires and other elastic materials. As the demand for high-performance synthetic rubbers has increased, the development of highquality elastomers by polymerization of isoprene and butadiene has grown in importance. In addition, the limited supply of natural rubber has promoted the need for improved synthetic polyisoprene. [1] To date a variety of catalyst systems have been reported for the polymerization of butadiene and isoprene, among which catalysts based on rare-earth metals have attracted special attention because of their high activity and high cis-1,4 selectivity.[2] The catalysts utilized industrially for the cis-1,4 polymerization of butadiene and isoprene are heterogeneous Ziegler-Natta-type multicomponent systems that consist typically of a rare-earth metal (e.g., Nd) carboxylate, ethylaluminum chloride, and isobutylaluminum hydride. [2a-c] To mimic and improve the industry catalyst systems, and to gain a better understanding of the mechanistic aspects of these heterogeneous catalysts, various discrete rare-earth metal carboxylate and alkoxide complexes as well as rareearth metal/aluminum heterometallic alkyl complexes have been investigated.[3] Some of these molecular systems show very high cis-1,4 selectivity (up to 99 %) when combined with a chloride additive, such as Et 2 AlCl. However, similar to the heterogeneous industrial catalysts, such binary or ternary catalyst systems generally lack "livingness" and yield polymers with rather broad molecular-weight distributions. On the other hand, lanthanide metallocene-based catalyst sys- [4b] have been found to afford polymers with both high cis-1,4 selectivity (up to 99 %) and a narrow molecularweight distribution, or "livingness" (M w /M n = 1.20-1.23), in the polymerization of butadiene under appropriate conditions, [4] however, the polymerization of isoprene has not been achieved in a "living" fashion with such catalyst systems.[4f]Very recently, the combination of a Nd/Mg heterotrimetallic allyl complex with methylaluminoxane (MAO) was reported to show both high cis-1,4 selectivity (95-99 %) and a relatively narrow molecular-weight distribution (M w /M n = 1.3-1.7) for the polymerization of isoprene. [5,6] A common feature in the reported catalyst systems is that they all require an aluminum additive, such as AlR 2 Cl, AlR 3 , or MAO, to show high activity and high cis-1,4 selectivity, which makes it difficult to identify the true catalytic species and to understand the mechanistic aspects of the polymerization process. [2][3][4][5][6][7][8] Recently, cationic methylyttrium species, such as [YMe 2Àn (solv) x ] n+1 (n = 0, 1; solv = solvent), have been reported to show activity for the polymerization of butadiene and isoprene in the absence of an aluminum additive, but ...

Many peroxy-containing secondary metabolites1,2 have been isolated and shown to provide beneficial effects to human health3–5. Yet, the mechanisms of most endoperoxide biosyntheses are not well understood. Although endoperoxides have been suggested as key reaction intermediates in several cases6–8, the only well-characterized endoperoxide biosynthetic enzyme is prostaglandin H synthase, a haem-containing enzyme9. Fumitremorgin B endoperoxidase (FtmOx1) from Aspergillus fumigatus is the first reported α-ketoglutarate-dependent mononuclear non-haem iron enzyme that can catalyse an endoperoxide formation reaction10–12. To elucidate the mechanistic details for this unique chemical transformation, we report the X-ray crystal structures of FtmOx1 and the binary complexes it forms with either the co-substrate (α-ketoglutarate) or the substrate (fumitremorgin B). Uniquely, after α-ketoglutarate binding to the mononuclear iron centre in a bidentate fashion, the remaining open site for oxygen binding and activation is shielded from the substrate or the solvent by a tyrosine residue (Y224). Upon replacing Y224 with alanine or phenylalanine, the FtmOx1 catalysis diverts from endoperoxide formation to the more commonly observed hydroxylation. Subsequent characterizations by a combination of stopped-flow optical absorption spectroscopy and freeze-quench electron paramagnetic resonance spectroscopy support the presence of transient radical species in FtmOx1 catalysis. Our results help to unravel the novel mechanism for this endoperoxide formation reaction.