Na-ion batteries are emerging as one of the most promising energy storage technologies, particularly for grid-level applications. Among anode candidate materials, hard carbon is very attractive due to its high capacity and low cost. However, hard carbon anodes often suffer a low first-cycle Coulombic efficiency and fast capacity fading. In this study, we discover that doping graphene oxide into sucrose, the precursor for hard carbon, can effectively reduce the specific surface area of hard carbon to as low as 5.4 m(2)/g. We further reveal that such doping can effectively prevent foaming during caramelization of sucrose and extend the pyrolysis burnoff of sucrose caramel over a wider temperature range. The obtained low-surface-area hard carbon greatly improves the first-cycle Coulombic efficiency from 74% to 83% and delivers a very stable cyclic life with 95% of capacity retention after 200 cycles.

We report that crystalline 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), an organic solid, is highly amenable to host divalent metal ions, i.e., Mg and Ca, in aqueous electrolytes, where the van der Waals structure is intrinsically superior in hosting charge-dense ions. We observe that the divalent nature of Mg causes unique squeezing deformation of the electrode structure, where it contracts and expands in different crystallographic directions when hosting the inserted Mg-ions. This phenomenon is revealed experimentally by ex situ X-ray diffraction and transmission electron microscopy, and is investigated theoretically by first-principles calculations. Interestingly, hosting one Mg ion requires the coordination from three PTCDA molecules in adjacent columns of stacked molecules, which rotates the columns, thus reducing the (011) spacing but increasing the (021) spacing. We demonstrate that a PTCDA Mg-ion electrode delivers a reversible capacity of 125 mA h g, which may include a minor contribution of hydronium storage, a good rate capability by retaining 75 mA h g at 500 mA g (or 3.7 C), and a stable cycle life. We also report Ca storage in PTCDA, where a reversible capacity of over 80 mA h g is delivered.

We have demonstrated, for the first time, a polycyclic aromatic hydrocarbon (PAH), crystalline and readily available coronene, exhibits highly reversible anion-storage properties. Conventional graphite anion-insertion electrodes operate at potentials >4.5 V vs Li + /Li, requiring electrolyte additives or the use of ionic liquids as electrolytes. The coronene electrode shows flat plateaus at 4.2 V (charge) and 4.0 V (discharge) in a standard alkyl carbonate electrolyte and delivers a reversible discharge capacity of ∼40 mA h g −1 . Ex situ characterization reveals that coronene retains its crystalline structure and chemical bonding upon initial PF 6 − incorporation. Coronene−PF 6 electrodes show impressive cycling stability: 92% capacity retention after 960 cycles. The discovery of the reversible anion-storage properties of coronene may open new avenues toward dualion batteries based on PAHs as electrodes.

The heterogeneous reactions of benzo[a]pyrene-d12 (BaP-d12), benzo[k]fluoranthene-d12 (BkF-d12), benzo[ghi]perylene-d12 (BghiP-d12), dibenzo[a,i]pyrene-d14 (DaiP-d14), and dibenzo[a,l]pyrene (DalP) with NO2, NO3/N2O5, and OH radicals were investigated at room temperature and atmospheric pressure in an indoor Teflon chamber and novel mono NO2-DaiP, and mono NO2-DalP products were identified. Quartz fiber filters (QFF) were used as a reaction surface and the filter extracts were analyzed by GC/MS for nitrated-PAHs (NPAHs) and tested in the Salmonella mutagenicity assay, using Salmonella typhimurium strain TA98 (with and without metabolic activation). In parallel to the laboratory experiments, a theoretical study was conducted to rationalize the formation of NPAH isomers based on the thermodynamic stability of OH-PAH intermediates, formed from OH-radical-initiated reactions. NO2 and NO3/N2O5 were effective oxidizing agents in transforming PAHs to NPAHs, with BaP-d12 being the most readily nitrated. Reaction of BaP-d12, BkF-d12 and BghiP-d12 with NO2 and NO3/N2O5 resulted in the formation of more than one mono-nitro isomer product, while the reaction of DaiP-d14 and DalP resulted in the formation of only one mono-nitro isomer product. The direct-acting mutagenicity increased the most after NO3/N2O5 exposure, particularly for BkF-d12 in which di-NO2-BkF-d10 isomers were measured. The deuterium isotope effect study suggested that substitution of deuterium for hydrogen lowered both the direct and indirect acting mutagenicity of NPAHs and may result in an underestimation of the mutagencity of the novel NPAHs identified in this study.

The lycopodium family of alkaloids has garnered considerable attention over the years because of their wide-ranging biological activity and structural complexity. 1 The parent member of this family, lycopodine (1), was isolated 125 years ago by Bödeker (Figure 1). 2 Beneficial medicinal properties, such as antipyretic 3 and anticholinesterase activity, 4 have been attributed to lycopodine and other lycopodium alkaloids. To date, seven racemic total syntheses and two racemic formal syntheses of 1 have been reported. 5 Herein, we report the first enantioselective total synthesis of 1. Our retrosynthetic strategy is shown in Figure 1. Key to this strategy is the diastereoselective intramolecular Michael addition of 4 and the Heathcock-inspired 5d Mannich cyclization to form tricycle 2.The synthesis commenced with the known ester 6, 6 which is readily accessible in two steps from commercially available acyl sultam 5 (Scheme 1). Next, one-pot treatment of commercially available 1,4-dibromobutane (7) with NaSO 2 Ph in DMF followed by NaN 3 and H 2 O generated the sulfone 8 in reasonable yield. Double deprotonation of 8 with lithium tetramethylpiperidide (LiTMP) followed by addition of the chiral ester 6 yielded keto sulfone 9 in 74% yield. It should be noted that use of lithium diisopropylamide or n-BuLi resulted in a significant reduction in the yield of this transformation. We have previously observed the superior performance of LiTMP during our synthetic efforts toward the bisspiroketal azaspiracid-1. 7 Next, we turned our attention to the cross metathesis of 9 and 3-penten-2-one (10). The presence of the azide moiety as well as an internal nucleophile (the C 8 keto sulfone moiety) and Michael acceptor (the C 5 -C 7 enone) within product 4 imparted unique challenges for the cross metathesis. We were gratified to find that use of the highly active secondgeneration Grubbs-Hoveyda (GH-II) catalyst 8 did generate the desired product 4 in good yield (63%, 88% on the basis of recovered starting material). Also key to this metathesis was the specific choice of the enone 10. 9 Replacement of 10 with methyl vinyl ketone led to a significant reduction in the efficiency of the transformation.Our attention then turned to the key intramolecular Michael addition of keto sulfone 4 (Scheme 2). We had initially hypothesized that the C 15 stereogenic center would disrupt the desired stereochemical outcome at the C 7 and C 8 positions by placing the larger phenyl sulfone and methyl ketone in pseudoequatorial positions in the transition state 11 shown. Consequently, our strategy had intended to explore a suitable organocatalyst for facilitating this reaction while overriding what we perceived to be the favored pathway. Prior to embarking on this investigation, we felt it would be prudent to confirm the inherent stereochemical preference in the system. Treatment of keto sulfone 4 with i-Pr 2 NH in a mixed-solvent system (4:1 i-PrOH/ dichloromethane) at room temperature led to clean conversion to a single product that crystallized out o...