Anti-Markovnikov Hydroalkylation of Styrene Derivatives via Hydrazones Catalyzed by Ru-PNP Complex.

A well-defined Ru(II)-PNP complex demonstrated high activity in the anti-Markovnikov hydroalkylation of nonpolarized terminal alkenes via hydrazones. Hydrazone served as a carbanion equivalent to combine with the electrophilic alkene substrate upon activation by the ruthenium catalyst, forming a new C-C bond in a concerted pathway with N2 as the only theoretical byproduct. Experimental and computational studies suggested the existence of a push-pull interaction that activated the alkene for hydrazone addition and then deduced the mechanism.

Prediction of highly stable 2D carbon allotropes based on azulenoid kekulene.

Despite enormous interest in two-dimensional (2D) carbon allotropes, discovering stable 2D carbon structures with practically useful electronic properties presents a significant challenge. Computational modeling in this work shows that fusing azulene-derived macrocycles - azulenoid kekulenes (AK) - into graphene leads to the most stable 2D carbon allotropes reported to date, excluding graphene. Density functional theory predicts that placing the AK units in appropriate relative positions in the graphene lattice opens the 0.54 eV electronic bandgap and leads to the appearance of the remarkable 0.80 eV secondary gap between conduction bands - a feature that is rare in 2D carbon allotropes but is known to enhance light absorption and emission in 3D semiconductors. Among porous AK structures, one material stands out as a stable narrow-multigap (0.36 and 0.56 eV) semiconductor with light charge carriers (me = 0.17 m0, mh = 0.19 m0), whereas its boron nitride analog is a wide-multigap (1.51 and 0.82 eV) semiconductor with light carriers (me = 0.39 m0, mh = 0.32 m0). The multigap engineering strategy proposed here can be applied to other carbon nanostructures creating novel 2D materials for electronic and optoelectronic applications.

Giant hornet (Vespa soror) attacks trigger frenetic antipredator signalling in honeybee (Apis cerana) colonies.

Asian honeybees use an impressive array of strategies to protect nests from hornet attacks, although little is understood about how antipredator signals coordinate defences. We compared vibroacoustic signalling and defensive responses of Apis cerana colonies that were attacked by either the group-hunting giant hornet Vespa soror or the smaller, solitary-hunting hornet Vespa velutina. Apis cerana colonies produced hisses, brief stop signals and longer pipes under hornet-free conditions. However, hornet-attack stimuli-and V. soror workers in particular-triggered dramatic increases in signalling rates within colonies. Soundscapes were cacophonous when V. soror predators were directly outside of nests, in part because of frenetic production of antipredator pipes, a previously undescribed signal. Antipredator pipes share acoustic traits with alarm shrieks, fear screams and panic calls of primates, birds and meerkats. Workers making antipredator pipes exposed their Nasonov gland, suggesting the potential for multimodal alarm signalling that warns nestmates about the presence of dangerous hornets and assembles workers for defence. Concurrent observations of nest entrances showed an increase in worker activities that support effective defences against giant hornets. Apis cerana workers flexibly employ a diverse alarm repertoire in response to attack attributes, mirroring features of sophisticated alarm calling in socially complex vertebrates.

Sodium Binding Interactions with Aliphatic Amino Acids: A Guided Ion Beam and Computational Study.

Metal binding affinities play a vital role in medicinal, biological, and industrial applications. In particular, metal cation-amino acid (AA) interactions contribute to protein stability such that analyzing analogous prototypical interactions is important. Here, we present a full description of the interactions of sodium cations (Na+) and six aliphatic amino acids (AA), where AA = glycine (Gly), alanine (Ala), homoalanine (hAla), valine (Val), leucine (Leu), and isoleucine (Ile). Experimentally, these interactions are evaluated using threshold collision-induced dissociation carried out in a guided ion beam tandem mass spectrometer, allowing for the determination of the kinetic-energy-dependent behavior of Na+-AA dissociation. Analysis of these dissociation cross sections, after accounting for multiple ion-molecule collisions, internal energy of reactant ions, and unimolecular decay rates, allows the determination of absolute Na+-AA bond dissociation energies (BDEs) in kJ/mol of Gly (164.0), Ala (166.9), hAla (167.9), Val (172.7), Leu (173.7), and Ile (174.6). These are favorably compared to quantum chemical calculations conducted at the B3LYP, B3P86, MP2(full), B3LYP-GD3BJ, and M06-2X levels of theory. Our combination of structural and energetic analyses provides information regarding the specific factors responsible for Na+ interactions with amino acids. Specifically, we find that the BDEs increase linearly with increasing polarizability of the amino acid.

Honey bees (Apis cerana) use animal feces as a tool to defend colonies against group attack by giant hornets (Vespa soror).

Honey bees (genus Apis) are well known for the impressive suite of nest defenses they have evolved to protect their abundant stockpiles of food and the large colonies they sustain. In Asia, honey bees have evolved under tremendous predatory pressure from social wasps in the genus Vespa, the most formidable of which are the giant hornets that attack colonies in groups, kill adult defenders, and prey on brood. We document for the first time an extraordinary collective defense used by Apis cerana against the giant hornet Vespa soror. In response to attack by V. soror, A. cerana workers foraged for and applied spots of animal feces around their nest entrances. Fecal spotting increased after colonies were exposed either to naturally occurring attacks or to chemicals that scout hornets use to target colonies for mass attack. Spotting continued for days after attacks ceased and occurred in response to V. soror, which frequently landed at and chewed on entrances to breach nests, but not Vespa velutina, a smaller hornet that rarely landed at entrances. Moderate to heavy fecal spotting suppressed attempts by V. soror to penetrate nests by lowering the incidence of multiple-hornet attacks and substantially reducing the likelihood of them approaching and chewing on entrances. We argue that A. cerana forages for animal feces because it has properties that repel this deadly predator from nest entrances, providing the first report of tool use by honey bees and the first evidence that they forage for solids that are not derived from plants. Our study describes a remarkable weapon in the already sophisticated portfolio of defenses that honey bees have evolved in response to the predatory threats they face. It also highlights the strong selective pressure honey bees will encounter if giant hornets, recently detected in western North America, become established.

Light-enabled metal-free pinacol coupling by hydrazine.

Efficient carbon-carbon bond formation is of great importance in modern organic synthetic chemistry. The pinacol coupling discovered over a century ago is still one of the most efficient coupling reactions to build the C-C bond in one step. However, traditional pinacol coupling often requires over-stoichiometric amounts of active metals as reductants, causing long-lasting metal waste issues and sustainability concerns. A great scientific challenge is to design a metal-free approach to the pinacol coupling reaction. Herein, we describe a light-driven pinacol coupling protocol without use of any metals, but with N2H4, used as a clean non-metallic hydrogen-atom-transfer (HAT) reductant. In this transformation, only traceless non-toxic N2 and H2 gases were produced as by-products with a relatively broad aromatic ketone scope and good functional group tolerance. A combined experimental and computational investigation of the mechanism suggests that this novel pinacol coupling reaction proceeds via a HAT process between photo-excited ketone and N2H4, instead of the common single-electron-transfer (SET) process for metal reductants.