The electronic spin filtering capability of a single chiral helical peptide is measured. A ferromagnetic electrode source is employed to inject spin-polarized electrons in an asymmetric single-molecule junction bridging an α-helical peptide sequence of known chirality. The conductance comparison between both isomers allows the direct determination of the polarization power of an individual chiral molecule.

The cationic, neutral, and anionic charge states of the B13 cluster are examined through the use of density functional theory. Several different isomers are studied and compared with a special emphasis given to the electronic structure of the lowest lying isomers. Included among the isomers are three which have been proposed earlier and a pair of new ones. While no minima that corresponded to a filled icosahedron could be found for the cluster, an intriguing atom-in-a-cage structure was found that is a local minimum on the cationic, neutral, and anionic surfaces. The structure found for the anionic cluster has D 3 h symmetry, and the 12 external boron atoms are arranged as three six-membered rings back-to-back. The planar and quasi-planar structures are seen to be more stable than three-dimensional isomers, but the ordering by stability of the planar and quasi-planar structures changes depending on the charge. Relative energies, selected geometric features, ionization potentials, and electron affinities are reported for these structures and some justification for the differences seen among the isomers is given. The planar structures benefit from π delocalization. In the case of the global minimum of the B13 + cationic cluster this delocalization is reminiscent of aromaticity.

There is increasing interest in the study of chiral degrees of freedom occurring in matter and in electromagnetic fields. Opportunities in quantum sciences will likely exploit two main areas that are the focus of this Review: (1) recent observations of the chiral-induced spin selectivity (CISS) effect in chiral molecules and engineered nanomaterials and (2) rapidly evolving nanophotonic strategies designed to amplify chiral light–matter interactions. On the one hand, the CISS effect underpins the observation that charge transport through nanoscopic chiral structures favors a particular electronic spin orientation, resulting in large room-temperature spin polarizations. Observations of the CISS effect suggest opportunities for spin control and for the design and fabrication of room-temperature quantum devices from the bottom up, with atomic-scale precision and molecular modularity. On the other hand, chiral–optical effects that depend on both spin- and orbital-angular momentum of photons could offer key advantages in all-optical and quantum information technologies. In particular, amplification of these chiral light–matter interactions using rationally designed plasmonic and dielectric nanomaterials provide approaches to manipulate light intensity, polarization, and phase in confined nanoscale geometries. Any technology that relies on optimal charge transport, or optical control and readout, including quantum devices for logic, sensing, and storage, may benefit from chiral quantum properties. These properties can be theoretically and experimentally investigated from a quantum information perspective, which has not yet been fully developed. There are uncharted implications for the quantum sciences once chiral couplings can be engineered to control the storage, transduction, and manipulation of quantum information. This forward-looking Review provides a survey of the experimental and theoretical fundamentals of chiral-influenced quantum effects and presents a vision for their possible future roles in enabling room-temperature quantum technologies.

The study of the reaction of water with the first-row transition-metal ions is continued in this work. Here we report the study of the reaction of water with the middle (Cr+, Mn+, and Fe+) first-row transition-metal cations in both high- and low-spin states. In agreement with experimental observations, the oxides are predicted to be more reactive than the metal ions, and no exothermic products are observed. Formation of endothermic products is examined. An in-depth analysis of the reaction paths leading to the observed products is given, including various minima, and several important transition states. All results have been compared with existing experimental and theoretical data, and our earlier works covering the (Sc+, Ti+, V+) + H2O reactions to observe existent trends for the early first-row transition-metal ions. The MO+ + H2 energy relative to M+ + H2O increases through the series from left to right. Additionally, the Fe+ case is seen to be significantly different from the entire Sc+−Mn+ series because both its low- and high-spin cases involve paired electrons, and Mn+ shows some differences because of the complete half-filling of its valence shell in the high-spin case.

Quantum chemical calculations using density functional theory and correlated ab initio methods of the 10 π‐electron systems (N6H6)2+ and C2N4H6 show that the planar forms are no minima on the potential energy surfaces. The twisted ring structures of the two species are energy minima, but acyclic isomers are much lower in energy. The planar geometries sustain strong diamagnetic ring current comparable with that of benzene. In contrast, the calculated multicenter normalized Giambiagi electron delocalization index ING suggests that π‐delocalization in planar (N6H6)2+ and C2N4H6 is much weaker than in benzene. Since aromaticity is synonymous for a particular stability of cyclic delocalized systems, it may be stated that calculation or measurement of magnetic chemical shifts due to induced ring currents is not a reliable method to ascertain the aromatic character of a molecule. Aromatic compounds exhibit ring current induced magnetic shielding, but the reverse conclusion that ring current induced magnetic shielding identifies aromaticity is not justified. Furthermore, the 4n+2 rule as indicator of aromatic stabilization should only be used in conjunction with the ring size; the nature of the occupied π orbitals must always be examined.