Stable structures of nitrogen-rich sulfides: N3SN4 and S(N4)m (m=1–4)

Planar Inorganic Five-Membered Heterocycles with σ+π Dual Aromaticity in Both S0 and T1 States

Cyclic species being aromatic in both the lowest singlet and triplet electronic states (so-called adaptive aromaticity) are scarce. To date, the reported systems are mostly organometallic heterocycles with the aromaticities...

Neutral binary chalcogen-nitrogen and ternary S,N,P molecules: new structures, bonding insights and potential applications

Early theoretical and experimental investigations of inorganic sulfur-nitrogen compounds were dominated by (a) assessments of the purported aromatic character of cyclic, binary S,N molecules and ions, (b) the unpredictable reactions of the fascinating cage compound S4N4, and (c) the unique structure and properties of the conducting polymer (SN)x. In the last few years, in addition to unexpected developments in the chemistry of well-known sulfur nitrides, the emphasis of these studies has changed to include nitrogen-rich species formed under high pressures, as well as the selenium analogues of well-known S,N compounds. Novel applications have been established or predicted for many binary S/Se,N molecules, including their use for fingerprint detection, in optoelectronic devices, as high energy-density compounds or as hydrogen-storage materials. The purpose of this perspective is to evaluate critically these new aspects of the chemistry of neutral, binary chalcogen-nitrogen molecules and to suggest experimental approaches to the synthesis of target compounds. Recently identified ternary S,N,P compounds will also be considered in light of their isoelectronic relationship with binary S,N cations.

Stability and Electronic Properties of Nitrogen Nanoneedles and Nanotubes

The electronic structures and stability of nitrogen nanostructures, nanotubes, and fiberlike nanoneedles of various diameters, formed by units N2m (m = 2-6), were studied by quantum chemistry computational modeling methods. The geometrical structures with various cross-sections and terminal units, their energetic stability, and their rather peculiar electron density distributions were investigated. The tightest nitrogen nanoneedle (NNN) studied theoretically in this work is the structure (N4n with D2h symmetry, whereas the nitrogen nanotube (NNT) with the largest diameter discussed here is the structure (N12)n with D2 symmetry. These families of NNNs and NNTs can be considered as nanostructures not only for potential applications as devices in nanotechnology or as possible scaffold structures but also as ligands in synthetic chemistry and high-energy density materials (HEDMs). As a consequence of the lone-pair electrons present around the walls of these NNNs and NNTs, these nitrogen nanostructures and the nitrogen nano-bundles (NNB) formed by aligning and combining them using intermediate carbon atoms, can have highly variable electronic properties controlled by the changing charge environment. In particular, for extended systems based on the units studied here, the band gaps of each of these systems can be affected greatly by the local charge of the environment.

Predicted High-Energy Molecules: Helical All-Nitrogen and Helical Nitrogen-Rich Ring Clusters

Helical all-nitrogen and nitrogen-rich ring clusters, new types of potential high-energy molecules, were investigated in the computational study reported here. Stable helical all-nitrogen clusters N26 and N46 and nitrogen-rich helical structure N26H16 formed by fused six-membered rings were found and characterized as proper energy minima by having real frequencies for all eigenvectors of the Hessian matrix. Furthermore, the stability of [6] N-ring helix was studied by calculating the barrier of dissociation reaction. The potential of these type molecules as high-energy density materials was studied. For a better intuitive understanding of the unusual bonding patterns, the molecular isodensity contour (MIDCO) surfaces for [6] N-ring helix and [6] N-helicene were compared at some characteristic density threshold values of 0.20, 0.32, and 0.35 au. As indicated at these threshold values of the isodensity surfaces, the bonds of all-nitrogen clusters appear stronger than those of nitrogen-rich clusters. Apparently, the nitrogen-rich clusters are of higher energy than the all-nitrogen structures, especially if one takes into account the energy balance of bonds involving hydrogen.

A theoretical study of nitrogen-rich phosphorus nitrides P(Nn)m

Ab initio calculations predict that structures P(Nn)m (n = 3, 4; m = 1-4; with linear N3, tetrahedral N4, and square N4) correspond to local energy minima characterized by having real frequencies for all eigenvectors of the Hessian matrix. The central P atom often prefers having an odd number of bonds, although we also found some stable structures where P is evenly bonded. The special role of the phosphorus atom in the geometrical arrangements of the P(Nn)m systems was investigated. The low barriers of P(N4)m in the gas-phase decomposition reactions mean that these nitrogen-rich systems require external stabilization if they are to be used as high-energy density materials or starting materials for further syntheses.