Dynamic Evolving Exothermicity Steers Ultrafast Formation of a Correlated Triplet Pair State

Singlet fission (SF) presents an attractive solution to overcome the Shockley–Queisser limit of single-junction solar cells. The conversion from an initial singlet state to final triplet is mediated by the correlated triplet pair state 1(T1T1). Despite significant advancement on 1(T1T1) properties and its role in SF, a comprehensive understanding of the energetic landscape during SF is still unclear.

The application of aromaticity and antiaromaticity to reaction mechanisms

Aromaticity, in general, can promote a given reaction by stabilizing a transition state or a product via a mobility of π electrons in a cyclic structure. Similarly, such a promotion could be also achieved by destabilizing an antiaromatic reactant. However, both aromaticity and transition states cannot be directly measured in experiment. Thus, computational chemistry has been becoming a key tool to understand the aromaticity-driven reaction mechanisms.

Aromaticity Concerto in Polycyclic Conjugated Hydrocarbons: Fusion Pattern on Combined Aromaticity Strategy Leads to Distinctive Excited State Photophysics of Dinaphthopentalenes

Understanding the structure–property relationships in polycyclic conjugated hydrocarbons (PCHs) is crucial for controlling their electronic properties and developing new optical function materials. Aromaticity is a fundamentally important and intriguing property of numerous organic chemical structures and has stimulated a myriad of experimental and theoretical investigations. Exploiting aromaticity rules for the rational design of optoelectronic materials with the desired photophysical characteristics is a challenging yet fascinating task.

Direct Conversion of N2 and O2 to Nitric Oxide at Room Temperature Initiated by Double Aromaticity in the Y2BO+ Cation

The conversion of dinitrogen to more useful and reactive molecules has been the focus of intense research by chemists. In contrast to reductive N2 fixation, direct oxidation of N2 by O2 to nitric oxide under mild conditions via a thermochemical process is extremely challenging. Herein, we report the first example of N2 and O2 activation and coupling under thermochemical conditions through the remarkable ability of Y2BO+ to react with one N2 and two O2 molecules.

Stabilizing a 20-Electron Metallaazulyne by Aromaticity

The 18-electron rule states that metal complexes with 18 valence electron metal centers are thermodynamically stable because nine valence orbitals of transition metals including one s orbital, three p orbitals, and five d orbitals can collectively accommodate 18 electrons, achieving the same electron configuration as the noble gas in the period. Thus, 20-electron compounds are extremely rare due to a violation of such a rule.

Phosphine-Stabilized Germylidenylpnictinidenes as Synthetic Equivalents of Heavier Nitrile and Isocyanide in Cycloaddition Reactions with Alkynes

The reactions of chlorogermylene MsFluindtBu-GeCl 1, supported by a sterically encumbered hydrindacene ligand MsFluindtBu, with NaPCO(dioxane)2.5 and NaAsCO(18-c-6) in the presence of trimethylphosphine afforded trimethylphosphine-stabilized germylidenyl-phosphinidene 2 and -arsinidene 3, respectively. Structural and computational investigations reveal that the Ge–E′ bond (E′ = P and As) features a multiple-bond character.

Probing the Origin of Ambiphilic Reactivity in Osmapentalyne Complexes: Interplay of Ring Strain, Aromaticity, and Phosphonium Substituent

Ambiphilic reactivity is a fascinating topic in chemical reactions, attracting considerable interest because ambiphilic reagents can display properties of both nucleophilicity and electrophilicity. However, most of the previous attention has been focused on the characterization of the ambiphilic reactivity, whereas the origin is less understood. Here we carry out thorough density functional theory (DFT) calculations to probe the origin of the ambiphilic reactivity of the carbyne atom in osmapentalynes, observed previously in experiment.

Isolation of a carbon nanohoop with Möbius topology

Carbon nanohoop, a class of constrained molecular architecture consisting of linked arene units, has attracted considerable interest from both experimental and theoretical chemists due to their synthetic challenge and aesthetic architectures. Another fascinating and synthetically challenging species, the Möbius-type molecule, has been attracting the scientific community with its elegant structure and aromaticity. Thus, combining two things together, synthesizing a carbon nanohoop with Möbius topology remains more challenging to date.

Probing the Tautomerization of Disilenes, Disilabenzenes with Their Isomeric Silylenes: Significant Substituent, Aromaticity and Base Effects

Disilene has attracted considerable interests due to the trans-bending geometry which is significantly different from the planar alkene. However, the equilibrium between disilene and isomeric silylsilylene has not been fully understood. Here, we report a density functional theory (DFT) study on this equilibrium. Calculations reveal significant effects of substituent, aromaticity and base. Specifically, the parent disilene is thermodynamically more stable than the isomeric silylene.

Open questions on aromaticity in organometallics

While sp2-hybridized carbon atoms in hydrocarbons typically contribute only one electron to their aromaticity, metals have more electrons from d or f orbitals available for participating in conjugation in organometallics, complicating the electron counting as well as analysis of their aromaticity. Here, the author comments on the challenges towards understanding aromaticity in organometallics and outlines several remaining questions that have yet to be answered.