Chirality–helicity of cumulenes: A non‐scalar charge density derived perspective

Abstract

We investigate the presence of helical character and chirality using a vector‐based charge density perspective instead of energetic or structural measures. The vector‐based perspective of the chemical bonding, constructed using the most preferred direction of charge density accumulation, finds the presence of induced symmetry‐breaking for α,ω‐disubstituted [4]cumulenes as the end groups are torsioned. The stress tensor trajectories Tσ(s) are used to provide the additional symmetry‐breaking required to quantify the degree and nature of the chirality and helical character. The S‐1,5‐dimethyl‐[4]cumulene contains a very low degree of chiral character but significant axiality(helicity) resulting in a weakly helical morphology of the corresponding Tσ(s). The (‐)S(‐), (+)S(‐) and (+)S(+) conformations of S‐1,5‐diamino‐[4]cumulene contain very significant degrees of both chirality and helical character resulting in helical morphology of the corresponding Tσ(s). We discuss the consequences for the Tσ(s) in locating chiral character in these molecules in future experiment investigations.

Scoring molecular wires subject to an ultrafast laser pulse for molecular electronic devices

“…3 In particular properties of conjugated carbon C C "linkages," as wires between building blocks, have prompted a huge and diverse body of research in polyenes, cumulenes, and related molecular motifs. [4][5][6][7][8][9][10] Ethene in particular has attracted a substantial body of both theoretical and experimental research investigations [11][12][13][14][15][16][17][18][19][20][21][22][23][24] focusing on excited state photodynamics, as it is the repeating unit of the simplest polyene and the smallest organic molecule that comprises a π orbital.…”

Tools for overcoming reliance on energy-based measures in chemistry: a tutorial review

“…50 This is consistent with theoretical investigations 53 discovering the interdependence of steric-electronic factors to be more complex than is discernable from molecular structures alone, for example, the helical electronic transitions of spiroconjugated (cumulene) molecules. 54,55 4.2.2 Hidden chiral character and steric effects. Formally achiral ethane comprises three symmetry inequivalent contributions: a pair of R s and S s stereoisomers along with Q s , which was newly discovered using second generation directed T s (s) 28 trajectories, see Section 3.3.2 and the ESI † Materials S4.…”

“…50 This is consistent with theoretical investigations 53 discovering the interdependence of steric-electronic factors to be more complex than is discernable from molecular structures alone, for example, the helical electronic transitions of spiroconjugated (cumulene) molecules. 54,55…”

Response of the mechanical and chiral character of ethane to ultra‐fast laser pulses

“…Recently, the interdependence of steric‐electronic factors was discovered to be more complex 1 than was discernable from the molecular structures for the helical electronic transitions of spiroconjugated molecules 2,3 …”

“…From the theoretical standpoint, ethane was recently used to establish the next generation QTAIM (NG‐QTAIM) interpretation of an achiral molecule 11 . In this earlier investigation we demonstrated that NG‐QTAIM can be used to understand the staggered conformation of ethane using second‐generation eigenvector trajectories 3 . We have also considered doubly halogen substituted ethane molecules and quantified their chiral character within the NG‐QTAIM formalism 12 …”