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

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 alpha,omega-disubstituted [4]cumulenes as the end groups are torsioned. The stress tensor trajectories T sigma(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 T sigma(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 T sigma(s). We discuss the consequences for the T sigma(s) in locating chiral character in these molecules in future experiment investigations.