Geometrical, electrical, and energetic parameters of hetero-disubstituted cumulenes and polyynes in the presence and absence of the external electric field

Abstract

Cumulenes and polyynes have the potential to be applied as linear, sp-hybridized, one-dimensional all-carbon nanowires in molecular electronics and optoelectronics. The delocalization and conductivity descriptors of the two π-conjugated systems, heterodisubstituted with the NO2, CN, NH2, and OH groups, were studied using the B3LYP, B3LYP/D3, CAM-B3LYP, and ωB97XD DFT functionals, combined with the aug-cc-pVTZ basis set. Three independent types of molecular descriptors, based on geometry (the HOMA index), electrical properties (trace of the polarizability tensor), and energetic (the HOMO-LUMO energy gap) were shown to be mutually correlated and provided concordant indication that communication through the cumulene chain was considerably better than through the polyyne one. The communication can be tuned by using substituents of significantly different π-electron donor-acceptor properties as well as by the external electric field directed along the carbon chain.

Substituent Effects from the Point of View of Energetics and Molecular Geometry in Acene, Polyene, and Polyyne Derivatives

“…Moreover, through-bond and through-space contributions to the SE were evaluated using models in which polyene linkers were removed. Further study by Sadlej-Sosnowska concerned the geometry, HOMO–LUMO gap, and polarizability in disubstituted polyynes and cumulenes . The main conclusion was that some combinations of X and Y groups cause higher changes in polarizability and the HOMO–LUMO gap than others.…”

“…Further study by Sadlej-Sosnowska concerned the geometry, HOMO–LUMO gap, and polarizability in disubstituted polyynes and cumulenes. 42 The main conclusion was that some combinations of X and Y groups cause higher changes in polarizability and the HOMO–LUMO gap than others. Hence, it is possible to tune optical and electric properties of polyynes and cumulenes by substitution.…”