Optical properties of DMA-π-DCV derivatives: A theoretical inspection under the DFT microscope

The optical properties of a series of donor-acceptor n,n-dimethylaniline-π-dicyanovinylene (dma-π-dcv) chromophores have been investigated under the density functional theory framework. focus has been made on the low-lying charge-transfer (ct) electronic transitions for which experimental data is available. the effect of the π-conjugated bridge length and type was analysed between the families of oligoene and oligoyne derivatives of increasing size. theoretical calculations demonstrate that the ethylene bridge is a better π-communicator and allows for more delocalized frontier molecular orbitals compared to the acetylene spacer. the λ diagnostic test allowed rationalization of the orbital spatial overlap in the main ct excitations. the performance of different density functional rungs was assessed in the prediction of the lowest-lying ct electronic transition. surprisingly,most modern long-range corrected functionals demonstrated to provide among the largest errors,whereas hybrid functionals showed the best performance. solvatochromism was confirmed in both oligoene and oligoyne compounds. a donor-acceptor-donor triad based on tetrathiafulvalene was utilised as a test system for the prediction of its two ct bands of different nature,energy,and intensity. the hybrid pbe0 (or a similar hybrid analogue) consolidates as the best choice for the prediction of ct excitations in the dma-π-dcv push-pull family. © 2016 joaquín calbo.