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Journal of Spectroscopy
Volume 2016 (2016), Article ID 3520698, 12 pages
http://dx.doi.org/10.1155/2016/3520698
Research Article

Optical Properties of DMA-π-DCV Derivatives: A Theoretical Inspection under the DFT Microscope

Instituto de Ciencia Molecular, Universidad de Valencia, 46890 Paterna, Spain

Received 17 August 2016; Accepted 4 October 2016

Academic Editor: Jau-Wern Chiou

Copyright © 2016 Joaquín Calbo. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

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 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.