Performance of DFT Methods in the Calculation of Optical Spectra of TCF-Chromophores


Andzelm, J. ; Rinderspacher, B. C. ; Rawlett, A. ; Dougherty, J. ; Baer, R. ; Govind, N. Performance of DFT Methods in the Calculation of Optical Spectra of TCF-Chromophores. J. Chem. Theory Comput. 2009, 5 2835–2846.
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We present electronic structure calculations of the ultraviolet/visible (UV?vis) spectra of highly active push?pull chromophores containing the tricyanofuran (TCF) acceptor group. In particular, we have applied the recently developed long-range corrected Baer-Neuhauser-Livshits (BNL) exchange-correlation functional. The performance of this functional compares favorably with other density functional theory (DFT) approaches, including the CAM-B3LYP functional. The accuracy of UV-vis results for these molecules is best at low values of attenuation parameters (\gamma) for both BNL and CAM-B3LYP functionals. The optimal value of \gamma is different for the charge-transfer (CT) and valence excitations. The BNL and PBE0 exchange correlation functionals capture the CT states particularly well, while the ???* excitations are less accurate and system dependent. Chromophore conformations, which considerably affect the molecular hyperpolarizability, do not significantly influence the UV?vis spectra on average. As expected, the color of chromophores is a sensitive function of modifications to its conjugated framework and is not significantly affected by increasing aliphatic chain length linking a chromophore to a polymer. For selected push?pull aryl-chromophores, we find a significant dependence of absorption spectra on the strength of diphenylaminophenyl donors.



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