TDDFT-calculations of Vis/NIR absorbing compounds

To examine the strengths and limitations of the time-dependent density functional theory in calculating the absorption wavelengths of dye, 130, non-radical, radical and biradical coloured organic compounds, including perylenimide, porphyrin, azobenzene, quinone, croconaine, squaraine and push-pull-type were randomly selected. The first intense electronic transitions were satisfactorily calculated colorants, using time-dependent density functional theory. Whilst polymethine dyes behaved exceptionally, the calculated transition energies for cyanines, oxonols and various related dyes were systematically too large. Broken-symmetry unrestricted density functional calculations revealed the biradical character of several quinoid compounds derived from p-quinodimethane as well as that of some non-Kekule-type structures. (C) 2009 Elsevier Ltd. All rights reserved.