Calculation of excitation energies of organic chromophores: a critical evaluation

A series of organic compounds with first-row elements was calculated to determine the performance of TD-DFRT (time-dependent density functional response theory) and to compare with the performance of approximate or semiempirical methods (TD-DFRT-TB, ZINDO/S, PM3/S). The mean absolute deviation between theoretical and experimental excitation energies is lowest for TD-DFRT. Because of poor results in some cases the error of TD-DFT was distinctly larger in the calculations of sulfur-free than in the calculation of sulfur-containing compounds. General spectral absorption features are reasonably well reproduced by the approximate TD-DFRT in tight-binding approximation (TD-DFRT-TB) and by semiempirical MO-CI methods based on the NDO (ZINDO/S) or the NDDO approach (PM3/S). If the limitations of ZINDO/S are considered the method is useful in calculating n --> pi*- and pi --> pi*-type transitions. (C) 2002 Elsevier Science B.V. All rights reserved.