Reliable prediction of charge transfer excitations in molecular complexes using time-dependent density functional theory.

We show how charge transfer excitations at molecular complexes can be calculated quantitatively using time-dependent density functional theory. Predictive power is obtained from range-separated hybrid functionals using nonempirical tuning of the range-splitting parameter. Excellent performance of this approach is obtained for a series of complexes composed of various aromatic donors and the tetracyanoethylene acceptor, paving the way to systematic nonempirical quantitative studies of charge-transfer excitations in real systems.