Signatures of Through-Space Charge Transfer in Two-Photon Absorption of Paracyclophane Derivatives

Third order polarizability, (γ) taken from the collective electronic oscillator (CEO) method was used to calculate the two-photon absorption (TPA) of tetrastyryl-[2,2]paracyclophane derivatives with different through-space charge transfer configurations considering various donor and acceptor combinations at the terminal styryl groups. For the virtually same linear absorption, different TPA spectra were obtained. For controlling and fine-tuning frequency and cross-sections of TPA the through-space charge transfer interactions can be used. The results are explained by the electronic density matrices corresponding to governing oscillators in one- and two-photon absorption and the ground state. It is indicated that for the studied systems mainly the lowest four oscillators are responsible for the TPA cross-sections rather than a simple effective three-state model.