Fine tuning of the one- and two-photon absorption properties of macrocyclic thiophene-based derivatives

The geometrical and electronic structures, and one- and two-photon absorption properties of macrocyclic thiophenes possessing push-pull groups were investigated. It shows that λ(1)maxs appear red-shift for the designed macrocycles with strong donor/acceptor (D/A) substituents, and the red-shifts enlarge as increasing the number of D/A pair. As a result, their two-photon absorption cross-section (δmax)s get larger, and the configurations with donor and acceptor location on the opposite site can result in larger δmax, which is ascribed to the enlargement of the stronger intramolecular charge transfer (ICT) between D and A or the inside of the whole ring skeleton. Taking SII series of molecules as an example, the enlargement of the net charge change (ΔQ) is one factor for the increase of δmax. Moreover, transition dipole moments (M0k and Mkn) play important roles on the increase of δmax. And the product of oscillator strengths (f0k × fkn) is in proportion to δmax.

► Influences from D/A pair, type and position for substituents have been discussed.
► λ(1)maxs of the designed molecules with D or A substituents have red-shifted.
► δmaxs increase with increasing the number of D/A pair.
► δmaxs of D–A type are close to A–A, and larger than that of D–D.
► Larger value of δmax is obtained when D and A locate on the opposite site.