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The one-photon and two-photon absorption properties of donor–acceptor substituted dehydrobenzo[18]annulenes were determined by using density functional theory and ZINDO methods. The macrocycle containing C2v symmetry exhibited the largest TPA cross-section value of 3376 × 10–50 cm4 s/photon. The calculated results indicate that the TPA response in the whole molecule comes from the contribution of that in the every side in the trigon. It is notable that the magnitudes of the transition dipole moment from the virtual intermediate state to the TPA final state and the dipole moment difference between the ground state and the virtual intermediate state play important roles in increasing the TPA cross-section value. This series of molecules can circumvent the trade-off between efficiency and transparency, and they provide a promising direction for the further development of novel two-dimensional molecules with such properties.Key words: two-photon absorption, ZINDO, sum-over-states, dehydrobenzo[18] annulenes, transparency.

The one-photon absorption (OPA) properties of tetrabenzoporphyrins (TBPs) and phthalocyanines (Pcs) were studied using the semiempirical ZINDO method and time-dependent density functional theory (TDDFT), respectively. The compared results confirmed that the semiempirical ZINDO method was reasonably reliable when calculating the OPA of tetrabenzoporphyrins and phthalocyanines. On the basis of the OPA properties obtained from the ZINDO method, two-photon absorption (TPA) properties of two series of molecules were investigated, using ZINDO and sum-over-states (SOS) methods. The results showed that the TPA cross-sections of all molecules were in the range of 220.6 × 10–50 – 345.9 × 10–50 cm4·s·photon–1, which were in the same order of magnitude as the values reported in the literature. The relatively larger δ(ω) value for Pcs with respect to that for corresponding TBPs originates from larger intramolecular charge transfer, which can be characterized by the difference of dipole moment between S0 and S1 and the transition dipole moment between S1 and S5.Key words: two-photon absorption, ZINDO, sum-over-states, tetrabenzoporphyrin, phthalocyanines.

The semiempirical INDO calculations were carried out to investigate the charge-transfer interaction and to evaluate the second-order nonlinear susceptibilities for a series of fulleropyrrolidine–tetrathiafulvalene(C60PY–TTF) dyads, C60PY, and C60PY-(CH=CH)n-TTF (n = 0–6). The equilibrium geometries, electronic structures, and UV–vis spectra of these C60PY–TTFs D–B–A dyads were determined by using ZINDO methods. On the basis of electronic spectra, we calculated the β for the dyads using the ZINDO-SOS expression, and found that these dyads have relatively large β. The calculated values of β are 48.78, 62.34, 97.90, 123.24, 183.78, 189.43, 193.45, 195.82 × 10–30 esu for C60PY and C60PY-(CH=CH)n-TTF (n = 0–6), respectively, which shows the enhancing effect when TTF is introduced. The β significantly increases as n increases from 0–3; and it tends to be saturated in the end.Key words: ZINDO-SOS, CI, structure, spectra, C60PY–TTF.