Intramolecular charge transfer in elongated donor-acceptor conjugated polyenes

Large Quadratic Hyperpolarizabilities with Donor–Acceptor Polyenes Exhibiting Optimum Bond Length Alternation: Correlation Between Structure and Hyperpolarizability

“…[1'-23J This effect can be related to the red shift of the ICT transition as well as to the concomitant increases of both the transition dipole and the photoinduced change in dipole ( A p ) that have been demonstrated experimentally for several series of push -pull phenylpolyenes and diphenylpolyenes of increasing size. [24,251 Previous experimental studies also demonstrated that the nature of the end groups strongly influences both the magnitude of [j and its chain-length behavior.…”

“…In particular, molecules 3a[l] and 3b[l] show very small Ap values and are most probably very close to the cyanine limit in dioxane. It should also be emphasized that lengthening the polyenic chain linking the donor to the acceptor end groups results in an increase of both pol and Ap values, as well as a decrease of the transition energy as noted previously, [24,251 so that significant enhancement of the quadratic hyperpolarizability is expected, based on the two-level approximation [see Eq. (I)].…”

Dependence of Spurious Charge-Transfer Excited States on Orbital Exchange in TDDFT: Large Molecules and Clusters

“…41,42 The calculated excited-state energy shifts to the blue with an increase of the fraction of orbital exchange. Likewise, the oscillator strength of the transition follows the fraction of exchange.…”

“…39,40 Finally, the chlorophylls constitute the main pigment in the biological photosynthetic light-harvesting complexes. 35,36 Previous theoretical work within DFT on some of these systems has been carried out within the DFT formalism for donor-acceptor molecules, 41,42 thiophenes, 43 and bacteriochlorophylls. 44,45 Here Ground-state geometry optimizations of the charge-neutral, singlet states of the substituted molecules have been done with the Turbomole program suite.…”

Fluorescent difluoroboron-curcumin analogs: An investigation of the electronic structures and photophysical properties

“…(Tables 2 and S1-S3). The molecular system therefore corresponds to donor-p-acceptor-p-donor, with considerable intramolecular charge transfer characteristic (ICT) [52][53][54]. As seen in the optimized geometry of the ground and excited states the changes in the dihedral angle, bond angle and bond lengths upon excitation remain nearly same in two symmetrical donor cores (Table 2), thus suggesting that the molecule remain in planar geometry in ground as well as in excited states.…”