Conjugated donor-acceptor substituted systems involving the 1,3-indandione-derived electron accepting moieties.

Conjugated donor-acceptor molecules are the focus of research owing to their unusual photo- and electro-physical properties. At the same time, several unusual features of these compounds are difficult to explain or predict. Here we present our results on the synthesis, X-ray structures and D-NMR spectra providing a deeper insight into the conjugation within the derivatives involving the 1,3-indandione-derived series of compounds with varying electron acceptor strength and conjugating bridge length.

Dipole moments of conjugated donor-acceptor substituted systems: calculations experiments.

We find that quantum mechanical calculations using B3LYP/aug-cc-pVTZ model chemistry involving anharmonic correction on simple conjugated organic compounds without rotating moieties provide the dipole moment values and molecular geometries with high accuracy. In the presence of one or two conjugated electron donating or accepting substituents capable of hindered rotation, the calculated dipole moments reproduce the experimental results equally well only in the cases when the experiments were done at the temperatures at which rotation of substituents remains hindered. In order to reproduce the experimental dipole moments determined at higher temperatures, a model assuming free (unhindered) rotation should be applied.

Hindered rotational barriers in conjugated donor-acceptor substituted systems: calculations vs. experiments.

Quantum mechanical calculations of barriers to rotation within push-pull π-conjugated molecules involving strong electron donors (D) and acceptors (A) using the generally accepted approach fail to reproduce the experimental barriers determined by temperature-dependent NMR spectra. On the examples of seven derivatives of this type with substituents of varying electron donating and accepting strength, we find that determination of one of the rotational barriers, for instance, that of the acceptor substituent, requires not only the energy calculation of the respective transition state of this substituent, but also the transition state of the donor and the transition state involving both donor and acceptor substituents. Calculations of the rotation barriers using B3LYP and APFD functionals considering three transition states produce the results with mean absolute deviations from 10 experimental barriers of 0.

Prediction of the spectral reflectance of laser-generated color prints by combination of an optical model and learning methods.

Recent color printing technologies based on the principle of revealing colors on pre-functionalized achromatic supports by laser irradiation offer advanced functionalities, especially for security applications. However, for such technologies, the color prediction is challenging, compared to classic ink-transfer printing systems. The spectral properties of the coloring materials modified by the lasers are not precisely known and may strongly vary, depending on the laser settings, in a nonlinear manner.