Two new coronene charge transfer
complexes with F4-TCNQ
of 2:1 and 1:1:1 (solvate with acetonitrile, MeCN) stoichiometry were
obtained using crystal growth procedures from the solution and vapor
phase. It was shown that mobility of coronene molecules in crystals
is more affected by the asymmetry of its surrounding than by the composition
and degree of charge transfer and interstack interactions. The combination
of X-ray diffraction and electrochemistry in the solid state and a
time-resolved one in solution allowed us to clarify the nucleation
in solution showing that the formation of 2:1 coronene/F4-TCNQ complexes is thermodynamically preferable. The X-ray single
crystal data for pristine coronene showed the crystal structure to
be the same as at ambient temperature, raising doubt about the previously
reported phase transitions at 140–180 K.
To assess the ability of the quantum-chemical computations to reproduce the experimental relative intensities in the infrared (IR) spectra of both the gas- and condensed-phase systems, the hybrid DFT functional B3LYP has been applied to simulation of IR spectra for species containing from three to twelve first- or second-row atoms, both in the gas phase and in CCl4 solutions. The results demonstrate that B3LYP, combined with the highly compact double-ζ basis set 6-31+G* and "scaled quantum mechanics" techniques, offers excellent quantitative performance in the calculations of relative IR intensities and frequencies (ν ≤ 2200 cm(-1)) for the bands of vibrations of medium-size isolated molecules, whereas it produces unsatisfactory results for the solutions of the same species. Neither larger basis sets nor implicit treatment of the media effects improve the agreement of the simulated spectra with the condensed-phase experiment. At the same time, some preliminary results suggest that explicit modeling of media effects could offer better quality of the IR spectral simulations for the condensed-phase systems.
Quantum chemical modeling in combination with vibrational and electronic absorption spectroscopy has delivered detailed information about supramolecular organization of azochromophore 4-amino-4′-nitroazobenzene (DO3), its solutions, and blends with poly(methyl methacrylate) (PMMA) polymer of various concentrations. It is shown that the neat chromophore contains both antistacked forms and hydrogen bonded associations of the "head-to-tail" type, while separate DO3 molecules dominate in diluted solutions of DO3 in chloroform. In PMMA/DO3 films with low concentrations of the chromophore, DO3 is mainly Hbonded to CO moieties of PMMA matrix, while in the blends with high concentrations of DO3 molecules, the latter form hydrogen bonds both with PMMA and with each other. Infrared, Raman, and UV−vis spectroscopic markers of isolated DO3 molecules and various modes of their supramolecular associations are revealed.
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