Highly Twisted Triarylamines for Photoinduced Intramolecular Charge Transfer

Abstract

9-(<i>N</i>,<i>N</i>-Dianisylamino)anthracene (<b>9DAAA</b>), 9-(<i>N</i>,<i>N</i>-dianisylamino)dinaphth([1,2-<i>a</i>:2′-1′-<i>j</i>]-anthracene (<b>9DAAH</b>), and 9,10-bis(<i>N</i>,<i>N</i>-dianisylamino)anthracene (<b>910BAA</b>) were synthesized as highly twisted triarylamines with potential for photoexcited internal charge transfer. Crystallography of <b>9DAAA</b> shows its dianisylamino group to be twisted nearly perpendicular to its anthracene unit, similar to a report for <b>910BAA</b>. The solution fluorescence spectra show strong bathochromic shifts for each of the three molecular systems with strongly decreased quantum efficiency in higher polarity solvents. Solution-phase (ensemble) time-resolved photoluminescence measurements show up to 4-fold decreases in fluorescence lifetime in acetonitrile compared to hexane. The combined results are consistent with photoinduced, transient intramolecular charge-transfer from the bis-anisylamine unit to the polycyclic aromatic unit. Computational modeling is in accord with intramolecular transfer of electron density from the bis-anisylamino unit to the anthracene, based on in comparisons of HOMO and LUMO.