How Boron Doping Shapes the Optoelectronic Properties of Canonical and Phenylene-Containing Oligoacenes: A Combined Experimental and Theoretical Investigation.
Optimized syntheses of 6,13-dimesityl-6,13-dihydro-6,13-diborapentacene (DBP) and a related compound (DBI) featuring two biphenylene-2,3-diyl units in place of naphthalene-2,3-diyl moieties are reported. Striking differences between the optoelectronic properties of DBP and DBI have been experimentally observed, and explained by quantum chemical calculations. DBP is a member of the oligoacene family, DBI is a linear [N]phenylene derivative. The yellow DBP shows blue photoluminescence, the deep red DBI is nonfluorescent. Both compounds give rise to two reversible redox transitions at E1/2 =-2.03 V, -2.75 V (DBP) and -1.52 V, -2.30 V (DBI; THF, vs. FcH/FcH+). The higher electron affinity of DBI agrees with a lower calculated LUMO energy level [-0.57 eV for DBI with respect to DBP @HF//SCS-MP2/def2-TZVP] and a higher Lewis acidity of its boron centers, which is reflected in the trend of adduct formation with small Lewis bases (MeCN, F-). The thermochemistry underlying this trend, as well as the mechanism of fluorescence quenching in DBI, are revealed by state-of-the-art quantum chemical calculations. It is suggested that the nonradiative deactivation occurs via a low-lying, doubly excited state.
Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt/Main, Max-von-Laue-Straße 7, 60438, Frankfurt/M, Germany.
Sven
S
Kirschner
Interdisciplinary Center for Scientific Computing, Ruprechts-Karls University, Im Neuenheimer Feld 205, 69120, Heidelberg, Germany.|Centre for Theoretical Chemistry and Physics, The New Zealand Institute for Advanced Study (NZIAS), Massey University Albany, Private Bag 102904, Auckland, 0745, New Zealand.
Jan-Michael
JM
Mewes
Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt/Main, Max-von-Laue-Straße 7, 60438, Frankfurt/M, Germany.
Michael
M
Bolte
Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt/Main, Max-von-Laue-Straße 7, 60438, Frankfurt/M, Germany.
Hans-Wolfram
HW
Lerner
Interdisciplinary Center for Scientific Computing, Ruprechts-Karls University, Im Neuenheimer Feld 205, 69120, Heidelberg, Germany.
Andreas
A
Dreuw
Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt/Main, Max-von-Laue-Straße 7, 60438, Frankfurt/M, Germany.
Matthias
M
Wagner
computational chemistry; density functional calculations; luminescence; organoboranes; polycyclic aromatic hydrocarbons