N‐Acenoacenes

Abstract The syntheses of new, fourfold alkynylated tetraazaacenoacenes (tetraazaanthracenoanthracene, tetraazatetracenotetracene and tetraazapentacenopentacene) are reported. This novel heteroacenoacene motif exhibits surprisingly strong electronic coupling between its constituting diazaacene units.


X-ray single-crystal structure analysis
X-ray single-crystal structure analyses were measured on a Bruker Smart APEX-II Quazar Area Detector diffractometer by Dr. F. Rominger (Heidelberg University). Diffraction intensities were corrected for Lorentz and polarization effects. An empirical absorption correction was applied using SADABS based on the Laue symmetry of reciprocal space. Heavy atom diffractions were solved by direct methods and refined against F2 with the full matrix least square algorithm. Hydrogen atoms were either isotropically refined or calculated. The structures were solved and refined using the SHELXTL software package.

UV-Vis and fluorescence spectroscopy
Absorption spectra were recorded on a Jasco UV-Vis V-660 or Jasco UV-Vis V-670.
Fluorescence spectra were recorded on a Jasco FP-6500.

Quantum yields
Quantum yields were determined by an Ulbricht sphere (6 inch) using a PTI QuantaMaster 40 equipped with a Hamamatsu R928P Photomultiplier.

Camera
The photos were taken by a Canon EOS 7D under daylight or UV-light irradiation (λ = 365 nm).

Computational studies
Computational studies were carried out using DFT calculations on Turbomole 6.3.1 and Gaussian16. Geometry optimizations were performed using the B3LYP functional and def2-TZVP basis set. At this geometry, the absolute energy, NICS(1) values and FMO energies were assigned by a single-point approach at the B3LYP/6-311++G** level. [2] S2.
Then anhydrous, degassed toluene was added, and the reaction mixture stirred at 110 °C for 24 h. The mixture was cooled to room temperature and diluted with water (10mL). The phases were separated, and the aqueous layer was extracted with dichloromethane (3×10 mL). The combined organic phases were washed with brine (10 mL), dried over magnesium sulfate and filtrated. The solvent was removed under reduced pressure and the crude product was absorbed on Celite ® . After flash column chromatography (petroleum ether/diethyl ether 250:1 v/v) and gel permeation chromatography (toluene) the product was isolated.