Synthesis and Electronic Properties of Directly Linked Dihydrodiazatetracene Dimers

5,12-Dihydro-5,12-diazatetracene (DHDAT) dimers with different substitution patterns are synthesized: a symmetric one with a C?C bond between the monomer units ( 1 ) and two asymmetric ones with a C?N bond between the monomer units ( 2 and 3 ). The DHDAT units are planar in the C?C linked dimer 1 but perpendicularly oriented in the C?N linked dimers 2 and 3 (from X-ray analysis). The electronic ground-state interaction between the two units is large in 1 and small in 2 and 3 . The emission behavior of 3 is different from that of other dimers and its monomer; it displays positive solvatochromism, characteristic for electron donor–acceptor molecules, despite its donor–donor type structure. Compound 3 exhibits a unique multi-step thermochromic emission behavior. The emission behavior is attributed to the asymmetric distribution of the HOMO and LUMO of DHDAT.