ABSTRACT
We report the annulation of heterocyclic building blocks to access π-extended polycyclic aromatic hydrocarbons (PAHs). The method involves the trapping of short-lived hetarynes with catalytically-generated biaryl palladium intermediates and allows for the concise appendage of three or more fused aromatic rings about a central heterocyclic building block. Our studies focus on annulating the indole and carbazole heterocycles through the use of indolyne and carbazolyne chemistry, respectively, the latter of which required the synthesis of a new carbazolyne precursor. Notably, these represent rare examples of transition metal-catalyzed reactions of N-containing hetarynes. We demonstrate the utility of our methodology in the synthesis of heterocyclic π-extended PAHs, which were then applied as ligands in two-coordinate metal complexes. As a result of these studies, we identified a new thermally-activated delayed fluorescence (TADF) emitter that displays up to 81% photoluminescence efficiency, along with insight into structure-property relationships. These studies underscore the utility of heterocyclic strained intermediates in the synthesis and study of organic materials.
ABSTRACT
The synthesis and characterization of zinc(II) chelates bearing acridin-4-ol (A), phenazin-1-ol (P), and benzo[b]phenazin-1-ol (bP) are presented. The formation of homoleptic (ZnX2) or heteroleptic (ZnX1) products can be controlled by stochiometric or excess amounts of zinc(II) acetylacetonate monohydrate, Zn(acac)2, respectively. Electrochemical and photophysical studies show that the homoleptic complexes (ZnA2, ZnP2, and ZnbP2) have ligand-centered properties inherited from the corresponding free ligands. Calculations using density functional theory (DFT) agree with the observed experimental ligand-centered photophysical and electrochemical behavior.
ABSTRACT
Tetra-aza-pentacenes are attractive n-type small molecules for optoelectronic device applications, yet their syntheses are often laborious. Disclosed here is a one-pot Friedländer synthesis of 1,7,8,14-tetraazapentacece (tAP) derivatives (linear and/or bent), fully aromatized in situ despite the absence of an exogenous oxidant. The photophysics of linear tAPs resembles that of regular pentacene though their crystal structures differ. A LUMO energy of -3.71â eV for di-tert-butylanisole-substituted linear tAP is similar to that of the well-known acceptor, C60 .
