Photophysical and Electrical Properties of Highly Luminescent 2/6-Triazolyl-Substituted Push–Pull Purines
Armands Sebris, Irina Novosjolova, Kaspars Traskovskis, Valdis Kokars, Natalija Tetervenoka, Aivars Vembris, Māris Turks
Abstract
(9)-alkylated 6-piperidino-2-triazolylpurine and 2-piperidino-6-triazolylpurine derivatives are synthesized, and their optical and optoelectronic properties are comprehensively characterized with experimental and computational methods. The compounds possess intense violet or blue fluorescence with fluorescence quantum yields of up to 91% in solution and 40% in host-free films. Depending on their structural composition, the compounds have ionization energy in the range of 5.25-6.04 eV, electron affinity of 2.18-3.15 eV, and triplet energy of 2.52-2.95 eV. Due to the presence of hole-transporting purine and electron-transporting triazole fragments, compounds exhibit bipolar charge-transportation ability. Despite the favorable emissive properties of the studied push-pull purines, their electroluminescence in thin films is quenched owing to large current densities that are present even at a moderate driving voltage. This marks application directions related to a predominantly charge-transportation functionality as the most suitable for this compound class.