The influence study of the number of substituted heteroaryls at the non-K region of pyrene structure on the photophysical properties based on the example of pyrene with 1-decyl-1H-1,2,3-triazole motif

Abstract

The study of the photophysical properties (thermal - thermogravimetric analysis and optical - absorption, emission in the solution and in powder, quantum efficiency of emission and efficient fluorescence lifetime in the solution) with the focus on the influence of the number of substituted 1-decyl-1H-1,2,3-triazole groups at the non-K region of pyrene structure. To the best of our knowledge, the investigation of the impact of the number of heteroaryl groups at the non-K region of pyrene is reported for the first time. The obtained results for monosubstituted derivative (1) were compared to di- (2, 3) and tetra- (4) analogues previously reported by us in the literature. In addition, theoretical studies based on DFT and TD-DFT were performed to support interpreting the experimental results. A strong influence of the number of substituted heteroaryls at the non-K region of pyrene on the photophysical properties was noticed. Theoretical calculations revealed that an increasing number of substituted groups decrease the contribution of pyrene in the creation of frontier orbitals for HOMO from 88 to 72% and LUMO from 91 to 74%, with a simultaneous increase of 1-decyl-1H-1,2,3-triazole. The energy gap values follow the same trend, the highest was established for monosubstituted ΔE = 3.62 eV and the lowest for tetrasubstituted ΔE = 3.16 eV. Considering the results of TD-DFT calculations for monosubstituted pyrene, there are no differences in the character of transitions related to absorption and emission in reference to the number of substituted triazole groups at the pyrene core. Therefore, the increasing number of substituted heteroaryls results in red-shifted absorption and emission in the solution and in the solid state (up to 50 nm), increasing the quantum efficiency from 37 to 72% and lower efficient fluorescence lifetime from 9.25 to 2.03 ns.