Methoxyphenyl indenopyrazoloquinoline derivatives as green fluorescent emitters for polymer based electroluminescent devices

Paper reports synthesis aspects and spectroscopic properties of three newly synthesized trimethyl derivatives of methoxyphenyl indenopyrazoloquinoline (MPTM-IPQ) compounds representing a subclass of azafluoranthene dyes. The spectroscopic studies are supplemented by cyclic voltammetry measurements and quantum-chemical calculations using DFT/TDDFT/PCM method at the B3LYP/6-31+G(d,p) level of theory. The absorption/fluorescence processes appear to be weakly dependent on the side position of the methyl radicals exhibiting the first absorption band in the region of 445–450 nm and the fluorescence band in the range of 530–540 nm. A considerable Stokes shift (85–100 nm) originates in all the dyes mainly from the solute relaxation in the excited state. The electroluminescence devices with an active PVK layer doped by MPTM-IPQ dyes have been designed. All the devices exhibit green electroluminescence with the emission maximum being rather weakly dependent on the type of the fluorescent dopant. The obtained results demonstrate that a series of newly synthesized MPTM-IPQ dyes may be considered as perspective green fluorescent emitters for electroluminescent applications.

► Synthesis of novel indenopyrazoloquinoline derivatives is described. ► Spectroscopy and cyclic voltammetry studies of these dyes are reported. ► Excitation energies are compared with the TDDFT calculations. ► Indenopyrazoloquinoline based electroluminescence devices are demonstrated. ► Indenopyrazoloquinolines represent green fluorescence emitters.