Blue-orange emitting carbazole based donor-acceptor derivatives: Synthesis and studies of modulating acceptor unit on opto-electrochemical and theoretical properties

In order to demonstrate an effect of varying acceptor unit on optoelectronic properties of Donor-Acceptor (D-A) assembly, we herein designed and synthesized C-N coupled, carbazole based dyes 1-8 by employing Buchwald-Hartwig coupling amination reaction and fully characterized by spectroscopic methods. Presence of intramolecular charge transfer (ICT) transitions (lambda(max) = 403-467 nm) in absorption spectra of all dyes reminiscent D-A assembly in it and emit in blue-yellow region (lambda(emm) = 467-565 nm) in solution state with marked positive solvatochromism. The photophysical studies of some of the dyes in different THF/water mixtures revealed aggregation-induced emission (AIE) feature with the nanoparticles formation, as confirmed by dynamic light scattering (DLS) technique. The HOMO ( -5.42 to -5.74 eV) and LUMO ( -3.03 to -3.50 eV) energy level of these molecules measured by cyclic voltammetry suggest electron transporting property in it. Further, DFT/ TDDFT calculation of dyes, indicate quite comparable theoretical and experimental photophysical and electro-chemical data. Moreover, calculated singlet (S-1) and triplet (T-1) excitation energy levels by DFT/B3LYP/6-311 G+(d,p) shows small Delta E-ST value for some dyes and hence called as TADF emitters. Thus obtained all optoelectrochemical properties of dyes propose its potential use in optoelectronic devices and in biosensing.

Automated summary

This study designed and synthesized carbazole-based dyes, characterized by spectroscopic methods to demonstrate the D-A assembly properties. The dyes exhibited blue-yellow emission and aggregation-induced emission in solution state, showing potential for applications in optoelectronic devices.