Dicyanopyrazino phenanthrene based charge transfer derivatives: Role of amine donor in tuning of photophysical, aggregation-induced emission, electrochemical and theoretical properties

Abstract

Herein Buchwald-Hartwig amination reaction employed for the synthesis of donor−acceptor−donor (D−A−D) structured, C–N coupled 2,3−dicyanopyrazino phenanthrene (DCPP) amines 2‒6. Further dyes characterized by spectroscopic viz. NMR, MALDI-TOF, IR techniques. The acquired intramolecular charge transfer (ICT) (λICT = 403–490 nm) transitions by donation of electron from donor to acceptor via C–N coupling in dyes confer D−A assembly. Also ICT properties of dyes found aligned with the donating strength of coupled amine in dyes. As a result dyes emit in blue−green region (λemi = 469–549 nm) in solution and solid film along with notable positive solvatochromism. Moreover aggregation-induced emission (AIE) characteristics in dyes found affected by the size of nanoparticle formed in THF/H2O media. Accordingly dye 2 and 6 exhibit AIE property among other dyes due to formation of emissive, small size nanoparticles in the media. Further comparable HOMO (−5.19 to −5.83 eV) and LUMO (−3.02 to −3.27 eV) energies of dyes with reported small organic ambipolar materials are remarkable towards its utilization in organic electronics. The band gap (2.16 to 2.66 eV) are also matches well with reported blue-emitting organic semiconductors. Density functional theory (DFT) and time-dependent density-functional theory (TDDFT) calculations agree with the experimental opto-electrochemical data. Thus opto-electrochemical properties possess by dyes undersigned its desired application in optoelectronic devices.