Computational modeling for the design of new fluorescent organic compounds based on both diketopyrrolopyrrole and nitrobenzofurazan moieties

Three examples of organic π-conjugated systems, based on both diketopyrrolopyrrole (DPP) and nitrobenzofurazan (NBD) were theoretically designed as host fluorescent materials that all of them emitted intense infrared fluorescence and the maximum emission bands ranged from 841 nm to 868 nm. Theoretical analysis by utilizing density function theory (DFT) and its extension of TD-DFT methods with B3LYP functional at the 6–311 g(d,p) calculation level, in acetonitrile, have been reported on the geometry, optoelectronic, absorption/emission characteristics of the studied materials. The furan-, thiophene-, or selenophene-flanked-DPP and coupled to NBD, named after M1 (X = O), M2 (X = S) and M3 (X = Se), have a great impact on optoelectronic properties to design lower optical band gap materials with excellent nonlinear optical (NLO) properties and efficient intra-molecular charge transfer (ICT). The studied molecular structures adopt a planar geometry stabilized by intra-molecular non-covalent interactions (NCIs). The reduced density gradient (RDG) has been further developed to analyze and understand the typical NCIs and their characteristics. The analysis of electron density and its reduced density gradient (RDG), NCIs, the topological analyses from MEP, ELF and LOL, QTAIM were carried out to evaluate the charge transfer within the investigated compounds.