Charge transfer and hydrogen bonding motifs in organic cocrystals derived from aromatic diamines and TCNB

Abstract

Herein, we have successfully fabricated two Charge transfer (CT) cocrystals 1 and 2 using 1,2,4,5-tetracyanobenzene (TCNB) as an acceptor with aromatic diamine (o-phenylenediamine and benzidine) as hydrogen bond (H-bonds) donor compounds. These binary compounds were characterized comprehensively by Single Crystal X-ray diffraction (SCXRD), powder diffraction, thermal, and spectroscopic analysis (Infrared and UV–vis spectroscopy) in the solid state. CT π···π interactions help to achieve the binary (1:1) mixed staking (DADA) supramolecular self-assembly while the dominant N−H··N and C−H··N H-bonds are exclusively involved in accomplishing the 2D structure as evidenced by the single-crystal analysis in these two cocrystals. Owing to the strong absorption in the near-infrared region (NIR) these materials appear black by virtue of charge transfer which is a fascinating phenomenon in TCNB based complexes. Not to mention, Hirshfeld surface analyses and density functional theory (DFT) were performed to assess the contribution of different intermolecular interactions and HOMO-LUMO energy levels. The present study will help to expand the understanding of non-covalent interactions in these hybrid materials which may further expand the library of functional materials that can find fascinating applications in the future.