Synthesis, Crystal Structure, Weak Interactions, and Optical Properties of an Organic Charge-Transfer Benzyl 2-Aminopyridinium Picrate Compound

Abstract

In this work, a new organic charge-transfer compound, namely 1-benzyl 2-aminopyridinium picrate [Bz-2-NH₂Py][PIC] (1), is prepared and characterized by single crystal X-ray diffraction (SC-XRD), powder X-ray diffraction (PXRD), FTIR, ¹H NMR and Raman spectroscopy. The title compound crystallizes in the monoclinic system with space group P2(1)/c and contains one [Bz-2-NH₂Py]⁺ cation and one [PIC]^– anion. The cations are stacked into a columnar structure through C–H⋯π interactions, and the N–H⋯O and C–H⋯O hydrogen bonds between the anions and cations stabilize the crystal stacking of [Bz-2-NH₂Py][PIC] (1). The frontier molecular orbitals HOMO and LUMO are computed by the DFT approach (using the B3LYP/6-31G (d,p) basis set) to understand the chemical reactivity and kinetic stability of the title compound. The geometrical parameters obtained from the XRD experiment are in good agreement with the simulated values from the single crystal structure. In addition, the organic material shows two main emission peaks at about 390 nm and 469 nm upon 241 nm excitation in the solid state at room temperature. The Hirshfeld surface analysis is performed to quantify the contributions of different intermolecular interactions.