*2.1. General*

All the chemicals were reagent grade. Procainamide (purity > 99.5) was purchased from Sigma-Aldrich (Darmstadt, Germany), and chloranilic acid and 2,3-dichloro-5,6 dicyano-1,4-benzoquinone were purchased from Merck (Darmstadt, Germany). Melting points were determined on a Barnstead electrothermal digital melting point apparatus, model IA9100, BIBBY scientific limited Stone (Staffordshire, UK). IR spectra were recorded on a Jasco FT/IR-6600 spectrometer (Tokyo, Japan) in KBr. NMR spectra were taken from 400 MHz premium shielded NMR spectroscopy in deuterated dimethyl sulfoxide (DMSO*d6*) (Agilent Technologies, Santa Clara, CA, USA). UV-vis spectra were measured using a Genesis G10S UV-Vis spectrophotometer (Thermo Fisher Scientific, Pleasanton, CA, USA), using acetonitrile as the solvent. All the measurements were performed using various solvents and quartz cells with a path length of 1 cm. The UV-Vis spectra in the solution were measured over the range of 200–700 nm. The conductivities of procainamide and its CT complexes (PA-ChA and PA-DDQ) were measured on an Orion conductometer (Beverly, MA, USA).
