Characterization, molecular modelling, and thermochemistry of proton-transfer adducts derived from interaction of piperidine and morpholine with two strong organic acceptors

Abstract

This study investigates the formation and properties of three proton-transfer complexes: piperidine-picric acid (PIP–PA), piperidine-7,7,8,8-tetracyanoquinodimethane (PIP–TCNQ), and morpholine-picric acid (MOR–PA). Utilizing piperidine and morpholine as electron donors, picric acid (PA) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as strong organic electron acceptors, this research employs both experimental and computational methods to analyze their electronic structures and stability. Experimentally, equimolar quantities of the donor and acceptor were reacted in chloroform; the resulting precipitates were purified and recrystallized to yield colored crystals. Composition was confirmed via CHN elemental analysis, UV/Vis spectroscopy, and FT-IR spectroscopy, while thermal stability and phase transition behavior were assessed using a Uni-melt capillary melting point apparatus. Theoretically, quantum-chemical calculations were performed using the SE-PM6 method in the Spartan software package. The results indicate linear correlations between experimental melting points and calculated formation enthalpies, heat capacities, dipole moments, and absolute hardness values. Ultimately, this integration of experimental and theoretical approaches elucidates the proton-transfer interactions involved, providing essential insights for the development of advanced organic electronics, such as sensors and high-efficiency solar cells. KEY WORDS: Piperidine, Morpholine, Picric acid, TCNQ, Proton-transfer complex, Experimental approach, Theoretical approach Bull. Chem. Soc. Ethiop. 2026, 40(11), 2305-2317                                 DOI: https://dx.doi.org/10.4314/bcse.v40i11.2