Structural, spectroscopic characterization and EPR studies of tetramethylammonium-hydrogen fumarate–fumaric acid complex Original Research Article

The tetramethylammonium-hydrogen fumarate–fumaric acid (hereafter, [TMAHF–FA]) complex was synthesized and characterized by spectroscopic (IR), structural (XRD) and electron paramagnetic resonance (EPR) techniques. In the crystal structure, tetramethylammonium cation lies on a mirror plane of the space group P 21/m. Crystal structure analysis reveals that there is a large degree of proton sharing between the fumaric acid and hydrogen fumarate, with the H atom lying almost symmetrically between the donor and acceptor sites, as evidenced by the long O–H and short H⋯O distances [1.19(3) Å, 1.26(3) Å], respectively. γ-Irradiation damage centers in [TMAHF–FA] single crystal have been investigated by EPR at room temperature. The spectra indicated the existence of View the MathML sourceC˙αHαCβHβCOO- radical. The EPR spectra recorded in the three mutually perpendicular planes have shown two magnetically distinct paramagnetic sites in monoclinic lattice. The principal values of g and hyperfine constants for both sites were calculated. IR spectrum was resolved and transitions were assigned based on the molecular structure.