Structural, spectroscopic characterization and EPR studies of tetramethylammonium-hydrogen fumarate-fumaric acid complex

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 P2₁/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 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.