Synthesis and Spectroscopic Characterizations of Tris(hydroxymethyl)aminomethane Proton Transfer Complexes with Acidic π-Acceptors

Abstract

Two charge transfer complexes that are based on an organic basic donor, tris(hydroxymethyl)aminomethane (Tris) and two π-acceptors having acidic protons such as picric acid (PA), and chloroanilic acid (CA) were synthesized for the first time. Some physicochemical analyses including UV-vis, FT-IR and ¹H-NMR were employed to investigate and confirm the proposed chemical structures of the prepared complexes. It was found that the donor–acceptor molar ratio is 1:1 for (Tris):(PA) and 1:2 for (Tris):(CA) charge transfer complexes. The formed charge transfer complexes have –NH₃⁺‏ and –OH²⁺ ions as a result of proton transfer from acidic to basic centers. The formation constant (K_CT) and molar absorptivity coefficient (e_CT) were calculated from the experimental spectroscopic data. Thermodynamic studies for both charge transfer complexes showed the favorability of the complex formation.