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

Two charge transfer complexes based on an organic basic donor, tris(hydroxymethyl)- aminomethane (Tris), and two π-acceptors having acidic protons, 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 –NH^+3 and –OH^+2 ions as a result of proton transfer from acidic to basic centers. The formation constant (KCT) and molar absorptivity coefficient (εCT) were calculated from the experimental spectroscopic data. Thermodynamic studies for both charge transfer complexes showed the favorability of the complex formation.