Synthesis, crystal structure and properties of tris(2-hydroxypropyl)ammonium based protic ionic liquids and protic molten salts

Fifteen tris(2-hydroxypropyl)ammonium salts (TPA salts) were first synthesized by a direct reaction of proton transfer from carboxylic acids to tris(2-hydroxypropyl)amine. The composition and structure of synthesized TPA salts were confirmed by NMR (1H, 13C), FT-IR spectroscopy and elemental analysis. The crystal structure and conformation of the tris(2-hydroxypropyl)ammonium cation in salts of salicylic, nicotinic and malonic acids were studied by single-crystal X-ray diffraction. Thermal stability studies have shown that TPA salts are protic ionic liquids with melting temperatures below 100 °C or room-temperature ionic liquids or molten salts. Selected TPA salts were investigated for their antimicrobial activity against bacterial and fungus strains. In addition, it was shown for the first time that synthesized TPA salts can be used as potential buffer agents for 68Ga-radiolabeling of bifunctional chelating agents (BCA) and clinically relevant peptides (PSMA-11, PSMA-617, DOTA-NOC, DOTA-TATE). [Display omitted] •Tris(2-hydroxypropyl)ammonium salts were synthesized and characterized.•TPA cations are characterized by endo- or endo-exo-conformations.•Decomposition temperatures of TPA salts vary in the range of 122–182 °C.•Antimicrobial activity depends significantly on the nature of hydroxyalkylamine.•[TPA]Cl-Crez is the most optimal buffer for 68Ga-radiolabeling reactions.