Protolytic and Complexing Properties of Isomeric N-(Pyridylethyl)taurines

New N-derivatives of taurine, N-[2-(2-pyridyl)ethyl]taurine (HL1) and N-[2-(4-pyridyl)ethyl]taurine (HL2) have been synthesized. Using the method of alkalimetric titration of aqueous solutions with pH potentiometric indication at I = 0.1 mol/L (KCl/KNO3) and T = 25 ± 1°C, the acid dissociation constants of functional groups in the composition of reagents have been determined (HL1: pKa0 = 3.80 ± 0.03, pKa1 = 8.67 ± 0.02, HL2: pKa0 = 4.80 ± 0.05, pKa1 = 8.18 ± 0.04). It has been found that reagent HL1 is more resistant to the degradation process. The complexation of transition and alkaline earth metal ions with НL1 has been studied. It has been shown that the introduction of a 2-(2-pyridyl)ethyl substituent into the structure of taurine leads to a significant increase in the stability (Δ log β ≥ 1) of copper(II), cobalt(II), nickel(II), zinc(II), cadmium(II) and silver(I) complexes with НL1. Calcium(II), magnesium(II), strontium(II), and barium(II) complexes with HL1 are characterized by a slight increase in stability (Δ lg β < 1) compared to taurine. Based on the data obtained, the structure of the studied complexes have been assumed.