Determination of acid-base constants in amphiprotic nonaqueous solvents by direct potentiometry

Novel Bispidine Ligands and Their First-Row Transition Metal Complexes: Trigonal Bipyramidal and Trigonal Prismatic Geometries

“…For electrochemical measurements a BAS-100B workstation was used, with a three-electrode setup, consisting of a glassy carbon working, a Pt-wire auxiliary, and, for MeCN solutions, an Ag/AgNO 3 reference electrode (0.01 M AgNO 3 , 0.1 M (Bu 4 N)(PF 6 ), degassed CH 3 CN), solutions of the complexes in MeCN/0.1 M (Bu 4 N)(PF 6 ); for H 2 O solutions, an Ag/AgCl reference electrode (3 M NaCl, degassed and deionized H 2 O), solutions of the complexes in H 2 O, 0.1 M KNO 3 ; the potential of the Fc + /Fc-couple for the MeCN setup had a value of +91 mV (MeCN, scan rate of 100 mV/s); the potential of the Fc + /Fc-couple for the H 2 O setup had a value of +195 mV, (H 2 O, scan rate of 100 mV/s). Potentiometric titrations were performed on 20 mL of samples (0.1 M KCl for p K a values, 0.2 M NaClO 4 for complex stabilities, 0.1 mol/L of the respective metal ion, 0.1 mol/L ligand) in various dioxane-water mixtures (50%, 55%, 60%), − T = 298 K; HCl was used to adjust the initial pH for p K a titration, HClO 4 for complex stabilities; 0.1 mol/L KOH (CO 2 -free, titration with potassium hydrogen phthalate); all solutions were kept under Ar. The measurements were done with a pH meter equipped with a 6.0202.100 combined electrode (Metrohm), a 665 Dosimat automatic buret (Metrohm).…”

Local anesthetic-membrane interaction: a multiequilibrium model.

“…Their local anesthetic properties were determined by studies on squid giant axons (22). These compounds were effective as local anesthetics .at concentrations of l0-5 to 5 X 10-5 M. The pK of both C2SL and C4SL (the ethoxy and butoxy analog of the local anesthetic spin labels used in this experiment) were found to be between 7.2 and 7.4 by the procedures described by Tencheva et al (29). The C6SL itself was.…”