Thiacrown chemistry: VI. Synthesis of chromogenic thiacrown and their coordination

Four new chromogenic thiacrowns bearing 7-aza-1, 4, 10, 13-tetrathiacyclohexadecane were successfully synthesized. The acid dissociation constants of chromogenic thiacrowns 3 and 4 were determined: pKa = 8.68(3); pKa1 = 8.49, pKa2 = 12.12(4). Their coordination to transitional metal cations were spectrophotometrically studied.