Tripodal ligand incorporating dual fluorescent ionophore: a coordinative control of photoinduced electron transfer

Abstract

p-(N,N-Dimethylamino)benzenesulfonamide (DMABSA), a dual fluorescent fluorophore, has been derivatized into two new fluoroionophores for transition metal cations. The electron-acceptor sulfonamide group has been N-substituted by a 2-pyridylmethylene group to lead to a bidentate ligand which forms a 2:1 complex with Cu(II). The crystal structure of the copper(II) complex is reported. The Cu(II) is coordinated through the pyridine N- and sulfonamide N-deprotonated atom which account for the blue-shift of the absorption and the partly quenched fluorescence. When DMABSA was incorporated into the tris(2-aminoethyl)amine (tren), a tripodal, dual-fluorescent ligand, is obtained which shows higher binding affinity for Zn(II) than for Cu(II). Furthermore, the large increase of the short wavelength emission and the disappearance of the TICT emission, upon Zn complexation, allow measurements of the Zn(II) concentration from relative fluorescence intensity at two wavelengths.