Taking Advantage of the Coordinative Behavior of a Tridentate Schiff Base Ligand towards Pd2+ and Cu2+

Abstract

We have explored the suitability of an O,N,N–donor Schiff base (H2SB) for obtaining dinuclear complexes with heavy metal ions such as Cu2+, Zn2+, Ni2+, and Co2+ (borderline acids) as well as Pd2+ and Cd2+ (soft acids). Spectroscopic studies demonstrated that the complexation of H2SB and Cu2+, Zn2+, Ni2+, Co2+, Pd2+, and Cd2+ occurred at a 1:1 stoichiometry. We have found two square planar centers with Pd-N-Pd angles of 93.08(11)° and a Pd–Pd distance of 3.0102(4) Å in Pd2(SB)2·Me2CO. This Pd–Pd distance is 30% shorter than the sum of the van der Waals radii, which is in accordance with a strong palladophilic interaction. Fluorescence studies on H2SB-M2+ interaction showed that H2SB can detect Cu2+ ions in a sample matrix containing various metal ions (hard, soft, or borderline acids) without interference. Determination of binding constants showed that H2SB has a greater affinity for borderline acids than for soft acids.