Mark A. W. Lawrence

The ability of six pincer type molecules (di‐2‐pyridyl ketone acetic acid hydrazone ( 1 ), N ‐(2,5‐dimethoxyphenyl)‐6‐[(2,5‐dimethoxyphenyl)carbamothioyl]pyridine‐2‐carboxamide ( 2 ), 6‐(4,7‐dimethoxy‐2‐benzothiazolyl)‐ N ‐(2,5‐dimethoxyphenyl)‐2‐pyridinecarboxamide ( 3 ), di‐2‐pyridyl ketone thiosemicarbazone ( 4 ), bis‐ N ‐(2,5‐dimethoxyphenyl)pyridine‐2,6‐dicarbothioamide ( 5 ), and 6‐(4,7‐dimethoxy‐2‐benzothiazolyl)‐ N ‐(2,5‐dimethoxyphenyl)‐2‐pyridinecarbothioamide ( 6 )), to detect MBr 2 (where M=Co, Ni, and Cu) in DMSO was quantified via formation constants determined from spectrophotometric and voltammetric titrations. The limit of detection (from electronic spectroscopy) of 1 – 6 ranged from 0.9‐9.5 ppm. The values of β (=log K ) for the six species were found to be in the ranges of 4.3–4.9 and 4.0–6.3 for Co(II), 3.9–5.5 and 3.5–4.3 for Ni(II), and 4.0–4.3 and 3.7–5.0 for Cu(II) by UV‐visible and voltammetric methods, respectively. The results suggested that κ 3 ‐NNS ( 6 ) and the κ 3 ‐NNO ( 3 ) had good affinity for Ni(II) and Cu(II), whereas the κ 3 ‐SNS ( 5 ) had greater affinities for Co(II) and Ni(II). The hydrazones (κ 3 ‐NNO, 1 and κ 3 ‐NNS, 4 ) were generally in the middle of the pack, displaying good affinity for the three metal ions. In a contrasting vein, the κ 3 ‐ONS species ( 2 ) was generally the lowest across the pincers. DFT calculations (PBE0/6‐31G(d,p)/SMD) suggested that stable complexes of coordination numbers=4 to 6 were plausible in solution.