Synthesis and anion binding properties of (thio)urea functionalized Ni(II)-salen complexes

• Published in: Dalton transactions : an international journal of inorganic chemistry
• Main Authors: Payong, Jae Elise L, Léonard, Nadia G, Anderson-Sanchez, Lauren M, Ziller, Joseph W, Yang, Jenny Y
• Format: Journal Article
• Language: English
• Published: England 01.11.2024
• ISSN: 1477-9226; 1477-9234; 1477-9234
• DOI: 10.1039/d4dt02683g

Salen ligands (salen = , '-ethylenebis(salicylimine)) are well-known for their versatility and widespread utility in chelating metal complexes. However, installation of hydrogen-bonding units on the salen framework, particularly functional groups that require amine-based precursors such as (thio)ureas, is difficult to achieve without the use of protecting group strategies. In this report, we show that the phenylketone analog of salicyladehyde is a stable alternative that enables the facile installation of hydrogen bonding (thio)urea groups on the salen scaffold, thus imparting anion binding abilities to a metal salen complex. Synthesis of symmetric -phenyl(thio)urea salen ligands functionalized at the 3,3'-position and an unsymmetric salen ligand with -phenylurea at the 5-position was achieved. Subsequent metalation with nickel(II) acetate afforded the nickel(II) complexes that were investigated for their anion binding properties towards F , Cl , Br , CH COO , and H PO . Solid-state structures of the nickel(II) complexes as well as the Cl bound dimer of the symmetric urea complex were obtained. The unusual acidity of the (thio)urea groups is reflected in the p -dependent anion binding behavior of the nickel(II) complexes, as elucidated by H and F Nuclear Magnetic Resonance (NMR) spectroscopy and Diffusion Ordered Spectroscopy (DOSY) experiments.