All about that base: investigating the role of ligand basicity in pyridyl complexes derived from a copper-Schiff base coordination polymer

Abstract

The role of ligand basicity in complex formation has been investigated using monodentate pyridines or benzimidazole (M) in combination with a solution-stable species derived form a coordination polymer, [Cu(L)] (where L = 2-(2-hydroxybenzylidene-amino)phenol). The 12 [Cu(L)(M)n] complexes generated, combined with the [Cu(L)]2(P) complexes from our previous work (where P is a polypyridyl ligand), allow us to gauge the likelihood of complex formation based on the pKa of the conjugate acid of the pyridyl ligands and Hammett parameter, σ. Above pKa ≈ 4.5, complexes are formed where the only ligands are L2− and M or P and the packing interactions are predominantly van der Waals. Below this value, complex formation is unlikely unless there additional oxygen ligands in the d_(z^2 ) of the Cu(II) ion. The structures of two literature [Cu(L)(B)] complexes, where B is a chelating bidentate pyridyl ligand are also re-examined to resolve the disorder in the [Cu(L)] moiety.

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Identifiers

ORCID for Mateusz Pitak: orcid.org/0000-0002-3680-7100

ORCID for Simon J. Coles: orcid.org/0000-0001-8414-9272

ORCID for Jonathan A Kitchen: orcid.org/0000-0002-7139-5666

ORCID for Tony Keene: orcid.org/0000-0003-2297-4327

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