@Article{D0NJ02347G,
author ="Oloyede, Hammed Olawale and Woods, Joseph Anthony Orighomisan and Görls, Helmar and Plass, Winfried and Eseola, Abiodun Omokehinde",
title  ="New cobalt(ii) coordination designs and the influence of varying chelate characters{,} ligand charges and incorporated group I metal ions on enzyme-like oxidative coupling activity",
journal  ="New J. Chem.",
year  ="2020",
volume  ="44",
issue  ="35",
pages  ="14849-14858",
publisher  ="The Royal Society of Chemistry",
doi  ="10.1039/D0NJ02347G",
url  ="http://dx.doi.org/10.1039/D0NJ02347G",
abstract  ="In transition-metal-mediated catalysis{,} designing new{,} well defined coordination architectures and subjecting them to catalysis testing under the same reaction conditions is a necessary tool for gaining an improved understanding of desirable active site geometries and characteristics. In this work{,} three ligands varying in chelation and charge characters (1 = tridentate{,} dianionic N^N^N; 2 = bidentate{,} dianionic N^N; 3 = bidentate{,} neutral N^O) were synthesized and introduced as organic backbones around cobalt(ii) centres. Four multinuclear coordination assemblies incorporating various group I metal ions (i.e.{,} (Na-Co1-i)2{,} (Na-Co1-e)2{,} (K-Co1-e)2 and (Cs-Co1-e)2) and two mononuclear complexes (i.e.{,} Co2 and Co3) were isolated{,} structurally characterized and studied as phenoxazinone synthase models. X-ray data and Continuous Shape Measure (CShM) calculations described unusual vacant trigonal bipyramidal geometries for (Na-Co1-i)2{,} (Na-Co1-e)2 and Co3{,} trigonal bipyramids for (K-Co1-e)2 and (Cs-Co1-e)2{,} and a tetrahedron for Co2. According to mass spectrometry data{,} the four multinuclear (MI-Co1-solvate)2 complexes of ligand 1 easily dissociate in solution to yield the corresponding ions including a common mononuclear Co1 unit. Testing as models in the oxidative coupling of o-aminophenol revealed that an increasing chelate character of the organic ligand backbone produces an undesirable catalyst activity reduction. Furthermore{,} the similarity in coupling efficiencies observed among complexes (Na-Co1-i)2{,} (Na-Co1-e)2{,} (K-Co1-e)2 and (Cs-Co1-e)2 proves that the presence of varying group I metal ions contributed no catalytic effects to the coupling efficiencies and that the Co1 species{,} which is generated by dissociation in solution{,} is the only active species responsible for the observed biomimetic behaviours. Therefore{,} the combination of anionic chelate ligands with easily detachable{,} neutral co-ligands (e.g.{,} water or pyridine) around a cobalt(ii) centre could be recommended for the generation of a successful catalyst material{,} rather than the combination of a neutral chelate ligand with counter-anionic monodentate co-ligands like halides."}