1033224-28-0Relevant articles and documents
Exploring the Strength of the H-Bond in Synthetic Models for Heme Proteins: The Importance of the N?H Acidity of the Distal Base
Alberti, Mariza N.,Polyhach, Yevhen,Tzirakis, Manolis D.,T?dtli, Laura,Jeschke, Gunnar,Diederich, Fran?ois
, p. 10194 - 10202 (2016)
The distal hydrogen bond (H-bond) in dioxygen-binding proteins is crucial for the discrimination of O2with respect to CO or NO. We report the preparation and characterization of a series of ZnIIporphyrins, with one of three meso-phenyl rings bearing both an alkyl-tethered proximal imidazole ligand and a heterocyclic distal H-bond donor connected by a rigid acetylene spacer. Previously, we had validated the corresponding CoIIcomplexes as synthetic model systems for dioxygen-binding heme proteins and demonstrated the structural requirements for proper distal H-bonding to CoII-bound dioxygen. Here, we systematically vary the H-bond donor ability of the distal heterocycles, as predicted based on pKavalues. The H-bond in the dioxygen adducts of the CoIIporphyrins was directly measured by Q-band Davies-ENDOR spectroscopy. It was shown that the strength of the hyperfine coupling between the dioxygen radical and the distal H-atom increases with enhanced acidity of the H-bond donor.
