title: Comparison and analysis of zinc and cobalt-based systems as catalytic entities for the hydration of carbon dioxide.
abstract: In nature, the zinc metalloenzyme carbonic anhydrase II (CAII) efficiently catalyzes the conversion of carbon dioxide (CO2) to bicarbonate under physiological conditions. Many research efforts have been directed towards the development of small molecule mimetics that can facilitate this process and thus have a beneficial environmental impact, but these efforts have met very limited success. Herein, we undertook quantum mechanical calculations of four mimetics, 1,5,9-triazacyclododedacane, 1,4,7,10-tetraazacyclododedacane, tris(4,5-dimethyl-2-imidazolyl)phosphine, and tris(2-benzimidazolylmethyl)amine, in their complexed form either with the Zn(2+) or the Co(2+) ion and studied their reaction coordinate for CO2 hydration. These calculations demonstrated that the ability of the complex to maintain a tetrahedral geometry and bind bicarbonate in a unidentate manner were vital for the hydration reaction to proceed favorably. Furthermore, these calculations show that the catalytic activity of the examined zinc complexes was insensitive to coordination states for zinc, while coordination states above four were found to have an unfavorable effect on product release for the cobalt counterparts.
authors.affiliation: Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, USA.
authors.forename: Edmond Y
authors.initials: EY
authors.lastname: Lau
authors.forename: Sergio E
authors.initials: SE
authors.lastname: Wong
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Baker
authors.forename: Jane P
authors.initials: JP
authors.lastname: Bearinger
authors.forename: Lucas
authors.initials: L
authors.lastname: Koziol
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Valdez
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Satcher
authors.forename: Roger D
authors.initials: RD
authors.lastname: Aines
authors.forename: Felice C
authors.initials: FC
authors.lastname: Lightstone
mesh_terms: D001372:Aza Compounds / Q000737:chemistry*; D001639:Bicarbonates / Q000138:chemical synthesis*; D032701:Biomimetics; D002245:Carbon Dioxide / Q000737:chemistry*; D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry; D013816:Thermodynamics; D014867:Water / Q000737:chemistry; D015032:Zinc / Q000737:chemistry*
chemical_list: D001372:Aza Compounds; D001639:Bicarbonates; D056831:Coordination Complexes; D006571:Heterocyclic Compounds; D012997:Solvents; D014867:Water; D002245:Carbon Dioxide; D003035:Cobalt; D015032:Zinc