Investigating the role of the outer-coordination sphere in [Ni(P Ph 2N Ph-R 2) 2] 2+ hydrogenase mimics

Avijita Jain, Matthew L. Reback, Mary Lou Lindstrom, Colleen E. Thogerson, Monte Helm, Aaron Appel, Wendy J. Shaw

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

A series of dipeptide substituted nickel complexes with the general formula, [Ni(P Ph 2N NNA-amino acid/ester 2) 2](BF 4) 2, have been synthesized and characterized (P 2N 2 = 1,5-diaza-3,7- diphosphacyclooctane, and the dipeptide consists of the non-natural amino acid, 3-(4-aminophenyl)propionic acid (NNA), coupled to amino acid/esters = glutamic acid, alanine, lysine, and aspartic acid). Each of these complexes is an active electrocatalyst for H 2 production. The effects of the outer-coordination sphere on the catalytic activity for the production of H 2 were investigated; specifically, the impact of sterics, the ability of the side chain or backbone to protonate and the pK a values of the amino acid side chains were studied by varying the amino acids in the dipeptide. The catalytic rates of the different dipeptide substituted nickel complexes varied by over an order of magnitude. The amino acid derivatives display the fastest rates, while esterification of the terminal carboxylic acids and side chains resulted in a decrease in the catalytic rate by 50-70%, implicating a significant role of protonated sites in the outer-coordination sphere on catalytic activity. For both the amino acid and ester derivatives, the complexes with the largest substituents display the fastest rates, indicating that catalytic activity is not hindered by steric bulk. These studies demonstrate the significant contribution that the outer-coordination sphere can have in tuning the catalytic activity of small molecule hydrogenase mimics.

Original languageEnglish
Pages (from-to)6592-6602
Number of pages11
JournalInorganic Chemistry
Volume51
Issue number12
DOIs
Publication statusPublished - Jun 18 2012

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Hydrogenase
amino acids
Dipeptides
Amino Acids
catalytic activity
Catalyst activity
esters
propionic acid
Esters
Nickel
acids
nickel
Derivatives
aspartic acid
glutamic acid
electrocatalysts
Electrocatalysts
lysine
Esterification
alanine

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry

Cite this

Investigating the role of the outer-coordination sphere in [Ni(P Ph 2N Ph-R 2) 2] 2+ hydrogenase mimics. / Jain, Avijita; Reback, Matthew L.; Lindstrom, Mary Lou; Thogerson, Colleen E.; Helm, Monte; Appel, Aaron; Shaw, Wendy J.

In: Inorganic Chemistry, Vol. 51, No. 12, 18.06.2012, p. 6592-6602.

Research output: Contribution to journalArticle

Jain, Avijita ; Reback, Matthew L. ; Lindstrom, Mary Lou ; Thogerson, Colleen E. ; Helm, Monte ; Appel, Aaron ; Shaw, Wendy J. / Investigating the role of the outer-coordination sphere in [Ni(P Ph 2N Ph-R 2) 2] 2+ hydrogenase mimics. In: Inorganic Chemistry. 2012 ; Vol. 51, No. 12. pp. 6592-6602.
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