title: Design of Carbene-Based Organocatalysts for Nitrogen Fixation: Theoretical Study.
abstract: Nitrogen fixation is a great challenge in solving the food supply of mankind. However N2 activation is extremely hard. Up until recently, the investigated catalysts for N2 fixation were based on metallic reducing agents. They are generally not environment friendly. We designed organocatalysts (carbenes) for nitrogen fixation using density functional theory (DFT) and ab initio theory. The reactivity of the carbene catalysts is mainly related to the electrostatic properties of the side chains. We compared the binding affinity to N2 with various carbenes (:CF2, :CCl2, :CBr2, and :CI2). We revealed that the electron donating ability of the central carbene carbon is the most important factor for trapping N2. Among heterocyclic carbenes, the cyclic diphospinocarbenes (PHC) represented a good candidate moiety for an efficient catalyst. We further designed the carbene based catalyst which has two carbene moieties to chelate N2 and investigated the whole catalytic mechanism. The highest energy barrier of the entire catalytic cycle is 28.5 kcal/mol, which is comparable to the previously reported metallic catalysts. This demonstrates the possibility of novel organic catalysts for nitrogen fixation.
authors.affiliation: Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea.
authors.forename: Sung-Woo
authors.initials: SW
authors.lastname: Park
authors.affiliation: Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea.
authors.forename: Young
authors.initials: Y
authors.lastname: Chun
authors.affiliation: Department of Cellular Molecular Medicine, College of Medicine, Chosun University, Gwangju 501-759, Republic of Korea.
authors.forename: Seung Joo
authors.initials: SJ
authors.lastname: Cho
authors.affiliation: Department of Applied Chemistry, School of Applied Sciences, Kyung Hee University, Kyungki-Do 446-701, Korea.
authors.forename: Sungyul
authors.initials: S
authors.lastname: Lee
authors.affiliation: Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea.
authors.forename: Kwang S
authors.initials: KS
authors.lastname: Kim