Theoretical and Computational Chemistry

Metamorphosis of activated nitrogen to ammonia at metal-free ambient condition: A DFT based inquisition

Authors

  • Ratan Logdi Indian Institute of Science Education and Research, Kolkata ,
  • Arijit Bag Maulana Abul Kalam Azad University of Technology West Bengal ,
  • Ashwani Kumar Tiwari Indian Institute of Science Education and Research Kolkata

Abstract

Activation of N_2 at an ambient condition and reduction to produce ammonia employing metal-free catalyst is one of the grand scientific problems to date. An effective appetite of carbenes towards molecular nitrogen proclaims their candidature as N_2 sequestering agent. However, the sequestering process is associated with a high activation energy barrier. Thus, to ameliorate the use of carbene for the N 2 activation process a Density Functional Theory (DFT) based design is pursued. Through a systematic study, the binding mechanism of the C − N bond between carbene and nitrogen is explored to model efficient carbene. Additionally, Intrinsic Reaction Coordinate (IRC) geometry traping followed by molecular orbital analysis was employed to explore the electronic level reaction mechanism of diazo derivative formation. It is corroborated that in the carbene − N_2 reaction, carbene operates as a σ -acceptor and π-donor where the bonding and the back bonding processes take place before and after the transition state of the reaction. With the aid of this knowledge, a model carbene is designed and computationally tested for nitrogen activation and ammonia formation. It is observed that the model carbene, 6^CN , is an efficient candidate for nitrogen activation and ammonia synthesis in a catalytic way. These results may stimulate future experimental inquisitions.

Content

Thumbnail image of manuscript.pdf

Supplementary material

Thumbnail image of Supporting-chemrxiv.pdf
Ammonia synthesis from molecular nitrogen at the metal-free condition
Employing an appropriate carbene, molecular nitrogen may be sequestered and converted to ammonia in a suitable reduction condition. Carbene acts as a σ -acceptor and π-donor in this process. The electronic level investigation proclaimed that the bonding and the back bonding processes are not instantaneous. These two processes occur at different stages of the reaction. The bonding takes place before reaching the transition state while the back bonding occurs after the transition state which implies that these two processes are independent of each other.