DFT prediction of multitopic N-heterocyclic carbenes using Clar's aromatic sextet theory

Cherumuttathu H. Suresh*, Manjaly J. Ajitha

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Existence of several multitopic N-heterocyclic carbene (NHC) ligands with up to four carbene centers have been predicted on the basis of Clar's aromatic sextet theory. Assessment on stability and reactivity of NHCs was made by quantifying aromaticity, aromatic stabilization energy (Earoma), strength of carbene lone pair, proton affinity, and CuCl binding energy. On NICS(0) and HOMA scales of aromaticity, several NHCs showed high aromaticity, while Earoma (17.2-19.4 kcal/mol) indicated substantial stability for the N-heterocycle. Homodesmotic reactions suggested that heat of formation of most of the newly designed carbenes is very close to that of the existing bis-NHCs. Designing a multitopic ligand through branching via Csp3 linkage was very effective as it improved the stability of the carbene. Electrostatic potential minimum (Vmin) at the carbene lone pair suggested that annelation of heterocycle to a benzenoid ring or branching through Csp3 linkage can only marginally influence the electron donating power of the ligand. Hence, all multitopic NHCs showed proton affinity (252.3-267.4 kcal/mol) and CuCl binding energy (62.9-66.6 kcal/mol) very close to those of 1,3-dimethylimidazolidine-2-ylidene (1). It has also been demonstrated that branched multitopic 3-dimensional NHCs are attractive for designing metal-organic framework with narrow (1-1.5 nm) cage/pore size.

Original languageEnglish (US)
Pages (from-to)3918-3924
Number of pages7
JournalJournal of Organic Chemistry
Issue number8
StatePublished - Apr 19 2013

ASJC Scopus subject areas

  • Organic Chemistry


Dive into the research topics of 'DFT prediction of multitopic N-heterocyclic carbenes using Clar's aromatic sextet theory'. Together they form a unique fingerprint.

Cite this