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Switching of carbene spin states: effect of hydrogen bond donors

Authors Guha AK, Boruah A, Hazarika M, Kaman S

Received 23 February 2015

Accepted for publication 28 April 2015

Published 20 July 2015 Volume 2015:3 Pages 1—6


Checked for plagiarism Yes

Review by Single-blind

Peer reviewer comments 4

Editor who approved publication: Dr Jorge Llano

Ankur Kanti Guha,1 Abhijit Boruah,2 Munmi Hazarika,2 Sumi Kaman2

1Department of Chemistry, Cotton College State University, Guwahati, Assam, India; 2Department of Chemistry, Dibrugarh University, Dibrugarh, Assam, India

Abstract: Quantum chemical calculations predict that the spin states of simple carbenes can be switched over from triplet to singlet via hydrogen bonding, and thus the spin specificity of their reactions can be tuned. The stability of the singlet state of simple carbenes like: CH2 increases due to hydrogen bond formation with a single molecule of water or methanol, although the triplet state is found to be the ground state. However, the most dramatic effect of spin switch is found for diphenylcarbene (Ph2C), which becomes a ground state singlet due to formation of a hydrogen bond with the hydrogen atom of water or methanol. The present calculations reveal that the effect of hydrogen bonds on switching the spin state of carbenes is only applicable to Ph2C, as it has a very small singlet–triplet gap in its free form, ie, when it is not hydrogen bonded with water or methanol. Further, the presence of such hydrogen-bonding interaction has been verified within the realm of atoms-in-molecules analysis of the electron density.

Keywords: carbenes, spin states, quantum chemical calculations, hydrogen bonding, atoms in molecules

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