The Electron Paramagnetic Resonance of Triplet CNN, NCN, and NCCCN

Abstract

We wish to report the observation, by electron paramagnetic resonance, of the ground-state triplets diazomethylene, :C=N+=N-(I); cyanonitrene, N=C-N (II); and dicyanomethylene, N=C-C-C=N (III).

Dicyanocarbene and Its Isomers: A Matrix Spectroscopic Study

“…Our DFT calculations confirmed the earlier prediction [12,15] that a triplet ground state ( 3 Σ g Ϫ ) has to be expected for dicyanocarbene (5). The geometry of T-5 should be linear (Scheme 1).…”

“…[9] Dicyanocarbene (5) has a similar history to the monocyano derivative. Wasserman et al [12] recorded the ESR spectrum of T-5 as far back as 1965, although in light of the results presented below it is astonishing that T-5 is claimed [12] to be the only triplet molecule formed upon irradiation of dicyanodiazomethane (4). Perhaps a more detailed ESR study could clarify the situation.…”

“…Since the calculated ϽS 2 Ͼ value of this singlet molecule amounts to 1.03 this species lies just in the middle between a pure singlet (ϽS 2 Ͼ ϭ 0) and a triplet (ϽS 2 Ͼ ϭ 2). If we believe Wasserman's [12] claim that the experimental ESR data can be taken as proof of the triplet ground state of 5, a structural elucidation based on a comparison of the IR spectra is not really needed. Therefore, we did not carry out a more appropriate theoretical treatment of S-5 by using multi-configuration calculations.…”

“…[14] Several calculational studies have also been published. [12,15] All theoretical treatments have agreed so far that dicyanocarbene possesses a triplet ground state, but the predictions for the geometry of T-5 differ. In combination with our work on monocyanocarbene (1), [9] and with regard to the still existing inconsistencies in the experimental and theoretical studies on T-5, we decided to study 5 in more detail.…”

Intrinsic Dinitrogen Activation at Bare Metal Atoms

“…CNN is less stable than NCN. [83,84] Co 2 D electronic ground state. Observed in matrix-isolation studies.…”