Spin trapping by bis(benzene)chromium: A density functional study

Abstract

Bis(benzene)chromium [(Z 6 -C 6 H 6 ) 2 Cr] (BBC) was shown to trap radical species R (R ¼ H, isobutyronitrile (IBN)) to form complex paramagnetic adducts whose structure was characterized in frozen solution by electron nuclear double resonance (ENDOR) spectroscopy. It has been shown that radical attack yields the 17 valence species (Z 6 -C 6 H 6 )(Z 5 -C 6 H 6 R)Cr where R assumes the endo position of the Z 5 ring. To prove the existence of such a mechanism, a density functional study of BBC and corresponding adducts has been carried out. Geometry optimisations of these molecules have been performed at the PBE0 level with an effective core potential for chromium and 6-31G(d) basis sets on carbons and hydrogens. The calculated hyperfine coupling constants of hydrogen nuclei of the obtained structure are in excellent agreement with experimental values, thus proving the formation of the ring-protonated adducts.

One-Photon Mass-Analyzed Threshold Ionization Spectroscopy of Bis(η6-benzene)chromium and Its Benzene and Ar Clusters

“…The strong MATI origin band in Figure suggests that the difference in the Cr−benzene distance is rather small between the neutral and ionized forms. These experimental observations are consistent with the electronic nature of the ionization of Cr(C 6 H 6 ) 2 , the removal of an electron in the nonbonding d-orbital of Cr. − And also, the experiment is consistent with the theoretical prediction that the Cr−ring distance remains constant in the ionization of Cr(C 6 H 6 ) 2 . , It is interesting to note that the ν 21 vibrational frequency (263 cm -1 ) in the 3d z 2 −R4p x,y Rydberg transition 12,13 is almost identical to that in the cationic ground state.

1 The MATI spectrum of bis(η 6 -benzene)chromium.

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“…[9][10][11] And also, the experiment is consistent with the theoretical prediction that the Cr-ring distance remains constant in the ionization of Cr(C 6 H 6 ) 2 . 6,8 It is interesting to note that the ν 21 vibrational frequency (263 cm -1 ) in the 3d z 2 -R4p x,y Rydberg transition 12,13 is almost identical to that in the cationic ground state.…”

“…And also, its high symmetry of D 6h makes this relatively large molecule a good model for many kinds of quantum mechanical calculations. [6][7][8] Laser spectroscopy and dynamics of bis(η 6 -benzene)chromium in the molecular beam have also been extensively investigated because of its intriguing dynamic simplicity despite of its intrinsic complexity as a large chemical system. [9][10][11][12][13] Ionization dynamics of Cr(C 6 H 6 ) 2 has got special attention because many high n-Rydberg states are readily accessible by the UV laser source.…”

In situ formation and electron-spectroscopic study of bis(arene) V and Cr compounds on a graphite surface

“…It should be noted, however, that recent theoretical work 13 suggests that it is the overlap of the bis(arene)TM HOMO with the graphene p orbitals, and not simply the AIP, that is critical in electron transfer. 36 The relative intensities and BEs computed for VBz 2 (not shown), which is isoelectronic with [CrBz 2 ] þ , are very similar to those in Fig. The CrBz 2 coverage in Fig.…”

A computational study of organic polyradicals stabilized by chromium atoms

“…A similarly bent benzene ring has been reported for the Bis(benzene)chromium (BBC) radical 62,63 obtained from addition of organic radicals to BBC. BBC is an efficient organometallic spin scavenger 62 and both theory and experiment assign the extra spin to the chromium atom.…”