A theoretical study of FeNC in the 6Δ electronic ground state

Ab initio molecular orbital study of ground and low-lying electronic states of NiCN

“…[24] which, unlike the r 0 values, can be derived from the observed spectrum in a straightforward manner. As already discussed at length for FeNC, FeCN, and CoCN in our previous papers [1,2,4], we suspect that the discrepancies between the experimentally derived r 0 values and our rovibrationally averaged, theoretical bond length values are caused by neglect of the effects of large-amplitude bending motion in the experimental determination of r 0 . Further details for e X 2 D NiCN will be given in Ref.…”

“…We have studied ab initio the first-row transition-metalcontaining isocyanide FeNC [1] and the cyanides FeCN [2] and CoCN [3,4] with a view to investigate the effects of the large-amplitude bending motion and the low-spin/highspin issues [3]. These molecules are basically ionic and can be written as M d+ (CN or NC) dÀ .…”

“…For the triatomic molecules FeNC [1], FeCN [2], CoCN [3,4], and for the diatomic CoH [11], we have studied the electronic structure of the ground electronic states. In addition, for CoCN [3] we have also described the low-lying excited states.…”

“…by perturbation methods and, in the case of the triatomic molecules, by means of the MORBID [12][13][14][15] and RENNER [16][17][18][19] variational approaches. The effects of large-amplitude bending motion have been analyzed for each of the triatomic molecules [1,2,4], and these analyses have demonstrated that several published, experimentally derived r 0 bond lengths for these molecules are of limited physical meaning since they were determined with the effects of large-amplitude bending motion being neglected. We suggest that theoretical, rovibrationally averaged bond lengths, obtained from MORBID or RENNER rovibrational wavefunctions, provide a sounder description of the molecular geometry.…”

A theoretical study of FeCN in the 6Δ electronic ground state

“…Thus, in addition to the aim of guiding experimental work on the molecules studied and facilitating the analysis of experimental results, our theoretical studies of metal cyanides and isocyanides acquire a further purpose: To provide accurate structural information, in particular accurate bond length values to supersede the experimentally derived, too-short values. We have already carried out ab initio calculations of structural parameters, rovibronic energies with associated transition intensities, and spectroscopic parameters for the electronic ground states of the first-row transition metal isocyanide FeNC [36] and of the cyanides CoCN [37,38] and NiCN [39]. For 6 D FeCN, our preliminary study mentioned above [22], carried out at the MR-SDCI + Q + E rel /[Wachters + f (Fe), cc-pVTZ (C, N)] level of theory, predicted equilibrium bond length values of r e (Fe-C) = 2.066 Å and r e (C-N) = 1.169 Å .…”