Ground state molecular orbital schemes

AsPh4]2[Mo S2C2(CN)2 3] was fitted by an axially symmetric spin Hamiltonian with g, = 2.000, g l = 1.974, Att = 10 G and AL = -100 G, interpreted in terms of a 1A1 ground state in D3 symmetry.49 The unpaired electron has predominantly metal dzi character. A molecular orbital scheme (Figure 4) was proposed for the dithiolene complexes.35 This scheme has been used in the discussion of ESR results,49 and electronic and resonance-Raman spectra.34... 

In terms of the molecular orbital scheme presented (for FeF) in figure 10.89, the ground electronic state of MnO may be approximated by the single configuration,... 

Figure 2. Molecular orbital schemes and ground states of MCO molecules (M first-row transition metal). Boxes here emphasize the only molecules with ej erimentally established ground states. Ground states are indicated as theoretically calculated (T) ej5>eri men tally determined (E) or suggested ( ), based on absence of an ESR spectrum.

Sandstrom et al. (65) evaluated the Kj value for 4,5-dimethyl-A-4-thiazoline-2-thione (46) in water (Scheme 19) K-j= 10. A-4-Thiazoline-2-thiones are less basic in the first excited state (61) than in the ground state, so application of Forster s cycle suggests that the thione form is even more favored in the first excited state. Huckel molecular orbital (HMO) calculations suggest that electronic effects due to substitution in... 

The bands due to Fe(CO)4 are shown in Fig. 8. This spectrum (68) was particularly important because it showed that in the gas phase Fe(CO)4 had at least two vq—o vibrations. Although metal carbonyls have broad vC—o absorptions in the gas phase, much more overlapped than in solution or in a matrix, the presence of the two Vc—o bands of Fe(CO)4 was clear. These two bands show that in the gas phase Fe(CO)4 has a distorted non-tetrahedral structure. The frequencies of these bands were close to those of Fe(CO)4 isolated in a Ne matrix at 4 K (86). Previous matrix, isolation experiments (15) (see Section I,A) has shown that Fe(CO)4 in the matrix had a distorted C2v structure (Scheme 1) and a paramagnetic ground state. This conclusion has since been supported by both approximate (17,18) and ab initio (19) molecular orbital calculations for Fe(CO)4 with a 3B2 ground state. The observation of a distorted structure for Fe(CO)4 in the gas phase proved that the distortion of matrix-isolated Fe(CO)4 was not an artifact introduced by the solid state. 

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