Dioxygen molecular orbitals

Dioxygen activation in transition metal complexes in the light of molecular orbital calculations. R. Boca, Coord. Chem. Rev., 1983, 50,1-72 (245). 

As can be seen from its ground-state molecular orbital diagram in Figure 4.11, dioxygen has a paramagnetic ground state. It is the only stable homonuclear diatomic molecule with this property. 

Dioxolane synthesis, 192-273 fused bicyclic dioxolanes, 193, 194 Dioxygenation, stereoselective, 339-48 Dioxymethane, molecular orbital treatment, 28-9... 

Fig. 1 Qualitative molecular orbital diagrams for the alkene fragment of benzoquinone and dioxygen highlighting the key differences in their respective frontier orbitals...

Defined as N = (n - n )/2, where n and n are the numbers of electrons in the bonding and antibonding molecular orbitals, respectively, of the corresponding dioxygen species. e R = alkyl. 

Fig. 5. A restricted molecular orbital description of the essential spin pairing interaction involved in dioxygen binding to a cobalt (Il)-base (B) adduct. Reprinted with permission from Ref. 48. Copyright 1976 American Chemical Society.

Translational symmetry. 74 Translawrencium elements, periodicity of. 615-617 Transport, dioxygen, 895-910 Triatomic molecules and ions, molecular orbitals in, 175-182... 

Figure t The molecular orbital diagram for the dioxygen molecule... 

The quantum mechanical methods described in this book are all molecular orbital (MO) methods, or oriented toward the molecular orbital approach ab initio and semiempirical methods use the MO method, and density functional methods are oriented toward the MO approach. There is another approach to applying the Schrodinger equation to chemistry, namely the valence bond method. Basically the MO method allows atomic orbitals to interact to create the molecular orbitals of a molecule, and does not focus on individual bonds as shown in conventional structural formulas. The VB method, on the other hand, takes the molecule, mathematically, as a sum (linear combination) of structures each of which corresponds to a structural formula with a certain pairing of electrons [16]. The MO method explains in a relatively simple way phenomena that can be understood only with difficulty using the VB method, like the triplet nature of dioxygen or the fact that benzene is aromatic but cyclobutadiene is not [17]. With the application of computers to quantum chemistry the MO method almost eclipsed the VB approach, but the latter has in recent years made a limited comeback [18],... 

Molecular orbital theory predicts that O2 is paramagnetic, in agreement with experiment. Note that the Lewis structure of O2 does not indicate that it has two unpaired electrons, even through it does imply the presence of a double bond. In fact, the prediction/confirmation of paramagnetism in O2 was one of the early successes of molecular orbital theory. Also, the ions 0+ (dioxygen cation), Oj (superoxide anion), and 0 (peroxide anion) have bond orders 2V2, U/2, and 1, respectively. The experimental energy levels of the molecular orbital for the O2 molecule are shown in Fig. 3.3.3(b). 

Molecular oxygen (or dioxygen) O2 and related species are involved in many chemical reactions. The valence molecular orbitals and electronic configurations of the homonuclear diatomic species O2 and Oj are shown in Fig. 16.1.1. 

As predicted by molecular orbital theory dioxygen has two unpaired electrons and some of its chemistry shows diradical characteristics in particular, it reacts readily with other radicals. Singlet oxygen is an excited state in which the two electrons in the p anti-bonding orbitals have paired spins. It produced in some chemical reactions and has different chemical reactivity. 

The bond orders for ground-state molecular oxygen (dioxygen, 02), for superoxide ion (02 -), and for (HOOH) are 2, 1.5, and 1, respectively. Tabled provides molecular orbital diagrams for dioxygen ( g , Ag, and g+) and superoxide ion, which illustrates the biradical character of 62 (-02-) and the delocalized spin density of 02 - (one-half spin per oxygen). 

Most recent authors have discussed the bonding in dioxygen complexes in terms of molecular orbital theory. Thus Drago in his spin-pairing model for 77 complexes of cobalt proposes a M.O. diagram arising fi om the interaction of one jtg orbital of dioxy-... 

Figure 11.2. Molecular orbital diagrams for O2 and O2. The ground state normal O2 (dioxygen) = triplet ground state) has two unpaired ir-electrons (it is a biradical) and is paramagnetic. Two excited forms of singlet oxygen O2 ( A and E ) can be generated (often by light irradiation in the presence of a sensitizer). The first product in a one-electron reduction of oxygen is the superoxide ) anion. (Adapted from Sawyer, 1991.)...

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