Molecular orbital iodination

The observed femtosecond dynamics of this dissociative CT reaction is related to the nature of bonding. Upon excitation to the CT state, an electron in the highest occupied molecular orbital (HOMO) of benzene (ir) is promoted to the lowest occupied molecular orbital (LUMO) of I2 (a ). Vertical electron attachment of ground state I2 is expected to produce molecular iodine anions in some high vibrational levels below the dissociation limit. In other words, after the electron transfer, the I—I bond is weakened but not yet broken. While vibrating, the entire I2 and benzene complex begins an excursion motion within die coulombic field and the system proceeds... 

In the atom-transfer reactions of iodine from aryl iodides to phenyl radical, intervention of [9-1-2] aryl(phenyl)-A3-iodanyl radicals is proposed [Eq. (86)] [3]. The ab initio molecular orbital study indicates that the diaryl-A3-iodanyl radicals are transition states in the atom-transfer reactions, but not intermediates [161]. Examples obtained by ab initio molecular orbital calculations with the B3LYP/6 - 31G(d) level are shown in Fig. 2. 

Here one of the electrons in the 7r molecular orbitals of the benzene is transferred to the iodine molecule in a molecular orbital of I2. Here we observe an analogy with the -complexes (Pauling, Dewar) as formed from an Ag+ ion... 

In a molecular orbital of this kind, bja always exceeds unity, but the ratio is much larger for fluorine than for iodine, indicating that the charge cloud... 

Both Xe2 and I2 have a vibrational frequency roughly half that of molecular iodine, consistent with the (molecular-orbital based) idea of ahalf bond for the ionic species versus a full bond for molecular iodine. Many other ionic species may be expected to be trapped in matrices and studied in the future by resonance Raman spectroscopy. 

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