Molecular ionization energies

Abstract. An isolated individual molecule clearly has only one ionization energy. For ordered molecular assemblies, however, multiple values have been found depending on the orientation of the molecules relative to a supporting substrate. This intriguing observation is rationalized here for the prototypical molecule pentacene, in terms of intrinsic surface dipoles built into the molecules, which collectively give rise to the orientation dependence of the molecular ionization energy. 

For a closed-shell ground-state molecule, those properties that involve only the ground-state wave function can be calculated just as well with either the localized of the delocalized MO description. Such properties include electron probability density, dipole moment, geometry, and heat of formation. Properties of a molecule that involve the wave function of the ground state and also the wave function of an open-shell excited state or the wave function of an open-shell ion cannot be calculated using a localized MO description. Such properties include the electronic absorption spectrum and molecular ionization energies. 

Another recent departure has been the invention of periodic tables designed to summarize the properties of compounds rather than elements. In 1980, Ray Hef-ferlin produced a periodic system for aU the conceivable diatomic molecules that can be formed between the first 118 elements. In order to represent this vast number of entries, Hefferlin used four three-dimensional blocks of varying sizes. His representation reveals that interatomic distances, spectroscopic frequencies, and molecular ionization energies are periodic properties. It also provided successful predictions regarding the properties of diatomic molecules. 

Bis(benzene)molybdenum, in contrast to the chromium analogue, shows a very rich and varied chemistry. It has a very low molecular ionization energy in the... 

Despite the fact that the total electronic energy is not given by the sum of SCF one-electron energies, it is still possible to relate the e, s to physical measurements. If certain assumptions are made, it is possible to equate orbital energies with molecular ionization energies or electron affinities. This identification is related to a theorem due to Koopmans. 

A key fundamental property of small molecules is the IE, which allows thermodynamic properties of neutral species to be derived from those of cations, and vice versa. Only a few actinide molecular ionization energies have been accurately measured by spectroscopic techniques, specifically by Heaven and coworkers lE(UO) = 6.03107 0.00003 eV (Goncharov et al., 2006), 1E(U02)=6.127 0.001 eV (Merritt et al., 2008), lE(ThO)=6.60263 0.00003 eV (Goncharov and Heaven, 2006), and lE(ThF)=6.3952 0.0037 eV (Barker et al., 2012). Mar alo and coworkers have employed electron transfer of actinide cations with neutral species to... 

A Rosen, DE Ellis, H Adachi, EW AveriU. Calculations of molecular ionization energies using a self-consistent-charge Hartree-Eock-Slater method. J Chem Phys 65 3629, 1976. 

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