Ionization potential electron affinity, relationship between

COSMO), ionization potential, electron affinity, logP, Phomo> lumo> 7> X> cd, and molecular weight (not determined by calculation) are listed in Table 3. Using these values, whether there are any relationships between CC50 and each of these descriptors was investigated (Fig. 7). 

When parameters of the Pariser-Parr-Pople configuration interaction molecular orbital (PPP-CI MO) method were modified so as to reproduce the Aol)s values for l,3-di(5-aryl-l,3,4-oxadiazol-2-yl)benzenes 16 and 17, the calculated HOMO and LUMO energy levels corresponded with the experimental ionization potential and electron affinity values. The relationships between the electrical properties and molecular structures for the dyes were investigated. The absorption maximum wavelengths for amorphous films were found to be nearly equal to those for solution samples <1997PCA2350>. 

Quantitative structure-physical property relationships (QSPR). There are two types of physical properties we must consider ground state properties and properties which depend on the difference in energy between the ground state and an excited state. Examples of the former are bond lengths, bond angles and dipole moments. The latter include infrared, ultraviolet, nuclear magnetic resonance and other types of spectra, ionization potentials and electron affinities. 

In the gas phase, homolytic bond dissociation enthalpies (D//) relate the thermochemical properties of molecules to those of radicals while ionization potentials (IP) and electron affinities (EA) tie the thermochemistry of neutral species to those of their corresponding ions. For example, Scheme 2.1 represents the relationships between RsSiH and its related radicals, ions, and radical ions. This representation does not define thermodynamic cycles (the H fragment is not explicitly considered) but it is rather a thermochemical mnemonic that affords a simple way of establishing the experimental data required to obtain a chosen thermochemical property. 

We reported the relationships between the NMR chemical shifts and the rate constants of acylation (k) as well as such electronic-property-related parameters as ionization potential (IP), electronic affinity (EA), and molecular orbital energy for a series of aromatic diamines and aromatic dianhydrides. " The usefulness of... 

Fig. 8.21 Relationship between the oxidation potential (E0x)> the reduction potential (ERed), the ionization potential (IP), the electron affinity (EA), and the solvation energies (AG°V+,...

This second approach has the added benefit or calling attention to the very dose relationship between electron affinity and ionization potential. In fact, when the ionization energies and electron affinities of atoms are plotted, a smooth curve results and the function may be described rather accurately by the quadratic formula 30... 

Anderson and Hinthorne [31] have determined that for positive secondary ions an element s secondary ion yield is inversely proportional to the first ionization potential of an element. A similar relationship has been established between negative secondary ion yields and electron affinities [4,31,32],... 

Figure 2.15 Schematic orbital diagram illustrating the relationship between ionization potential (IP) and electron affinity (EA) for the ground and excited states of a molecule and the corresponding ground- and excited-states redox potentials...

Concluding this section all that one can say is that we found no relationship between anesthetic potency and either the ionization potentials or the frequency of the lowest ultraviolet absorption band. The observation that replacement of a fluorine atom by a hydrogen usually lowers the IP is probably of some value. However, as was pointed out above this could only indicate the possibility of charge transfer interaction if the electron affinities followed the same trend. Unfortunately these have not been determined and the variations in the frequencies of the broad UV bands are too irregular to draw conclusions. It seems that there exists an indirect relationship between the acidity of these molecules and their IPs and what counts is their proton donor ability connected with the acidic hydrogen as has been concluded from the infrared studies described in previous sections. 

The electron affinities of many of the molecules determined in the ECD or NIMS have been verified by half-wave reduction potentials and charge transfer complex data. These methods were developed in the 1960s but have been significantly improved. The relationship between the electronegativity and the electron affinities and ionization potentials for aromatic hydrocarbons can be used to support the Ea. The use of the ECD model and these techniques to estimate the electron affinities of aromatic hydrocarbons are illustrated for selected compounds. We will also describe the use of charge transfer complex data to obtain the electron affinities of acceptors. 

Related procedures for estimating electron affinities make use of the concept of electronegativity (EN). These use the Mulliken [33] definition of absolute electronegativity, the average of the first ionization potential and the first electron affinity, EN = (IP + EA)/2. With an estimate of the Mulliken electronegativity and the experimental value of the ionization potential, the electron affinities can be calculated. When both the electron affinity and ionization potential are measured, the relationship between the EN and experiment can be examined. This has been accomplished for aromatic hydrocarbons and will be discussed in Chapter 10. 

Determination of proton affinities (basicities) and acidities in the gas phase provides a means of systematically representing a large number of ion-molecule reactions and of the relationships between these quantities and bond strengths, ionization potentials and electron affinities without disturbance by solvation phenomena 47). 

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