Molecular descriptor superdelocalizability

The maximum electrophilic superdelocalizability among all the atoms in a molecule is a molecular descriptor defined as ... 

A variety of molecular descriptors have been defined and used proceeding from frontier molecular orbital theory (FMO) of chemical reactivity [42]. This theory is based on the concept of the superdelocalizability, an index characterizing the affinity of occupied and unoccupied orbitals in chemical reactions. A distinction has been made between the electrophilic and the nucleophilic superdelocalizability (or acceptor and donor superdelocalizability), respectively. The former describes the interaction of... 

Quantum-chemical descriptors The quantum-chemical molecular descriptors are derived from the eigenvalues and eigenvectors. Descriptors based on the eigenvalues are the HOMO and LUMO. Atomic charges, dipole moment, bond orders, and frontier orbital indices are derived from the coefficients of the eigenvectors of the atomic orbitals. The superdelocalizability index is based on both the values of the eigenvalues and eigenvectors. 

Several different kinds of quantum-chemical descriptors have been defined, and these can be broadly divided into energy-based descriptors, local quantum-chemical properties, descriptors based on the Density Functional Theory, molecular orbital energies, superdelocalizability indices, frontier orbital electron densities, and polarizabilities [Cartier and Rivail, 1987 Bergmann and Hinze, 1996 Karelson et al, 1996]. 

Charge descriptors and several - quantum-chemical descriptors such as -+ molecular orbital energies and - superdelocalizability indices are examples of reactivity indices. 

Protein binding and several other SAR s of phenols are correlated by summed electrophilic superdelocalizabilities [ZS (E)] and the electron density of the hydroxyl oxygen atom divided by MW (q /MW) (142). Descriptor estimations are based on HMO calculations. The involvement of molecular electrophilic character with specific in-volvment of phenolic OH suggests general dipolar binding with probable H-bond formation. As in the previous case, the same conclusions would likely be reached with classical descriptors, though it is rare for quantum chemists to cross-validate in this way. 

The electronic properties of a molecnle include physical aspects of its chemistry, such as its ability to accept and donate hydrogen bond, ionization, dipole moment, as well as those calculated from a knowledge of electron distribution. Of the last, molecular orbital properties are easily calculated and widely used these include atomic charge, superdelocalizability, and energies of electrons in specific molecular orbitals. The calculation and use of electronic descriptors, molecular orbital properties in particular, were well reviewed by Schuurmaim (2004). 

Historically, multiple theoretical descriptor-based approaches to H-bond strength ranking were proposed. That includes approaches based on group contribution method [46], electrostatic potentials [47], electrophilic superdelocalizability and self-atom polarizability [48], Quantum Theory of Atoms In Molecules (QTAIM) descriptors [49-51], the two-center shared electron number a and the product of ionization potential [45, 52], and local quantum mechanical molecular parameters, which quantify electrostatic, polarizability, and charge transfer contributions to H-bonding [53, 54],... 

The display facilities range from simple descriptors, such as atomic charges, bond orders, and bond strains, to multidimensional energy maps, IR spectra, UV/visible spectra, molecular orbitals, and reactivity surfaces such as electron densities, electrostatic potentials, and Fukui susceptibilities and superdelocalizabilities (electrophilic, radical, and nucleophilic). The presentation-quality figures can be readily cut and pasted into a wide range of desktop publishing applications. 

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