Lowest unoccupied molecular orbital INDEX

In addition to the above prescriptions, many other quantities such as solution phase ionization potentials (IPs) [15], nuclear magnetic resonance (NMR) chemical shifts and IR absorption frequencies [16-18], charge decompositions [19], lowest unoccupied molecular orbital (LUMO) energies [20-23], IPs [24], redox potentials [25], high-performance liquid chromatography (HPLC) [26], solid-state syntheses [27], Ke values [28], isoelectrophilic windows [29], and the harmonic oscillator models of the aromaticity (HOMA) index [30], have been proposed in the literature to understand the electrophilic and nucleophilic characteristics of chemical systems. 

If only the electron density of the highest occupied molecular orbital (HOMO) is taken into account, an electrophilic attack is said to be regulated by the frontier electron density index (54JCP1433 79FCF1). In nucleophilic substitutions, the aromatic substrate tends to accept an electron pair in the transition state, and so the frontier orbital is taken as the lowest unoccupied molecular orbital (LUMO). In this case, the frontier electron density is assumed to be as the electron distribution that would be present in the LUMO if it were occupied by two electrons. In contrast to arguments based on the charge or 7c-electron densities, both nucleophilic and electrophilic substitution occur preferentially at the atom with the highest electron density within the appropriate frontier orbital, i.e., LUMO or HOMO, respectively. 

Linear relationships between quantum chemical indexes (maximum negative (q ax) and positive (q x) charges) as well as energies of highest occupied molecular orbital (Ehomo = IP) where IP is the vertical ionization potential) and lowest unoccupied molecular orbital (Elumo) find the empirical donor-acceptor parameters of organic molecules were established in [49]. Parameters of the relationships are presented in Table 1. 

Lovasz-Pelikan index spectral indices (0 eigenvalues of the adjacency matrix) LOVIs = LOcal Vertex Invariants local invariants Lowdin population analysis quantum-chemical descriptors Lowest-Observed-Effect Level biological activity indices (0 toxicological indices) lowest unoccupied molecular orbital quantum-chemical descriptors lowest unoccupied molecular orbital energy quantum-chemical descriptors LUDI energy function scoring functions Lu index —> hyper-Wiener-type indices... 

TABLE 4.15 The Training (Calibration) and Test (Marked With Asterisk - to be chosen) Compounds Studied Along Their HOMA (Harmonic Oscillator Model of Aromatic) Index (Mosquera et al., 2007 Ciesielski et al., 2009) and of Associated Computed (Hypercube, 2002 (Semiempirical, AMI, Polak-Ribier optimization procedure)) Structural First, Second, and Third Order HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) Reactivity Indices (Tarko Putz, 2010)... 

---