Electronegativity is a well-known property of atoms and substituent groups. Because there is no direct way to measure it, establishing a useful scale for electronegativity often entails correlating it to another chemical parameter; a wide variety of methods have been proposed over the past 80 years to do just that. This work reports a new approach that connects electronegativity to a spectrosco...

The aim of the present study was to prepare new cluster (B6C4Si) as an antibiotic carrier. Density functional theory (DFT) method at the B3LYP level of theory in conjugate with the 6-311G** basis set was used to evaluate the interaction between B6C4Si cluster and Penicillin. Binding parameters, HOMO, LUMO and HOMO- LUMO GAP were calculated. Results show the ‍ B6C4Si HOMO–LUMO gap value of 0.13...

Electronic and geometric structures of MxSy (M=W, Mo; x = 1, 2, 4; y = 1–12) clusters have been studied using density functional theory calculations, and compared to experimental photoelectron spectra. For the metal atoms, an uptake of up to six sulfur atoms has been observed, which can be explained by the bonding of S3 chains. A structural difference to the corresponding oxides is the preferen...

The electronic structure of ultrasmall Au clusters on thin MgO/Ag(001) films has been analyzed by scanning tunneling spectroscopy and density functional theory. The clusters exhibit two-dimensional quantum well states, whose shapes resemble the eigenstates of a 2D electron gas confined in a parabolic potential. From the symmetry of the highest occupied (HOMO) and lowest unoccupied molecular orb...

We present a partial ion yield experiment on freon 13, CF(3)Cl, excited in the vicinity of the C 1s and Cl 2p ionization thresholds. We have collected a large amount of cationic fragments and a few anionic fragments at both edges. We have observed a strong intensity dependence of Rydberg transitions with ion fragment size for the CF(n)Cl(+) and CF(n)(+)/F(+) (n=0-3) series at both the Cl 2p and...

Small monovalent ions are able to polarize carbonaceous nanostructures significantly. We report a systematic investigation of how monovalent and divalent ions influence valence electronic structure of graphene. Pure density functional theory is employed to compute electronic energy levels. We show that the lowest unoccupied molecular orbital (LUMO) of an alkali ion (Li(+), Na(+)) fits between t...

Dihydrofolate reductase (DHFR) plays a ubiquitous role in the biosynthesis of DNA, RNA and essential amino acid methionine, and exhibits potential application in the treatment and prophylaxis of AIDS-associated opportunistic microbial infections. In this study, a series of DHFR analogs of 2,4-diaminopyrido[2,3-d]pyrimidines and 2,4-diaminopyrrolo[2,3-d]pyrimidines were subjected to quantitative...

In mathematical chemistry, the median eigenvalues of the adjacency matrix of a molecular graph are strictly related to orbital energies and molecular orbitals. In this regard, the difference between the occupied orbital of highest energy (HOMO) and the unoccupied orbital of lowest energy (LUMO) has been investigated (see Fowler and Pisansky in Acta Chim. Slov. 57:513-517, 2010). Motivated by th...

By making use of Janak’s interpolation in the Kohn-Sham method, together with an explicit and differentiable functional of the density for the exchange-correlation energy, like LDA or GGA, the second derivative of the energy with respect to the number of electrons, N, is evaluated from the derivative of the highest occupied molecular orbital (HOMO) with respect to N (left derivative), or from t...

In regard to the worldwide interest in synthesis and application of stable carbenes, DFT calculations (B3LYP/6-311++G**//B3LYP/6-31+G* levels) are employed to reach at a series of phenyl carbenes. The singlet-triplet energy separations (ΔES-T), HOMO–LUMO energy gaps (ΔEHOMO-LUMO), as well as philicity indices (N and ω) and basicity of these carbenes are compared and contrasted with the synthesi...