Semiempirical Approach to the Fukui Function Analysis of Uric Acid under Different pH Conditions.

Analytic Fukui functions calculated at a first-principles level are combined with experimental p values and the calculation of tautomerization energies to obtain the effective regioselectivity of uric acid toward electron-transfer reactions under different pH conditions. Second-order electron binding energies are also computed to determine which of the tautomers is more likely to participate in the electron transfer. A comparison of vertical and adiabatic proton detachment energies allows us to conclude that tautomerization is not mediating deprotonation and that two monoanionic species are of comparable relevance.

H NMR global diatropicity in copper hydride complexes.

Understanding the magnetic response of electrons in nanoclusters is essential to interpret their NMR spectra thereby providing guidelines for their synthesis towards various target applications. Here, we consider two copper hydride clusters that have applications in hydrogen storage and release under standard temperature and pressure. Through Born-Oppenheimer molecular dynamics simulations, we study dynamics effects and their contributions to the NMR peaks.

derivation of flavin hyperfine interactions for the protein magnetosensor cryptochrome.

The radicals derived from flavin adenine dinucleotide (FAD) are a corner stone of recent hypotheses about magnetoreception, including the compass of migratory songbirds. These models attribute a magnetic sense to coherent spin dynamics in radical pairs within the flavo-protein cryptochrome. The primary determinant of sensitivity and directionality of this process are the hyperfine interactions of the involved radicals.

Metallaborazines: To Be or Not To Be Delocalized.

In the current work, the analysis of the electronic delocalization of some metallacycles, based on borazine, was realized by employing magnetic criteria, such as the induced magnetic field and magnetically induced current densities, and electronic criteria, such as adaptative natural density partitioning and the analysis of molecular orbitals. The current metallaborazines were generated from isoelectronic substitutions. The main question is whether the electronic delocalization increases or decreases.

Cubic aromaticity in ligand-stabilized doped Au superatoms.

The magnetic response of valence electrons in doped gold-based M@AuL superatoms (M = Pd, Pt, Ag, Au, Cd, Hg, Ir, and Rh; L = PPh; and q = 0, +1, +2) is studied by calculating the gauge including magnetically induced currents (GIMIC) in the framework of the auxiliary density functional theory. The studied systems include 24 different combinations of the dopant, total cluster charge, and cluster structure (cubic-like or oblate). The magnetically induced currents (both diatropic and paratropic) are shown to be sensitive to the atomic structure of clusters, the number of superatomic electrons, and the chemical nature of the dopant metal.

Magnetically induced currents and aromaticity in ligand-stabilized Au and AuPt superatoms.

Understanding magnetically induced currents (MICs) in aromatic or metallic nanostructures is crucial for interpreting local magnetic shielding and NMR data. Direct measurements of the induced currents have been successful only in a few planar molecules but their indirect effects are seen in NMR shifts of probe nuclei. Here, we have implemented a numerically efficient method to calculate gauge-including MICs in the formalism of auxiliary density functional theory.

Analysis of the electronic delocalization in some isoelectronic analogues of B doped with beryllium and/or carbon.

In the current work, a new family of isoelectronic analogues to B12 is reported. The construction of this family was performed through the isoelectronic substitution principle to generate species such as B11C+, B11Be-, B10BeC, B10C22+, B10Be22- B9Be2C-, and B9BeC2+. The search for the global minimum was realized by utilizing genetic algorithms, while the induced magnetic field, electronic localization function, magnetic current densities, and multicenter aromaticity criteria were calculated to understand their electronic delocalization.

Calculation of the EPR g-tensor from auxiliary density functional theory.

The working equations for the calculation of the electron paramagnetic resonance (EPR) g-tensor within the framework of the auxiliary density functional theory (ADFT) are presented. The scheme known as gauge including atomic orbitals (GIAOs) is employed to treat the gauge origin problem. This ADFT-GIAO formulation possesses an inherent high computational performance, allowing for the calculation of the EPR g-tensor of molecules containing some hundreds of atoms in reasonable computational time employing moderate computational resources.

Efficient calculation of nuclear spin-rotation constants from auxiliary density functional theory.

The computation of the spin-rotation tensor within the framework of auxiliary density functional theory (ADFT) in combination with the gauge including atomic orbital (GIAO) scheme, to treat the gauge origin problem, is presented. For the spin-rotation tensor, the calculation of the magnetic shielding tensor represents the most demanding computational task. Employing the ADFT-GIAO methodology, the central processing unit time for the magnetic shielding tensor calculation can be dramatically reduced.

Efficient calculation of the rotational g tensor from auxiliary density functional theory.

The computation of the rotational g tensor with the recently developed auxiliary density functional theory (ADFT) gauge including atomic orbital (GIAO) methodology is presented. For the rotational g tensor, the calculation of the magnetizability tensor represents the most demanding computational task. With the ADFT-GIAO methodology, the CPU time for the magnetizability tensor calculation can be dramatically reduced.

Magnetizability tensors from auxiliary density functional theory.

The working equations for the calculation of the magnetizability tensor in the framework of auxiliary density functional theory with gauge including atomic orbitals (ADFT-GIAO) are derived. Unlike in the corresponding conventional density functional theory implementations the numerical integration of the GIAOs is avoided in ADFT-GIAO. Our validation shows that this simplification has no effect on the accuracy of the methodology.

NMR shielding tensors from auxiliary density functional theory.

The working equations for the calculation of NMR shielding tensors in the framework of auxiliary density functional theory are derived. It is shown that in this approach the numerical integration over gauge-including atomic orbitals can be avoided without the loss of accuracy. New integral recurrence relations for the required analytic electric-field-type integrals are derived.

A MinMax self-consistent-field approach for auxiliary density functional theory.

A MinMax self-consistent-field (SCF) approach is derived in the framework of auxiliary density functional theory. It is shown that the SCF convergence can be guided by the fitting coefficients that arise from the variational fitting of the Coulomb potential. An in-core direct inversion of the iterative subspace (DIIS) algorithm is presented.

Density functional theory optimized basis sets for gradient corrected functionals: 3d transition metal systems.

Density functional theory optimized basis sets for gradient corrected functionals for 3d transition metal atoms are presented. Double zeta valence polarization and triple zeta valence polarization basis sets are optimized with the PW86 functional. The performance of the newly optimized basis sets is tested in atomic and molecular calculations.