Joseph E. Fowler

ON THE REACTIVITY OF TI+(4F,2F). REACTION OF TI+ WITH OH2

The reaction of Ti+(4F,2F) + OH2 has been studied in detail for both doublet and quartet spin states. The only exothermic products are TiO+(2Δ) and H2; formation of several endothermic products is also examined. An in-depth analysis of the reaction paths leading to each of the observed products is given, including various singlet, triplet, and quartet minima, several important transition states, and a discussion of the two H2 elimination mechanisms proposed in the literature. The experimentally observed spin-forbidden crossing is given a possible explanation. Throughout this work comparison to experimental results in energetics, reaction products, and suggested mechanisms has been central.

Carbonyl–water hydrogen bonding: The H2CO–H2O prototype

The potential energy surface (PES) of the water–formaldehyde complex has been examined using ab initio methods. Three energetically low‐lying stationary points were located on the potential surface corresponding to one minimum and two transition states. All stationary points were examined using a double‐ζ plus polarization (DZP) basis set at the self‐consistent field (SCF), single and double excitation configuration interaction (CISD), and single and double excitation coupled‐cluster (CCSD) levels of theory. In addition, the minimum was more thoroughly investigated through the use of the triple‐ζ plus double polarization (TZ2P) basis set, the TZ2P plus higher angular momentum functions [TZ2P(f,d)] basis, and the TZ2P basis set augmented by a set of diffuse functions (TZ2P+diff) with those same theoretical methods. For each of the stationary points, geometrical parameters, absolute energies, classical binding energies, and zero‐point vibrational energy corrections are reported. Additional information conce...

Quantum mechanical calculations on phosphate hydrolysis reactions

Multiple biological processes are regulated by kinases and phosphatases. This study aims to provide nonenzymatic models for phosphorylation and dephosphorylation of serine, threonine, and tyrosine phosphate using ab initio guantum mechanical calculations. We reduce the problem to methyl phosphate hydrolysis to model serine/threonine, and the hydrolysis of phenyl phosphate to model the tyrosine. HF, B3LYP, and MP2 calculations with a 6‐31+G(d) basis set were employed. The effect of water as a catalyst was also analyzed. As expected, the activation energy barrier is lowered.

The silicon–carbon symmetric stretching fundamental ν1 of Si2C: Nonintuitive theoretical behavior

There are two experimental values for ν1(Si2C), namely 658 and 839 cm−1. Previous theoretical studies suggest a third value slightly below 800 cm−1. Here, elaborate theoretical studies using very large basis sets confirm that the ν1=839 cm−1 experiment of Presilla‐Marquez and Graham is correct. The contributions of both higher order correlation effects (as gauged by coupled cluster methods) and f functions are contrary to previous experience.

Critical conditions for stable dipole-bound dianions

Full configuration interaction calculations for two electrons moving in the field of an electric dipole have been carried out in order to determine whether bound states with respect to detachment of one electron exist. Model dipoles are constructed by the placement of point charges q=1, 2, 3 a.u. at varying distances. It was found that for a dipole constructed of point charges q=3 separated by a distance of 0.8788 a.u., the energy of binding one and two electrons is equivalent. In all cases, there exist charge separation lengths for which the binding of two electrons gives a binding energy only slightly less than that of binding one electron. Escape channels were not calculated, but may provide barriers allowing the existence of dipole-bound dianions with lifetimes long enough to allow detection.

Equilibrium geometry of isocyanomethylene (HCNC) and comparison to the troublesome isomer cyanomethylene (HCCN)

Inspired by the recent experimental study of the radical anions HCCN− and HCNC− and by earlier examinations of HCCN, the equilibrium geometry of the HCNC molecule has been investigated using both self‐consistent field (SCF) and configuration interaction methods including single and double excitations (CISD). The largest basis set used was a triple‐ζ plus double polarization with diffuse functions and higher angular momentum functions appended to each atom [TZ2P(f,d)+diff]. Using this basis, the H–C–N equilibrium angle is predicted to be 128.5° at the CISD level of theory. Additionally, the zero point vibrational energy (ZPVE) corrected energy separation of the bent and linear conformations was predicted to be 10.1 kcal mol−1 at the CISD level of theory with the largest basis set employed. The barrier to linearity is 7.7 kcal mol−1 at the CCSD level of theory and 6.9 kcal mol−1 at the CCSD(T) level of theory, employing the CISD optimized geometries with a basis that was comprised of triple‐ζ plus double po...