Effect of Dimerization and Racemization Processes on the Electron Density and the Optical Rotatory Power of Hydrogen Peroxide Derivatives

The variation of the electron density properties and optical rotatory power of the monomers and dimers of seven monosubstituted hydrogen peroxide derivatives, HOOX (X = CCH, CH3, CF3, t-Bu, CN, F, Cl), upon racemization has been studied using DFT (B3LYP/6-31+G**) and MP2 (MP2/6-311+G**) methods. The geometrical results have been rationalized on the basis of natural bond orbital (NBO) analysis. The atomic partition of the electron density properties within the atoms in molecules (AIM) methodology has allowed investigating the energy and charge redistribution in the different structures considered. The calculated optical rotatory power (ORP) of the dimers are, in general, twice of the values obtained for the monomers

Theoretical Study of Dihydrogen Bonds between (XH)₂, X = Li, Na, BeH, and MgH, and Weak Hydrogen Bond Donors (HCN, HNC, and HCCH)

The dihydrogen-bonded (DHB) complexes formed by (XH)2, with X = Li, Na, BeH, and MgH, with one, two, and four protonic molecules (HCN, HNC, and HCCH) have been studied. These complexes have been compared to those of the XH monomers with the same hydrogen bond donor molecules. The energetic results have been rationalized based on the electrostatic potential of the isolated hydridic systems. The electron density properties have been analyzed within the AIM methodology, both at the bond critical points and the integrated values at the atomic basins. Exponential relationships between several properties calculated at the bond critical points (ρ,∇2ρ, λi, G, and V) and variation of integrated properties (energy, charge, and volume) vs the DHB distance have been obtained

Raman, Surface-Enhanced Raman, and Density Functional Theory Characterization of (Diphenylphosphoryl)(pyridin-2‑, -3‑, and -4-yl)methanol

This work presents near-infrared Raman spectroscopy (FT-RS) and surface-enhanced Raman scattering (SERS) studies of three pyridine-α-hydroxymethyl biphenyl phosphine oxide isomers: (diphenylphosphoryl)­(pyridin-2-yl)­methanol (α-Py), (diphenylphosphoryl)­(pyridin-3-yl)­methanol (β-Py), and (diphenylphosphoryl)­(pyridin-4-yl)­methanol (γ-Py) adsorbed onto colloidal and roughened in oxidation–reduction cycles silver surfaces. The molecular geometries in the equilibrium state and vibrational frequencies were calculated by density functional theory (DFT) at the B3LYP 6-311G­(df,p) level of theory. The results imply that the most stable structure of the investigated molecules is a dimer created by two intermolecular hydrogen bonds between the H atom of the α-hydroxyl group (in up (HO_U) or down (HO_D) stereo bonds position) and the O atom of tertiary phosphine oxide (O) of the two monomers. Comparison the FT-RS spectra with the respective SERS spectra allowed us to predict the orientation of the hydroxyphosphonate derivatives of pyridine that depends upon both the position of the substituent relative to the ring N atom (in α-, β-, and γ-position, respectively) and the type of silver substrate