Three-Body Dispersion Corrections to the Spherical Atom Model: The PFD-3B Density Functional

The low-lying electronic states and ultrafast relaxation dynamics of the monomers and J-aggregates of meso-tetrakis (4-sulfonatophenyl)-porphyrins

The electronic and vibrational spectra of the meso-tetrakis(4-sulfonatophenyl)-porphyrins (TSPP) have been studied computationally using the PFD-3B functional with time-dependent density functional theory for the excited states. The calculated UV-vis absorption and emission spectra in aqueous solution are in excellent agreement with the experimental measurements of both H2TSPP-4 (monomer) at high pH and H4TSPP-2 (forming J-aggregate) at low pH. Moreover, our calculations reveal an infrared absorption at 1900 cm-1 in the singlet and triplet excited states that is absent in the ground state, which is chosen as a probe for transient IR absorption spectroscopy to investigate the vibrational dynamics of the excited state. Specifically, the S2 to S1 excited state internal conversion process time, the S1 state vibrational relaxation time, and the lifetime of the S1 excited electronic state are all quantitatively deduced.

Improved Geometries and Frequencies with the PFD-3B DFT Method

Bond lengths have been calculated for a test set of 120 diatomic species, including all homonuclear diatomics, hydrides, fluorides, and oxides for elements H through Kr for which experimental data is available for comparison. The performance of the PFD-3B functional is significantly better than competitive DFT methods. The rms error in bond lengths is reduced to 0.01 Å using a moderate size 3Za1Pa + f triple-ζ basis set, with the rms error in harmonic vibrational constants, ω_e, equal to 38 cm^-1. A very small 2ZP0H basis set is sufficient to calculate anharmonic constants, ω_eX_e, within ±4 cm^-1. The rotational constants, B_e, agree with experiment to within ±2%, and the vibration-rotation coupling constants, α_e, agree within 10%. The calculated vibrational zero-point energy, ZPE, agrees with experiment to within ±0.06 kcal mol^-1 for the diatomic test set, and the error increases to just ±0.11 kcal mol^-1 for a set of 12 small polyatomic species. Comparison of a detailed anharmonic analysis of the twisted ethylene cation to the PFI-ZEKE experimental data illustrates the reliability of the PFD-3B for atypical structures.

Simulation and computational study of graphene oxide nano-carriers, absorption, and release of the anticancer drug of camptothecin

The structure of nano-graphene oxide has attracted special attention in drug release due to its special properties such as hydrophilicity, special surface, biocompatibility, and the possibility of high loading of hydrophilic and hydrophobic drugs. In this study, after simulating and optimizing the structure of nano-graphene and then nano-graphene oxide (NGO), it was used to load the anti-cancer drug of camptothecin (CA) in an aqueous medium, and the optimal conditions for achieving maximum loading efficiency of the drug were investigated. Due to the structure of the drug, there are two forms, one form of lactone ring and the other carboxylate. If the lactone ring form is predominant, the effectiveness of the drug is increased. This depends on pH of the environment. The calculated thermodynamic and structural results show that the solubility of the drug about nano-graphene and its lactone ring state is maintained by using nano-graphene oxide. To increase the effectiveness of the drug, the lactone ring form must be maintained in the drug structure. The use of folic acid as an intermediate in the aqueous medium preserves the lactone form in the drug structure and increases its effectiveness. The results show that the presence of the ring in the drug structure and its binding to the mediator of folic acid to nano-graphene oxide is a stabilizing factor of keto tautomer. The calculation of vibrational frequencies shows that the presence of folic acid intermediate reduces the vibrational frequency of the hydroxyl group (OH) so that its absorption energy (E_ad) is equal to the lowest value 65.24 a.u.