Realization of Either Physisorption or Chemisorption of 2H-Tetraphenylporphyrin on the Cu(111) from Density Functional Theory

The adsorption of organic molecules to surfaces is a central issue to achieve fully-functional molecular devices, for which porphyrins are well-studied due to their chemical stability and functional diversity. Herein, we investigate both the physical and the chemical adsorption of the free-base tetraphenylporphyrin 2H-TPP on the Cu(111) surface within the framework of density functional theory and find that the most stable physisorbed configuration is more weakly bound by -0.36 eV than the chemisorbed configuration. We use the electron localization function to investigate the difference in binding mechanisms between strong physisorption and weak chemisorption. We have computed a reaction barrier of 0.12 eV in going from physical binding to chemical bonding to the surface, and a barrier of 50 meV in going between neighboring physical binding sites. Our results support the possibility of realizing free-base porphyrins either physisorbed or chemisorbed on Cu(111) depending on the deposition procedure and experimental conditions.

Density Functional Study to Investigate the Ability of (ZnS)(n) (n = 1-12) Clusters Removing Hg(0), HgCl, and HgCl(2) via Electron Localization Function and Non-Covalent Interactions Analyses

In this study, the density functional theory is used to study the ability of (ZnS)_n clusters to remove Hg⁰, HgCl, and HgCl₂ and reveals that they can be absorbed on (ZnS)_n clusters. According to electron localization function (ELF) and non-covalent interactions (NCI) analyses, the adsorption of Hg⁰ on (ZnS)_n is physical adsorption and the adsorption ability of (ZnS)_n for removing Hg⁰ is weak. When (ZnS)_n adsorbs HgCl and HgCl₂, two new Hg-S and Zn-Cl bonds form in the resultant clusters. An ELF analysis identifies the formation of Hg-S and Zn-Cl bonds in (ZnS)_nHgCl and (ZnS)_nHgCl₂. A partial density of states and charge analysis confirm that as Hg⁰, HgCl, and HgCl₂ approach (ZnS)_n clusters, atomic orbitals in Hg and Zn, Hg and S, as well as Zn and Cl overlap and hybridize. Adsorption energies of HgCl and HgCl₂ on (ZnS)_n clusters are obviously bigger than those of Hg⁰, indicating that HgCl and HgCl₂ adsorption on (ZnS)_n clusters is much stronger than that of Hg⁰. By combining ELF analysis, NCI analysis, and adsorption energies, the adsorption of HgCl, and HgCl₂ on (ZnS)_n clusters can be classified as chemical adsorption. The adsorption ability of (ZnS)_n clusters for removing HgCl and HgCl₂ is higher than that of Hg⁰.

Molecular Electrides: An In Silico Perspective

Electrides are defined as the ionic compounds where the electron(s) serves as an anion. These electron(s) is (are) not bound to any atoms, bonds, or molecules rather than they are localized into the space, crystal voids, or interlayer between two molecular slabs. There are three major categories of electrides, known as organic electriades, inorganic electrides, and molecular electrides. The computational techniques have proven as a great tool to provide emphasis on the electride materials. In this review, we have focused on the computational methodologies and criteria that help to characterize molecular electrides. A detailed account of the computational methods and basis sets applicable for molecular electrides have been discussed along with their limitation(s) in this field. The main criterion for the identification of the electrides has also been discussed thoroughly with proper examples. The molecular electrides presented here have been justified with all the required criteria that support and proved their electride characteristics. We have also presented a few systems which have similar properties but are not considered as molecular electrides. Moreover, the applicability of the electrides in catalytic processes has also been presented.

The X-ray constrained wavefunction of the [Mn(CO)4{(C6H5)2P-S-C(Br2)-P(C6H5)2}]Br complex: a theoretical and experimental study of dihalogen bonds and other noncovalent interactions

The synthesis and X-ray structure determination of the [Mn(CO)₄{(C₆H₅)₂P-S-C(Br₂)-P(C₆H₅)₂}]Br complex (1) are described. The C-Br...Br dihalogen bond present in 1 has been characterized by means of topological studies of the electron density. Both the quantum theory of atoms in molecules and the electron localization function approaches have been applied to several theoretically calculated wavefunctions as well as to an X-ray constrained wavefunction. In addition, a number of theoretical techniques, such as the source function, the reduced density gradient method and the interacting quantum atoms approach, among others, have been used to analyse the dihalogen bond as well as several intramolecular interactions of the type C-H...Br-C which have also been detected in 1. The results show clearly that while bonding in the latter interactions are dominated by electrostatic components, the former has a high degree of covalency.