Chemical Bonding: The Journey from Miniature Hooks to Density Functional Theory

Our modern understanding of chemistry is predicated upon bonding interactions between atoms and ions resulting in the assembly of all of the forms of matter that we encounter in our daily life. It was not always so. This review article traces the development of our understanding of bonding from prehistory, through the debates in the 19th century C.E. bearing on valence, to modern quantum chemical models and beyond.

Quantum chemical models for the absorption of endohedral clusters on Si(111)-(7 × 7): a subtle balance between W–Si and Si–Si bonding

The absorption of endohedral clusters on Si(111)-7 × 7 generates a new bond between W and a surface silicon adatom.

Fermentative Metal – Containing Bio-Nano complexes, Quantum Chemical Models of Their Active Centers and Applications in Biotechnologies

The general structure and the functional universal mechanism of the active centers of the fermentative metal-containing bio-nanocomplexes are discussed on the basis of the quantum-chemical approach using the conception “protein — machine”. The process, proceeding taking place in the active centers structure is the result of their interaction with the substrates. The active centers quantum-chemical models represent the electron distribution among the complex molecular orbitals (MO). The interaction of the central ions with the ligands is carried out by the donor-acceptor mechanism: the ions provide the connection of the vacant orbitals and connection of the vacant orbitals and the ligands — the unshared electron pair. One of the coordination bonds is functional, using for the interaction with substrates. From the quantum-chemical point of view the functional mechanism of the bio-nanocomplexes is universal. In the final, it is reduced to the functional electron accepting and the leaving in the molecular antibonding orbitals of the complex, inducing the active center transitions from one state to another. The electron-conformational transitions, the active centers changes at its functioning, the role of its protein surrounding may be explained on a basis of the conception “protein — machine”. The specific properties of the investigated bio-nanosystems are involved in the using of the internal valuable information, that is the process is a wave and occurs self-correlatively, and may be described by Kolmogorov-Petrovskii-Piskunov mathematical model. It is fair to say that the discussing bio-nanosystems are the natural intellectual tools, which may be used in the nanobiotechnologies and the spheres of its application are wide. It is necessary to conclude that the metal-containing bio-nanocomplexes are the self-organizing, self-congruent, nonlinear, open systems.

Bi- and polynuclear coordination compounds of d-elements as catalysts of homogeneous selective oxidation of thiol groups

This research aims to study the catalytic cycle reactions for homogeneous selective oxidation of thiol RSH groups to RSSR with the participation of coordination compounds for d-element ions-NiII, PdII, Pt II, CuI , CuII. We used the DFT M06, PBE0 / Def2-TZVP methods to build the quantum chemical models of the reactions. We have developed a mechanism for the functioning of the catalytic system in which primary active centers are either binuclear {M(-OH)2M}n+ or polynuclear {M(μ-OH)2M(μ-OH)2M}2+ sites. Catalysts under consideration should retain stable spatial complementarity at all stages of the process. The main interrelated functions of the binuclear catalysts are the spatial approaching of anions RS– in the inner sphere of the bridged coordination compound required for the disulfide (–S–S–) cross-linking and the two-electron redox transfer during the transformation of these anions into disulfide (СH3)2S2

Upper-division chemistry students’ navigation and use of quantum chemical models

Chemical processes can be fully explained only by employing quantum mechanical models. These models are abstract and require navigation of a variety of cognitively taxing representations. Published research about how students use quantum mechanical models at the upper-division level is sparse. Through a mixed-methods study involving think-aloud interviews, a novel rating task, and an existing concept inventory, our work aims to fill this gap in the literature and begin the process of characterizing learning of quantum chemistry in upper-division courses. The major findings are that upper-division students tend to conflate models and model components. Students, unlike experts, focus on surface features. Our data indicates two specific surface features: lexical features and a “complex equals better” heuristic. Finally, there is no correlation in our data between a student's facility with navigating models and their conceptual understanding of quantum chemistry as a whole. We analyze the data through the lens of a framework which enables us to cast model conflation as a problem of ontology.