DFT-D4 Insight into the Inclusion of Amphetamine and Methamphetamine in Cucurbit[7]uril: Energetic, Structural and Biosensing Properties

The host–guest interactions of cucurbit[7]uril (CB[7]) as host and amphetamine (AMP), methamphetamine (MET) and their enantiomeric forms (S-form and R-form) as guests were computationally investigated using density functional theory calculations with the recent D4 atomic-charge dependent dispersion corrections. The analysis of energetic, structural and electronic properties with the aid of frontier molecular orbital analysis, charge decomposition analysis (CDA), extended charge decomposition analysis (ECDA) and independent gradient model (IGM) approach allowed to characterize the host–guest interactions in the studied systems. Energetic results indicate the formation of stable non-covalent complexes where R-AMP@CB[7] and S-AMP@CB[7] are more stable thermodynamically than R-MET@CB[7] and S-MET@CB[7] in gas phase while the reverse is true in water solvent. Based on structural analysis, a recognition mechanism is proposed, which suggests that the synergistic effect of van der Waals forces, ion–dipole interactions, intermolecular charge transfer interactions and intermolecular hydrogen bonding is responsible for the stabilization of the complexes. The geometries of the complexes obtained theoretically are in good agreement with the X-ray experimental structures and indicate that the phenyl ring of amphetamine and methamphetamine is deeply buried into the cavity of CB[7] through hydrophobic interactions while the ammonium group remains outside the cavity to establish hydrogen bonds with the portal oxygen atoms of CB[7].

The interaction between carboplatin anticancer drug and B12N12 nano-cluster: A computational investigation

This study investigated the interaction between B12N12 nano-cluster and carboplatin complex using B3P86 functional. Two interaction modes between B12N12 nano-cluster and carboplatin complex were considered. The bonding interaction between the B12N12 nano-cluster and carboplatin complex was examined through energy decomposition analysis (EDA). Also, Shubin Liu’s energy decomposition analysis (EDA-SBL) is used to study the source of energy differences between various isomers of B12N12 ... carboplatin complex. Charge transfer between fragments were illustrated with electrophilicity-based charge transfer (ECT) and extended charge decomposition analysis (ECDA). The quantum theory of atoms in molecules (QTAIM) analysis was applied to assess the Pt-B and Pt-N bonds within B12N12 ... carboplatin complex.

Enhanced π-back-donation resulting in the trans labilization of a pyridine ligand in an N-heterocyclic carbene (NHC) PdII precatalyst: a case study

The molecular structure of the benzimidazol-2-ylidene–PdCl2–pyridine-type PEPPSI (pyridine-enhanced precatalyst, preparation, stabilization and initiation) complex {1,3-bis[2-(diisopropylamino)ethyl]benzimidazol-2-ylidene-κC 2}dichlorido(pyridine-κN)palladium(II), [PdCl2(C5H5N)(C23H40N4)], has been characterized by elemental analysis, IR and NMR spectroscopy, and natural bond orbital (NBO) and charge decomposition analysis (CDA). Cambridge Structural Database (CSD) searches were used to understand the structural characteristics of the PEPPSI complexes in comparison with the usual N-heterocyclic carbene (NHC) complexes. The presence of weak C—H...Cl-type hydrogen-bond and π–π stacking interactions between benzene rings were verified using NCI plots and Hirshfeld surface analysis. The preferred method in the CDA of PEPPSI complexes is to separate their geometries into only two fragments, i.e. the bulky NHC ligand and the remaining fragment. In this study, the geometry of the PEPPSI complex is separated into five fragments, namely benzimidazol-2-ylidene (Bimy), two chlorides, pyridine (Py) and the PdII ion. Thus, the individual roles of the Pd atom and the Py ligand in the donation and back-donation mechanisms have been clearly revealed. The NHC ligand in the PEPPSI complex in this study acts as a strong σ-donor with a considerable amount of π-back-donation from Pd to Ccarbene. The electron-poor character of PdII is supported by π-back-donation from the Pd centre and the weakness of the Pd—N(Py) bond. According to CSD searches, Bimy ligands in PEPPSI complexes have a stronger σ-donating ability than imidazol-2-ylidene ligands in PEPPSI complexes.

The transition metal to ligand bonding nature: A quantum chemical study of π-allyl-ruthenacycle molecule

Understanding of the transition metal (TM) to ligand (L) bonding nature is important for characterization of experimental observations. One of the methods to explain the TM to L interactions is the Dewar–Chatt–Duncanson (DCD) model. However, in most applications the validity of the DCD model is based on assumptions in order to explain trends in vibrational spectroscopy or other physical properties of TM complexes. In this paper the computational methodology for treatment of the π-allyl-ruthenacycle complex based on the density functional theory, restricted Hartree–Fock method, natural bond orbital and charge decomposition analysis is reported. It is shown how the DCD model emerges from the presented calculation scheme and how it relates with the physical properties and stability of this complex. It is important to note that in this work the determination of the DCD model operation is based on the defined computational procedure, not postulated beforehand. The calculated geometry parameters, vibrational frequencies and electron density arrangement for the π-allyl-ruthenacycle complex are in good agreement with the experiment and support the DCD model.

Donor-driven conformational flexibility in a real-life catalytic dicopper(ii) peroxo complex

The conformers of the real-life tyrosinase model [Cu2O2{HC(3-tBuPz)2(Py)}2]2+which displays catalytic hydroxylation reactivity were investigated by density functional theory (DFT) studies including second-order perturbation theory and charge decomposition analysis (CDA).