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The importance of impurity-related detection and certification in drug manufacture is highlighted in this study, which presents theoretical structural and spectral properties of clomipramine (CPA) and methotrimeprazine HCl (MPH) as well as their adsorption on graphene and fullerene. Investigating adsorption may reveal details about their reactivity, electronic and structural properties. The molecule's frontier molecular orbitals (FMOs) energies and energy gaps were calculated. Three-dimensional visualization of the electrostatic potential diagrams was mapped. Docking was used to find the binding with the receptors. Enhancement for different wave numbers is seen in the graphene/fullerene complex-molecules assembly. Non-covalent interactions (NCI) can be characterized using topological analysis and the respective isosurfaces. In the CPA-graphene cluster, the graphene system shows strong repulsive non-covalent interactions (red portions). Two small green portions of the isosurface between CPA and graphene frameworks indicate weak non-covalent interactions. [ABSTRACT FROM AUTHOR]

Using metal substrates that are nanoscale in size, surface-enhanced Raman scattering (SERS) is a technique for enhancing the Raman signal of biomolecules. Numerous industries including sensing materials, adsorption and medical devices, use nanomaterials like nanocages and nanoclusters. To discover a possible novel sensor platform involving a small metal cluster and a curved rigid substrate, we used density functional theoretical (DFT) simulations to explore the adsorption of glycoluril (GLC), a prospective drug intermediate, on a pure magnesium oxide cage (Mg12O12). This well defined cage was used as (i) an exact probable structure that could be used as well as (ii) a general model for MgO nanostructures. We also investigated the mono Al-doped Mg12O12 nanocage version Mg11AlO12. All computations were performed at the M06-2X level of theory. The GLC binds to the Mg12O12 nanocage by way of strong donor–acceptor interactions. The adsorption is releasing − 45.80 kcal mol−1 of energy. Due to Al doping, the energy gap of GLC-Mg11AlO12 (1.91 eV) is reduced from that of GLC-Mg12O12 (4.28 eV) and hence there is an increase in electrical conductivity of GLC-Mg11AlO12. The electronic change in the nanocage's conductivity can be transformed into an electrical signal which can be used to detect the presence of the drug analyte. In addition, when a GLC molecule is present, the work function of the nanocage is also reduced. The MgO nanocage, we conclude, is a work function type as well as a possible electronic sensor for GLC drug detection. GLC desorption from the Mg11AlO12 surface recovers more quickly in comparison with Mg12O12 recovery time. The AIM and NCIs assessed in this study were performed to help analyze the electronic structures of the complexes. Our findings pave the possibility for Mg11AlO12 nanostructures to be used in drug recognition. [ABSTRACT FROM AUTHOR]

The zwitterionic (zw-) type intramolecular [3 + 2] cycloaddition (IM32CA) reactions of C,N-disubstituted nitrones bearing acyclic and cyclic alkene functionalities have been studied from the molecular electron density theory (MEDT) perspective. The nitrones under study were classified as zwitterionic species from the topological analysis of the electron localization function (ELF). These IM32CA reactions show non-polar character and follow a non-concerted one step mechanism with activation free energies of 22.8--35.2 kcal mol-1 in toluene. When the N-butenyl system is attached to the nitrogen atom of the nitrone, the IM32CA reaction presents total regioselectivity with the terminal alkene carbon involved in C--C bond formation in complete agreement with the experimental findings. Interestingly, the activation free energy shows a sharp increase of 6.1 kcal mol-1 on dimethyl substitution of the terminal carbon owing to the considerable increase in the non-covalent strongly repulsive interaction revealed by the reduced density gradient scatter map of the NCI plot. This agrees well with the experiments showing no reaction of the corresponding nitrone. For the nitrones with a cyclic alkene functionality, the activation energies are decreased by 5.1--6.2 kcal mol-1 compared to the acyclic one, due to the relatively lower energy cost demanded for the similar bonding changes along the reaction path. [ABSTRACT FROM AUTHOR]

The [3 + 2] cycloaddition (32CA) reactions of 1‐pyrroline‐1‐oxide with acetylene and with a series of four symmetrically disubstituted acetylenes (XC ≡ CX, X = CH3, NH2, OH, F), leading to 4,5‐disubstituted bicyclic 4‐isoxazolines, have been studied within molecular electron density theory at the B3LYP‐D3/6‐311++G(d,p) computational level. These 32CA reactions take place through a one‐step mechanism, with activation enthalpies in toluene between 24.4 (X = NH2) and 12.9 (X = F) kcal mol−1. Due to the strong exergonic character of these 32CA reactions, between −12.0 and −47.6 kcal mol−1, they are irreversible. The 32CA reaction of difluoroacetylene, involving fluorine as the most electronegative atom of this series attached to the acetylene carbons, presents the lowest activation enthalpy due to the increase of the polar character of this 32CA reaction, evidenced by the analysis of the global electron density transfer at the corresponding transition state structure. The topological analysis of the electron localization function along the reaction paths of these 32CA reactions allows us to characterize them as the zwitterionic‐type ones. The formation of the new CC and CO single bonds takes place at the end of the reactions through the coupling of pseudoradical centers. [ABSTRACT FROM AUTHOR]

The strain promoted [3+2] cycloaddition reaction of benzyl azide with cyclooctyne has been studied within the molecular electron density theory (MEDT) at the MPWB1K/6-311G(d,p) computational level. This reaction takes place through a one-step mechanism with activation free energy of 27.1 kcal mol-1 in gas phase and 30.2 kcal mol-1 in acetonitrile. The activation enthalpies are 13.8 and 16.5 kcal mol-1, respectively in gas phase and acetonitrile. Topological analysis of the electron localization function (ELF) of the reagents shows zwitter-ionic type character of this reaction. The calculated activation free energy is lowered by 5.0 kcal mol-1 in gas phase and 4.2 kcal mol-1 in acetonitrile relative to the analogues reaction with acetylene. The corresponding activation enthalpy is lowered by 6.4 kcal mol-1 in gas phase and 5.9 kcal mol-1 in acetonitrile. A comparative bonding evolution theory (BET) analysis of the two reactions reveals lower energy requirements for the depopulation of the alkyne framework and the formation of pseudoradical centers along the reaction path of the cyclooctyne reaction. Topological analysis of the ELF and the Quantum Theory of Atoms in Molecules (QTAIM) parameters reveal early transition states with no covalent bonding interactions between the reacting nuclei, which is consistent with the forming bond distances greater than 2 Å in each case. [ABSTRACT FROM AUTHOR]

Nitrile imine has been classified as carbenoid type three atom component (TAC) by coupled cluster single doubles plus perturbative triples (CCSD(T)) calculations. [3+2] cycloaddition (32CA) reactions of nitrile imine with a set of olefins has been studied in this report in terms of Global electron density transfer (GEDT), Bonding evolution theory (BET) and Quantum theory of atoms in molecules (QTAIM) analyses at B3LYP and MPW1K levels. The reactions have been nonpolar showing non-covalent interactions and hence GEDT doesn't make the reaction feasible by inducing significant electrophilic-nucleophilic interaction between reactants as occurs in case of polar processes. Mutual penetration of forming bonds to the Van-der Waals' surface has been reproduced in asymmetry indices at the transition states. BET and QTAIM study confirmed initial rupture of olefinic bond, followed by the formation of pseudoradical centres and subsequently the bond-formation processes. [ABSTRACT FROM AUTHOR]

- tert-butylmethanimine -oxide is a potent spin-trapping probe for biologically important radicals, and this nitrone undergoes complete regioselective cycloadditions to less electron-deficient monosubstituted olefins. In the present study, solvent effects on the cycloaddition of this nitrone to styrene have been theoretically studied in terms of the global properties of the reactants, electrophilic and nucleophilic Parr function analysis and the activation and reaction energies of located transition states and products. Formation energies of optimized radical adducts were computed to determine their stabilities in different solvents. The cycloaddition is predicted to be completely ortho regioselective which is in complete agreement with experiments and involved earlier C-C bond formation owing to the insufficient depopulation of -conjugated carbon atom in styrene and shows varying asymmetry indices in different solvents. Decrease in activation parameters and increase in stability of cycloadducts are predicted with decreasing solvent polarity. Aqueous media destabilize the radical adducts as predicted from the calculated formation energy, enthalpy and free energy of reaction. Hydroxyl as well as methyl radical adducts are predicted to be more stable than superoxide anion radical adducts. These predictions are in complete agreement with the experiments. [ABSTRACT FROM AUTHOR]

Due to its negative effects on people, melamine contamination in food products are detected and filtered. Amongst several sensory schemes for the screening of melamine poisoning, one of the most promising techniques is the use of nanomaterial based sensing for real time applicability in industries. In the current work, we have looked into the way melamine binds to Ga 12 -N 12 /P 12 nanocages. Surface-enhanced Raman scattering (SERS), a successful spectroscopic technique is used to monitor melamine. Density functional theoretical (DFT) computations were used to study the sensing properties of melamine (Me) with Ga 12 -N 12 /P 12 nanocages. Reactivity and Mulliken charge analyses show charge transfer from melamine to nanocage. Me-Ga 12 -N 12 and Me-Ga 12 P 12 clusters have adsorption energies of -47.54 and -33.12 kcal/mol, respectively. All nanocage-Me systems have a significant increase in polarizability. The electron densities revealed non-covalent interactions in the adsorbed systems. All adsorption energies in aqueous media are negative, indicating an attractive and exothermic reaction, with maximum value in water for Me-Ga 12 N 12 and in acetone for Me-Ga 12 P 12 . Evidence of SERS is observed due to the enhancement of different vibrational modes.Communicated by Ramaswamy H. Sarma.