Exploring nonlinear optical properties in a hybrid dihydrogen phosphate system: an experimental and theoretical approach.

CONTEXT: The controlled slow evaporation process conducted at room temperature has produced a novel hybrid material denoted as (2-hydroxyethyl) trimethylammonium dihydrogen phosphate [2-HDETDHP] (C5H14NO+, H2PO4-), synthesized through the solution growth method. X-ray crystallography analysis reveals a triclinic structure with a filling rate of P and a Z value of 2. This hybrid material displays noteworthy absorption characteristics in the middle and far ultraviolet regions. UV-visible spectroscopy further establishes its transparency in the visible and near-visible ultraviolet domains. FT-IR spectroscopy examines various vibration modes, elucidating their relationships with the functional groups within the structure. Two- and three-dimensional fingerprint maps, coupled with three-dimensional crystal structures through Hirshfeld Surface Analysis, unveil the dominance of O•••H and H•••H interactions in the structure, comprising 49.40% and 50.40%, respectively. Fingerprint plots derived from the Hirshfeld surface assess the percentages of hydrogen bonding interactions, with 80.6% attributed to a fragment patch. The experiment of antimicrobial efficacy of a synthesized product, conducted in triplicate, demonstrated the synthesized product's potential antimicrobial activity. METHODS: Hirshfeld surfaces are employed to investigate intermolecular hydrogen bonding, specifically within single phosphate groups. The molecular structure of 2-HDETDHP was refined using single-crystal X-ray analysis, while its optical characteristics were examined through UV-visible spectroscopy. FT-IR spectroscopy is employed for the assignment of molecular vibrations of functional groups in the affined structure. Quantum calculations were executed with the GAUSSIAN 09 software package at B3LYP/6-311G level of theory, to optimize the molecular geometries. The antimicrobial efficacy of a synthesized product was evaluated using the disc diffusion method against antibiotic-resistant Candida albicans, Candida tropicalis, Aspergillus niger, Staphylococcus aureus, and Escherichia coli. Microorganisms were cultured on nutrient agar, and inhibition zones were measured after incubation, with streptomycin and amphotericin as positive controls.

Investigation of the interaction of thymine drugs with Be12O12 and Ca12O12 nanocages: A quantum chemical study.

Based on the DFT in a Wb97xd/6-311+G* level of theory, the interaction of thymine derivatives with Be12O12 and Ca12O12 nanocages was investigated. It was found that adsorption energies of thymine molecules on the Be12/Ca12-O12 surface was around -43.16, -60.06 and -29.62, -50.71, -45.95, -30.27 kcal/mol, for thymine (TH1), 1-amino thymine (TH2) and thymine glycol (TH3), respectively and this result supported the drug's adsorption. Additionally, according to the FMOs and MEP studies, a charge transfer from TH's to nanocages. Additionally, both molecular orbitals demonstrate that the LUMO and HOMO are primarily found on the BeO's surface.

DFT analysis on the adsorption of melamine in Ga12-N12/P12 nanocages: solvent effects, SERS analysis, reactivity properties.

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 Ga12-N12/P12 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 Ga12-N12/P12 nanocages. Reactivity and Mulliken charge analyses show charge transfer from melamine to nanocage. Me-Ga12-N12 and Me-Ga12P12 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-Ga12N12 and in acetone for Me-Ga12P12. Evidence of SERS is observed due to the enhancement of different vibrational modes.Communicated by Ramaswamy H. Sarma.

Theoretical study of glycoluril by highly symmetrical magnesium oxide Mg12O12 nanostructure: adsorption, detection, SERS enhancement, and electrical conductivity study.

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.

Unveiling the mechanism and selectivity of [3+2] cycloaddition reactions of benzonitrile oxide to ethyl trans-cinnamate, ethyl crotonate and trans-2-penten-1-ol through DFT analysis.

The mechanism and regioselectivity of [3+2] cycloaddition (32CA) reactions of benzonitrile oxide with ethyl trans-cinnamate, ethyl crotonate and trans-2-penten-1-ol has been studied in gas phase and in acetonitrile, ethyl acetate and tetrahydrofuran using the B3LYP functional in connection with 6-31G(d) basis set. The 32CA reactions followed one-step mechanism with asynchronous TSs. The calculated global electron density transfer (GEDT) at the TSs showed electronic flux from benzonitrile oxide to ethyl trans-cinnamate and ethyl crotonate, while the electronic flux from trans-2-penten-1-ol to benzonitrile oxide was predicted, in complete agreement with the Conceptual Density Functional Theory (CDFT) indices. The regioselectivity is correctly described in coherence with the experiment data. The intermolecular interaction at the TSs was realized through visualization and quantification by means of independent gradient model (IGM) analysis based on promolecular density.

Unravelling the regio- and stereoselective synthesis of bicyclic N,O-nucleoside analogues within the molecular electron density theory perspective.

The [3 + 2] cycloaddition (32CA) reactions of 1-pyrroline-1-oxide with N-vinyl nucleobases leading to bicyclic N,O nucleoside analogues have been studied within the molecular electron density theory (MEDT) at the MPWB1K/6-311G(d,p) computational level. These non-polar zwitterionic type 32CA reactions take place through a one-step mechanism with minimal global electron density transfer (GEDT) at the TSs and the exo/ortho approach mode as the energetically favoured reaction path. The 32CA reactions of N-vinyl nucleobases with thymine and cytosine substituents respectively show the activation enthalpies of 15.2 and 12.5 kcal mol-1 in toluene. The reactions are irreversible due to strong exothermic character of - 35.4-- 26.4 kcal mol-1 in toluene. The bonding evolution theory (BET) study suggests that these 32CA reactions take place through the coupling of pseudoradical centres with earlier C-C bond formation and the formation of new C-C and C-O covalent bonds has not been started in the TSs. Non-covalent interactions (NCI) are predicted at the TSs from the visualization of NCI gradient isosurfaces.

Theoretical analysis of the regio- and stereoselective synthesis of spiroisoxazolines.

The [3+2] cycloaddition (32CA) reaction of benzonitrile oxide to α-methylene cyclopentanone and propionitrile oxide to γ-methyl-α-methylene-γ-butyrolactone, yielding regio- and stereochemically defined spiroisoxazolines, has been studied at the MPWB1K/6-311G(d,p) computational level. These processes proceed by a one-step mechanism through asynchronous transition states. Ortho regioselectivity and anti diastereofacial selectivity are predicted in complete agreement with the experimental outcomes.

A Molecular Electron Density Theory Study of the Chemoselectivity, Regioselectivity, and Diastereofacial Selectivity in the Synthesis of an Anticancer Spiroisoxazoline derived from α-Santonin.

The [3 + 2] cycloaddition (32CA) reaction of an α-santonin derivative, which has an exocyclic C⁻C double bond, with p-bromophenyl nitrile oxide yielding only one spiroisoxazoline, has been studied within the molecular electron density theory (MEDT) at the MPWB1K/6-311G(d,p) computational level. Analysis of the conceptual density functional theory (CDFT) reactivity indices and the global electron density transfer (GEDT) account for the non-polar character of this zwitterionic-type 32CA reaction, which presents an activation enthalpy of 13.3 kcal·mol-1. This 32CA reaction takes place with total ortho regioselectivity and syn diastereofacial selectivity involving the exocyclic C⁻C double bond, which is in complete agreement with the experimental outcomes. While the C⁻C bond formation involving the ß-conjugated carbon of α-santonin derivative is more favorable than the C⁻O one, which is responsible for the ortho regioselectivity, the favorable electronic interactions taking place between the oxygen of the nitrile oxide and two axial hydrogen atoms of the α-santonin derivative are responsible for the syn diastereofacial selectivity.