Inclusive DFT Insight into Sensing Mechanism of Cyclotetrapyrole Towards Lung Irritants

The development of smart sensing devices for toxic analytes detection especially lung irritants is much essential. The cyclic conducting polymers having infinite 𝜋-conjugation are proved to be highly sensitive for toxic analytes. Herein, by using the DFT approach, we investigated the sensing mechanism of cyclotetrapyrole (CTPy) for accurate detection of phosgene, diphosgene, chloropicrin and chlorine at the B3LYP-D3/6-31+ G (d, p) level. The calculated interaction energies show the physisorption of lungs irritants over the CTPy surface. Natural bond orbital (NBO) and charge decomposition (CDA) analyses predict charge transfer interactions in the complexes. The reduced density gradient (RDG) approach reveals that charge transfer electrostatic hydrogen bonding interactions dominate in the complexes. The sensitivity of CTPy towards lung irritants is further illustrated by the reduction in HOMO-LUMO energy gaps, red shifting of \({{\lambda }}_{\text{m}\text{a}\text{x}}\) in UV–Visible specta. Density of state (DOS) analysis affirm that enhanced conductivity upon complexation is due to the origination of new energy states in occupied and virtual orbitals nearer to the Fermi level. Moreover, PDOS spectra show that CTPy primarily contributes to the energy of HOMO. The outcome of the current study depicts appreciable sensitivity of CTPy towards lung irritants. We believe that the upshot of the current findings and their forecasts will provide useful guidelines for an experimentalist to design highly sensitive sensors for toxic analytes using CTPy.

Energetic and Geometric Characteristics of the Substituents: Part 2: The Case of NO2, Cl, and NH2 Groups in Their Mono-Substituted Derivatives of Simple Nitrogen Heterocycles

Variously substituted N-heterocyclic compounds are widespread across bio- and medicinal chemistry. The work aims to computationally evaluate the influence of the type of N-heterocyclic compound and the substitution position on the properties of three model substituents: NO2, Cl, and NH2. For this reason, the energetic descriptor of global substituent effect (Erel), geometry of substituents, and electronic descriptors (cSAR, pEDA, sEDA) are considered, and interdependences between these characteristics are discussed. Furthermore, the existence of an endocyclic N atom may induce proximity effects specific for a given substituent. Therefore, various quantum chemistry methods are used to assess them: the quantum theory of atoms in molecules (QTAIM), analysis of non-covalent interactions using reduced density gradient (RDG) function, and electrostatic potential maps (ESP). The study shows that the energetic effect associated with the substitution is highly dependent on the number and position of N atoms in the heterocyclic ring. Moreover, this effect due to interaction with more than one endo N atom (e.g., in pyrimidines) can be assessed with reasonable accuracy by adding the effects calculated for interactions with one endo N atom in substituted pyridines. Finally, all possible cases of proximity interactions for the NO2, Cl, and NH2 groups are thoroughly discussed.

Structural, surface, and computational analysis of two vitamin-B1 crystals with sulfonimide-based anions

Two crystals incorporating the thiamine·HCl cation and the fluorinated anion 1,3-disulfonylhexafluoropropyleneimide have been characterized via single-crystal X-ray diffraction. The host-guest interactions of thiamine with the anions are analyzed and characterized using Hirshfeld surface analysis. The cations in both structures form a dimer in the solid-state via reciprocal hydrogen bonding through the amine and hydroxyl moieties. Additional investigation into the interactions responsible for dimer formation found that the sulfur atom in the thiazolium ring interacting with several hydrogen atoms to form stabilizing interactions. These interactions in the dimer are further analyzed using reduced density gradient analysis and the results are correlated to the fingerprint plots derived from the Hirshfeld surfaces. Moreover, specific interactions are observed from the cyclical anions, with both the fluorine and sulfonyl oxygen atoms participating in bridging interactions, displaying the diverse host-guest properties of thiamine.

Halogen Interactions in Halogenated Oxindoles: Crystallographic and Computational Investigations of Intermolecular Interactions

X-ray structural determinations and computational studies were used to investigate halogen interactions in two halogenated oxindoles. Comparative analyses of the interaction energy and the interaction properties were carried out for Br···Br, C-H···Br, C-H···O and N-H···O interactions. Employing Møller–Plesset second-order perturbation theory (MP2) and density functional theory (DFT), the basis set superposition error (BSSE) corrected interaction energy (Eint(BSSE)) was determined using a supramolecular approach. The Eint(BSSE) results were compared with interaction energies obtained by Quantum Theory of Atoms in Molecules (QTAIM)-based methods. Reduced Density Gradient (RDG), QTAIM and Natural bond orbital (NBO) calculations provided insight into possible pathways for the intermolecular interactions examined. Comparative analysis employing the electron density at the bond critical points (BCP) and molecular electrostatic potential (MEP) showed that the interaction energies and the relative orientations of the monomers in the dimers may in part be understood in light of charge redistribution in these two compounds.

Molecular Structure, Interactions and Antimicrobial Properties of Curcumin-PLGA Complexes – A DFT Study

Density functional calculations are performed to study the molecular structure, interactions, and antimicrobial activity of curcumin-poly Lacto glycolic acid (Cur-PLGA) complexes. The calculations are performed on curcumin, Glycolic acid (SSC and AAT conformers), Lactic acid (LA), Cur-SSC, Cur-AAT, Cur-LA, and Cur-PLGA complexes using dispersion corrected M06-2X functional with 6–31 + G* basis set. The condensed Fukui functions of curcumin are calculated to identify the favorable reactive sites. Inter- and intramolecular H–bond interactions are analyzed in detail through natural bond orbital, Atoms in Molecule, and Reduced density gradient analyses. The interaction energy values indicate that the interaction between curcumin and AAT is stronger than the other studied complexes. Further, our calculations show that the PLGA interacted with curcumin is having lower LUMO energy and density values. This indicates that the antimicrobial activity is high in this complex.

Vibrational Spectral Studies, Quantum Mechanical Properties, and Biological Activity Prediction and Inclusion Molecular Self-Assembly Formation of N-N’-Dimethylethylene Urea

A cyclic urea analog, N-N'-dimethylethylene urea, was studied using different spectral methods like FT-IR, FT-Raman, and UV-VIS methods followed by computational simulations. The experimental and simulated spectra are compared, and a detailed assignment of vibrations and potential energy distribution is made. It was followed by various quantum mechanical studies like frontier orbital analysis, energy descriptors, average local ionization energies, and nonlinear optical properties. The NBO gave an insight into the various intramolecular stabilizing electron delocalization by hyperconjugation. Noncovalent interaction analysis provided various types of interactions present in the molecule. We also studied ALIE, local information entropy, electron localized function, reduced density gradient studies, localized orbital locator studies, and other analyses. Molecular docking results indicated that this urea derivative acted as an ATP-hydrolysing inhibitor, and the drug delivery ability of cyclodextrin on NND was tested by forming an inclusion complex with both compounds with dispersion and without dispersion interaction.

A DFT Investigation of The Host-Guest Interactions Between Boron-Based Aromatic Systems and β-Cyclodextrin

Density-functional theory calculations including dispersion at BLYP-D3(BJ)/def2-SVP level of theory were performed for a series of systems based on cyclodextrin complexation with boron-based aromatic compounds. Elaborated investigations were carried out using different quantum chemical parameters such as computed complexation energies, theoretical association constants and natural bond orbital (NBO) analysis. Several configurations and inclusion modes were considered in this work. The calculated complexation energies were consistent with the experimental classification of these systems on the basis of occurring interactions. Reduced density gradient (RDG) and independent gradient model (IGM) approaches determined the nature and strength of non-covalent interactions which played a central role in the formation of the complexes. Thus, phenylboronic acid (PBA) and benzoxaborole (Bxb) act mainly as hydrogen-bonded complexes with β-cyclodextrin, while mainly Van der Waals (vdW) interactions stabilize both catechol (PhBcat) and pinacol esters of phenylboronic acid (PhBpin) complexes. The ferroceneboronic acid (FcBA) exhibits a mixture of H-bonds and vdW interactions with β-cyclodextrin.

Synthesis and detailed characterization of a newly synthesized chalcone, 3-(2,5-dimethoxyphenyl)-1-(naphthalen-2-yl)prop-2-en-1-one

Chalcones are the main component of some natural compounds. The title compound, 3-(2,5-dimethoxyphenyl)-1-(naphthalen-2-yl)prop-2-en-1-one, was synthesized and characterized. The compound (C21H18O3) crystallizes in the triclinic system with the space group of P-1 (no. 2), a = 7.7705(4) Å, b = 10.2634(6) Å, c = 11.2487(6) Å, α = 79.655(5)°, β = 81.500(5)°, γ = 68.039(5)°, V = 815.28(9) Å3, Z = 2, T = 293(2) K, μ(MoKα) = 0.086 mm-1, Dcalc = 1.297 g/cm3, 9126 reflections measured (4.318° ≤ 2Θ ≤ 52.728°), 3302 unique (Rint = 0.0466, Rsigma = 0.0528) which were used in all calculations. The final R1 was 0.0568 (I > 2σ(I)) and wR2 was 0.1667 (all data). The crystal structure is stabilized by both short C-H···O inter- and intra-molecular interactions. In addition, the crystal structure is reinforced by π-π interactions. Hirshfeld surface analysis confirmed the presence of C-H···O intermolecular interactions. The two-dimensional fingerprint plots are used to visualize the individual interactions present in the molecule. DFT calculations were performed to know the energy levels of the frontier molecular orbitals (HOMO-LUMO). The energy gap between the frontier molecular orbitals shows the kinetic stability of the molecule. The chemical reactive sites are observed by generating MEP surface. Non-covalent interactions (NCIs) are analyzed using reduced density gradient (RDG) analysis.