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Investigating the molecular structure, vibration methods, nonlinear optical, electronic and thermo dynamical properties of 2, 4-dichloroaniline (2, 4DCA), 2, 4-difluoroaniline (2, 4DFA) and 2, 4-diiodoaniline (2, 4DIA) gives comparable hypothetical properties to decide a desired material. Density Functional Theories (DFTs) have the basic guidelines to affect the Schrödinger equation for several body systems. Comparison is drawn among theoretical properties like stability and charge delocalization of the molecules which are studied by Natural Bond Orbital (NBO) analysis, Nonlinear Optical (NLO) behavior in terms of first-order hyperpolarizability, Molecular Electrostatic Potential (MEP) and dipole moment of title compounds. The chance of the title atoms being bio-active hypothetically incontestable by the electrophilicity index prompts additional property studies for the chosen compounds. The title molecules are found to suit well with L – glutamate oxidase inhibitor utilizing molecular docking techniques. The outcomes of the chosen organic alkane series are obtained utilizing higher basis set (6-311++G (d, 2p)) to realize results.

The mesogenic behavior and electronic properties of hydrogen bond ferroelectric liquid crystal (HBFLC) complex are studied using experimental and theoretical techniques. HBFLC complex is synthesized from mesogenic 4-hexyloxy benzoic acid (6O BA) as the proton donor and nonmesogenic chiral DL-tartaric acid (DLTA) as the proton acceptor through intermolecular hydrogen bonding. Molecular geometry of DLTA+6O BA HBFLC complex is optimized by density functional theory (DFT) calculation. An interesting observation is that polarizing optical microscope (POM) study confirms that the HBFLC complex exhibits thermochromic behavior in chiral nematic (N${}^{\ast })$ along with induced nontitled smectic G^* phases. Another noteworthy observation is the manifestation of tripartite temperature stages. Fourier-transform infrared spectroscopy (FTIR) and natural bond orbital (NBO) analysis elucidate the intermolecular hydrogen bond between mesogenic (6O BA) and nonmesogenic (DLTA) compounds. Further, frontier molecular orbital (FMO) study and electrostatic potential (ESP) analysis explore the reactivity sites, intermolecular charge transfer and electronic behavior of HBFLC complex.

Interaction of CO and NO molecules by different orientations on (BN)_n=3-5 clusters have been studied at the B3LYP/6-311+G* level of theory. Total electronic energies have been corrected for geometrical counterpoise (gCP) and dispersion (D3) energies at the B3LYP/6-31G* level. Formation of a new sigma bond between the gas and (BN)₃ cluster, atom in molecules (AIM) results, density of states spectrums (DOS), molecular electrostatic potential (MEP) surfaces, and visualization of wave function of molecular orbitals in the nearest bonding regions to the Fermi level have confirmed that adsorption of CO by carbon end atom, and NO by nitrogen end atom is covalent in nature, so that the charge transfer is occurred from gas molecule to the cluster.

Boron isosteres [CH₃-CO-BH-CH(R)-CONHCH₃; R=CH₃,CH₂OH,CH₂SH] of natural amino acids have been designed as inhibitors of serine protease based on boron's ability to mimic the transition state of the normal enzyme catalyzed reaction. The conformation and electronic properties of these isosteres have been determined by ab initio calculations at the HF/6-31G** level of theory. The global minimum energy structures of the boron isosteres (which are all identical) and the natural amino acids are radically different. Interestingly, the boron isosteres have favorable conformations with positive values for the ϕ dihedral, which are "disallowed states" for the natural amino acids. This is possible because of the smaller atomic size of boron compared to nitrogen. The molecular electrostatic potential of the boron isosteres is also very different from the natural amino acids. There is a positive potential around the boron atom, which provokes the attack of the Ser¹⁹⁵–OH group in the enzyme, resulting in formation of an irreversible enzyme-inhibitor adduct.

The FTIR (4000–400cm${}^{-1}$) and the FT-Raman spectra (4000–50cm${}^{-1}$) of 4-Hydroxy-7-methyl-1,8-naphthyridine-3-carboxylic acid are recorded and investigated. The spectra are interpreted using anharmonic frequency computations by VPT2, VSCF and PT2-VSCF methods within DFT/6-311G(d,p) framework. The root mean square (RMS) values indicate that VSCF computed frequencies are in close agreement with the observed frequencies. The combination and overtone bands are also identified in the FTIR spectrum. The intermolecular O-H$\cdots$O hydrogen bonding interactions are discussed in the dimer structure of the molecule. The magnitudes of the coupling between pair of modes are also computed. The electronic spectra in water and ethanol solvents are analyzed using TD-B3LYP/6-311$++$G(d,p) level of theory. Molecular electrostatic potential (MEP) and HOMO-LUMO analysis are also performed.

In this work, a detailed vibrational analysis of L-(-)-xylose molecule has been carried out. The geometrical parameters and anharmonic spectrum have been calculated and compared with XRD, FTIR (4000–400cm${}^{-1}$) and FT-Raman (4000–50cm${}^{-1}$) observed data. The simulated data along with IR and Raman intensities were calculated using DFT/B3LYP level of theory in combination with 6-311$++$G(d,p) basis set. The experimental and theoretical results are found to be in a good agreement with each other. Moreover, thermodynamic properties, molecular electrostatic potential (MEP) and natural bond orbital (NBO) analysis of L-(-)-xylose are also reported. The calculated HOMO and LUMO energies confirm the charge transfer within the molecule.

Nanoclusters such as ${\text{Al}}_{12}$${\text{N}}_{12}$ have received increased attention due to their diverse applications in the fields of optoelectronics and energy storage. In this paper, we have investigated a series of alkaline earth metal (AEM)-encapsulated ${\text{Al}}_{12}$${\text{N}}_{12}$ nanoclusters for hydrogen adsorption. Thermodynamic adsorption parameters, optical and nonlinear optical properties were investigated using density functional theory (DFT) at the B3LYP/6-31G(d,p) level of theory. Encapsulation of AEMs (Be, Mg and Ca) is an effective strategy to improve the NLO reaction and thermodynamic and adsorption properties of ${\text{Al}}_{12}$${\text{N}}_{12}$ nanoclusters. The adsorption energies ranging from $-$26.57kJ/mol to $-$213.33kJ/mol for the three guests (Be, Mg and Ca) capsulated ${\text{Al}}_{12}$${\text{N}}_{12}$ nanoclusters are observed. The adsorption energy is affected by the size of the nanocage. Therefore, Ca- and Mg-encapsulated cages show higher values of adsorption energy. Overall, an increase in adsorption energy ($E_{\mathrm{\text{ad}}}=-31.91$kJ/mol to $-$91.06kJ/mol) is observed for (Be, Mg and Ca) encapsulated ${\text{Al}}_{12}$${\text{N}}_{12}$ nanoclusters compared to untreated ${\text{Al}}_{12}$${\text{N}}_{12}$ and H₂-${\text{Al}}_{12}$${\text{N}}_{12}$ cages. Moreover, adsorption of hydrogen on AEMs encapsulated in ${\text{Al}}_{12}$${\text{N}}_{12}$ leads to a decrease in the HOMO-LUMO energy gap with an enhancement of linear and nonlinear hyperpolarizability. All hydrogen-adsorbed AEMs ${\text{Al}}_{12}$${\text{N}}_{12}$ nanocages exhibit large ${\alpha }_{\mathrm{\text{total}}}$ and $\beta o$ values, suggesting that these systems are potential candidates for optical materials. Various geometrical parameters such as frontier molecular orbitals (FMOs), partial density of states, global quantum descriptor of reactivity, natural bond orbital testing and molecular electrostatic strength analyses were performed to investigate the thermodynamic stability of all the studied systems. The results obtained confirmed that the designed systems are suitable for hydrogen storage. Therefore, we recommend that these systems be investigated for their hydrogen storage and optical properties.

A new Schiff base compound and its derivative, 3-cyclopropyl-4-(4-nitrofuran-1-yl)methyleneamino-4,5-dihydro-1$H$-1,2,4-triazol-5-one (3-CNM) and 1-acetly-3-cyclopropyl-4-(4-nitrofuran-1-yl)methyleneamino-4,5-dihydro-1$H$-1,2,4-triazol-5-one (1-ACNM), were synthesized. The structures of compounds were characterized by ${}^{13}$C-NMR, ¹H-NMR and FT-IR spectroscopy techniques. The antioxidant capacities of the molecules were investigated by different methods (metal chelation, DPPH and reducing power). Some quantum chemical calculations are performed on the B3LYP, B3PW91, MPW1PW91 functionals with the 6-311++G(d,p) level basis set of the density functional theory (DFT). Using the optimized structures of Schiff bases, the frontier molecular orbital, the theoretical spectroscopic and the nonlinear optic (NLO) analysis, the molecular electrostatic potential (MEP) surface, the thermodynamic parameters, the dipole moment, the molecular geometric properties and the total energy were calculated. The calculation results showed that the 3-CNM compound can be used as a suitable and good nonlinear optical compound. In addition, electronegative and electropositive atoms were determined from the MEP surface map. The difference between ($\mathrm{\Delta }E$) the highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO) energies was calculated as 3.3eV and 3.4eV for 3-CNM and 1-ACNM, respectively, and these values express the chemical stability of the molecule and the orbital interactions. This work is important because it includes the synthesis of two new molecules and theoretical calculations that support their experimental properties. It can also provide significant benefits in terms of synthesis of similar Schiff base compounds and their calculated electronic, geometric and thermodynamic properties.