Density functional theory (DFT) investigation of molecular structure and frontier molecular orbitals (FMOs) of P-N,N-dimethylaminobenzylidenemalononitrile (DBM)

Carbon and boron nitride quantum dots as optical sensor probes for selective detection of toxic metals in drinking water: a quantum chemical prediction through structure- and morphology-dependent electronic and optical properties

Toxic metals present in drinking water pose a serious threat to the environment and human beings when present in abundance. In this work, we investigated the sensing ability of quantum dots (pristine CQDs, boron/nitrogen/sulphur (B/N/S)-doped CQDs, and BNQDs) of various sizes and morphologies (rectangular, circular, and triangular) towards toxic metals such as arsenic (As), cobalt (Co), nickel (Ni), copper (Cu), and lead (Pb) using quantum chemical density functional theory calculations in both gas and water phases. We probed the structural, electronic, and optical properties of the QDs. All the modelled QDs are energetically stable. Frontier molecular orbital analysis predicted that BNQDs are more chemically stable than all other CQDs. UV-vis absorption and Raman spectra analyses helped to understand the optical properties of all the QDs. Further, adsorption studies revealed that triangular pristine CQDs and sulphur-doped CQDs show higher adsorption affinity towards the toxic metals. The magnitude of adsorption energies follows the trend Ni > Pb > As > Cu > Co in most of the QDs. Several pristine and doped CQDs exhibited chemisorption towards the toxic metals, and hence, they can be used as adsorbents. However, a majority of BNQDs showed physisorption towards the metals, and therefore, they can be used as efficient optical sensors compared to CQDs. Further, the sensing ability of the QDs was explored through optical phenomena such as changes in UV-vis absorption spectra and fluorescence after metal adsorption. When compared to pristine CQDs and B/N/S-doped CQDs, metal complexation caused significant changes in the UV-vis absorbance peak intensities in BNQDs along with peak shifts. Moreover, metal interaction with the QDs increased their fluorescence lifetime with the highest values observed in Co-adsorbed triangular H18C46 (152.30 ns), Pb-adsorbed rectangular H15C30S (21.29 ns), and As-adsorbed circular B27N27H18 (2.99 μs) among pristine CQDs, B/N/S-doped CQDs, and BNQDs, respectively. Overall, we believe that our first-of-its-kind computational prediction of the optical sensing ability of tailor-made zero-dimensional systems such as QDs will be a great aid for experimentalists in designing novel and rapid optical probes to detect toxic metals in drinking water.

Wojcik M. Impact of non-covalent interactions on FT-IR spectrum and properties of 4-methylbenzylammonium nitrate. A DFT and molecular docking study

In this research, the impact of non-covalent interactions on the FT-IR spectrum and structural, electronic, topological and vibrational properties of hybrid 4-methylbenzylammonium nitrate (4MBN) have been studied combining B3LYP/CC-PVTZ calculations with molecular docking. 4MBN was synthesized and characterized by using the FT-IR spectrum while the optimized structures in gas phase and in ethanol and aqueous solutions have evidenced monodentate coordination between the nitrate and methylbenzylammonium groups, in agreement with that experimental determined for this species by X-ray diffraction. Here, non-covalent interactions were deeply analyzed in terms of topological parameters (AIM), electron localization function (ELF), localized orbital locator (LOL), Hirshfeld surface and reduced density gradient (RDG) method. Weak interactions such as H-bonds, VDW and steric effect in 4MBN were visualized and quantified by the independent gradient density (IGM) based on the promolecular density. The hyper-conjugative and the delocalization of charge in 4MBN have been elucidated by natural bonding orbital (NBO) while its chemical reactivity was studied and discussed by using molecular electrostatic potential surface (MESP), frontier molecular orbital (FMOs), density of state (DOS) and partial density of state (PDOS). The complete vibrational assignments of 69 vibration modes expected for 4MBN are reported together with the scaled force constants while the electronic transitions were evaluated by TD-DFT calculations in ethanol solution. Thermal analysis (DTA and DSC) was also determined. Molecular docking calculations have suggested that 4MBN presents biological activity and could act as a good inhibitor against schizophrenia disease.

On the spectroscopic analyses of 3-Hydroxy-1-Phenyl-Pyridazin-6(2H)one (HPHP): A comparative experimental and computational study

We have systematically calculated various physical characteristics such as optimized molecular structural parameters, vibrational frequencies, HOMO-LUMO energy gap, total dipole moment and thermochemical parameters: nuclear repulsion energy, ionization energy, electron affinity, global hardness, electronic chemical potential, global electrophilicity index and finally softness (ζ) using DFT/B3LYP utilizing 6-311G(d,p) basis set for 3-Hydroxy-1-Phenyl-Pyridazin-6(2H)one (HPHP). Also, HPHP nonlinear optical (NLO) properties have been checked by DFT/B3LYP utilizing 6-311G(d,p) basis set. In addition, we have investigated the influence of exposure to UV radiation on HPHP physical properties at the same level of theory. Our results show that HPHP possesses a dipole moment (2.68Debye) and HOMO-LUMO energy gap of 3.99eV that emphasize its high applicability for manufacturing photovoltaic devices such as solar cells. After exposure to UV radiation, the HPHP dipole moment has been lowered from 2.68 to 2.3Debye due to UV radiation. Moreover, a double spin in HPHP has been observed, as electrons are aligned according to their spin state. Electrons (spin ↑) and (spin ↓) are aligned in alpha and beta levels with energy gaps 3.82 and 3.17eV, respectively. This anomalous behavior may be justified by considering that HPHP undergoes anomalous Zeeman-like effect. The presence of this phenomenon in HPHP introduces it as a modern organic semiconductor which has high applicability to be used in modern spintronics.

FT-IR, FT-Raman and DFT quantum chemical study on the molecular conformation, vibrational and electronic transitions of 1-(m-(trifluoromethyl)phenyl)piperazine

The FTIR and FT-Raman spectra of 1-(m-(trifluoromethyl)phenyl)piperazine [TFMPP] have been recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The optimized geometry, frequency and intensity of the vibrational bands of the compound was obtained by the density functional theory using 6-311++G(d,p) basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. A detailed interpretation of the infrared and Raman spectra were also reported based on potential energy distribution (PED). UV-Vis spectrum of the compound was recorded and the electronic properties HOMO and LUMO energies were measured by TD-DFT approach. Furthermore, molecular electrostatic potential is performed and also the calculated HOMO and LUMO energies show that charge transfer occurs within the molecule.