Metalloporphyrin reduced C70 fullerenes as adsorbents and detectors of ethenone; A DFT, NBO, and TD-DFT study.

In the present work, the structure and electronic properties of Ti-, Cr-, Fe-, Ni-, Zn-, and Cu-inserted in porphyrin-reduced C70 fullerenes (TM-PIC70Fs) and their interactions with the ethenone were studied using DFT, NBO, and TD-DFT at CAM-B3LYP/6-31G(d) level of theory. 2.89-3.83 and 4.02-4.56 eV were obtained for the HOMO-LUMO gap energies and work functions of TM-PIC70Fs, respectively, compared with 3.76 and 4.54 eV for PIC70F. Among considered TM-PIC70Fs, the adsorption of the ethenone on Ti-PIC70F appreciably changed the HOMO-LUMO energy gap and work function. Consequently, Ti-PIC70F may be used as the ethenone's electronic conductivity and work function types sensor. According to calculated UV-visible spectra, the ethenone adsorption may change the color of Fe- and Ti-PIC70Fs. Therefore, they can be used as color-changing sensors of ethenone. In addition, Ti-, Cr-, Fe-, and Zn-PIC70Fs can be employed as suitable adsorbents of ethenone. Among proper sensors and adsorbents of ethenone, Cr-, Fe-, and Zn-PIC70Fs may be recovered and reused.

Water-vapochromic behavior of a mononuclear Pd(II) complex of piroxicam: A DFT and TD-DFT study.

The vapochromic behavior of a mononuclear Pd(II) complex with piroxicam ligands (trans-[Pd(Pir)2] (Pir- is piroxicam anion)) in the presence of water vapor has been theoretically investigated using the time-dependent density functional theory (TD-DFT). The structure of Pd(II) complex interacting with different number of water molecules (n = 1-5) was optimized, separately. The electronic absorption spectra of the optimized structures were calculated using the TD-DFT method and the changes in the absorption spectrum of complex with the increase in the number of water molecules were followed. Comparison of the absorption spectrum of bare Pd(II) complex with those of its hydrated forms with different numbers of water molecules showed a considerable change in the region of 360-400 nm including the change in the intensity and peak position. The main electronic configurations of the intense absorption lines in the related absorption spectra were determined so that the molecular orbitals involved in these absorption lines were determined. The natural bonding orbital (NBO) analysis was performed to assign the NBOs contributing to these molecular orbitals and to see how the NBO composition of the involved molecular orbitals in the electron excitation change with the number of water molecules. It was observed that the change in the intensity and position of the inter- and intraligand π→π∗ transitions are responsible for the color change. Also, based on the NBO results, the contribution of the electronic transitions involving the Pd(II) ion in the color change of the complex was absent.

Directional affinity of a spherical Gold nanoparticle for the adsorption of DNA bases.

In this work, the adsorption activities of different facets of a spherical gold nanoparticle (Au(111), Au(100) and Au(110)) for adenine (ADE) and cytosine (CYT) in two different environments including gas phase and in the presence of solvent (water) have been investigated, separately. It has been found that the adsorption energy (Ead) and geometry of the DNA bases depend strongly on the kind of nanoparticle facet. The Au (110) facet showed the highest adsorption affinity for the ADE and CYT in both gas phase and water compared to Au(111) and Au(100) facets. Comparison of the Eads of bases calculated in the gas phase with those obtained in the presence of water showed that the electrostatic field of solvent decreases the Eads of bases, especially, for the Au (110) facet. The adsorption geometry of the CYT showed strong dependency on the kind of nanoparticle facet compared to ADE. Also, it has been shown that the direction and amount of charge transfer (CT) between the molecule and nanoparticle strongly depends on the kind of nanoparticle facet and environment. The CT is from the Au (111) facet to the ADE while the CT direction is reversed when the ADE is adsorbed on the Au (110) and Au (100) facets in the gas phase. The CT is from the CYT to three facets in the gas phase while its direction for the ADE and CYT adsorbed on Au (100) facet is reversed. The atoms in molecules (AIM) analysis has been employed to determine the bond paths (BPs) and bond critical points (BCPs) between the bases and facets. The infrared (IR) spectra of the bases adsorbed on the selected facets were calculated and compared with each other and with the spectra of the isolated bases. It was found that the symmetric and unsymmetric stretching of the NH of NH2 group, C-H stretching of the rings and CO stretching of bases can be used for the discrimination of the selected facets.

Evaluation of one-dimensional potential energy surfaces for prediction of spectroscopic properties of hydrogen bonds in linear bonded complexes.

This work evaluated the reliability of the one-dimensional potential energy surface for calculating the spectroscopic properties (rovibrational constants and rotational line energies) of hydrogen bonds in linear bonded complexes by comparing theoretical results with the corresponding experimental results. For this purpose, two hydrogen bonded complexes were selected: the HCN···HCN homodimer and the HCN···HF heterodimer. The one-dimensional potential energy surfaces related to the hydrogen bonds in these complexes were calculated using different computational methods and basis sets. The calculated potential curve of each complex was fitted to an analytical one-dimensional potential function to obtain the potential parameters. The obtained analytical potential function of each complex was used in a two-particle Schrödinger equation to obtain the rovibrational energy levels of the hydrogen bond. Using the calculated rovibrational levels, the rovibrational spectra and constants of each complex were calculated and compared with experimental data available from the literature. Compared with experimental data, the calculated one-dimensional potential energy surface at the QCISD/aug-cc-pVDZ level of theory was found to predict the spectroscopic properties of hydrogen bonds better than the potential curves obtained using other computational methods, especially for the HCN···HCN homodimer complex. Generally, the results obtained for the HCN···HCN homodimer complex were closer to experimental data than those obtained for the HCN···HF heterodimer complex. The investigation performed in this work showed that the one-dimensional potential curve related to the hydrogen bond between two linear molecules can be used to predict the spectroscopic constants of hydrogen bonds. Graphical abstract Potential energy curves of HCN···HCN and HCN···HF complexes calculated at the different computational levels.

Rovibrational energy and spectroscopic constant calculations of complexes pairing via dihydrogen bonds.

In the present investigation, we performed a thorough study of potential energy curves, rovibrational spectra, and spectroscopic constants for complexes pairing via dihydrogen bonds. In particular, we dealt with LiH···HX (X = F, CN, CCH, CCF, CCCl) complexes by employing accurate electronic energy calculations at the MP2/aug-cc-pVDZ level of theory. Following this, the Numerov method was applied to solve the nuclear Schrödinger equation, thus obtaining spectroscopic constants and rovibrational spectra. Good linear correlation between the magnitudes of the interaction energies for interaction of HX with LiH, and the most positive electrostatic potentials of hydrogen in HX, was established.