The ultimate aim of the present work is to establish an acceptable level of computation for the van der waals (vdw) complexes that is able to pick up appreciable amount of dispersion interaction energy, reproduce the equilibrium separation within the acceptable limits and at the same time cost and time effective. In order to reach this aim vdw clusters where pure isotropic dispersion interaction occur, namely, Ar dimer and trime were investigated. Computations using different basis sets and at different levels of theory have been carried out. Three basis sets, namely, the 6-31++G ** , the 6-311++G ** and the aug-cc-pvdz basis set, were found superior to all other basis sets used. The high performance and relative small CPU time of the 6-31++G ** basis set make it a good candidate for use with large vdw clusters, especially those of interest in biology. Three compound methods were applied in the present work, namely G1, G2 and G2 Moller-Plesset (MP2) and the complete basis set method, CBS-Q. These methods failed to detect the attraction dispersion interaction in the dimer. The predicted repulsive interaction seems dominant in all these methods. Some of the recently developed Density Functional Theory (DFT) methods that were parameterized to account for the dispersion interaction were also evaluated in the present work. Results come to the conclusion that, in contrast to the claims made, state-of-theart Density Functional Theory methods are incapable of accounting for dispersion effects in a quantitative way, although these methods predict correctly the inter-atomic separations and are thus considered a real improvement over the conventional methods. BS-SE has been computed, analyzed and discussed.
The present study presents a thorough theoretical analysis of the electronic structure and conformational preference of the Schiff's base ligand N,N-bis(2-hydroxybenzilidene)-2,4,6-trimethyl benzene-1,3-diamine (H 2 L) and its metal complexes with Zn 2+ , Cu 2+ and Ag + ions. The study aims to investigate the behavior of H 2 L and the binuclear Zn 2+ complex (1), as uorescent probes for the detection of metal ions (Zn 2+ , Cu 2+ and Ag + ) using Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TDDFT). The six conformers of the H 2 L ligand were optimized using B3LYP/6-311++G** level of theory, while the L -2 -metal complexes were optimized by applying B3LYP functional with LANL2DZ/6-311++G** mixed basis set. The gas-phase and solvated Enol-cis isomer (E-cis) was found to be the most stable species. The absorption spectra of E-cis isomer and its metal complexes were simulated using B3LYP, CAM-B3LYP, M06-2X and ωB97X functionals with a 6-311++G** basis set for C, O, N and H atoms and LANL2DZ basis set for the metal ions (Zn 2+ , Cu 2+ and Ag + ). The computational results of B3LYP functional were in excellent agreement with the experimental ones. Hence, it has been adopted for performing the emission calculations. The results indicated that, the metal complex (1) can act as a uorescent chemosensor, for the detection of Ag + and Cu 2+ ions through the mechanism of the Intermolecular Charge Transfer (ICT) and as a molecular switch "On-Off-On" via the replacement of Cu 2+ by Ag + ions, as proved experimentally.
<p>The X-ray spectroscopic signatures of solvated Co<sup>2+</sup> ions mimicking the aqueous solution of CoCl<sub>2</sub> are investigated accounting for multiconfigurational as well as spin-orbit coupling effects. To this end the RASSCF/RASSI methodology with second order corrections due to dynamical correlation (RASPT2) is employed. Emphasis is put on the identification of spectral signatures of different species in octahedral, [Co(H<sub>2</sub>O)<sub>6</sub><sub>-</sub><sub>x</sub>Cl<sub>x</sub>]<sup>(2</sup><sup>-</sup><sup>x)+</sup>, and tetrahedral, [Co(H<sub>2</sub>O)<sub>4</sub><sub>-</sub><sub>x</sub>Cl<sub>x</sub>]<sup>(2</sup><sup>-</sup><sup>x)+</sup>,coordination. X-ray absorption spectra show distinct differences in the L<sub>3</sub> band only. Here, the best agreement is obtained for the hexa-aqua complex [Co(H<sub>2</sub>O)<sub>6</sub>]<sup>2+</sup>. For better identification it is proposed to use RIXS spectroscopy, which shows pronounced species-dependent inelastic features.</p><p><br></p>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.