DFT and TD-DFT Study of Bis[2-(5-Amino-[1,3,4]-Oxadiazol-2-yl) Phenol](Diaqua)M(II) Complexes [M = Cu, Ni and Zn]: Electronic Structures, Properties and Analyses

Abstract

Ground state geometries, spectral (IR and UV-Vis) properties, analysis of frontier molecular orbitals (FMOs), natural bond orbital (NBO) analysis and molecular electrostatic potential (MEP) surfaces of three transition metal complexes [Cu(AOYP)2(OH2)2] (A), [Ni(AOYP)2(OH2)2] (B) and [Zn-(AOYP)2(OH2)2] (C), have been studied theoretically by the Density Functional Theory (DFT) andTime-Dependent Density Functional Theory (TD-DFT) methods. AOYP is the oxadiazole ligand 2-(5-amino-[1,3,4]-oxadiazol-2-yl)phenol. The geometries of these complexes were initially optimized using two basis sets: LAN2DZ and a generic basis set, the latter of which was selected for subsequent analysis. The stability of the complexes arising from intramolecular interactions and electron delocalization was estimated by natural bond orbital (NBO) analysis. The NBO results showed significant charge transfer from lone pair orbitals on the AOYP donor atoms O19, O21, N15 and N36 to central metal ions in the complexes, as well as to the benzene and oxadiazole rings. The electronic spectrum of (A) showed bands at 752 and 550 nm mainly attributable to ligand-tometal charge transfer (LMCT) transitions, and a band at 446 nm assigned to a d-d transition. The electronic spectrum of (B) consisted of bands at 540, 463 and 395 nm mainly due to d-d transitions. Calculated electronic bands for (C) occurred at 243, 238 and 235 nm, arising from intraligand charge transfer (ILCT) transitions within AOYP. A good agreement in terms of band positions was found between experimental and calculated absorption spectra of the complexes.

Aminothiazole-Linked Metal Chelates: Synthesis, Density Functional Theory, and Antimicrobial Studies with Antioxidant Correlations

“…The analysis of frontier molecular orbitals (FMOs) may easily determine a chemical system with its optoelectronic capabilities as well as its capacity to absorb light. The energy differential among the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO, respectively) was closely related to a molecule for its chemical reactivity and kinetic stability . The HOMOs, which are electronically filled orbitals, have the option to contribute electrons, whereas the LUMOs, which are electronically vacant or unoccupied orbitals, have the potential to receive electrons.…”

“…Any chemical system with its physical and chemical characteristics may be investigated using molecular electrostatic potential (MEP) plots. Such maps can be used to understand the potential for nucleophiles or electrophiles to engage at more suitable locations in chemical species . The MEP surfaces have distinct hues such as green, orange, blue, red, and yellow that show the magnitudes of electrostatic potential within the chemical structures.…”

“…Such maps can be used to understand the potential for nucleophiles or electrophiles to engage at more suitable locations in chemical species. 42 The MEP surfaces have distinct hues such as green, orange, blue, red, and yellow that show the magnitudes of electrostatic potential within the chemical structures. The colors in their ranges as red > orange > yellow > green > blue were discovered to be the ascending order of magnitude of electrostatic potential.…”

Computational Analysis of a Series of Chlorinated Chalcone Derivatives

“…Full unconstrained molecular geometry optimizations of 16 chalcones were carried out using Wavefunction Spartan'18 software [42] using the exchange correlation functional by Becke [43] with gradient-corrected correlation provided by Lee, Yang and Parr [44] with the 6-31G* basis set. This DFT method was chosen since it is fast, less computationally intensive, takes electron correlation into account, and provides accuracy in reproducing experimental data [45]. chalcones.…”

Computational Analysis of Theacrine, a Purported Nootropic and Energy-Enhancing Nutritional Supplement

“…Full unconstrained molecular geometry optimizations of theacrine and caffeine were carried out using Wavefunction Spartan '16 software [33] using the exchange correlation functional by Becke [34] with gradient-corrected correlation provided by Lee, Yang and Parr [35] with the 6-31G* basis set. This DFT method was chosen since it is fast, less computationally intensive, takes electron correlation into account, and provides accuracy in reproducing experimental data [36]. Figure 2.…”