Density functional theory (DFT) calculations, regardless of the exchange-correlation functional, have long failed to reproduce the observed dz21 ground state of the [NiIII(TtBuP)(CN)2]- anion (where TtBuP is the strongly ruffled tetra(tbutyl)porphyrin ligand), predicting instead a dx2-y21 ground state. Normally, such failures are associated with DFT calculations on spin states of different multiplicity, which is not the case here. The calculations reported here strongly suggest that the problem does not lie with DFT. Instead environmental factors need to be taken into account, such as counterions and solvents. Counterions such as K+ placed against the cyanide nitrogens and polar solvents both result in a dz21 ground state, thus finally reconciling theory and experiment.
The data presented in this paper are related to the research article entitled "Novel dichloro(bis{2-[1-(4-methylphenyl)-1H-1,2,3-triazol-4-yl-κN3]pyridine-κN})metal(II) coordination compounds of seven transition metals (Mn, Fe, Co, Ni, Cu, Zn and Cd)" (Conradie et al., 2018) [1]. This paper presents characterization and structural data of the 2-(1-(4-methyl-phenyl)-1H-1,2,3-triazol-1-yl)pyridine ligand (L2) (Tawfiq et al., 2014) [2] as well as seven dichloro(bis{2-[1-(4-methylphenyl)-1H-1,2,3-triazol-4-yl-κN3]pyridine-κN})metal(II) coordination compounds, [M(L2)2Cl2], all containing the same ligand but coordinated to different metal ions. The data illustrate the shift in IR, UV/VIS, and NMR (for diamagnetic complexes) peaks when L is coordinated to the metals, as well as the influence of the different metals on the peak positions. Solid state structural data is presented for M = Ni and Zn, while density functional theory calculated energies, structures and optimized coordinates are provided for the lowest energy cis and trans conformations for L2 as well as [M(L2)2Cl2] with M = Mn, Fe, Co, Ni, Cu, Zn and Cd.
Abstract Context Bis(terpyridine)manganese(III) exhibits Jahn–Teller distortion due to the inequivalent occupation of the degenerate e g orbitals of this high-spin d 4 pseudo octahedral complex. Due to the spatially constrained nature of the terpyridine ligand, the central Mn-N bonds will always be shorter than the Mn-N terminal bonds, making it more difficult to distinguish between compression and elongation Jahn–Teller structures for bis(terpyridine)manganese(III). Density functional theory (DFT) calculations were utilized as a tool to evaluate the type of Jahn–Teller distortion in the high-spin d 4 bis(terpyridine)manganese(III). The nature of the Jahn–Teller distortion calculated does depend upon the choice of density functional approximation (DFA) with the B3LYP, M06, and OLYP-D3 DFAs giving compression and the PW6B95D3, MN15, and MN15-D3 DFAs giving elongation in gas-phase calculations. All solvent-phase calculations yield an elongated structure for the bis(terpyridine)manganese(III) compound, which is yet to be structurally characterized experimentally. However, both gas and solvent OLYP-D3 calculations result in a compressed structure for the only experimentally isolated and characterized bis(terpyridine)manganese(III) complex, specifically the complex with terpyridine = 4′-(4-methylphenyl)-2,2′:6′,2′′-terpyridine. This alignment with the experimentally observed compression Jahn–Teller structure enhances the credibility of OLYP-D3 calculations in reproducing the observed geometries. The compressed Jahn–Teller geometries were near D 2d symmetry with the z -axis for compression defined along the Mn-N central bonds. Elongation Jahn–Teller distortion is not possible along the Mn-N central bonds, due to their spatially constrained nature. Thus, elongation occur along one pair of opposite Mn-N terminal bonds that are longer than the other pair of opposite terminal bonds, with shorter central bonds. The highest symmetry of the elongation Jahn–Teller distortion geometry of bis(terpyridine)manganese(III) is C 2v . Criteria to distinguish between a compression and elongation Jahn–Teller geometry for bis(terpyridine)manganese(III) are identified. The nature of the singly occupied e g molecular orbital, exhibiting anti-bonding interaction with the nitrogen-p MOs involved, dictates the type of Jahn–Teller distortion that occurs. The low-energy occupied bonding t 2g molecular orbitals establish bonds with and undergo mixing with the ligand molecular orbitals. The OLYP-D3 functional is recommended for calculating bis(terpyridine)manganese(III) and related compounds due to its consistent generation of metal–ligand bonds slightly longer than observed in experiments, in line with the required behavior. Additionally, OLYP-D3 offers a realistic electronic structure for Jahn–Teller distorted bis(terpyridine)manganese(III), correctly identifying alpha e g molecular orbitals as the highest occupied molecular orbital and lowest unoccupied molecular orbital in agreement with experimental electrochemical studies. Furthermore, OLYP-D3 accurately reproduces the experimental compression geometry for the only structurally known bis(terpyridine)manganese(III) compound, instilling confidence in its reliability for such calculations. Methods DFT geometry optimization and frequency calculations were done on the two different modes of Jahn–Teller distortion of bis(terpyridine)manganese(III), using the OLYP, B3LYP, M06, PW6B95D3, and MN15 functionals, with and without the Grimme’s D3 dispersion correction, and the 6-311G(d,p) or def2TZVPP basis set, as implemented in Gaussian 16. All optimizations were in the gas phase and also in the solvent phase with CH 3 CN as implicit solvent using IEFPCM. Graphical Abstract DFT calculations were utilized to determine the Jahn–Teller effect on the geometry of high-spin d 4 bis(terpyridine)manganese(III) complex containing two structurally constrained tridentate ligands.
DFT(PW91/TZP) calculations, including full geometry optimizations, have been carried on [FeII(P)(NO2)]-, FeIII(P)(NO2), [FeII(P)(NO2)(py)]-, FeIII(P)(NO2)(py), [FeIII(P)(NO2)2]-, and FeIII(P)(NO2)(NO), where P is the unsubstituted porphine dianion, as well as on certain picket fence porphyrin (TPivPP) analogues. The bonding in [FeII(P)(NO2)]- and FeIII(P)(NO2), as well as in their pyridine adducts, reveals a σ-donor interaction of the nitrite HOMO and the Fe dz2 orbital, where the Fe−Nnitro axis is defined as the z direction and the nitrite plane is identified as xz. Both molecules also feature a π-acceptor interaction of the nitrite LUMO and the Fe dyz orbital, whereas the SOMO of the Fe(III)−nitro complexes may be identified as dxz. The Fe(III)−nitro porphyrins studied all exhibit extremely high adiabatic electron affinities, ranging from about 2.5 eV for FeIII(P)(NO2) and FeIII(P)(NO2)(py) to about 3.4 eV for their TPivPP analogues. Transition-state optimizations for oxygen-atom transfer from FeIII(P)(NO2) and FeIII(P)(NO2)(py) to dimethyl sulfide yielded activation energies of 0.45 and 0.77 eV, respectively, which is qualitatively consistent with the observed far greater stability of FeIII(TPivPP)(NO2)(py) relative to FeIII(TPivPP)(NO2). Addition of NO to yield {FeNO}6 nitro−nitrosyl adducts such as Fe(P)(NO2)(NO) provides another mechanism whereby Fe(III)−nitro porphyrins can relieve their extreme electron affinities. In Fe(P)(NO2)(NO), the bonding involves substantial Fe−NO π-bonding, but the nitrite acts essentially as a simple σ-donor, which accounts for the relatively long Fe−Nnitro distance in this molecule.
In view of the important role of dithizone in trace metal analyses, new structural aspects and approaches used to probe metal complexes of dithizone are of interest. Three X-ray diffraction structures are reported, dichloridobis(dithizonato)tin(IV), dichlorido(dithizonato)antimony(III), and bis(dithizonato)copper(II). During synthesis of the tin complex, auto-oxidation of SnIICl2 to SnIV occurred without chloride liberation. The SbIII complex revealed a unique distorted see-saw geometry which is, as for the other complexes, predicted by DFT molecular orbital calculations. The computed products of the lowest energy reactions are in agreement with experimentally obtained reaction products, which, together with molecular orbital renderings serve as a tool toward prediction of modes of coordination in these complexes. The S–M–N bond angle in the five-membered coordination ring shows a linear relationship with the corresponding metal ionic radii.
The prominent benefit of granite is owned to its physicochemical property and ubiquitous nature. Vast application of granite which also includes its use as an adsorbent in environmental remediation practice, can also be enhanced. To further enhanced the uptake capacity of granite, nanocomposite consisting of multiwall carbon nanotubes (MWCNTs) and granite was fabricated and further modified using Dialiumguineensestem bark extract. The structure and composition of pristine granite (PG) and modified nanocomposite granite (G) based material were examined and confirmed by the FTIR, Raman, TGA, SEM and XRD. Meanwhile, the specific surface areasof PG (1.268 m2/g) and G (16.57 m2/g) were obtained using the BET surface area analyser. The optimization step revealed that the uptake capacities of PG and G were dependent on solution pH, sorbent dose and contact time. Meanwhile, pseudo-second-order and Elovich kinetic models were noticed to best describe the data for the removal of Cr (VI) by PG and G. Equilibrium isotherm study revealed that Freundlich and Langmuir models fitted well to the experimental data obtained for the uptake of Cr(VI) onto PG and G respectively. Furthermore, electrostaticattraction betweentheDialiumguineense stem bark extract on the surface of G and Cr(VI) influenced the uptake of Cr(VI). On the other hand, the interaction between the plant extract and Cr(VI) may result in the attenuation of Cr(VI) via reduction to Cr(III). Finally, the thermodynamically favoured adsorptive process demonstrated high adsorbent reusability with good stability for Cr(VI) uptake.
A theoretical (DFT) study of the equilibrium geometry of the possible reaction products of the oxidative addition reaction [Rh(FcCOCHCOCF 3 )(CO)(PPh 3 )] + CH 3 I (Fc = ferrocenyl), consistent with experimental observations, revealed that the first alkyl product results from trans addition to RhI. Isomerization via an acyl intermediate leads to a second octahedral alkyl product with the PPh 3 group and the iodide above and below the square plane. Theoretical computations also revealed that the thermodynamic acyl product adopts a square-pyramidal geometry with the COCH 3 group in the apical position. Keywords: DFT, computational, rhodium, β-diketone, NMR PDF and Supplementry file attached
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