Scalar-relativistic DFT Calculations Research Articles

Indenyl and Allyl Palladate Complexes BearingN‐Heterocyclic Carbene Ligands: an Easily Accessible Class of New Anticancer Drug Candidates

AbstractThe mechanochemical syntheses of allyl and indenyl palladate complexes are reported. All compounds were obtained in quantitative yields and microanalytically pure without the need of any workup. These complexes are stable in chlorinated and polar (DMSO or DMSO/H2O solutions) solvents. In chlorinated solvents, they appear as ionic pairs of which crystals suitable for single X‐ray diffraction studies have been obtained. Bonding and solvation properties are rationalized through scalar relativistic DFT calculations. Moreover, most complexes showed excellent cytotoxicity towards ovarian cancer cell lines, with IC50values comparable or lower than cisplatin. The potent anticancer activity of two IPrCland IPr*‐based palladate complexes was examined in a high‐grade serous ovarian cancer (HGSOC) patient‐derived tumoroid. Moreover, the inhibition of the antioxidant enzyme thioredoxin reductase (TrxR) was noticed, and structure‐activity relationships could be derived, suggesting the ROS detoxifying system is involved in the mode of action.

Iridium(VII)-Corrole Terminal Carbides Should Exist as Stable Compounds.

Scalar-relativistic DFT calculations with multiple exchange-correlation functionals and large basis sets foreshadow the existence of stable iridium(VII)-corrole terminal carbide derivatives. For the parent compound Ir[Cor](C), OLYP/STO-TZ2P calculations predict a short Ir-C bond distance of 1.69 Å, a moderately domed macrocycle with no indications of ligand noninnocence, a surprisingly low electron affinity of ∼1.1 eV, and a substantial singlet-triplet gap of ∼1.8 eV. These results, and their essential invariance with respect to the choice of the exchange-correlation functional, lead us to posit that Ir(VII)-corrole terminal carbide complexes should be isolable and indefinitely stable under ambient conditions.

A Detailed Theoretical Study of Cu3Agm Bimetallic Clusters

In this work, we explored the energy landscape and the effect of increasing the amount of Ag atoms over the segregation of Cu atoms in bimetallic clusters with compositions Cu 3 Ag m (), using a genetic algorithm coupled with the Gupta potential to determine the most stable clusters. According to our results, the Ag atoms determine the magic compositions, which are the Cu 3 Ag 10 , Cu 3 Ag 16 and Cu 3 Ag 20 clusters. In all studied structures, the Cu atom establishes an interface with the Ag atoms or tends to form a core-shell structure with at least one Cu atom on the cluster surface. Scalar relativistic DFT calculations of the magic compositions reveal that these clusters have an electronic behavior similar to their pure Ag analogues. DOI: http://dx.doi.org/10.17807/orbital.v13i3.1536

Relativistic Effects on a Metal-Metal Bond: Osmium Corrole Dimers.

A series of metal-metal bonded osmium corrole dimers, {Os[T pXPC]}2, were synthesized in reasonably good yields (35-46%) via the interaction of the corresponding free-base meso-tris( p-X-phenyl)corroles (H3[T pXPC], X = CF3, H, CH3, and OCH3), Os3(CO)12, and potassium carbonate in 1,2,4-trichlorobenzene under an inert atmosphere at 180 °C over several hours. The complexes are only the second class of Os corroles reported to date (the first being OsVIN corroles) and also the second class of metal-metal bonded metallocorrole dimers (the other being Ru corrole dimers). Comparison of the X-ray structures, redox potentials, and optical spectra of analogous Ru and Os corrole dimers, along with scalar-relativistic DFT calculations, has provided an experimentally calibrated account of relativistic effects in these complexes. Three of the Os corrole dimers (X = CF3, H, and OCH3) were analyzed with single-crystal X-ray diffraction analysis, revealing inversion-related corrole rings with eclipsed Os-N bonds and Os-Os distances of ∼2.24 Å that are ∼0.06 Å longer than the Ru-Ru distances in the analogous Ru corrole dimers. Interestingly, a comparison of scalar-relativistic and nonrelativistic DFT calculations indicates that this difference in metal-metal bond distance does not, in fact, reflect a differential relativistic effect. For a given corrole ligand, the Ru and Os corrole dimers exhibit nearly identical oxidation potentials but dramatically different reduction potentials, with the Os values ∼0.5 V lower relative to Ru, suggesting that whereas oxidation occurs in a ligand-centered manner, reduction is substantially metal-centered, which indeed was confirmed by scalar-relativistic calculations. The calculations further indicate that approximately a third of the ∼0.5 V difference in reduction potentials can be ascribed to relativity. The somewhat muted value of this relativistic effect appears to be related to the finding that reduction of an Os corrole dimer is not exclusively metal-based but that a significant amount of spin density is delocalized over to the corrole ligand; in contrast, reduction of an Ru corrole dimer occurs exclusively on the Ru-Ru linkage. For isoelectronic complexes, the Ru and Os corrole dimers exhibit substantially different UV-vis spectra. A key difference is a strong near-UV feature of the Os series, which in energy terms is blue-shifted by ∼0.55 V relative to the analogous feature of the Ru series. TDDFT calculations suggest that this difference may be related to higher-energy Os(5d)-based LUMOs in the Os case relative to analogous MOs for Ru.

DFT and experimental study of nitrosyl carboxylate palladium clusters Pd4(NO)2(RCO2)6 as catalysts for aerobic oxidation of alcohols

Possible activation pathways for palladium nitrosyl carboxylate complexes Pd4 (μ-NO)2 (μ-RCO2)6 in reaction of catalytic aerobic oxidation of alcohols are reported. The study was carried out using scalar-relativistic DFT calculations for the system palladium nitrosyl acetate (RCH3) + methanol. Exchange-correlation functional PBE was found to be the best choice in terms of accuracy and time for calculations. The main pathway includes dissociation of starting 4-nuclear molecule into binuclear species Pd2(NO) (CH3CO2)3, where nitrosyl group keeps bridging coordination mode. Experimental studies showed that palladium nitrosyl acetate (RCH3) and nitrosyl pivalate (RCMe3) are moderately active catalysts for aerobic oxidation of benzylic alcohol, (E)-2-hexen-1-ol, (−)-menthol, trans-1,3-diphenyl-2-propen-1-ol and dodecanol-1. The addition of pyridine substantially improved the catalysts performance.

Roles of d- and f-orbital electrons in the complexation of Eu(III) and Am(III) ions with alkyldithiophosphinic acid and alkylphosphinic acid using scalar-relativistic DFT calculations

Roles of d- and f-orbital electrons in the complexation of Eu(III) and Am(III) ions with alkyldithiophosphinic acid and alkylphosphinic acid using scalar-relativistic DFT calculations

Insights into metal–ligand and metal–metal interaction in coinage metal triangles. Insights of d10-d10, d10-d8 and d8-d8 contacts from [Au3In(CH3N[dbnd]COCH3)3] (n = 2, 4, 6) via relativistic DFT calculations

The successive addition of one, two and three equivalents of iodide to [Au3(CH3NCOCH3)3], gives rise to the [Au3In(CH3NCOCH3)3] (n=2, 4, 6) oxidized systems. Such structures have been studied by using scalar relativistic DFT calculations and TD-DFT. Our results demonstrate a stronger ligand-to-metal charge donation, which increases in covalency. The long metal–metal contacts observed through the series result from the similarly population of bonding, non-bonding and slightly anti-bonding combinations of the 6s-Au atomic shells in the [Au3]n+ core, leading to distances in the range of the sum of their van der Waals radii for all the systems.

Spin and structural features of oxygen dissociation on tetrahedral Ag20 and Ag19Au clusters.

The spin-crossing mechanism of oxygen dissociation on Ag20 and monodoped Ag19Au clusters was investigated via spin-polarized scalar-relativistic DFT calculations using the PBE, TPSSh, M06L, mPBE, BLYP, OLYP, and B3LYP functionals. In particular, the singlet and triplet O-O bond rupture pathways at vertex-edge and facet-edge sites on the tetrahedral clusters were studied. The calculations reveal that for the Ag20O2 and Ag19AuO2 complexes, the spin inversion from the triplet to singlet state occurs during the last step, which involves O-O bond rupture through a singlet transition state (TS). When spin crossing during oxygen dissociation on the clusters is considered, the activation energies decrease by 10-29 kJ mol(-1); however, they are still high due to the magic nature of the clusters and high vertical spin excitation energies. For these silver clusters, size effects based on the relationship between the TS structure and oxidation activation energy were predicted.

ChemInform Abstract: DFT Study of Uranyl Peroxo Complexes with H2O, F‐, OH‐, CO32‐, and NO3‐.

AbstractStructural and electronic properties of various uranyl peroxo complexes are examined using scalar relativistic DFT calculations considering only complexes in which the peroxo ligands are coordinated to the uranyl moiety in a bidentate mode.

Palladium site ordering and the occurrence of superconductivity in Bi 2Pd 3Se 2− xS x

The crystallographic and electronic structures of compounds related to parkerite (Bi 2Ni 3S 2) are investigated with respect to the recently reported occurrence (Bi 2Pd 3Se 2) and absence (Bi 2Pd 3S 2) of superconductivity. Similarities and differences of the crystal structures are discussed within the series of solid solutions Bi 2Pd 3S 2− x Se x from powder and single crystal diffraction data. From crystal structure refinements, the question of different structures and settings of parkerite is discussed. Similar and different 2D and 3D partial Pd– Ch ( Ch=S, Se) structures are related to half antiperovskite ordering schemes. To investigate the relation of low dimensional structures and the occurrence of superconductivity, electronic structures are analyzed by scalar-relativistic DFT calculations, including site projected DOS, ECOV and Fermi surfaces.

Geometries of Third-Row Transition-Metal Complexes from Density-Functional Theory.

A set of 41 metal-ligand bond distances in 25 third-row transition-metal complexes, for which precise structural data are known in the gas phase, is used to assess optimized and zero-point averaged geometries obtained from DFT computations with various exchange-correlation functionals and basis sets. For a given functional (except LSDA) Stuttgart-type quasi-relativistic effective core potentials and an all-electron scalar relativistic approach (ZORA) tend to produce very similar geometries. In contrast to the lighter congeners, LSDA affords reasonably accurate geometries of 5d-metal complexes, as it is among the functionals with the lowest mean and standard deviations from experiment. For this set the ranking of some other popular density functionals, ordered according to decreasing standard deviation, is BLYP > VSXC > BP86 ≈ BPW91 ≈ TPSS ≈ B3LYP ≈ PBE > TPSSh > B3PW91 ≈ B3P86 ≈ PBE hybrid. In this case hybrid functionals are superior to their nonhybrid variants. In addition, we have reinvestigated the previous test sets for 3d- (Bühl M.; Kabrede, H. J. Chem. Theory Comput. 2006, 2, 1282-1290) and 4d- (Waller, M. P.; Bühl, M. J. Comput. Chem. 2007, 28, 1531-1537) transition-metal complexes using all-electron scalar relativistic DFT calculations in addition to the published nonrelativistic and ECP results. For this combined test set comprising first-, second-, and third-row metal complexes, B3P86 and PBE hybrid are indicated to perform best. A remarkably consistent standard deviation of around 2 pm in metal-ligand bond distances is achieved over the entire set of d-block elements.

The Isomers of Gadolinium Scandium Nitride Clusterfullerenes GdxSc3−xN@C80 (x=1, 2) and Their Influence on Cluster Structure

The isomers of gadolinium scandium mixed-metal nitride clusterfullerenes GdxSc3-xN@C(80) [x=2 (1, 4); x=1 (2, 5)] have been synthesized by the "reactive gas atmosphere" method and isolated facilely by recycling HPLC. The yield of GdxSc3-xN@C80 (I, II) (x=1, 2) relative to the homogenous clusterfullerenes Sc3N@C80 [I (3), II (6)] was determined. According to the UV/Vis/NIR spectroscopic data, 1, 2, 4, and 5 are all stable fullerenes with large optical gaps. Fullerene 1 has greater similarity to Gd3N@C80 (I) and 2 seems to resemble Sc3N@C80 (I). The quite similar overall absorption features of 4 and 5 suggest pronounced similarity in electronic structure. Vibrational spectroscopic studies led to the assignment of the cage symmetries of GdxSc3-xN@C80 (I, II), that is, Ih for 1, 2 and D5h for 4, 5. The cluster-cage interactions in GdxSc3-xN@C80 (I, II) were analyzed by means of the low-energy Raman lines. The splitting of the metal-nitrogen stretching vibrational mode in GdxSc3-xN@C80 (I, II) was studied in detail. Scalar-relativistic DFT calculations were performed to reveal the geometry parameters and the magnetic state of the GdxSc3-xN@C80 (I, II) molecules.

The Prediction of the Nuclear Quadrupole Splitting of 119Sn Mössbauer Spectroscopy Data by Scalar Relativistic DFT Calculations

The electric field gradient components for the tin nucleus of 34 tin compounds of experimentally known structures and (119)Sn Mössbauer spectroscopy parameters were computed at the scalar relativistic density functional theory level of approximation. The theoretical values of the electric field gradient components were used to determine a quantity, V, which is proportional to the nuclear quadrupole splitting parameter (DeltaE). In a subsequent linear regression analysis the effective nuclear quadrupole moment, Q, was evaluated. The value of (11.9+/-0.1) fm(2) is a significant improvement over the non-relativistic result of (15.2+/-4.4) fm(2) and is in agreement with the experimental value of (10.9+/-0.8) fm(2). The average mean square error DeltaE(calcd)-DeltaE(exptl)=+/-0.3 mm s(-1) is a factor of two smaller than in the non-relativistic case. Thus, the approach has a quality which provides accurate support for the structure interpretation by (119)Sn spectroscopy. It was noted that geometry optimization at the relativistic level does not significantly increase the quality of the results compared with non-relativistic optimized structures. The accuracy in the approach called on us to consider the singlet-triplet state nature of the electronic structure of one of the investigated compounds.

Structure and Bonding of the Hexameric Platinum(II) Dichloride, Pt6Cl12 (β‐PtCl2)

AbstractThe crystal structure of Pt6Cl12 (β‐PtCl2) was redetermined ($R \bar 3 m$ ah = 13.126Å, ch = 8.666Å, Z = 3; arh = 8.110Å, α = 108.04°; 367 hkl, R = 0.032). As has been shown earlier, the structure is in principle a hierarchical variant of the cubic structure type of tungsten (bcc), which atoms are replaced by the hexameric Pt6Cl12 molecules. Due to the 60° rotation of the cuboctahedral clusters about one of the trigonal axes, the symmetry is reduced from $Im \bar 3 m$ to $R \bar 3 m$ ($I \bar 3 m$). The molecule Pt6Cl12 shows the (trigonally elongated) structure of the classic M6X12 cluster compounds with (distorted) square‐planar PtCl4 fragments, however without metal‐metal bonds. The Pt atoms are shifted outside the Cl12 cuboctahedron by Δ = +0.046Å ($\bar {\rm d}$(Pt—Cl) = 2.315Å; $\bar {\rm d}$(Pt—Pt) = 3.339Å). The scalar relativistic DFT calculations results in the full $m \bar 3 m$ symmetry for the optimized structure of the isolated molecule with d(Pt—Cl) = 2.381Å, d(Pt—Pt) = 3.468Å and Δ = +0.072Å. The electron distribution of the Pt‐Pt antibonding HOMO exhibits an outwards‐directed asymmetry perpendicular to the PtCl4 fragments, that plays the decisive role for the cluster packing in the crystal. A comparative study of the Electron Localization Function with the hypothetical trans‐(Nb2Zr4)Cl12 molecule shows the distinct differences between Pt6Cl12 and clusters with metal‐metal bonding. Due to the characteristic electronic structure, the crystal structure of Pt6Cl12 in space group $R \bar 3 m$ is an optimal one, which results from comparison with rhombohedral Zr6I12 and a cubic bcc arrangement.