Lanthanide-Dependent Photochemical and Photophysical Properties of Lanthanide-Anthracene Complexes: Experimental and Theoretical Approaches.

The structural, photophysical, and photochemical properties of Ln(depma)(hmpa)(NO) (Ln = La, Ce, Nd, Sm, Eu, Tb, Ho, Er, and Yb) complexes were investigated with a multidisciplinary approach involving synthesis, photocycloaddition-based crystal engineering, spectroscopic analytical techniques and quantum chemical ab initio calculations. Depending on the Ln ion the isostructural complexes exhibit quite different behavior upon excitation at 350-400 nm. Some complexes (Ln = La, Ce, Sm, Tb, Yb) emit a broad and strong band near 533 nm arising from paired anthracene moieties, whereas others (Ln = Nd, Eu, Ho, Er) do not.

Systematic Raman spectroscopic study of the complexation of uranyl with fluoride.

A simple aqueous complexing system of UO with F is selected to systematically illustrate the application of Raman spectroscopy in exploring uranyl(VI) chemistry. Five successive complexes, UOF, UOF(aq), UOF, UOF, and UOF, are identified, as well as the formation constants except for the 1 : 5 species UOF, which was experimentally observed here for the first time. The standard relative molar Raman scattering intensity for each species is obtained by deconvolution of the spectra collected during titrations.

Linear Scaling Incremental Scheme for Correlation Energies with Embedding Generated Virtuals.

A novel incremental scheme is presented including an incremental expansion of the virtual space for the calculation of electron correlation energies, which is compatible with any size-extensive correlation method and scales asymptotically linear for large molecules. The performance is studied for organic molecules, water clusters, and a La(III)-water complex, where the compatibility with pseudopotentials is also examined. The computational requirements are already reduced tremendously for medium-sized water clusters and hydrocarbons with respect to the canonical CCSD as well as the ordinary incremental scheme references.

Periodic trends and complexation chemistry of tetravalent actinide ions with a potential actinide decorporation agent 5-LIO(Me-3,2-HOPO): A relativistic density functional theory exploration.

A relativistic density functional theory (DFT) study is reported which aims to understand the complexation chemistry of An ions (An = Th, U, Np, and Pu) with a potential decorporation agent, 5-LIO(Me-3,2-HOPO). The calculations show that the periodic change of the metal binding free energy has an excellent correlation with the ionic radii and such change of ionic radii also leads to the structural modulation of actinide-ligand complexes. The calculated structural and binding parameters agree well with the available experimental data.

Density Functional Studies of Coenzyme NADPH and Its Oxidized Form NADP : Structures, UV-Vis Spectra, and the Oxidation Mechanism of NADPH.

Density functional theory has been used to study the biologically important coenzyme NADPH and its oxidized form NADP . It was found that free NADPH prefers a compact structure in gas phase and exists in more extended geometries in aqueous solution. Ultraviolet-visible absorption spectra in aqueous solution were calculated for NADPH with an explicit treatment of 100 surrounding water molecules in combination with the COSMO solvation model for bulk hydration effects.

Enhancing Actinide(III) over Lanthanide(III) Selectivity through Hard-by-Soft Donor Substitution: Exploitation and Implication of Near-Degeneracy-Driven Covalency.

Soft donor ligands often provide higher selectivity for actinides(III) over chemically similar lanthanides(III), e.g., in the Am-Eu pair.

An Efficient Hartree-Fock Implementation Based on the Contraction of Integrals in the Primitive Basis.

A new approach to implement the restricted closed-shell Hartree-Fock equation is proposed. In the ansatz presented, the explicit transformation of integrals from the primitive to the atomic-orbital basis is omitted. Instead, the density matrix is transformed to the primitive basis, in which it is contracted with the untransformed integrals.

Visible-Light Photocatalysis of C(sp )-H Fluorination by the Uranyl Ion: Mechanistic Insights.

The uranyl dication shows photocatalytic activity towards C(sp )-H bonds of aliphatic compounds, but not towards those of alkylbenzenes or cyclic ketones. Theoretical insights into the corresponding mechanisms are still limited. Multi-configurational ab initio calculations including relativistic effects reveal the inherent electron-transfer mechanism for the uranyl catalyzed C-H fluorination under blue light.

The Origin of the Photoluminescence Enhancement of Gold-Doped Silver Nanoclusters: The Importance of Relativistic Effects and Heteronuclear Gold-Silver Bonds.

The weak photoluminescence of silver nanoclusters prevents their broad application as luminescent nanomaterials. Recent experiments, however, have shown that gold doping can significantly enhance the photoluminescence intensity of Ag nanoclusters but the molecular and physical origins of this effect remain unknown. Therefore, we have computationally explored the geometric and electronic structures of Ag and gold-doped Ag Au (x=1-5) nanoclusters in the S and S states.

The difficult search for organocerium(iv) compounds.

This Tutorial Review provides an overview of the historic and current development of the organometallic chemistry of cerium in its oxidation state 4+. Among the tetravalent lanthanide ions, only Ce forms stable coordination compounds (e.g.

The first water coordination sphere of lanthanide(iii) motexafins (Ln-Motex, Ln = La, Gd, Lu) and its effects on structures, reduction potentials and UV-vis absorption spectra. Theoretical studies.

Density functional calculations have been performed to study selected hydrated lanthanide(iii) motexafins (Ln-Motex, Ln = La, Gd, Lu) by using energy-consistent 4f-in-core lanthanide pseudopotentials to include the major relativistic effects due to the heavy metals. The maximum number (n) of water molecules bound strongly to [Ln-Motex] (Ln = La, Gd, Lu) was determined to be 6 by calculating the change of the Gibbs energies for the reactions [Ln-Motex(HO)] + HO → [Ln-Motex(HO)]. The number of water molecules coordinated directly to Ln was found to be 3 for La, and 2 for Gd and Lu.

Energy Resonance Crossing Controls the Photoluminescence of Europium Antenna Probes.

The energy transfer pathways in lanthanide antenna probes cannot be comprehensively rationalized by the currently available models, and their elucidation remains to be a challenging task. On the basis of quantum-chemical ab initio calculations of representative europium antenna complexes, an innovative energy resonance model is proposed, which is controlled by an overall nonet-quintet intersystem crossing on the basis of spin-orbit coupling among the sublevels of the involved states.

Quantum chemical study of the autoxidation of ascorbate.

Reactions involved in the autoxidation of ascorbate have been investigated with quantum chemical first-principles and ab initio methods. Reaction energies and Gibbs energies of the reactions were calculated at the density functional theory level applying the gradient-corrected BP86 and the hybrid B3LYP functionals together with def2-TZVP basis sets. Results of single-point CC2, CCSD, and CCSD(T) calculations were used for calibration of the density functional theory data and show excellent agreement with the B3LYP values.

Assigning the Cerium Oxidation State for CH2CeF2 and OCeF2 Based on Multireference Wave Function Analysis.

The geometric and electronic structure of the recently experimentally studied molecules ZCeF2 (Z = CH2, O) was investigated by density functional theory (DFT) and wave function-based ab initio methods. Special attention was paid to the Ce-Z metal-ligand bonding, especially to the nature of the interaction between the Ce 4f and the Z 2p orbitals and the possible multiconfigurational character arising from it, as well as to the assignment of an oxidation state of Ce reflecting the electronic structure. Complete active space self-consistent field (CASSCF) calculations were performed, followed by orbital rotations in the active orbital space.

Global optimization of clusters of rigid molecules using the artificial bee colony algorithm.

The global optimization of molecular clusters is an important topic encountered in many fields of chemistry. In our previous work (Phys. Chem.

Actinoid(III) Hydration-First Principle Gibbs Energies of Hydration Using High Level Correlation Methods.

The Gibbs energies of hydration of actinoid(III) ions are evaluated for density functional optimized geometries of [An(H2O)h](3+) complexes (h = 8, 9) at the coupled cluster singles, doubles, and perturbative triples level by means of the incremental scheme. Scalar-relativistic 5f-in-core pseudopotentials for actinoids and basis sets of polarized triple-ζ quality were applied. The calculated Gibbs energies for the octa- and nona-aquo complexes agree within 1% with the experimental values which are available only for uranium and plutonium.

Third-Order Incremental Dual-Basis Set Zero-Buffer Approach for Large High-Spin Open-Shell Systems.

The third-order incremental dual-basis set zero-buffer approach (inc3-db-B0) is an efficient, accurate, and black-box quantum chemical method for obtaining correlation energies of large systems, and it has been successfully applied to many real chemical problems. In this work, we extend this approach to high-spin open-shell systems. In the open-shell approach, we will first decompose the occupied orbitals of a system into several domains by a K-means clustering algorithm.

Regulatory Mechanism of the Enantioselective Intramolecular Enone [2+2] Photocycloaddition Reaction Mediated by a Chiral Lewis Acid Catalyst Containing Heavy Atoms.

The asymmetric catalysis of the intramolecular enone [2+2] photocycloaddition has been subject of extensive experimental studies, however theoretical insight to its regulatory mechanism is still sparse. Accurate quantum chemical calculations at the CASPT2//CASSCF level of theory associated with energy-consistent relativistic pseudopotentials provide a basis for the first regulation theory that the enantioselective reaction is predominantly controlled by the presence of relativistic effects, that is, spin-orbit coupling resulting from heavy atoms in the chiral Lewis acid catalyst.

ABCluster: the artificial bee colony algorithm for cluster global optimization.

Global optimization of cluster geometries is of fundamental importance in chemistry and an interesting problem in applied mathematics. In this work, we introduce a relatively new swarm intelligence algorithm, i.e.

Accurate quantum chemical modelling of the separation of Eu(3+) from Am(3+)/Cm(3+) by liquid-liquid extraction with Cyanex272.

The experimentally observed extraction complexes of trivalent lanthanide Eu(3+) and actinide Am(3+)/Cm(3+) cations with Cyanex272 [bis(2,4,4-trimethylpentyl) phosphinic acid, denoted as HC272] and Cyanex301 [bis(2,4,4-trimethylpentyl) dithiophosphinic acid, denoted as HC301] have been studied by using relativistic energy-consistent 4f- and 5f-in-core pseudopotentials for trivalent f elements, combined with density functional theory and a continuum solvation model. It has been found that, as a result of hydrogen bonding, HC272 exists primarily as a self-associated species, whereas HC301 is preferably a monomer. The calculations show that in case of all three M(3+) (M = Eu, Am, Cm) ions for HC272 the extraction complexes M[H(C272)2]3 are formed prior to M(C272)3, whereas for HC301 the extraction complexes M(C301)3 have priority over M[H(C301)2]3.

A theoretical study of imine hydrocyanation catalyzed by halogen-bonding.

A detailed theoretical study of the mechanism and energetics of an organocatalysis based on C=N activation by halogen-bonding is presented for the hydrocyanation of N-benzylidenemethylamine. The calculations at the level of scalar-relativistic gradient-corrected density functional theory give an insight in this catalytic concept and provide information on the characteristics of four different monodentate catalyst candidates acting as halogen-bond donors during the reaction.

Approaching the complete basis set limit of CCSD(T) for large systems by the third-order incremental dual-basis set zero-buffer F12 method.

The third-order incremental dual-basis set zero-buffer approach was combined with CCSD(T)-F12x (x = a, b) theory to develop a new approach, i.e., the inc3-db-B0-CCSD(T)-F12 method, which can be applied as a black-box procedure to efficiently obtain the near complete basis set (CBS) limit of the CCSD(T) energies also for large systems.

Labile capping bonds in lanthanide(III) complexes: shorter and weaker.

For a wide range of trivalent lanthanide ion coordination complexes of tricapped trigonal prism or monocapped square antiprism configurations, the bonds between the central lanthanide ions and the capping ligands are found to violate Badger's rule: they can get weaker as they get shorter. We demonstrate that this observation originates from the screening and repulsion effect of the prism ligands. Both effects enhance as the electric field of the central ion or the softness of the prism ligands increases.

Dispersion interaction stabilizes sterically hindered double fullerenes.

By state-of-the-art quantum chemical methods, we show that for bulky functional groups like cyclohexane, [20]fullerene, dodecahedrane, and C60, the attractive dispersion interaction can have a greater impact on stereochemistry than the repulsive steric effect, making the compact isomer the more stable one. In particular, for the double C60 adduct of pentacene 1, the syn isomer should be the main product instead of the anti one inferred in the original synthesis experiment (Y. Murata et al.

Understanding lanthanoid(III) hydration structure and kinetics by insights from energies and wave functions.

The hydration of all trivalent lanthanoid (Ln) ions is studied theoretically from two aspects: energy and wave function. With the help of the incremental scheme, for the first time the lanthanoid(III) aqua complexes are computed at the CCSD(T) level using large basis sets. These computations prove that SCS-MP2 is nearly as accurate as CCSD, thus enabling us to give the most accurate first principle hydration Gibbs free energies and reliable preferred coordination numbers (CNs) of lanthanoid(III) aqua complexes: 9, 8, and both, for light, heavy, and intermediate lanthanoids, respectively.