Altering the spectroscopy, electronic structure, and bonding of organometallic curium(III) upon coordination of 4,4'-bipyridine.

Structural and electronic characterization of (Cp'Cm)(μ-4,4'-bpy) (Cp' = trimethylsilylcyclopentadienyl, 4,4'-bpy = 4,4'-bipyridine) is reported and provides a rare example of curium-carbon bonding. Cp'Cm displays unexpectedly low energy emission that is quenched upon coordination by 4,4'-bipyridine. Electronic structure calculations on Cp'Cm and (Cp'Cm)(μ-4,4'-bpy) rule out significant differences in the emissive state, rendering 4,4'-bipyridine as the primary quenching agent.

Synthesis and Crystallographic Characterization of a Reduced Bimetallic Yttrium -Metallocene Hydride Complex, [K(crypt)][(μ-Cp)Y(μ-H)] (Cp = MeSi[CH(SiMe)-3]), with a 3.4 Å Yttrium-Yttrium Distance.

The reduction of a bimetallic yttrium -metallocene hydride was examined to explore the possible formation of Y-Y bonds with 4d Y(II) ions. The precursor [CpY(μ-H)(THF)] (Cp = MeSi[CH(SiMe)-3]) was synthesized by hydrogenolysis of the allyl complex CpY(η-CH)(THF), which was prepared from (CH)MgCl and [CpY(μ-Cl)]. Treatment of [CpY(μ-H)(THF)] with excess KC in the presence of one equivalent of 2.

Cyclopentadienyl coordination induces unexpected ionic Am-N bonding in an americium bipyridyl complex.

Variations in bonding between trivalent lanthanides and actinides is critical for reprocessing spent nuclear fuel. The ability to tune bonding and the coordination environment in these trivalent systems is a key factor in identifying a solution for separating lanthanides and actinides. Coordination of 4,4'-bipyridine (4,4'-bpy) and trimethylsilylcyclopentadienide (Cp') to americium introduces unexpectedly ionic Am-N bonding character and unique spectroscopic properties.

Creation of an unexpected plane of enhanced covalency in cerium(III) and berkelium(III) terpyridyl complexes.

Controlling the properties of heavy element complexes, such as those containing berkelium, is challenging because relativistic effects, spin-orbit and ligand-field splitting, and complex metal-ligand bonding, all dictate the final electronic states of the molecules. While the first two of these are currently beyond experimental control, covalent M‒L interactions could theoretically be boosted through the employment of chelators with large polarizabilities that substantially shift the electron density in the molecules. This theory is tested by ligating Bk with 4'-(4-nitrophenyl)-2,2':6',2"-terpyridine (terpy*), a ligand with a large dipole.

Synthesis, characterization, and theoretical analysis of a plutonyl phosphine oxide complex.

The interplay of bond strength and covalency are examined in AnOCl(OPcy) (An = Pu, U) complexes. The synthesis of -PuOCl(OPcy), 1-Pu, has been carried out and confirmed by single crystal X-ray diffraction along with UV-vis-NIR, and P NMR spectroscopies. Theoretical analysis finds that despite a higher calculated covalency for the Pu-Cl interaction, the Pu-OPcy interaction is stronger due to the accumulation of electron density in the interatomic region.

Influence of Outer-Sphere Anions on the Photoluminescence from Samarium(II) Crown Complexes.

Three samarium(II) crown ether complexes, [Sm(15-crown-5)]I (), [Sm(15-crown-5)]I·CHCN (), and [Sm(benzo-15-crown-5)]I (), have been prepared via the reaction of SmI with the corresponding crown ether in either THF or acetonitrile in good to moderate yields. The compounds have been characterized by single crystal X-ray diffraction and a variety of spectroscopic techniques. In all cases, the Sm(II) centers are sandwiched between two crown ether molecules and are bound by the five etheric oxygen atoms from each crown ether to yield 10-coordinate environments.

Understanding the Stabilization and Tunability of Divalent Europium 2.2.2B Cryptates.

Lanthanides such as europium with more accessible divalent states are useful for studying redox stability afforded by macrocyclic organic ligands. Substituted cryptands, such as 2.2.

Origin of Bond Elongation in a Uranium(IV) -Bis(imido) Complex.

The activation of U-N multiple bonds in an imido analogue of the uranyl ion is accomplished by using a system that is very electron-rich with sterically encumbering ligands. Treating the uranium(VI) -bis(imido) UI(NDIPP)(THF) (DIPP = 2,6-diisopropylphenyl and THF = tetrahydrofuran) with -butyl(dimethylsilyl)amide (NTSA) results in a reduction and rearrangement to form the uranium(IV) -bis(imido) [U(NDIPP)(NTSA)]K (). Compound features long U-N bonds, pointing toward substantial activation of the N═U═N unit, as determined by X-ray crystallography and H NMR, IR, and electronic absorption spectroscopies.

Exploring the Oxidation States of Neptunium with Schiff Base Coordination Complexes.

A pair of neptunium Schiff base coordination complexes, and { = ,'-bis[(4,4'-diethylamino)salicylidene]-1,2-phenylenediamine}, have been synthesized and analyzed by several characterization methods including single-crystal X-ray diffraction, electronic absorption, H NMR, cyclic voltammetry, and theoretical interpretation. Structural analysis reveals that and are isomorphous with the previously reported and (M = Pu, Ce, U, Th) complexes, respectively, allowing for a direct comparison across the series. The reduction of or direct synthesis from a (NpO) source shows evidence of a pentavalent neptunyl species as determined by UV/vis/NIR and H NMR spectroscopy.

The role of the excited state dynamic of the antenna ligand in the lanthanide sensitization mechanism.

A fragmentation scheme combined with a series of theoretical approximations like TD-DFT, and multiconfigurational CASSCF/NEVPT2 methods, has been used to describe the photophysical phenomena associated with the antenna effect and lanthanide ion emission. The theoretical protocol was used in (Cp2Ph)3Tb and (Cp2Ph)TbCl2(THF)3, where Cp2Ph = diphenylcyclopentadienyl and THF = tetrahydrofuran, organometallic complexes recently reported by Roitershtein et al. (Inorg.

Classical and Quantum Mechanical Calculations of the Stacking Interaction of Nd Complexes with Regular and Mismatched DNA Sequences.

The design of organometallic complexes used as selective intercalators to bind and react at DNA mismatch sites has concentrated efforts in the last few years. In this context, lanthanides have received attention to be employed as active optical centers due to their spectroscopic properties. Despite the fact that there are several experimental data about synthesis and DNA binding of these compounds, theoretical analyses describing their interaction with DNA are scarce.

Rare-Earth Metal(II) Aryloxides: Structure, Synthesis, and EPR Spectroscopy of [K(2.2.2-cryptand)][Sc(OC H tBu -2,6-Me-4) ].

The suitability of aryloxide ligands for stabilizing +2 oxidation states of Sc and Y has been examined and EPR evidence indicating the first O-donor complexes of Sc and Y has been obtained, as well as an X-ray crystal structure of a Sc aryloxide complex. The trivalent rare-earth metal aryloxide precursors, Ln(OAr') , 1-Ln (Ln=Sc, Y, Gd, Dy, Ho, Er; OAr'=OC H tBu -2,6-Me-4), were synthesized from the corresponding rare-earth metal trichlorides and LiOAr'⋅OEt . Reduction of THF solutions of 1-Ln with potassium graphite in the presence of 2.

Theoretical Determination of Energy Transfer Processes and Influence of Symmetry in Lanthanide(III) Complexes: Methodological Considerations.

This work presents a theoretical protocol to analyze the symmetry effect on the allowed character of the transitions and to estimate the probability of energy transfer in lanthanide(III) complexes. For this purpose, a complete study was performed based on the multireference CASSCF/PT2 technique along with TDDFT, to build the energy level diagrams and determine the spectral overlap integrals, respectively. This approach was applied on a series of LnIII complexes, viz.

Three new types of transition metal carboranylamidinate complexes.

Three new types of transition metal carboranylamidinate complexes are reported. The tetranuclear Mn(ii) complex Mn4Cl6[(o-C2B10H10)C(NiPr)(NHiPr)]2(THF)4·THF (2) was prepared by treatment of anhydrous MnCl2 with Li[(o-C2B10H10)C(NiPr)(NHiPr)] ([double bond, length as m-dash]Li[HLiPr]) in THF, while the analogous reaction with FeCl2 afforded ionic [Li(DME)3][FeCl2{(o-C2B10H10)C(NiPr)(NHiPr)}] (3). The dinuclear Mo(ii) complex Mo2[(o-C2B10H10)C(NiPr)(NHiPr)]2(OAc)2·2THF (4), obtained from Mo2(OAc)4 and 2 equiv.

Ab initio calculations of heavy-actinide hexahalide compounds: do these heavy actinides behave like their isoelectronic lanthanide analogues?

Research on heavy actinides has experienced an increased interest in the last few years due to new synthetic techniques and recent technological advances that have allowed for obtaining important information even from very small samples. This area presents challenges not only from the experimental point of view but also from the theoretical perspective. This work deals with a multiconfigurational CASSCF and NEVPT2 benchmark study based on a two-step methodology that considers first correlation effects and then the spin-orbit coupling applied to berkelium (Bk), californium (Cf), einsteinium (Es) and fermium (Fm) hexahalides.

Theoretical Method for an Accurate Elucidation of Energy Transfer Pathways in Europium(III) Complexes with Dipyridophenazine (dppz) Ligand: One More Step in the Study of the Molecular Antenna Effect.

A theoretical protocol to study the sensitization and emission mechanism in lanthanide compounds on the basis of multireference CASSCF/PT2 calculations is proposed and applied to [Eu(NO)(dppz-CN)] and [Eu(NO)(dppz-NO)] compounds synthesized and characterized herein. The method consists of a fragmentation scheme where both the ligand and the lanthanide fragments were calculated separately but at the same level of theory, using ab initio wave-function-based methods which are adequate for the treatment of quasi-degenerate states. This is based on the fact that the absorption is ligand-localized and the emission is europium-centered.