The neutral molecule NPrO and its anion NPrO– are characterized to be linear pentavalent praseodymium nitride-oxides that possess PrN triple bonds and PrO double bonds.

The chemistry of lanthanides (Ln = La-Lu) is dominated by the low-valent + 3or+ 2oxidation state because of the chemical inertness of the valence 4f electrons.T he highest knownoxidation state of the whole lanthanide series is + 4f or Ce,Pr, Nd, Tb,and Dy.W ereport the formation of the lanthanide oxide species PrO 4 and PrO 2 + complexes in the gas phase and in as olid noble-gas matrix. Combined infrared spectroscopic and advanced quantum chemistry studies show that these species have the unprecedented Pr V oxidation state, thus demonstrating that the pentavalent state is viable for lanthanide elements in as uitable coordination environment.Oxidation state (OS) has become ac entral concept of chemistry and astaple of chemistry textbooks.[1] Thequestion of just how high an OS of an element can be reached has long piqued chemists interest.[2] Thed iscovery of novel species with high OS helps to expand chemical understanding of the behavior of elements and their compounds.U ntil fairly recently,t he highest observed OS had been + 8, which occurs only in afew compounds including RuO 4 ,OsO 4 ,IrO 4 , and XeO 4 . [2][3][4][5] Recently,t he IrO 4 + cation was successfully formed in the gas phase,a nd was identified to contain the highest reported Ir IX oxidation state. [6,7] Forthe light elements in each row of the main group,t ransition metals,a nd actinides,the highest OS often equals the number of available valence electrons (e.g. + 3to+ 6f or Al-S,Sc-Cr,and Ac-U).However,i nl anthanides (Ln) the 4f orbitals are usually extremely contracted in radial distribution and considerably lower in energy because they penetrate the [Xe] core,t hus hardly participating in bonding.The chemistry of lanthanides is thus generally dominated by the low-valent + 3o r+ 2 oxidation state despite the fact that most lanthanides have available valence 4f electrons. [8][9][10] Besides the omnipresent oxidation state + 3, the higher oxidation state Ln IV is rather common for Ce,and is encountered in Pr, Nd, Tb,and Dy as well, [10] as these lanthanides have the lowest fourth ionization energies and also the lowest + 4/ + 3r eduction potentials. [11] Thec hemistry of pentavalent lanthanides has not been explored to date.[10] Aprevious study presumed the presence of pentavalent praseodymium in PrO 3 À without bonding analysis.[12] However,recent density functional theory (DFT) and ab initio multiconfigurational wavefunction theory (WFT) calculations show that the Pr center in the PrO 3 À anion is in oxidation state + 4r ather than the anticipated + 5.[13] Herein, we report ac ombined experimental and theoretical study on the lanthanide oxide species PrO 4 in solid noble-gas matrix as well as the PrO 2 + ion in the gas phase and in solid noble-gas matrix. Combined gas-phase infrared photodissociation spectroscopy,m atrix-isolation infrared absorption spectroscopy,a nd high-level quantum chemistry studies reveal that these species have the Pr V oxidation state. Thepraseodymium oxide cation species were generated in the gas phase by usi...

For further fundamental understanding of the nature and extent of covalency in actinyl-ligand bonding, and the benefits that this may have in the design of new ligands for nuclear waste separation, there is burgeoning interest in the nature of actinyl complexes with polydentate or multiple-point-donor ligands, such as crown ethers. There are few cases of structurally authenticated molecular actinyl-crown bonds under ambient conditions. We report here the computational characterization of AnO-(15-crown-5) complexes, where An = U, Np, Pu, Am, and Cm, and 15-crown-5 is the cyclic polyether ligand with five ether oxygen atoms. In the gas-phase complex, the actinyl group is located inside of the crown ether, tilted slightly out of the plane of the five equatorial oxygen atoms that coordinate the actinide metal center. The actinyl-cyclic ether complexes are found to exhibit a conventional conformation, with typical An-O and An-O distances and angles. A striking result is the enhanced stability of the insertion complex for UOversus NpO, PuO, AmO and CmO, which is evaluated in the context of An-O binding strengths (esp. bonding covalency), and may have ramifications for the utility of actinyl-crown complexes in separation applications.

The suitable band structure is vital for perovskite solar cells, which greatly affect the high photoelectric conversion efficiency. Cation substitution is an effective approach to tune the electric structure, carrier concentration, and optical absorption of hybrid lead iodine perovskites. In this work, the electronic structures and optical properties of cation (Bi, Sn, and TI) doped tetragonal formamidinium lead iodine CH(NH2)2PbI3 (FAPbI3) are studied by first-principles calculations. For comparison, the cation-doped tetragonal methylammonium lead iodine CH3NH3PbI3 (MAPbI3) are also considered. The calculated formation energies reveal that the Sn atom is easier to dope in the tetragonal MAPbI3/FAPbI3 structure due to the small formation energy of about 0.3 eV. Besides, the band gap of Sn-doped MAPbI3/FAPbI3 is 1.30/1.40 eV, which is considerably smaller than the un-doped tetragonal MAPbI3/FAPbI3. More importantly, compare with the un-doped tetragonal MAPbI3/FAPbI3, the Sn-doped MAPbI3 and FAPbI3 have the larger optical absorption coefficient and theoretical maximum efficiency, especially for Sn-doped FAPbI3. The lower formation energy, suitable band gap and outstanding optical absorption of the Sn-doped FAPbI3 make it promising candidates for high-efficient perovskite cells.

The classic Fokin mechanism of the CuAAC reaction of terminal alkynes using a variety of Cu(I) catalysts is wellknown to include alkyne deprotonation involving a bimetallic σ,π-alkynyl intermediate. In this study, we have designed a CNTsupported atomically precise nanocluster Au 4 Cu 4 (noted Au 4 Cu 4 /CNT) that heterogeneously catalyzes the CuAAC reaction of terminal alkynes without alkyne deprotonation to a σ,π-alkynyl intermediate. Therefore, three nanocluster−π-alkyne intermediates [Au 4 Cu 4 (π-CHC-p-C 6 H 4 R)], R = H, Cl, and CH 3 , have been captured and characterized by MALDI-MS. This Au 4 Cu 4 /CNT system efficiently catalyzed the CuAAC reaction of terminal alkynes, and internal alkynes also undergo this reaction. DFT results further confirmed that HCCPh was activated by π-complexation with Au 4 Cu 4 , unlike the classic dehydrogenation mechanism involving the bimetallic σ,π-alkynyl intermediate. On the other hand, a Cu 11 /CNT catalyst was shown to catalyze the reaction of terminal alkynes following the classic deprotonation mechanism, and both Au 11 /CNT and Cu 11 /CNT catalysts were inactive for the AAC reaction of internal alkynes under the same conditions, which shows the specificity of Au 4 Cu 4 involving synergy between Cu and Au in this precise nanocluster. This will offer important guidance for subsequent catalyst design.

In-cavity complexes and their bonding features between thio-crown (TC) ethers and f-elements are unexplored so far. In this paper, actinyl(VI) (An = U, Np, Pu, Am, and Cm) complexes of TC ethers have been characterized using relativistic density functional theory. The TC ether ligands include tetrathio-12-crown-4 (12TC4), pentathio-15-crown-5 (15TC5), and hexathio-18-crown-6 (18TC6). On the basis of the calculations, it is found that the "double-decker" sandwich structure of AnO(12TC4) and "side-on" structure AnO(12TC4) are changed to "insertion" structures for AnO(15TC5) and AnO(18TC6) due to increased size of the TC ether ligands. The actinyl monocyclic TC ether complexes are found to exhibit conventional conformations, with typical An-O and An-S distances and angles. Chemical bonding analyses by Weinhold's natural population analysis (NPA), natural localized molecular orbital (NLMO), and energy decomposed analysis (EDA), show that a typical ionic An-S bond with the extent of covalent interaction between the An and S atoms primarily attributable to the degree of radial distribution of the S 3p atomic orbitals. The similarity and difference of the oxo-crown and TC ethers as ligands for actinide coordination chemistry are discussed. As soft S-donor ligands, TC ethers may be candidate ligands for actinide recognition and extraction.

Organosodium chemistry is underdeveloped compared with organolithium chemistry, and all the reported organosodium complexes exhibit similar, if not identical, reactivity patterns to their lithium counterparts. Herein, we report a rare organosodium monomeric complex, namely, [Na(CH 2 SiMe 3 )(Me 6 Tren)] (1-Na) (Me 6 Tren: tris[2-(dimethylamino)ethyl]amine) stabilized by a tetra-dentate neutral amine ligand Me 6 Tren. Employing organo-carbonyl substrates (ketones, aldehydes, amides, ester), we demonstrated that 1-Na features distinct reactivity patterns compared with its lithium counterpart, [Li(CH 2 SiMe 3 )(Me 6 Tren)] (1-Li). Based on this knowledge, we further developed a ligand-catalysis strategy to conduct ketone/aldehyde methylenations, using [NaCH 2 SiMe 3 ] ∞ as the CH 2 feedstock, replacing the widely used but hazardous/expensive C�O methylenation methods, such as Wittig, Tebbe, Julia/Julia-Kocienśki, Peterson, and so on.

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