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1. Collision‐induced dissociation of [UO 2 (NO 3 ) 3 ] − and [UO 2 (NO 3 ) 2 (O 2 )] − and reactions of product ions with H 2 O and O 2

   https://doi.org/10.1002/jms.4705  

   Bubas, Amanda R. ; Perez, Evan ; Metzler, Luke J. ; Rissler, Scott D. ; Van Stipdonk, Michael J. ( February 2021 , Journal of Mass Spectrometry)

   Electrospray ionization (ESI) can produce a wide range of gas‐phase uranyl (UO₂²⁺) complexes for tandem mass spectrometry studies of intrinsic structure and reactivity. We describe here the formation and collision‐induced dissociation (CID) of [UO₂(NO₃)₃]⁻and [UO₂(NO₃)₂(O₂)]⁻. Multiple‐stage CID experiments reveal that the complexes dissociate in reactions that involve elimination of O₂, NO₂, or NO₃, and subsequent reactions of interesting uranyl‐oxo product ions with (neutral) H₂O and/or O₂were investigated. Density functional theory (DFT) calculations reproduce experimental results and show that dissociation of nitrate ligands, with ejection of neutral NO₂, is favored for both [UO₂(NO₃)₃]⁻and [UO₂(NO₃)₂(O₂)]⁻. DFT calculations also suggest that H₂O adducts to products such as [UO₂(O)(NO₃)]⁻spontaneously rearrange to create dihydroxides and that addition of O₂is favored over addition of H₂O to formally U(V) species.

    

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2. Solvothermal Synthesis of [Cr 7 S 8 (en) 8 Cl 2 ]Cl 3  ⋅ 2H 2 O with Magnetically Frustrated [Cr 7 S 8 ] 5+ Double‐Cubes**

   https://doi.org/10.1002/chem.202103761  

   Gamage, Eranga H. ; Clark, Judith K. ; Yazback, Maher ; Cheng, Hai‐Ping ; Shatruk, Michael ; Kovnir, Kirill ( December 2021 , Chemistry – A European Journal)

   A novel transition metal chalcohalide [Cr₇S₈(en)₈Cl₂]Cl₃ ⋅ 2H₂O, with [Cr₇S₈]⁵⁺dicubane cationic clusters, has been synthesized by a low temperature solvothermal method, using dimethyl sulfoxide (DMSO) and ethylenediamine (en) solvents. Ethylenediamine ligand exhibits bi‐ and monodentate coordination modes; in the latter case ethylenediamine coordinates to Cr atoms of adjacent clusters, giving rise to a 2D polymeric structure. Although magnetic susceptibility shows no magnetic ordering down to 1.8 K, a highly negative Weiss constant,θ=−224(2) K, obtained from Curie‐Weiss fit of inverse susceptibility, suggests strong antiferromagnetic (AFM) interactions betweenS=3/2 Cr(III) centers. Due to the complexity of the system with (2S+1)⁷=16384 microstates from seven Cr³⁺centers, a simplified model with only two exchange constants was used for simulations. Density‐functional theory (DFT) calculations yielded the two exchange constants to beJ₁=−21.4 cm⁻¹andJ₂=−30.2 cm⁻¹, confirming competing AFM coupling between the shared Cr³⁺center and the peripheral Cr³⁺ions of the dicubane cluster. The best simulation of the experimental data was obtained withJ₁=−20.0 cm⁻¹andJ₂=−21.0 cm⁻¹, in agreement with the slightly stronger AFM exchange within the triangles of the peripheral Cr³⁺ions as compared to the AFM exchange between the central and peripheral Cr³⁺ions. This compound is proposed as a synthon towards magnetically frustrated systems assembled by linking dicubane transition metal‐chalcogenide clusters into polymeric networks.

    

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3. Al(OR F ) 3 (R F = C(CF 3 ) 3 ) activated silica: a well-defined weakly coordinating surface anion

   https://doi.org/10.1039/C9SC05904K  

   Culver, Damien B. ; Venkatesh, Amrit ; Huynh, Winn ; Rossini, Aaron J. ; Conley, Matthew P. ( February 2020 , Chemical Science)

   Weakly Coordinating Anions (WCAs) containing electron deficient delocalized anionic fragments that are reasonably inert allow for the isolation of strong electrophiles. Perfluorinated borates, perfluorinated aluminum alkoxides, and halogenated carborane anions are a few families of WCAs that are commonly used in synthesis. Application of similar design strategies to oxide surfaces is challenging. This paper describes the reaction of Al(OR F ) 3 *PhF (R F = C(CF 3 ) 3 ) with silica partially dehydroxylated at 700 °C (SiO 2-700 ) to form the bridging silanol Si–OH⋯Al(OR F ) 3 ( 1 ). DFT calculations using small clusters to model 1 show that the gas phase acidity (GPA) of the bridging silanol is 43.2 kcal mol −1 lower than the GPA of H 2 SO 4 , but higher than the strongest carborane acids, suggesting that deprotonated 1 would be a WCA. Reactions of 1 with NOct 3 show that 1 forms weaker ion-pairs than classical WCAs, but stronger ion-pairs than carborane or borate anions. Though 1 forms stronger ion-pairs than these state-of-the-art WCAs, 1 reacts with alkylsilanes to form silylium type surface species. To the best of our knowledge, this is the first example of a silylium supported on derivatized silica. 

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4. Optical properties of undoped, Eu 3+ doped and Li + co-doped Y 2 Hf 2 O 7 nanoparticles and polymer nanocomposite films

   https://doi.org/10.1039/c9qi01181a  

   Gupta, Santosh K. ; Zuniga, Jose P. ; Abdou, Maya ; Ghosh, P. S. ; Mao, Yuanbing ( January 2020 , Inorganic Chemistry Frontiers)

   Desirable phosphors for lighting, scintillation and composite films must have good light absorption properties, high concentration quenching, high quantum efficiency, a narrow color emission, and so forth. In this work, we first show that undoped yttrium hafnate Y 2 Hf 2 O 7 (YHO) nanoparticles (NPs) display dual blue and red bands after excitation using 330 nm light. Based on density functional theory (DFT) calculations, these two emission bands are correlated with the defect states arising in the band-gap region of YHO owing to the presence of neutral and charged oxygen defects. Once doped with Eu 3+ ions (YHOE), the YHO NPs show a bright red emission, a long excited state lifetime and stable color coordinates upon near-UV and X-ray excitation. Concentration quenching is active when Eu 3+ doping reaches 10 mol% with a critical distance of ∼4.43 Å. This phenomenon indicates a high Eu 3+ solubility within the YHO host and the absence of Eu 3+ clusters. More importantly, the optical performance of the YHOE NPs has been further improved by lithium co-doping. The origin of the emission, structural stability, and role of Li + -co-doping are explored both experimentally and theoretically. DFT calculation results demonstrate that Li + -co-doping increases the covalent character of the Eu 3+ –O 2− bonding in the EuO 8 polyhedra. Furthermore, the YHOE NPs have been dispersed into polyvinyl alcohol (PVA) to make transparent nanocomposite films, which show strong red emission under excitation at 270 and 393 nm. Overall, we demonstrate that the YHO NPs with Eu 3+ and (Eu 3+ /Li + ) doping have a high emission intensity and quantum efficiency under UV and X-ray excitation, which makes them suitable for use as phosphors, scintillators and transparent films for lighting, imaging and detection applications. 

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5. Origin of the 29 Si NMR chemical shift in R 3 Si–X and relationship to the formation of silylium (R 3 Si + ) ions

   https://doi.org/10.1039/D0DT02099K  

   Huynh, Winn ; Conley, Matthew P. ( November 2020 , Dalton Transactions)

   null (Ed.)

   The origin in deshielding of 29 Si NMR chemical shifts in R 3 Si–X, where X = H, OMe, Cl, OTf, [CH 6 B 11 X 6 ], toluene, and O X (O X = surface oxygen), as well as i Pr 3 Si + and Mes 3 Si + were studied using DFT methods. At the M06-L/6-31G(d,p) level of theory the geometry optimized structures agree well with those obtained experimentally. The trends in 29 Si NMR chemical shift also reproduce experimental trends; i Pr 3 Si–H has the most shielded 29 Si NMR chemical shift and free i Pr 3 Si + or isolable Mes 3 Si + have the most deshielded 29 Si NMR chemical shift. Natural localized molecular orbital (NLMO) analysis of the contributions to paramagnetic shielding ( σ p ) in these compounds shows that Si–R (R = alkyl, H) bonding orbitals are the major contributors to deshielding in this series. The Si–R bonding orbitals are coupled to the empty p-orbital in i Pr 3 Si + or Mes 3 Si + , or to the orbital in R 3 Si–X. This trend also applies to surface bound R 3 Si–O X . This model also explains chemical shift trends in recently isolated t Bu 2 SiH 2 + , t BuSiH 2 + , and SiH 3 + that show more shielded 29 Si NMR signals than R 3 Si + species. There is no correlation between isotropic 29 Si NMR chemical shift and charge at silicon. 

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