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1. Structure and vibrational spectroscopy of complexes of Al+ and Al2+ with ethane

   https://doi.org/10.1063/5.0266163  

   Ashraf, Muhammad Affawn; Metz, Ricardo B (April 2025, The Journal of Chemical Physics)

   The binding motifs of clusters of Al+ and Al2+ with ethane, Alx+(C2H6)n (x = 1, 2; n = 1–3), are determined using vibrational photodissociation spectroscopy in the C–H stretching region (2550–3100 cm−1) in conjunction with spectra calculated using density functional theory. The relative energies of candidate structures are determined with the B3LYP-D3 and ωB97X-D density functionals and the 6–311++G(d,p) basis set. Local mode Hamiltonian calculations are better able to reproduce the spectra than scaled harmonic calculations, due to contributions from bending overtones and combination bands. Vibrational photodissociation spectra show a red shift in the stretching frequencies of C–H bonds that are proximate to the cation. This red shift decreases as the number of ethanes increases. For Al+(C2H6)n (n = 1–3), side-on (T-shaped) binding of the metal is preferred to end-on binding, and subsequent ligands bind on the same side of the cation. Similarly, for Al2+(C2H6)n (n = 1–3), T-shaped configurations in which the C–C and Al–Al bonds are approximately perpendicular and the ethane binds side-on to the Al2+ are preferred. In Al2+(C2H6)n (n = 1–3) complexes, intense bands are observed, which are due to overtones and combinations of symmetric deformations in Fermi resonance with the red-shifted C–H stretches. 

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2. Differentiating Ligand Tailoring and Cation Incorporation as Strategies for Tuning Heterobimetallic Cerium Complexes

   https://doi.org/10.1002/chem.202500474  

   Mikeska, Emily_R; Blakemore, James_D (May 2025, Chemistry – A European Journal)

   Abstract Tuning of redox‐active complexes featuring metals with high coordination numbers by incorporation of secondary redox‐inactive cations has received far less attention than it deserves. Here, appending moderate steric bulk to a tripodal ligand framework has been tested for its influence on secondary‐cation‐driven structural and electrochemical tuning of cerium, a lanthanide that tends to adopt high coordination numbers. Aquasi‐C₃‐symmetric cerium(III) complex denoted[Ce]has been prepared that features pendant benzyloxy groups, and this work demonstrates that this species offers a site capable of binding single Na⁺or Ca²⁺ions. Electrochemical and UV‐visible spectroscopic studies reveal equilibrium binding affinity of[Ce]for Na⁺in acetonitrile solvent, contrasting with tight binding of all cations in all other previously studied systems of this type. The modulated cation binding can be attributed to the bulky benzyloxy groups, which impact the thermodynamics of cation binding but do not impede the formation of cerium centers with coordination number 8 upon binding of either Na⁺or Ca²⁺. The Ce(IV/III) reduction potential was found to be tunable under the equilibrium binding conditions, highlighting the potentially significant role that controlled structural changes can play in modulating the solution properties of heterobimetallic complexes. 

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3. Lanthanide binding peptide surfactants at air–aqueous interfaces for interfacial separation of rare earth elements

   https://doi.org/10.1073/pnas.2411763121  

   Ortuno_Macias, Luis E; Jiménez-Ángeles, Felipe; Marmorstein, Jason G; Wang, Yiming; Crane, Stephen A; K_T, Surabh; Sun, Pan; Sapkota, Bikash; Hummingbird, Eshe; Jung, Woojin; et al (December 2024, Proceedings of the National Academy of Sciences)

   Rare earth elements (REEs) are critical materials to modern technologies. They are obtained by selective separation from mining feedstocks consisting of mixtures of their trivalent cation. We are developing an all-aqueous, bioinspired, interfacial separation using peptides as amphiphilic molecular extractants. Lanthanide binding tags (LBTs) are amphiphilic peptide sequences based on the EF-hand metal binding loops of calcium-binding proteins which complex selectively REEs. We study LBTs optimized for coordination to Tb³⁺using luminescence spectroscopy, surface tensiometry, X-ray reflectivity, and X-ray fluorescence near total reflection, and find that these LBTs capture Tb³⁺in bulk and adsorb the complex to the interface. Molecular dynamics show that the binding pocket remains intact upon adsorption. We find that, if the net negative charge on the peptide results in a negatively charged complex, excess cations are recruited to the interface by nonselective Coulombic interactions that compromise selective REE capture. If, however, the net negative charge on the peptide is −3, resulting in a neutral complex, a 1:1 surface ratio of cation to peptide is achieved. Surface adsorption of the neutral peptide complexes from an equimolar mixture of Tb³⁺and La³⁺demonstrates a switchable platform dictated by bulk and interfacial effects. The adsorption layer becomes enriched in the favored Tb³⁺when the bulk peptide is saturated, but selective to La³⁺for undersaturation due to a higher surface activity of the La³⁺complex. 

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4. Fluoride anion complexation and transport using a stibonium cation stabilized by an intramolecular PO → Sb pnictogen bond

   https://doi.org/10.1039/D1DT03370K  

   Gonzalez, Vanessa M.; Park, Gyeongjin; Yang, Mengxi; Gabbaï, François P. (December 2021, Dalton Transactions)

   We describe the synthesis of [ o -Ph 2 P(O)(C 6 H 4 )SbPh 3 ] + ([2] + ), an intramolecularly base-stabilized stibonium Lewis acid which was obtained by reaction of [ o -Ph 2 P(C 6 H 4 )SbPh 3 ] + with NOBF 4 . This cation reacts with fluoride anions to afford the corresponding fluorostiborane o -Ph 2 P(O)(C 6 H 4 )SbFPh 3 , the structure of which indicates a strengthening of the PO → Sb interaction. When deployed in fluoride-containing POPC unilamellar vesicles, [2] + behaves as a potent fluoride anion transporter whose activity greatly exceeds that of [Ph 4 Sb] + . 

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5. Bandgap and band edge positions in compositionally graded ZnCdO

   https://doi.org/doi.org/10.1063/1.5036710  

   I.J.T. Jensen, K.M. Johansen (January 2018, Journal of applied physics)

   Introducing Cd into ZnO allows for bandgap engineering, potentially with particularly interesting properties to observe in compositionally graded samples. In this work, compositionally graded Zn1–xCdxO samples with 0x<0.16 were made using metal organic vapour phase epitaxy. The chemical composition was studied using scanning transmission electron microscopy, while the band structure of the samples was investigated using a combination of cathodoluminescence spectroscopy and X-ray photoelectron spectroscopy (XPS). It is found that the reduction of the bandgap in our samples is caused by changes in the conduction band. The position of the Fermi level relative to the vacuum level, i.e., the workfunction, was also found to change upon addition of Cd, giving an apparent shift in the valence band when evaluated from the XPS valence spectra. 

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