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1. Cu( i )–O 2 oxidation reactions in a fluorinated all-O-donor ligand environment

   https://doi.org/10.1039/C8DT05028G  

   Brazeau, Sarah E. ; Doerrer, Linda H. ( April 2019 , Dalton Transactions)

   Investigation of Cu–O 2 oxidation reactivity is important in biological and anthropogenic chemistry. Zeolites are one of the most promising Cu/O based oxidation catalysts for development of industrial-scale CH 4 to CH 3 OH conversion. Their oxidation mechanisms are not well understood, however, highlighting the importance of the investigation of molecular Cu( i )–O 2 reactivity with O-donor complexes. Herein, we give an overview of the synthesis, structural properties, and O 2 reactivity of three different series of O-donor fluorinated Cu( i ) alkoxides: K[Cu(OR) 2 ], [(Ph 3 P)Cu(μ-OR) 2 Cu(PPh 3 )], and K[(R 3 P)Cu(pin F )], in which OR = fluorinated monodentate alkoxide ligands and pin F = perfluoropinacolate. This breadth allowed for the exploration of the influence of the denticity of the ligand, coordination number, the presence of phosphine, and K⋯F/O interactions on their O 2 reactivity. K⋯F/O interactions were required to activate O 2 in the monodentate-ligand-only family, whereas these connections did not affect O 2 activation in the bidentate complexes, potentially due to the presence of phosphine. Both families formed trisanionic, trinuclear cores of the form {Cu 3 (μ 3 -O) 2 } 3− . Intramolecular and intermolecular substrate oxidation were also explored and found to be influenced by the fluorinated ligand. Namely, {Cu 3 (μ 3 -O) 2 } 3− from K[Cu(OR) 2 ] could perform both monooxygenase reactivity and oxidase catalysis, whereas those from K[(R 3 P)Cu(pin F )] could only perform oxidase catalysis. 

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2. Synthetic route to vanadium(III) dichalcogenidophosphinate complexes, V(S 2 PPh 2 ) 3 and V(Se 2 PPh 2 ) 3 : A spectroscopic and structural comparative study with analogous complexes of chromium(III), Cr(E 2 PPh 2 ) 3 (E=S, Se)

   https://doi.org/10.1002/zaac.202000396  

   Phipps, Christine A. ; Rosenberger, Joanna M. ; Miller, McKenzie M. ; Parkin, Sean R. ; Brown, Jessie L. ( April 2021 , Zeitschrift für anorganische und allgemeine Chemie)

   Addition of the potassium dichalcogenidodiphenylphosphinate salts, KE₂PPh₂(E=S, Se), to either the THF solvate of vanadium(III) chloride or unsolvated chromium(III) chloride results in rapid ligand substitution and the formation of a series of closely‐related trivalent, neutral mononuclear complexes, M(E₂PPh₂)₃(M=V, Cr; E=S, Se), isolated in modest to good yield. The metal dichalcogenidophosphinate complexes reported herein were characterized by IR, UV‐vis, and¹H NMR spectroscopies, and their solid‐state molecular structures were determined by single‐crystal X‐ray crystallography. Importantly, the comparative analysis includes the structural and spectroscopic studies of two rare V(III) dithio‐ and diseleno‐phosphinate VE₆cores, as well as, two previously known CrE₆analogues. In the solid‐state the title complexes exhibit trigonal distortion from octahedral with torsion angles ranging from 43(2) to 50.3(6)° and structural parameters consistent with ligation of progressively ‘softer’ chalcogen‐donors.

    

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3. Applying Unconventional Spectroscopies to the Single‐Molecule Magnets, Co(PPh 3 ) 2 X 2 (X=Cl, Br, I): Unveiling Magnetic Transitions and Spin‐Phonon Coupling

   https://doi.org/10.1002/chem.202100705  

   Bone, Alexandria N. ; Widener, Chelsea N. ; Moseley, Duncan H. ; Liu, Zhiming ; Lu, Zhengguang ; Cheng, Yongqiang ; Daemen, Luke L. ; Ozerov, Mykhaylo ; Telser, Joshua ; Thirunavukkuarasu, Komalavalli ; et al ( August 2021 , Chemistry – A European Journal)

   Large separation of magnetic levels and slow relaxation in metal complexes are desirable properties of single‐molecule magnets (SMMs). Spin‐phonon coupling (interactions of magnetic levels with phonons) is ubiquitous, leading to magnetic relaxation and loss of memory in SMMs and quantum coherence in qubits. Direct observation of magnetic transitions and spin‐phonon coupling in molecules is challenging. We have found that far‐IR magnetic spectra (FIRMS) of Co(PPh₃)₂X₂(Co‐X; X=Cl, Br, I) reveal rarely observed spin‐phonon coupling as avoided crossings between magnetic andu‐symmetry phonon transitions. Inelastic neutron scattering (INS) gives phonon spectra. Calculations using VASP and phonopy programs gave phonon symmetries and movies. Magnetic transitions among zero‐field split (ZFS) levels of theS=3/2 electronic ground state were probed by INS, high‐frequency and ‐field EPR (HFEPR), FIRMS, and frequency‐domain FT terahertz EPR (FD‐FT THz‐EPR), giving magnetic excitation spectra and determining ZFS parameters (D, E) andgvalues. Ligand‐field theory (LFT) was used to analyze earlier electronic absorption spectra and give calculated ZFS parameters matching those from the experiments. DFT calculations also gave spin densities inCo‐X, showing that the larger Co(II) spin density in a molecule, the larger its ZFS magnitude. The current work reveals dynamics of magnetic and phonon excitations in SMMs. Studies of such couplings in the future would help to understand how spin‐phonon coupling may lead to magnetic relaxation and develop guidance to control such coupling.

    

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4. Oxygen uptake in complexes related to [NiFeS]- and [NiFeSe]-hydrogenase active sites

   https://doi.org/10.1039/C8SC04436H  

   Yang, Xuemei ; Elrod, Lindy C. ; Reibenspies, Joseph H. ; Hall, Michael B. ; Darensbourg, Marcetta Y. ( January 2019 , Chemical Science)

   A biomimetic study for S/Se oxygenation in Ni(μ-EPh)(μ-SN 2 )Fe, (E = S or Se; SN 2 = Me-diazacycloheptane-CH 2 CH 2 S); Fe = (η 5 -C 5 H 5 )Fe II (CO) complexes related to the oxygen-damaged active sites of [NiFeS]/[NiFeSe]-H 2 ases is described. Mono- and di-oxygenates (major and minor species, respectively) of the chalcogens result from exposure of the heterobimetallics to O 2 ; one was isolated and structurally characterized to have Ni–O–Se Ph –Fe–S connectivity within a 5-membered ring. A compositionally analogous mono-oxy species was implicated by ν (CO) IR spectroscopy to be the corresponding Ni–O–S Ph –Fe–S complex; treatment with O-abstraction agents such as P( o -tolyl) 3 or PMe 3 remediated the O damage. Computational studies (DFT) found that the lowest energy isomers of mono-oxygen derivatives of Ni(μ-EPh)(μ-SN 2 )Fe complexes were those with O attachment to Ni rather than Fe, a result consonant with experimental findings, but at odds with oxygenates found in oxygen-damaged [NiFeS]/[NiFeSe]-H 2 ase structures. A computer-generated model based on substituting − SMe for the N-CH 2 CH 2 S − sulfur donor of the N 2 S suggested that constraint within the chelate hindered O-atom uptake at that sulfur site. 

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5. Ligand and Linkage Isomers of Bis(ethylthiocarbamato) Copper Complexes with Cyclic C 6 H 8 Backbone Substituents: Synthesis, Characterization, and Antiproliferation Activity

   https://doi.org/10.1002/ejic.202300447  

   Bajaj, Kritika ; Andres, Sarah A. ; Hofsommer, Dillon T. ; Chekwube Michael, Okolocha ; Mashuta, Mark S. ; Bates, Paula J. ; Buchanan, Robert M. ; Grapperhaus, Craig A. ( September 2023 , European Journal of Inorganic Chemistry)

   A series of isomeric bis(alkylthiocarbamate) copper complexes have been synthesized, characterized, and evaluated for antiproliferation activity. The complexes were derived from ligand isomers with 3‐methylpentyl (H₂L²) and cyclohexyl (H₂L³) backbone substituents, which each yield a pair of linkage isomers. The thermodynamic products CuL^2a/3ahave two imino N and two S donors resulting in three five‐member chelate rings (555 isomers). The kinetic isomers CuL^2b/3bhave one imino and one hydrazino N donor and two S donors resulting in four‐, six‐, and five‐member rings (465 isomers). The 555 isomers have more accessible Cu^II/Ipotentials (E_1/2=−811/−768 mV vs. ferrocenium/ferrocene) and lower energy charge transfer bands than their 465 counterparts (E_1/2=−923/‐854 mV). Antiproliferation activities were evaluated against the lung adenocarcinoma cell line (A549) and nonmalignant lung fibroblast cell line (IMR‐90) using the MTT assay. CuL^2awas potent (^A549EC₅₀=0.080 μM) and selective (^IMR‐90EC₅₀/^A549EC₅₀=25) for A549. Its linkage isomer CuL^2bhad equivalent A549 activity, but lower selectivity (^IMR‐90EC₅₀/^A549EC₅₀=12.5). The isomers CuL^3aand CuL^3bwere less potent with^A549EC₅₀ values of 1.9 and 0.19 M and less selective with^IMR‐90EC₅₀/^A549EC₅₀ratios of 2.3 and 2.65, respectively. There was no correlation between reduction potential and A549 antiproliferation activity/selectivity.

    

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