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1. The versatility of 1,4,8,11-tetraazacyclotetradecane (cyclam) in the formation of compounds of Co 2+ , Ni 2+ , Cu 2+ , and Zn 2+ with metal ions in and out of the cyclic ligand ring

   https://doi.org/10.1515/zkri-2023-0026  

   Noor, Mah ; Chah, Hamza ; Tresp, David ; Bernal, Ivan ; Lalancette, Roger A. ( June 2023 , Zeitschrift für Kristallographie - Crystalline Materials)

   Herein we report the results of preparing metal compounds (where the metal ions are Co2+, Ni2+, Cu2+, Zn2+) with the cyclic ligand 1,4,8,11-tetraazacyclotetradecane [cyclam] under a variety of conditions of metal-ligand ratios and solvent media. In all cases, we used metal Cl2 . nH2O salts (except for anhydrous CoCl2), as specified. Outcome: we isolated species with a four-coordinate metal in the N4 cavity of the ligand alone, and also with either one or two additional axial ligands. Those axial ligands can be (a) a single chloride, leading to penta-coordinated+ products; (b) two chlorides, leading to octahedral-neutral compounds; (c) two waters, giving rise to hexa-coordinated [(cyclam)metal(H2O)2]2+ species. Finally, in the case of HCl added to the reaction medium, the cyclam can be di-protonated and appears as [(cyclam)H2]2+ in the crystals. With such a variety of products, it is not surprising that since the metal coordination numbers vary, the cyclam ligand stereochemistries are thereby affected. Interestingly, the [(cyclam)metal] species are invariably hydrogen-bonded to one another in infinite strings of two kinds: (1) those for which the crystal’s Z’ = 1 have single strings; (2) when Z’ = 2, there is a pair of homogeneous strings attached to one another by a variety of hydrogen-bonding linkages. Finally, we observed an interesting pair of hydroxonium cations: the first is hydoxonium cations in a pleated 2-D sheet consisting of fused pentagons located between sheets of [(cyclam)metal] moieties; the second one is an infinite string of composition (H3O+)-(H2O)-(H3O+)-(H2O)-(H3O+)-(H2O)-(H3O+). 

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2. A Family of Cross-Conjugated Polyenynes Capped by Co III (cyclam): Syntheses, Molecular and Electronic Structures

   https://doi.org/10.1021/acs.organomet.9b00313  

   Natoli, Sean N. ; Zeller, Matthias ; Ren, Tong ( June 2019 , Organometallics)
3. Magneto-structural Correlations in Ni 2+ –Halide···Halide–Ni 2+ Chains

   https://doi.org/10.1021/acs.inorgchem.1c02483  

   Blackmore, William J. A. ; Curley, Samuel P. M. ; Williams, Robert C. ; Vaidya, Shroya ; Singleton, John ; Birnbaum, Serena ; Ozarowski, Andrew ; Schlueter, John A. ; Chen, Yu-Sheng ; Gillon, Beatrice ; et al ( December 2021 , Inorganic Chemistry)
4. Distinct Bimetallic Cooperativity Among Water Reduction Catalysts Containing [Co III Co III ], [Ni II Ni II ], and [Zn II Zn II ] Cores

   https://doi.org/10.1002/chem.202104426  

   Morgan, Fredricka ; Schaugaard, Richard ; Anderson, Dennis ; Schlegel, H. Bernhard ; Verani, Cláudio N. ( March 2022 , Chemistry – A European Journal)

   Three binuclear species [LCo^III₂(μ‐Pz)₂](ClO₄)₃(1), [LNi^II₂(CH₃OH)₂Cl₂]ClO₄(2), and [LZn^II₂Cl₂]PF₆(3) supported by the deprotonated form of the ligand 2,6‐bis[bis(2‐pyridylmethyl) amino‐methyl]‐4‐methylphenol were synthesized, structurally characterized as solids and in solution, and had their electrochemical and spectroscopic behavior established. Species1–3had their water reduction ability studied aiming to interrogate the possible cooperative catalytic activity between two neighboring metal centers. Species1and2reduced H₂O to H₂effectively at an applied potential of −1.6 V_Ag/AgCl, yielding turnover numbers of 2,820 and 2,290, respectively, after 30 minutes. Species3lacked activity and was used as a negative control to eliminate the possibility of ligand‐based catalysis. Pre‐ and post‐catalytic data gave evidence of the molecular nature of the process within the timeframe of the experiments. Species1showed structural, rather than electronic cooperativity, while species2displayed no obvious cooperativity. DFT methods complemented the experimental results determining plausible mechanisms.

    

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5. Ab initio determination of a simultaneous dual-ion charging mechanism for Ni 0.25 Mn 0.75 O 2 through redox reactions of Ni 2+ /Ni 4+ and O 2- /O -

   https://doi.org/10.1039/D2TA03938A  

   Shepard, Robert ; Brennan, Scott ; Juran, Taylor R ; Young, Joshua ; Smeu, Manuel ( July 2022 , Journal of Materials Chemistry A)

   Over recent years, great efforts have been made to push the limits of layered transition metal oxides for secondary battery cathodes. This is particularly true for overall capacity, which has reached a terminal theoretical value for many materials. One avenue for increasing this capacity during charging is the intercalation of anions post cation deintercalation. This work investigates the charging mechanism of the P3-Na0.5Ni0.25 Mn0.75O2 cathode material through cation (Na) deintercalation and anion (ClO4) intercalation by means of density functional theory. The calculations corroborate experimental findings of increased capacity (135 mAh g-1 to 180 mAh g-1) through the intercalation of anions. However, this work demonstrates that a process of simultaneous cation deintercalation/anion intercalation is the primary charging mechanism, with charge compensation reactions of Ni2+/Ni4+ and O2-/O- occurring within the cathode material. To elucidate this simultaneous process, a novel method for computationally determining anion voltage in which one must consider full electrolyte interactions is proposed. Based on the results, it is believed that a simultaneous cation deintercalation/anion intercalation mechanism provides one potential avenue for the discovery of the next generation of secondary batteries. 

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