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1. Measurements of ¹⁸ O ¹⁸ O and ¹⁷ O ¹⁸ O in the atmosphere and the role of isotope-exchange reactions: ¹⁸ O ¹⁸ O AND ¹⁷ O ¹⁸ O IN THE ATMOSPHERE

   https://doi.org/10.1029/2012JD017992  

   Yeung, Laurence Y.; Young, Edward D.; Schauble, Edwin A. (September 2012, Journal of Geophysical Research: Atmospheres)
2. Measurement of the ²⁷ Al ⁺ and ⁸⁷ Sr absolute optical frequencies

   https://doi.org/10.1088/1681-7575/abd040  

   Leopardi, Holly; Beloy, Kyle; Bothwell, Tobias; Brewer, Samuel M; Bromley, Sarah L; Chen, Jwo-Sy; Diddams, Scott A; Fasano, Robert J; Hassan, Youssef S; Hume, David B; et al (February 2021, Metrologia)

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3. The Role of Ozone Vibrational Resonances in the Isotope Exchange Reaction ¹⁶ O ¹⁶ O + ¹⁸ O → ¹⁸ O ¹⁶ O + ¹⁶ O: The Time-Dependent Picture

   https://doi.org/10.1021/acs.jpca.9b06139  

   Yuen, Chi Hong; Lapierre, David; Gatti, Fabien; Kokoouline, Viatcheslav; Tyuterev, Vladimir G. (August 2019, The Journal of Physical Chemistry A)
4. Probing the Ni ²⁺ ‐selective Response of Fluorescent Probe NiSensor‐1 with the NiCast Photocaged Complex ^{† ‡}

   https://doi.org/10.1111/php.13567  

   Hickey, Erin E.; Kennedy, Daniel P.; Gwizdala, Celina; Basa, Prem N.; Müller, Peter; MacDonald, John; Burdette, Shawn C. (December 2021, Photochemistry and Photobiology)

   Abstract CTEA (N,N‐bis[2‐(carboxylmethyl)thioethyl]amine) is a mixed donor ligand that has been incorporated into multiple fluorescent sensors such as NiSensor‐1 that was reported to be selective for Ni²⁺. Other metal ions such as Zn²⁺do not produce an emission response in aqueous solution. To investigate the coordination chemistry and selectivity of this receptor, we prepared NiCast, a photocage containing the CTEA receptor. Cast photocages undergo a photoreaction that decreases electron density on a metal‐bound aniline nitrogen atom, which shifts the binding equilibrium toward unbound metal ion. The unique selectivity of CTEA was examined by measuring the binding affinity of NiCast and the CTEA receptor for Ni²⁺, Zn²⁺, Cd²⁺and Cu²⁺under different conditions. In aqueous solution, Ni²⁺binds more strongly to the aniline nitrogen atom than Cd²⁺; however, in CH₃CN, the change in affinity virtually disappears. The crystal structure of [Cu(CTEA)], which exhibits a Jahn–Teller–distorted square pyramidal structure, was also analyzed to gain more insight into the underlying coordination chemistry. These studies suggest that the fluorescence selectivity of NiSensor‐1 in aqueous solution is due to a stronger interaction between the aniline nitrogen atom and Ni²⁺compared to other divalent metal ions except Cu²⁺. 

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5. 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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