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1. Oxoiron(IV) Tetramethylcyclam Complexes with Axial Carboxylate Ligands: Effect of Tethering the Carboxylate on Reactivity

   https://doi.org/10.1021/acs.inorgchem.6b02659  

   Bigelow, Jennifer O. ; England, Jason ; Klein, Johannes E. ; Farquhar, Erik R. ; Frisch, Jonathan R. ; Martinho, Marlène ; Mandal, Debasish ; Münck, Eckard ; Shaik, Sason ; Que, Lawrence ( March 2017 , Inorganic Chemistry)
2. Zinc–Carboxylate Binding in Mixed Octadecanoic Acid and Octadecanol Monolayers on Proxy Seawater Solution Surfaces

   https://doi.org/10.1021/acsearthspacechem.1c00272  

   Auvil, Nicole C. ; Vazquez de Vasquez, Maria G. ; Allen, Heather C. ( October 2021 , ACS Earth and Space Chemistry)
3. Disposable paper strips for carboxylate discrimination

   https://doi.org/10.1039/d0an00137f  

   Xu, Yifei ; Bonizzoni, Marco ( January 2020 , The Analyst)

   We describe a method for the differentiation of carboxylate anions on disposable paper supports (common printer paper, filter paper, chromatography paper), based on differential patterns of interactions between carboxylates and a fluorescent sensing system. The sensor was built from commercially available components, namely a polycationic fifth generation amine-terminated poly(amidoamine) dendrimer (PAMAM G5) and a small organic fluorophore (calcein) through non-covalent interactions. The assay's physical dimensions were chosen to conform to the microwell plate standard so detection could be carried out on widely available plate reader instrumentation. The sensing complex was first deposited in spots on a paper support to prepare the sensor strip; a carboxylate solution was then loaded on each spot. Nuanced changes in fluorescence were associated with carboxylate binding to the PAMAM dendrimer, characteristic of the structure and affinity of each carboxylate. Such signal changes, interpreted through Linear Discriminant Analysis (LDA), contained enough information to recognize and successfully discriminate most anions in the panel. Among the substrates we tested, chromatography paper was the most promising. The relationship between the structure of the carboxylates and the patterns giving rise to their differentiation was also discussed. Finally, the long-term stability (“shelf life”) of the pre-assembled [calcein·dendrimer] sensing system was found to be excellent when deposited on paper support. 

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4. Molecular-level origin of the carboxylate head group response to divalent metal ion complexation at the air–water interface

   https://doi.org/10.1073/pnas.1818600116  

   Denton, Joanna K. ; Kelleher, Patrick J. ; Johnson, Mark A. ; Baer, Marcel D. ; Kathmann, Shawn M. ; Mundy, Christopher J. ; Wellen Rudd, Bethany A. ; Allen, Heather C. ; Choi, Tae Hoon ; Jordan, Kenneth D. ( July 2019 , Proceedings of the National Academy of Sciences)

   We exploit gas-phase cluster ion techniques to provide insight into the local interactions underlying divalent metal ion-driven changes in the spectra of carboxylic acids at the air–water interface. This information clarifies the experimental findings that the CO stretching bands of long-chain acids appear at very similar energies when the head group is deprotonated by high subphase pH or exposed to relatively high concentrations of Ca 2+ metal ions. To this end, we report the evolution of the vibrational spectra of size-selected [Ca 2+ ·RCO 2 − ] + ·(H 2 O) n =0 to 12 and RCO 2 − ·(H 2 O) n =0 to 14 cluster ions toward the features observed at the air–water interface. Surprisingly, not only does stepwise hydration of the RCO 2 − anion and the [Ca 2+ ·RCO 2 − ] + contact ion pair yield solvatochromic responses in opposite directions, but in both cases, the responses of the 2 (symmetric and asymmetric stretching) CO bands to hydration are opposite to each other. The result is that both CO bands evolve toward their interfacial asymptotes from opposite directions. Simulations of the [Ca 2+ ·RCO 2 − ] + ·(H 2 O) n clusters indicate that the metal ion remains directly bound to the head group in a contact ion pair motif as the asymmetric CO stretch converges at the interfacial value by n = 12. This establishes that direct metal complexation or deprotonation can account for the interfacial behavior. We discuss these effects in the context of a model that invokes the water network-dependent local electric field along the C–C bond that connects the head group to the hydrocarbon tail as the key microscopic parameter that is correlated with the observed trends. 

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5. Purification and In Situ Ligand Exchange of Metal-Carboxylate-Treated Fluorescent InP Quantum Dots via Gel Permeation Chromatography

   https://doi.org/10.1021/acs.jpclett.7b01772  

   Roberge, Adam ; Stein, Jennifer L. ; Shen, Yi ; Cossairt, Brandi M. ; Greytak, Andrew B. ( August 2017 , The Journal of Physical Chemistry Letters)