Thermodynamic Study of Dihydrogen Phosphate Dimerisation and Complexation with Novel Urea‐ and Thiourea‐Based Receptors

Bregović, Nikola; Cindro, N.; Frkanec, Leo; Užarević, Krunoslav; Tomišić, Vladislav

doi:10.1002/chem.201404091

Cited by 35 publications

(31 citation statements)

References 45 publications

(18 reference statements)

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“…1a ). Phosphate oligomerization has been seen in solution 38 , 39 even without receptors and was previously modelled 14 in acetonitrile as a simple monomer–dimer equilibrium ( K dimer = 2400 M –1 ) where 66% of the phosphate is dimerized at 1 mM. Presumably, the propensity of phosphate to oligomerize as well as the characteristics of the receptors will help determine the types of complexes it forms.…”

Section: Introductionmentioning

confidence: 99%

Phosphate–phosphate oligomerization drives higher order co-assemblies with stacks of cyanostar macrocycles

et al. 2018

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Section: Introductionmentioning

confidence: 99%

Phosphate–phosphate oligomerization drives higher order co-assemblies with stacks of cyanostar macrocycles

et al. 2018

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“…Namely, Perez‐Casas and Yatsimirsky have shown that in some cases the same data could be fitted to both “apparent association constant” and to the overall constant involving multiple equilibria including proton transfer with sufficient quality . These, and other authors pointed out the importance of self‐association of anions with their conjugate acids in non‐aqueous media and this equilibrium is also included in K app . The K app will serve for the comparison with literature data and those obtained by titration of selected benzoylthioureas ( BTU1 and BTU4 – 6 ) and neutral benzoylguanidines ( 4 and 6 ) prepared in this work.…”

Section: Resultsmentioning

confidence: 99%

Benzoylguanidines as Anion‐Responsive Systems

et al. 2018

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A series of benzoylguanidinium salts was prepared and the changes in UV/Vis spectra, triggered by the presence of anions, were investigated. All compounds undergo deprotonation with basic anions like dihydrogenphosphate and acetate in acetonitrile. The most pronounced spectral changes were obtained by deprotonation of N1‐benzoyl‐N3‐(p‐nitrophenyl) guanidinium chloride which shows the naked‐eye visible color change from colorless to yellow. Measured pKa(BH+) in acetonitrile ranges from 12–16, which is comparable to the pyridinium cations. The proton transfer equilibria were also tested in acetonitrile/water mixture where all but the most acidic derivatives showed pKa(BH+) of 4–6 units which corresponds to apparent association constants of 104–106 dm3 mol−1. UV/Vis spectra of neutral and protonated forms were modelled by the TD‐DFT approach using CAM‐B3LYP and PBE0 functionals and compared to CC2 results. In the case of CAM‐B3LYP, a parameter ω, defining amount of long‐range exchange correction, was varied to achieve the best agreement with the experimental spectra. The optimized ω parameters are 0.10 a0−1 for neutral benzoylguanidines and 0.20 a0−1 for neutral nitrobenzoyl and protonated systems. The larger ω parameter in the latter is ascribed to more pronounced charge transfer character of the HOMO‐LUMO transition – the one responsible for the lowest energy absorption band.

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“…As a control, no peaks were observed in the same region in studies conducted with perchlorate (Figure c) or when bisulfate (Figure d) was examined in the absence of cyanostar at near saturated concentrations (1 M). Furthermore, careful scrutiny of all prior works claiming the observation of H 2 PO 4 − dimers, did not find any corresponding signature of a hydrogen bonded −OH group.…”

Section: Figurementioning

confidence: 88%

“…Nevertheless, there are no direct observations of anion dimers in solution. With good reason, the authors of those works, Reinhoudt, Kubo, Fabbrizzi, Sessler, and Tomisič, took care to circumscribe these claims with caveats such as “tentatively assigned”. The idea that anions can be bound to each other in solution in a complex has yet to be substantiated.…”

Section: Figurementioning

confidence: 99%

“…We propose that the unique encapsulation environment inside the stacked pair of cyanostar macrocycles contributes to the observation and stability of the bisulfate dimer. All prior works, that proposed dimers of H 2 PO 4 − have solvent‐exposed receptors. That exposure may inhibit the observation of a proton resonance for the H 2 PO 4 − dimer on account of exchange processes.…”

Section: Figurementioning

confidence: 99%

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Anions Stabilize Each Other inside Macrocyclic Hosts

et al. 2016

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Contrary to the simple expectations from Coulombs law,Weinhold proposed that anions can stabilize each other as metastable dimers,y et experimental evidence for these species and their mutual stabilization is missing. We showt hat two bisulfate anions can form such dimers,w hichs tabilizee ach other with self-complementary hydrogen bonds,b ye ncapsulation inside apair of cyanostar macrocycles.The resulting 2:2 complex of the bisulfate homodimer persists across all states of matter,i ncluding in solution. The bisulfate dimersO H···O hydrogen bonding is seen in a 1 HNMR peak at 13.75 ppm, which is consistent with borderline-strong hydrogen bonds.The fundamental role of Coulombsl aw [1] is so ingrained in all areas of chemistry,b iology,a nd physics that it is the starting point for formulating hypotheses on the behavior of matter.Itgoverns the bonding in ionic solids,the salt-bridges that guide protein structure and function, and the movement of ions in electric fields.W er ely daily upon the notion that like charges repel (Figure 1a)a nd opposite charges attract ( Figure 1b). Fort his reason, it came as some surprise when Weinholdsr ecent theoretical work [2] and its commentary [3] suggested that anions can attract, instead of repel, each other to form dimers. [4] Propositions that anions can stabilize each other are rare and the only unequivocal evidence for this phenomenon is in the solid state. [5] We found over 80 examples of HSO 4 À dimers (see the Supporting Information, Table S1), [6] as well as chains of HSO 4 À , [7] water-bridged sulfates, [8] and oligomers [9] and cyclic forms of hydrogen-bonded phosphates. [10] However, many forces other than anti-electrostatic hydrogen bonding, [2] for example,ionic bonding,can stabilize such anion dimers in crystals.Insolution, where solvation overtakes ionic bonding, dimer salts do not appear to survive.S upramolecular encapsulation offers aw ay to stabilize unstable species in solution. [11] Theonly reports of complexes of anion dimers are with H 2 PO 4 À and are based on the observation of a2:1 ratio of phosphate and receptor.N evertheless,t here are no direct observations of anion dimers in solution. With good reason, the authors of those works,R einhoudt, [5a, 12] Kubo, [13] Fabbrizzi, [5b, 14] Sessler, [15] and Tomisič, [16] took care to circumscribe these claims with caveats such as "tentativelySupportinginformation (experimentald etails, determination of binding constants, X-ray data collection and DFT calculation details) and the ORCID identification number(s) for the author(s) of this article can be found under: http://dx.

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Thermodynamic Study of Dihydrogen Phosphate Dimerisation and Complexation with Novel Urea‐ and Thiourea‐Based Receptors

Cited by 35 publications

References 45 publications

Phosphate–phosphate oligomerization drives higher order co-assemblies with stacks of cyanostar macrocycles

Phosphate–phosphate oligomerization drives higher order co-assemblies with stacks of cyanostar macrocycles

Benzoylguanidines as Anion‐Responsive Systems

Anions Stabilize Each Other inside Macrocyclic Hosts

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