The phosphorylation of imidazole by two activated phosphate diesters and a triester gives phosphorylimidazole derivatives that are stable enough in aqueous solution to be observed and identified by ESI-MS/MS and NMR. Half-lives ranging from hours to days (in the case of the monoethyl ester) show that it is possible to design molecules with variable half-lives with potential to be used for biological intervention experiments as possible inhibitors of biosignaling processes or as haptens for the generation of antibodies.

The reaction between the benzohydroxamate anion (BHO(-)) and bis(2,4-dinitrophenyl)phosphate (BDNPP) has been examined kinetically, and the products were characterized by mass and NMR spectroscopy. The nucleophilic attack of BHO(-) follows two reaction paths: (i) at phosphorus, giving an unstable intermediate that undergoes a Lossen rearrangement to phenyl isocyanate, aniline, diphenylurea, and O-phenylcarbamyl benzohydroxamate; and (ii) on the aromatic carbon, giving an intermediate that was detected but slowly decomposes to aniline and 2,4-dinitrophenol. Thus, the benzohydroxamate anion can be considered a self-destructive molecular scissor since it reacts and loses its nucleophilic ability.

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The high rate of spontaneous hydrolysis of tris-2-pyridyl phosphate (TPP) is explained by the activating effects of the non-leaving ("spectator") groups on P-OAr cleavage, and not by intramolecular catalysis. Previous work on phosphate-transfer reactions has concentrated on the contributions to reactivity of the nucleophile and the leaving group, but our results make clear that the effects of the non-leaving groups on phosphorus can be equally significant. Rate measurements for three series of phosphate triesters showed that sensitivities to the non-leaving groups are substantial for spontaneous hydrolysis reactions, although significantly smaller for reactions with good nucleophiles. There are clear differences between triaryl and dialkyl aryl triesters in sensitivities to leaving and non-leaving groups with the more reactive triaryl systems showing lower values for both β(LG) and β(NLG). Intramolecular catalysis of the hydrolysis of TPP by the neighbouring pyridine nitrogens is insignificant, primarily because of their low basicity.

We report a novel pKa determination for different graphene-like samples: graphene oxide (GO), reduced GO (rGO), graphene nanoribbons (GNR), oxidized GNR (GONR), thiol- and imidazole-functionalized GO (GOSH and GOIMZ, respectively) and thiol-functionalized GONR (GONRSH). Using the specialized computational program BEST7 for treating titration curves, pKas for different functional groups were discriminated (confirmed by infrared spectra) and their composition quantified. Overall, three equilibria were distinguished, two relative to carboxylic acids exhibiting different acidic degrees (pKa1∼4.0 and pKa2∼6.0) and one relative to alcohols (pKa4∼10.0). Upon functionalization on carboxylate sites, thiol (pKa(GOSH/GONRSH)=6.7) and imidazole (pKa(GOIMZ)=6.6) moieties were discerned, followed by a decrease of their carboxylate percentage (compared to the precursors), thus allowing determining the degree of functionalization (48% and 36% of thiol content for GOSH and GONRSH respectively, and 29% of imidazole for GOIMZ). The proposed method is innovative and simpler when compared to the traditional tools usually employed to quantify chemical functionalization.

The bifunctionalization of graphene oxide (GO) has attracted attention as a promising tool for broadening applications, despite its many challenges, especially regarding site-specific reactions. Herein, we obtained mono-and bifunctionalized GO containing thiol and imidazole groups that were anchored on the carboxylic acid sites of GO via amidation reactions. We varied the bifunctionalization methodology and showed that consecutive addition of the reagents (containing imidazole and thiol groups) led to materials with higher degrees of functionalization, in contrast to their simultaneous addition. The functionalized materials were evaluated as nanocatalysts in the neutralization reaction of a toxic organophosphate. Also, it was evidenced that the effect of the mono-and bifunctionalized materials on the catalytic outcomes gives insight toward neighboring effects. All catalysts were effective in the reaction studied with the monofunctionalized materials (containing thiol or imidazole groups) showing similar activity. Among the bifunctionalized materials (with both thiol and imidazole moieties), the one with the lower degree of functionalization showed the best performance. This was attributed to a combination of mechanisms, strongly dependent on the neighboring groups: attraction on the GO surface, nucleophilic catalysis by thiol/imidazole groups, and bifunctional intramolecular catalysis, for example, by thiol and imidazole groups, assisting potential nucleophilic hydroxyl groups. Oddly, the bifunctionalized materials with the higher degree of functionalization did not show the most prominent activity; they were actually similar to the monofunctionalized ones. This can be attributed to the inhibition or hindering of some of the proposed mechanisms due to steric effects or a nonideal positioning of the groups. A lot remains to be clarified in this field, but one thing is clear: a higher degree of functionalization should not always be pursued because the application of the material is what should guide what characteristics should be determined. Several other applications should be impacted by neighboring effects, which are directly influenced by the functionalization procedure.

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Synthesis of functionalized graphene-based thin films through the interfacial route, their nanocomposites with Ag-NPs, and their multiple applications.