Conversion of Isocyanide to Amine in The Presence of Water and Hg(II) Ions: Kinetics and Mechanism as Detected by Fluorescence Spectroscopy and Mass Spectrometry

Abstract

Aromatic isocyanides including isocyanonaphthalene derivatives have been proven to be very effective fluorescent sensors for the quantification of Hg(II) ions in water. Thus, the reaction of 1,5-isocyanoaminonaphthalene (1,5-ICAN), which is one of the most important members of this family, with water and HgCl2 as the oxidation agents, was studied by fluorescence spectroscopy and mass spectrometry in order to get deeper insight into the kinetics and mechanistic details of this complex reaction. The reactions of 1,5-ICAN with water and HgCl2 were performed in various water/co-solvent mixtures of different compositions. The co-solvents used in this study were both aprotic solvents including tetrahydrofuran, acetonitrile and N,N-dimethylformamide and protic solvents, such as ethanol and 2-propanol. It was found that in aprotic solvents the conversion of the isocyano group to amino moiety takes place, while in protic solvents the corresponding carbamate (urethane) group is formed in addition to the amino moiety. The variation of the resulting fluorescence intensities versus time curves were described using an irreversible, consecutive reaction model, in which the formation of isocyanate and carbamic acid intermediates, as well as diamino and carbamate (in the case of protic solvents) products were assumed. The formation of these intermediates and products was unambiguously confirmed by mass spectrometric measurements. Furthermore, by fitting the model to the experimental fluorescence versus time curves, the corresponding rate coefficients were determined. It was observed that the overall rate of transformation of the isocyano group to amino moiety increased with the water concentration and the polarity of the co-solvent. It was also supported that formation of diamino and carbamate derivatives in protic solvents takes place simultaneously and that the ratio of the amino to the carbamate function increased with the increasing water concentration. In addition, with an extension, the model presented herein proved to be capable of describing the kinetics of the transformation of 1,5-diisocyanonaphthalene (1,5-DIN) into 1,5-diaminonaphthalene (1,5-DAN) in the mixtures of water/aprotic solvents.

Design and Synthesis of Dipeptidomimetic Isocyanonaphthalene as Enhanced-Fluorescent Chemodosimeter for Sensing Mercury Ion and Living Cells

“…According to similar mechanism studies (Adamoczky, et al, 2020;Nagy, et al, 2019;Zhang, et al, 2018) which involve aromatic isocyanides as high effective sensors for the quantification of target metal Hg 2+ , the sensing mechanism can be also speculated Figure 5 shows the 13 C NMR spectrum of free NpI in CDCl 3 , the ester-, amide-carbonyl, and isocyanic carbon signals were clearly discernible at δ 172, 166, and 165 ppm, respectively. However, upon the addition of a certain amount of HgCl 2 , the signal intensity of the isocyano group gradually disappeared at δ 165 ppm.…”

“…According to similar mechanism studies ( Adamoczky, et al, 2020 ; Nagy, et al, 2019 ; Zhang, et al, 2018 ) which involve aromatic isocyanides as high effective sensors for the quantification of target metal Hg 2+ , the sensing mechanism can be also speculated to the Hg 2+ -induced hydration of isocyano group to amino group in water. To verify this conversion process, the fluorescence response of precursor compound, i.e., intermediate 1, was firstly investigated toward Hg 2+ under the identical measurement experimental condition of dipeptidomimetic NpI sensor.…”

“…Isocyanides have also attracted the attention of coordination chemists due to their strong σ-donor and weak π-acceptor properties ( Boyarskiy, et al, 2015 ; Yamamoto, 1980 ), and for advances in the synthesis and application of helical polymers, and the screw-sense polyisocyanides have been extensively used to the living polymerization of the corresponding isocyanide monomers ( Wang, et al, 2018c ; Zhou, et al, 2021 ). Notably, the chemical reactions based on the isonitrile group have recently been exploited for the design of fluorescent Hg 2+ probes ( Adamoczky, et al, 2020 ; Nagy, et al, 2019 ; Zhang, et al, 2018 ), which involves the Hg 2+ -mediated conversion of isonitrile to the amino group. Only two isocyano-functionalized fluorescent probes thay display distinct optical response have been explored.…”

The Physical Chemistry and Chemical Physics (PCCP) Section of the International Journal of Molecular Sciences in Its Publications: The First 300 Thematic Articles in the First 3 Years

“…Thematic Area 2 includes 22 articles, namely [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ], the typification of which is shown in Table 3 . With some degree of conventionality, it is possible to subdivide the articles published here into two main groups, namely, articles devoted to the study of the kinetics of processes in which any chemical transformations are decisive, and articles devoted to the study of the kinetics of processes in which chemical transformations are either not decisive or absent altogether.…”

“…With some degree of conventionality, it is possible to subdivide the articles published here into two main groups, namely, articles devoted to the study of the kinetics of processes in which any chemical transformations are decisive, and articles devoted to the study of the kinetics of processes in which chemical transformations are either not decisive or absent altogether. Among the articles of the first group, in turn, two categories can be distinguished, in the first of which are the clear majority; the processes related to them were considered in the articles [ 29 , 30 , 31 , 32 , 33 , 35 , 37 , 42 , 43 , 44 , 45 , 46 , 47 ]. For example, in [ 29 ], the kinetics of the aldol condensation of benzaldehyde and heptanal in liquid-phase systems using various solvents was characterized, and a very pronounced effect of the solvent was noted for a given set of identical kinetic parameters (i.e., the same kinetics of the liquid phase can lead to different values of conversion and yield of reaction products depending on the choice of solvent).…”