The project is devoted to the solution of global problems of humanity and deals with the advanced research of the modern principles and laws of non-covalent interactions for further application in the development of smart materials for prospective technologies. The implementation of the project includes a fundamental research aimed at the accumulation of knowledge with subsequent project-oriented development of new methods and approaches to the design of 2D and 3D materials. Thus, the core of the project is non-covalent interactions that will become the basis for further development and implementation of materials.
Within the implementation of the project we have been continuing a study of diaryliodonium metallate that has been launched with an earlier published paper (Cryst. Growth Des., 2021, 21 (2), 1136–1147) by the participants of the project covering diaryliodonium tetrachloroaurates(III). Tetrachloroplatinate (II) is an isoelectronic analog of tetrachloroaurate(III) therefore within the project we have synthesized and characterized using X-ray structural analysis based on monocrystals (XSA) a series of four diaryliodonium tetrachloroplatinates(II) [Ar1IAr2]2[PtCl4] (Ar1 = Ph, Ar2 = Ph; Ar1 = 2,4,6-(MeO)3C6H2, Ar2 = Ph, 4-MeC6H4, 4-ClC6H4). Diaryliodonium tetrachloroplatinates were synthesized during an exchange reaction between corresponding trifluoroacetate and K2PtCl4, while trifluoroacetates were synthesized using an original method published in (Beilstein J. Org. Chem., 2018, 14 (1), 849-855). In all the instances, the formation of heterotrimer electrically neutral clusters has been found in crystals. The integrity of these clusters is ensured by means of the formation interionic halogen bonds. In three out of four compounds, the nature of these bonds is similar – it is an interaction between the iodonium center and the C−I∙∙∙Cl−Pt chloride ligands.
A completely different structure of the heterotrimer was detected for [PhI(2,4,6-(MeO)3C6H2)]2[PtCl4], where interionic association is implemented by means of unique trifurcation interactions of C−I∙∙∙(Cl−Pt−Cl), while the main contribution is made by C−I∙∙∙Pt, according to the conducted quantum chemical computations. Despite the fact that previously halogen bonds with platinum(II) have already been described, including in works published by participants of the project, these halogen bonds between hypervalent iodine(III) and with the mcenter have been detected for the first time. The results of the research of diaryliodonium tetrachloroplatinates(II) have been published in an article in the Crystal Growth & Design journal (Q1, IF = 4.076) published b the American Chemical Society.
The research of diaryliodonium metallates was continued with the use of modified cations in which not only I(III) but also additional halogen atoms in substitutes can be used as electrophilic centers, which was demonstrated in the research of new tetrachloroaurates(III) [(4-XC6H4)2I][AuCl4] (X = Cl, Br). Along with a multitude of C−I∙∙∙Cl−Au and C−I∙∙∙(Cl−Au−Cl) in crystals of these compounds we have found unique C−X∙∙∙Au (X = Cl, Br) and C−Br∙∙∙(Cl−Au) contacts that are the first examples of halogeic bonds with gold(III) as the nucleophilic center. The nature of the interactions was confirmed by subsequent theoretical computations. Taking note o the above-mentioned interactions of C−I∙∙∙(Cl−Pt−Cl) with tetrachloroplatinate(II), we can say that it is namely the use of diaryliodonium cations that allowed to find one more common property of [PtCl4]2− and [AuCl4]– isoelectronic anions – the capability of acting as nucleophiles through the metallocenter, forming halogen bonds
As part of researching the reaction capability of these compounds, it has been found that when solutions of the phenyl(mesityl)iodonium tetrachloroaurate complexes are stored, sedimentation occurs and the solution changes its color from yellow to bright pink. These observations allowed to suggest that micro- and nanodimensional gold-containing products are formed under the impact of external factors (light and temperature).
At the first stage of the research we have managed to confirm the stability of the complex itself in methanol by means of UV-Vis spectroscopy. For instance, when the solution is stored in a refrigerator for six days, a slight decrease of the absorption intensity in the 300-350 nm region. After that the methanol solution of the complex with a concentration of 1 mmol was exposed to 275 nm and 365 nm UV radiation for 6 to 9 hours. Therefore, we have accumulated kinetic data on salt decomposition during exposure to radiation.
Under the impact of 275 nm radiation a reduction of the absorption band in the 350 nm region and an intense increase of signal in the 450 nm region was detected. Additional experiments are required to determine the structure and composition of the produced objects whose absorption maximum corresponds to 450 nm. When a sample is exposed to light with a wavelength of 360 nm, we have found a sharp suppression of the band at 350 nm and a minor increase in the intensity of absorption in the 350 nm region, which corresponds to gold nanoparticles.
In the vast majority of cases of intermolecular interactions with gold(III) this metallocenter acts as the electrophile, but with the discovery of the C−X∙∙∙Au halogen bond, gold(III) can be classified as an amphiphilic center. For other d8-centers, such as platinum(II) and palladium(II), it is more typical to form precisely halogen bonds in their interactions with halogens that are covalently bound to carbon. However, in isomorphic crystals of cis-[MCl2(4-XC6H4NC)2] (M = Pd, X = Cl, Br; M = Pt, X = Br) complexes we have managed to detect a manifestation of electrophilic properties with respect to halogens in X−С bonds, which reveals itself in the formation of a M∙∙∙X−С semiccordination. The electrophilicity of metals with respect to halogens has been confirmed by subsequent theoretical computations. Along with these interactions, we have also found С−X∙∙∙X−С (X = Cl, Br) halogen bonds in crystals. The results of this research have been published in the Crystals journal (Q2, IF = 2.589) of the MDPI publishing house.
The formation of a halogen bond is also possible with other bromine-centered electrophiles. For example, we have demonstrated for the first time that 1,1,2,2-tetrabromoethane, like other bromoalkanes, can act as a donor of halogen bonds on the example of solvates of trans-[PtBr2(NCNR2)2]∙2(1,1,2,2-C2H2Br4) (R2 = Me2, (CH2)5). The nature of the bonds has been confirmed not only by X-ray structural analysis on monocrystals but also by subsequent theoretical computations that, in particular, confirmed the emergence of partial negative charge on molecules of 1,1,2,2-C2H2Br4 during the formation of halogen bonds. The results of this research have been published in an article in the Crystals journal (Q2, IF = 2.589) of the MDPI publishing house.
Halogen bonds of bromine-halogenide ligands have been found for the first time for the compound of hypervalent bromine — dibenzobromolium tetrachloraureate(II) — as well. According to X-ray structural analysis data, in the crystal of this compund a heterotetrameric cluster is formed that consists of two cations and two anions. Its integrity is ensured trough a C−Br∙∙∙Cl−Au and C−Br∙∙∙(Cl−Au−Cl) halogen bons as well as via a Au∙∙∙Cl−Au semicorrdination between two anions.
The project also explored other diaryliodonium metallates, namely, diphenyliodonium tetracyanonickelate(II) and tetracyanopalladate(II) [Ph2I][M(CN)4] (M = Ni, Pd) that form isomorphic crystals. Due to the formation of C−I∙∙∙N halogen bonds between ions, in both crystals infinite supramolecular chains with alternating cations and anions have formed. It is worth noting that angles around the nitrogen atoms I∙∙∙N≡С that are part of anions are from straight, which is surprising from the viewpoint of sp-hybridization of these atoms and the corresponding positioning of lone pairs. It is supposed that one of the explanations of such a geometry can be the reverse charge transfer from the iodine atom to the π-antibonding orbital of cyano groups that has been detected using theoretical computations.
Continuing the work of the members of our team in the research of diaryliodonium thiocyanates (Crystals, 2020, 10 (3), 230; Org. Chem. Front., 2020, 7, 2230–2242), we have produced a series of diaryliodonium selenocyanates [Ar1IAr2]SeCN, in which instead of sulfur another material, selenium, which heavier and therefore more polarizable and soft from the viewpoint of the HSAB theory. While in thiocyanates the absence of formation of the C−I∙∙∙S halogen bond during the structuring of the solid phase is possible, in all cases of diaryliodonium selenocyanate crystals we have found the C−I∙∙∙Se halogen bonds that is advantageous compared from the viewpoint of HSAB. In the vast majority of cases they, along with the C−I∙∙∙N halogen bond, lead to the formation of supramolecular heterotrimer clusters. It is worth noting that halogen bonds with SeCN− have been previously described only for compounds of monovalent iodine.
Similarly to the earlier described analogous thiocyanate, the [PhI(4-MeOC6H4)]SeCN compound also forms a more complex heterooctamer supramolecular cluster, however, a C−I∙∙∙Se halogen bonds and a C−I∙∙∙N halogen bond are still formed.
Thus, we have demonstrated the first examples of the formation of I…Se halogen bonds in compounds of hypervalent iodine (III).
We have synthesized a series iodonium salts with 1,2,4-oxadiazolones as counter-ions. The synthesis was performed by mixing of acetone solutions of initial compounds: a corresponding sodium oxydiazolone salt, and dibenzoiodolium triflate at room temperature. The resulting salts were classified by means of NMR 1Н, 13С and 19F spectroscopy as well as by high resolution mass spectrometry. The collected spectral data confirmed the suggested composition of the salts.
For two compounds (R = Me and Br) monocrystalline samples have been produced and their X-ray structural analysis has been performed. The produced structures are isomorphic hydrates. In both structures there are short contacts between the iodine atom and the oxygen atoms of oxadiazalone (O1) and water (O2). An analysis of the geometrical parameters (the I∙∙∙O distance and the (C–I∙∙∙O) angle) has demonstrated that these short contacts can be classified as halogen bonds. It is notable that the distance between the iodine and the oxygen of the water is sligthly shorter than with the oxygen of the oxadiazole.
Copper(I) complexes with azaheterocyclic ligands are in high demand in materials science [Science, 2019, 363(6427), 601-606; Chem. Comm., 2009, (44), 6774-6776; JACS, 2021, 142(45), 19161-19169]. Thus far, there are known copper(I) complexes with pyridines, pyrazoles, imidazoles, benzoimidazoles, benzooxazoles and triazoles, while there are no described examples of coordination compounds of copper(I) with oxadiazole ligands.
When a third component – copper(I) salt – is introduced, the reaction of oxadiazolone results in coordination compounds in which two oxadiazolone ligands are bound though a copper «bridge». We have synthesized and characterized 5 such complexes using spectral methods, including one dibenzbromonium salt derivative.
For all the complexes we have produced monocrystalline samples and conducted an E-ray structural analysis. In all 5 structures we could observe X∙∙∙O (X = I, Br) bonds between halogen and oxygen atoms of oxadiazolone ligand s.
Apart from that, an analysis of the produced structures indicated the presence of two types of packaging depending on the positioning of oxadiazolone ligands. For complexes with 4-MeOC6H4 substituents in oxadiazolone ligand oxygen atoms of two different complexes are involved in the halogen bond, while ligands have anti(trans)-placement with regard to the metallocenter (an intermolecular halogen bonds). For complexes with 4-tolyl and 5-tienyl substituted oxadiazolones, ligands have syn(cis)-placement with regard to the metallocenter, and both halogen bonds are «within» the molecule of the complex.
The production of complexes with acyclic iodonium salts turned out to be impossible due to arylation occurring in the process of crystallization. Therefore subsequently within the research of the interaction of acyclic iodonium salts with 1,2,4-oxadiazolones we have developed a method of copper-catalysed N-arylation with the use of noncyclic symmetric and asymetric iodine salts as arylating agents. The developed method allows to produce a wide range of products of various nature. An assessment of the factors influencing the selectivity N/O-arylation have shown a considerable contribution of sterical hinderances both in the structure of iodonium salts and in the structure of oxadiazolones, which can be indirectly proven by X-ray structural analysis data.
- The reaction of para-substituted oxadiazolones with sterically hindered dimethyl iodonium triflate leads to the formation of a mixture of products of N/O-arylation with low outputs. This fact can be explained by a decrease of the rate of N-arylation, which leads to arylation of oxygen which is less nucleophylic and more sterically available.
- Ortho-substituted react only forming a product of N-arylation with outputs starting from 43 per cent. This observation is indirectly explained by analyzing the crystal structure of the products. For instance, in the case of ortho-substituted products of arylation the angle between the planes of the heterocyclic ring (А) and the benzene ring (В) exceeds 55 degrees, which increases the sterical availability of nitrogen. For para-substituted products, the corresponding angle between the planes is less than 36 degrees.
The results of this work have been published in the Advanced Synthesis & Catalysis journal (Q1, IF=5.837).
This research started with the synthesis of cyclic imidazole-containing iodonium salts as substrates for subsequent crystallization. The methodology of the production has been developed earlier [J. Org. Chem. 2021, 86 (10), 7163]. A number of 4a-4e salts with outputs ranging from moderate to high.
The produced salts can be subsequently used crystal chemistry design. They are of interest for crystal chemistry due to the presence of not only iodine(III) as a donor of halogen bonds in the molecule, but also monovalent halogens in various locations of the benzene ring. Moreover, these salts include a pyridine nitrogen atom that can act both as the acceptor of the halogen bond and as an atom forming a coordination bond with metallocenters.
By coordinating with nitrogen and, accordingly, closing one of the σ-holes, these salts are also interesting for the study of halogen bonds in crystal chemistry.
Halogen, chalcogen and pnictogen-containing compounds have recently been attracting attention of chemists as organocatalysts and building blocks for the production of new materials based on nonvalent interactions. It is well-known that such compounds are able to organize various interactions, such as cation-π, interactions with nucleophiles, with ion pairs etc. Hence the development of methods of the synthesis of such compounds is an important task. As part of the search for donors of halogen bonds, special attention was paid to the development of new methods of the synthesis of organic selenides and combined donors of halogen bonds and chalcogen bonds.
Our researchers have synthesized a series of diaryliodonium salts using a known method [J. Org. Chem., 2017, 82(2), 1279-1284], which were introduced into further transformations. The simultaneous procedure constitutes subsequent arylation of the SeCN-anion [Org. Lett., 2017, 19(19), 5252-5255] with subsequent interaction with iodo(2,4,6-trimethoxy)benzene.
Using phenyl(1,3,5-trimethoxyphenyl)iodonium trifluoroacetate as a model substrate, we have selected the optimal conditions for the synthesis of phenyl(1,3,5-trimethoxyphenyl)selenide. By varying the solvent, the temperature and the base, we have demonstrated that a maximum output of 73 per cent can be achieved upon heating up to 80 degrees in the presence of pyridine in a hexafluorisopropanol medium.
In the optimal conditions we have managed to produce a wide range of aryl(1,3,5-trimethoxyphenyl)selenides with outputs of up to 92 per cent. Analysis of the impact of substituents demonstrates that the reaction proceeds with high outputs in the presence of electron-acceptor substituents, while introducing electron-donor substituents reduces the outputs to 26 per cent. Moreover, a significant decrease of the output of the product was observed in a meta-CF3-substituted substrate, which can be attributed to losses on the first stage due the high volatility of the intermediate product.
The produced diarylselenides have been described and identified using modern physical and chemical analysis methods.
Therefore, we have developed a method of the synthesis of aryl(1,3,5-trimethoxyphenyl)selenides that will be later studied as chalcogen bond donors. Nine new compounds have been produced whose output vary from acceptable to excellent depending on constituents.
A significant direction of the research of chalcogen bonds and halogen bonds is the design of new combined halogen bond donors. As part of this work, attention was directed towards methods of the development of methods of the syntheses of cyclic iodine salts that has a thiophene ring in its structure.
Using the known approaches, such as the Suzuki reaction [Green Chem., 2017, 19(20), 4798-4803] and diazotization-iodination [Synthesis, 2007, 2007(01), 81-84], we have managed to successfully produce a series of 3-(2-iodophenyl)thiophene with aggregate outputs of up to 67 per cent. According to the results, the oxidation of 3-(2-iodophenyl)thiophenes to corresponding salts occurs with the highest outputs when chloroperbenzoic acid is used. In these conditions we managed to produce four examples of previously unknown benzothieneiodolium trifluoroacetates. The produced compounds successfully enter anion exchange reactions, which has been demonstrated on a number of examples. The results of an X-ray structural analysis of benzothieneiodolium trifluoroacetate show the formation of chalcogen bonds and halogen bonds with the same oxygen atom (O1A), which signifies additional activation of the sulfur of thiophene by the iodonium center, while the sulfur is normally not inclined to form chalcogen bonds. An important feature of halogen bonds in benzotieniodolium triftoracetate is a bifuraction of the I1…O1A(O2A) halogen bond, which can be explained by the convergence of the anion and the cation due to an additional chalcogen bonds.
Therefore, our researchers were the first to develop a targeted method of the synthesis of combined donors of chalcogen bonds and halogen bonds based on cyclic iodonium salts. The close location of iodine(III) and sulfur allows to study the features of the combination of nonvalent interactions with common nucleophilic centers.
Among iodonium salts, zwitterion derivatives can be distinguished as a separate group [J. Fluor. Chem. 2003, 122 (1), 57–61; Tetrahedron Lett. 2009, 50 (44), 6072–6075]. For these materials, the assessment of the published X-ray structural analysis data indicates a high inclination of these compounds to form 1D and 2D supramolecular organizations. Within this research, we were paying special attention to the earlier unknown 4-(aryliodonium)benzenesulfonates. We have managed to collect X-ray structural analysis data for three zwitterions.
All the produced structures tend to forn A diners by establishing I…O halogen bonds between the phenyl rings following a «head-tail» pattern. For three out of the four produced structures it is typical to form 1D chains by binding dimers with two more halogen bonds in a «head-tail» pattern. It turned out to be significant that in the case of 4-(mesityl iodonium)benzenrsulfonate the formation of 1D pores containing the solvent can be observed. A further research of the properties of the material has demonstrated that drying the crystals can lead to their destruction.
Varying the conditions of crystallization of 4-(mesityl iodonium)benzosulfonate helped to produce a radically new structure of a 3D organic framework that is stable during drying. Similarly to the earlier produced 1D chains, the main structural motive are A dimers formed by I…O halogen bonds. However, in this case each dimer is bound to four others forming a complex structure containing hexagonal pores similar to a honeycomb. An assessment of the physical properties of this material has shown the possibility of drying while preserving the crystal structure, which demonstrates good prospects of such materials for materials chemistry.
Therefore, we have researched the supramolecular organization of new zwitterion salts of 4-(aryliodonium)benzenesulfonates that, as a rule, forn 1D chains in the solid phase. However, varying the conditions of crystallization allows to produce more complex 3D structures that are promising for materials chemisty.
As part of the continuing research of sulfonate derivatives of iodonium salts, we have assessed the feasibility of combining two different classes of polyvalent iodine compounds, such as iodonium salts and iodylobenzoles and iodoxybenzene. For this purpose, we have tried to produce iodonium salt with an anion based on 4-iodoxy benzene sulfonate.
In this case we observed a complex picture of intermolecular interactions with 13 various halogen bonds in the structure of the crystal, among which there are three C-I(III)...O-S bonds, four C-I(III)...O-I(V) bonds, a O-I(V)...OH2 bond, two O-I(V)...O-S bonds, two С-I(V)...O-I(V) bonds and one O-I(V)...O-I(V) bond. The length of the C-I(III)...O-I(V) contact is less than the sum of the van der Waals radii of the atoms and is equal to 2.773(4) Å and the contact angle is close to 180 degrees, amounting to 170.05(18) degrees., which strongly confirms the formation of a halogen bond between the C-I(III)...O-I(V) centers.
A distinct direction towards an increase in the complexity of the supremolecular assembly is the introduction of two-center acceptors into the structure of the iodonium salt. In this part of our work, we focused on studying the laws of interaction between iodinium cations and naphthalene disulfonates as two-center acceptors. The co-crystallization of diphenyliodonium and и dimesityl iodonium trifluoroacetate with 1,5- and 2,6-naphthalene disulfonates:
- In the case of 1,5-naphthalene disulfonates we could observe the formation of 1D chains by binding anions through I…O halogen bonds with four iodinium cations. An increase in the complexity of the structure is observed for dimesityl iodonium 1,5-naphthalene disulfonate due to the introduction of solvated water, but the main motive persists.
- Iodonium 2,6-naphthalene disulfonate are more inclined to form 2D layers. In this case it is hard to isolate some common structural fragment, however, we are planning to broaden the range of salts for a more comprehensive assessment of the impact of the anion on supramolecular assembly.
Consequently, we have found the laws of supramolecular assembly for diaryliodonium naphthalene disulfonates and demonstrated that the structure of the anion significnalty influences the dimensionality of the produced structure.
Organic carbonic acids are widely used for the synthesis and design of metallo-organic frameworks. Among such carbonic acids we can isolate terephthalic acid. Within this work we have conducted an assessment of the impact of terephthalate-anion on the supramolecular assembly in diaryliodonium salts.
We have managed to collect X-ray structural analysis data for two crystals. In both cases we observed the assembly in the form of 1D chains. In 4-chlorophenyl mesityl iodonium terephthalate the length of contacts amounted to, in the direction of 4-chlorophenyl and mesityl rings, 2.5968(19) Å and 2.7129(18) Å correspondingly, while the contact angles are 169.69(8) degrees and 167.41(8) degrees.
In bis(4-chlorophenyl)iodonium terephthalate, the main difference of 4-chlorophenyl mesityl iodonium terephthalate is a short bifurcate halogen bond with a length of 2.480(2) Å and an angle of 164.97(9) degrees. this fact can be related to an increase of the electrostatic potential in the σ-holes in the presence of a 4-chlorophenyl ring.
We have demonstrated the possibility of assembling supramolecular structures on the basis of diaryliodonium salts as halogen bond donors with the use 1D linkers relying on aromatic carboxylic acids.
In addition to the possibility of using terephatlic acid as «bridges» in supramolecular structures, this acid is also a part of the most widely used plastics of our time, polyethylene terephthalate (PET) [Green Chem., 2017, 19, 4737-4753]. The use of PET in the packaging industry has increased the production of this nonbiodegradable polymer, which has given rise to a serious environmental concern [Nat. Commun., 2020, 11, 3381].
PET recycling can be performed by mechanical means, but a drawback in this case is that the properties of plastic deteriorate, while chemical recycling is more profitable [Waste Management, 2017, 69, 24-58]. Chemical recycling implies depolymerization by hydrolysis. This process can be combined with iodination using the Tronov-Novikov reaction to produce a mixture of iodo-terephthalic acid and terephthalic acid, which can be used for the self-assembly of metallo-organic frameworks [Angew. Chem. Int. Ed. 2021, 60, 16279; J. Chem. Educ., 1971, 48(6), 405]. The produced metallo-organic frameworks (MOFs) with a halogen bond donor can demonstrate better sorption with respect to halogen-containing ecotoxicants.
A scheme has been proposed for producing a mixture of terephthalic acids.
The produced mixtures of terephthalic acids have been used for the synethsis of the zirconium MOF UiO-66 using the published methodology [Chem. Sci., 2016, 7, 6492-6498]. The formation of the crystalline phase of MOFs has been confirmed by X-ray phase analysis data and the presence of characteristic peaks found by infrared spectroscopy.
Using the produced metallo-organic frameworks in real-life sorption technologies can be hampered due to the granulometric composition [ACS Cent. Sci., 2017, 3(6), 554–563]. Therefore, a methodology has been developed for growing UiO-66 on the surface of PET.
We have produced a number of PET@UiO-66 MOFs. The formation of crystallites of MOFs on the surface has been studied using infrared spectroscopy, X-ray phase analysis. The samples have also been subjected to the measurement of the concentration of zirconium by means of mass-spectroscopy with inductively-bound plasma and obtaining images by scanning electron microscopy.
Thus, we have developed a scheme of the functional hydrolysis of used PET for the synthesis of a mixture of iodo-terephthalic acid and terephthalic acid, subsequently producing a MOF on the surface of PET.
To synthesize Koser's reagents, we have determined the optimal conditions of their production. In the reaction of different variations of oxidation systems, such as Oxone, m-CPBA, and the mixtures of solvents dichloromethane/HFIP and acetonitrile/HFIP in various temporal and temperature ranges. For instance, for the reaction that produces bis(hydroxy-tosyloxy)diiodoarene the optimal synthesis conditions turned out to be 3 equivalents of m-CPBA, 2.5 equivalents of p-TsOH in a dichloromethane/HFIP mixture at room temperature. We have also optimized the stage of the production of bis(diaryliodonium) triflate, where the best synthesis conditions turned out to be 2.2 equivalents of arene and 3 equivalents of TfOH in dichloromethane.
Our researchers have conducted an anion e xchange in produced triflates to iodide, bromide, chloride and thiocyanate anions. The structure of the produced compounds has been confirmed by means of modern physical and chemical analysis methods. The synthesized compounds were placed in crystallization conditions, and we already have accumulated data concerning the structure of triflates.
We have demonstrated the presence of a halogen contact using the XPS method.
Using tert-butyl nitrite as a diazotizing agent and acetone as a solvent, we have produced a target bromolium trifluoroacetate with a high output. It is notable that along with the research conducted by our team, a similar approach to the synthesis of bromolium salts has been published by Wencel-Delord in 2021 [Angew. Chem. Int. Ed.. 2021, 60(27), 14852-14857]. However, the procedure developed by the laboratory allows to obtain the target product with a better output (94 per cent) compared with the published method (29 per cent).
The produced bromolium trifluoroacetate has been successfully used for exchange with metallates based on gold and copper.
We have also conducted a research of processes of synthesis of derivatives of hypervalent bromine with the use of substrates containing N and О-coordinating centers.
The developed of methods has been commenced with a screening of methods of oxication and their applicability to the selected bromine-substituted substrates. Oxone, m-CPBA, NaIO4, NaBO3, NaClO were used as oxydizing agents in the temperature range between -10 and 70 оС. However, we have not managed to produce polyvalent bromine compounds.
As part of our study of the catalytic activity of diaryliodonium salts, we decided to investigate the reaction of ring-opening of donor-acceptor cyclopropanes by aromatic nucleophiles, to develop a methodology for conducting this transformation using catalysts based on compounds of hypervalent iodine and to determine the advantages and disadvantages of this approach.
To study the catalytic activity of diaryliodonium salts and the impact of various factors on the course of the process, we have selected the reaction with 1,3,5-trimethoxybenzene. As the catalyst we chose dibenziodolium bis-(trifluoromethanesulfon)imid, which demonstrates an acceptable solubility in most organic solvents and a high stability. We have studied the course of the reaction in various conditions, the conversion of the substrate was determined by gas chromatography mass spectrometry with the use of an internal standard.
When using such solvents as acetonitrile and methanol, the formation of the product of transofmation is observed only in trace amounts, which can be explained by a decrease of the activity of the catalyst due to the coordination of the solvent with the electrophilic center of the diaryliodonium cation. The use of 1,2-dichloroethane allowed to achieve a high conversion of the substrate, we have also established the reaction does not run in the absence of diaruliodonium salt in the reaction mixture, which allows to rule out the formation of catalytic amounts of HCl as the reason of this phenomenon. A full conversion of the substrate could be achiveved with the use of fluorobenzene, chlorobenzene and toluol as the solvents. If the catalyst load is decreased, an insignificant reduction of substrate conversion can be observed, while introducing trifluoromethanesulfonate salt leads to its significant decrease. It is noteworthy that it is possible to perform the reaction with sufficient efficiency without using a solvent, however, in this case a significant number of byproducs is formed.
If cyclopropane is used as a substrate that does not contain a donor aromatic fragment, the formation of only trace amounts of the product could be observed, which is coherent with existing data on the reaction capability of the donor-acceptor cyclopropanes of various structures.
Our researchers have proposed novel methods and approaches to building supramolecular structures based on stable organic radicals with the use of nonvalent interactions.
We are accumulating experimental samples to research them using EPR and SQUID.
A method has been developed for the production of a first noncovalent framework based on zwitterion iodonium salts.
We have formulated conclusions on the impracticability of the synthesis of N-coordinated iodanes, the research plan has been adjusted accordingly.
A design has been proposed for new chiral reagents based on hypervalent iodine for the production of target products.
A number of derivatives of perrhenates and pertechnetates for the study of the crystal structure.
Methods have been developed for the synthesis of iodinium salts as precursors for immobilization onto the surface. Additionally, methods have been developed for the modification of novel materials.
Education and career development:
On the grounds of the Laboratory, a laboratory of the synthesis of novel supramolecular structures. We are also planning to create a laboratory for the structural research with the use of a single crystal X-ray diffractometer.
- A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences, Institute of Chemistry of the Saint Petersburg State University, Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, N.D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences (Russia): 2nd International symposium «Noncovalent interactions in the synthesis, catalysis and crystal chemical design» within the initiative of the Russian Academy of Sciences «Towards the 300th anniversary of the Russian Academy of Sciences» (Moscow, 14-16 November 2022).
- Polytechnic University of Milan (Italy): academic internships of two laboratory staff members under the supervision of the leading scientist Giuseppe Resnati (2021, 2022 ).
- French National Centre for Scientific Research — CNRS: a joint grant in the form of a subsidy from the federal budget to conduct research by Russian scientific organizations and (or) higher educational orgniazaitons in collaboration with French organizations for the implementation of the federal program for bilateral and multilateral technological interaction («Functional recycling» of polymer waste for the creation of smart materials for environment protection and «green» power generation».
Field of studies
Time span of the project
Laboratory for Redox-active Molecular Systems
Kazan Scientific Center of Russian Academy of Sciences - (FRC KazSC of RAS)
Alabugin Igor Vladimirovich
Spin Hyperpolarisation Laboratory
International Tomography Center Siberian Branch of RAS - (ITC)
Laboratory of Microwave Activation of Catalytic Processes
N. D. Zelinsky Instituteof Organic Chemistry of RAS - (Zelinsky Institute)
Salmi Tapio Olavi