Symmetrical Noncovalent Interactions Br···Br Observed in Crystal Structure

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S S symmetry Communication SymmetricalCommunication Noncovalent Interactions Br···Br Symmetrical Noncovalent Interactions Br···Br ObservedObserved in Crystal Structure of Exotic Primary PeroxidePrimary Peroxide

Dmitrii S. Bolotin 1,*, Mikhail V. Il’in 1, Vitalii V. Suslonov 2 and Alexander S. Novikov 1,* Dmitrii S. Bolotin 1,*, Mikhail V. Il’in 1, Vitalii V. Suslonov 2 and Alexander S. Novikov 1,* 1 Institute of Chemistry, Saint Petersburg State University, Universitetskaya Nab. 7/9, Saint Petersburg 1 Institute of Chemistry, Saint Petersburg State University, Universitetskaya Nab. 7/9, 199034, Russia; Saint [email protected] 199034, Russia; [email protected] 2 2 CenterCenter for for X-ray X-ray Diffraction Diﬀraction Studies, Studies, Saint Saint Petersburg Petersburg State State University, University, Universitetskii Universitetskii Pr., Pr., 26, 26, Saint PetersburgSaint Petersburg 198504, 198504,Russia; Russia;[email protected] [email protected] * Correspondence:Correspondence: [email protected] [email protected] (D.S.B.), (D.S.B.); [email protected] [email protected] (A.S.N.) (A.S.N.) Received: 31 March 2020; Accepted: 14 April 2020; Published: date Received: 31 March 2020; Accepted: 14 April 2020; Published: 17 April 2020 Abstract: 4-Bromobenzamidrazone reacts with cyclopentanone giving Abstract: 4-Bromobenzamidrazone reacts with cyclopentanone giving 3-(4-bromophenyl)-5-(4- 3-(4-bromophenyl)-5-(4-peroxobutyl)-1,2,4-triazole, which precipitated as pale-yellow crystals peroxobutyl)-1,2,4-triazole, which precipitated as pale-yellow crystals during the reaction. The during the reaction. The intermolecular noncovalent interactions Br···Br in the single-crystal XRD intermolecular noncovalent interactions Br Br in the single-crystal XRD structure of the peroxo structure of the peroxo compound were studied··· theoretically using quantum chemical calculations compound were studied theoretically using quantum chemical calculations (ωB97XD/x2c-TZVPPall) (ωB97XD/x2c-TZVPPall) and quantum theory of atoms in molecules (QTAIM) analysis. These and quantum theory of atoms in molecules (QTAIM) analysis. These attractive intermolecular attractive intermolecular noncovalent interactions Br···Br is type I halogen···halogen contacts and noncovalent interactions Br Br is type I halogen halogen contacts and their estimated energy is their estimated energy is 2.2–2.5··· kcal/mol. These weak··· interactions are suggested to be one of the 2.2–2.5 kcal/mol. These weak interactions are suggested to be one of the driving forces (albeit driving forces (albeit surely not the main one) for crystallization of the peroxo compound during surely not the main one) for crystallization of the peroxo compound during the reaction and thus its the reaction and thus its stabilization in the solid state. stabilization in the solid state. Keywords: organic peroxide; triazole; DFT; QTAIM; noncovalent interactions; halogen bonding Keywords: organic peroxide; triazole; DFT; QTAIM; noncovalent interactions; halogen bonding

1.1. Introduction Introduction ShortShort halogen···halogen halogen halogen contacts contacts can can be be classified classiﬁed on on two two types types (Figure (Figure 11))[ [1].1]. Type Type I I is is simply ··· duedue to crystal packingpacking eeffects,ﬀects, whilewhile type type II II (halogen (halogen bonding) bonding) is is directed directed noncovalent noncovalent interactions interactions [2] [2]formed formed between between the theσ-hole σ-hole (electrophilic (electrophilic region) region) on theon the halogen halogen (Hal) (Hal) atom atom and and a nucleophile. a nucleophile.

FigureFigure 1. 1. TypesTypes of of Hal···Hal Hal Hal noncovalent noncovalent interactions. interactions. ··· AlthoughAlthough both types ofof HalHal···HalHal contactscontacts havehave similar similar abundance, abundance, today today halogen halogen bond bond (type (type II) ··· II)has has drawn drawn signiﬁcantly significantly higher higher attention attention and and similarly similarly toto hydrogenhydrogen bonds,bonds, metallophilic contacts, contacts, and stacking interactions, halogen bonding is now widely used in crystal growth and design and in Symmetry 2020, 12, x; doi: FOR PEER REVIEW www.mdpi.com/journal/symmetry

Symmetry 2020, 12, 637; doi:10.3390/sym12040637 www.mdpi.com/journal/symmetry Symmetry 2020, 12, x FOR PEER REVIEW 2 of 7 Symmetry 2020, 12, x 637 FOR PEER REVIEW 2 of 7 and stacking interactions, halogen bonding is now widely used in crystal growth and design and in andsupramolecular stacking interactions, engineering halogen [1,3–5]. bonding The is recently now widely published used in relevant crystal growth reviews and are design devoted and in to supramolecular engineering engineering [1 , [1,3–5].3–5]. The The recently recently published published relevant relevant reviews reviews are devoted are to devoted theoretical to theoretical approaches to Hal···Hal contacts [6,7] and also application of Hal···Hal contacts in theoreticalapproaches approaches to Hal Hal to contacts Hal···Hal [6,7 ] contacts and also [6,7] application and also of HalapplicationHal contacts of Hal···Hal in supramolecular contacts in supramolecular engineering··· [8–12], catalytic reactions [13], organometallic··· and coordination supramolecularengineering [8–12 engineering], catalytic reactions [8–12], [ 13 catalytic], organometallic reactions and [13], coordination organometallic chemistry and [14 – coordination18], polymer chemistry [14–18], polymer science [19], medical chemistry and drug discovery [20–23], and to the chemistryscience [19 ],[14–18], medical polymer chemistry science and drug [19], discovery medical [chemistry20–23], and and to thedrug involvement discovery of[20–23], Hal Hal and contacts to the involvement of Hal···Hal contacts in human function [24]. ··· involvementin human function of Hal···Hal [24]. contacts in human function [24]. In this communication, we describe symmetrical type I noncovalent interactions observed In this communication, we describe symmetrical type I noncovalent interactions observed between betweenIn this two communication, bromine atoms, wewhich describe allow symmetricalisolation of primary type I noncovalentperoxide formed interactions in the reaction observed of betweentwoamidrazone bromine two and atoms,bromine cyclopentanone which atoms, allow which isolation(along allow with of isolation primary different of peroxide primaryhydrogen formed peroxide bonds in theandformed reaction other in crystalthe of amidrazonereaction packing of amidrazoneand cyclopentanone and cyclopentanone (along with di (alongerent hydrogenwith different bonds hydrogen and other bondscrystal and packing other e ectscrystal dominating packing effects dominating in this respect).ﬀ ﬀ effectsin this respect).dominating in this respect). 2. Results and Discussion 2. Results Results and and Discussion Discussion Reaction of 4-bromobenzamidrazone 1 with cyclopentanone 2 (1.2 equiv.) in methanol at 60 °C Reaction of 4-bromobenzamidrazone 1 with cyclopentanone 2 (1.2 equiv.) in methanol at 60 C for 96Reaction h in air of results4-bromobenzamidrazone in unpredictable formation1 with cyclopentanone of 1,2,4-triazole 2 (1.2 3 featuringequiv.) in aliphaticmethanol peroxide at 60 ◦°C for 96 96 h h in in air air results results in unpredictable in unpredictable formation formation of 1,2,4-triazole of 1,2,4-triazole3 featuring 3 featuring aliphatic aliphatic peroxide peroxide chain as chain as several pale-yellow crystals, which were studied by single-crystal XRD (Scheme 1a and chainseveral as pale-yellow several pale-yellow crystals, which crystals, were which studied were by single-crystal studied by XRD single-crystal (Scheme1 a XRD and Figure (Scheme2), among 1a and Figure 2), among the formation of 1,4-di(4-bromophenyl)tetrazine as a major product of the reaction Figurethe formation 2), among of 1,4-di(4-bromophenyl)tetrazinethe formation of 1,4-di(4-bromophenyl)tetrazine as a major product as ofa major the reaction product [25 of]. the Reaction reaction of [25]. Reaction of other para-substituted aromatic amidrazones, i.e., 4-RC6H4C(NH2)=NNH2 (R = CF3, [25].other Reactionpara-substituted of other aromaticpara-substituted amidrazones, aromatic i.e., amidrazones, 4-RC6H4C(NH i.e.,2)= 4-RCNNH6H2 4(RC(NH= CF2)=NNH3, H, MeO)2 (R = under CF3, H, MeO) under the same conditions resulted in formation of only the corresponding tetrazines [25], the same conditions resulted in formation of only the corresponding tetrazines [25], whereas generation H, MeO) under the same conditions resulted in formation of only the corresponding+ tetrazines [25], whereas generation of the peroxide substrates was not observed+ even by HRESI -MS. whereasof the peroxide generation substrates of the wasperoxide not observed substrates even was by not HRESI observed-MS. even by HRESI+-MS. HO a HO O O 5mol%a TsOH, O MeOH, in air, N NH2 5mol% TsOH, N NH g O MeOH,60 °C, in96 air h, N NH N NH2 N NH g Ar 60 °C, 96 h OH N NH Ar –H2O Ar O OH NH N Ar 2 –H2O Ar O N 1 2 Ar = 4-BrC6H4 3 Ar NH2 N NH 1 2 Ar = 4-BrC6H4 3 H

b H2O –H2O f b H2O –H2O f H O HO H O HO O N N N NH O2 N N O (from air) N NH O N N N NH O2 N N O Ar Ar (from air) Ar N NH Ar c Ar dAr e Ar NH2 NH2 NH2 N c d e Ar NH2 NH2 NH2 NH H Scheme 1. Reaction scheme of the formation of primary aliphatic peroxide (a) and the plausible Scheme 1. Reaction scheme of the formation of primary aliphatic peroxide (a) and the plausible Scheme 1. Reaction scheme of themechanism formation of ofits primary generation aliphatic (b–g). peroxide (a) and the plausible mechanism of its generation (b–gmechanism). of its generation (b–g).

Figure 2. The single-crystal XRD structure of 3. Probability level of thermal ellipsoids—50%. Figure 2. The single-crystal XRD structure of 3. Probability level of thermal ellipsoids—50%. Figure 2. The single-crystal XRD structure of 3. Probability level of thermal ellipsoids—50%. Plausible mechanism of this reaction includes an acid catalyzed reversible Schiﬀ condensation (b). 1 Plausible mechanism of this reaction includes an acid catalyzed reversible Schiff condensation H NMRPlausible reaction mechanism monitoring of this in CD reaction3OD reveals includes that an the acid reaction catalyzed mixture reversible approached Schiff an condensation equilibrium (b). 1H NMR reaction monitoring in CD3OD reveals that the reaction mixture approached an (molar1 ratio 1:3 1:9) at 60 ◦C for ca. 1 h. The reaction stops at this step in the case of utilization of an (equilibriumb). H NMR (molar reaction≈ ratio monitoring 1:3 ≈ 1:9) at in 60 CD °C3 ODfor ca. reveals 1 h. The that reaction the reaction stops at mixture this step approached in the case anof equilibriumargon atmosphere, (molar but ratio under 1:3 air≈ 1:9) it proceeds at 60 °C further for ca. and 1 h. the The next reaction plausible stops step at includes this step tautomerization in the case of utilization of an argon atmosphere, but under air it proceeds further and the next plausible step (c) and oxidation of the enamine by molecular oxygen giving secondary peroxide (d). Availability of utilizationincludes tautomerization of an argon atmosphere, (c) and oxidation but under of the air enamine it proceeds by molecular further and oxygen the next giving plausible secondary step includeselectron-withdrawing tautomerization peroxo (c) and group oxidation close to of the the imine enamine C atom by providesmolecular intramolecular oxygen giving nucleophilic secondary

Symmetry 2020, 12, x FOR PEER REVIEW 3 of 7 peroxide (d). Availability of electron-withdrawing peroxo group close to the imine C atom provides Symmetry 2020 12 intramolecular, , 637nucleophilic attack by the NH2 moiety giving spiro intermediate (e). The last 3 step of 7 includes heterolytic C–C bond splitting, which accompanied by aromatization of the 1,2,4-triazole cycle and stabilization of the carbanion by the electron-withdrawing peroxo group (f). Proton attack by the NH2 moiety giving spiro intermediate (e). The last step includes heterolytic C–C bond splitting,transfer from which the accompanied N atom to by the aromatization C atom terminates of the 1,2,4-triazole the reaction cycle (g). Further and stabilization experimental of the or carbanioncomputational by the studies electron-withdrawing are needed to confirm peroxo the group suggested (f). Proton mechanism. transfer from the N atom to the C Because precipitation of the peroxo compound 3 has been observed only in the case of atom terminates the reaction (g). Further experimental or computational studies are needed to confirm amidrazone 1 featuring bromine atom in the structure, which (i) has intermediate electronic effects the suggested mechanism. in the row of R’s: CF3, Br, H, MeO, and (ii) cannot sterically affect the reaction proceeding, we Because precipitation of the peroxo compound 3 has been observed only in the case of amidrazone 1suggestedfeaturing that bromine weak atom halogen···halogen in the structure, intermolecular which (i) has interactions intermediate (along electronic with edifferentffects in thehydrogen row of bonds and other crystal packing effects dominating in this respect) provide precipitation of 3 R’s: CF3, Br, H, MeO, and (ii) cannot sterically affect the reaction proceeding, we suggested that weak during the reaction progress and thus stabilization the peroxide 3 in the solid state. Based upon this halogen halogen intermolecular interactions (along with different hydrogen bonds and other crystal observation··· and our interest in unusual noncovalent interactions involving halogen atoms, we packing effects dominating in this respect) provide precipitation of 3 during the reaction progress and studied theoretically the origin of the symmetrical intermolecular Br···Br contacts (type I, Figure 1), thus stabilization the peroxide 3 in the solid state. Based upon this observation and our interest in which were detected in the single-crystal XRD structure of 3. unusual noncovalent interactions involving halogen atoms, we studied theoretically the origin of the Indeed, the intermolecular distance Br···Br in the crystal structure of 3 is 3.414 Å, which is symmetrical intermolecular Br Br contacts (type I, Figure1), which were detected in the single-crystal shorter than the sum of van der··· Waals radii [26] of two bromine atoms (3.66 Å). In order to confirm XRD structure of 3. from a theoretical viewpoint the existence of these intermolecular short contacts Br···Br in the Indeed, the intermolecular distance Br Br in the crystal structure of 3 is 3.414 Å, which is shorter crystal under study, we carried out quantum··· chemical calculations (ωB97XD/x2c-TZVPPall level) than the sum of van der Waals radii [26] of two bromine atoms (3.66 Å). In order to confirm from a and quantum theory of atoms in molecules (QTAIM) analysis [27] for model dimeric associate theoretical viewpoint the existence of these intermolecular short contacts Br Br in the crystal under (Table 1). The visualization of intermolecular noncovalent interactions Br···Br··· in the crystal structure study, we carried out quantum chemical calculations (ωB97XD/x2c-TZVPPall level) and quantum theory of 3 are shown in Figures 3 and 4. of atoms in molecules (QTAIM) analysis [27] for model dimeric associate (Table1). The visualization of intermolecular noncovalent interactions Br Br in the crystal structure of 3 are shown in Figures3 and4. Table 1. Results of quantum theory of atoms··· in molecules (QTAIM) analysis: ρ(r), ∇2ρ(r), λ2, Hb, V(r), and G(r) values (in a.u.) at the bond critical point, corresponding to intermolecular 2 noncovalent Table 1. Results of quantum theory of atoms in molecules (QTAIM) analysis: ρ(r), ρ(r), λ2,Hb, interactions Br···Br in the single-crystal XRD structure of 3 and estimated energy for ∇these contacts V(r), and G(r) values (in a.u.) at the bond critical point, corresponding to intermolecular noncovalent defined by two approaches—Eint (kcal/mol). interactions Br Br in the single-crystal XRD structure of 3 and estimated energy for these contacts ··· defined by twoLaplacian approaches—E of int (kcal/mol). Potential Lagrangian Density of All Energy Electron λ2 Energy Kinetic Eint a Eint b Density of All Laplacian of Electron Energy Potential Energy Lagrangian Kinetic a b Electrons ρ(r) 2 λ2 Density Hb Eint Eint Electrons ρ(r) Density ∇ρ(r)2 Density Hb Density V(r) Energy G(r) Density∇ ρ(r) Density V(r) Energy G(r) 0.010 0.034 0.012 0.001 0.006 0.007 2.2 2.5 0.010 0.034 −0.012− 0.001 − −0.006 0.007 2.2 2.5 a b Eint = 0.58( V(r)) [28]; Eint = 0.57G(r)[28]. a Eint = 0.58(−V(− r)) [28]; b Eint = 0.57G(r) [28].

Figure 3. Visualization of intermolecular noncovalent interactions Br···Br Br Br in the single-crystal XRD ··· structure of of3 3(distribution (distribution of the of theLaplacian Laplacian of electron of electron density density2ρ(r), ∇ bond2ρ(r), paths bond and paths selected and zero-ﬂux selected ∇ surfaces,zero-flux lengthsurfaces, units—Å). length units—Å).

Symmetry 2020, 12, 637 4 of 7 Symmetry 2020, 12, x FOR PEER REVIEW 4 of 7

FigureFigure 4.4. VisualizationVisualization ofof intermolecularintermolecular noncovalentnoncovalent interactionsinteractions BrBr···BrBr inin thethe single-crystalsingle-crystal XRDXRD ··· structurestructure ofof 33 usingusing thethe independentindependent gradientgradient modelmodel analysisanalysis basedbased onon promolecularpromolecular densitydensity (high(high inter qualityquality grid,grid, ~1728000~1728000 pointspoints inin total;total; valuevalue ofof isosurfaceisosurface == 0.01, δδgginter descriptor).descriptor).

The appropriate bond critical point for intermolecular noncovalent interactions Br Br in the The appropriate bond critical point for intermolecular noncovalent interactions Br···Br ··· in the single-crystalsingle-crystal XRD XRD structure structure of of 3 3waswas found found during during the the QTAIM QTAIM analysis. analysis. The The properties properties of electron of electron densitydensity in in this this bond bond critical critical point point are are typical typical for fornoncovalent noncovalent interactions interactions [29,30] [ and,29,30 in] and,particular, in particular, for for similar weak contacts halogen halogen [31–33]. Energy for these contacts (2.2–2.5 kcal/mol) was similar weak contacts halogen···halogen··· [31–33]. Energy for these contacts (2.2–2.5 kcal/mol) was estimatedestimated using using the the procedures procedures developed developed by Tsirelson by Tsirelson et al. for et non-covalent al. for non-covalent contacts involving contacts bromine involving bromineatoms using atoms the equations using the E equationsint = 0.58(−V( Er)) or= E0.58(int = 0.57G(V(r))r), or respectively E = 0.57G( [28].r ),Note respectively that estimated [28]. energy Note that int − int estimatedof these symmetrical energy of theseintermolecular symmetrical Br···Br intermolecular contacts in the Br single-crystalBr contacts XRD in the structure single-crystal of 3 is XRDvery structurewell ··· ofconsistent3 is very with well the consistent approximate with dimerization the approximate energy dimerization of the appropriated energy modelof the appropriateddimeric associate model dimericcalculated associate at the ωB97XD/x2c-TZVPall calculated at the ω levelB97XD (stabilization/x2c-TZVPall amounts level to (stabilization 2.1 kcal/mol). amounts The balance to2.1 between kcal/mol). TheG(r) balance and V(r between) at the G( bondr) and critical V(r ) point at the reveals bond critical that a point covalent reveals contribution that a covalent in the contribution intermolecular in the intermolecularnoncovalent interactions noncovalent Br···Br interactions in the X-ray Br structureBr in theof 3 X-ray is negligible structure [34]. of The3 is sign negligible of λ2 in [ 34appropriate]. The sign of ··· λbondin appropriatecritical point bondfor intermolecular critical point noncovalent for intermolecular interactions noncovalent Br···Br in the interactions X-ray structure Br ofBr 3 in reveals the X-ray 2 ··· structurethat these ofcontacts3 reveals are attractive that these [35,36]. contacts are attractive [35,36].

3.3. Materials and MethodsMethods

3.1.3.1. Synthetic Procedure

AA solution solution of amidrazone of amidrazone1 (214 1 mg, (214 1 mmol), mg, 1 TsOH mmol),H2 O TsOH·H (10 mg,2 0.05O (10 mmol), mg, and 0.05 cyclopentanone mmol), and · 2cyclopentanone(100 mg, 1.2 mmol) 2 (100 in mg, methanol 1.2 mmol) (5 mL) in methanol was kept at(5 60mL)◦C was for 96kept h. at The 60 crystals °C for 96 of h.3 formedThe crystals during of the3 formed reaction during were isolated the reaction from the were reaction isolated solution from and the were reaction subjected solution to single-crystal and were subjected XRD. to single-crystal XRD. 3.2. X-Ray Diffraction Study 3.2. X-RayThe Agilent Diffraction Technologies Study «Xcalibur» diffractometer was used for X-ray diffraction experiment. X-ray diffractionThe Agilent experiment Technologies was collected «Xcalibur» at 100 diffractometer K using monochromated was used for Mo X-rayKαradiation. diffraction The experiment. parameters ofX-ray unit diffraction cell (Table experiment S1) were refined was collected by least square at 100 Ktechniques using monochromated in the 2θ range Mo ofKα 5–55 radiation.◦ for Mo TheKα. Structureparameters was of solvedunit cell using (Table Superflip S1) were [37 refined,38] by by the least charge square flipping techniques method in andthe 2 refinedθ range using of 5–55° the SHELXLfor MoKα [39. Structure] program was implemented solved using in the SuperflipOLEX2 [ 40[37,38]] program by the package. charge Theflipping CrysAlisPro method [ 41and] program refined complexusing the was SHELXL used for empirical [39] program absorption implemented correction using in the spherical OLEX2 harmonics [40] program in SCALE3 package. ABSPACK The scalingCrysAlisPro algorithm. [41] programThe crystallographic complex was data used have for been empirical deposited absorption at Cambridge correction Crystallographic using spherical Data Centreharmonics (CCDC in SCALE3 1969513) ABSPACK and can be scaling obtained algorithm. free of charge The crystallographic via www.ccdc.cam.ac.uk data have/data_request been deposited/cif. Alsoat Cambridge appropriated Crystallographic cif-file with single-crystal Data Centre XRD(CCDC structure 1969513) of 3andis givencan be in obtained Supplementary free of charge Materials. via www.ccdc.cam.ac.uk/data_request/cif. Also appropriated cif-file with single-crystal XRD structure 3.3. Computational Details of 3 is given in Supplementary Materials. The single point DFT calculations based on the experimental X-ray geometry of model dimeric3.3. Computational associate wereDetails carried out using the dispersion-corrected hybrid functional ωB97XD [42] in Gaussian-09 [43] program package. The segmented contracted all-electron relativistic triple-ζ The single point DFT calculations based on the experimental X-ray geometry of model dimeric valence quality basis sets x2c-TZVPPall [44] were used. The quantum theory of atoms in molecules associate were carried out using the dispersion-corrected hybrid functional ωB97XD [42] in (QTAIM) analysis [27] and independent gradient model analysis of noncovalent interactions based on Gaussian-09 [43] program package. The segmented contracted all-electron relativistic triple-ζ valence quality basis sets x2c-TZVPPall [44] were used. The quantum theory of atoms in molecules (QTAIM) analysis [27] and independent gradient model analysis of noncovalent interactions based

Symmetry 2020, 12, 637 5 of 7 promolecular density [45] were performed in Multiwfn program package (v. 3.6) [46]. The Cartesian atomic coordinates for model dimeric associate are presented in Table S2 (Supporting Information).

4. Conclusions In this work, the formation of organic primary peroxide from amidrazone and cyclopentanone was described. The 3-(4-bromophenyl)-5-(4-peroxobutyl)-1,2,4-triazole precipitates as pale-yellow crystals during the reaction and the intermolecular noncovalent interactions Br Br in the crystal ··· structure were determined. Results of quantum chemical calculations indicated that these attractive intermolecular noncovalent interactions Br Br is type I halogen halogen contacts and their estimated ··· ··· energy is 2.2–2.5 kcal/mol. These symmetric weak interactions (along with diﬀerent hydrogen bonds and other crystal packing eﬀects) are suggested to be one of the driving forces for crystallization of the peroxo compound during the reaction and thus its stabilization in the solid state. Further studies of the found reaction are under investigation in our group.

Supplementary Materials: The following Supporting Information is available online at http://www.mdpi.com/ 2073-8994/12/4/637/s1, Table S1: Crystal data for 3, Table S2: Cartesian atomic coordinates for model dimeric associate of 3, cif-file with single-crystal XRD structure of 3. Author Contributions: Conceptualization, D.S.B. and A.S.N.; methodology, D.S.B., M.V.I., V.V.S. and A.S.N.; software, A.S.N.; validation, D.S.B., M.V.I., V.V.S. and A.S.N.; formal analysis, D.S.B., M.V.I., V.V.S. and A.S.N.; investigation, D.S.B., M.V.I., V.V.S. and A.S.N.; resources, D.S.B., M.V.I., V.V.S. and A.S.N.; data curation, D.S.B. and A.S.N.; writing—original draft preparation, D.S.B. and A.S.N.; writing—review and editing, D.S.B., M.V.I., V.V.S. and A.S.N.; visualization, D.S.B. and A.S.N.; supervision, D.S.B. and A.S.N.; project administration, D.S.B. and A.S.N.; funding acquisition, D.S.B. All authors have read and agreed to the published version of the manuscript. Funding: This work was financially supported by Russian Science Foundation (grant 17-73-20004). Acknowledgments: Physicochemical studies were performed at the Center for X-ray Diffraction Studies belonging to Saint Petersburg State University. We thank the Reviewers of this communication for their valuable advices and comments. Conflicts of Interest: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

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