Currently, ammonium hexafluorosilicates are being actively studied as new anti-caries agents, which, according to the results of researches on rats, show a more significant caries-preventive effectiveness compared to sodium fluoride with a simultaneous significant improvement of the biochemical indicators of the dental pulp and the absence of hepatotoxic effects. Previously, we’ve synthesized 2-, 3-, 4-aminophenylacetic acid hexafluorosilicates (2-, 3-, 4-APhHFS); in an attempt to recrystallize the 2-APhHFS salt from ethanol, a red crystalline product was obtained. The purpose of the research – considering the potential prospects of 2-, 3-, 4-APhHFS, it is expedient to establish the composition and structure of the recrystallization product of 2-APhHFS. Mass spectra were recorded on MX-1321 and VG 7070 spectrometers (VG Analytical), X-ray structural analysis was carried out on an Xcalibur E diffractometer. As follows from the comparison of the external inspection of the original 2-APhHFS and its recrystallization product (RP) samples, they differ significantly: light brown amorphous 2-APhHFS and red crystalline RP. The characteristics of the mass spectra of 2-APhHFS and RP are also different. The structure of RP as 2-oxindole was objectively established by X-ray diffraction data. The recrystallization process of 2-APhHFS to obtain 2-oxindole does not require heating of the reaction mixture, i.e., it is carried out under extremely mild conditions. It is possible that it's connected with the participation of the protonated form of 2-aminophenylacetic acid in the composition of 2-APhHFS in chemical transformations. Thus, caution should be exercised in experiments with both solutions and, apparently, solid samples of 2-APhHFS during salt purification procedures or other manipulations. The high lability of 2-aminophenylacetic acid hexafluorosilicate limits the possibilities of using standard purification methods (sublimation, recrystallization) for this compound.

Гексафторосиликат состава (LH)2SiF6 (I), (L = 4-гидроксиметилпиридин) выделен в качестве продукта взаимодействия метанольного раствора L и 45%-й кремнефтороводородной кислоты (L:H2SiF6 = 1:3). В кристаллической структуре I катионы и анионы объединены Н-связями NH⋯F (N⋯F 2.809(2), 2.824(2) Å) и OH⋯F (O⋯F 2.7036(18) Å), геометрия аниона SiF62– — искаженный октаэдр (расстояния Si—F 1.6780(11)—1.6877(11) Å. В ИК спектре I идентифицированы полосы поглощения основных колебаний, определены растворимость I в воде и ряде органических растворителей, а также степень гидролиза соли в 1⋅10–4 М водном растворе.

Попытка сокристаллизации N7,N16-бис(S-1-фенилэтил)-1,4,10,13-тетраокса-7,16-диазациклооктадекан-7,16-дикарбоксамида (1) с гидрохлоридами метиловых эфиров (ГХМЭ) L- и D-валина, а также L- и D-лейцина приводит к раздельной кристаллизации диазакраун-эфира 1 (или его моногидрата 1.H2O) и ГХМЭ соответствующих α-аминокислот. Ранее неописанные кристаллические структуры соединений 1, 1.H2O и ГХМЭ D-лейцина (2) определены методом монокристальной дифрактометрии.

Reaction of potassium thiocyanate with 2-[2-oxo-1-(1-tosyloxyimino)-2-phenylethyl]pyrimidin-4-(3H)-one derivatives led to the formation of a new fused heterocyclic system with a common nitrogen atom, substituted 7H-[1,2,5]thiadiazolo[2,3-a]pyrimidin-7-one.

We report here the synthesis and our studies of the structure, physicochemical properties, and anticaries activity of a novel potential anticaries substance 2-amino-4,6-dihydroxypyrimidinium hexafluorosilicate. IR spectra, EI mass spectra, and 19F NMR spectra were obtained and their properties were studied. Biological investigations were performed on animals kept on the Stephan caries-inducing diet (50% sucrose). Alkaline phosphatase (AlkP) and acid phosphatatase (AcP) were assayed in pulp homogenates and the AlkP:AcP ratio was used to assess the mineralization index (MI). AlkP activity was measured in serum, along with alanine aminotransferase (ALT). The number and depth of caries lesions to the teeth were assessed and caries prophylactic efficacy (CPE) was computed. The data showed that 2-amino-4,6-dihydroxypyrimidinium hexafluorosilicate decreased the number of caries lesions by 45.5% and had high anticaries efficacy, five times greater than that of sodium fluoride.

Реакция роданида калия с производными 2-[2-оксо-1-(1-тозилоксиимино)-2-фенилэтил]пиримидин- 4(3Н)-она приводит к образованию новой конденсированной гетероциклической системы с общим атомом азота - замещённого 7Н-[1,2,5]тиадиазоло[2,3-а]пиримидин-7-она.

Hexafluorosilicate (LH 2 )SiF 6 and the cis -[SiF 4 (L)] chelate complex characterized by 19 F NMR are products of reaction between hydrofluorosilicic acid and 1,10-phenanthroline (L). XRD findings show that the structure of (LH 2 )SiF 6 is stabilized by NH···F hydrogen bonds (N···F 2.618(4), 2.676(4) Å) and CH···F contacts. The relative resistance of the cis -[SiF 4 (L)] complex to hydrolysis is associated with the chelate effect.

Выполнено рентгеноструктурное исследование двух изоструктурных комплексов диоксония [H5O2]+ с тетрабензо-30-краун-10 (ТБ30К10) состава [(ТБ30К10 · H5O2)][TaF6] (I) и [(ТБ30К10 · H5O2)][NbF6] (II). Комплексы принадлежат к моноклинной сингонии, пр. гр. C2/c, Z = 4. Для комплекса I: a=15.6583(12), b=15.2259(13), c=16.4473(13) A, =99.398(6)°; для комплекса II: a=15.7117(12), b=15.2785(15), c=16.5247(15) A, =99.398(7)°. Комплексы относятся к ионному типу. Катион диоксония [H5O2]+ в виде двухзвенного кластера [H3O · H2O]+, стабилизирован сильной водородной связью ОН···О [О···О 2.353(4) A] и капсулирован краун-эфиром. Каждый из его атомов кислорода образует также по две водородные связи О···О(краун). Краун-эфир принимает необычную двухъярусную (карманообразную) конформацию, обеспечивающую полное капсулирование оксониевого ассоциата. Взаимодействие комплексного катиона с анионом осуществляется в кристалле посредством контактов типа С–Н···F.

The structure of the complex ( o -CH 3 C 6 H 4 NH 3 ) 2 SiF 6 was determined by X-ray diffraction. In the ionic structure of the complex, the SiF 6 2− anions (Si-F, 1.595(9)-1.683(17)Å) and the o -CH 3 C 6 H 4 NH 3 + cations are combined by NH⋯F hydrogen bonds (N⋯F 2.757(10)-3.25(2) Å). The components of the structure are combined into a layer whose central part is formed by the SiF 6 2− anions and the outer hydrophobic surfaces are formed by the aromatic rings of the cations.

The results of computer-assisted molecular modeling showed that 2,6,8,12-tetraoxa-4,10(1,4)-dibenzena-1,7(2,7)-difluorenacyclododecaphane-19,79-dione is promising as a receptor for polar organic molecules. This compound was synthesized by the reaction of 1,4-bis(bromomethyl)benzene with 2,7-dihydroxyfluoren-9-one in DMF in the presence of anhydrous potassium carbonate under strong dilution. Crystalline complexes of the title compound with DMF and nitrobenzene were isolated and studied by X-ray diffraction. In both complexes the substrate is located in the ligand cavity.

The results of computer-assisted molecular modeling showed that 2,6,8,12-tetraoxa-4,10(1,4)-dibenzena-1,7(2,7)-difluorenacyclododecaphane-1 9 ,7 9 -dione is promising as a receptor for polar organic molecules. This compound was synthesized by the reaction of 1,4-bis(bromomethyl)benzene with 2,7-dihydroxyfluoren-9-one in DMF in the presence of anhydrous potassium carbonate under strong dilution. Crystalline complexes of the title compound with DMF and nitrobenzene were isolated and studied by X-ray diffraction. In both complexes the substrate is located in the ligand cavity.

A statistical Monte Carlo computer simulation has shown that the use of a diphenylglycoluril fragment as a rigid linker should give bis(crown ethers) with identically oriented benzocrown rings located closely in space. The syntheses of the first representative of this series, bis[(benzo-18-crown-6)-4,5-ylmethyl]-1,3,4,6-diphenylglycoluril and its complex with sodium picrate have been described. The crystal structure of the complex has been determined by X-ray diffraction: space group \(P\bar 1\), a = 13.976(3) Å, b = 16.723(3) Å, c = 20.578(4) Å, α = 98.74(2)°, β = 106.19(3)°, γ = 114.07(3)°. The complex represents a new type of coordination polymer formed by a combination of coordination and hydrogen bonds and stacking, which are favored by the U-shaped conformation of diphenylglycoluril.

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The products of the reaction of 1,2,5-thiadiazolo[3,4-d]pyrimidine-5,7-dione 2-oxide with water, viz. 1,2,5-thiadiazolo[3,4-d]pyrimidine-5,7-dione 2-oxide dihydrate and 6-amino2,4-dioxo-1,2,3,4-tetrahydropyrimidine-5-sulfamic acid, were isolated and characterized by X-ray diffraction.

The results of systematic studies into the structures of products formed in reactions between fluorosilicic acid (FSA) and organic bases are presented. Different hydrolytically labile silicon fluoride complexes contained in these products are stabilized. A debatable problem of FSA state in aqueous solutions is discussed in the light of the data obtained.