Alexander S. Lyakhov

1,5-Diamino-1H-1,2,3,4-tetrazolium picrate: X-ray molecular and crystal structures and ab initio MO calculations

The crystal and molecular structures of 1,5-diamino-1H-1,2,3,4-tetrazolium picrate (DATP) were determined by X-ray diffraction analysis. The tetrazolium cation in DATP has a structure with protonated N4 atom of the ring. Two amino groups in the cation are found to be rather different. The 5-amino group lies in the plane of the tetrazole ring and valence angles around the N atom are close to 1208, which indicates sp 2 hybridization of atomic orbital of the nitrogen atom. In contrast, valence angles around the N atom of the 1-amino group are close to tetrahedral angle, which suggests sp 3 hybridization. The exocyclic C– N bond in the cation is substantially shorter than that in 1,5-diaminotetrazole. The obtained results indicate a conjugation between the p-system of the tetrazole ring and the 5-amino group. The results of ab initio calculations of electronic structure and relative stability for various tautomeric forms of protonated 1,5-diaminotetrazole using MP2/6-31G* and B3LYP/6-31G* levels of theory are in a good agreement with X-ray data and show that there are differences in s-electron overlap populations for the C– N bonds in the cation in DATP, while p-electrons are delocalized. q 2003 Elsevier Science B.V. All rights reserved.

Synthesis, characterization, and biological evaluation of new tetrazole-based platinum(II) and palladium(II) chlorido complexes--potent cisplatin analogues and their trans isomers.

Two series of tetrazole-containing platinum(II) and palladium(II) chlorido complexes, trans-[ML(2)Cl(2)] (M=Pt, Pd) and cis-[PtL(2)Cl(2)]·nH(2)O (n=0, 1), where L is 1- or 2-substituted 5-aminotetrazole, have been synthesized and thoroughly characterized. Configuration of platinum(II) complexes obtained from the reaction of 5-aminotetrazoles with K(2)PtCl(4) has been found to vary depending on the nature of tetrazole derivatives and reaction conditions. According to in vitro cytotoxic evaluation, only platinum complexes display noticeable antiproliferative effect, and their cytotoxicity depends strongly on their geometry and hydrophobicity of the carrier ligands. The most promising complexes are cis-[Pt(1-apt)(2)Cl(2)]·H(2)O and cis-[Pt(2-abt)(2)Cl(2)]·H(2)O, where 1-apt is 5-amino-1-phenyltetrazole and 2-abt is 5-amino-2-tert-butyltetrazole. In comparison with cisplatin, they show comparable cytotoxic potency against cisplatin-sensitive human cancer cell lines, cis-[Pt(2-abt)(2)Cl(2)]·H(2)O performing substantially higher activity against cisplatin-resistant cell lines. Cell cycle studies in H1299 cell line indicated that cis-[Pt(2-abt)(2)Cl(2)]·H(2)O induced apoptosis launched from G2 accumulations. The DNA interaction with cis-[Pt(1-apt)(2)Cl(2)]·H(2)O was followed by UV spectroscopy, circular dichroism, hydrodynamic and electrophoretic mobility studies. Both cis-[Pt(1-apt)(2)Cl(2)]·H(2)O and cis-[Pt(2-abt)(2)Cl(2)]·H(2)O complexes appeared to be significantly less toxic than cisplatin in mice, while only compound cis-[Pt(1-apt)(2)Cl(2)]·H(2)O displayed noticeable efficacy in vivo.

Thermal behaviour of ammonium polyphosphate-inorganic compound mixtures. Part 2. Manganese dioxide

The chemical interaction between ammonium polyphosphate (APP) and managanese dioxide (MnO2) was studied by thermogravimetry with linear heating. The products of interaction were collected at successive steps of weight loss and analysed by X-ray diffraction (on crystalline products) or by chemical analysis (on amorphous products). It was found that MnO2 starts to interact with APP at the beginning of the thermal decomposition of APP at 270–280°C. At the onset of weight loss of the APPMnO2 mixtures, manganese(VI) is reduced to manganese(III) and (II) producing MnNH4P2O7 and Mn(NH4)2(PO3)4 respectively. Ammonia, which is partially reduced to nitrogen, is evolved from PP. The formation of MnNH4P3O9 and then Mn2P4O12 is observed on further heating of the mixtures to 560–570°C. The content and ratio of the products of reaction depend on the temperature and the ratio of components in the initial APPMnO2 mixtures. Assignment of the X-ray powder diffraction peaks and an estimation of the lattice parameters have been made on orthorhombic MnNH4P3O9 (a = 7.357(3), b = 12.186(8), c = 9.390(5)A, space group Pmcn).

Two derivatives of 5-aminotetrazole: 5-amino-1-phenyltetrazole and 5-amino-1-(1-naphthyl)tetrazole

In the molecules of 5-amino-1-phenyltetrazole, C(7)H(7)N(5), (I), and 5-amino-1-(1-naphthyl)tetrazole, C(11)H(9)N(5), (II), the tetrazole rings and aryl fragments are not coplanar; corresponding dihedral angles are 50.58 (5) and 45.19 (7) degrees for the two independent molecules of (I), and 64.14 (5) degrees for (II). Intermolecular N-H.N hydrogen bonds between the amino groups and tetrazole N atoms are primarily responsible for formation of two-dimensional networks extending parallel to the bc plane in both compounds. The presence of the amino group has a distinct effect on the geometry of the tetrazole rings in each case.

Two isostructural manganese (III) diphosphates, acid α-MnHP2O7 and double MnLiP2O7: crystal structure determination from X-ray powder diffraction data

Summary Ab initio crystal structure determination of the α form of MnHP2O7 and Rietveld refinement of the MnLiP2O7 structure were performed using powder X-ray diffraction data. The final structures have been obtained using soft restraints on interatomic bond lengths and bond angles for the diphosphate group. The two compounds were found to be to a great extent isostructural. They crystallize in the monoclinic space group P21, Z = 2, a = 6.7547(6), b = 8.3160(7), c = 4.8769(5) Å, β = 113.1791(18)°, Rp = 0.0283, Rwp = 0.0390, RBragg = 0.0930, RF = 0.0869 for α-MnHP 22O7, and a = 7.0018(5), b = 8.1616(6), c = 4.7267(4)Å, β = 109.404(3)°, Rp = 0.0307, Rwp = 0.0423, RBragg = 0.0960, RF = 0.0861 for MnLiP2O7. In both compounds, diphosphate groups adopt nearly eclipsed configuration. Their structures present three-dimensional networks, which have tunnels including the lithium cations or hydrogen atoms. The behaviour of the crystalline forms of MnHP2O7 in H/Li exchange reactions is discussed, vs. their structural aspects.

Selective synthesis of binuclear N-substituted tetrazoles and tetrazolium salts

The selective alkylation of mononuclear tetrazoles by 2,5-dimethyl-2,5-hexanediol and of N-unsubstituted binuclear tetrazoles by tert-butyl alcohol was realized in perchloric and sulfuric acids. A series of previously unknown N-substituted binuclear tetrazoles and tetrazolium salts were synthesized. Data from X-ray crystallographic analysis of 2,5-dimethyl-2,5-di(5-phenyl-2-tetrazolyl)hexane are presented.

Two succinic acid derivatives of 2-ethyl-6-methylpyridin-3-ol.

Crystals of bis(2-ethyl-3-hydroxy-6-methylpyridinium) succinate-succinic acid (1/1), C(8)H(12)NO(+)·0.5C(4)H(4)O(4)(2-)·0.5C(4)H(6)O(4), (I), and 2-ethyl-3-hydroxy-6-methylpyridinium hydrogen succinate, C(8)H(12)NO(+)·C(4)H(5)O(4)(-), (II), were obtained by reaction of 2-ethyl-6-methylpyridin-3-ol with succinic acid. The succinate anion and succinic acid molecule in (I) are located about centres of inversion. Intermolecular O-H···O, N-H···O and C-H···O hydrogen bonds are responsible for the formation of a three-dimensional network in the crystal structure of (I) and a two-dimensional network in the crystal structure of (II). Both structures are additionally stabilized by π-π interactions between symmetry-related pyridine rings, forming a rod-like cationic arrangement for (I) and cationic dimers for (II).

Stereoselective synthesis of 9α-hydroxylated ecdysteroids.

Treatment of ecdysteroids with excess of TBAF in THF was shown to proceed with stereoselective oxidation at the 9alpha position of the carbon skeleton. The stereochemistry of the products was confirmed by X-ray analysis. Using this method, 9alpha-hydroxyecdysteroids were obtained in good yield. The results open a route to novel type of natural and modified steroids that are difficult to access otherwise.

catena-Poly­[[bis­[μ-1,2-bis(1-methyl­tetrazol-5-yl)­ethane-κ2N4:N4′]bis[chloro­copper(II)]]-di-μ-chloro]

In the title compound, [Cu 2 Cl 4 (C 6 H 10 N 8 ) 2 ] n , the ligand has C 2 symmetry, and the Cu and Cl atoms lie on a mirror plane. The coordination polyhedron of the Cu atom is a distorted square pyramid, with the basal positions occupied by two N atoms from two different ligands [Cu-N = 2.0407 (18) A] and by the two Cl atoms [Cu-Cl = 2.2705 (8) and 2.2499 (9) A], and the apical position occupied by a Cl atom [Cu-Cl=2.8154(9) A] that belongs to the basal plane of a neighbouring Cu atom. The [CuCl 2 (C 6 H 10 N 8 )] 2 units form infinite chains extending along the a axis via the Cl atoms. Intermolecular C-H...Cl contacts [C...Cl = 3.484 (2) A] are also present in the chains. The chains are linked together by intermolecular C-H...N interactions [C...N = 3.314 (3) A].

Synthesis and structure of 1-tert-butyl-3-R-tetrazolium salts

An effective method was developed for the synthesis of 1,3-disubstituted tetrazolium salts by the quaternization of 2-monosubstituted tetrazoles, including functionally substituted compounds, with tert-butanol in 72% perchloric acid. An X-ray diffraction investigation of examples of this series of salts - 1-tert-butyl-3-(1-methylvinyl)- and 1,3-di-tert-butyltetrazolium perchlorates - was carried out.