An orthorhombic polymorph of 2-(1,3,5-dithiazinan-5-yl)ethanol or MEA-dithiazine

Substituted triazines are a class of compounds utilized for scavenging and sequestering hydrogen sulfide in oil and gas production operations. The reaction of one of these triazines under field conditions resulted in the formation of the title compound, 2-(1,3,5-dithiazinan-5-yl)ethanol, C5H11NOS2, or MEA-dithiazine. Polymorphic form I, in space group I41/a, was first reported in 2004 and its extended structure displays one-dimensional, helical strands connected through O—H...O hydrogen bonds. We describe here the form II polymorph of the title compound, which crystallizes in the orthorhombic space group Pbca as centrosymmetric dimers through pairwise O—H...N hydrogen bonds from the hydroxyl moiety to the nitrogen atom of an adjacent molecule.

Novel Fluoridoaluminates from Ammonothermal Synthesis: Two Modifications of K2AlF5 and the Elpasolite Rb2KAlF6

Two new modifications of the pentafluoridoaluminate K2AlF5 were obtained from ammonothermal synthesis at 753 K, 224 MPa and 773 K, 220 MPa, respectively. Both crystallize in the orthorhombic space group type Pbcn, with close metric relations and feature kinked chains of cis-vertex-connected AlF6 octahedra resulting in the Niggli formula ∞1{[AlF2/2eF4/1t]2−}. The differences lie in the number of octahedra necessary for repetition within the chains, which for K2AlF5-2 is realized after four and for K2AlF5-3 after eight octahedra. As a result, the orthorhombic unit cell for K2AlF5-3 is doubled in chain prolongation direction [001] as compared to K2AlF5-2 (1971.18(4) pm versus 988.45(3) pm, respectively), while the unit cell parameters within the other two directions are virtually identical. Moreover, the new elpasolite Rb2KAlF6 is reported, crystallizing in the cubic space group Fm3¯m with a = 868.9(1) pm and obtained under ammonothermal conditions at 723 K and 152 MPa.

Crystal structure and Hirshfeld surface analysis of (Z)-4-{[4-(3-methyl-3-phenylcyclobutyl)thiazol-2-yl]amino}-4-oxobut-2-enoic acid

The title cyclobutyl compound, C18H18N2O3S, was synthesized by the interaction of 4-(3-methyl-3-phenylcyclobutyl)thiazol-2-amine and maleic anhydride, and crystallizes in the orthorhombic space group P212121 with Z′ = 1. The molecular geometry is partially stabilized by an intramolecular N—H...O hydrogen bond forming an S 1 1(7) ring motif. The molecule is non-planar with a dihedral angle of 88.29 (11)° between the thiazole and benzene rings. In the crystal, the molecules are linked by O—H...N hydrogen bonds, forming supramolecular ribbons with C 1 1(9) chain motifs. To further analyze the intermolecular interactions, a Hirshfeld surface analysis was performed. The results indicate that the most important contributions to the overall surface are from H...H (43%), C...H (18%), O...H (17%) and N...H (6%), interactions.

Crystal structure of a dicationic PdII dimer containing a 2-[(diisopropylphosphanyl)methyl]quinoline-8-thiolate pincer ligand

A dicationic PdII dimer, bis{2-[(diisopropylphosphanyl)methyl]quinoline-8-thiolato}palladium(II) bis(hexafluoridoantimonate) dichloromethane monosolvate, [Pd2(C32H42N2P2S2)](SbF6)2·CH2Cl2, containing a 2-[(diisopropylphosphanyl)methyl]quinoline-8-thiolate pincer ligand, was isolated and its crystal structure determined. The title compound crystallizes in the orthorhombic space group Pbca. A dimeric structure is formed by bridging coordination of the S atoms. The geometry of the butterfly-shaped Pd2S2 core is bent, with a hinge angle of 108.0 (1)° and a short Pd...Pd distance of 2.8425 (7) Å. These values are the lowest measured compared to ten dicationic dimers with a Pd2S2 core featuring sulfur atoms embedded in a chelating ligand. One of the two hexafluoridoantimonate anions is disordered over two sets of positions with site-occupancy factors of 0.711 (5) and 0.289 (5). The crystal structure is stabilized by many C—H...F and C—H...π interactions, forming a supramolecular network.

Synthesis, Crystal Structures, and Molecular Properties of Three Nitro-Substituted Chalcones

Three functionalized chalcones containing combinations of nitro functional groups have been synthesized via Claisen-Schmidt condensation between 2-nitroacetophenone and nitrobenzaldehyde, and the crystal structures obtained ((E)-1,3-bis(2-nitrophenyl)prop-2-en-1-one, 1a, (E)-1-(2-nitrophenyl)-3-(3-nitrophenyl)prop-2-en-1-one, 1b and (E)-1-(2-nitrophenyl)-3-(4-nitrophenyl)prop-2-en-1-one, 1c), C15H10N2O5, are reported. Compounds 1a and 1c crystallized in the triclinic centrosymmetric space group P1¯, whereas compound 1b crystallized in the orthorhombic space group Pbca. The X-ray analysis reveals that structures 1a and 1b exhibits s-trans conformation, whereas structure 1c exists in s-cis conformation, concerning the olefinic double bonds. In addition, the results show that the position of the nitro substituent attached to the aromatic B-ring has a direct effect on the molecular coplanarity of these compounds. The Hirshfeld surface analysis suggests that the non-covalent π-π stacking interactions are the most important contributors for the crystal packing of 1a and 1b. In 1c, the crystal packing is mainly stabilized by weak intermolecular C―H···O interactions due to the planar nature of the molecule.

Synthesis, characterization, and computational study of copper bipyridine complex [Cu (C18H24N2) (NO3)2] to explore its functional properties

In the present study, copper (II) complex of 4, 4′-di-tert-butyl-2,2′-bipyridine [Cu (C18H24N2) (NO3)2], 1 is investigated through its synthesis and characterization using elemental analysis technique, infra-red spectroscopy, and single-crystal analysis. The compound 1 crystallizes in orthorhombic space group P212121. The copper atom in the mononuclear complex is hexa coordinated through two nitrogen and four oxygen atoms from bipyridine ligand and nitrate ligands. The thermal analysis depicts the stability of the entitled compound up to 170 °C, and the decomposition takes place in different steps between 170 and 1000 °C. Furthermore, quantum chemical techniques are used to study optoelectronic, nonlinear optical, and therapeutic bioactivity. The values of isotropic and anisotropic linear polarizabilities of compound 1 are calculated as 41.65 × 10−24 and 23.02 × 10−24 esu, respectively. Likewise, the static hyperpolarizability is calculated as 47.92 × 10−36 esu using M06 functional compared with para-nitroaniline (p-NA) and found several times larger than p-NA. Furthermore, the antiviral potential of compound 1 is studied using molecular docking technique where intermolecular interactions are checked between the entitled compound and two crucial proteins of SARS-CoV-2 (COVID-19). Our investigation indicated that compound 1 interacts more vigorously to spike protein than main protease (MPro) due to its better binding energy of −9.60 kcal/mol compared with −9.10 kcal/mol of MPro. Our current study anticipated that the above-entitled coordination complexes could be potential candidates for optoelectronic properties and their biological activity.

Chemistry of Spontaneous Alkylation of Methimazole with 1,2-Dichloroethane

Spontaneous S-alkylation of methimazole (1) with 1,2-dichloroethane (DCE) into 1,2-bis[(1-methyl-1H-imidazole-2-yl)thio]ethane (2), that we have described recently, opened the question about its formation pathway(s). Results of the synthetic, NMR spectroscopic, crystallographic and computational studies suggest that, under given conditions, 2 is obtained by direct attack of 1 on the chloroethyl derivative 2-[(chloroethyl)thio]-1-methyl-1H-imidazole (3), rather than through the isolated stable thiiranium ion isomer, i.e., 7-methyl-2H, 3H, 7H-imidazo[2,1-b]thiazol-4-ium chloride (4a, orthorhombic, space group Pnma), or in analogy with similar reactions, through postulated, but unproven intermediatethiiranium ion 5. Furthermore, in the reaction with 1, 4a prefers isomerization to the N-chloroethyl derivative, 1-chloroethyl-2,3-dihydro-3-methyl-1H-imidazole-2-thione (7), rather than alkylation to 2, while 7 further reacts with 1 to form 3-methyl-1-[(1-methyl-imidazole-2-yl)thioethyl]-1H-imidazole-2-thione (8, monoclinic, space group P 21/c). Additionally, during the isomerization of 3, the postulated intermediate thiiranium ion 5 was not detected by chromatographic and spectroscopic methods, nor by trapping with AgBF4. However, trapping resulted in the formation of the silver complex of compound 3, i.e., bis-{2-[(chloroethyl)thio]-1-methyl-1H-imidazole}-silver(I)tetrafluoroborate (6, monoclinic, space group P 21/c), which cyclized upon heating at 80 °C to 7-methyl-2H, 3H, 7H-imidazo[2,1-b]thiazol-4-ium tetrafluoroborate (4b, monoclinic, space group P 21/c). Finally, we observed thermal isomerization of both 2 and 2,3-dihydro-3-methyl-1-[(1-methyl-1H-imidazole-2-yl)thioethyl]-1H-imidazole-2-thione (8), into 1,2-bis(2,3-dihydro-3-methyl-1H-imidazole-2-thione-1-yl)ethane (9), which confirmed their structures.

A previously unknown cyclic alkanolamine and molecular ranking using the pair distribution function

A new six-membered cyclic alkanolamine with chemical formula C6H15N3O3 was synthesized by the reaction of glycolaldehyde with gaseous ammonia. The molecular structure, characterized by a hexagonal ring of alternating carbon and nitrogen atoms with three hydroxymethyl groups attached to the carbon atoms, could not be unambiguously determined by elemental analysis and 1H/13C/15N NMR. The molecular structure and conformation were further determined using a combination of vibrational spectroscopy (IR and Raman) and real-space pair distribution function (PDF) analysis. The crystal structure was determined ab initio from laboratory X-ray powder diffraction (XRPD) with orthorhombic space group Ama2 (No. 40) and unit-cell parameters a = 12.1054 (2) Å, b = 13.5537 (2) Å and c = 5.20741 (8) Å. Consistent structure models could be obtained by symmetry-independent PDF and PDF-Rietveld co-refinements. Independent local structure refinements indicate that the most likely deviations from the average structure consist of small tilting and translational distortions of hydrogen-bonded molecular stacks. Thermal analysis (TG/DTA) and temperature-dependent XRPD measurements were also performed to determine the thermal behavior.

The structures of 1:1 and 1:2 adducts of phosphanetricarbonitrile with 1,4-diazabicyclo[2.2.2]octane

In the structures of 1:1 and 1:2 adducts of phosphanetricarbonitrile (C3N3P) with 1,4-diazabicyclo[2.2.2]octane (C6H12N2), the 1:1 adduct crystallizes in the orthorhombic space group, Pbcm, with four formula units in the unit cell (Z′ = 0.5). The P(CN)3 unit lies on a crystallographic mirror plane while the C6H12N2 unit lies on a crystallographic twofold axis passing through one of the C—C bonds. The P(CN)3 moiety has close to C 3v symmetry and is stabilized by forming adducts with two symmetry-related C6H12N2 units. The phosphorus atom is in a five-coordinate environment. As a result of the symmetry, the two trans angles are equal so τ5 = 0.00 and thus the geometrical description could be considered to be square pyramidal. However, the electronic geometry is distorted octahedral with the lone pair on the phosphorous occupying the sixth position. As would be expected from VSEPR considerations, the repulsion of the lone-pair electrons with the equatorial bonding electrons means that the trans angles for the latter are considerably reduced from 180° to 162.01 (4)°, so the best description of the overall geometry for phosphorus is distorted square pyramidal. The 1:2 adduct crystallizes in the monoclinic space group, P21/m with two formula units in the asymmetric unit (i.e. Z' = 1/2). The P(CN)3 moiety lies on a mirror plane and one of the two C6H12N2 (dabco) molecules also lies on a mirror plane. The symmetry of the P(CN)3 unit is close to C 3v. There are three P...N interactions and consequently the molecular geometry of the phosphorus atom is distorted octahedral. This must mean that the lone pair of electrons on the phosphorus atom is not sterically active. For the 1:1 adduct, there are weak associations between the phosphorus atom and one of the terminal nitrogen atoms from the C[triple-bond] N moiety, forming chains in the a-axis direction. In addition there are weak C—H...N interactions between a terminal nitrogen atoms from the C[triple-bond]N moiety and the C6H12N2 molecules, which form sheets perpendicular to the a axis.

Formazans: a Structural and Spectroscopic Study of 3-Substituted-1,5-Diphenylformazans

<p>A series of thirteen isomeric 1,5-diphenylformazans have been structurally characterised both in the solid state and in solution by the combined techniques of x-ray crystallography, nuclear magnetic resonance, Raman, mass and absorption spectroscopies. 1,5-Diphenylformazan is known to exist in the anti, s-trans configuration in the solid state and this is shown to be the solution dominant species. In aprotic solvents an equilibrium involving the anti, s-trans and syn, s-cis configurations is evidenced. 3-Methyl-1,5-diphenylformazan has been characterised by an x-ray crystal analysis. C14H14N4 belongs to the monoclinic space group P2/c, a = 8.133(1), b = 19.085(4), c = 9.364(2) A, beta = 105.93 degrees,U = 1397.6(5) A3, Z = 4. The anti, s-trans configuration of the solid state is also preferred in solution where it is in equilibrium with the syn, s-cis configuration. 3-Ethyl-1,5-diphenylformazan exists in two isomers in the solid state, both of which have been characterised by an x-ray crystal analysis. The red isomer of 3-ethyl-1,5-diphenylformazan belongs to the orthorhombic space group P2l2l2l and adopts the syn, s-trans configuration in the solid state. The orange, light stable isomer of 3-ethyl-1,5-diphenylformazan belongs to the monoclinic space group P2l/c and adopts the anti, s-trans configuration in the solid state. The rate of return of the photo-activated orange isomer to the dark-stable red isomer follows first order kinetics dependent upon the total concentration of the formazan and the water content of the solvent. 3-Tertiary-butyl-1,5-diphenylformazan has been characterised by an x-ray crystal analysis. C17H20N4, belongs to the monoclinic space group P2/c, a = 11.235(3), b = 20.117(5), c = 14.176(3) A, beta = 92.14(2) degrees, U = 3202(1) A3, Z = 8. The syn, s-cis configuration of the solid state is maintained in solution. 1,3,5-Triphenylformazan is shown to exist in two red forms in the solid state. The syn, s-cis and syn, s-trans isomers are both present in the crystalline sample. These isomers are also evident in solution with the syn, s-trans configuration becoming more dominant in aprotic solvents. 1,5-Diphenylformazan reacts with bromine in solution in a single reaction to give di(3-bromo-1,5-diphenyltetrazolium)-decabromide and 3-bromo-1,5-di-para-phenylformazan, both of which have been characterised by an x-ray crystal analysis. C13H10.6N4Br5.3 belongs to the triclinic space group Pl, a = 8.572(1), b = 9.711(1), c = 14.166(3) A, alpha = 75.18(1), beta = 89.84(1), gamma = 70.42(1) degrees, Z = 2. Stacks of anti-parallel pairs of 3-bromo-1,5-diphenyltetrazolium cations are interleaved by pairs of Br102- anions. The polybromide represents a new type of polyhalogen network for bromine, Br102-, the Raman spectrum of which has been recorded for the first time. C13H9N4Br3 belong to the orthorhombic space group Pnma, a = 7.343(2), b = 32.793(12), c = 5.912(1) A, Z = 4. The formazan adopts the anti, s-trans configuration in the solid state. 3-Chloro-1,5-diphenylformazan has been characterised by an x-ray crystal analysis. Preliminary results indicate that the formazan adopts the anti, s-trans configuration in the solid state. 3-Mercapto-1,5-diphenylformazan is shown to exist in the anti, s-trans configuration in CDCl3, solution. 3-Methylthio-1,5-diphenylformazan is shown to exist in an equilibrium mixture of syn, s-trans and anti, s-trans configurations in solution. The ratio of the two isomers is approximately equal. 3-Ethylthio-1,5-diphenylformazan exists in two isomers in the solid state, one of which has been characterised by an x-ray crystal analysis. Preliminary results indicate that the orange isomer of 3-ethylthio-1,5-diphenylformazan. C15H16N4S belongs to the monoclinic space group P2l/a, a = 11.027(6). b = 8.627(7), c = 15.487(8) A, b = 93.70(5) degrees, U = 1470 A3, Z = 4, and exists in the anti, s-trans configuration on the solid state. The orange and red isomers are both present in an equilibrium mixture in solution. The red isomer is shown to exist in the syn, s-trans configuration in the solid. 3-isopropylthio-1,5-diphenylformazan is shown to exist in an equilibrium mixture of anti, s-trans and syn, s-trans configurations in solution. 1-Methyl-1,5-diphenylformazan has been characterised by an x-ray crystal analysis. C14H14N4 belongs to the monoclinic space group 12/1, a = 28.402(7), b = 5.640(1), c = 15.688(4) A, beta = 97.34 degrees, U = 2493(1) A3, Z = 8. The formazan adopts the anti, s-trans configuration in the solid state. The formazan retains its configurational integrity in both protic and aprotic solutions. The excitation profile of the Raman active phonons based upon coupled vibrations of the formazan backbone indicate a maximum corresponding to the absorption spectra in both the solid state and in solution. Preliminary results of a kinetic investigation of some primary metal dithizonates indicate that the thermal-path return is strictly first order. The mechanism would appear to be essentially similar to that operating in 3-ethyl-1,5-diphenylformazan. The mass spectra of the series of formazan follow similar splitting schemes irrespective of the solid-state configuration.</p>