3,4‐Di‐2‐pyridyl‐1,2,5‐oxadiazole and its perchlorate salt

In 3,4‐di‐2‐pyridyl‐1,2,5‐oxadiazole (dpo), C₁₂H₈N₄O, each mol­ecule resides on a twofold axis and inter­acts with eight neighbours via four C—H⋯N and four C—H⋯O inter­actions to generate a three‐dimensional hydrogen‐bonded architecture. In the perchlorate analogue, 2‐[3‐(2‐pyrid­yl)‐1,2,5‐oxadiazol‐4‐yl]pyridinium perchlorate, C₁₂H₉N₄O⁺·ClO₄⁻ or [Hdpo]ClO₄, the [Hdpo]⁺ cation is bisected by a crystallographic mirror plane, and the additional H atom in the cation is shared by the two pyridyl N atoms to form a symmetrical intra­molecular N⋯H⋯N hydrogen bond. The cations and perchlorate anions are linked through C—H⋯O hydrogen bonds and π–π stacking inter­actions to form one‐dimensional tubes along the b‐axis direction.     

2‐(4‐Hydroxy­phenyl)‐4,4‐dimethyl‐2‐oxazoline: X‐ray and density functional theory study

In the crystal structure of the title compound, C₁₁H₁₃NO₂, there are strong inter­molecular O—H⋯N hydrogen bonds which, together with weak intra­molecular C—H⋯O hydrogen bonds, lead to the formation of infinite chains of mol­ecules, held together by weak inter­molecular C—H⋯O hydrogen bonds. A theoretical investigation of the hydrogen bonding, based on density functional theory (DFT) employing periodic boundary conditions, is in agreement with the experimental data. The cluster approach shows that the influence of the crystal field and of hydrogen‐bond formation are responsible for the deformation of the 2‐oxazoline ring, which is not planar and adopts a ⁴T₃ (^C3T_C2) conformation.     

(R)‐N‐[(R)‐1‐(2‐Hydroxy‐5‐methyl­phenyl)‐2‐phenyl­ethyl]‐2‐methyl‐1‐phenyl­propyl­ammonium chloride

In the title compound, C₂₅H₃₀NO⁺·Cl⁻, the mol­ecules are linked by a combination of inter­molecular N—H⋯Cl and O—H⋯Cl hydrogen bonds and intra­molecular N—H⋯O hydrogen bonds. The absolute configuration of the new stereogenic centre (the C atom adjacent to the N atom on the phenol side) is determined to have an R configuration.     

1‐((E)‐{(1R,2R)‐2‐[(E)‐(2‐Hydr­oxy‐1‐naphth­yl)methyl­eneamino]cyclo­hexyl}iminiometh­yl)naphthalen‐2‐olate: a Schiff base compound having both OH and NH character

The title Schiff base compound, C₂₈H₂₆N₂O₂, possesses both OH and NH tautomeric character in its mol­ecular structure. While the OH side of the compound is described as an inter­mediate state, its NH side adopts a predominantly zwitterionic form. The mol­ecular structure of the compound is stabilized by both N⁺—H⋯O⁻ and O—H⋯N intra­molecular hydrogen bonds. There are two weak C—H⋯O hydrogen bonds leading to polymeric chains of topology C(5) and C(13) running along the b axis of the unit cell. In addition, inter­molecular C—H⋯π inter­actions serve to stabilize the extended structure.     

2′‐De­oxy‐2‐fluoro­tubercidin

In the title compound [systematic name: 7‐(2‐de­oxy‐β‐d ‐erythro‐pentofuranos­yl)‐2‐fluoro‐7H‐pyrrolo[2,3‐d]pyrimidin‐2‐amine], C₁₁H₁₃FN₄O₃, the conformation of the N‐glycosylic bond is between anti and high‐anti [χ = −110.2 (3)°]. The 2′‐deoxy­ribofuranosyl unit adopts the N‐type sugar pucker (₄T³), with P = 40.3° and τ_m = 39.2°. The orientation of the exocyclic C4′—C5′ bond is −ap (trans), with a torsion angle γ = −168.39 (18)°. The nucleobases are arranged head‐to‐head. The crystal structure is stabilized by four inter­molecular hydrogen bonds of types N—H⋯N, N—H⋯O and O—H⋯O.     

4,4′‐Butane‐1,4‐diylbis[3‐ethyl‐1H‐1,2,4‐triazol‐5(4H)‐one] and 4‐hydr­oxy‐3‐n‐prop­yl‐1H‐1,2,4‐triazol‐5(4H)‐one

The title compounds, C₁₂H₂₀N₆O₂, (I), and C₅H₉N₃O₂, (II), display the characteristic features of 1,2,4‐triazole derivatives. Compound (I) lies about an inversion centre which is at the mid‐point of the central C—C bond. Compound (II) also contains a planar 1,2,4‐triazole ring but differs from (I) in that it has a hydr­oxy group attached to the ring. Mol­ecules of (I) are held together in the crystal structure by inter­molecular N—H⋯O contacts and by weak π–π stacking inter­actions between the 1,2,4‐triazole moieties. Compound (II) contains inter­molecular O—H⋯O and N—H⋯O hydrogen bonds.     

(2‐Hydroxy­ethyl)­hydrazinium(2+) dichloride

The crystal structure of the title compound, C₂H₁₀N₂O²⁺·2Cl⁻, is built up from one 2‐hydroxy­ethyl­hydrazinium(2+) cation and two Cl⁻ anions. The mol­ecular structure is stabilized by O—H⋯Cl and N—H⋯Cl hydrogen bonds. The crystal structure is stabilized by one N—H⋯O and three N—H⋯Cl inter­actions, and the three‐dimensional network of hydrogen bonds stabilizes the crystal packing. All five hydrazinium H atoms are involved in hydrogen bonds to Cl⁻ anions. The Cl⋯H contact distances range from 2.122 (15) to 2.809 (14) Å.     

Supramolecular structures of three isomeric 4‐(methyl­phenylamino)­pyridine‐3‐sulfonamides

The structures of the three title isomers, namely 4‐(2‐methyl­anilino)pyridine‐3‐sulfonamide, (I), 4‐(3‐methyl­anilino)pyridine‐3‐sulfonamide, (II), and 4‐(4‐methyl­anilino)pyridine‐3‐sulfonamide, (III), all C₁₂H₁₃N₃O₂S, differ in their hydrogen‐bonding arrangements. In all three mol­ecules, the conformation of the 4‐amino­pyridine‐3‐sulfon­amide moiety is conserved by an intra­molecular N—H⋯O hydrogen bond and a C—H⋯O inter­action. In the supra­mol­ecular structures of all three isomers, similar C(6) chains are formed via inter­molecular N—H⋯N hydrogen bonds. N—H⋯O hydrogen bonds lead to C(4) chains in (I), and to R₂²(8) centrosymmetric dimers in (II) and (III). In each isomer, the overall effect of all hydrogen bonds is to form layer structures.     

Three isomeric forms of hydroxyphenyl‐2‐oxazoline: 2‐(2‐hydroxyphenyl)‐2‐oxazoline, 2‐(3‐hydroxyphenyl)‐2‐oxazoline and 2‐(4‐hydroxyphenyl)‐2‐oxazoline

Crystal structures are reported for three isomeric compounds, namely 2‐(2‐hydroxy­phenyl)‐2‐oxazoline, (I), 2‐(3‐hydroxy­phenyl)‐2‐oxazoline, (II), and 2‐(4‐hydroxy­phenyl)‐2‐oxazoline, (III), all C₉H₉NO₂ [systematic names: 2‐(4,5‐dihydro‐1,3‐oxazol‐2‐yl)phenol, (I), 3‐(4,5‐dihydro‐1,3‐oxazol‐2‐yl)phenol, (II), and 4‐(4,5‐dihydro‐1,3‐oxazol‐2‐yl)phenol, (III)]. In these compounds, the deviation from coplanarity of the oxazoline and benzene rings is dependent on the position of the hydroxy group on the benzene ring. The coplanar arrangement in (I) is stabilized by a strong intra­molecular O—H⋯N hydrogen bond. Surprisingly, the 2‐oxazoline ring in mol­ecule B of (II) adopts a ³T₄ (^C2T_C3) conformation, while the 2‐oxazoline ring in mol­ecule A, as well as that in (I) and (III), is nearly planar, as expected. Tetra­mers of mol­ecules of (II) are formed and they are bound together via weak C—H⋯N hydrogen bonds. In (III), strong inter­molecular O—H⋯N hydrogen bonds and weak intra­molecular C—H⋯O hydrogen bonds lead to the formation of an infinite chain of mol­ecules perpendicular to the b direction. This paper also reports a theoretical investigation of hydrogen bonds, based on density functional theory (DFT) employing periodic boundary conditions.     

2‐Formyl­benzonitrile

The title compound, C₈H₅NO, has an intra­molecular O⋯CN contact involving an O⋯C distance of 2.797 (2) Å and a C—C—N bond angle of 174.5 (2)°, both indicative of a weak nucleophilic attack of the aldehyde O atom on the electrophilic C atom in the nitrile group. Calculations at the B3LYP density functional level using the 6–31G* basis set support this inter­pretation; natural bond‐order analysis indicates an n_O1→π delocalization energy of 6.3 kJ mol⁻¹. Similar results were obtained from density functional calculations on three related mol­ecules. The 2‐formyl­benzonitrile mol­ecules pack in sheets as a consequence of C—H⋯N and C—H⋯O hydrogen bonds.     

Naphthalene‐1,7‐diol

The asymmetric unit of the title compound, C₁₀H₈O₂, contains two planar symmetry‐independent mol­ecules linked by an O—H⋯O hydrogen bond. In the crystal structure, mol­ecules are linked into infinite chains of rings, formed by a combination of O—H⋯O and C—H⋯O hydrogen bonds, and additionally reinforced by π–π stacking inter­actions. Adjacent chains are connected by weak C—H⋯π inter­actions.     

Salicylaldehyde 4,4′‐(hexane‐1,6‐di­yl)­thio­semicarbazone

The title compound, C₁₄H₁₉N₃OS, is in the thio­keto form, with the thione S and hydrazine N atoms cis with respect to each other so that the S atom is involved in inter‐ and intra­molecular hydrogen bonds simultaneously. Inter­molecular C—H⋯S and C—H⋯O hydrogen bonds result in one‐dimensional polymeric chains of mol­ecules along the a axis. A weak C—H⋯π ring inter­action binds the polymeric chains together.     

Dichloro­{2‐[2‐(dimethyl­ammonio)­ethyl­imino­meth­yl]‐4‐nitro­phenolato}­zinc(II) in unsolvated and hemihydrate forms

The two title complexes, [ZnCl₂(C₁₁H₁₅N₃O₃)], (I), and [ZnCl₂(C₁₁H₁₅N₃O₃)]·0.5H₂O, (II), are mononuclear zinc(II) compounds. In both structures, the Zn^II atom is four‐coordinated in a tetra­hedral configuration by one imine N atom and one phenolate O atom of a Schiff base, and by two Cl atoms. The structure of each of the two zinc(II) complex molecules of (II) is similar to that of (I). In (I), the mol­ecules are linked through inter­molecular hydrogen bonds, forming a three‐dimensional framework. In (II), the solvent water mol­ecules are linked to the zinc(II) moieties through inter­molecular O—H⋯O and O—H⋯Cl hydrogen bonds. The mol­ecules in (II) are further linked via other inter­molecular hydrogen bonds, forming a three‐dimensional framework.     

Benzoin 4‐ethyl­thio­semicarbazone

In the title compound, 2‐hydr­oxy‐1,2‐diphenyl­ethanone 4‐ethyl­thio­semicarbazone, C₁₇H₁₉N₃OS, the thio­semi­carbazone moiety is planar and has an E configuration. The planar phenyl rings make dihedral angles of 82.34 (8) and 8.07 (17)° with the plane of the thio­semicarbazone moiety. The crystal structure contains two intra­molecular (N—H⋯O and N—H⋯N) and one inter­molecular inter­action (O—H⋯S), as well as two C—H⋯π(benzene) inter­actions. Mol­ecules are stacked in columns running along the a axis. Mol­ecules in each column are connected to each other by means of linear O—H⋯S hydrogen bonds and C—H⋯π inter­actions. In addition, there are also C—H⋯π(benzene) inter­actions between the columns.     

6‐(2‐Chloro­acetamido)­hexa­noic acid

Crystals of the title compound, C₈H₁₄ClNO₃, belong to the space group Cc and are characterized by an asymmetric unit containing two mol­ecules, both with a twisted conformation. The mol­ecular packing is stabilized by N—H⋯O=C hydrogen bonds between the amide groups of mol­ecules with the same conformation. In addition, hydrogen‐bonded cyclic carboxylic acid dimers are established between mol­ecules with a different conformation. The ClCH₂—CONH bond has a cis conformation in order to favour an intra­molecular Cl⋯HN electrostatic inter­action. Weak intra‐ and inter­molecular CH₂⋯O=C inter­actions are also present.     

catena‐Poly[[[triaqua­cobalt(II)]‐μ‐2,6‐dioxo‐1,2,3,6‐tetra­hydro­pyrimidine‐4‐carboxyl­ato(2–)] 1.72‐hydrate]

The Co^II ion in the title complex {[Co(C₅H₂N₂O₄)(H₂O)₃]·1.72H₂O}_n, has a distorted octa­hedral coordination geometry comprised of three water ligands, one deprotonated pyrimidine N atom and an adjacent carboxyl­ate O atom of one orotate ligand. The sixth coordination site is occupied by an exocyclic O atom from a neighbouring orotate moiety, and through this inter­action a helicoidal chain is formed. The mol­ecules are linked by intra­molecular O_water—H⋯O and inter­molecular N—H⋯O and O_water—H⋯O hydrogen bonds, forming a three‐dimensional network.     

2′‐Deoxy‐7‐propynyl‐7‐deaza­adenosine: a DNA duplex‐stabilizing nucleoside

In the title compound, 2′‐deoxy‐7‐propynyl‐7‐deaza­adenosine, C₁₄H₁₆N₄O₃, the torsion angle of the N‐glycosylic bond is anti [χ = −130.7 (2)°]. The sugar pucker of the 2′‐deoxy­ribo­furanosyl moiety is C2′‐endo–C3′‐exo, ²T₃ (S‐type), with P = 185.9 (2)° and τ_m = 39.1 (1)°, and the orientation of the exocyclic C4′—C5′ bond is −ap (trans). The 7‐substituted propynyl group is nearly coplanar with the heterocyclic base moiety. Mol­ecules of the nucleoside form a layered network in which the heterocyclic bases are stacked head‐to‐tail with a closest distance of 3.197 (1) Å. The crystal structure of the nucleoside is stabilized by three inter­molecular hydrogen bonds of types N—H⋯ O, O—H⋯ N and O—H⋯ O.     

(Z)‐1‐Ferrocenyl‐3‐(3‐hydroxy­anilino)­but‐2‐en‐1‐one and (Z)‐1‐ferrocenyl‐3‐(4‐hydroxy­anilino)­but‐2‐en‐1‐one

The title compounds, both [Fe(C₅H₅)(C₁₅H₁₄NO₂)], crystallize with Z′ = 2 in the centrosymmetric space group P. In each compound, there is an intra­molecular N—H⋯O=C hydrogen bond, and pairs of inter­molecular O—H⋯O=C hydrogen bonds link the mol­ecules into chains, parallel to [10] in the 3‐hydr­oxy compound and parallel to [10] in the 4‐hydr­oxy compound.     

2‐Amino‐7‐chloro‐2′‐deoxy­tubercidin

In 4‐chloro‐7‐(2‐de­oxy‐β‐d ‐erythro‐pento­furanos­yl)‐7H‐pyr­rolo­[2,3‐d]­pyrimidine‐2,4‐diamine, C₁₁H₁₄ClN₅O₃, the conformation of the N‐glycosylic bond is between anti and high‐anti [χ = −102.5 (6)°]. The 2′‐deoxy­ribofuranosyl unit adopts the C3′‐endo‐C4′‐exo (³T₄) sugar pucker (N‐type) with P = 19.6° and τ_m = 32.9° [terminology: Saenger (1989). Landolt‐Börnstein New Series, Vol. 1, Nucleic Acids, Subvol. a, edited by O. Madelung, pp. 1–21. Berlin: Springer‐Verlag]. The orientation of the exocyclic C4′—C5′ bond is +ap (trans) with a torsion angle γ = 171.5 (4)°. The compound forms a three‐dimensional network that is stabilized by four inter­molecular hydrogen bonds (N—H⋯O and O—H⋯N) and one intra­molecular hydrogen bond (N—H⋯Cl).     

N,N′‐Bis(2‐pyridylmeth­yl)ferrocene‐1,1′‐diyldicarboxamide and N,N′‐bis­(3‐pyridylmeth­yl)ferrocene‐1,1′‐diyldicarboxamide

The mol­ecules of N,N′‐bis­(2‐pyridylmeth­yl)ferrocene‐1,1′‐diyl­dicarboxamide, [Fe(C₁₂H₁₁N₂O)₂], contain intra­molecular N—H⋯N hydrogen bonds and are linked into sheets by three independent C—H⋯O hydrogen bonds. The mol­ecules of the isomeric compound N,N′‐bis­(3‐pyridylmeth­yl)ferrocene‐1,1′‐diyldicarboxamide lie across inversion centres, and the mol­ecules are linked into sheets by a combination of N—H⋯N hydrogen bonds and π–π stacking inter­actions between pyridyl groups.