Ferrocene compounds: methyl 1′‐aminoferrocene‐1‐carboxylate

The title compund, [Fe(C₅H₆N)(C₇H₇O₂)], features one strong intermolecular hydrogen bond of the type N—H...O=C [N...O = 3.028 (2) Å] between the amine group and the carbonyl group of a neighbouring molecule, and vice versa, to form a centrosymmetric dimer. Furthermore, the carbonyl group acts as a double H‐atom acceptor in the formation of a second, weaker, hydrogen bond of the type C—H...O=C [C...O = 3.283 (2) Å] with the methyl group of the ester group of a second neighbouring molecule at (x, −y − , z − ). The methyl group also acts as a weak hydrogen‐bond donor, symmetry‐related to the latter described C—H...O=C interaction, to a third molecule at (x, −y − , z + ) to form a two‐dimensional network. The cyclopentadienyl rings of the ferrocene unit are parallel to each other within 0.33 (3)° and show an almost eclipsed 1,1′‐conformation, with a relative twist angle of 9.32 (12)°. The ester group is twisted slightly [11.33 (8)°] relative to the cylopentadienyl plane due to the above‐mentioned intermolecular hydrogen bonds of the carbonyl group. The N atom shows pyramidal coordination geometry, with the sum of the X—N—Y angles being 340 (3)°.     

3,3′‐[o‐Phenyl­enebis­(methyl­eneoxy)]­bis(6‐chloro­flavone) and 3,3′‐propyl­ene­dioxy­bis­[6‐chloro‐2‐(2‐furyl)‐4H‐1‐benzopyran‐4‐one]

The title compound 3,3′‐[o‐phenyl­enebis­(methyl­eneoxy)]­bis(6‐chloro­flavone), C₃₈H₂₄Cl₂O₆, (I), crystallizes in the monoclinic space group C2/c, with the molecules lying across twofold rotation axes so that there is half a mol­ecule in the asymmetric unit, while the other title compound, 3,3′‐propyl­ene­dioxy­bis­[6‐chloro‐2‐(2‐furyl)‐4H‐1‐benzopyran‐4‐one], C₂₉H₁₈Cl₂O₈, (II), crystallizes in monoclinic space group P2₁/n with one mol­ecule in the asymmetric unit. In both compounds, the benzopyran moiety is nearly planar, with dihedral angles between the two fused rings of 1.43 (8)° in (I), and 2.54 (7) and 3.00 (6)° with respect to the benzopyran moieties in the two halves of (II). The furan rings are twisted by 8.3 (1) and 8.4 (1)° in the two halves of (II). In both compounds, the molecular structure is stabilized by intramolecular C—H⃛O hydrogen bonds, while the crystal packing is stabilized by C—H⃛Cl and C—H⃛O intermolecular hydrogen bonds in (I) and (II), respectively.     

Influence of fluorine substitution on the molecular conformation of 3′‐deoxy‐3′‐fluoro‐5‐methyluridine

Fluorine substitutions on the furanose ring of nucleosides are known to strongly influence the conformational properties of oligonucleotides. In order to assess the effect of fluorine on the conformation of 3′‐deoxy‐3′‐fluoro‐5‐methyluridine (^RT^F), C₁₀H₁₃FN₂O₅, we studied its stereochemistry in the crystalline state using X‐ray crystallography. The compound crystallizes in the chiral orthorhombic space group P2₁2₁2₁ and contains two symmetry‐independent molecules (A and B) in the asymmetric unit. The furanose ring in molecules A and B adopts conformations between envelope (²E, 2′‐endo, P = 162°) and twisted (²T₃, 2′‐endo and 3′exo, P = 180°), with pseudorotation phase angles (P) of 164.3 and 170.2°, respectively. The maximum puckering amplitudes, ν_max, for molecules A and B are 38.8 and 36.1°, respectively. In contrast, for 5‐methyluridine (^RT^OH), the value of P is 21.2°, which is between the ³E (3′‐endo, P = 18.0°) and ³T₄ (3′‐endo and 4′‐exo, P = 36°) conformations. The value of ν_max for ^RT^OH is 41.29°. Molecules A and B of ^RT^F generate respective helical assemblies across the crystallographic 2₁‐screw axis through classical N—H…O aand O—H…O hydrogen bonds supplemented by C—H…O contacts. Adjacent parallel helices of both molecules are linked to each other via O—H…O and O…π interactions.     

3,3′‐Dinitro‐2,2′‐dithiodipyridine

In the title compound, C₁₀H₆N₄O₄S₂, (I), the molecule has a centre of inversion. The structure is a positional isomer of 5,5′‐dinitro‐2,2′‐dithiodipyridine [Brito, Mundaca, Cárdenas, López‐Rodríguez & Vargas (2007). Acta Cryst. E 63 , o3351–o3352], (II). The 3‐nitropyridine fragment of (I) shows excellent agreement with the bonding geometries of (II). The most obvious differences between them are in the S—S bond length [2.1167 (12) Å in (I) and 2.0719 (11) Å in (II)], and in the C—C_ipso—N_ring [119.8 (2)° in (I) and 123.9 (3)° in (II)] and S—C—C [122.62 (18)° in (I) and 116.0 (2)° in (II)] angles. The crystal structure of (I) has an intramolecular C—H...O interaction, with an H...O distance of 2.40 (3) Å, whereas this kind of interaction is not evident in (II). The molecules of (I) are linked into centrosymmetric R⁴₄(30) motifs by a C—H...O interaction. There are no aromatic π–π stacking and no C—H...π(arene) interactions. Compound (I) can be used as a nucleophilic tecton in self‐assembly reactions with metal centres of varying lability.     

Poly­[manganese(II)‐μ2‐benzidine‐κ2N:N′‐μ3‐bi­phenyl‐2,2′‐di­carboxylato‐κ4O:O′,O′′:O′′′]

The title compound, [Mn(C₁₄H₈O₄)(C₁₂H₁₂N₂)]_n, with a novel three‐dimensional framework, has been prepared by a hydro­thermal reaction at 433 K. Each Mn atom lies on a twofold axis in a slightly distorted octahedral geometry, coordinated by two N atoms from two benzidine ligands and four O atoms from three symmetry‐related biphenyl‐2,2′‐dicarboxylate (bpdc) ligands. The benzidine ligands lie about inversion centres and the bpdc ligands about twofold axes. Each bpdc ligand is bonded to three Mn ions to form a continuous chain of metal ions. The bpdc ligands are accommodated in a series of distorted holes resembling hexagonal prisms.     

A low‐temperature modification of hexa‐tert‐butyldisilane and a new polymorph of 1,1,2,2‐tetra‐tert‐butyl‐1,2‐diphenyldisilane

Crystals of hexa‐tert‐butyldisilane, C₂₄H₅₄Si₂, undergo a reversible phase transition at 179 (2) K. The space group changes from Ibca (high temperature) to Pbca (low temperature), but the lattice constants a, b and c do not change significantly during the phase transition. The crystallographic twofold axis of the molecule in the high‐temperature phase is replaced by a noncrystallographic twofold axis in the low‐temperature phase. The angle between the two axes is 2.36 (4)°. The centre of the molecule undergoes a translation of 0.123 (1) Å during the phase transition, but the conformation angles of the molecule remain unchanged. Between the two tri‐tert‐butylsilyl subunits there are six short repulsive intramolecular C—H...H—C contacts, with H...H distances between 2.02 and 2.04 Å, resulting in a significant lengthening of the Si—Si and Si—C bonds. The Si—Si bond length is 2.6863 (5) Å and the Si—C bond lengths are between 1.9860 (14) and 1.9933 (14) Å. Torsion angles about the Si—Si and Si—C bonds deviate by approximately 15° from the values expected for staggered conformations due to intramolecular steric H...H repulsions. A new polymorph is reported for the crystal structure of 1,1,2,2‐tetra‐tert‐butyl‐1,2‐diphenyldisilane, C₂₈H₄₆Si₂. It has two independent molecules with rather similar conformations. The Si—Si bond lengths are 2.4869 (8) and 2.4944 (8) Å. The C—Si—Si—C torsion angles deviate by between −3.4 (1) and −18.5 (1)° from the values expected for a staggered conformation. These deviations result from steric interactions. Four Si—C(t‐Bu) bonds are almost staggered, while the other four Si—C(t‐Bu) bonds are intermediate between a staggered and an eclipsed conformation. The latter Si—C(t‐Bu) bonds are about 0.019 (2) Å longer than the staggered Si—C(t‐Bu) bonds.     

Cocrystallization of adamantane‐1,3‐dicarboxylic acid and 4,4′‐bipyridine

The cocrystallization of adamantane‐1,3‐dicarboxylic acid (adc) and 4,4′‐bipyridine (4,4′‐bpy) yields a unique 1:1 cocrystal, C₁₂H₁₆O₄·C₁₀H₈N₂, in the C2/c space group, with half of each molecule in the asymmetric unit. The mid‐point of the central C—C bond of the 4,4′‐bpy molecule rests on a center of inversion, while the adc molecule straddles a twofold rotation axis that passes through two of the adamantyl C atoms. The constituents of this cocrystal are joined by hydrogen bonds, the stronger of which are O—H...N hydrogen bonds [O...N = 2.6801 (17) Å] and the weaker of which are C—H...O hydrogen bonds [C...O = 3.367 (2) Å]. Alternate adc and 4,4′‐bpy molecules engage in these hydrogen bonds to form zigzag chains. In turn, these chains are linked through π–π interactions along the c axis to generate two‐dimensional layers. These layers are neatly packed into a stable crystalline three‐dimensional form via weak C—H...O hydrogen bonds [C...O = 3.2744 (19) Å] and van der Waals attractions.     

Synthesis and Crystal Structure of Peptide‐2,2′‐Biphenyl Hybrids

1,1′‐Biphenyl derivatives with amino acid/peptide substitution at C(2) and C(2′) (‘peptide‐biphenyl hybrids', 6 – 8 ) have been prepared by direct N‐acylation of amino acid/peptide derivatives with 1,1′‐biphenyl‐2,2′‐dicarbonyl dichloride ( 5 ). Both conformers, which arise from the rotation around the aryl aryl bond, have been detected by ¹H‐NMR spectroscopy. Single atropisomers of each 6 ((R)‐configuration at the stereogenic axis) and 7 ((S)‐configuration at the stereogenic axis) have been obtained in quantitative yield by slow evaporation of methanolic solutions. The procedures are dynamic atropselective resolutions (asymmetric transformations of the second kind). The crystal structures of the peptide‐biphenyl hybrids 6 and 7 show highly ordered molecular and supramolecular structures with extensive intramolecular and intermolecular H‐bonding.     

cis,cis,cis‐(Acetato‐O,O′)­bis­[1,2‐bis­(di­phenyl­phosphino)­ethane‐P,P′]­ruthenium(II) hexa­fluoro­phosphate di­methanol solvate

In the cation of the title complex, cis,cis,cis‐[Ru(η²‐O₂CMe)(dppe)₂]PF₆·2MeOH [dppe is 1,2‐bis­(di­phenyl­phosphino)­ethane, C₂₆H₂₄P₂], the Ru atom is in a pseudo‐octahedral coordination environment with two chelating dppe ligands and one chelating acetate ligand. Intra‐phosphine and intra‐acetate bond lengths and angles are unexceptional. Deviations from idealized octahedral coordination angles at ruthenium [O—Ru—O 59.43 (8)° and P—Ru—P 103.19 (2)°] presumably derive from constraints imposed by the chelate rings. The Ru—P distances for the mutually trans P‐donor atoms [2.3785 (6) Å] are significantly longer than those for the Ru—P linkages trans to the acetate ligand [2.3074 (6) Å]. The Ru1, C1 and C2 atoms lie on a twofold axis, and atom P3 of the anion lies on an inversion centre.     

Synthesis and properties of new aromatic poly‐(ether benzoxazole)s from 2,2′‐bis(4‐amino‐3‐hydroxyphenoxy)biphenyl and aromatic dicarboxylic acid chlorides

A new bis(o‐aminophenol) with a crank and twisted noncoplanar structure and ether linkages, 2,2′‐bis(4‐amino‐3‐hydroxyphenoxy)biphenyl, was synthesized by the reaction of 2‐benzyloxy‐4‐fluoronitrobenzene with biphenyl‐2,2′‐diol, followed by reduction. Biphenyl‐2,2′‐diyl‐containing aromatic poly(ether benzoxazole)s with inherent viscosities of 0.52–1.01 dL/g were obtained by a conventional two‐step procedure involving the polycondensation of the bis(o‐aminophenol) monomer with various aromatic dicarboxylic acid chlorides, yielding precursor poly(ether o‐hydroxyamide)s, and subsequent thermal cyclodehydration. These new aromatic poly(ether benzoxazole)s were soluble in methanesulfonic acid, and some of them dissolved in m‐cresol. The aromatic poly(ether benzoxazole)s had glass‐transition temperatures of 190–251 °C and were stable up to 380 °C in nitrogen, with 10% weight losses being recorded above 520 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2656–2662, 2002     

Double anomeric effects and a hydrogen‐bonded supramolecular motif in N,N′‐bis(3‐nitrophenyl)methanediamine

In the title compound, C₁₃H₁₂N₄O₄, the molecule lies on a crystallographic twofold axis. Molecules are linked into complex sheets parallel to (100) via one N—H...O and two C—H...O hydrogen bonds. Within the molecule, the 3‐nitroanilino fragment is essentially planar, and the C—N—C—N—C fragment assumes a nearly perpendicular/perpendicular conformation, with C—N—C—N torsion angles of 81.18 (18)°, which is controlled by a pair of adjacent anomeric interactions. The findings constitute the first demonstration of two anomeric effects existing in one N—C—N unit.     

2,2′‐[2,3‐Di­hydro‐2‐(prop‐2‐enyl)‐1H‐isoindole‐1,3‐diyl­idene]bis(propane­di­nitrile)–tetra­thia­fulvalene (1/1), TCPI–TTF

The title complex, C₁₇H₉N₅·C₆H₄S₄, contains π‐deficient bis(di­nitrile) and TTF mol­ecules stacked alternately in columns along the a‐axis direction; the interplanar angle between the TTF molecule and the isoindolinyl C₄N[C(CN)₂]₂ moiety is 1.21 (4)°. The N‐allyl moiety in the TCPI mol­ecule is oriented at an angle of 87.10 (10)° with respect to the five‐membered C₄N ring, and the four C[triple‐bond]N bond lengths range from 1.134 (3) to 1.142 (3) Å, with C—C[triple‐bond]N angles in the range 174.3 (3)–176.9 (2)°. In the TTF system, the S—C bond lengths are 1.726 (3)–1.740 (3) and 1.751 (2)–1.763 (2) Å for the external S—C(H) and internal S—C(S) bonds, respectively.     

Host/Guest Simulation of Fluorescent Probes Adsorbed into Low‐Density Polyethylene, 1. Excimer Formation of 1,3‐Di(1‐pyrenyl)propane

Molecular dynamics and Rotational Isomer State/Monte Carlo techniques with a Dreiding 1.01 Force Field are employed to study the excimer formation of isolated 1,3‐di(1‐pyrenyl)propane and the probe adsorbed into a low‐density polyethylene (LDPE) matrix model. The probability of formation of each molecular conformer at several temperatures was calculated using these theoretical techniques. Conformational statistical analysis of the four torsion angles (ϕ₁, ϕ₂, θ₁, θ₂) of Py3MPy showed that the angles —C—C^ar— (ϕ₁, ϕ₂) present two states c ^± = ±90°; and the angles —C—C— (θ₁, θ₂), the three trans states = 180°, g ^± = ±60°. The correlation of θ₁–θ₂ torsion angles showed that the most probable pairs were g⁺g^– and g^–g⁺ for the excimer‐like specimens, although these angles are distorted because of interactions with the polymer matrix. The temperature dependence of the excimer‐formation probability revealed that this process was thermodynamically controlled in the isolated case. When the probe was adsorbed into the LDPE matrix, the excimer formation process was reversed at T = 375 K. At T >  375 K, the behavior was similar to the isolated case but, at T < 375 K, excimer formation probability increased with temperature as found experimentally by steady‐state fluorescence spectroscopy. This temperature was coincident with the onset of the LDPE melting process, determined experimentally by thermal analysis.     

Two polymorphs of 4‐propyl‐3,4‐dihydro‐2H‐naphtho[1,2‐b]pyran‐5,6‐dione

Two polymorphs of the title compound, C₁₆H₁₆O₃, have been obtained from the same solution. One polymorph, (I_m), crystallizes in the monoclinic space group P2₁, while the other, (I_o), crystallizes in the orthorhombic space group P2₁2₁2₁. The cell constants of the two polymorphs are surprisingly similar. Whereas the a and b axes are equal in the two structures, the c axis in (I_o) is twice as long as that in (I_m). The monoclinic angle β is 95.084 (9)° compared with 90° in the orthorhombic crystal system. The cell volume of (I_m) is almost exactly half of the cell volume of (I_o). The packing motifs are also very similar in the two structures. However, whereas the molecules in (I_m) are related by a twofold screw axis just in the direction of the b axis, in (I_o) there are twofold screw axes along all three directions of the unit cell.     

Cobalt(II) and cobalt(III) complexes with 4′‐(4‐cyanophenyl)‐2,2′:6′,2′′‐terpyridine

4′‐Cyanophenyl‐2,2′:6′,2′′‐terpyridine (cptpy) was employed as an N,N′,N′′‐tridentate ligand to synthesize the compounds bis[4′‐(4‐cyanophenyl)‐2,2′:6′,2′′‐terpyridine]cobalt(II) bis(tetrafluoridoborate) nitromethane solvate, [Co^II(C₂₂H₁₄N₄)₂](BF₄)₂·CH₃NO₂, (I), and bis[4′‐(4‐cyanophenyl)‐2,2′:6′,2′′‐terpyridine]cobalt(III) tris(tetrafluoridoborate) nitromethane sesquisolvate, [Co^III(C₂₂H₁₄N₄)₂](BF₄)₃·1.5CH₃NO₂, (II). In both complexes, the cobalt ions occupy a distorted octahedral geometry with two cptpy ligands in a meridional configuration. A greater distortion from octahedral geometry is observed in (I), which indicates a different steric consequence of the constrained ligand bite on the Co^II and Co^III ions. The crystal structure of (I) features an interlocked sheet motif, which differs from the one‐dimensional chain packing style present in (II). The lower dimensionality in (II) can be explained by the disturbance caused by the larger number of anions and solvent molecules involved in the crystal structure of (II). All atoms in (I) are on general positions, and the F atoms of one BF₄⁻ anion are disordered. In (II), one B atom is on an inversion center, necessitating disorder of the four attached F atoms, another B atom is on a twofold axis with ordered F atoms, and the C and N atoms of one nitromethane solvent molecule are on a twofold axis, causing disorder of the methyl H atoms. This relatively uncommon study of analogous Co^II and Co^III complexes provides a better understanding of the effects of different oxidation states on coordination geometry and crystal packing.     

(4,4′‐Bipyridine)dichloroman­ganese(II), a two‐dimensional ­coordination polymer

The title compound, [MnCl₂(C₁₀H₈N₂)]_n, crystallizes with a two‐dimensional network constructed from linear chains of edge‐sharing MnCl₄ square‐planar units cross‐linked by bidentate 4,4′‐bi­pyridine bridges. The Mn atom and the bipyridine moieties lie on sites with 222 crystallographic symmetry; the Cl atom lies on a twofold axis. The bi­pyridine mol­ecule is twisted about the central C—C bond by 33.5 (3)°.     

13‐cis‐β,β‐Carotene and 15‐cis‐β,β‐carotene

13‐cis‐β,β‐Carotene, C₄₀H₅₆, crystallizes with a complete molecule in the asymmetric unit, whereas 15‐cis‐β,β‐carotene, also C₄₀H₅₆, has twofold symmetry about an axis through the central bond of the polyene chain. The polyene methyl groups are arranged on one side of the polyene chains for each molecule and the 6‐s‐cisβ end groups, with the cyclohexene rings in half‐chair conformations, are twisted out of the planes of the polyene chains by angles ranging from 41.37 (17) to 52.2 (4)°. The molecules in each structure pack so that the arms of one occupy the cleft of the next, and there is significant π–π stacking of the almost‐parallel polyene chains of the 15‐cis isomer, which approach at distances of 3.319 (1)–3.591 (1) Å.     

2′‐Deoxy‐5‐fluorotubercidin

In the title compound, 4‐amino‐7‐(2‐deoxy‐β‐d ‐erythro‐pentofuranosyl)‐5‐fluoro‐7H‐pyrrolo[2,3‐d]pyrimidine, C₁₁H₁₃FN₄O₃, the conformation of the glycosyl bond lies between anti and high anti [χ = −101.1 (3)°]. The furanose moiety adopts the S‐type sugar pucker (²T₃), with P = 164.7 (3)° and τ = 40.1 (2)°. The extended structure is a three‐dimensional hydrogen‐bond network involving a C—H⋯F, two N—H⋯O and two O—H⋯O hydrogen bonds.     

catena‐Poly[[(1,10‐phenanthroline‐κ2N,N′)manganese(II)]‐di‐μ‐salicylato‐κ4O:O′]

In the title polymeric complex, [Mn(C₇H₅O₃)₂(C₁₂H₈N₂)]_n, the Mn^II atom is located on a twofold axis and displays a distorted octa­hedral coordination geometry, formed by four salicylate anions and one 1,10‐phenanthroline (phen) mol­ecule. The salicylate anions doubly bridge the Mn^II atoms to form one‐dimensional polymeric chains. A comparison of Mn—O bond distances with the corresponding Mn—O—C angles suggests a significant electrostatic content in the Mn—O bonds. A face‐to‐face distance of 3.352 (7) Å between neighbouring parallel phen planes indicates π–π stacking inter­actions between polymeric chains.     

1,3(R):4,6(R)‐Di‐O‐benzyl­idene‐d‐mannitol

The title compound, C₂₀H₂₂O₆, has crystallographic twofold symmetry. The central six‐C‐atom chain has an extended conformation similar to that of d ‐mannitol, with two independent C—C—C—C torsion angles of 165.69 (14) and 177.60 (12)°. The 1,3‐dioxane ring has a chair conformation. All chiral centers have the R configuration.