85 research outputs found
Coordination polymers and isomerism; a study using silver(I) and a ∏-stacked ligand
The ligand 2,5-bis(2-pyridylmethylsulfanylmethyl)pyrazine (L) was prepared by the base coupling of 2-(sulfanylmethyl)pyridine and 2,5-bis(chloromethyl)pyrazine. This new ligand was treated with AgClO₄ in a 1 1 metal-to-ligand ratio and with AgNO₃in a 2 1 metal-to-ligand ratio to give coordination polymers. The crystal structures of {[Ag(L)]ClO₄}∞ ( 1) and {[Ag₂(L)](NO₃)₂}∞ ( 2) were determined. The Ag(I) ions in the one-dimensional polymeric chains of 1 adopted square-pyramidal geometries with the pyridine and pyrazine N donors coordinated in an extremely bent fashion. The structure of 2 revealed two isomeric polymer chains in the one crystal forming a single supramolecular array. The isomeric polymers differed in the donor atoms about the Ag(I) ions and in the arrangement of adjacent ligands along the chain. A feature of both structures was that L adopted a three-layer ∏-stacked arrangement
A redetermination at low temperature of the structure of triethylammonium bromide
The structure of the title compound, C6H16N+·Br−, was determined at low temperature and the cell dimensions were comparable to those reported for room-temperature studies [James, Cameron, Knop, Newman & Falp, (1985). Can. J. Chem.
63, 1750–1758]. Initial analysis of the data led to the assignment of P31
c as the space group rather than P63
mc as reported for the room-temperature structure. Careful examination of the appropriate |F
o| values in the low-temperature data showed that the equalities |F(
kl)| = |F(h
l)| and |F(hkl)| = |F(hk
)| did not hold at low temperature, confirming P31c as the appropriate choice of space group. As a consequence of this choice, the N atom sat on a threefold axis and the ethyl arms were not disordered as observed at room temperature. The crystal studied was an inversion twin with a 0.68 (3):0.32 (3) domain ratio
1,4-Bis(iodomethyl)benzene
The centrosymmetric title compound, C8H8I2, was prepared by metathesis from the dibromo analogue. In the crystal structure, weak C—H⋯I interactions link the molecules into stacks down the b axis. The structure is further stabilized by short I⋯I contacts [3.8433 (2) Å], forming undulating sheets in the (101) plane
6-Hydroxy-5,7,8-trimethylchroman-2-one
The title compound, C12H14O3, consists of a chromanone unit with an –OH substituent at the 4-position and methyl substituents on the remaining C atoms of the aromatic ring. The fused pyranone ring adopts a distorted envelope conformation with the methylene group adjacent to the carbonyl carbon as the flap atom. The crystal structure is stabilized by classical O—H⋯O hydrogen bonds and weak C—H⋯O and C—H⋯π interactions, generating a three-dimensional network
2-Methyl-4,6-bis(1-methylhydrazino)pyrimidine
In the title compound, C7H14N6, the amine groups of the two methylhydrazino substituents are orientated in the opposite direction to the methyl substituent at the 2-position of the pyrimidine ring. The molecule is almost planar with only the two amine N atoms lying substantially out of the mean plane of the pyrimidine ring [by 0.1430 (2) and 0.3092 (2) Å]. The H atoms on these amine groups point inwards towards the aromatic ring, such that the lone pair of electrons points outwards from the molecule. Each molecule is linked to two others through N—H⋯N hydrogen bonds between the two amino groups, forming a one-dimensional chain in the [010] direction. Offset face-to-face π–π stacking interactions between the pyrimidine rings organize these chains into a two-dimensional array [centroid–centroid distance = 3.789 (2) Å]
Gel actuators based on polymeric radicals
Low-voltage electrochemical actuation of radical polymer gels has been demonstrated in an organic electrolyte. Polymer gels were prepared by post-modification of active-ester precursor gels with an amine-functionalised radical. A combination of few-layer graphene and multiwall carbon nanotubes gave high conductivity and improved actuation in the gels, with 32% linear actuation. The actuator system showed good stability over at least 10 cycles, showing its promise. The cycle time was several hours due to mass-transport limited transport of ions and solvent into the device
4-[(E)-2-Ferrocenylethenyl]-1,8-naphthalic anhydride
In the structure of the title compound, [Fe(C5H5)(C19H11O3)], the plane of the substituted ferrocene ring is tilted by 14.17 (6)° with respect to the mean plane through the naphthalene ring system. In the crystal structure, centrosymmetric dimers are formed through π–π interactions [centroid–centroid distance = 3.624 (2) Å] between the substituted ferrocene ring and the three fused rings of the naphthalic anhydride unit. Pairs of dimers are held together by further naphthalene–naphthalene π–π interactions [distance between parallel mean planes 3.45 (3) Å]. Each dimer interacts with four neighbouring dimers in a herringbone fashion through C—H⋯π interactions, so forming a two-dimensional sheet-like structure
1-(3-Bromopropyl)-4-(2-pyridyl)-1H-1,2,3-triazole
In the structure of the title compound, C10H11BrN4, the plane of the substituted 1,2,3-triazole ring is tilted by 14.84 (10)° with respect to the mean plane of the pyridine ring. The pyridine and closest triazole N atoms adopt an anti arrangement which removes any lone pair–lone pair repulsions between the N atoms. This conformation is further stabilized by weak intermolecular C—H⋯N interactions. There are two molecules in the unit cell, which form a centrosymmetric head-to-tail dimer. The dimers are stabilized through π–π interactions [centroid–centroid distance = 3.733 (4) Å and mean interplanar distance = 3.806 (12) Å] between the substituted 1,2,3-triazole ring and the pyridine rings in adjacent molecules. Each dimer interacts with two neighbouring dimers above and below, forming a slipped stack of dimers through the crystal. The 3-bromopropyl chain sits over the pyridine ring of a neighbouring molecule and the triazole rings of nearby molecules are adjacent
Phenyl 2,3-O-isopropylidene-1-thio-α-d-rhamnopyranoside
In the title compound, C15H20O4S, a dioxolane ring is fused to the pyran ring of the sugar which carries a thiophenyl substituent on the anomeric C atom. The dioxolane ring adopts an envelope conformation and the pyran ring system a distorted 4
C
1 chair. The structure is stabilized by O—H⋯O hydrogen bonds, forming centrosymmetric dimers that generate an R
2
2(10) ring motif. Additional C—H⋯O interactions form an extended network. Two C atoms of the phenyl ring are disordered over two positions; the site occupancy factors are ca. 0.7 and 0.3
N-Methacryloyl-4-(piperidin-1-yl)-1,8-naphthalimide
In the title compound, C21H20N2O3, the naphthalimide unit is almost planar (r.m.s. deviation for the 15 non-H atoms = 0.059 Å). The carboximide N atom and the five C atoms of the 2-methylprop-2-enoyl substituent also lie in a plane (r.m.s. deviation = 0.009 Å), which subtends an angle of 84.34 (7)° to the naphthalamide plane. This orients the =CH2 group of the vinyl fragment towards the naphthalimide rings, giving the molecule an extended configuration. The piperidine ring adopts a chair conformation and there is evidence for some delocalization between the naphthalene and piperidine units, the C—Npip bond length being 1.404 (4) Å. In the crystal structure, π–π contacts with centroid–centroid distances of 3.5351 (18) and 3.7794 (18) Å supported by C—H⋯O hydrogen bonds link adjacent molecules in a head-to-tail fashion, forming dimers. These are further stabilized by other C—H⋯O contacts of varying strength, which stack the molecules down the b axis
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