Anisotropic Poisson Effect and Deformation-Induced Fluorescence Change of Elastic 9,10-Dibromoanthracene Single Crystals

Elastic organic crystals have attracted considerable attention as next-generation flexible smart materials. However, the detailed information on both molecular packing change and macroscopic mechanical crystal deformations upon applied stress is still insufficient. Herein, we report that fluorescent single crystals of 9,10-dibromoanthracene are elastically bendable and stretchable, which allows a detailed investigation of the deformation behavior. We clearly observed a Poisson effect for the crystal, where the short axes (b and c-axes) of the crystal are contracted upon elongation along the long axis (a-axis). Moreover, we found that the Poisson's ratios along the b-axis and c-axis are largely different. Theoretical molecular simulation suggests that the tilting motion of the anthracene may be responsible for the large deformation along the c-axis. Spatially resolved photoluminescence (PL) measurement of the bent elastic crystals reveals that the PL spectra at the outer (elongated), central (neutral), and inner (contracted) sides are different from each other.     

3‐Amino‐1,2,4‐triazine

In the crystal structure of 3‐amino‐1,2,4‐triazine, C₃H₄N₄, the mol­ecules form hydrogen‐bonded chains that are almost parallel to the b axis (3.2°), and which are inclined to the a and c axes by ～21 and ～69°, respectively. The distortion of the 1,2,4‐triazine ring in the crystal is compared with gas‐phase ab initio molecular‐orbital calculations.     

1,5‐Dianilinopentane‐1,3,5‐trione: a crystal structure containing two polymorphic domains

Single crystals of the title compound, C₁₇H₁₆N₂O₃, were obtained by gas diffusion. The observed diffraction pattern is compatible with a superposition of reflections from two monoclinic unit cells with the space group C2/c. The two cells share the a and b axes but not the c axis. Both structures contain layers parallel to (001), with molecules connected by intermolecular N—H...O=C hydrogen bonds. The bonding between adjacent layers is weak. Layer displacements result in a crystal structure containing two closely related polymorphic domains. The structure of one polymorph can be derived from the structure of the other if subsequent layers are displaced by (a/4, b/4, 0) for odd‐numbered layers and by (a/4, −b/4, 0) for even‐numbered layers. Three different crystals were analysed and their observed diffraction patterns were similar, showing all three crystals to contain the polymorphic domain structure.     

Monosodium [1‐hydroxy‐2‐(1H‐imidazol‐3‐ium‐4‐yl)ethane‐1,1‐diyl]bis(phosphonate) tetrahydrate (monosodium isozoledronate)

The title compound, Na⁺·C₅H₉N₂O₇P₂^?·4H₂O, is an isomer of zoledronate, a potent bone antiresorptive bis­phospho­nate drug having significant activity against several parasitic protozoa. The crystal structure of isozoledronate consists of bisphosphonate dimers coordinated by two Na⁺ ions. The dimers are held together through an extensive hydrogen‐bonding network. The crystals exhibit non‐merohedral twinning that roughly superimposes the a and b axes, and inverts the c axis.     

The solid‐state structure of the β‐blocker metoprolol: a combined experimental and in silico investigation

Metoprolol {systematic name: (RS)‐1‐isopropylamino‐3‐[4‐(2‐methoxyethyl)phenoxy]propan‐2‐ol}, C₁₅H₂₅NO₃, is a cardioselective β₁‐adrenergic blocking agent that shares part of its molecular skeleton with a large number of other β‐blockers. Results from its solid‐state characterization by single‐crystal and variable‐temperature powder X‐ray diffraction and differential scanning calorimetry are presented. Its molecular and crystal arrangements have been further investigated by molecular modelling, by a Cambridge Structural Database (CSD) survey and by Hirshfeld surface analysis. In the crystal, the side arm bearing the isopropyl group, which is common to other β‐blockers, adopts an all‐trans conformation, which is the most stable arrangement from modelling data. The crystal packing of metoprolol is dominated by an O—H…N/N…H—O pair of hydrogen bonds (as also confirmed by a Hirshfeld surface analysis), which gives rise to chains containing alternating R and S metoprolol molecules extending along the b axis, supplemented by a weaker O…H—N/N—H…O pair of interactions. In addition, within the same stack of molecules, a C—H…O contact, partially oriented along the b and c axes, links homochiral molecules. Amongst the solid‐state structures of molecules structurally related to metoprolol deposited in the CSD, the β‐blocker drug betaxolol shows the closest analogy in terms of three‐dimensional arrangement and interactions. Notwithstanding their close similarity, the crystal lattices of the two drugs respond differently on increasing temperature: metoprolol expands anisotropically, while for betaxolol, an isotropic thermal expansion is observed.     

Crystal structure of poly(m-phenylene isophthalamide)

The crystal structure of poly(m-phenyulene isophthalamide) was determined by x-ray analysis. The triclinic cell, with a = 5.27 Å, b = 5.25 Å, c (fiber axis) = 11.3 Å, α = 111.5°, β = 111.4° and γ = 88.0° and space group P1, contains one monomeric unit. The crystal density is 1.47 g/cc. The molecules in the crystal are contracted by 1 Å per monomeric unit from the fully extended conformation, and the planes of the benzene rings and adjacent amide groups make angles of about 30°. The crystal is composed of molecular chains connected by N? H···O hydrogen bonds along the a and b axes forming a “jungle gym” network structure. The low tensile modulus of this polymer as compared with that of poly(p-phenylene terephthalamide) is attributed to the contracted molecular conformation.     

Dimorphism of ethyl 1,4‐dihydro‐2,4,6‐triphenylpyridine‐3‐carboxylate

The title compound, C₂₆H₂₃NO₂, (Ia) and (Ib), shows polymorphism with crystals obtained from different solvents displaying different crystal structures. However, it is not the geometry of the single mol­ecules nor the hydrogen‐bond pattern that is different in (Ia) and (Ib), but the way in which the hydrogen‐bonded chains, running along the a‐axis direction, are arranged with respect to each other.     

2‐[(E)‐(4‐Chloro­phenyl)­methyl­ene­amino]‐N‐(X‐methyl­phenyl)‐4,5,6,7‐tetra­hydro‐1‐benzo­thio­phene‐3‐carbox­amide,where X = 2 and 3

The title compounds, both C₂₃H₂₁ClN₂OS, are isomeric, with (I) and (II) being the N‐3‐methyl­phenyl and N‐2‐methyl­phenyl derivatives, respectively. The dihedral angle between the 4‐chloro­phenyl group and the thio­phene ring in (II) [38.1 (1)°] is larger than that in (I) [7.1 (1)°], indicating steric repulsion between the chloro­phenyl and o‐toluidine groups in (II). In both compounds, an intramolecular N—H⋯N hydrogen bond forms a pseudo‐six‐membered ring, thus locking the molecular conformation. In the crystal structures, mol­ecules are connected via N—H⋯O hydrogen bonds, forming chains along the b axis in (I) and along the c axis in (II). Intermolecular C—H⋯O/S and π–π interactions are also observed in (II), but not in (I).     

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.