Abstract:The title compound, C15H10O2, was found to crystallize in the centrosymmetric space group P2(1)/n. The hydrogen bonding is of the cyclic dimer type about a center of symmetry. The carboxyl O atoms are ordered as is the carboxyl H atom. The anthracene core, while less nearly planar, shows good agreement with the anthracene cores of anthracene-9-carboxylic acid and anthracene-1,6-dicarboxylic acid. The carboxyl group plane makes a dihedral angle of 12.4 (2) degrees with the best-fit anthracene core plane.
“…Fig. 4a shows the powder XRD diffraction pattern calculated from the previously obtained structure of a 9-AC single crystal [34]. The calculated peaks correspond well to those observed for the powdered CS rods in Fig.…”
“…Fig. 4a shows the powder XRD diffraction pattern calculated from the previously obtained structure of a 9-AC single crystal [34]. The calculated peaks correspond well to those observed for the powdered CS rods in Fig.…”
“…The putative molecular structure from this attempted refinement was unphysical with respect to geometry, bond lengths, and angles. Differential scanning calorimetry in the temperature range 153-373 K revealed a broad phase transition centered at 230 K. Analysis of the relaxation times of the 13 C resonances of the 4-iodobenzoic acid also showed a change in T 2 at the transition temperature for the phase transition. This phase transition does not, however, cause any drastic change in the molecular structure.…”
Section: Discussionmentioning
confidence: 94%
“…The carboxylic acid moiety is an important structural feature that occurs frequently in crystal engineering and biology. − In general, structures of carboxylic acids in the solid state are dominated by dimers in which the carbonyl oxygen and hydroxyl groups act as donors and acceptors. ,− The structure of this hydrogen-bonded dimer is shown in Figure . 1 Schematic representation of a typical carboxylic acid dimer with the crystallographically generated atoms as X‘.…”
Section: Introductionmentioning
confidence: 99%
“…As also shown in Figure , the full, real space hydrogen bond scheme is often developed via a crystallographic center of inversion. − However, the presence of a carboxylic acid group does not always imply the presence of a dimeric structure and two-dimensional networks and chains have also been observed. In systems where the dimeric structure is observed, the degenerate nature of the atoms involved in the hydrogen-bonded carboxylic acid dimer has attracted the interest of the theoretical community as a model for proton transfer. ,− …”
The solid-state structure of 4-iodobenzoic acid has been confirmed by variable temperature X-ray diffraction, variable temperature solid-state NMR and differential scanning calorimetry. 4-iodobenzoic acid crystallizes in the space group P2(1)/n, and dimerizes in the solid state about a center of inversion. Using extensive X-ray crystallographic data collections, the placement of the carboxylate H atoms from the residual electron density in difference Fourier maps was determined. The position of the electron density associated with the proton is found to vary with temperature in that the population of the disordered sites changes with varying temperature. Determination of the crystal structure between the temperatures of 248 and 198 K was not possible due to a phase transition, an endothermic event occurring at 230.77 K. The phase transition is also indicated by a change in the relaxation time of the ring carbon atoms in the solid-state NMR data. Though the dominating force in the dimeric unit in the solid state is the presence of strong hydrogen bonds, there are also van der Waals forces present between the iodine atoms. In the layered structure, the iodine-iodine distance is within the van der Waals contact radii, an interaction which causes a deformation in the electron density of the iodine atoms.
“…existent in the crystal of anthracene-1-carboxylic acid [16]) if a strong hydrogen bond acceptor molecule is present such as DMSO acting as successful competitor. Under these circumstances, changed structures are formed whilst maintaining, for example, p-stacking as a subordinate synthon mode [17].…”
Two constitutionally isomeric 9,10-anthraquinonecarboxylic acids 1 and 2 are reported to yield DMSO-solvated crystals (1a and 2a) on the crystallization from DMSO. The molecular and crystal structures are described and comparatively discussed with reference to the effect implicated by the different position of the carboxylic group at the anthraquinone basis and the involvement of the solvent molecule.\ud
Anthraquinonecarboxylic acids-DMSO solvates-X-ray analysis-Hydrogen bonding-π-Stacking interactio
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