Crystal Structure of the 9-Anthracene–Carboxylic Acid Photochemical Dimer and Its Solvates by X-ray Diffraction and Raman Microscopy

Abstract

The photodimerization of anthracene derivatives constitutes a model system for intermolecular [4 + 4] cycloadditions. In this paper we deal with the elusive 9-anthracene–carboxylic case and study the crystal state of the head-to-tail dimer, obtained by the reaction of the monomer in various solvents both in its unary and solvated forms, by X-ray diffraction and confocal Raman microscopy in the lattice phonon region. A number of solvates have been identified, and their structures have been solved and here presented. The 9-anthracene–carboxylic acid dimer appears to be an exemplary case of a molecular crystal easily prone to host solvent molecules in the interstices of the framework generated by homomolecular hydrogen bonds. Alternatively, the hydrogen bonds between solvent molecules and the carboxylic group may establish supramolecular structures of closely packed architectures. Raman microscopy has also allowed us to investigate the short-lived dimer, which is produced in the crystal-to-crystal photoreaction triggered by the irradiation of the monomer single crystal.

Using light intensity to control reaction kinetics and reversibility in photomechanical crystals

“…When a photodimer is formed, the buttery distortion of the anthracene rings would be expected to affect the hydrogen-bonding to neighboring molecules. 60,61 If the surrounding molecules are all monomers, then there would be an energetic driving force to restore the network of hydrogen-bonds in the unreacted crystal, destabilizing the lone photodimer. At large conversions, however, when the surrounding molecules have been dimerized, it is possible that a new network of hydrogen bonds can be formed that stabilizes the dimers and changes the dissociation energetics.…”

Incorporation of Manganese Complexes within Hybrid Resol-Silica and Carbon-Silica Nanoparticles

“…Three new bands were detected (1020, 1250 and 1390 cm −1 ) and the G band appeared larger (1580–1600 cm −1 ) than with the excitation in the visible range. The weak band at 1020 cm −1 can be attributed to deformations of aromatic rings (δ(ring)) [ 31 , 32 ], which gives us little information, considering that both the ligands and the support present aromatic rings. The 1250 cm −1 is however more interesting and corresponds to a combination mode of aromatic deformation (δ(ring)) and CH deformation(δ(CH)) [ 31 , 32 ].…”

Integrating Photorewritable Fluorescent Information in Shape‐Memory Organohydrogel Toward Dual Encryption

“…Specifically, original multiple peaks at 1026, 1039, 1061, 1083, 1105, 1128, and 1150 cm −1 converted into two board peaks (1143 and 1077 cm −1 ) for anthracene moieties, which correspond to C-C and/or ring deformation modes. [25,26] To further certify the mechanism of the unimer-dimer transition of anthracene moieties, density functional theory (DFT) calculations were employed to analyze the energy gaps and orbital energy levels of the fluorescent monomers involved (Figure 1F). The separation degree of electron cloud between HOMO and LUMO of unimer form is larger than that of dimer form, and the energy gap (ΔE) between HOMO and LUMO of dimer form (1.049 eV) was less than that of unimer form (2.256 eV), indicating that it is more susceptible for unimer to be excited and switched to dimer under 365 nm.…”