Structural Transformations in a Crystal during the Photochemical Reaction of 2-Benzyl-5-benzylidenecyclopentanone

Structural changes taking place in a crystal during an intramolecular photochemical reaction [the Yang photocyclization of the α-methylbenzylamine salt with 1-(4-carboxybenzoyl)-1-methyladamantane] were monitored step-by-step using X-ray structure analysis. This is the first example of such a study carried out for an intramolecular photochemical reaction. During the photoreaction, both the reactant and product molecules change their orientation, but the reactant changes more rapidly after the reaction is about 80% complete. The distance between directly reacting atoms in the reactant molecule is almost constant until about 80% reaction progress and afterwards decreases. The torsion angle defined by the reactant atoms that form the cyclobutane ring also changes in the final stages of the photoreaction. These phenomena are explained in terms of the influence of many product molecules upon a small number of reacting molecules. The adamantane portion shifts more than the remaining part of the anionic reactant species during the reaction, which is explained in terms of hydrogen bonding. The structural changes are accompanied by changes in the cell constants. The results obtained in the present study are compared with analogous results published for intermolecular reactions.

Download Full-text

Structural Transformations in Crystals Induced by Radiation and Pressure. Part 10. The Crystallographic Picture of Photochemical Behaviour of bi(anthracene-9,10-dimethylene) under High Pressure

Crystals ◽

10.3390/cryst10111031 ◽

2020 ◽

Vol 10 (11) ◽

pp. 1031

Author(s):

Julia Bąkowicz ◽

Ilona Turowska-Tyrk

Keyword(s):

High Pressure ◽

Intermolecular Interactions ◽

Photochemical Reaction ◽

Molecular Orientation ◽

Reaction Path ◽

Structural Transformations ◽

Initial Increase ◽

Ambient Conditions ◽

Photochemical Behaviour ◽

Pressure Part

The results of the monitoring of the [4 + 4] photocycloaddition reaction path in single crystals of bi(anthracene-9,10-dimethylene) at high pressure are presented. The crystal structures for several steps of the phototransformation at 0.3 GPa and 1.0 GPa were determined and analysed. The applied high pressure did not halt the photochemical reaction and almost 100% of the product molecules were obtained, although the reaction was very slowly reversible similarly to that of ambient conditions. During the crystal phototransformation the intramolecular geometry, molecular orientation and intermolecular interactions of the reactant changed more and more towards the values observed for the product. The initial increase in the unit cell volume brought about by the photochemical reaction was diminished by high pressure. High pressure itself did not significantly influence the intramolecular geometry of the reactant and product molecules, but it influenced the intermolecular interactions.

Download Full-text

Monitoring Structural Transformations in Crystals. Part 15. Structural Changes in Crystals Caused by UV Radiation Despite the Lack of a Photochemical Reaction

Journal of Chemical Crystallography ◽

10.1007/s10870-012-0286-9 ◽

2012 ◽

Vol 42 (6) ◽

pp. 593-599 ◽

Cited By ~ 6

Author(s):

Julia Bąkowicz ◽

Renata Siedlecka ◽

Ilona Turowska-Tyrk

Keyword(s):

Uv Radiation ◽

Photochemical Reaction ◽

Structural Changes ◽

Structural Transformations

Download Full-text

Monitoring structural transformations in crystals. 11. Yang photocyclizations – one type of reaction, but diversity of structural changes

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768107051336 ◽

2007 ◽

Vol 63 (6) ◽

pp. 933-940 ◽

Cited By ~ 13

Author(s):

Ilona Turowska-Tyrk ◽

Julia Bąkowicz ◽

John R. Scheffer

Keyword(s):

Hydrogen Bonds ◽

Photochemical Reaction ◽

Structural Changes ◽

Structural Transformations ◽

Geometrical Parameters ◽

Reaction Centre ◽

Carboxylate Group ◽

Molecular Fragments ◽

Reaction Progress ◽

X Ray

Structural changes proceeding in a crystal during the Yang photocyclization of the salt 6,6-diethyl-5-oxo-5,6,7,8-tetrahydronaphthalene-2-carboxylate with (1S)-1-(4-methylphenyl)ethylamine were monitored by means of X-ray structure analysis. The course of the photoreaction was evaluated on the basis of the geometrical parameters for the pure reactant crystal. Variations in the cell constants, the product content, the geometry of the reaction centre, the orientation of molecular fragments and the geometry of hydrogen bonds were described and analyzed. It was found that the cell volume increased until 56% product content and decreased thereafter. The distance between the directly reacting C atoms was constant, ∼ 3.0 Å, until ∼ 75% reaction progress. Analysis of the distance between atoms that would participate in the formation of the second (unobserved) enantiomorph excluded the formation of such an isomer. Molecular fragments varied their orientation during the photoreaction, and the largest change was observed for the carboxylate group despite its participation in strong hydrogen bonds. The geometry of the hydrogen bonds changed during the photoreaction. The largest change was 0.17 Å for the D...A distance and 13° for the D—H...A angle. A comparison of the intra- and intermolecular parameters for the studied salt with data for other compounds undergoing the Yang photocyclization in crystals revealed a diversity of structural changes brought about by this type of photochemical reaction.

Download Full-text

Structural Transformation of a Germanium Σ=13 (510) [001] Tilt Grain Boundary under the Electron Beam

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100179014 ◽

1990 ◽

Vol 48 (1) ◽

pp. 52-53 ◽

Cited By ~ 1

Author(s):

Jean-Luc Rouvière ◽

Alain Bourret

Keyword(s):

Electron Microscopy ◽

High Resolution ◽

Grain Boundary ◽

Structural Transformation ◽

Mirror Symmetry ◽

High Resolution Electron Microscopy ◽

Structural Transformations ◽

Covalent Bonds ◽

Resolution Electron ◽

Tilt Grain Boundary

The possible structural transformations during the sample preparations and the sample observations are important issues in electron microscopy. Several publications of High Resolution Electron Microscopy (HREM) have reported that structural transformations and evaporation of the thin parts of a specimen could happen in the microscope. Diffusion and preferential etchings could also occur during the sample preparation.Here we report a structural transformation of a germanium Σ=13 (510) [001] tilt grain boundary that occurred in a medium-voltage electron microscopy (JEOL 400KV).Among the different (001) tilt grain boundaries whose atomic structures were entirely determined by High Resolution Electron Microscopy (Σ = 5(310), Σ = 13 (320), Σ = 13 (510), Σ = 65 (1130), Σ = 25 (710) and Σ = 41 (910), the Σ = 13 (510) interface is the most interesting. It exhibits two kinds of structures. One of them, the M-structure, has tetracoordinated covalent bonds and is periodic (fig. 1). The other, the U-structure, is also tetracoordinated but is not strictly periodic (fig. 2). It is composed of a periodically repeated constant part that separates variable cores where some atoms can have several stable positions. The M-structure has a mirror glide symmetry. At Scherzer defocus, its HREM images have characteristic groups of three big white dots that are distributed on alternatively facing right and left arcs (fig. 1). The (001) projection of the U-structure has an apparent mirror symmetry, the portions of good coincidence zones (“perfect crystal structure”) regularly separate the variable cores regions (fig. 2).

Download Full-text