scholarly journals Structural transformations in crystals induced by radiation and pressure. Part 1. How pressure influences the intramolecular photochemical reactions in crystals

CrystEngComm ◽  
2014 ◽  
Vol 16 (27) ◽  
pp. 6039-6048 ◽  
Author(s):  
Julia Bąkowicz ◽  
Ilona Turowska-Tyrk
Keyword(s):  
Structural Transformations ◽  
Photochemical Reactions ◽  
Pressure Part

scholarly journals Photochemical Reactions of Hydrogen-bonded Coordination Polymers

2014 ◽  
Vol 70 (a1) ◽  
pp. C529-C529
Author(s):  
Jagadese Vittal
Keyword(s):  
Metal Ions ◽  
Coordination Polymers ◽  
Structural Transformations ◽  
Photochemical Reactions ◽  
Supramolecular Interactions ◽  
Network Structures ◽  
Experimental Conditions ◽  
Hydrogen Bonding Interactions ◽  
Kinetic Phenomenon ◽  
Solvent Molecules

Crystallization is a kinetic phenomenon and the experimental conditions like solvents, concentration, pH, temperature and time have greater influence on the nature of products in the synthesis of coordination network structures. During crystallization, the solvents and ligands bind to the metal ions reversibly and hence, the least soluble polymer will crystallize first, independent of the metal-ligand ratio used in the crystallization. The kinetic products quite often contain solvents bonded to the metal ions. The removal of these coordinated solvents is likely to transform the kinetically formed coordination polymers (CPs) into thermodynamically stable products. In these structural conversions, supramolecular interactions play a major role. Such structural transformations as well as [2+2] cycloaddition reactions have been demonstrated in many coordination polymeric network structures aided by the directional hydrogen bonding interactions. A number of structural transformations involving the loss of solvent molecules and use of photodimerization reactions in the solid state will be presented in this talk.

Monitoring structural transformations in crystals. 12. Course of an intramolecular [4 + 4] photocycloaddition in a crystal

2008 ◽  
Vol 64 (3) ◽  
pp. 375-382 ◽  
Author(s):  
Elżbieta Trzop ◽  
Ilona Turowska-Tyrk
Keyword(s):  
Hydrogen Bonds ◽  
Cell Volume ◽  
Molecular Shape ◽  
Structural Transformations ◽  
Photochemical Reactions ◽  
Molecular Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crystal And Molecular Structures ◽  
Orientation Of Molecules

Variations in crystal and molecular structures, brought about by the intramolecular [4 + 4] photocycloaddition of bi(anthracene-9,10-dimethylene), were monitored using X-ray diffraction. The cell volume increased by 0.8% until the reaction was ca 40% complete, and afterwards decreased by 1.6% during the remainder of the photoreaction. The changes of the a and b lattice parameters were correlated with the changes of the molecular shape and packing. The distance between the directly reacting C atoms varied in a manner not observed for other photochemical reactions in crystals. It was constant until ca 20% photoreaction progress, then decreased, and later stabilized from ca 40% photoreaction progress. This phenomenon was explained by interplay between stress resulting from the presence of product molecules and the rigidity of reactant molecules. Changes of the orientation of molecules during the photoreaction were smaller than in the case of other monitored photochemical reactions in crystals owing to similarities in the shape and packing of reactant and product molecules. Weak C—H...π hydrogen bonds exist among reactant molecules in the pure reactant and partly reacted crystals.

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