Structural disorder and transformation in crystal growth: direct observation of ring-opening isomerization in a metal-organic solid solution

A rare example is reported in which discrete Ag2 L 2 ring and (AgL)∞ chain motifs [L = N,N'-bis(3-imidazol-1-yl-propyl)-pyromellitic diimide] co-crystallize in the same crystal lattice with varying ratios and degrees of disorder. Crystal structures obtained from representative crystals reveal c...

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Bibliographic Details
Published in:IUCrJ 2014-09, Vol.1 (Pt 5), p.318-327
Main Authors: Jiang, Ji-Jun, He, Jian-Rong, Lü, Xing-Qiang, Wang, Da-Wei, Li, Guo-Bi, Su, Cheng-Yong
Format: Article
Language:English
Subjects:
Chemical properties
Crystal lattices
Crystal structure
crystallization
Crystals
Diimide
disorder
Disorders
Isomerization
Isomers
Observations
Organometallic compounds
Research Papers
ring-opening isomerism
solid solution
Solid solutions
structural transformation
Structure
Transformations
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Summary:A rare example is reported in which discrete Ag2 L 2 ring and (AgL)∞ chain motifs [L = N,N'-bis(3-imidazol-1-yl-propyl)-pyromellitic diimide] co-crystallize in the same crystal lattice with varying ratios and degrees of disorder. Crystal structures obtained from representative crystals reveal compatible packing arrangements of the cyclic and polymeric isomers within the crystal lattice, which enables them to co-exist within a crystalline solid solution. A feasible pathway for transformation between the isomers is suggested via facile rotation of the coordinating imidazolyl groups. This chemical system could provide a chance for direct observation of ring-opening isomerization at the crystal surface. Mass spectrometry and (1)H NMR titration show a dynamic equilibrium between cyclic and oligomeric species in solution, and a potential crystallization process is suggested involving alignment of precursors directed by aromatic stacking interactions between pyromellitic diimide units, followed by ring-opening isomerization at the interface between the solid and the solution. Both cyclic and oligomeric species can act as precursors, with interconversion between them being facile due to a low energy barrier for rotation of the imidazole rings. Thermogravimetric analysis and variable-temperature powder X-ray diffraction indicate a transition to a different crystalline phase around 120°C, which is associated with loss of solvent from the crystal lattice.
ISSN:2052-2525
2052-2525
DOI:10.1107/S2052252514015966