title: Structural disorder and transformation in crystal growth: direct observation of ring-opening isomerization in a metal-organic solid solution.
abstract: 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.
authors.affiliation: MOE Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, Lehn Institute of Functional Materials, School of Chemistry and Chemical Engineering, Sun Yet-Sun University , Guangzhou 510275, People's Republic of China.
authors.forename: Ji-Jun
authors.initials: JJ
authors.lastname: Jiang
authors.affiliation: MOE Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, Lehn Institute of Functional Materials, School of Chemistry and Chemical Engineering, Sun Yet-Sun University , Guangzhou 510275, People's Republic of China.
authors.forename: Jian-Rong
authors.initials: JR
authors.lastname: He
authors.affiliation: MOE Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, Lehn Institute of Functional Materials, School of Chemistry and Chemical Engineering, Sun Yet-Sun University , Guangzhou 510275, People's Republic of China.
authors.forename: Xing-Qiang
authors.initials: XQ
authors.lastname: Lü
authors.affiliation: MOE Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, Lehn Institute of Functional Materials, School of Chemistry and Chemical Engineering, Sun Yet-Sun University , Guangzhou 510275, People's Republic of China.
authors.forename: Da-Wei
authors.initials: DW
authors.lastname: Wang
authors.affiliation: MOE Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, Lehn Institute of Functional Materials, School of Chemistry and Chemical Engineering, Sun Yet-Sun University , Guangzhou 510275, People's Republic of China.
authors.forename: Guo-Bi
authors.initials: GB
authors.lastname: Li
authors.affiliation: MOE Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, Lehn Institute of Functional Materials, School of Chemistry and Chemical Engineering, Sun Yet-Sun University , Guangzhou 510275, People's Republic of China ; State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences , Shanghai 200032, People's Republic of China.
authors.forename: Cheng-Yong
authors.initials: CY
authors.lastname: Su
keywords: crystallization; disorder; ring-opening isomerism; solid solution; structural transformation