Two new cadmium(II) coordination polymers based on imidazole‐containing ligands: synthesis, structural characterization and fluorescence properties

• Published in: Acta crystallographica. Section C, Crystal structure communications Crystal structure communications, 2020-04, Vol.76 (4), p.314-321
• Main Authors: Li, Bing-Feng, Xu, Xi-Ting, Dong, Tong-Min, Zhou, Wan-Ying, Gu, Yang, Gong, Lei, Zhong, Kai-Long
• Format: Article
• Language: English
• Subjects: Anions; Benzene; Cadmium; coordination polymer; Coordination polymers; crystal structure; Diffraction patterns; Fluorescence; fluorescence properties; hexafluorosilicate; Hydrocarbons; Hydrogen bonds; Imidazole; Infrared analysis; Infrared spectroscopy; Ions; Ligands; Metal-organic frameworks; Polymers; Properties (attributes); Structural analysis; thermal properties; X-ray diffraction
• ISSN: 2053-2296; 0108-2701; 2053-2296; 1600-5759
• DOI: 10.1107/S2053229620002594

The judicious selection of suitable ligands is vitally important in the construction of novel metal–organic frameworks (MOFs) with fascinating structures and interesting properties. Recently, imidazole‐containing multidentate ligands have received much attention. Two new CdII coordination frameworks, namely, poly[tris{μ‐1,4‐bis[(1H‐imidazol‐1‐yl)methyl]benzene‐κ2N3:N3′}tetrakis(nitrato‐κ2O,O′)dicadmium], [Cd2(NO3)4(C14H14N4)3]n, (I), and poly[[bis{μ3‐1,3,5‐tris[(1H‐imidazol‐1‐yl)methyl]benzene‐κ3N3:N3′:N3′′}cadmium] hexafluorosilicate], {[Cd(C18H18N6)2](SiF6)}n, (II), have been synthesized and characterized by elemental analysis, IR spectroscopy and single‐crystal X‐ray diffraction. In polymer (I), the 1,4‐bis[(1H‐imidazol‐1‐yl)methyl]benzene ligand bridges Cd2+ ions with a distorted seven‐coordinated pentagonal bipyramidal geometry, forming a one‐dimensional ladder chain, and the nitrate anions coordinate to the Cd2+ ions in a terminal bidentate fashion. In the crystal, adjacent chains are further connected by C—H…O hydrogen bonds to generate a two‐dimensional (2D) supramolecular structure. Polymer (II) exhibits a 2D layered structure in which 1,3,5‐tris[(1H‐imidazol‐1‐yl)methyl] benzene ligands join Cd2+ centres having a six‐coordinated octahedral structure. The layers are connected by hexafluorosilicate anions via C—H…F hydrogen‐bond interactions, giving rise to a three‐dimensional supramolecular network structure in the solid state. In addition, powder X‐ray diffraction (PXRD) patterns were recorded, thermogravimetric analyses (TGA) carried out and fluorescence properties investigated. Two CdII coordination polymers have been synthesized from 1,4‐bis[(1H‐imidazol‐1‐yl)methyl]benzene and 1,3,5‐tris[(1H‐imidazol‐1‐yl)methyl]benzene ligands, forming a distorted seven‐coordinated pentagonal bipyramidal geometry and a one‐dimensional ladder chain with the former ligand, and a six‐coordinated octahedral structure with layers connected by hexafluorosilicate anions with the latter.