Published September 30, 2001 | Version v1
Journal article Open

Three-dimensional hydrogen-bonded supramolecular networks assembled by lanthanide picrates and 4,4'-bipyridine

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Department of Chemistry, Guangxi Normal University, Guilin, Guangxi 541004, P. R. China

E-mail : bioinorganicchem@263.net                hurx@mailbox.gxnu.edu.cn

Analysis Center, Chengdu Branch of Chinese Academy of Science, Chengdu, Sichuan 610041 P. R. China

Manuscript received 4 September 2000. revised 15 March 2001, accepted 24 March 2001

The reactions of rare earth picrates with 4,4' -bpy in H2O-CH3CN give compounds [Tm(H2O )4(pic)2]2[Tm(H2O)6(pic)](4,4' -bpy)5(pic)6 (1) and [Gd2(4,4'-bpy)(pic)2( H2O)12](4,4'-bpy)5(H2O)6(pic)4 (2) (4,4'-bpy = 4,4'-bipyridine, pic- = picric anion). A supramolecular unit cell of compound 1 is assembled by intermolecular hydrogen bond from three independent complex cations which are crystallographically distinguishable. Such units arc bridged in the form of side-by-side by 4,4'-bpy molecules via hydrogen bond to form stair-like chains, and then an elegant 20-network structure. Furthermore, a supramolecular 3D-network is constructed by hydrogen bond formed by uncoordinated picric anion and coordinated water molecules. Both coordinative and hydrogen bonds contribute to networking in compound 2 based on 4,4'-bpy-bridgcd binuclear units which have been shown to be linked in the form of head-to-tail by double hydrogen-bond bridges of the type Gd-H2O ... 4,4'-bpy ...H2O ... H2O-Gd, producing zig-zag chains. The chains are further extended into hydrogen-bonded 3d network. This generates supramolecular cavities which incorporate some uncoordinated picric anions and 4,4' -bpy as guests via  host-guest hydrogen bonding. Magnetic susceptibilities measured for compound 2 from 75 to 300 K arc indication of no appreciable magnetic exchange interaction between the adjacent GdIII ions.

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