Weakly Bonded Molecular Networks Built from Tetranitro- and Tetracyanospirobifluorenes
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- 作者：Eric Demers ;
D="cg049590tb00001"> ; Thierry Maris ; Janie Cabana ;D="cg049590tb00002"> ; Jean-Hugues Fournier ;D="cg049590tb00003"> ; and James D. Wuest - 刊名：Crystal Growth & Design
- 出版年：2005
- 出版时间：May 2005
- 年：2005
- 卷：5
- 期：3
- 页码：1237 - 1245
- 全文大小：954K
- 年卷期：v.5,no.3(May 2005)
- ISSN：1528-7505
文摘
Three tetranitro and three tetracyano derivatives of 9,9'-spirobifluorene were synthesized andcrystallized, and their structures were determined by X-ray crystallography. 2,2',7,7'-Tetranitro-9,9'-spirobi[9H-fluorene] (4) self-associates via C-H···O interactions to give an open supramolecular network, with 31% of the totalvolume of the crystal available for including guests. Tetracyano analogue 5 also crystallizes to give a porous network,but no significant C-H···N interactions are present; instead, molecular association is directed primarily by 
-stacking.An extended tetranitro analogue, 2,2',7,7'-tetrakis(4-nitrophenyl)-9,9'-spirobi[9H-fluorene] (6), crystallizes as a nearlyclose-packed structure held together by a combination of C-H···O interactions and -stacking. Tetracyano analogue7 crystallizes to form an open structure maintained by -stacking, without significant C-H···N contacts. Extendedmeta-substituted analogues, 2,2',7,7'-tetrakis(3-nitrophenyl)-9,9'-spirobi[9H-fluorene] (8) and 2,2',7,7'-tetrakis(3-cyanophenyl)-9,9'-spirobi[9H-fluorene] (9), were also synthesized and crystallized. The two structures are closelysimilar and show close-packed architectures involving mainly -stacking. Together, these observations suggest thatcyano groups are not effective acceptors for the formation of C-H···N interactions strong enough to direct molecularassociation in competition with aryl-aryl interactions, at least in the spirobifluorene system. In contrast, nitrogroups can be used to help direct association via C-H···O interactions, either in competition with or in cooperationwith other weak interactions.
-stacking.An extended tetranitro analogue, 2,2',7,7'-tetrakis(4-nitrophenyl)-9,9'-spirobi[9H-fluorene] (6), crystallizes as a nearlyclose-packed structure held together by a combination of C-H···O interactions and -stacking. Tetracyano analogue7 crystallizes to form an open structure maintained by -stacking, without significant C-H···N contacts. Extendedmeta-substituted analogues, 2,2',7,7'-tetrakis(3-nitrophenyl)-9,9'-spirobi[9H-fluorene] (8) and 2,2',7,7'-tetrakis(3-cyanophenyl)-9,9'-spirobi[9H-fluorene] (9), were also synthesized and crystallized. The two structures are closelysimilar and show close-packed architectures involving mainly -stacking. Together, these observations suggest thatcyano groups are not effective acceptors for the formation of C-H···N interactions strong enough to direct molecularassociation in competition with aryl-aryl interactions, at least in the spirobifluorene system. In contrast, nitrogroups can be used to help direct association via C-H···O interactions, either in competition with or in cooperationwith other weak interactions.