摘要:
IntroductionThe use of predetermined building blocks is of basic relevance in two areasof great current interest dealing, respectively, with the deliberate constructionof coordination networks1and with the designof metal-based supramolecular architectures.2Metal containing subunits with programmed coordination angles can be employedfor the self-assembly of frameworks and of macromolecular polygons andpolyhedral cages, of potential utility for molecular recognition. Many interestingcyclic nanostructures have been obtained in the last years by Fujita,3Stang4and many others,3–5using rational synthetic methods.In these architectures the most frequently employed metal ‘corners’werecis-PdIIandcis-PtIIsquare planar complexes, particularly for the building of supramolecular squares.However, though the self-assembly of discrete macrocyclic architecturesis favoured under thermodynamic equilibration and can be highly convergent,the competitive generation of open-chain oligomers or polymers is oftenobserved.6We report here on the use of a differentcorner unit, namely [Cu(2,2′-bipy)]2+(1), that exhibits twocis-equatorialand two axial free coordination sites. Unit1,with triflate (1a), tetrafluoroborate (1b) or nitrate (1c)as counterions, has been reacted with different bifunctional rigid or flexible,neutral or anionic spacer ligands. Our hypothesis was to obtain derivativeswith the entering ligands coordinated to1in the two equatorial positions (seeScheme 1)and with one or both the axial positions involved in weaker interactions withthe counterions or solvent molecules. Possible target motifs are illustratedinScheme 1, including macromoleculesand polymers, some of which (I–IV) have been ideally associated with the (notstrictly necessary) use of rigid spacers, while the remaining ones (V–VIII)need surely more flexible ligands. In this preliminary study we have operatedin conditions that have favoured the kinetic products, thus obtaining mainly,but not exclusively, polymeric species.
ISSN:1466-8033
DOI:10.1039/b006306l
出版商:RSC
年代:2000
数据来源: RSC