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A series of dendritic ammonium salts have been designed and synthesized. Subsequently, they were used to construct the corresponding [2]rotaxanes by a template-directed clipping approach. Unusually, two unsymmetrical dendritic [2]rotaxanes containing fluorophore (pyrene units) were also obtained; their optical properties, such as UV/vis absorption and fluorescence, were measured. The results indicate that these two rotaxanes possess stronger intermolecular interaction in the solid state than in solution. As a result, solutions of high concentration readily formed the excimer. These special rotaxanes might be applied in dynamic fluorescence-reponsive materials, and the rotaxane structure will also be used as a strategy to adjust the aggregated behaviors of fluorescent molecules. [ABSTRACT FROM AUTHOR]

A squaraine rotaxane scaffold with four alkyne groups is readily converted into a range of dendritic architectures using high-yielding copper-catalyzed alkyne azide cycloaddition (CuAAC) chemistry. A convergent synthesis approach is more efficient than a divergent pathway. Dendritic squaraine rotaxanes with peripheral amine groups can be further functionalized to produce multivalent deep-red fluorescent derivatives that exhibit high brightness and outstanding chemical stability in biological solution. The surface groups on these functionalized fluorescent dendrimers include guanidinium, mannose, and phosphatidylcholine. [ABSTRACT FROM AUTHOR]