Sterically-Limited Self-Assembly of Pt4 Macrocycles into Discrete Non-covalent Nanotubes: Porous Supramolecular Tetramers and Hexamers

• Published in: Chemistry : a European journal Vol. 18; no. 43; pp. 13712 - 13721
• Main Authors: Frischmann, Peter D., Sahli, Brian J., Guieu, Samuel, Patrick, Brian O., MacLachlan, Mark J.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 22.10.2012; WILEY‐VCH Verlag; Wiley; Wiley Subscription Services, Inc
• Subjects: Chemistry; Chemistry, Multidisciplinary; Diffraction; macrocycles; microporous materials; Physical Sciences; platinum; Science & Technology; self-assembly; stacking interactions; POROSITY; ACTIVATION; CRYSTAL-STRUCTURE; COMPLEXES; stacking interactions; ADSORPTION; MOLECULES; self-assembly; platinum; macrocycles; microporous materials; PLATINUM(II); ORTHO-DISUBSTITUTED BENZENES; DERIVATIVES; AGGREGATION
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201201536

We report a template‐free strategy based on steric repulsion for the isolation of discrete columnar aggregates of macrocycles. Specifically, introduction of sterically‐demanding trityl‐derived substituents at the periphery of Pt4 Schiff base macrocycles limits the otherwise infinite one‐dimensional columnar aggregation to discrete tetrameric and hexameric assemblies. Single crystal X‐ray diffraction studies of these compounds reveal discrete nanotubes of finite length that pack inefficiently resulting in three‐dimensional networks of interconnected void space. The discrete assemblies were studied by N2 adsorption and show enhanced surface area when stacked. In the absence of bulky substituents the macrocycles are nonporous. This strategy for engineering discrete supramolecular macrocyclic aggregates may be generalized to other columnar assembling systems. Stacked to the max: Sterically demanding substituents limit the columnar organization of metallomacrocycles into discrete hexamers and tetramers (see figure). By limiting one‐dimensional macrocycle aggregation to finite non‐covalent nanotubes, significant molecular porosity is engineered into the materials. The concepts presented here for isolating discrete aggregates may be generalized to other one‐dimensional assembling systems.