Self-Assembly and Photothermal Conversion of MetallaRussian Doll and Metalla[2]catenanes Induced via Multiple Stacking Interactions

A variety of organometallic supramolecular architectureshave beenconstructed over the past decades and their properties were also exploredvia different strategies. However, the synthesis of metalla-Russiandoll is still a fascinating challenge. Herein, a series of new coordinationsupramolecular complexes, including a metalla-Russian doll, metalla[2]catenanes,and metallarectangles, were synthesized by using meticulously selectedCp*Rh (Cp* = & eta;(5)-C5Me5) buildingunits (E1, E2, and E3) and three rigid anthracylpyridine ligands (L1,L2, and L3) via a self-assembly strategy. While the combination ofthe short ligand L1 and E1 or E2 generated two metallarectangles,the longer ligand L2 containing an alkynyl group resulted in two new[2]catenanes, most likely due to which the strong electron-donatingeffect of alkynyl groups causes self-accumulation. Interestingly,an unusual Russian doll assembly was obtained through the reactionof L3 and E3 based on sextuple & pi;& BULL;& BULL;& BULL;& pi; stackinginteractions. Furthermore, the dynamic structural conversion between[2]catenanes and the corresponding metallarectangles could be observedthrough concentration-, solvent-, and guest-induced effects. The [2]catenanecomplexes 4b displayed efficient photothermal conversion efficiencyin solution (20.2%), in comparison with other organometallic macrocycles.We believe that & pi;& BULL;& BULL;& BULL;& pi; stacking interactionsgenerate active nonradiative pathways and promote radiative photodeactivationpathways. This study proves the versatility of half-sandwich buildingunits, not only to build complicated supramolecular topologies butalso in effective functional materials for various appealing applications.