The Intricate Structural Chemistry of MII2nLn‑Type Assemblies
datasetposted on 12.06.2017, 13:51 authored by Giacomo Cecot, Mathieu Marmier, Silvano Geremia, Rita De Zorzi, Anna V. Vologzhanina, Philip Pattison, Euro Solari, Farzaneh Fadaei Tirani, Rosario Scopelliti, Kay Severin
The reaction of cis-blocked, square-planar MII complexes with tetratopic N-donor ligands is known to give metallasupramolecular assemblies of the formula M2nLn. These assemblies typically adopt barrel-like structures, with the ligands paneling the sides of the barrels. However, alternative structures are possible, as demonstrated by the recent discovery of a Pt8L4 cage with unusual gyrobifastigium-like geometry. To date, the factors that govern the assembly of MII2nLn complexes are not well understood. Herein, we provide a geometric analysis of M2nLn complexes, and we discuss how size and geometry of the ligand is expected to influence the self-assembly process. The theoretical analysis is complemented by experimental studies using different cis-blocked PtII complexes and metalloligands with four divergent pyridyl groups. Mononuclear metalloligands gave mainly assemblies of type Pt8L4, which adopt barrel- or gyrobifastigium-like structures. Larger assemblies can also form, as evidenced by the crystallographic characterization of a Pt10L5 complex and a Pt16L8 complex. The former adopts a pentagonal barrel structure, whereas the latter displays a barrel structure with a distorted square orthobicupola geometry. The Pt16L8 complex has a molecular weight of more than 23 kDa and a diameter of 4.5 nm, making it the largest, structurally characterized M2nLn complex described to date. A dinuclear metalloligand was employed for the targeted synthesis of pentagonal Pt10L5 barrels, which are formed in nearly quantitative yields.
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Pt 8 L 4 cagePt II complexesself-assembly processsquare-planar M II complexesM II 2 n L n complexesdinuclear metalloligandtetratopic N-donor ligandsIntricate Structural Chemistrypentagonal Pt 10 L 5 barrelssquare orthobicupola geometrybarrel structurelatter displaysgyrobifastigium-like structuresM 2 n L n complexes4.5 nmgyrobifastigium-like geometrytype Pt 8 L 4formula M 2 n L n23 kDaalternative structurespyridyl groupspentagonal barrel structureligands panelingMononuclear metalloligandsPt 10 L 5metallasupramolecular assembliesbarrel-like structuresPt 16 L 8M 2 n L n