Indistinguishability and distinguishability between amide and ester moieties in the construction and properties of M6L8 octahedral nanocages

Abstract

A series of 25 × 25 × 25 ų octahedral coordination cages [Pd₆(L)₈](NO₃)₁₂ (L = L¹, 1; L = L², 2; L¹ = tris(6-quinolyl)trimesic ester; L² = N,N′,N′′-tris(6-quinolyl)-1,3,5-benzenetricarboxamide) is reported. L¹ and L² are indistinguishable for construction of octahedral nanocages, and thus the desirable mixed ligand nanocage comprising a statistical ligand distribution ([Pd₆(L¹)_n(L²)_8−n](NO₃)₁₂, 3) can be efficiently constructed. However, the nanocages are distinguishable for functions such as photoluminescence (PL) and catalysis. The PL intensity is in the order 1 ≫ 3 > 2, wherein 1 shows a blue emission. The nanocages show excellent catalytic activity for the C–C coupling reaction under mild conditions in the order 1 > 3 > 2, presumably owing to the spacer-functional groups.