Multicomponent Self‐Assembly of Pd^II/Pt^II Interlocked Molecular Cages: Cage‐to‐Cage Conversion and Self‐Sorting in Aqueous Medium

Abstract

Coordination‐driven self‐assembly is an efficient approach for constructing complicated molecules with the aid of reversible bond formation. However, constructing topologically complicated interlocked systems and their formation studies remain challenging tasks. The formation of two water‐soluble hexanuclear interlocked cages by multicomponent self‐assembly of a flexible triimidazole donor (L1) and a rigid tripyridyl donor (L2) based on a triazine core in combination with 90° cis‐blocked PdII and PtII acceptors is reported here. Formation of interlocked systems having a composition of M6(L1)2(L2)2 (M=Pd or Pt) becomes feasible through cavity‐induced self‐recognition of two similar units having a composition of M3(L1)(L2). Self‐sorting of two independently prepared cages of [M3(L1)2] and [M6(L2)4] in aqueous medium leads to the formation of interlocked systems, and their formation was monitored by time‐dependent 1H NMR spectroscopy. Self‐recognition of L1 by [M6(L2)4] or L2 by [M3(L1)2] leads to the formation of interlocked systems, as confirmed from 1H NMR spectroscopic titrations of L1 with cages {M6(L2)4} and L2 with {M3(L1)2}, respectively. Both the interlocked cages of Pd and Pt are highly stable, and formation of either system is equally probable as observed from the treatments of Pd3(L1)2 with Pt6(L2)4 or Pt3(L1)2 with Pd6(L2)4, which lead to the formation of two different self‐assembled homometallic interlocked cages [Pt6(L1)2(L2)2+Pd6(L1)2(L2)2] instead of forming any other heterometallic assemblies. Formation of interlocked cages is dependent on the steric bulk of the diamine ligand bound to the metal acceptors. A N‐alkyl‐substituted blocking amine prefers the non‐interlocked cage instead of the interlocked analogue.

Transformation networks of metal–organic cages controlled by chemical stimuli

“… 86 The generality of this approach was further demonstrated by Mukherjee's preparation of related interlocked Pt II or Pd II cages, employing an imidazole-containing ligand in place of one of the pyridyl-based ligands. 87 Another key approach was developed by Stang, using a mixture of carboxylate and pyridyl ligands to form a series of heteroleptic Pt II -based architectures. 39 …”

Non‐Covalent Interaction‐Directed Coordination‐Driven Self‐Assembly of Non‐Trivial Supramolecular Topologies

“…Three component self‐assembly of M(II) (M=Pd, Pt) acceptor and two distinctive tripodal ligands in a 3 : 1 : 1 stoichiometry resulted in the formation of thermodynamically stable interlocked cage complexes in D 2 O at 100 °C. Mukherjee and co‐workers have also reported the three‐component self‐assembly of a series of triply interlocked Pd 12 coordination prisms in aqueous medium [47b,c] . In 2014, Stang, Chi and coworkers reported template‐free, coordination‐driven self‐assemblies of interlocked cages 29 and 30 using tetracene and naphthalene‐based Ru(II) acceptors and 1,3,5‐tris(3‐(pyridin‐4‐yl)‐1H‐pyrazol‐1‐yl)benzene donor ( L23 ) in 2 : 3 stoichiometry (Scheme 16).…”

A New Pt(II) Complex with Anionic s-Triazine Based NNO-Donor Ligand: Synthesis, X-ray Structure, Hirshfeld Analysis and DFT Studies

“…Several ligands have been synthesized based on the s- triazine as a core structure and have been explored in coordination chemistry [ 1 ]. Mukherjee et al constructed a complicated coordinated molecule by coordination-driven self-assembly of homometallic Pd/Pt-based s -triazine ligand as interlocked molecular cages [ 2 ]. Motloch et al reported the synthesis of the Pt(II)/Pd(II) complex with s -triazine-type ligands for the purpose of hydrogen bonded/metal-coordination hybrid [ 3 ].…”