Metallo-Supramolecular Nanospheres via Hierarchical Self-Assembly

Abstract

A novel coordination oligo/polymer is synthesized by metal-directed self-assembly from equimolar amounts of the (dppp)M(OTf) 2 precursor complexes (dppp = bis-(diphenylphosphino)-propane, OTf = triflate; M = Pd II or M = Pt II ) and banana-shaped bidentate dipyridyl ligands. The assemblies were characterized by ESI mass spectrometry and NMR spectroscopy. The analysis of the cloudy suspension prepared by dissolving the coordination polymer in aqueous methanol solutions indicates nanosized spherical objects to form. Evidence for vesicle formation from these metallo-supramolecular oligomers comes from (cryogenic) transmission electron microscopy (TEM, cryo-TEM). Atomic force microscopy revealed stable nanospheres on hydrophilic mica and monolayer formation on hydrophobic highly oriented pyrolitic graphite (HOPG) substrates. On mica, also torus-shaped object were observed, which are rationalized by vesicles that opened during the drying procedure and released the internal solvent. Elemental analysis of the nanoassemblies by X-ray photoelectron spectroscopy (XPS) indicates uncoordinated and coordinated pyridines in the coordination polymers that form the nanospheres. Various control experiments using different metal centers and modified ligands support the conclusions.

Monte Carlo Simulations of Metallo‐Supramolecular Micelles

“…We will consider the equilibrium between 2:1 and 1:1 ligand-metal complexes formed on the micelle core surface and in the bulk ( Figure 1a) and study the effect of the association energy of metal-ligand complexes, aggregation number and coronablock length on the monomer density distribution and core-surface coverage. The obtained results provide insights on the molecular principles of self-assembly of metallosupramolecular micelles and unzippable micelles (involving reversible interactions between blocks [4][5][6][7][8][9][10][11][12] ) in general, which can help future experimental design of smart (metallo-)supramolecular materials with desired properties.…”

“…''Unzippable'' block copolymers with the blocks of different chemical nature connected to each other by means of other reversible interactions such as hydrogen bonding or inclusion complexes have also been reported in literature. [4][5][6][7][8][9][10][11][12] Due to the heterogeneous structure of their building blocks, metallo-supramolecular micelles exhibit unprecedented capabilities. [3,13] For example, electrochemical, photochemical, and redox properties associated with metal-ligand complexation [14] can be further exploited in metallo-supramolecular micelles to monitor and control material properties.…”

Design and Synthesis of ZnII‐Coordination Polymers Anchored with NSAIDs: Metallovesicle Formation and Multi‐drug Delivery

“…On the other hand, potential nanocarriers such as metallomicelles derived from coordination complexes and coordination polymers, metallovesicles obtained from coordination polymers and metal‐organic polyhedra are accessed relatively easily. The precursor compounds (i.e.…”

“…With this background in mind, we considered the following aspects to develop multi‐drug delivery systems derived from coordination polymer based metallovesicles . We and others reported that in vitro drug delivery was possible from nano‐suspension of coordination polymers; in these studies, the coligand drugs being anchored to the metal center through coordination bond were the integral part of the coordination polymers.…”

“…On the other hand, potential nanocarrierssuch as metallomicelles derived from coordinationc omplexesa nd coordination polymers, [27] metallovesicles obtained from coordination polymers [28,29] and metal-organic polyhedra [30,31] are accessed relatively easily.T he precursor compounds (i.e. coordination complexes, coordination polymers and metal-organic polyhedra) are amenable to easy synthetic modulation guided by atomic level structural characterization by single crystal X-ray crystallography.…”