LiFE Assessment Tool

As part of an ongoing study to construct a molecular Turing machine in which a polymer chain is encoded via allosteric information transfer between macrocyclic complexes, we describe the thermodynamic and kinetic characterization of a multicomponent self-assembled system based on a zinc porphyrin macrocyclic compound, a bidentate ligand (1,4-diazabicyclo[2.2.2]octane, DABCO), and a viologen-substituted polymer guest. Initial addition of DABCO to the porphyrin macrocycle in chloroform solution leads to the formation of a stable 2:1 (porphyrin:DABCO) dimeric complex, even under dilute conditions, by means of strong cooperative interactions involving hydrogen and metal-ligand bonds. Further titration of the porphyrin-DABCO mixtures with the polymer gives rise to a complex array of species in the solution. The system is analyzed in detail by a combination of spectroscopic measurements and computational modeling. Each association constant in the binding scheme and the fraction of each individual complex that is formed in solution are determined precisely using a mass-balance model. Kinetic studies revealed that the rates of the polymer threading and dethreading in and out of the dimeric system are remarkably slow, indicating that the polymer is locked inside the cavity of the stable 2:1 dimeric complex as a result of strong allosteric interactions

Host-guest complexes with tuneable solid state structures

Molecular clip receptors with long hydrocarbon tails self-assemble and form lamellar thin solid films, the architecture and properties of which can be fine-tuned by complexation of guest molecules

Lamellar organic thin films through self-assembly and molecular recognition

Molecular clips possessing U-shaped cavities have been functionalized on their convex side with long aliphatic tails. These molecules form dimers which self-assemble into malleable lamellar thin films. Upon addition of a guest (methyl 3,5-dihydroxybenzoate), a 1:1 host-guest complex is formed, which prohibits clip dimerization. As a result, the lamellar structure of the material is lost. Complexation of 3,5-dihydroxybenzoic acid in the clip results in host-guest complexes which dimerize by hydrogen bonding interactions between the carboxylic acid functions of the bound guests. This dimerization restores the lamellar type architecture of the material

NSC191771

Since the serendipitous event that led to the first synthesis of a molecule by the hands of Man in 1826, the creation of molecular matter depended for 150 years on linking together molecules from other molecular building blocks with the help of strong covalent bonds. The advent of supramolecular chemistry in the last decades of the 20th century has provided chemists with a wealth of new possibilities to synthesize molecular structures and materials that are held together by relatively weak, non-covalent interactions, such as hydrogen bonding, π-π stacking, electrostatic and van der Waals interactions. Using nature as a source of inspiration, the creation of even more complex supramolecular architectures has recently become possible by applying the concept of hierarchical self-assembly, i.e. the non-covalent organization of molecules and macromolecules which takes places over distinct multiple levels, in which the assembly processes gradually decrease in strength. This review will focus on some recent discoveries in the field of spontaneous hierarchical organization of synthetic amphiphiles, disk-like molecules and concave building blocks into well-defined nano-sized assemblies

Manganese porphyrin hosts as epoxidation catalysts - activity and stability control by axial ligand effects

The catalytic performance of a cavity-containing [(porphyrin)Mn] in the epoxidation of alkenes is described. Inside the catalyst cavity, nitrogen-containing axial ligands can be bound to the porphyrin metal with high association constants, resulting in strong activation of the catalyst in the presence of only one equivalent of the ligand. Complexation of a sterically demanding ligand to the outside of the cavity-containing catalyst can prevent catalyst decomposition through the formation of ν-oxo dimers

Templated self-assembly of porphyrin cages

The development of self-assembling catalysts, although an often-tried approach, has achieved little success so far. Toward the construction of substrate selective catalysts, we have self-assembled a porphyrin cage based upon the recognition of the templates meso-dipyndyl (DPyP) or meso-tetrapyridyl porphyrin (TPyP) by glycoluril-based receptors that are functionalized with two pendant zinc porphyrins