Energy transfer between amphiphilic porphyrin polymer shells and upconverting nanoparticle cores in water-dispersible nano-assemblies.

The synthesis of water-dispersible nano-assemblies containing upconverting nanoparticles (UCNPs) and porphyrin molecules using a one-pot method is described. When the nano-assemblies are excited by 980 nm near-infrared light, the intensity of the 'green emission' band of the UCNP is reduced due to a combination of Föster Resonace Energy Transfer (FRET) and emission-reabsorption. This process is also responsible for the emission from the porphyrin chromophores despite the fact they do not absorb near-infrared light.

Rigid, cross-conjugated macrocycles: a cyclic alternative to 4,4'-bipyridines in supramolecular chemistry.

[structure: see text]. The synthesis of two fully conjugated, rigid macrocyclic analogues to 4,4'-bipyridine is described. The use of these macrocycles in self-assembly processes is demonstrated by axial coordination to metalloporphyrins, and one system (R = Me) has been characterized by single-crystal X-ray crystallography.

A remarkably stable hydrogen-bonded porphyrin.iron(terpyridine) ion pair.

Even in highly competitive solvents such as DMSO, strong bimolecular association and subsequent fluorescence quenching result from the combination of hydrogen bonding and ion pairing between a porphyrinic bis(carboxylate) dianion and an iron(terpyridine) bis(urea).

Novel synthesis of photochromic polymers via ROMP.

[reaction: see text] Ring-opening metathesis polymerization (ROMP) of a photochromic 1, 2-bis(3-thienyl)cyclopentene monomer generated a series of novel polymers. All polymers exhibit reversible light-activated interconversion between their colorless-open and their colored-closed forms.

Reversible encapsulation of disc-shaped guests by a synthetic, self-assembled host.

Here, the synthesis of a bowl-shaped molecule is described and evidence of its reversible dimerization by means of hydrogen bonds is presented. The dimer features a flattened spherical cavity of peculiar symmetry and acts as a host for the encapsulation of guest molecules of complementary shape. Encapsulation of aromatic guests in chloroform solution and of cyclohexane in p-xylene solution was demonstrated by nuclear magnetic resonance experiments. The passage of guests into and out of the cavity is slow and occurs on a time scale of hours. The system was used to explore the effects of size, shape, and solvation on molecular recognition coupled with assembly.

Encapsulation of methane and other small molecules in a self-assembling superstructure.

Physical inclusion of small molecules in larger structural lattices is well known in the crystalline state and is a common feature of the chemistry of zeolites. In the liquid state, a variety of synthetic macrocyclic molecules are available to complex and contain smaller guest species. An alternative strategy for binding is explored: assembly of cavity-forming structures from small subunits. Encapsulation of small guest molecules such as methane can be achieved with a synthetic structure that assembles reversibly through hydrogen bonding.