Blue-fluorescent molecular nanocapsules created by simple mixing 'green-environmentally friendly' metal ions and bent organic blocks

ScienceDaily (July 12, 2012) ? New fluorescent molecular nanocapsules have potential applications as sensors, displays, and drug delivery systems (DDS).

Michito Yoshizawa, Zhiou Li, and collaborators at Tokyo Institute of Technology (Tokyo Tech) synthesized ~1 nanometer-sized molecular capsules with an isolated cavity using green and inexpensive zinc and copper ions. In sharp contrast to previous molecular capsules and cages composed of precious metal ions such as palladium and platinum, these nanocapsules emit blue fluorescence with 80% efficiency.

Molecular nanocapsules have potential applications as photo-functional compounds and materials but so far molecular capsules synthesized by incorporating palladium ions and so on exhibit poor fluorescence.

The Tokyo Tech researchers expect to be able to prepare multicolor fluorescence composites by the simple insertion of appropriate fluorescent molecules into the isolated cavity of the nanocapsules.

Fluorescence has widespread applications, helping researchers to understand issues in the fundamental sciences and develop practical materials and devices. Among the useful fluorescent compounds in development, capsule-shaped molecular architectures, which possess both strong fluorescent properties and a nanometer-sized cavity, are particularly promising.

Molecular cages and capsules can be prepared through a simple synthetic process called coordinative self-assembly. However, most of them are composed of precious metal ions such as palladium and platinum, and are non-emissive due to quenching by the heavy metals.

Now, Michito Yoshizawa, Zhiou Li, and co-workers from the Chemical Resources Laboratory at Tokyo Institute of Technology report novel molecular nanocapsules with the M2L4 composition (where M represents zinc, copper, platinum, palladium, nickel, cobalt, and manganese). Their zinc and copper capsules, in particular, display unique fluorescent properties.

The M2L4 capsules self-assemble from two metal ions and four bent ligands that include anthracene fluorophores (fluorescent parts). X-ray crystallographic analysis verified the closed shell structures where the large interior cavities of the capsules, around one nanometer in diameter, are shielded by eight anthracene panels.

The zinc capsule emitted strong blue fluorescence with a high quantum yield (80%), in sharp contrast to the weakly emissive nickel and manganese capsules and the non-emissive palladium, platinum, and cobalt capsules. The fluorescence of the copper capsule, on the other hand, depends on the solvent; for example, it shows blue emission in dimethyl sulfoxide but no emission in acetonitrile.

This study is the first to show such emissive properties of molecular capsules bearing an isolated large cavity. The researchers believe their nanocapsules could have novel applications in devices such as chemosensors, biological probes, and light-emitting diodes.

Share this story on Facebook, Twitter, and Google:

Other social bookmarking and sharing tools:

---

Story Source:

The above story is reprinted from materials provided by Tokyo Institute of Technology, via ResearchSEA.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Journal Reference:

1. Zhiou Li, Norifumi Kishi, Kenji Yoza, Munetaka Akita, Michito Yoshizawa. Isostructural M2L4 Molecular Capsules with Anthracene Shells: Synthesis, Crystal Structures, and Fluorescent Properties. Chemistry - A European Journal, 2012; 18 (27): 8358 DOI: 10.1002/chem.201200155

Note: If no author is given, the source is cited instead.

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

Source: http://www.sciencedaily.com/releases/2012/07/120712111634.htm

robert kennedy san diego weather north korea frances bean cobain north korea missile launch modesto detroit tigers