Sensitized near-infrared emission from ytterbium(III) via direct energy transfer from iridium(III) in a heterometallic neutral complex

A tetrametallic iridium-ytterbium complex has been synthesised that shows sensitized near-infrared emission (\u3bbmax = 976 nm) upon excitation of the iridium unit in the visible region (400 nm) due to efficient energy transfer from the iridium units to the Yb(iii) ion. The iridium phosphorescence is quenched nearly quantitatively while the ytterbium ion emits brightly in the NIR

Assembling photo- and electroresponsive molecules and nano-objects

The self-assembly of small molecules into large, functional nanostructures has led to the construction of supramolecular systems, both in solution and on solid substrates, with defined dimensions that display unique properties through collective interactions, much like natural systems. In this article, we show how one assembles photo- and electroluminescent molecules through coordination chemistry for the purpose of producing novel materials that can be used for displays and lighting applications. In a stepwise process, we discuss the design and synthesis of the components, their spectroscopic behavior, and finally the properties arising from the assembly. We then move from molecules to more complex systems such as zeolite L nano-objects that can be used as nanocontainers and functionalized in different ways. We show how it is possible to organize rods of micron length in a geometrically controlled manner in solution and on surfaces. The assemblies are built by coordinative bonds and are luminescent materials that can be constructed from fluorescent building blocks, with potential applications as optoelectronic materials, in analogy to their molecular counterparts

Highly luminescent, neutral, nine-coordinate lanthanide(III) complexes

Using a simple ligand design, we have prepared neutral, nine-coordinate lanthanide complexes that exclude water from the inner coordination sphere, thus leading to high emission quantum yields and long excited-state lifetimes. The complexes form in high synthetic yields (49-87%) by simply mixing the ligand and the lanthanide. Visible luminescence from EuIII (\u3a6 = 60 %, \u3c4 = 2.2 ms) and TbIII (\u3a6 = 7 %, \u3c4 = 0.2 ms) and near-infrared luminescence from YbIII (\u3a6 = 0.7%), NdIII and Er III were observed in acetonitrile and CH2Cl2 at room temperature. In addition, the GdIII complex was prepared to gain information about the triplet state of the ligand

Enantiopure, supramolecular helices containing three-dimensional tetranuclear lanthanide(III) arrays: Synthesis, structure, properties, and solvent-driven trinuclear/tetranuclear interconversion

The enantiomerically pure pinene-bipyridine-based receptor, (-) or (+) L-, diastereoselectively self-assembles in dry acetonitrile in the presence of LnIII ions (Ln = La, Pr, Nd, Sm, Eu, Gd, and Tb) to give a C3-symmetrical, pyramidal architecture with the general formula [Ln4(L)9(\u3bc3-OH)](ClO4) 2) (abbreviated as tetra-Ln4L9). Three metal centers shape the base: an equilateral triangle surrounded by two sets of helically wrapping ligands with opposite configurations. This part of the structure is very similar to the species [Ln3(L)6(\u3bc 3-OH)(H2O)3](ClO4)2) (recently reported by us and abbreviated as tris-LnL2) formed by the ligand and the Ln(III) ions when the reactions are performed in methanol. The tetranuclear structure is completed by a capping, helical unit LnL3 whose chirality is also predetermined by the chirality of the ligand. A complete characterization of these isostructural, chiral compounds was performed in solid state (X-ray, IR) and in solution (ES-MS, NMR, CD, UV-vis and emission spectroscopies). The sign and the intensity of the CD bands in the region of the \u3c0\u3c0* transitions of the bipyridine (absolute \u394 \u3b5 values at 327 nrn are about 280 M-1\ub7cm -1) are highly influenced by the helicity of the capping fragment LnL3. The photophysical properties (lifetime, quantum yield) of the visible (Eu and Tb complexes) and NIR (Nd complex) emitters indicate a good energy transfer between the ligands and the metal centers. The two related superstructures tetra-Ln4L9 and tris-LnL2 can be interconverted in acetonitrile, the switching process depending on the amount of water present in the solvent, the size of the Ln(III) ion, and the concentration. The weak chiral recognition capabilities of the self-assembly leading to the formation of tetra-Ln4L9 either by direct synthesis from a racemic mixture of the ligand and Ln(III) ions or by the conversion of a tris-Ln[(\ub1)-L]2 racemate were likewise demonstrated

Synthesis of oligoarylenevinylenes with fluorinated double bonds

Oligoarylenevinylenes with fluorine atoms in the vinylene units and side-chains with a range of polarities bonded to the aryl rings, have been synthesized via a methodology based on the Stille cross-coupling reaction. All compounds were stereoselectiveIy synthesized with trans double bonds

Dynamics of benzene molecules situated in metal-organic frameworks

In this paper, we investigate the gyroscopic motion of a benzene molecule C6H6, which comprises an inner carbon ring and an outer hydrogen ring, and is suspended rigidly inside a metal-organic framework. The metal-organic framework provides a sterically unhindered environment and an electronic barrier for the benzene molecule. We model such gyroscopic motion from the inter-molecular interactions between the benzene ring and the metal-organic framework by both the Columbic force and the van der Waals force. We also capture additional molecular interactions, for example due to sterical compensations arising from the carboxylate ligands between the benzene molecule and the framework, by incorporating an extra empirical energy into the total molecular energy. To obtain a continuous approximation to the total energy of such a complicated atomic system, we assume that the atoms of the metal-organic framework can be smeared over the surface of a cylinder, while those for the benzene molecule are smeared over the contour line of the molecule. We then approximate the pairwise molecular energy between the molecules by performing line and surface integrals. We firstly investigate the freely suspended benzene molecule inside the framework and find that our theoretical results admit a two-fold flipping, with the possible maximum rotational frequency reaching the terahertz regime, and gigahertz frequencies at room temperature. We also show that the electrostatic interaction and the thermal energy dominate the gyroscopic motion of the benzene molecule, and we deduce that the extra energy term could possibly reduce the rotational frequency of the rigidly suspended benzene molecule from gigahertz to megahertz frequencies at room temperature, and even lower frequencies might be obtained when the strength of these interactions increases.Yue Chan, James M. Hil