Duplex-selective ruthenium-based DNA intercalators.

We report the design and synthesis of small molecules that exhibit enhanced luminescence in the presence of duplex rather than single-stranded DNA. The local environment presented by a well-known [Ru(dipyrido[3,2-a:2',3'-c]phenazine)L2 ](2+) -based DNA intercalator was modified by functionalizing the bipyridine ligands with esters and carboxylic acids. By systematically varying the number and charge of the pendant groups, it was determined that decreasing the electrostatic interaction between the intercalator and the anionic DNA backbone reduced single-strand interactions and translated to better duplex specificity. In studying this class of complexes, a single Ru(II) complex emerged that selectively luminesces in the presence of duplex DNA with little to no background from interacting with single-stranded DNA. This complex shows promise as a new dye capable of selectively staining double- versus single-stranded DNA in gel electrophoresis, which cannot be done with conventional SYBR dyes.

Stabilization of a highly porous metal-organic framework utilizing a carborane-based linker.

The first tritopic carborane-based linker, H3BCA (C15B24O6H30), based on closo-1,10-C2B8H10, has been synthesized and incorporated into a metal-organic framework (MOF), NU-700 (Cu3(BCA)2). In contrast to the analogous MOF-143, NU-700 can be activated with retention of porosity, yielding a BET surface area of 1870 m(2) g(-1).

An exceptionally high boron content supramolecular cuboctahedron.

A boron-rich supramolecular cuboctahedron containing an impressive 240 boron atoms has been synthesized via coordination-driven assembly. The cuboctahedron, which is composed of Cu(2+) paddle-wheel nodes and carborane-isophthalic acids, was obtained simply and in high purity. The ability to precisely characterize the nanostructure via X-ray diffraction makes it unique among boron-rich nanostructures.

A coordination chemistry dichotomy for icosahedral carborane-based ligands.

Although the majority of ligands in modern chemistry take advantage of carbon-based substituent effects to tune the sterics and electronics of coordinating moieties, we describe here how icosahedral carboranes-boron-rich clusters-can influence metal-ligand interactions. Using a series of phosphine-thioether chelating ligands featuring meta- or ortho-carboranes grafted on the sulfur atom, we were able to tune the lability of the platinum-sulfur interaction of platinum(II)-thioether complexes. Experimental observations, supported by computational work, show that icosahedral carboranes can act either as strong electron-withdrawing ligands or electron-donating moieties (similar to aryl- or alkyl-based groups, respectively), depending on which atom of the carborane cage is attached to the thioether moiety. These and similar results with carborane-selenol derivatives suggest that, in contrast to carbon-based ligands, icosahedral carboranes exhibit a significant dichotomy in their coordination chemistry, and can be used as a versatile class of electronically tunable building blocks for various ligand platforms.