Pb(2)(2-) as Ligand in

Bimetallic Iridium(III) Complexes Consisting of Ir(ppy)2 Units (ppy = 2-Phenylpyridine) and Two Laterally Connected N∧N Chelates as Bridge: Synthesis, Separation, and Photophysical Properties

Reaction of the precursor complex Ir2(ppy)4Cl2 (ppy = 2-phenylpyridine) with the bridging ligand 3,8-dipyridyl-4,7-phenanthroline (L) affords, in 94% yield, the cyclometalated iridium dinuclear complex [(ppy)2Ir(mu-L)Ir(ppy)2]2+ (12+) as a mixture of three stereoisomers. This mixture consists of a meso form Delta,Lambda and a racemic form (enantiomeric pair Delta,Delta and Lambda,Lambda) in the ratio 1:1.5. Single-crystal X-ray characterization of the perchlorate salt of the meso form reveals (i) the distortion of the bridging ligand from the planarity and (ii) the location of the two iridium subunits above and below the medium plane of the bridging ligand. Ion-pair chromatography with Delta-TRISPHAT anion (TRISPHAT = tris(tetrachlorobenzenediolato)phosphate(V)) as resolving anion permits the separation of the three stereoisomers. The 1H NMR spectroscopic analysis of each fraction indicates high diastereomeric purity. Electronic circular dichroism properties and comparison with literature data establish their absolute configuration. The absorption and emission properties of the three stereoisomers show only very small variations. The anisotropic properties can be interpreted as distinct interactions of the isomers with the chiral resolving Delta-TRISPHAT anion.

Outer-Sphere Association of p-Sulfonatothiacalix[4]arene and Tetrasulfonatomethylated Calix[4]resorcinarene with Cobalt(III) Tris(dipyridyl): The Effect on the Spectral and Electrochemical Properties of the Latter

According to the 1H NMR and X-ray data, the outer-sphere association of [Co(dipy)3]3+ with cyclophanic anions p-sulfonatothiacalix[4]arene and tetrasulfonatomethylated calix[4]resorcinarene is accompanied by the inclusion of the dipyridyl moiety of the former into the cavities of the cyclophanic anions in aqueous and aqueous-DMSO solutions and in the solid state. The first-step dissociation of p-sulfonatothiacalix[4]arene does not change the inclusion mode, but the increase in DMSO content leads to a shallower inclusion of [Co(dipy)3]3+. The electrochemical property changes of [Co(dipy)3]3+ with both receptors undergoing ion pairing indicate the stabilization of the tris(dipyridyl) cobalt complexes in lower oxidation states. The effect of the cyclophanic anions on the cyclic voltammograms of [Co(dipy)3]3+ correlates with the efficiency of binding of the latter with tetrasulfonatomethylated calix[4]resorcinarene and p-sulfonatothiacalix[4]arene.