Triazole-Linked Anthracenyl-Appended Calix[4]arene Conjugate As Receptor for Co(II): Synthesis, Spectroscopy, Microscopy, and Computational Studies

A new triazole-linked anthracenyl-appended calix[4]arene-1,3-diconjugate (L) has been synthesized and characterized, and its single crystal XRD structure has been established. Binding properties of L toward different biologically relevant metal ions have been studied by fluorescence and absorption spectroscopy in ethanol. L exhibits selective recognition of Co2+ and can detect down to a concentration of 55 ppb (0.92 mu M). The roles of the calix[4]arene platform as well as the preorganized binding core in L's selective recognition have been demonstrated by studying appropriate control molecules. The mode of binding of L with Co2+ has been modeled both by DFT and MD computational calculations. L and its Co2+ complex could be differentiated on the basis of the nanostructural features observed in AFM and TEM

A dinuclear bis(bipyridine)ruthenium(II) complex, [(bpy)2Ru(II){L2-}Ru-II(bpy)(2)](2+), incorporating an unusual non-innocent bridging ligand containing a p-benzoquinonediimine fragment: synthesis, structure, redox, and UV/VIS/NIR and EPR spectroelectrochemical properties

The reaction of [Ru(bpy)(2)(EtOH)(2)](2+) (bpy = 2,2'-bipyridine) with the symmetrical binucleating phenolatodiimine ligand HOC6H4N=CHC6H4CH=NC6H4OH (H2L1) in ethanol under dinitrogen results in the unexpected formation of the diruthenium complex [(bpy)(2)Ru-II{OC6H4N=C6H3(=NH)O}Ru-II(bpy)(2)](ClO4)(2) 1. In this complex, the bridging ligand (L-sq,L-sq)(2-) contains two inequivalent o-iminophenolate N,O-chelating binding sites, each formally at the semiquinone oxidation level, linked such that there is a p-benzoquinonediimine bridge between the two Ru centres. The crystal structures of H2L1 and of 1 have been determined. Complex 1 is electrochemically active and undergoes two reversible oxidations and two reversible reductions which, on the basis of UV/VIS/NIR and EPR spectroelectrochemical evidence, comparison with related systems and consideration of the redox potentials, we assign as centred on the bridging ligand. The two oxidations (at +0.12 and +0.35 V versus SCE) result in formation of a neutral, fully quinonoidal bridging ligand L-q,L-q; in the 'mixed-valence' mono-oxidised state, a near-IR transition (1570 nm) is ascribed to an intra-ligand charge transfer from the non-oxidised (semiquinone-like) to the oxidised (quinone-like) terminus. The two reductions (at -0.98 and -1.38 V versus SCE) are localised on the central p-benzoquinonediimine unit of the bridging ligand, affording the p-benzosemiquinone radical and then a p-diamide unit. In addition, at more extreme potentials, two oxidations at +1.49 and +1.70 V versus SCE are ascribed to Ru(II)/Ru(III) couples, and the reduction at -1.81 V versus SCE is bpy-based

Twenty-Five Years’ History, Mechanism, and Generality of Preferential Enrichment as a Complexity Phenomenon

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