This review highlights solvent systems that were designed to simultaneously address reaction, separation and recycling challenges.

We have synthesized a series of ethynylated phenazines and their bis-triazolyl cycloadducts to serve as metal ion sensors. Binding of metal ions is achieved through coordination to the phenazine nitrogen atom and the triazole ring. To allow metal sensing in aqueous solution, the triazole units are substituted with water-soluble ethylene glycol chains. These phenazine cycloadducts exhibit a selective affinity for binding silver ions. Examination of the halogenated analogues reveals a lowering of the band gap and the corresponding bathochromic shifts in the absorption and emission spectra. The electron-withdrawing properties of these halogens also result in significantly decreased metal-binding activity of the phenazine cycloadducts.

Polymers containing conjugated oligo(phenylene) segments of defined length alternating with solubilizing regions of di-to hexa(ethylene glycol) have been synthesized using a Suzuki coupling protocol. Soluble and characterizable materials with up to four benzene rings linked together have been formed without the inclusion of conjugation-disrupting solubilizing side chains. The polymers were generated with weight-averaged molecular weights as high as 158 000 g/mol as determined by GPC-LS. The thermal and luminescence properties of these materials were studied in order to determine how these properties varied with the lengths of the two types of blocks. While the terphenyl polymers were amorphous, the quaterphenyl polymers exhibited multiple transitions in their DSC thermatograms. Polarized light microscopy and X-ray diffractometry were used to investigate this behavior. All of the polymers fluoresced strongly in the blue region of the visible spectrum with a 40 nm red shift in emission between solution and solid-state spectra. UV-visible and fluorescence studies were performed at different concentrations and in solvent/nonsolvent mixtures in order to study possible causes for this spectral shift, which appears to be due to the presence of ground state aggregates.