Color Responses of a Tripodal Colorimetric Sensor toward Anions

Multiple-Responsive Dendronized Hyperbranched Polymers

By combining topological structures of hyperbranched polymers with dendronized polymers, a series of hyperbranched poly(acylhydrazone)s pendanted with 3-fold branched dendritic oligoethylene glycol (OEG) units were efficiently prepared through A2 + B3 polycondensation. The constituents of these dendritic polymers can be mediated through dynamic covalent acylhydrazones. Owing to the dense OEG pendants, these dendronized hyperbranched polymers are biocompatible and thermoresponsive, and their cloud points (T cps) can be modulated by the branched architecture, solution pH, and addition of a third component. Cell viability in the presence of these hyperbranched poly(acylhydrazone)s can be maintained above 80%. Based on the unique dendritic architecture with rich acylhydrazine groups, dynamic hydrogels cross-linked via acylhydrazone linkages with good mechanical property were prepared, which inherit the characteristic thermoresponsive behavior of the polymer precursors and also show remarkable self-healing properties. This novel kind of topological polymers and their corresponding hydrogels with dynamic and multiple smart properties may have promising applications as biomaterials.

Tripod-type 2,2′-bipyridine ligand for lanthanide cations: synthesis and photophysical studies on coordination to transition metal cations

New tripod-type 2,2′-bipyridine ligand consisting of a central polyaminocarboxylic moiety for the coordination to lanthanide cations and three appended 5-phenyl-2,2′-bipyridine fragments for the coordination to various transition metal cations have been prepared. A europium complex of this ligand was prepared, and its photophysical properties and a luminescent response towards transition metal salts (particularly, CdI2, Cd(OAc)2, Zn(ClO4)2, Cu(OAc)2, and HgCl2) have been studied. Europium cation luminescence quenching in the presence of transition metal salts in solution was observed in all cases. In addition, it was observed that the fluorescent response of the europium complex was quite individual depending on the type of the metal salt. The obtained data were compared with the earlier published data for some lanthanide complexes bearing additional sites for the chelation of transition metal cations.

Spectroscopic, potentiometric and theoretical studies of novel imino-phenolate chelators for Fe(III)

The present study was targeted to explore the binding properties of two strong chelators for Fe(III) based on tripodal-iminophenolate moiety. Complexation behavior of the tripodal systems cis-cis cyclohexane-1,3,5-tricarboxylic acid tris-({2-[(2-hydroxy-benzylidene)-amino]-ethyl}-amide (CYCOENSAL, L(1)) and cis-cis cyclohexane-1,3,5-tricarboxylic acid tris-({3-[(2-hydroxy-benzylidene)-amino]-propyl}-amide (CYCOPNSAL, L(2)) is described. Three protonation constants obtained are assigned for three hydroxyl groups of aromatic ring were employed for the evaluation of the formation constants of the metal complexes. Both ligands liberate three protons each forming monomeric complexes of type FeLH3, FeLH2, FeLH and FeL (L=L(1) and L(2)). The first species FeLH3 depicted at low pH, where the ligands were coordinated through three imine nitrogen and other species form subsequently from FeLH3 in steps upon deprotonation and coordination of the phenolic oxygen giving encapsulated tris(phenolate) complexes. The probable structures of the metal complexes formed in solution were proposed through molecular modeling calculations. L(2) was observed to be highly selective towards Fe(III) as compared to L(1).