Effect of the Structure of Amido Esters and Amido Hydrazides of Imidazole-4,5-Dicarboxylic Acid on their Luminescent Properties

Theoretical and Experimental Chemistry - It was established that unsubstituted amides of imidazole-4,5-dicarboxylic acid are characterized by large (up to 15000 cm–1) Stokes shifts. It was...     

p-tert-butylcalix[4]arenes containing azacrown ether substituents at the lower rim as potential polytopic receptors

A series of disubstituted p-tert-butylcalix[4]arenes with N-methoxycarbonylmonoazacrown ether and N-ethoxymonoazacrown ether residues at the lower rim has been prepared via the reaction of di(carboxymethoxy)-p-tert-butylcalix[4]arene with azacrown ethers and subsequent reduction of the resulting amide derivatives. Using UV titration and ¹H NMR spectroscopy we have demonstrated the ability of the calixarene with two N-carbonylmonoaza-18-crown-6-ether substituents to form the 1:3 complexes with K⁺ and Na⁺ and the 1:2 complexes with Cs⁺, Sr²⁺, Cu²⁺, and Zn²⁺. The calixarene with two fragments of N-ethoxymonoazo-18-crown ether has formed binuclear complexes with alkali metals cations and mononuclear complexes with transition metals cations.     

Luminescent sol–gel materials based on lanthanide aminopolycarboxylates (Ln = Nd, Eu, Tb, Yb)

Luminescent organic–inorganic hybrid materials containing immobilized lanthanide(III) complexes (Ln = Nd, Eu, Tb, Yb) with modified ethylenediaminetetraacetic and diethylenetriaminepentaacetic acid were synthesized by sol–gel method. Obtained hybrids exhibit 4f-luminescence in the visible (Eu(III) and Tb(III)) and IR-region (Nd(III) and Yb(III)). The influence of the hybrid matrix on the lanthanide luminescence was established and it was shown, that the location of resonance level of Eu(III) is optimal for efficient energy transfer from matrix, while in the case of Tb(III) energy transfer does not occur and Tb(III) is able to absorb energy only due to its own week f–f transitions. It was also established that the inorganic matrix leads to elimination of nonradiative energy losses and increase of 4f-luminescence lifetimes. Covalent binding of Ln(III) aminopolycarboxylates in the matrix allows to consider obtained materials as promising for creation of photo- and chemically-stable luminescent sensors.