Syntheses of ester and amide derivatives of calix[6]arene and their complexation affinities towards La<sup>3+</sup>, Eu<sup>3+</sup>, and Yb<sup>3+</sup> Marina Tranfić Bakić David Klarić Maria Soledad Espinosa Saša Kazazić Leo Frkanec Paola Alejandra Babay Nives Galić 10.6084/m9.figshare.9209585.v1 https://tandf.figshare.com/articles/figure/Syntheses_of_ester_and_amide_derivatives_of_calix_6_arene_and_their_complexation_affinities_towards_La_sup_3_sup_Eu_sup_3_sup_and_Yb_sup_3_sup_/9209585 <p>One hexaester (<b>1</b>) and three hexaamide derivatives (<b>2</b>–<b>4</b>) of calix[6]arenes were prepared for the first time in one synthetic step, under microwave radiation. Compounds <b>2</b> and <b>3</b> were novel ones, while ester calix[6]arene derivative <b>1</b> and amide derivative <b>4</b> were prepared previously, by conventional syntheses. Microwave-assisted syntheses shortened the reaction times from 48 to 2 h. The binding properties of calix[6]arenes towards selected lanthanide cations (La<sup>3+</sup>, Eu<sup>3+</sup>, Yb<sup>3+</sup>) were studied by spectroscopic and mass spectrometric techniques. No complexation was observed with the ester derivative, while compounds <b>2</b>–<b>4</b> formed 1:1 complexes. Based on spectrophotometric titrations, the stability constants of resulting complexes could only be estimated (lg <i>K</i> ≥ 6). Calixarene derivatives, as well as their complexes, were analysed by ESI MS and MS/MS spectrometry. Corresponding fragmentation pathways were proposed, and in some cases confirmed by MS<sup>3</sup> experiments. The results obtained by different techniques were in accordance.</p> 2019-08-02 03:09:47 calix[6]arene lanthanides complexation UV spectroscopy mass spectrometry (MS)