Analysis of guest binary mixtures by tert-butylcalix[6]arene using host memory of previously bound guests

Abstract

A new principle of quantitative and qualitative analysis of binary organic mixtures is offered, which is based on an ability of calixarene receptor for specific polymorphic transitions related to the composition of the analyzed guest mixture. The ability of tert-butylcalix[6]arene to remember selectively some guests bound from headspace both of pure liquids and their binary mixtures is used. The image of guest mixture remains written in metastable polymorphs of host after partial or complete guest elimination from clathrates. The memory was read using differential scanning calorimetry as the enthalpy of exothermic polymorphic transition of host collapse. This enthalpy monotonously changes with the variation of guests' ratio in mixture, unlike the enthalpies of endothermic pseudopolymorphic transitions of guest release. So, the composition of volatile binary mixture can be estimated using only one receptor and only one its parameter even in absence of preferential binding from a binary mixture of guests. This is an example of a genuine molecular recognition.

Smart Molecular Recognition: From Key-to-Lock Principle to Memory-Based Selectivity

“…tert-Butylcalix[5]arene with such structure of inclusion compounds has a very irregular relationship between S and MR D values (Ziganshin et al, 2007). The same was observed for diol host (Gorbatchuk et al, 2000), adamantylcalix[4]arene (Yakimova et al, 2008), and tert-butylcalix[6]arene (Safina et al, 2013).…”

“…This selectivity of tertbutylcalix[6]arene may be used in the analysis of binary mixtures if at least one of their components is from the first group. The efficiency of this analysis was demonstrated using DSC for the binary mixtures with one (Safina et al, 2013) and two (Gabdulkhaev et al, 2016) remembered components.…”

Twice as smart behavior of tert-butylthiacalix[4]arene derivative in glassy and crystalline form

“…This XRPD pattern is different from those of the initial 1Á1.1CH 3 CN obtained from 1g (Fig. 24,26,27 The observed potential polymorphism of calixarene 1 has a strong influence on the shape of the TG and MS curves of guest elimination from its clathrates ( Fig. 7a).…”

“…As well as the glass state keeping a memory of previous thermal treatment, heating some calixarenes 22,23 or their clathrates 24-27 may yield guest-free crystalline polymorphs, which remember their thermal history or previously bound guest, respectively. 24 This specific phase behavior was studied in the present work for 1 in its initial glassy 1g and crystalline 1a forms. [24][25][26][27] For clathrates, the presence of this effect and its temperature and enthalpy may strongly depend on the structure of the guest 24,27 and may be used for molecular recognition of guests in the pure state 24,26,27 and in mixtures.…”

“…1 The ability of calixarenes to form glass may have common structural causes with another smart property of these compounds. [24][25][26][27] For clathrates, the presence of this effect and its temperature and enthalpy may strongly depend on the structure of the guest 24,27 and may be used for molecular recognition of guests in the pure state 24,26,27 and in mixtures. This host memory of a guest can be observed in a DSC experiment as an exothermic transition, without loss of mass, to a stable form.…”