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

Abstract

A studied tert-butylthiacalix[4]arene derivative with four N-(2-acetoxyethyl)carbamoylmethoxy substituents on its lower rim in partial-cone configuration (calixarene 1) can remember its previous treatment in three essentially different ways by the formation either of a molecular glass or two metastable polymorphs after heating or the removal of an included guest molecule. Guest-induced memory is very selective with a polymorph created only after the release of a few included guests among a large series of those studied and is detected via an exothermic transition. Along with ordinary properties, like glass transition, curing and cold crystallization, the molecular glass from 1 is selective due to its ability to crystallize in solvent vapors and vapor mixtures over a well-defined concentration range. Being cooperative, this property may be used for the visual detection of ethanol content in water solution when it reaches a threshold value.

Interaction of l-alanyl-l-valine and l-valyl-l-alanine with organic vapors: thermal stability of clathrates, sorption capacity and the change in the morphology of dipeptide films

“…Thermoanalysis by simultaneous TG/DSC/MS Simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC) analysis of dipeptide powder with mass spectrometric (MS) evolved gas analysis were performed using a thermoanalyzer STA 449 C Jupiter (Netzsch) coupled with a quadrupolar mass-spectrometer QMS 403C Aeolos (Netzsch) as described elsewhere. 41,43 In each experiment, the temperature rate was 10 K min À1 , and an argon atmosphere with a total flow rate of 75 ml min À1 was used. For this experiment, 5-7 mg samples of guest-free dipeptides were placed in aluminum crucibles (40 ml) with lids having 3 holes, each of 0.5 mm in diameter.…”

Liquid Silyl Derivative of beta-Cyclodextrin

“…Obtained values are rather high, being several times more than ΔC p obtained earlier for a glass transition in calixarenes. [20,21] Exposure of liquid 1 to the vapors of methanol, ethanol, 1-propanol, acetonitrile, benzene and toluene results in a quick formation of solution, so, 1 can be mixed with these solvents in any proportion. For comparison, Liquid Silyl Derivative of beta-Cyclodextrin 5c,d, which are absent in diffractograms of crystals grown from the studied hydrophilic solvents.…”

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

“…The activation of this process with guest vapors may be selective. Such selectivity was observed visually for a compact glass of calixarene (Gataullina et al, 2015(Gataullina et al, , 2017 and using an atomic force microscopy for thin amorphous films of dipeptides (Ziganshin et al, 2015). Amorphous dipeptides may have three options in contact with guest vapors depending on the guest molecular structure: (1) crystallization, (2) gel formation, (3) intact host morphology (Ziganshin et al, 2017).…”

“…The mixture should have the concentration of this guest above a certain threshold value for this crystallization to be apparent, Figure 1B. For example, glassy tert-butylthiacalix[4]arene derivative crystallizes in contact with vapors of the aqueous solution of ethanol if its concentration is above 24 vol.% (Gataullina et al, 2015). The glass of the same calixarene in another conformation allows detecting 1% vol.…”

“…A corresponding screening technique involves preparing the inclusion compound and removing the included guest (Lee et al, 2013;Gataullina et al, 2017). This is a smart process, where the host may remember molecular structure of a released guest by formation of a specific metastable polymorph (Gataullina et al, 2015).…”