Are the Physical Properties of Xe@Cryptophane Complexes Easily Predictable? The Case of syn- and anti-Tris-aza-Cryptophanes

Abstract

We report the synthesis and the optical resolution of C3-symmetrical tris-azacryptophanes anti-3 and syn-4, as well as the study of their interaction with xenon via hyperpolarized 129 Xe NMR. These molecular cages are close structural analogs of the two wellknown cryptophane-A (1; chiral) and cryptophane-B (2; achiral) diastereomers since these new compounds differ only by the presence of three nitrogen atoms grafted on the same cyclotribenzylene unit. The assignment of their relative (syn vs anti) and absolute configurations was made possible thanks to the combined use of quantum calculation at the DFT level and vibrational circular dichroism (VCD). More importantly, our results show that despite the large structural similarities with cryptophane-A (1) and -B (2), these two new compounds show very different behavior in the presence of xenon in organic solution. These results demonstrate that a prediction of the physical properties of the xenon@cryptophane complexes, only based on structural parameters, remains extremely difficult.

Access to the Syn diastereomers of cryptophane cages using HFIP

“…1,3 Most cryptophanes can be obtained under two diastereomeric forms ( syn and anti ), 1,4 that display different physicochemical properties and complexation affinity of selected guests. 5–10…”

“…In contrary, the use of Sc(OTf) 3 in an equimolar amount was found to provide, under mild conditions, good yields and more convenient purification steps for the synthesis of a wide range of syn and anti -cryptophanes. 1,4–11 Nevertheless the access to syn isomers bearing ethylenedioxy linkers remains highly challenging. Whereas anti -cryptophane A (Fig.…”

syn-Cryptophanes: macrocyclic compounds with optimized characteristics for the design of 129Xe NMR-based biosensors

“…The synthetical pathway for cryptophane 2 and its characterization as well as this of the intermediates is given in ESI (S1-S11). Unlike other syncryptophanes (except for those containing nitrogen groups on the linkers or as aromatic substituents 23,24 ), xenon in the presence of compound 2 exhibits a slow exchange situation at 11.7 T and room temperature, i.e. the xenon exchange in and 13 C spectra of the intermediates, HSQC, HMBC of 2, 129 Xe spectra of compounds 1 and 3, 1 H spectra comparing 1 and 2, 1 and 3 in different experimental conditions, pulse sequence to measure the depolarization rate, simulation of the effect of the rf pulse].…”

Study of syn and anti Xenon-Cryptophanes Complexes Decorated with Aromatic Amine Groups: Chemical Platforms for Accessing New Cryptophanes

“…To do so, different parameters that have been summarized in a recent article have to be taken into account. 4 We recently reported the synthesis of compounds 1 and 2 with a low yield. 4 Compounds 1 and 2 are close analogs to cryptophanes A (3) and B (4), respectively.…”

“…4 We recently reported the synthesis of compounds 1 and 2 with a low yield. 4 Compounds 1 and 2 are close analogs to cryptophanes A (3) and B (4), respectively. 5,6 These compounds differed only by the replacement of three oxygens of the alkoxy linkers in compounds 3 and 4 by three nitrogen atoms (see Chart 1).…”