Russian Nesting Doll Complexes of Molecular Baskets and Zinc Containing TPA Ligands

Abstract

In this study, we examined the structural and electronic complementarities of convex 1-Zn(II), comprising functionalized tris(2-pyridylmethyl)amine (TPA) ligand, and concave baskets 2 and 3, having glycine and (S)-alanine amino acids at the rim. With the assistance of (1)H NMR spectroscopy and mass spectrometry, we found that basket 2 would entrap 1-Zn(II) in water to give equimolar 1-Zn⊂2in complex (K = (2.0 ± 0.2) × 10(3) M(-1)) resembling Russian nesting dolls. Moreover, C3 symmetric and enantiopure basket 3, containing (S)-alanine groups at the rim, was found to transfer its static chirality to entrapped 1-Zn(II) and, via intermolecular ionic contacts, twist the ligand's pyridine rings into a left-handed (M) propeller (circular dichroism spectroscopy). With molecular baskets embodying the second coordination sphere about metal-containing TPAs, the here described findings should be useful for extending the catalytic function and chiral discrimination capability of TPAs.

Chirality transfer in a cage controls the clockwise/anticlockwise propeller arrangement of the tris(2-pyridylmethyl)amine ligand

“…Compared to (M)-1, the metallated (M)-Cu I (1)(Cl) displayed a positive ECD couplet at 260 nm characteristic of the electronic p-p* transition of the TPA-metal chromophore. 7,16 Along with XRD and 1 H-NMR studies, the ECD analysis therefore confirms that the transfer of chirality from the CTV unit to the (TPA)Cu I (Cl) core occurs in both solid state and solution.…”

“…More recently, Badjić and coworkers reported an elegant strategy based on the supramolecular functionalization of a cationic TPA derivative with an anionic C 3 symmetrical concave basket. 7 The static chirality of the basket results in the exclusive formation of a left-handed Zn-TPA supramolecular complex via intermolecular ionic contact. Furthermore, very lately, a length-dependent inversion of the TPA helicity upon guest-binding in a supramolecular cage has been described.…”

On the encapsulation and assembly of anticancer drugs in a cooperative fashion

“…30 After basket 1 was dissolved in 10 mM phosphate buffer (PBS) at pH = 7.0, its 1 H NMR spectrum showed a set of five, somewhat broad, resonances corresponding to, on average, D 3h symmetric 1 6– (Fig. 2A); note that for six remote carboxylates, we assumed p K a < 5 31. In line with 1 H NMR results, the Monte-Carlo conformational sampling of 1 6– , in implicit water solvent (OPLS3e, Maestro), revealed numerous conformers (Fig.…”

Control and Transfer of Chirality Within Well-Defined Tripodal Supramolecular Cages

“…Another remarkable strategy to generate and control chirality on an achiral tripodal ligand consists in its non-covalent wrapping with a chiral concave open-cage structure, through intermolecular ionic contacts. This so-called “Russian nesting doll” approach have been reported in 2016 by Badjic et al which used the chiral molecular baskets developed in their team to create and control a propeller-like arrangement of a TPA-based Zinc complex (Zhiquan et al, 2016 ). The self-assembled architecture Zn II (9)(Cl) is based on supramolecular ionic interactions between a zinc complex substituted with three positively charged ammonium groups Zn II (TPA NH3 )Cl , and the chiral molecular nest 8 (displaying three negatively charged carboxylates at its rim) ( Figure 2C ).…”