Towards a Generalized Synthetic Strategy for Variable Sized Enantiopure M4L4 Helicates

Abstract

<jats:p>The reliable and predictable synthesis of enantiopure coordination cages is an important step towards the realization of discrete cages capable of enantioselective discrimination. We have built upon our initial report of a lantern-type helical cage in attempts to expand the synthesis into a general approach. The use of a longer, flexible diacid ligand results in the anticipated cage [Cu4(L1)4(solvent)4] with a similar helical pitch to that previously observed and a cavity approximately 30% larger. Using a shorter, more rigid ligand gave rise to a strained, conjoined cage-type complex when using DABCO as an internal bridging ligand, [{Co4(L2)4(DABCO)(OH2)x}2 (DABCO)]. The expected paddlewheel motif only forms for one of the Co2 units within each cage, with the other end adopting a “partial paddlewheel” with aqua ligands completing the coordination sphere of the externally facing metal ion. The generic approach of using chiral diacids to construct lantern-type cages is partially borne out, with it being apparent that flexibility in the core group is an essential structural feature.</jats:p>

Enantioselective chiral sorption of 1-phenylethanol by homochiral 1D coordination polymers

“…H 2 AlaPmDI and bix were synthesised using literature procedures. 10,35 FTIR spectra were obtained on an Agilent Cary 630 diamond attenuated total reflection (ATR) spectrometer, using Micro-Lab software to process the data. Thermogravimetric analyses were conducted using a Mettler Toledo TGA/DSC1 STARe system.…”

“…We have reported the dicarboxylate ligand AlaPmDI 2− as part of a discrete 'dumbbell-like' complex when used alongside DABCO. 35 In combination with the longer bis-nitrogen donor atom ligand 1,4-bis(imidazol-1-ylmethyl)benzene (bix), we instead drive the formation of polymeric structures that form as homochiral materials due to the stereocentres within the AlaPmDI 2− ligand. Coordination polymers formed using H 2 AlaPmDI have previously been formed, 46,47 and a 3D framework containing AlaPmDI 2− and Zn II has been able to separate benzene and cyclohexane based on aromatic interactions.…”

Supramolecular Chemistry in the 3rd Millennium

“…Supramolecular interactions play a vital role in the assembly of molecular helicates, and it is therefore fitting that this area of chemistry is represented in this themed issue -the assembly of enantiopure M 4 L 4 helicates is described in a study from Turner and coworkers [11]. Moving from multinuclear helicates to coordination polymers takes us on to contributions that describe supramolecular assemblies containing trinuclear copper(II)pyrazolato units (Raptis, Boudalis, Herchel and coworkers) [12] and chloro-substituted pyrazin-2-aminocopper(I) assemblies featuring hydrogen bond and halogen bond interactions (Mailman, Rissanen and coworkers) [13].…”