Can enantiomer ligands produce structurally distinct homochiral MOFs?

Abstract

Here, we report a self-assembled homochiral metal-organic framework [Cu1.5(H2Ll-leu)(Ac)H2O]n·3H2O (1) obtained from an l-leucine-derived ligand (H4Ll-leu) and Cu(Ac)2·H2O in a 1 : 1 ratio. Coordination-induced conformational change in the ligand has been monitored by circular dichroism which has been further attested by synthesizing a d-leucine-containing enantiomer H4Ld-leu and its Cu(ii) complex [Cu1.5(H2Ld-leu)H2O]n·10H2O (2). Structure determination revealed entirely different structures for the homochiral MOFs (1 and 2) obtained from the l/d-leucine-derived enantiomer ligands under analogous reaction conditions. Further, structural dissimilarity in these MOFs has been judicially supported by proton conductance studies. MOF 1 shows higher proton (10-5 S cm-1) conductance in comparison to 2 (10-6 S cm-1) due to dissimilar alignment of the hydrogen-bonded water molecules in the hydrophilic pocket as well as crystal packing. © The Royal Society of Chemistry.