A pair of 3D enantiotopic zinc(ii) complexes based on two asymmetric achiral ligands

Abstract

Enantiomorphism and enantioselectivity are critical in biology and many other applications. Herein, we report two 3D chiral MOFs {[Zn₆(MIDPPA)₃(1,2,4-btc)₃(NO₂)₃(H₂O)₃](H₂O)₇}_n (1L and 1R) based on achiral ligands with high enantiomeric excess and a novel topological type. The internal mechanism of spontaneous chiral symmetry breaking, during the crystallization of chiral MOFs based on achiral ligands, is elucidated for the first time from both structural and theoretical aspects. Hydrogen bonds are found to play a key role in the spontaneous symmetry breaking of chiral MOFs. Also, DFT calculations support our findings from the aspects of total energies and HOMO–LUMO energy gaps. Both 1L and 1R, exhibiting green fluorescence, present a non-centrosymmetric polar packing arrangement, resulting in good ferroelectric behaviors and second-order nonlinear optical effects.