Role of the Auxiliary Ligand in the Spontaneous Resolution of Enantiomers in Three-Dimensional Coordination Polymers

Four pairs of chiral 3D coordination polymers (CPs), [Zn-2(BDC)(lac)(DMF)]center dot guest (2) (H (2) BDC = benzene dicarboxylic acid; H(2)lac = lactic acid; guest = 1.5DMF + i-PrOH), [Co-2(BDC)(lac)(DMF)]center dot guest (3) (guest = DMF + 2H(2)O), [Fe-4(BDC)(3)(lac)(2)(DMF)(2)](CO3)center dot guest (4) (guest = DMF + 2H(2)O), and {Zn-11(BPDC)(6)(lac)(6)[NH2(CH32](2)}center dot guest (H2BPDC = 3,3'- biphenyldicarboxylic acid; guest = 6DMF + 18H(2)O) (5), are prepared through the reactions of racemic lactic acid (rac-H(2)lac) with different metal ions and auxiliary ligands. Structural analyses and DFT calculations reveal that forming more and stronger coordination bonds between the auxiliary ligand and metal ions is more conducive to the spontaneous resolution of enantiomers in 3D CPs than simply increasing the entropy of the auxiliary ligand itself.