Modular, Homochiral, Porous Coordination Polymers: Rational Design, Enantioselective Guest Exchange Sorption and Ab Initio Calculations of Host-Guest Interactions

Two new, homochiral, porous metal organic coordination polymers [Zn-2(ndc){(R)-man}(dmf)]center dot.3DMF and [Zn-2(bpdc)1(R)-man}(dmf)]center dot 2DMF (ndc=2,6-naphthalenedicarboxylate; bpdc=4,4'-biphenyldicarboxylate; man= mandelate; dmf -=/V,M-dimethylformamide) have been synthesized by heating Zn-II nitrate, H(2)ndc or H(2)bpdc and chiral (R)-mandelic acid (H(2)man) in DMF. The colorless crystals were obtained and their structures were established by single-crystal X-ray diffraction. These isoreticular structures share the same topological features as the previously reported zinc(II) terephthalate lactate [Zn-2(bdc){(S)-lac)-(dmf)}-DMF framework, but have larger pores and opposite absolute configuration of the chiral centers. The enhanced pores size results in differing stereoselective sorption properties: the new metal organic frameworks effectively and stereoselectively (cc up to 62%) accommodate bulkier guest molecules (alkyl aryl sulfoxides) than the parent [Zn-2(bdc)((S)-lac}(dmp]center dot DMF, while the latter demonstrates decent enantioselectivity toward precursor of chiral anticancer drug sulforaphane, CH3SO(CH2)(4)OH. The new homochiral porous metal organic coordination polymers are capable of catalyzing a highly selective oxidation of bulkier sulfides (2-NaphSMe (2-C10H7SMe) and PhSCH2Ph) that could not be achieved by the smaller-pore [Zn-2(bdc){(S)-lac)(dmf)]center dot DMF. The sorption of different guest molecules (both R and S isomers) into the chiral pores of [Zn-2(bdc){(S)-lac}(dmf)]center dot DMF was modeled by using ab initio calculations that provided a qualitative explanation for the observed sorption enantioselectivity. The high stereo-preference is accounted for by the presence of coordinated inner-pore DMF molecule that forms a weak C-H center dot center dot center dot O bond between the DMF methyl group and the (S)PhSOCH3 sulfinyl group.