Homochiral coordination polymers constructed from V-shaped oxybisbenzoyl-based amino acid derivatives: structures, magnetic and photoluminescence properties

Five novel homochiral coordination polymers (HCPs) [Cu2(ODBALa)2(bpa)2H2O]·7H2O (1), [M(ODBALa)H2O]·H2O (M = Mn for 2; Co for 3), [Cu(ODBPRo)(bpe)]·7H2O (4) and [Cd2.5(ODBPRo)(HODBPRo)3(bpe)2.5]·13H2O (5) have been successfully synthesized by using designed chiral 4,4'-oxybisbenzoyl alanine/proline derivatives in the absence/presence of N-donor ancillary ligands, where H2ODBALa = 4,4'-oxybisbenzoyl-bis(l-alanine), H2ODBPRo = 4,4'-oxybisbenzoyl-bis(l-proline), bpa = 1,2-bis(4-pyridyl)ethane, and bpe = 1,2-bis(4-pyridyl)ethene. Interestingly, the combination of the chiral derivatives and metal ions gives various chiral metal-organic fragments, which are connected by N-donor ancillary ligands to construct the intriguing homochiral structures. In 1, 40-membered [Cu2(ODBALa)2] metallacycles as beads are strung by bpa ligands, yielding a one-dimension (1D) tortuous chain. Compounds 2 and 3 are isomorphous and possess a 3D metal-organic framework, embedding the unique (μ2-COO)(μ2-Ocarboxylate)(μ2-H2O) triple-bridges and twisted (-Mn4(ODBALa)4-)n left-handed helical chains. In 4, the [Cu(ODBPRo)]n left-handed helical chains are linked by bpe ligands to constitute a high undulated 2D layer. In 5, the crab-like [(Cd1)2(Cd2)(Cd3)2(HODBPRo)6(ODBPRo)2] fragments are joined together to form a 1D left-handed helical chain, which is further connected by bpe ligands to build a remarkable layered network. Magnetic susceptibility measurements of 2 and 3 indicate typical antiferromagnetic behaviour between the triple-bridging Mn(ii) ions in 2, whereas ferromagnetic coupling between the triple-bridging Co(ii) ions exists in 3. Moreover, the photoluminescent spectrum of 5 exhibits a strong solid-state emission at 414 nm.