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

Five novel homochiral coordination polymers (HCPs) [Cu-2(ODBALa)(2)(bpa)(2)H2O]7H(2)O (1), [M(ODBALa)H2O]H2O (M = Mn for 2; Co for 3), [Cu(ODBPRo)(bpe)]7H(2)O (4) and [Cd-2.5(ODBPRo)(HODBPRo)(3)(bpe)(2.5)]13H(2)O (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 H(2)ODBALa = 4,4-oxybisbenzoyl-bis(l-alanine), H(2)ODBPRo = 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 [Cu-2(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 ((2)-COO)((2)-O-carboxylate)((2)-H2O) triple-bridges and twisted (-Mn-4(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.