Homochiral Supramolecular Compounds Constructed from Amino Acid Derivatives: Syntheses, Structures, Chiroptical, and Photoluminescence Properties

Recrystallization of enantiopure amino acid derivatives N-(2-pyridylmethyl)-alanine in MeOH resulted in high quality crystals of compounds 1 (l-Hpala) and 2 (d-Hpala). Self-assembly of l- or d-Hpala with Zn(CH3CO2)2·2H2O in MeOH in a ratio of 2:1 produced two enantiopure neutral mononuclear complexes [Zn(l-pala)2]·H2O (3) and [Zn(d-pala)2]·H2O (4) with almost quantitative yields. X-ray single crystal diffraction analyses reveal that they are two-dimensional undulate homochiral supramolecular structures. Circular dichroism (CD) spectra confirm that 1 and 2, 3 and 4 are one pair of enantiomers, respectively. [Cu1.5(spp)(bpy)1.5(H2O)2(NO3)](NO3)·4H2O (5) was prepared by the self-assembly of Cu(NO3)2·3H2O, pala−, and 4.4′-dipyridyl (bpy) in a H2O−EtOH mixture involving the in situ formation of a Schiff base ligand N-(2-pyridylmethyl)-pyruvic acid (spp−). Compound 5 crystallized in the centrosymmetric C2/c space group. It features a three-dimensional supramolecular network by interconnection of an antenna-shaped Cu-containing sheet and a hydrogen bonded supramolecular layer in the alternate ...ABAB... stacking mode. The solid-state photoluminescence properties of 1 and 3 were also investigated.