Four novel coordination compounds based on N-acetyl-L-phenylalanine: Synthesis, characterization and fluorescence properties

Four novel d10 transition metal chiral coordination compounds Cd(L-acphe)2(H2O)2 (1), {[Cd(L-acphe)2(bpe) (H2O)].2.5H2O}n (2), {[Cd(L-acphe)2 (4,4 '-bipy)(H2O)].H2O}n (3), {[Zn2(L-acphe)2(bpp)2(OH)]NO3.2H2O}n (4) (L-Hacphe = N-acetyl-L-phenylalanine, 4,4 '-bipy = 4,4 '-bipyridine, bpe = 1,2-bis (4-pyridyl)ethane, bpp = 1,3-bis (4-pyridyl)propane) have been synthesized by changing central metal ions and N-containing auxiliary ligands. Their structures were determined by single crystal X-ray diffraction analysis and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, powder X-ray diffraction and circular dichroism. The structures of compounds 1-3 with cadmium(II) as the center metal ion change from 0D, 1D to 2D, ultimately compound 1 generates a 2D supramolecular structure via hydrogen bonding, while compounds 2 and 3 expand to 3D supramolecular structures through hydrogen bonding. The compound 4 with zinc(II) as the center metal ion feature 1D chain structures, and 3D supramolecular structure of compound 4 is formed by hydrogen bonding. The present results indicate that selecting central metals with different electronic structures and introducing different N-containing auxiliary ligands could achieve the regulation of the structures of compounds. In addition, the fluorescence recognition properties of compounds 3 and 4 demonstrate that they can highly selectively detect Fe3+ and nitrobenzene in aqueous solutions through fluorescence quenching, indicating that compounds 3 and 4 are expected to become bifunctional fluorescence recognition sensors for the detection of Fe3+ ions and nitrobenzene.