The structural mobility of zinc complexes with tetradentate tripodal ligands derived from the amino acids glycine and phenylalanine

摘要: Crystallographic studies indicate that aromatic interactions favor the formation of trigonal-bipyramidal zinc(II) complexes with tetradentate tripodal ligand bpaAc–Phe–OMe (N,N-bis(2-picolyl)aminoacyl-(S)-phenylalanine-methylester). The benzyl side chain in [(bpaAc–Phe–OMe)Zn(OTf)]+ (1b, OTf = triflate), [(bpaAc–Phe–OMe)Zn(H2O)]2+ (2b) and [(bpaAc–Phe–OMe)Zn(pz)]2+ (3btt, pz pyrazole; t trigonal-bipyramidal) is oriented towards axial active coordination site phenyl ring ca. 4.5 A away from metal center. Here we show this conformation retained solutions 1b, 2b [(bpaAc–Phe–OMe)Zn(Cl)]+ (8b). Temperature-dependent 1H NMR spectra reveal phenylalanine locked its position as long sphere stays trigonal-bipyramidal. Based on our crystallographic results expected pyrazole N-methylimidazole 3btt [(bpaAc–Phe–OMe)Zn(N-Meim)]2+ (4bttt, N-Meim = N-methylimidazole) to be labile respect addition a sixth such triflate, water, or N-methylimidazole. confirm six-coordinate species 3boo 4booo (o: octahedral) are formed solution. This presumably due solvation effects mobilizes which flexible octahedral complexes.