Syntheses, structures, and properties of lanthanide supramolecular complexes with 1,10-phenanthroline and terminal amino acids with different chain lengths

Four lanthanide supramolecular coordination compounds, [Eu(gly)(2)(phen)(2)(H2O)(2)](ClO4)(3)(phen)(4)(H2O)-H-. (1), [Eu-2(APA)(6)(phen)(2)](ClO4)(6)(phen)(4) (.)3H(2)O (2), [Tb-2(ABA)(4)(phen)(4)](ClO4)(6)(phen)(4) (3), and [Eu-2(AHA)(4)(phen)(4)](ClO4)(6)(phen)(2)(.)2H(2)O(.)2C(2)H(5)OH (4) (gly = glycine, APA = 3-aminopropionic acid, ABA = 4-aminobutanoic acid, AHA = 6-aminohexanoic acid, phen = 1,10-phenanthroline), were synthesized and characterized by single crystal X-ray diffraction. Compound 1 has a 2-D supramolecular layered structure of mononuclear coordination cations and free phen molecules connected via hydrogen bonding and pi-pi stacking interactions. 2 forms a 3-D supramolecular network by hydrogen bonding between binuclear coordination cations and free phen molecules, between coordination cations and lattice water molecules, and pi-pi stacking interactions between free phen molecules. Compounds 3 and 4 form 2-D supramolecular structures with pi-pi stacking between coordinating phen molecules, and between free phen molecules hydrogen-bonded to the binuclear coordination cations. The high-resolution emission spectra show only one Eu3+ ion site in the title complexes. The aqueous solutions of the title complexes are all photochromic with the color of the solution changing from yellow to green when irradiated by mercury lamp. During the decoloration process, they return to yellow color.