title: Self-assembly of discrete M6L8 coordination cages based on a conformationally flexible tripodal phosphoric triamide ligand.
abstract: Reactions of a tripodal ligand, N,N',N″-tris(3-pyridinyl)phosphoric triamide (TPPA), and a series of transition-metal ions result in the assembly of five discrete M(6)L(8) coordination cages [M(6)(TPPA)(8)(H(2)O)(12)](ClO(4))(12)·57H(2)O [M = Ni(2+) (1), Co(2+) (2), Zn(2+) (3), Cd(2+) (4)] and [Pd(6)(TPPA)(8)]Cl(12)·22H(2)O (5). X-ray structural analyses reveal that the cages have large internal cavities and flexible windows. The flexible ligand TPPA adopts the syn conformation in cages 1-4, but it transforms to the anti conformation in cage 5. Because of the conformational transformation, the sizes of the windows and the volume of the internal cavity of cage 5 are increased. (1)H NMR and electrospray mass spectrometric studies show that cage 5 maintains its structural integrity in solution. Additionally, compounds 3 and 4 exhibit strong blue fluorescent emissions, which are 1 order of magnitude higher than that of the free ligand.
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People's Republic of China.
authors.forename: Xing-Jun
authors.initials: XJ
authors.lastname: Li
authors.forename: Fei-Long
authors.initials: FL
authors.lastname: Jiang
authors.forename: Ming-Yan
authors.initials: MY
authors.lastname: Wu
authors.forename: Shu-Quan
authors.initials: SQ
authors.lastname: Zhang
authors.forename: You-Fu
authors.initials: YF
authors.lastname: Zhou
authors.forename: Mao-Chun
authors.initials: MC
authors.lastname: Hong