Sintesi di un nuovo sistema macrociclico che agisce da macchina molecolare guidata dal pH. Abstract: The synthesis of the macrocyclic ligand 4,4'-(2,5,8,11,14-pentaaza[15])-2,2'-bipyridylophane (L3), which contains a pentaamine chain linking the 4,4'-positions of a 2,2'-dipyridine moiety, is reported. Protonation and Zn(II) complexation by L3 and by macrocycle L2, containing the same pentaamine chain connecting the 6,6'-positions of 2,2'-dipyridine, were studied by means of potentiometric, UV-vis, and fluorescent emission measurements. While in L2 all the nitrogen donor atoms are convergent inside the macrocyclic cavity, in L3 the heteroaromatic nitrogen atoms are located outside. Both ligands form mono- and dinuclear Zn(II) complexes in aqueous solution. In the mononuclear Zn(II) complexes with L2, the metal is coordinated inside the macrocyclic cavity, bound to the heteroaromatic nitrogen donors and three amine groups of the aliphatic chain. As shown by the crystal structure of the [ZnL2](2+) complex, the two benzylic nitrogens are not coordinated and facile protonation of the complex takes place at slightly acidic pH values. Considering the mononuclear [ZnL3](2+) complex, the metal is encapsulated inside the cavity, not coordinated by the dipyridine unit. Protonation of the complex occurs on the aliphatic polyamine chain and gives rise to translocation of the metal outside the cavity, bound to the heteroaromatic nitrogens.
Protonation and Zn(II) Coordination by Dipyridine-Containing Macrocycles with Different Molecular Architecture. A case of pH-Controlled Metal Jumping Outside-Inside the Macrocyclic Cavity / Carlos Lodeiro, † A. Jorge Parola; Pina, † Fernando; Bazzicalupi, † Carla; Bencini, ‡ Andrea; Bianchi, ‡ Antonio; Giorgi, ‡ Claudia; Masotti, ‡ Andrea; Barbara, Valtancoli. - In: INORGANIC CHEMISTRY. - ISSN 0020-1669. - STAMPA. - 40:(2001), pp. 2968-2975.
Protonation and Zn(II) Coordination by Dipyridine-Containing Macrocycles with Different Molecular Architecture. A case of pH-Controlled Metal Jumping Outside-Inside the Macrocyclic Cavity
BAZZICALUPI, CARLA;BENCINI, ANDREA;BIANCHI, ANTONIO;GIORGI, CLAUDIA;VALTANCOLI, BARBARA
2001
Abstract
Sintesi di un nuovo sistema macrociclico che agisce da macchina molecolare guidata dal pH. Abstract: The synthesis of the macrocyclic ligand 4,4'-(2,5,8,11,14-pentaaza[15])-2,2'-bipyridylophane (L3), which contains a pentaamine chain linking the 4,4'-positions of a 2,2'-dipyridine moiety, is reported. Protonation and Zn(II) complexation by L3 and by macrocycle L2, containing the same pentaamine chain connecting the 6,6'-positions of 2,2'-dipyridine, were studied by means of potentiometric, UV-vis, and fluorescent emission measurements. While in L2 all the nitrogen donor atoms are convergent inside the macrocyclic cavity, in L3 the heteroaromatic nitrogen atoms are located outside. Both ligands form mono- and dinuclear Zn(II) complexes in aqueous solution. In the mononuclear Zn(II) complexes with L2, the metal is coordinated inside the macrocyclic cavity, bound to the heteroaromatic nitrogen donors and three amine groups of the aliphatic chain. As shown by the crystal structure of the [ZnL2](2+) complex, the two benzylic nitrogens are not coordinated and facile protonation of the complex takes place at slightly acidic pH values. Considering the mononuclear [ZnL3](2+) complex, the metal is encapsulated inside the cavity, not coordinated by the dipyridine unit. Protonation of the complex occurs on the aliphatic polyamine chain and gives rise to translocation of the metal outside the cavity, bound to the heteroaromatic nitrogens.I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.