title: Cu(ii) complexation with an acridine-containing macrocycle. Assembly of water cluster chains within the cavity of tetranuclear metallomacrocycles.
abstract: The synthesis and characterisation of a new macrocyclic compound (L), composed of a pentamine chain linking the 2,7 positions of an acridine moiety, is reported. Cu(ii) complexation was studied by means of potentiometric, UV-vis and EPR measurements in aqueous solutions. This study reveals that the ligand forms a stable tetranuclear complex with an overall [Cu(4)L(2)(OH)(4)](4+) stoichiometry in aqueous solution. The crystal structure of the [Cu(8)L(4)(micro-OH)(8)(micro-NO(3))(3)](NO(3))(5).32H(2)O complex, isolated from neutral aqueous solution, shows that it is formed by tetranuclear clusters [Cu(4)L(2)(micro-OH)(4)(micro-NO(3))(x)]((4-x)+) (x= 1 or 2), composed of two [Cu(2)L](4+) macrocyclic units linked together by four bridging hydroxide and nitrate anions to give an overall metallomacrocyclic structure. Magnetic measurements shows that the hydroxide-bridged Cu(ii) ions are ferromagnatically coupled. Inspection of the crystal packing shows that couples of metallomacrocycles are paired by pi-stacking interactions between acridine moieties, giving rise to an internal hydrophilic cavity were hexameric or pentameric water clusters are enclosed. The coupled metallomacrocycles assume a columnar disposition growing along the a axis, giving rise to channels passing through the cavities of the metallomacrocycles; these channels are filled by chains of 5- or 6-membered water clusters linked together by [NO(3).H(2)O](2) units.
authors.affiliation: Department of Chemistry, University of Florence, Via della Lastruccia 3, 50019-Sesto Fiorentino, Firenze, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Bartoli
authors.forename: Carla
authors.initials: C
authors.lastname: Bazzicalupi
authors.forename: Silvia
authors.initials: S
authors.lastname: Biagini
authors.forename: Lucia
authors.initials: L
authors.lastname: Borsari
authors.forename: Andrea
authors.initials: A
authors.lastname: Bencini
authors.forename: Enrico
authors.initials: E
authors.lastname: Faggi
authors.forename: Claudia
authors.initials: C
authors.lastname: Giorgi
authors.forename: Claudio
authors.initials: C
authors.lastname: Sangregorio
authors.forename: Barbara
authors.initials: B
authors.lastname: Valtancoli