title: Synthesis and coordination properties of new macrocyclic ligands: equilibrium studies and crystal structures.
abstract: The synthesis and characterization of two new macrocyclic ligands, the bis-macrocyclic compound 2,6-bis(1,4,13-triaza-7,10-dioxacyclopentadec-1-ylmethyl)phenol (L) and 38-methoxy-1,4,13,16,19,28-hexaaza-7,10,22,25-tetraoxatricyclo[14.14.7.1(32,36)]octatriconta-32,34,Delta(36,38)-triene (L1) are reported. Equilibrium studies of basicity and coordination properties toward metal ions such as Cu(II), Zn(II), Cd(II) and Pb(II) were performed for ligand by potentiometric measurements in aqueous solution (298.1 +/- 0.1 K, I= 0.15 mol dm(-3)). L behaves as a hexaprotic base (logK(1)= 10.93, logK(2)= 9.70, logK(3)= 8.79, logK(4)= 8.05, logK(5)= 6.83, logK(6)= 2.55). All metal ions form stable mono- and dinuclear complexes: logK(MLH(-1))= 25.61 for Cu(II), 15.37 for Zn(II), 12.58 for Cd(II) and 13.79 for Pb(II); logK(M(2)LH(-1))= 31.61 for Cu(II), 23.38 for Zn(II), 24.49 for Cd(II) and 23.68 for Pb(II). All these dinuclear species show a great tendency to add the OH(-) group: the equilibrium constant for the addition reaction was found to be logK(M(2)LH(-1)OH)= 4.77 for Cu(II), 5.66 for Zn(II), 2.8 for Cd(II) and 3.18 for Pb(II). In the case of Ni(II), kinetic inertness prevents the possibility of solution studies. The dinuclear solid adducts [Ni(2)H(-1)L(N(3))(3)].EtOH and [Cu(2)H(-1)L(N(3))](ClO(4))(2) were characterized by X-ray analysis.
authors.affiliation: Institute of Chemical Sciences, University of Urbino, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Ambrosi
authors.forename: Paolo
authors.initials: P
authors.lastname: Dapporto
authors.forename: Mauro
authors.initials: M
authors.lastname: Formica
authors.forename: Vieri
authors.initials: V
authors.lastname: Fusi
authors.forename: Luca
authors.initials: L
authors.lastname: Giorgi
authors.forename: Annalisa
authors.initials: A
authors.lastname: Guerri
authors.forename: Mauro
authors.initials: M
authors.lastname: Micheloni
authors.forename: Paola
authors.initials: P
authors.lastname: Paoli
authors.forename: Roberto
authors.initials: R
authors.lastname: Pontellini
authors.forename: Patrizia
authors.initials: P
authors.lastname: Rossi