Highly luminescent Eu(3+) and Tb(3+) macrocyclic complexes bearing an appended phenanthroline chromophore.
A two-component ligand system (1) containing 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) as the hosting unit for the lanthanide cations and an appended asymmetrically functionalized 1,10-phenanthroline (phen) as the chromophore was synthesized. The 1:1 complexes with Eu(3+), Gd(3+), Tb(3+), and Yb(3+) have been prepared and studied in aqueous solution. For Gd.1, a relaxivity value of 2.4 mM(-1) s(-1) has been measured at 20 MHz and 25 degrees C, which indicates that there are no water molecules in the first coordination sphere of the metal ion. The analysis of high resolution (1)H NMR spectra of Yb.1 supports this view and suggests the direct involvement of the phen moiety in the coordination of the metal ion. For Eu.1 and Tb.1, the absorption and luminescence spectra, the overall luminescence efficiencies, and the metal-centered (MC) lifetimes were obtained; coordination features were also determined by comparing luminescence properties in water and deuterated water. For Eu.1 and Tb.1, the overall emission sensitization (se) process in air-equilibrated water was found to be notably effective with phi(se) = 0.21 and 0.11, respectively. A detailed study of the steps originating from light absorption at the phen unit and leading to MC sensitized emission was performed.
Quici
Silvio
S
Istituto ISTM-CNR and Dipartimento di Chimica Organica e Industriale dell'Università, Via C. Golgi 19, I-20133 Milano, Italy. franz@frae.bo.cnr.it
Marzanni
Giovanni
G
Cavazzini
Marco
M
Anelli
Pier Lucio
PL
Botta
Mauro
M
Gianolio
Eliana
E
Accorsi
Gianluca
G
Armaroli
Nicola
N
Barigelletti
Francesco
F