Effect of water/carboxymethylcellulose gel on the excimer formation of polyamine ligands functionalized with naphthalene.
Formation of intramolecular excimers was studied for the compounds 6,20-bis-naphthalene-2-ylmethyl-3,6,9,17,20,23,29,30-octaaza-tricyclo[23.3.1.1] triaconta-1(29),11,13,15(30),25,27-hexane (L1), a bis-naphthalene derivative, and N1-(2-{bis-[2-(3-amino-propylamino)-ethyl]-amino}-ethyl)-propane-1,3-diamine (L2), a tris-naphthalene derivative, incorporated in gels of carboxymethylcellulose sodium salt. Excimers are formed through dynamic processes as well as from ground state dimers. A mathematical treatment including preformed dimers was used to split the static and dynamic contributions in the excimer/monomer emission ratio. In the case of compound L1, the activation energy for excimer formation in water is 11 kJ mol(-1) and experimental evidence that the dynamic terms are identical in water and in the gel was achieved. On the other hand, ground state dimers are extremely favorable in the gel with an equilibrium constant of 8.2 at 25 degrees C. On the contrary, in the case of compound L2, the ground state dimers are observed in water but not in the gel. The results were interpreted as reflecting a balance between specific interactions (hydrogen bond) and confinement effects.
REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Portugal.
Laura
L
Rodríguez
Estefanía
E
Delgado-Pinar
Alejandra
A
Sornosa-Ten
Javier
J
Alarcón
Enrique
E
García-España
Manoli
M
Cano
João C
JC
Lima
Fernando
F
Pina