The interaction of the pyrazole-containing macrocyclic receptors 3,6,9,12,13,16,19,22,25,26-
decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene 1[L1], 13,26-dibenzyl-3,6,9,12,13,16,-
19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene 2[L2], 3,9,12,13,16,22,-
25,26-octaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene 3[L3], 6,19-dibenzyl-3,6,9,12,13,-
16,19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene 4[L4], 6,19-diphenethyl-
3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene 5[L5], and
6,19-dioctyl-3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene
6[L6] with L-glutamate in aqueous solution has been studied by potentiometric techniques. The synthesis
of receptors 3-6[L3-L6] is described for the first time. The potentiometric results show that 4[L4] containing
benzyl groups in the central nitrogens of the polyamine side chains is the receptor displaying the larger
interaction at pH 7.4 (Keff ) 2.04 104). The presence of phenethyl 5[L5] or octyl groups 6[L6] instead of
benzyl groups 4[L4] in the central nitrogens of the chains produces a drastic decrease in the stability [Keff
) 3.51 102 (5), Keff ) 3.64 102 (6)]. The studies show the relevance of the central polyaminic nitrogen
in the interaction with glutamate. 1[L1] and 2[L2] with secondary nitrogens in this position present significantly
larger interactions than 3[L3], which lacks an amino group in the center of the chains. The NMR and modeling
studies suggest the important contribution of hydrogen bonding and ð-cation interaction to adduct formation.This work is devoted to the memory of
Prof. Manuel Lora-Tamayo. Financial support by the Spanish
“Comisio´n Interministerial de Ciencia y Tecnologı´a” (CICYT,
Proyects SAF-99-0063, and BQU2003-09215-CO3-01) is gratefully
acknowledged.Peer reviewe