EFFECT OF MIXED PENDENT GROUPS ON THE SOLUTION AND CATALYTIC PROPERTIES OF EUROPIUM(III) MACROCYCLIC COMPLEXES - BIFUNCTIONAL AND MONOFUNCTIONAL AMIDE AND ALCOHOL PENDENTS IN SEPTADENTATE OR OCTADENTATE LIGANDS

Five new Eu(III) macrocyclic complexes have been prepared and their so lution and catalytic properties studied. The Eu(III) complexes with se ptadentate ligands TRED and NB-TRED dissociate rapidly at pH 7.4, 37 d egrees C (TRED = tris(hydroxyethyl)-1,4,7,10-tetraazacyclododecane, NB -TRED = 1-(nitrobenzyl)-4,7,10-tris(hydroxyethyl)1,4,7,10- tetraazacyc lododecane). Dissociation rates as determined in the presence and abse nce of strongly binding competing ligands suggest that under most cond itions the Eu(III) complexes of ATHC, ABHC, and CNPHC are more kinetic ally inert to dissociation than is the Eu(III) complex containing all hydroxyethyl groups (ATHC = tris(hydroxyethyl)-1,4,7,10-tetraazacyclod odecane, ABHC = 1,7-bis(carbamoylmethyl)-4,10- bis(hydroxyethyl)-1,4,7 ,10-tetraazacyclododecane, CNPHC = 1-(1-carboxamido-3-(4-nitrophenyl)p ropyl)4,7,1 s(2-hydroxyethy1)-1,4,7,10-tetraazacyclododecane). Laser-i nduced luminescence excitation spectra of Eu(III) complexes of ABHC, A THC, CNPHC, THED, and S-THP suggest that there is a single major speci es in solution at pH 6.3 and a second species that appears at more bas ic pH values (THED = akis(hydroxyethyl)-1,4,7,10-tetraazacyclododecane , S-THP = (2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane). The speci es present at basic pH is proposed to be an alkoxide or hydroxide comp lex; pK(a) values as determined by potentiometric titrations are 7.5 a nd 8.1 for Eu(CNPHC)(3+) and Eu(ABHC)(3+),respectively. Eu(CNPHC)(3+), Eu(ATHC)(3+), and Eu(ABHC)(3+) promote transesterification of the hyd roxypropyl ester of 4-nitrophenyl phosphate with pseudo-first-order ra te constants at pH 7.3, 37 degrees C, and 1.00 mM complex of 1.4 x 10( -5), 9.3 x 10(-6), and 1.0 x 10(-6) s(-1), respectively. Both Eu(CNPHC )(3+) and Eu(ABHC)(3+) promote attack of an hydroxyethyl group of the macrocycle on bis(4-nitrophenyl) phosphate with pseudo-first-order rat e constants at pH 7.3, 37 degrees C, and 1.00 mM complex of 1.5 x 10(- 4) and 3.5 x 10(-5) s(-1), respectively. In general, an increase in th e number of amide groups on the macrocycle of the Eu(III) complex decr eases the rate of both intramolecular or intermolecular phosphate dies ter transesterification reactions.