BULKY ORTHO 3-METHOXY GROUPS ON N4O3 AMINE PHENOL LIGANDS PRODUCING 6-COORDINATE BIS(LIGAND)LANTHANIDE COMPLEX CATIONS [LN(H3L)2]3+ (LN = PR, GD H3L = TRIS(((2-HYDROXY-3-METHOXYBENZYL)AMINO)ETHYL)AMINE)

The synthesis and characterization of an N4O3 amine phenol (tris(((2-hydroxy-3-methoxybenzyl)amino)ethyl)amine, H3L4) and its lanthanide complexes [Ln(H3LA)(NO3)3] (Ln = Pr, Nd) and [Ln(H3L4)2](NO3)3 (Ln = Pr, Nd, Gd, Yb) are reported. The N4O3 amine phenol ligand is the KBH4 reduction product of the Schiff base derived from the reaction of tris(2-aminoethyl)amine (tren) and 3 equiv of o-vanillin. The reactions of lanthanide nitrates with 1 equiv of H3L4 produce nine-coordinate type II complexes, [Ln(H3L4)(NO3)3] (Ln = Pr, Nd), in which H3L4 acts as a tridentate O3 ligand and six-coordinate bis(ligand) type IV complexes, [Ln(H3L4)2](NO3)3 (Ln = Gd, Yb). The latter were prepared from the reactions of lanthanide nitrates with 2 equiv of H3L4 in the presence of sodium hydroxide. The X-ray crystal structures of [Ln(H3L4)2](NO3)3.xH2O.YMeOH (Ln = Pr, x = 5.56, y = 0.44; Ln = Gd, x = 5.96, y = 0.66) have been determined. Crystals of [Ln(H3L4)2](NO3)3.xH2O.yMeOH (Ln = Pr, x = 5.56, y = 0.44; Ln = Gd, x = 5.96, y = 0.66) are isomorphous, crystallizing in the monoclinic space group C2/c, with a = 25.260(2) [25.131(2)] angstrom, b = 14.927(3) [14.990(4)] angstrom, c = 21.402(2) [21.459(3)] angstrom, beta = 112.912(7)-degrees [112.615(7)-degrees], Z = 4, and V = 7433(2) [7462(2)] angstrom3 (bracketed values refer to the Gd complex). The structures were solved by the Patterson method and were refined by full-matrix least-squares procedures to R = 0.033 [0.033] and R(w) = 0.040 [0.0361 for 5032 [58671 reflections with I greater-than-or-equal-to 3sigma(I), respectively. In both complexes, the three phenolate O atoms of each of the two tridentate amine phenol ligands coordinate to the metal ions in a slightly distorted octahedral geometry while the secondary amine N atoms are protonated and uncoordinated. The effects of bulky 3-methoxy groups of the phenyl rings on the coordinating behavior toward lanthanide metals are discussed.