Abstract
A family of thirteen tetranuclear heterometallic zinc(II)-lanthanide(III) complexes of the hexa-imine macrocycle (L-Pr)(6-), with general formula Zn(3)(II)Ln(III)(L-Pr)(NO3)(3)center dot xsolvents (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm or Yb), were prepared in a one-pot synthesis using a 3 : 1 : 3 : 3 reaction of zinc(II) acetate, the appropriate lanthanide(III) nitrate, the dialdehyde 1,4-diformyl-2,3-dihydroxybenzene (H2L1) and 1,3-diaminopropane. A hexanuclear homometallic zinc(II) macrocyclic complex [Zn-6(L-Pr)(OAc)(5)(OH)(H2O)]center dot 3H(2)O was obtained using a 2 : 0 : 1 : 1 ratio of the same reagents. A control experiment using a 1 : 0 : 1 : 1 ratio failed to generate the lanthanide-free [Zn-3(L-Pr)] macrocyclic complex. The reaction of H2L1 and zinc(II) acetate in a 1 : 1 ratio yielded the pentanuclear homometallic complex of the dialdehyde H2L1, [Zn-5(L-1)(5)(H2O)(6)]center dot 3H(2)O. An X-ray crystal structure determination revealed [(Zn3PrIII)-Pr-II(L-Pr)(NO3)(2)(DMF)(3)](NO3)center dot 0.9DMF has the large ten-coordinate lanthanide(III) ion bound in the central O-6 site with two bidentate nitrate anions completing the O-10 coordination sphere. The three square pyramidal zinc(II) ions are in the outer N2O2 sites with a fifth donor from DMF. Measurement of the magnetic properties of [(Zn3DyIII)-Dy-II(L-Pr)(NO3)(3)(MeOH)(3)]center dot 4H(2)O with a weak external dc field showed that it has a frequency-dependent out-of-phase component of ac susceptibility, indicative of slow relaxation of the magnetization (SMM behaviour). Likewise, the Er and Yb analogues are field-induced SMMs; the latter is only the second example of a Yb-based SMM. The neodymium, ytterbium and erbium complexes are luminescent in the solid phase, but only the ytterbium and neodymium complexes show strong lanthanide-centred luminescence in DMF solution.