Assisted Self-Assembly to Target Heterometallic Mn-Nd and Mn-Sm SMMs: Synthesis and Magnetic Characterisation of [Mn(7)Ln(3)(O)(4)(OH)(4)(mdea)(3)(piv)(9)(NO3)(3)] (Ln=Nd, Sm, Eu, Gd)**

In an assisted self-assembly approach starting from the [Mn6O2(piv)(10)(4-Me-py)(2)(pivH)(2)] cluster a family of Mn-Ln compounds (Ln=Pr-Yb) was synthesised. The reaction of [Mn6O2(piv)(10)(4-Me-py)(2)(pivH)(2)] (1) with N-methyldiethanolamine (mdeaH(2)) and Ln(NO3)(3) . 6H(2)O in MeCN generally yields two main structure types: for Ln=Tb-Yb a previously reported Mn(5)Ln(4) motif is obtained, whereas for Ln=Pr-Eu a series of Mn(7)Ln(3) clusters is obtained. Within this series the Gd-III analogue represents a special case because it shows both structural types as well as a third Mn(2)Ln(2) inverse butterfly motif. Variation in reaction conditions allows access to different structure types across the whole series. This prompts further studies into the reaction mechanism of this cluster assisted self-assembly approach. For the Mn(7)Ln(3) analogues reported here variable-temperature magnetic susceptibility measurements suggest that antiferromagnetic interactions between the spin carriers are dominant. Compounds incorporating Ln=Nd-III(2), Sm-III(3) and Gd-III (5) display SMM behaviour. The slow relaxation of the magnetisation for these compounds was confirmed by ac measurements above 1.8 K.