In this paper we describe the synthesis and magnetic properties of a series of 3d-4f complexes of general formula [M₄Ln(OH)₂(chp)₄(SALOH)₅(H₂O)(MeCN)(Solv)] (Solv = MeOH, MeCN, H₂O; chp stands for deprotonated 6-chloro-2-hydroxypyridine (C₅H₃ClNO), SALOH stands for monodeprotonated 3,5-ditert-butylsalicylic acid (C₁₅H₂₁O₃)) obtained by a solvent-free microwave assisted synthesis method. The Ni(ii) complexes (Ni₄Gd, Solv = MeOH; Ni₄Dy, Solv = MeCN) are not SMMs in the absence of an applied dc field. The replacement of Ni(ii) by Co(ii) (Co₄La, Solv = MeOH; Co₄Gd, Solv = H₂O; Co₄Gd-MeCN, Solv = MeCN; Co₄Tb, Solv = MeOH; Co₄Dy, Solv = H₂O) results in improved SMM properties.