LnIII2MnIII2 heterobimetallic "butterfly" complexes displaying antiferromagnetic coupling (Ln = Eu, Gd, Tb, Er)Electronic supplementary information (ESI) available: Figures detailing the hydrogen bonding between the clusters (Fig. S1, S2, S3, S4), bond valence sum calculations of complexes 1Gd, 1Tb and 1Er. CCDC 884900-884902. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2dt31144e

The isostructural heterometallic complexes [Ln III 2 Mn III 2 O 2 (ccnm) 6 (dcnm) 2 (H 2 O) 2 ] (Ln = Eu ( 1Eu ), Gd ( 1Gd ), Tb ( 1Tb ), Er ( 1Er ); ccnm = carbamoylcyanonitrosomethanide; dcnm = dicyanonitrosomethanide) have been synthesised and structurally characterised. The in situ transition metal promoted nucleophilic addition of water to dcnm, forming the derivative ligand ccnm, plays an essential role in cluster formation. The central [Ln III 2 Mn III 2 (O) 2 ] moiety has a "butterfly" topology. The coordinated aqua ligands and the NH 2 group of the ccnm ligands facilitate the formation of a range of hydrogen bonds with the lattice solvent and neighbouring clusters. Magnetic measurements generally reveal weak intracluster antiferromagnetic coupling, except for the large J MnMn value in 1Gd . There is some evidence for single molecule magnetic (SMM) behaviour in 1Er . Comparisons of the magnetic properties are made with other recently reported butterfly-type {Ln III x M III 4 x (d-block)} clusters, x = 1, 2; M = Mn, Fe. In situ ligand formation has been utilised in the synthesis of the heterometallic complexes [Ln III 2 Mn III 2 O 2 (ccnm) 6 (dcnm) 2 (H 2 O) 2 ] (Ln = Eu, Gd, Tb, Er), with evidence of single molecule magnetic (SMM) behaviour observed in the erbium analogue.