Molecular Structures and Magnetism of Mn 12 Nanomagnets Containing the 3‐Thiophenecarboxylate Ligand

The new Mn 12 single‐molecule magnets containing thiophenyl ligands, [Mn 12 O 12 (O 2 CC 4 H 3 S) 16 (HO 2 CC 4 H 3 S)(H 2 O) 2 ] · 5CH 2 Cl 2 ( 1 ) and [Mn 12 O 12 (O 2 CC 4 H 3 S) 16 (H 2 O) 4 ] · 6CH 2 Cl 2 · 2H 2 O ( 2 ), have been synthesized by ligand‐substitution reactions of 3‐thiophenecarboxylic acid and [Mn 12 O 12 (O 2 CCH 3 ) 16 (H 2 O) 4 ] and investigated by magnetic measurements with a SQUID magnetometer. The X‐ray analysis of 1 shows five‐coordination geometry around the Mn III ion due to the unusual coordination of 3‐thiophenecarboxylic acid to the Mn III ion. Compound 1 displays two different rates of magnetization relaxation, which are faster than that of compound 2 because of structural distortion in the Mn 12 complex of 1 . Magnetic susceptibility measurements on 1 and 2 give the following parameters: U eff (the faster relaxation form of 1 ) = 51.81 K, 1/ τ 0 = 1.90 · 10 8 s –1 ; U eff (the slower relaxation form of 1 ) = 66.44 K, 1/ τ 0 = 1.50 · 10 8 s –1 ; U eff ( 2 ) = 67.09 K, 1/ τ 0 = 1.32 · 10 8 s –1 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)