Assembling Hexagonal‐Bipyramidal {Mn 8 Zn 2 } and {Mn 8 Zn 4 } Clusters

Reaction between Mn(NO 3 ) 2  ⋅ 6H 2 O, Zn(NO 3 ) 2  ⋅ 6H 2 O, 1,3,5‐tri(2‐hydroxyethyl)‐1,3,5‐triazacyclohexane (H 3 L) and pyrazole in MeOH under basic conditions leads to the formation of the decanuclear complex [Mn III 6 Mn II 2 Zn II 2 (L) 2 (pyr) 4 O 4 (OH) 4 (NO 3 ) 2 (MeOH) 2 (H 2 O) 4 ](NO 3 ) 2  ⋅ Η 2 Ο ( 1  ⋅ Η 2 Ο). The metallic core of the cationic cluster consists of a central hexagonal‐bipyramidal {Mn III 4 Mn II 2 Zn II 2 } unit connected to two peripheral trivalent Mn centers arranged in a “trans” fashion, with one Mn III center lying above and one Mn III center below the hexagonal plane. Replacing Mn(NO 3 ) 2  ⋅ 6H 2 O with MnBr 2  ⋅ 4H 2 O and repeating the same reaction leads to the formation of the related, neutral decanuclear complex [Mn III 6 Mn II 2 Zn II 2 (L) 2 (pyr) 4 O 4 (OH) 4 Br 4 (H 2 O) 2 ] ( 2 ), displaying the same metallic core as 1 . Addition of THF to the reaction mixture that produces ( 2 ) affords the neutral dodecanuclear complex [Mn III 6 Mn II 2 Zn II 4 (L) 2 (pyr) 6 O 4 (OH) 4 Br 6 (H 2 O) 4 ] ⋅ 8THF ( 3  ⋅ 8THF), whose metallic skeleton retains the central hexagonal‐bipyramidal {Mn III 4 Mn II 2 Zn II 2 } unit found in 1 and 2 but is now connected to two peripheral {Mn III Zn II } units. Magnetic susceptibility and magnetization measurements carried out in the T =2–300 K temperature range and in fields up to B =7.0 T for all three complexes reveal dominant antiferromagnetic exchange interactions.