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New Mixed‐Valence Mn II/III 6 Complexes Bearing Oximato and Azido Ligands: Synthesis, and Structural and Magnetic Characterization
Author(s) -
Lampropoulos Christos,
Stamatatos Theocharis C.,
Manos Manolis J.,
Tasiopoulos Anastasios J.,
Abboud Khalil A.,
Christou George
Publication year - 2010
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200901013
Subject(s) - chemistry , valence (chemistry) , oxime , magnetization , crystallography , cationic polymerization , ketone , ion , manganese , magnetic susceptibility , stereochemistry , medicinal chemistry , magnetic field , organic chemistry , physics , quantum mechanics
The combined use of the anion of methyl 2‐pyridyl ketone oxime (mpko – ) and azides (N 3 – ) in non‐carboxylate Mn chemistry has afforded two new Mn 6 clusters, [Mn 6 O 3 (N 3 ) 3 (mpko) 6 (H 2 O) 3 ](ClO 4 ) 2 ( 1 ) and [Mn 6 O 3 (N 3 ) 5 (mpko) 6 (H 2 O)] ( 2 ), which are mixed‐valence (Mn II , 5 Mn III ). The 1:1:1:1 reaction of Mn(ClO 4 ) 2 · 6H 2 O, mpkoH, NaN 3 and NEt 3 in MeOH gave the cationic complex 1 , while a similar reaction using additional NaO 2 CMe led instead to the neutral complex 2 . The structurally unprecedented cores of the two cages are very similar, and contain the six Mn ions in a topology comprising three vertex‐sharing oxide‐centered triangles bridged by two end‐on azides. Variable‐temperature, solid‐state dc and ac magnetization studies were carried out for 1 and 2 in the 1.8–300 K range. The data reveal S = 5/2 ground states for both complexes, and fitting of magnetization vs. field ( H ) and temperature ( T ) data by matrix diagonalization for 1 gave S = 5/2, D = –1.4(3) cm –1 , and g = 1.99(1), where D is the axial zero‐field splitting (ZFS) parameter. The combined results demonstrate the versatility of 2‐pyridyl ketone oxime anions in the presence of suitable ancillary ligands, such as azides, for the synthesis of new Mn clusters, without requiring the co‐presence of carboxylate ligands.