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Oxalato‐Bridged [Cu II Cr III ] and [Mn II Cr III ] Binuclear Complexes: Synthesis, Crystal Structures, Magnetic and EPR Investigations
Author(s) -
Marinescu Gabriela,
Visinescu Diana,
Cucos Andrei,
Andruh Marius,
Journaux Yves,
Kravtsov Victor,
Simonov Yurii A.,
Lipkowski Janusz
Publication year - 2004
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.200400061
Subject(s) - chemistry , crystallography , denticity , hexacoordinate , crystal structure , oxalate , ligand (biochemistry) , electron paramagnetic resonance , chromium , bridging ligand , inorganic chemistry , stereochemistry , nuclear magnetic resonance , biochemistry , physics , receptor , organic chemistry , silicon
Two new heterobinuclear complexes, [(bipy)(C 2 O 4 )Cr(μ‐C 2 O 4 )Cu(Hfsaaep)(H 2 O)]·2H 2 O ( 1 ) and [(phen)(C 2 O 4 )Cr(μ‐C 2 O 4 )Mn(phen) 2 (N 3 )]·H 2 O ( 2 ) have been obtained by using bis(oxalato)chromium( III ) anions, [Cr(AA)(C 2 O 4 ) 2 ] − , as building blocks [AA = 2,2′‐bipyridine (bipy); 1,10‐phenanthroline (phen)]. The crystal structures of the two complexes have been solved. These complexes comprise neutral oxalato‐bridged Cr III −Cu II and Cr III −Mn II units. The [Cr(AA)(C 2 O 4 ) 2 ] − anion acts as a bidentate ligand toward Cu II in compound 1 and as a monodentate ligand toward Mn II in compound 2 . The copper( II ) ion in 1 exhibits a slightly distorted square bipyramidal stereochemistry, with the aqua ligand and one of the bridging oxalato oxygen atoms disposed in the apical positions [Cu(1)−O(1w) = 2.360(3) Å and Cu(1)−O(4) = 2.504(2) Å]. The second bridging oxalato oxygen atom [Cu(1)−O(2) = 2.0747(18) Å] and the N , N , O ‐type Hfsaaep ligand are located in the basal plane. The distance between the Cr III and Cu II ions across the bridging oxalate unit is 5.506 Å. The Mn II ion in compound 2 is hexacoordinate (two chelating phen ligands, one oxalato bridging oxygen, and one terminal azido group). The intermolecular Cr III ··· Mn II distance is 5.257 Å. The magnetic properties of the two complexes have been investigated. The magnetic coupling between Cr III and Cu II in 1 was found to be ferromagnetic ( J = +1.4 cm −1 ). The nature of the ground state ( S = 2) has been further confirmed by plotting the magnetization‐versus‐field curve. An antiferromagnetic interaction was found between Cr III and Mn II in compound 2 ( J = −1.9 cm −1 ). The magnetization‐versus‐field curve indicates the occurrence of a crossover between the Zeeman components: M S = −1 (ground state S = 1), M S = −2, from the first excited state ( S = 2), and M S = −3, from the second excited state. The EPR spectra of the two compounds are discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)