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The Impact of Anion‐Modulated Structural Variations on the Magnetic Coupling in Trinuclear Heterometallic Cu II –Co II Complexes Derived from a Salen‐Type Schiff Base Ligand
Author(s) -
Ghosh Soumavo,
Aromí Guillem,
Gamez Patrick,
Ghosh Ashutosh
Publication year - 2014
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.201402151
Subject(s) - chemistry , crystallography , thiocyanate , azide , schiff base , denticity , copper , ligand (biochemistry) , ion , stereochemistry , bridging ligand , crystal structure , inorganic chemistry , biochemistry , receptor , organic chemistry
Three new trinuclear heterometallic [(Cu II L) 2 Co II X 2 ] complexes [H 2 L = N , N′ ‐bis(salicylidene)‐1,3‐propanediamine and X = thiocyanate ( 1 ), benzoate ( 2 ), or azide ( 3 )] have been synthesized by reacting the metalloligand [CuL] with Co(ClO 4 ) 2 · 6H 2 O and the NH 4 + or Na + salt of the corresponding anion in methanol. Structural characterization reveals that the central Co II ion is connected to two terminal metalloligands through μ 1,1 ‐diphenoxido bridges in all three complexes. However, two monodentate thiocyanato ions, which are mutually cis coordinated to the Co atom in 1 , generate a “bent” structure, whereas the trans ‐coordinated syn–syn bridging benzoato (1κ O :2κ O′ ) and the end‐on bridging azido (μ 1,1 ) coligands in 2 and 3 , respectively, produce linear structures. The changes in the number and nature of the bridges with a shortening of the distances between the metal centers leads to a concomitant decrease of the average Cu II –O–Co II bridging angle from 99.3(2) to 97.1(4) and 91.5(1)° for 1 , 2 and 3 , respectively. Variable‐temperature magnetic susceptibility measurements show the presence of a dominant antiferromagnetic coupling between the Cu–Co pairs in all three complexes. However, a steady decrease of the magnitude of the exchange coupling constant ( J Cu‐Co ) is observed from –33.4 (for 1 ) to –11.4 (for 2 ) and –2.15 cm –1 (for 3 ). This trend suggests that larger Cu–O–Co angles are associated with stronger antiferromagnetic coupling.