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One Ferromagnetic and Two Antiferromagnetic Dinuclear Nickel(II) Complexes Derived from a Tridentate N,N,O‐Donor Schiff Base Ligand: A Density Functional Study of Magnetic Coupling
Author(s) -
Biswas Rituparna,
Giri Sanjib,
Saha Shyamal K.,
Ghosh Ashutosh
Publication year - 2012
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.201200028
Subject(s) - chemistry , schiff base , crystallography , deprotonation , ligand (biochemistry) , magnetic susceptibility , octahedron , denticity , bridging ligand , nickel , antiferromagnetism , chelation , octahedral molecular geometry , stereochemistry , inorganic chemistry , ion , crystal structure , organic chemistry , biochemistry , receptor , physics , condensed matter physics
Three new dinuclear Ni II complexes, [Ni 2 L 2 (NO 3 ) 2 ] ( 1 ), [Ni 2 L 2 (NO 2 ) 2 ] ( 2 ), and [Ni 2 L 2 (CH 3 COO) 2 (H 2 O)] ( 3 ), have been synthesized by using a tridentate Schiff base ligand, 2‐({[3‐(dimethylamino)propyl]imino}methyl)phenol (HL), along with a nitrate, nitrite, or acetate ion, respectively, as co‐ligand. These three complexes were characterized by spectral analysis, X‐ray crystallography, and variable‐temperature magnetic susceptibility measurements. The structural analyses revealed that the Ni II ions are coordinated by the deprotonated chelating tridentate Schiff base and possess a distorted octahedral geometry in all three complexes. Complexes 1 and 2 are two di‐μ 2 ‐phenoxido‐bridged species in which the nitrate and nitrite act as chelating co‐ligands. However, in complex 3 , in which the acetate anion is monodentate, an additional water bridge is present along with two μ 2 ‐phenoxido bridges making the complex a face‐sharing bi‐octahedron. Magnetic susceptibility measurements indicate an antiferromagnetic intradimer interaction in complexes 1 and 2 with J values of –20.34(5) and –25.25(4) cm –1 , respectively, whereas complex 3 shows a dominant ferromagnetic exchange coupling with J = 19.11(9) cm –1 . DFT calculations were performed, and the theoretically obtained J values of –19.99 (for 1 ), –24.19 (for 2 ) and 18.81 cm –1 (for 3 ) corroborate very well the experimental results. An attempt has also been made to correlate the effect of Ni ··· Ni distances and bridging Ni–O–Ni angles on the coupling constants of the Ni II complexes through DFT calculations. The relative energy calculations show that the diphenoxido‐bridged complexes are stable at larger bridging angles, and consequently the coupling is antiferromagnetic, whereas with an additional water bridge, the formation of complexes with the Ni–O–Ni bridging angle in the ferromagnetic region is energetically profitable.