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Variation of nuclearity in Ni complexes of a Schiff base ligand: crystal structures and magnetic studies
Four new Ni II complexes, [Ni(L 1 )](NO 3 )·1.5H 2 O ( 1 ), [Ni(L 1 )][Ni(HL 2 )](NO 3 ) 2 ·H 2 O ( 2 ), [Ni 4 (L 2 ) 2 (μ 3 -OCH 3 ) 2 (NO 3 )](NO 3 )·CH 3 OH ( 3 ), and [Ni 6 (L 2 ) 2 ( o -van) 2 (μ 3 -OH) 4 ](NO 3 ) 2 ·H 2 O ( 4 ), where HL 1 = 2-{[2-(2-aminoethylamino)ethylimino]methyl}-6-methox...
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| Published in: | CrystEngComm 2019-08, Vol.21 (31), p.462-4631 |
|---|---|
| Main Authors: | , , , |
| Format: | Article |
| Language: | |
| Online Access: | Get full text |
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| Summary: | Four new Ni
II
complexes, [Ni(L
1
)](NO
3
)·1.5H
2
O (
1
), [Ni(L
1
)][Ni(HL
2
)](NO
3
)
2
·H
2
O (
2
), [Ni
4
(L
2
)
2
(μ
3
-OCH
3
)
2
(NO
3
)](NO
3
)·CH
3
OH (
3
), and [Ni
6
(L
2
)
2
(
o
-van)
2
(μ
3
-OH)
4
](NO
3
)
2
·H
2
O (
4
), where HL
1
= 2-{[2-(2-aminoethylamino)ethylimino]methyl}-6-methoxyphenol and H
2
L
2
=
N
,
N
′-bis(3-methoxysalicylidene)diethylenetriamine, have been synthesized by changing the reaction conditions and stoichiometry of the reactants. Single-crystal X-ray diffraction study reveals that complexes
1
and
2
are mononuclear with a square planar geometry around the Ni
II
centre, whereas complexes
3
and
4
possess tetranuclear and hexanuclear structures, respectively, with octahedral Ni
II
centres. The differences in nuclearity, coordination numbers and geometry of the Ni
II
centres in the complexes have been explained considering the flexible coordination modes and denticity of the Schiff base ligands. Variable temperature molar magnetic susceptibility measurements show that the tetranuclear Ni
II
4
complex (
3
) is ferromagnetically coupled with two exchange couplings,
J
1
= 0.64 cm
−1
and
J
2
= 8.41 cm
−1
, whereas the hexanuclear Ni
II
6
complex (
4
) is antiferromagnetically coupled with four exchange couplings,
J
1
= −5.60 cm
−1
,
J
2
= −9.39 cm
−1
,
J
3
= −5.18 cm
−1
and
J
4
= 3.72 cm
−1
. The sign and magnitude of these exchange couplings in complexes
3
and
4
are correlated with similar types of reported cubane or defective cubane-like Ni
II
complexes. Electrochemical measurements of these complexes reveal that the Ni
II
centres are irreversibly reduced with one reduction potential for
1
,
3
and
4
, whereas for
2
the Ni
II
centres are irreversibly reduced with two reduction potentials.
Four Ni
II
complexes have been synthesized by changing the reaction conditions and stoichiometry of the reactants. The magnetic coupling in the Ni
II
4
complex is ferromagnetic whereas that in the Ni
II
6
complex is antiferromagnetic. |
|---|---|
| ISSN: | 1466-8033 |
| DOI: | 10.1039/c9ce00574a |