1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
z InorganicChemistry
TetranuclearCopper(II)ComplexeswithSimultaneous
PhenoxoandAzidoBridges-Synthesis,Structuraland
MagneticStudies
Priyanka Pandey,
[a]
Dr. Nidhi Dwivedi,
[a]
Dr. Goulven Cosquer,
[b, c]
Prof. Masahiro
Yamashita,
[b, c, d, e]
and Dr. Sailaja S. Sunkari*
[a]
Tetradentate Schiff base ligands with multiple coordinaton sites
are one of the best choice for the construction of multinuclear
metal complexes. Coupled with auxiliary ligands under self
assembling conditions, the scope for generating new structures
increases manifold due to various structure directing factors in
operation. Though, phenoxo or azido bridged copper(II)
systems have been investigated thoroughly from structural and
magnetic aspects, the literature is scanty with combined
phenoxo and azido bridged systems. In a study on the effect of
synthetic conditions on the structures generated and associ-
ated magnetic properties, two new tetranuclear copper com-
plexes, viz., [Cu
4
(L1)
2
(μ-N
3
)
2
(N
3
)
2
](1) and [Cu
4
(L2)
2
(μ-N
3
)
2
(N
3
)
2
](2)
where L1 = N,N’-Bis(salicylidene)diaminopropane (salpn) and
L2 = N,N’-Bis(salicylidene)diaminobenzene (salophen) with both
phenoxo and azido bridges are reported. The tetranuclear
cluster is made of two inversion related dimers built of
phenoxo bridged Cu1 and Cu2 with distorted square planar
and square pyramidal geometries respectively. These dimers
are bridged by symmetrically bridging azides leading to a
tetranuclear core. The contrasting magnetic behavior inspite of
same coordination environments, antiferromagnetic in 1 (J
1
=
2.17 cm
1
;J
2
= 28.15 cm
1
) and ferromagnetic in 2 (J
1
=
74.7 cm
1
;J
2
= 146.5 cm
1
), is understood in terms of lower
bridge angles and closer separation between copper centers in
2 than in 1.
Introduction
Synthesis and structural studies of polynuclear metal com-
plexes is on rise since few years, as they provide interesting
systems with material applications as in catalysis,
[1]
molecule
based magnetism,
[2]
sensing,
[3]
DNA cleavage
[4]
and so on.
Strategies adopted for generation of such polynuclear systems
include self assembly of molecular components and selective
organization of metal ions into predesignated positions of
tailor made ligands.
[5]
While the second approach offers control
over product formation, the first approach often leads to
unpredicted structures of material relevance which may not be
obtained otherwise and are aesthetically pleasing too.
Tetradentate Schiff base ligands provide ideal environment
for positioning the metal ions, thus leading to polynuclear
metal complexes. Connecting such complexes with auxiliary
ligands can lead to discrete metallates or 1-D polymer chains
depending on synthetic conditions as well as ligand geome-
try.
[6]
The influence of synthetic conditions in generating
assemblies with rich structural variations has been demon-
strated by us as well as others previously.
[7]
Among the auxiliary ligands, azides are unique with
reference to their bridging modes in connecting metal centers,
especially Cu
II
, thus generating a plethora of structures of
relevance in magneto chemistry.
[8]
Such systems provide ideal
test systems for understanding the basics of magnetic inter-
actions in extended systems.
[9]
While Cu
II
magneto chemistry of
phenoxo bridged
[10]
Schiff bases or azido bridged
[11]
systems
individually are plenty in literature, multinuclear Cu
II
systems
involving both phenoxo and azido bridges are rather scarce.
[12]
The reported systems involving both phenoxo and azido
bridges involve tetranuclear copper complexes involving sale-
n,
[12a]
salpn,
[12b]
and salophen,
[12c]
as Schiff bases, where salen =
N,N’-Bis(salicylidene)ethylenediamine; salpn = N,N’-bis(salicyli-
dene)-1,3-propylenediamine; salophen = N,N’-bis(salicylidene)-
1,2-diaminobenzene. While the salen system has been charac-
terized both structurally and magnetically, the salpn and
salophen systems have been characterized only structurally.
[a] P. Pandey, Dr. Nidhi Dwivedi, Dr. Sailaja S. Sunkari
Department of Chemistry,
Mahila MahaVidyalaya,
Banaras Hindu University
Varanasi 221005, India
E-mail: sunkari.s7@gmail.com
[b] Dr. Goulven Cosquer, Prof. Masahiro Yamashita
Department of Chemistry,
Graduate School of Science,
Tohoku University
6-3 Aramaki-Aza-Aoba, Sendai 980-8578, Japan
[c] Dr. Goulven Cosquer, Prof. Masahiro Yamashita
3 CREST, JST
4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
[d] Prof. Masahiro Yamashita
WPI Research Center,
Advanced Institute for Materials Research Tohoku University,
2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
[e] Prof. Masahiro Yamashita
School of Materials Science and Engineering
Nankai University,
Tianjin 300350, China
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/slct.201801820
FullPapers DOI:10.1002/slct.201801820
10311 ChemistrySelect 2018, 3, 10311 – 10319 © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim