Use of Cu(II)-di-Schiff bases as metalloligands in the formation of complexes with Cu(II), Ni(II) and Zn(II) perchlorate

Article abstract of DOI:10.1016/j.poly.2013.08.021

One linear homo-metallic trinuclear [{CuL¹(CH ₃OH)}₂Cu(ClO₄)₂] (1); five trinuclear hetero-metallic; bent [(CuL¹)₂Ni(H ₂O)₂](ClO₄)₂·H₂O (2), linear [(CuL¹)₂Zn(ClO₄)₂] (3), bent [{CuL²(ClO₄)}{CuL²(CH₃OH)} Ni(CH₃OH)₂](ClO₄)·(CH ₃OH)·0.25(H₂O) (4), triangular [(CuL ²){CuL²(CH₃CN)}Ni(CH₃CN) ₂](ClO₄)₂ (5), triangular [(CuL ²)₂Ni(H₂O)₂](ClO₄) ₂·3H₂O (6) and one rare tetranuclear star-shaped [{CuL²(H₂O)}₂(CuL²)Zn](ClO ₄)₂·H₂O (7) complexes have been synthesized by reacting the "metalloligand", [CuL¹] or [CuL²] with corresponding metal perchlorate where the di-Schiff base ligands H₂L¹ = N,N′-bis(salicylidene)-1,3- propanediamine and H₂L² = (N,N′-bis(α- methylsalicylidene)-1,3-propanediamine. The structures of all the seven complexes have been determined by X-ray crystallography. Structural analysis shows that complexes 1-6 are discrete trinuclear species where phenoxido groups of two terminal "metalloligands" coordinate to a central Cu(II) in 1 or Ni(II) in 2, 4-6 or Zn(II) in 3. In 1 and 3 two trans axial positions of the central Cu(II) are weakly coordinated by the oxygen atoms of perchlorate anions and the molecules are linear. However, in 2, 4-6 two solvent molecules coordinate to the cis positions of the central Ni(II) to complete its distorted octahedral geometry that makes the molecules bent or triangular. On the other hand, complex 7 is a star-shaped tetranuclear species. In which three metalloligands bind a central Zn(II) ion through double phenoxido bridge.

Full text of DOI:10.1016/j.poly.2013.08.021

Polyhedron 65 (2013) 322–331
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Use of Cu(II)-di-Schiff bases as metalloligands in the formation
of complexes with Cu(II), Ni(II) and Zn(II) perchlorate
⇑
⇑
Saptarshi Biswas , Ashutosh Ghosh
Department of Chemistry, University College of Science, University of Calcutta, 92 A.P.C. Road, Kolkata 700 009, India
a r t i c l e i n f o
a b s t r a c t
1
Article history:
One linear homo-metallic trinuclear [{CuL (CH OH)} Cu(ClO ) ] (1); five trinuclear hetero-metallic; bent
3
2
4 2
Received 26 June 2013
Accepted 4 August 2013
Available online 14 August 2013
1
1
2
2
[
(CuL )
Ni(CH OH)
triangular [(CuL )
Zn](ClO
ꢀH
with corresponding metal perchlorate where the di-Schiff base ligands H
2
Ni(H
2
O)
2
](ClO
4
)
2
ꢀH
OH)ꢀ0.25(H
O) ](ClO
ꢀ3H
2
O
(2), linear [(CuL )
2
Zn(ClO
4 2
) ]
(3), bent [{CuL (ClO
4
)}{CuL (CH
3
OH)}
2
2
3
2
](ClO
4
)ꢀ(CH
3
2
O) (4), triangular [(CuL ){CuL (CH
3
CN)}Ni(CH
3
CN) ](ClO
2
4
)
2
(5),
2
2
2
2
Ni(H
2
2
4
)
2
2
O (6) and one rare tetranuclear star-shaped [{CuL (H
2
O)}
2
(CuL )-
1
2
4
)
2
2
O (7) complexes have been synthesized by reacting the ‘‘metalloligand’’, [CuL ] or [CuL ]
Keywords:
1
0
II
II
2
L = N,N -bis(salicylidene)-
2
,3-propanediamine and H L = (N,N -bis(a-methylsalicylidene)-1,3-propanediamine. The structures of
Ni Cu
2
complexes
complex
complex
2
0
1
II
II
Zn Cu
2
3
II
II
all the seven complexes have been determined by X-ray crystallography. Structural analysis shows that
complexes 1–6 are discrete trinuclear species where phenoxido groups of two terminal ‘‘metalloligands’’
coordinate to a central Cu(II) in 1 or Ni(II) in 2, 4–6 or Zn(II) in 3. In 1 and 3 two trans axial positions of the
central Cu(II) are weakly coordinated by the oxygen atoms of perchlorate anions and the molecules are
linear. However, in 2, 4–6 two solvent molecules coordinate to the cis positions of the central Ni(II) to
complete its distorted octahedral geometry that makes the molecules bent or triangular. On the other
hand, complex 7 is a star-shaped tetranuclear species. In which three metalloligands bind a central Zn(II)
ion through double phenoxido bridge.
Zn Cu
Di-Schiff base ligands
Crystal structures
Ó 2013 Elsevier Ltd. All rights reserved.
1
. Introduction
In the past several decades, the design and synthesis of polynu-
be homonuclear i.e. the second metal ion is also a Cu(II) or
heteronuclear i.e. it is other than Cu(II) ion. The molecular shapes
of the trinuclear complexes show an interesting trend; the homo-
nuclear Cu(II) complexes are usually linear [25–28] with some
exceptions [23,24]. However, in the hetero trinuclear complexes
when the bridging anionic co-ligands (nitrate, acetate, perchlorate
etc.) act as an additional bridge between two adjacent metal cen-
ters, the shape of the molecule is linear whereas the monodentate
anionic co-ligands (thiocyanate, dicyanamide, cyanate etc.) results
in a bent structure. On the other hand, when the counter anions are
non-coordinating or weakly coordinating such as perchlorate,
three ‘‘metalloligands’’ can coordinate to a central metal ion to
result in rather unusual star-shaped tetranuclear complexes
[17,20,21]. However, trinuclear complexes with such anions are
limited and hence no generalization on the shape of the trinuclear
molecules could be done.
clear transition metal complexes have been drawing the attention
of coordination chemists not only because of their variety of archi-
tectures and topologies as observed in the metal–organic frame-
works but also in many possible applications e.g. in catalysis
[
1,2], magnetism [3–6], electron transport processes [7] and sens-
ing [8]. There are various strategies to synthesize polynuclear
complexes; one of them is to use the neutral complex of divalent
transition metal ion with salen type N
2
O
2
donor tetradentate
0
di-Schiff base ligands (salen = N,N -ethylenebis(salicylidenei-
mine)). The oxygen atoms of the coordinated Schiff base are
capable of bridging another metal ion to form multinuclear com-
plexes in which these chelates act as ‘‘metalloligands’’ [9]. Among
the divalent first transition elements, Cu(II) forms the most stable
complexes with these Schiff bases [10–13] and therefore, these
neutral Cu-chelates have been used frequently to form complex
with another metal ions. In most of these complexes, the oxygen
atoms of two ‘‘metalloligands’’ coordinate to a second ion to result
in trinuclear complexes [14–28]. These trinuclear complexes can
As a part of our ongoing study in the development of homo- and
hetero-polynuclear complexes using Cu(II) chelate with salen type
Schiff bases and various anionic co-ligands, we would like to
investigate the preferred nuclearity and molecular shape of the
resulted complexes with non-coordinating perchlorate salts.
Herein, we report the synthesis and crystal structures of seven
1
⇑
Corresponding authors. Tel.: +91 94 3334 4484; fax: +91 33 2351 9755.
E-mail addresses: saptarshibiswas85@yahoo.com (S. Biswas), ghosh_59@yahoo.
complexes, two linear trinuclear [{CuL (CH
3
OH)}
2
Cu(ClO
4
)
2
] (1)
O)
1
1
and [(CuL )
2
Zn(ClO
4
)
2
] (3); two bent trinuclear [(CuL )
2
Ni(H
2
2
]
com (A. Ghosh).
0
277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2013.08.021

S. Biswas, A. Ghosh / Polyhedron 65 (2013) 322–331
323
2
2
ꢁ1
ꢁ1
(
(
(
(
(
ClO
4
)
2
ꢀH
2
O
(2) and [{CuL (ClO
OH)ꢀ0.25(H O) (4); two triangular [(CuL ){CuL
CN) ](ClO
6) and a rare star-shaped tetranuclear [{CuL (H
4
)}{CuL (CH
3
OH)}Ni(CH
3
OH)
2
]
N, 5.47%. UV–Vis (CH
3
CN): kmax(nm) (
e
, M cm ) = 600 (365), 356
2
2
ꢁ1
ClO
4
)ꢀ(CH
3
2
(7700), 268 (21150), 230 (42200). IR:
m
(C@N) = 1623 cm
,
(5), [(CuL2)
ꢀ3H
2
O
m(ClO
ꢁ
) = 1107 cm .
ꢁ1
CH
3
CN)}Ni(CH
3
2
4
)
2
2
Ni(H
2
2
2 4
O) ](ClO )
2
4
2
2
O)} (CuL )Zn]
2
Complex 2: Yield: 0.580 g. (58%). Anal. Calc. for C34
2
H38NiCu N
4-
1
0
ClO
4
)
2
ꢀH
2
O (7) where H
2
L = N,N -bis(salicylidene)-1,3-propanedi-
O
2
15Cl (999.37): C, 40.86; H, 3.83; N, 5.61. Found: C, 40.61; H, 3.87;
2
0
ꢁ1
ꢁ1
amine and H
2
L = (N,N -bis(
a
-methylsalicylidene)-1,3-propanedi-
N, 5.87%. UV–Vis (CH
3
CN): kmax(nm) (
e
, M cm ) = 1020 (30), 618
amine. It is to be noted that
a
compound having similar
(327), 347 (11925), 269 (36525), 232 (67125). IR:
m
(C@N)
ꢁ1
ꢁ
ꢁ1
composition to that of 1 has been reported earlier [29]. In that
compound the coordinated methanol molecules were not present.
Moreover, the coordination mode of the perchlorate ions was
different.
1619 cm
Complex 3: Yield: 0.638 g. (67%). Anal. Calc. for C34
(952.03): C, 42.89; H, 3.39; N 5.89. Found: C, 42.61; H, 3.47;
, m(ClO ) 1090 cm .
4
2 4-
H32ZnCu N
O
12Cl
2
ꢁ1
ꢁ1
N, 5.87%. UV–Vis (CH
3
CN): kmax(nm) (
e, M cm ) = 616 (319), 336
ꢁ
1
(
m
10770), 269 (33419), 235 (58020). IR:
m(C@N) 1619 cm ,
ꢁ
ꢁ1
(ClO
4
) 1097 cm .
2
. Experimental
2
.4. Synthesis of
2
.1. Starting materials
2
2
[{CuL (ClO
4
)}{CuL (CH
3
OH)}Ni(CH
CN)}Ni(CH CN) ](ClO
O)}
3
OH)
2
](ClO
4
)ꢀ(CH OH)ꢀ0.25H
3
2
O (4),
O) ]
2 2
2
2
2
[
(
(CuL ){CuL (CH
ClO O (6) and [{CuL (H
ꢀ3H
3
3
2
2
4
)
2
2
(5), [(CuL )
2
Ni(H
The salicylaldehyde, 2-hydroxyacetophenone and 1,3-propane-
)
4 2
2
2
2
(CuL )Zn](ClO
4 2
) ꢀH
2
O (7)
diamine were purchased from Lancaster and were of reagent grade.
They were used without further purification.
Caution! Perchlorate salts of metal complexes with organic li-
gands are potentially explosive. Only a small amount of material
should be prepared and it should be handled with care.
2
The ‘‘metalloligands’’ [CuL ] (1.174 g, 3 mmol) was dissolved in
4 2-
methanol (30 mL) and then 5 mL aqueous solution of Zn(ClO )
ꢀ
6H
3
2
O (0.375 g, 1 mmol) was added to the solution, stirred for
0 min and then allowed to stand overnight when green X-ray
quality single crystals of complex 7 appeared at the bottom of
the vessel. The crystals were isolated, washed with ether and dried
1
2
2
.2. Synthesis of the Schiff base ligands H
2
L and H
2
L and their
1
2
metalloligands [CuL ] and [CuL ]
in vacuum desiccator containing anhydrous CaCl
2
. Complexes 4–6
were obtained by following a similar procedure to that of 7, using
The two di-Schiff-base ligands, H
standard methods [10,11]. Briefly, 5 mmol of 1,3-propanediamine
0.42 mL) were mixed with 10 mmol of the required aldehyde (sal-
icylaldehyde (1.04 mL) or 2-hydroxyacetophenone (1.21 mL)) in
methanol (20 mL). The resulting solutions were refluxed for ca.
2
L1 and H
2
L2 were prepared by
2
‘
(
‘metalloligands’’ [CuL ] (0.782 g, 2 mmol) and Ni(ClO
0.365 g, 1 mmol) in various of solvents, methanol, acetonitrile
4
)
2
ꢀ6H
2
O
(
and acetone for complexes 4–6, respectively. The crystals which
separated on keeping the solution were green in color.
Compound 4: Yield: 0.836 g. (74%). Anal. Calc. for C42
H56.5Cl2-
2
h, and allowed to cool. The yellow colored methanolic solutions
were used directly for complex formation. To a methanolic solution
20 mL) of Cu(ClO O (1.852 g, 5 mmol), was added a metha-
ꢀ6H
nolic solution of H
respective precursors ‘‘metalloligands’’ [CuL ] [10] and [CuL ]
Cu
2
NiN 16.25 (1134.11): C, 44.88; H, 5.02; N, 4.94. Found C,
4
O
ꢁ1
4
5.11; H, 4.87; N, 5.17%. UV–Vis (CH
3
CN): kmax(nm) (
e
, M
-
(
4
)
2
2
ꢁ1
cm ) = 1004 (145), 608 (338), 333 (11685), 263 (27822) and
1
2
2
L
or H
2
L
(5 mmol, 10 mL) to prepare the
ꢁ1
ꢁ
ꢁ1
2
35 (51521). IR:
Complex 5: Yield: 0.710 g. (63%). Anal. Calc. for C44
(1124.59): C, 46.99; H, 4.39; N, 8.72. Found: C, 46.61; H,
m
(C@N) = 1594 cm
,
m(ClO
4
) = 1096 cm
.
1
2
2 7-
H49NiCu N
[
11] as reported earlier (Scheme 1).
O
12Cl
2
ꢁ1
ꢁ1
4
.61; N, 8.87%. UV–Vis (CH
3
CN): kmax(nm) (e, M cm ) = 1004
1
1
2
(
.3. Synthesis of [{CuL (CH
3
OH)}
2
Cu(ClO
4 2 2 2 2
) ] (1), [(CuL ) Ni(H O) ]
(
150), 608 (350), 333 (13530), 263 (31676) and 233 (58407). IR:
1
4 2
ClO ) ꢀH
2
O (2) and [(CuL )
2
Zn(ClO ] (3)
)
4 2
ꢁ1
ꢁ
ꢁ1
m
(C@N) 1596 cm
Compound 6: Yield: 0.588 g. (54%). Anal. Calc. for C38
NiN 17 (1091.51): C, 41.81; H, 4.62; N, 5.13. Found: C, 41.63; H,
.87; N, 5.09%. UV–Vis (CH
112), 608 (261), 333 (12500), 264 (30790) and 235 (55277). IR:
, m(ClO ) 1097 cm .
4
2
H50Cl Cu2-
1
The ‘‘metalloligands’’ [CuL ] (0.688 g, 2 mmol) was dissolved in
4
O
methanol (30 mL) and then 5 mL aqueous solution of Cu(ClO
4
)
2-
ꢁ1
ꢁ1
4
(
3
CN): kmax(nm) (e, M cm ) = 1004
ꢀ
2
6H O (0.370 g, 1 mmol) was added to the solution, stirred for
3
0 min and then allowed to stand overnight when brown X-ray
quality single crystals of complex 1 appeared at the bottom of
the vessel. The crystals were isolated, washed with ether and dried
ꢁ1
ꢁ
ꢁ1
m
(C@N) = 1593 cm
Compound 7: Yield: 0.965 g. (67%). Anal. Calc. for C57
17Zn (1434.05): C, 47.74; H, 4.64; N, 5.86. Found: C, 47.81; H,
, m(ClO ) = 1086 cm .
4
H
2
66Cl Cu3-
N
4
6
O
in vacuum desiccator containing anhydrous CaCl
and 3 were obtained by following a similar procedure to that of
but Ni(ClO (0.365 g, 1 mmol) or Zn(ClO ꢀ6H
ꢀ6H
0.375 g, 1 mmol) were used respectively, for complexes 2 and 3
instead of Cu(ClO O. The crystals which separated on keep-
2
. Complexes 2
ꢁ1
ꢁ1
.87; N, 5.67%. UV–Vis (CH
3
CN): kmax(nm) (e, M cm ) = 608
(
m
220), 330 (13920), 267 (35280) and 228 (67880). IR:
1
(
,
4
)
2
2
O
4
)
2
2
O
ꢁ1
ꢁ
ꢁ1
(C@N) = 1597 cm
, m(ClO ) = 1089 cm .
4
4
)
2
ꢀ6H
2
2.5. Physical measurements
ing the solution were green in color.
Complex 1: Yield: 0.778 g. (77%). Anal. Calc. for C36
14 (1014.27): C, 42.63; H, 3.98; N, 5.52. Found: C, 42.81; H, 3.87;
H
2 3 4-
40Cl Cu N
Elemental analyses (C, H and N) were performed using a
Perkin-Elmer 2400 series II CHN analyzer. IR spectra in KBr pellets
O
ꢁ1
(
4000–500 cm ) were recorded using a Perkin-Elmer RXI FT-IR
R
R
spectrophotometer. Electronic spectra (1200–200 nm) were re-
corded in a Hitachi U-3501 spectrophotometer in acetonitrile
solution.
R
R
N
N
N
N
Cu
OH HO
O
O
2.6. Crystal data collection and refinement
1
R = H, CuL1
R = H, H L
2
2
2
Suitable single crystals of all the complexes were mounted on a
R = CH , H L
R = CH , CuL
3
3
2
Bruker-AXS SMART APEX II diffractometer equipped with
a
Scheme 1. Ligands and ‘metalloligands’ used in this work.
graphite monochromator and Mo K (k = 0.71073 Å) radiation.
a

3
24
S. Biswas, A. Ghosh / Polyhedron 65 (2013) 322–331
The crystals were positioned at 60 mm from the CCD. 360 frames
were measured with a counting time of 10s. The structures were
solved using Patterson method by using the SHELXS 97. Subsequent
difference Fourier synthesis and least-square refinement revealed
the positions of the remaining non-hydrogen atoms. Non-hydro-
gen atoms were refined with independent anisotropic displace-
ment parameters. Hydrogen atoms were placed in idealized
positions and their displacement parameters were fixed to be 1.2
times larger than those of the attached non-hydrogen atom. Suc-
cessful convergence was indicated by the maximum shift/error of
lid was found to be complex 7. On the other hand, with an aim to
obtain a star-shaped tetranuclear complex with Ni(II) as central
2
metal ion, we increased the proportion of [CuL ] up to the molar
2
ratios of nickel salt:[CuL ] = 1:4 using methanol as solvent but
the resulted species was the trinuclear complex 4. As there are
two cis coordinated solvent molecule in the central Ni(II) ion of
4, we presumed that they probably prevented the chelation of an-
other molecule of metalloligand. We therefore, used two other sol-
vent mixtures (acetonitrile and acetone) in order to get
II
II
tetranuclear Cu
3
Ni complex but in both the cases only the trian-
2
2
0
.001 for the last cycle of the least squares refinement. Absorption
gular complexes [(CuL ){CuL (CH
3 3
CN)}Ni(CH CN)
](ClO )
2 4 2
(5),
2
corrections were carried out using the SADABS program [30]. All cal-
culations were carried out using SHELXS 97 [31], SHELXL 97 [32], PLATON
[(CuL )
2
Ni(H
2
O)
2
](ClO
4
)
2
ꢀ3H
2
O (6) were formed. Similarly, we also
2
tried to prepare a tetranuclear species with [CuL ] precursor and
Cu(II) as central metal ion on changing the molar ratios of Cu-
salt:[CuL ] as well as the solvent systems but in all cases only
9
9 [33], ORTEP-32 [34] and WINGX system Ver-1.64 [35]. Data collec-
2
tion and structure refinement parameters and crystallographic
data for the seven complexes are given in Table 1.
the linear trinuclear complex which was reported earlier [36]
was isolated.
Besides elemental analysis, all the complexes were initially
characterized by IR spectra. The ‘‘metalloligands’’ were neutral
and obviously they have not any counter anions, whereas all the
complexes, 1–7 contain perchlorate anions which are easily de-
tected by the appearance of the characteristic intense peak in the
IR spectra in the range of 1086–1107 cm . The rest of the spectral
patterns and band positions of all the complexes are very similar to
the corresponding ‘‘metalloligands’’. The azomethine m(C@N)
3
. Results and discussion
3.1. Synthesis, IR and UV–Vis absorption considerations
L1 and H
L and its Cu complexes
2
II
ꢁ1
The di-Schiff base ligands H
2
2
1
2
[
[
CuL ] and [CuL ] were synthesized using the reported procedures
10,11]. [CuL ] on reaction with Cu(ClO
1
4
)
2
ꢀ6H
2
O, Ni(ClO
4
)
2
ꢀ6H
2
O
O
and Zn(ClO
4
)
2
ꢀ6H O separately in a 2:1 M ratios in CH
2
3
OH-H
2
group of the Schiff base appears at 1623, 1619, 1622, 1594, 1596,
1
ꢁ1
(
6/1, v/v) medium resulted in the trinuclear complexes [{CuL (CH3-
1593 and 1597 cm for complexes 1–7, respectively. In the IR
1
1
OH)}
Zn(ClO
2
Cu(ClO
4
)
2
] (1), [(CuL )
2
Ni(H
2 2
O) ](ClO
4
)
2
ꢀH
2
O (2) and [(CuL )2-
spectra of the complexes 1, 2, 5, 6 and 7, there is a broad band near
ꢁ1
4
2
) ] (3) by self-assembly (see Scheme 2). All three trinuclear
3434, 3440, 3443, 3449 and 3450 cm due to the O–H stretching
of the crystallized water/methanol molecule.
complexes are formed by the coordination of two phenoxido oxy-
gen atoms from each of the two terminal [CuL ] units to the central
Cu(II) (for 1), Ni(II) (for 2) and Zn(II) (for 3) but their geometries are
very different: complexes 1 and 3 are linear whereas complex 2 is
1
The electronic spectra of all the complexes have been measured
in acetonitrile solution. The spectra of complex 1 display a broad
absorption band near 600 nm. The position of this band is consistent
with the observed square-based geometry around the copper cen-
2
bent. On the other hand, [CuL ] on reaction with Ni(ClO
4
)
2 2
ꢀ6H O,
1
Zn(ClO
4
)
2
ꢀ6H
O medium resulted in the bent trinuclear [{CuL (ClO
OH)}Ni(CH OH) ](ClO OH)ꢀ0.25(H O) (4), star-
)ꢀ(CH
shaped tetranuclear [{CuL (H O)} (CuL )Zn](ClO O (7) and
ꢀH
] [36] species. In order to isolate a trinuclear
2
O and Cu(ClO
4
)
2
ꢀ6H
2
O separately in 2:1 M ratios in
ter. However, the band is broader compared to [CuL ] probably
2
CH OH-H
3
2
4
)}
due to the presence of different types of environments in the central
2
{CuL (CH
3
3
2
4
3
2
and terminal Cu(II). On the other hand in complex 2, a broad band is
2
2
3
3
observed at 618 nm for both Cu(II) and Ni(II) ( T1g
A2g). Another
2
2
4
)
2
2
2
3
4 2
linear [(CuL )Cu(ClO )
weaker broad band at 1020 nm is assignable to the transition T2g-
2
3
species with central zinc ion and terminal metalloligand [CuL ], we
decreased the proportion of [CuL ] in the reaction mixture but even
when the molar ratio of zinc salt:[CuL ] was 1:1, the separated so-
A2g for Ni(II). This value is in agreement with the literature value
2
for octahedral Ni(II) compounds [37]. The d–d transition band of
complex 3 was observed at 616 nm for Cu(II). The intense bands
2
Table 1
Crystal data and refinement details of the complexes 1–7.
Complex
Formula
1
2
3
4
5
6
7
C
36
H
40Cl
2
Cu
3 4
N O
14
C
34
H
38Cu
2
NiN
4
O
15Cl
2
C
34
H
32Cu
2 4
ZnN O
12Cl
2
C
2
42Cu NiCl
2
4
N H
56.5
O
76.25
C
44
H
49Cu
2
NiN
7
O
12Cl
2
C
38
H
50Cu
2
Cl
2
NiN
4
O
17
C
57
H
66Cu
3
O
17ZnCl N
2 6
Formula Weight 1014.27
999.37
monoclinic
P2 /n
11.342(5)
22.117(5)
15.545(5)
90
94.678(5)
90
3887(2)
4
952.03
monoclinic
P2 /n
9.028(5)
11.767(5)
17.300(5)
90
104.234(5)
90
1781(1)
2
1131.08
monoclinic
P2 /n
10.990(5)
34.611(5)
13.578(5)
90
100.959(5)
90
5071(3)
4
1124.59
monoclinic
P2 /c
20.59(2)
11.989(13)
22.569(16)
90
121.25(6)
90
4763(8)
4
1091.51
monoclinic
C2/c
19.244(5)
13.025(5)
15.516(5)
90
93.299(5)
90
1434.05
triclinic
P1ꢀ
Crystal System
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P2 /c
10.586(5)
13.306(5)
14.847(5)
90
107.841(5)
90
1990.7(14)
2
1
1
1
1
1
12.292(5)
15.262(5)
18.500(5)
69.906(5)
78.534(5)
69.480(5)
3040(2)
2
a
(°)
b (°)
(°)
c
3
V (Å )
3883(2)
4
1.850
Z
D
calc (g cmꢁ3)
1.692
1.708
1.777
1.775
2.072
1.482
1.373
1.568
1.457
1.566
1.584
ꢁ
1
l
(mm
)
1.692
1.790
R
int
0.0667
5336
0.0593
7700
0.0805
3175
0.0799
9163
0.1872
8070
0.0419
3463
0.0291
12391
Unique data
Data with I > 2(I) 3385
4787
1875
4917
2949
1865
4827
R
1
0.0437
0.1156
1.027
0.0518
0.1534
1.037
0.0807
0.1959
1.047
0.0737
0.1920
1.028
0.1013
0.2348
0.952
0.1203
0.3242
1.207
0.0650
0.1920
1.056
wR
Goodness-of-fit
GOF) on F2
2
(

S. Biswas, A. Ghosh / Polyhedron 65 (2013) 322–331
325
ClO3
N
N
Z
O
O
X
Y
O
O
Cu
W
Cu
Cu
N
N
O
O
N
N
N
N
O
Cu
Cu
W
O
Ni
O
X
O
Cu
2
)
2
2
;
X= H
2
O, Y=Z= NIL
4
L 1
O
2
l
-
ClO3
:
4
5
6
; X= Z= CH OH, Y= ClO
3 4
C
C
i(
u
; X= CH CN, Y=Z= NIL
(
N
1
:
3
:
1
Cl
:
1
; W= MeOH
O
L
; X= H O, Y=Z= NIL
2
4
)
u
1
2
2
C
L=L for
2
, L for
4-
6
Cu...O for
R
5 and 6
R
R
N
N
R
Cu(ClO4)2
Methanol
N
N
O
N
N
OHOH
Cu
Cu
O
O
1
O
R = H, H L
1
2
2
)
2
C
R = H, CuL
R = CH , H L
O
4
u
L 1
2
3
2
l
R = CH , CuL
C
:
3
(
Ligands
n
:
Z
Zn
Metalloligands
2
:
(
C
1
L
u
3
2
lO
C
:1
4
)
2
OH2
N
O
N
O
2
Cl
Cu
O
O
O
N
O
O
O
N
N
Cu
Zn
Cu
O
O
Zn
O
N
N
N
O
Cu
Cu
O
H O
O
2
O
N
N
Cl
O
2
7
3
Scheme 2. Synthetic route to the complexes 1–7.
at about 356, 268, 230; 347, 269, 232 and 336, 269, 235 nm for com-
The coordination sphere of terminal Cu(1) atom is penta-coor-
dinated with square-pyramidal geometry. The equatorial plane is
formed by the two imine N atoms N(1) and N(2), with the distances
1.955(3) and 1.966(3) Å and the two phenoxido O atoms, O(1) and
O(2) of the Schiff base with the distances 1.958(2) and 1.947(2) Å,
respectively. An oxygen atom O(5) from a methanol coordinates to
the axial position at 2.329(3) Å (Fig. 1). The r.m.s deviation of the
four equatorial donor atoms is 0.022 Å with the metal atom
0.089(1) Å from the plane towards O(5) atom. The Addison param-
plexes 1–3 respectively, correspond to the ligand-to-metal charge
⁄
⁄
transfer,
p–p transition of aromatic rings and n–p transition,
respectively [38,39]. The absorption bands of the complexes 4–6
are more or less similar to each other. The d–d transition bands ap-
pear at 608 nm (for both Cu(II) and Ni(II)) and 1004 nm for Ni(II)).
⁄
The ligand-to-metal charge transfer,
p–p
transition of aromatic
⁄
rings and n–
p
transition bands are found near at 333, 263 and
2
35 nm, respectively. In complex 7, spin-allowed d–d transition
band for Cu(II) is observed at 608 nm. The ligand-to-metal charge
eter (
around the central atom;
and trigonal bipyramidal geometries, respectively) of Cu(1) is
s
= |b ꢁa|/60° where b and a are the two largest angles
⁄
⁄
transfer,
p–
p
transition of aromatic rings and n–
p
transition bands
s
= 0 and 1 for perfect square pyramidal
appears at 330, 267 and 228 nm, respectively.
0
.019, indicating its square pyramidal geometry [40].
The packing of the molecules is controlled by two types of H–
3
3
.2. Description of the structures
bonding interactions, namely O–HꢀꢀꢀO and C–HꢀꢀꢀO. Hydrogen
atom H(18) of methanol shows hydrogen bonding interaction with
O(13) to form a 2D network in crystallographic ‘bc’ plane (Fig. 2
and Table 4). This 2D sheets are further connected by C–HꢀꢀꢀO
interaction along crystallographic ‘a’ axis to form a 3D supramolec-
ular structure (Fig. 2 and Table 4).
1
.2.1. Complex 1: [{CuL (CH
3
OH)}
2
Cu(ClO
4 2
) ]
The discrete trinuclear unit of complex 1 is shown in Fig. 1 and
the bond parameters are given in Table 2 and Table 3. The complex
contains two [CuL ] units, one Cu(II) atom, two methanol
molecules and two perchlorate anions. The structure contains a
crystallographic inversion centre at central Cu(2) atom which is
six-coordinate being bonded to six oxygen atoms: four from two
1
In this context, it is to be mentioned that a similar compound
1
[
(CuL )
2
Cu](ClO
4
)
2
with slightly different composition has been
synthesized by reacting copper acetate, di-Schiff base ligand
‘
‘metalloligands’’ and two from perchlorate anions. The four phe-
(
(
H
2
L) and sodium perchlorate in 8:5:5 M ratios in methanol–water
a
a
noxido oxygen atoms O(1), O(1) , O(2) and O(2) (symmetry oper-
4:1, v/v) medium. In that compound, the coordinated methanol
ation a = 2 ꢁx,ꢁy,2 ꢁz) define the basal plane and oxygen atoms
molecules were not present and the perchlorate ions bridge each
terminal copper ion to the central one. The axial bond distances
of perchlorate oxygen atoms to the central Cu(II) in that compound
is shorter (2.488 Å) and the av. bond distance of four basally
a
of perchlorate ions [O(11) and O(11) ] coordinate weakly to the
elongated side to complete the distorted octahedral geometry
around Cu(2). Bond lengths are 1.933(2) Å to O(1), 1.942(2) Å to
O(2) and 2.748(5) Å to O(11).

3
26
S. Biswas, A. Ghosh / Polyhedron 65 (2013) 322–331
Table 3
Dimensions in the metal coordination sphere of both the complexes, angles (deg).
Complex 1
Complex 2
Atoms
Angles
Atoms
Angles
O(5)–Cu(1)–O(1)
O(5)–Cu(1)–O(2)
O(2)–Cu(1)–O(1)
O(5)–Cu(1)–N(1)
O(5)–Cu(1)–N(2)
O(1)–Cu(1)–N(1)
O(1)–Cu(1)–N(2)
O(2)–Cu(1)–N(1)
O(2)–Cu(1)–N(2)
N(1)–Cu(1)–N(2)
O(11)–Cu(2)–O(1)
O(11)–Cu(2)–O(2)
O(11)–Cu(2)–O(11)
93.03(12)
87.55(15)
77.65(9)
O(4)–Ni(1)–O(5)
O(4)–Ni(1)–O(6)
O(5)–Ni(1)–O(6)
O(1)–Cu(1)–O(2)
O(1)–Cu(1)–N(1)
O(1)–Cu(1)–N(2)
O(2)–Cu(1)–N(1)
O(2)–Cu(1)–N(2)
N(1)–Cu(1)–N(2)
O(3)–Cu(2)–O(4)
O(3)–Cu(2)–N(3)
O(3)–Cu(2)–N(4)
O(4)–Cu(2)–N(3)
O(4)–Cu(2)–N(4)
N(3)–Cu(2)–N(4)
O(1)–Ni(1)–O(2)
O(1)–Ni(1)–O(3)
O(1)–Ni(1)–O(4)
O(1)–Ni(1)–O(5)
O(1)–Ni(1)–O(6)
O(2)–Ni(1)–O(3)
O(2)–Ni(1)–O(4)
O(2)–Ni(1)–O(5)
O(2)–Ni(1)–O(6)
O(3)–Ni(1)–O(4)
O(3)–Ni(1)–O(5)
O(3)–Ni(1)–O(6)
171.33(16)
89.43(15)
94.61(18)
78.00(14)
91.93(17)
169.96(17)
168.00(17)
91.97(16)
97.97(19)
79.07(13)
92.37(16)
170.91(17)
171.31(16)
91.84(16)
96.71(18)
72.43(13)
95.58(13)
86.56(13)
90.55(16)
170.49(16)
164.49(13)
96.17(13)
90.74(16)
99.48(16)
72.83(13)
99.36(16)
91.46(16)
96.40(16)
92.60(13)
91.36(10)
167.38(12)
168.53(10)
91.32(11)
99.23(12)
77.64(13)
77.29(15)
180.00
102.36(13)
102.71(15)
78.37(9)
180.00
101.63(9)
180.00
a
a
O(11)–Cu(2)–O(1)
O(11)–Cu(2)–O(2)
a
O(2)–Cu(2)–O(1)
a
O(2)–Cu(2)–O(1)
a
O(2)–Cu(2)–O(1)
a
O(2)–Cu(2)–O(2)
Fig. 1. The structure of 1 with ellipsoids at 30% probability. The dotted bonds show
the weak Cu(2)ꢀꢀꢀO(11) axial interactions.
coordinated phenoxido atoms is longer (1.957 Å) compare to those
in 1 (1.938 Å).
Symmetry element a = 2 ꢁx,ꢁy,2 ꢁz for complex 1.
1
3.2.2. Complex 2: [(CuL )
2 2
Ni(H O)
](ClO )
2 4 2
ꢀH O
2
1
The asymmetric unit of the complex 2 contains two [CuL ]
units, one Ni(II) atom, three water molecules and two perchlorate
anions. The ORTEP view is shown in Fig. 3 and the bond distances
and angles are given in Table 2 and Table 3, respectively. Both
Cu(II) ions present a tetra-coordinated square planar geometry
where four donor atoms (two imine N atoms and two phenoxido
O atoms) are from di Schiff ligand. The bond distances around both
s
4
= [360° ꢁ(
gles around the central metal in the complex. The values are
.156 and 0.126 for Cu(1) and Cu(2), respectively, confirming a
a + b)]/141°, a and b (in °) being the two largest an-
0
slightly distorted square planer geometry for both metal centers.
The environment of the nickel ion is distorted octahedral both
in the bond lengths and bond angles (Table 2 and Table 3). The
hexa-coordinated Ni(II) ion has four donor phenoxido oxygen
atoms from two terminal [CuL ] moieties and two cis-coordinated
water molecules. The bond distances are in the range of 2.039(5)–
copper atoms are in the range of 1.934(3)–1.972(4) Å. The
s
4
value
= 1)
4
and a perfect square planar geometry (s = 0) with the formula:
[
41] measures the distortion between a perfect tetrahedron (s
4
1
2
.088(3) Å. Regarding the angles, three trans angles are 164.49(13),
Table 2
170.49(16) and 171.33(16) and the cis angles vary in the range of
7
Dimensions in the metal coordination sphere of both the complexes, angles (°).
2.43(13)–99.48(16).
Atoms
Distances
The packing of the complex 2 is controlled by two types of weak
supramolecular interactions; namely, cation–
p and hydrogen
Complex 1
Cu(1)–O(5)
Cu(1)–O(1)
Cu(1)–O(2)
Cu(1)–N(1)
Cu(1)–N(2)
Cu(2)–O(1)
Cu(2)–O(1)
Cu(2)–O(2)
2.329(3)
1.958(2)
1.947(2)
1.955(3)
1.966(3)
2.748(5)
1.933(2)
1.942(2)
bonding. These cation– interactions again are of two types: in-
p
tra-molecular and inter-molecular. For the intermolecular interac-
tion, the centroid of the phenyl ring (Cg) is located at a distance of
CgꢀꢀꢀCu(1) = 3.498 Å while for intra-molcular CgꢀꢀꢀCu(2) distance is
at 3.910 Å (Fig. 4). The CgꢀꢀꢀCu(1) interaction builds a 1D chain that
propagates diagonally to the crystallographic ac plane. The intra-
1
molecular cation–
p
interaction holds the two [CuL ] moieties clo-
Complex 2
Cu(1)–O(1)
Cu(1)–O(2)
Cu(1)–N(1)
Cu(1)–N(2)
Cu(2)–O(3)
Cu(2)–O(4)
Cu(2)–N(3)
Cu(2)–N(4)
Ni(1)–O(1)
Ni(1)–O(2)
Ni(1)–O(3)
Ni(1)–O(4)
Ni(1)–O(5)
Ni(1)–O(6)
ser and thus stabilized the bent structure. On the other hand, each
trinuclear unit forms H-bond with its neighboring trinuclear units
with the help of coordinated water molecules and perchlorate
anions to form a 1D chain along crystallographic a axis (Fig. 5
and Table 4). These two types of chains form a 2D sheet along
the crystallographic ac plane.
1.939(3)
1.947(3)
1.972(4)
1.953(5)
1.940(3)
1.934(3)
1.945(5)
1.957(4)
2.066(4)
2.074(3)
2.065(3)
2.088(3)
2.050(5)
2.039(5)
1
3
.2.3. Complex 3: [(CuL )
2 4 2
Zn(ClO ) ]
The discrete trinuclear unit of complex 3 is shown in Fig. 6 and
the bond parameters are given in Table 5. The complex contains
1
two [CuL ] units, one Zn(II) atom and two bridging perchlorate an-
ions. The structure contains a crystallographic inversion centre at
central Zn(1) atom. The central Zn(1) is six-coordinate being

S. Biswas, A. Ghosh / Polyhedron 65 (2013) 322–331
327
Fig. 2. Supramolecular H–bonding interaction of complex 1, 2D (left, view along crystallographic a axis) and 3D (right, view along crystallographic b axis) networks.
Table 4
Hydrogen bond dimensions of both the complexes 1 and 2.
D–HꢀꢀꢀA
D–H (Å)
HꢀꢀꢀA (Å)
DꢀꢀꢀA (Å)
\D-HꢀꢀꢀA (°)
Symmetry
1
1
2
2
2
2
2
O5–H18ꢀꢀꢀO13
C8–H8BꢀꢀꢀO12
O1W–H2O1ꢀꢀꢀO7
O6–H1O6ꢀꢀꢀO1W
O5–H1O5ꢀꢀꢀO11
O5–H2O5ꢀꢀꢀO8
O6–H2O6ꢀꢀꢀO14
0.61(7)
0.97(4)
0.7400
0.9100
0.67(7)
0.92(7)
0.72(7)
2.35(7)
2.51(4)
2.2500
1.9900
2.16(7)
2.15(7)
2.13(7)
2.902(7)
3.389(8)
2.812(6)
2.704(7)
2.828(6)
3.017(8)
2.840(10)
153(9)
151(3)
134.00
134.00
171(7)
157(5)
169(6)
x,1/2 ꢁy,1/2 + z
1 ꢁx,1/2 + y,3/2 ꢁz
. . .
ꢁ1 + x,y,z
. . .
. . .
. . .
Fig. 4. Intra-molecular and inter-molecular cation–
p
interactions in complex 2
forms a 1D chain.
1
.957(8) and 1.949(8) Å and the two phenoxido O atoms, O(1) and
O(2) of the Schiff base with the distances 1.940(5) and 1.935(5) Å,
respectively. An oxygen atom O(12) from a perchlorate coordinate
to the axial position at 2.561(8) Å (Fig. 6). The r.m.s deviation of the
four equatorial donor atoms is 0.163 Å with the metal atom
0
.019(1) Å from the plane towards O(12) atom. The Addison
parameter ( ) of Cu(1) is 0.01, indicating nearly perfect square pla-
s
ner geometry [40].
The packing of the molecules are controlled by intermolecular
Fig. 3. ORTEP View of the complex 2 with ellipsoids at 30% probability.
cation–p interaction, which forming a 1D polymeric chain with
centroid of the phenyl ring CgꢀꢀꢀCu(1) distance of 3.915 Å (Fig. 7).
bonded to four oxygen atoms, two from each of two ‘‘ligands com-
plex’’, together with two oxygen atoms of perchlorate anions. The
2
2
3.2.4. Complex 4: [{CuL (ClO
(CH
OH)ꢀ0.25(H
(ClO and complex 6: [(CuL )
4
)}{CuL (CH
3
OH)}Ni(CH
3
OH)
CN)}Ni(CH
ꢀ3H
2
](ClO
4
)ꢀ
b
b
2
2
four phenoxido oxygen atoms O(1), O(1) , O(2) and O(2) (symme-
3
2
O), complex 5: [(CuL ){CuL (CH
3
3
CN) ]
2
b
2
try operation = 1 ꢁx,1 ꢁy,1 ꢁz) define the basal plane and oxy-
4
)
2
2
Ni(H
2
O)
2
](ClO
)
4 2
2
O
b
2
gen atoms of perchlorate ions [O(11) and O(11) ] coordinate
The trinuclear structures of 4–6 contain the same two [CuL ]
units, one Ni(II) atom and two perchlorate anions. However, the
solvent molecules that coordinate to the central Ni(II) are different;
they are methanol, acetonitrile and water for complexes 4–6,
respectively. The ORTEP views of the complexes are shown in
Fig. 8. The environment of the nickel ion is distorted octahedral
both in the bond distances (Table 6) and bond angles (Table 7).
weakly to the elongated side to complete the distorted octahedral
geometry around Zn(1). Bond lengths are 2.080(6) Å to O(1),
2
.016(5) Å to O(2) and 2.262(6) Å to O(11).
The coordination sphere of terminal Cu(1) atom is penta-coor-
dinated with square-pyramidal geometry. The equatorial plane is
formed by the two imine N atoms N(1) and N(2), with the distances

3
28
S. Biswas, A. Ghosh / Polyhedron 65 (2013) 322–331
Fig. 5. Inter-molecular H-bonding interactions to form a 1D polymeric chain in complex 2.
The hexa-coordinated Ni(II) ions contain four donor atoms of
2
phenoxido oxygen from two terminal [CuL ] moieties and two
cis-coordinated methanol (for 4), acetonitrile (for 5) and water
molecules (for 6). The bond distances around Ni(II) are in the range
of 1.863(10) to 2.093(5) Å for all three complexes. Regarding the
angles, three trans angles are in the range of 173.8(2)–155.6(4)°
and the cis angles vary in the range of 74.4(4)–101.5(5)°.
In the three complexes, the coordinating environments of the
2
two [CuL ] moieties are considerably different although they all
possess penta-coordinated square-pyramidal geometry. In com-
plex 4, oxygen atoms of perchlorate ion (O71) and O7 of methanol
molecule coordinate to the axial positions of Cu(2) and Cu(1),
respectively. In complex 5, Cu(1) is axially coordinated through
2
O3 of the other [CuL ] moiety and in Cu(2) a nitrogen atom (N7)
Fig. 6. ORTEP view of the complex 3 with ellipsoids at 30% probability. Hydrogen
atoms are omitted for clarity.
of acetonitrile molecule is axially coordinated. The penta-coordi-
nated square-pyramidal geometry of both the copper atoms in
complex 6 is completed by the axial coordination of the oxygen
c
c
atom O2 and O2 ( = 2 ꢁx,y,1/2 ꢁz) of two symmetry related
Table 5
2
Bond distances (Å) and angles (°) around the metal centers in complex 3.
[CuL ] units in the molecule.
In the three structures an interesting trend has been found
regarding the shape of the trinuclear complexes depending upon
the coordinating ability of the solvent molecules which are cis-
coordinated to central Ni(II) atom. In complex 4, the av. Ni(II)–
Atoms
Distance (Å)
Atoms
Distance (Å)
Cu1–O1
Cu1–O2
Cu1–N1
Cu1–N2
1.940(5)
1.935(5)
1.957(8)
1.949(8)
Cu1–O12
Zn1–O1
Zn1–O2
Zn1–O11
2.561(8)
2.080(6)
2.016(5)
2.262(6)
3
OHCH distance of 2.065 Å is the longest one and the terminal
Cu(II) atoms are not connected by the phenoxido oxygen atoms
as is evident from the long separation (2.976(5) Å) between them.
Consequently, the shape of the molecule is angular. Whereas, in 6
Atoms
Angle (°)
Atoms
Angle (°)
O1–Cu1–O2
O1–Cu1–N1
O1–Cu1–N2
O1–Cu1–O12
O2–Cu1–N1
O2–Cu1–N2
O2–Cu1–O12
N1–Cu1–N2
O12–Cu1–N1
O12–Cu1–N2
80.3(2)
92.5(3)
167.1(3)
86.9(2)
166.5(3)
91.0(3)
103.4(2)
97.9(3)
86.0(3)
119.7(2)
O1–Zn1–O2
O1–Zn1–O11
O1–Zn1–O1
O1–Zn1–O2
O1–Zn1–O11
O2–Zn1–O11
O2–Zn1–O11
O2–Zn1–O2
O11–Zn1–O11
75.1(2)
91.9(2)
180.00
104.9(2)
88.1(2)
91.1(2)
88.9(2)
180.00
180.00
b
the av. Ni–OH
Cu(II) are linked together through double
2
distance (1.915 Å) is the shortest and the terminal
-phenoxido bridge
b
l
3
b
b
with a bond distance of 2.590(8) Å that makes the shape of the
molecule triangular. On the other hand, in complex 5, the av.
b
Ni(II)–NCCH
distance (2.048 Å) is intermediate and the two termi-
-phenoxido
3
b
nal Cu(II) are joined together through only one
l
3
bridge with longer bond distance of 2.726(11) Å. These differences
Symmetry operation b = 1 ꢁx,1 ꢁy,1 ꢁz.
in bridging modes is also reflected in CuꢀꢀꢀCu distances which are
4
.027(2), 3.897(5) and 3.501(3) Å for complexes 4–6, respectively.
Therefore, we may infer that in these complexes, shorter is the cis
2
Ni(II)–S (S = solvent) distances, the two terminal [CuL ] units come
closer forming more in number as well as stronger bridges be-
tween them.
2
2
3
.2.5. Complex 7: [{CuL (H
2
O)}
2
(CuL )Zn](ClO
4 2
) ꢀH
2
O
2
The structure of 7 contains a discrete, independent [{CuL (H2-
(CuL )Zn] cation and two perchlorate anions. The structure
2
2+
O)}
2
of the cation is shown in Fig. 9. The selected bond lengths and an-
2
gles are summarized in Table 8. The structure of the [{CuL (H2-
2
2+
2
2
2 2
O)} (CuL )Zn] cation involves two [CuL (H O)] and one [CuL ]
moieties surrounding a zinc cation. The zinc ion is six-coordinate
being bonded to three pairs of oxygen atoms from each ‘ligand
complex’. Thus the zinc ion bridges three copper atoms each
Fig. 7. Cation–
graphic a axis.
p interactions in (3) to form a 1D polymeric chain along crystallo-

S. Biswas, A. Ghosh / Polyhedron 65 (2013) 322–331
329
Fig. 8. ORTEP View of the complexes 4–6 (left to right) with ellipsoids at 30% probability. Hydrogen atoms are omitted for clarity.
through two phenoxido oxygen atoms. The environment of the
Zn(II) ion can be described as a considerably distorted octahedron.
There are four short Zn–O bonds to O(1), O(4), O(5) and O(6) with
distances in the range 1.990(6)–2.087(6) Å, and two longer bonds
Zn–O(2) = 2.561(7) and Zn–O(3) = 2.269(6) Å. The bond angles also
show significant deviations from the ideal octahedral geometry.
Thus, the trans angles are lower than 180° (168.6(2)°, 176.2(2)°
and 141.0(2)°, Table 8) and the cis angles vary in a wide range
ent from the dihedral angles (17.07°) between the two planes,
N(1)–Cu(1)–O(1) and N(2)–Cu(1)–O(2) compare with 0° for a per-
fectly square-planar arrangement and 90° for a perfect tetrahedral
arrangement.
A CSD search reveals that at least 25 trinuclear homometallic
2 2
Cu(II) complexes with salen type N O donor ligands have been re-
ported. Of them, 21 are linear and rests are bent. It is to be noted
that the coordination sphere of the central Cu(II) is very important
to determine the shape of the molecule. When the central copper
atom is bonded only with the four oxygen atoms of two ligand
complexes in a square planar environment, the geometry is
(
from 67.1(2)° to 112.1(2)°, Table 8). The distances between the
Zn and three Cu(II) are almost equal (Zn(1)ꢀꢀꢀCu(1) = 3.074(2) Å,
Zn(1)ꢀꢀꢀCu(2) = 3.098(2) Å and Zn(1)ꢀꢀꢀCu(3) = 3.150(2) Å). The
CuꢀꢀꢀCu distances are 3.683(2) (for Cu(1)ꢀꢀꢀCu(2)), 5.687(3) (for
Cu(1)ꢀꢀꢀCu(3)) and 6.026(3) Å (for Cu(3)ꢀꢀꢀCu(2)).
2
Table 7
The geometry of Cu(3) and Cu(2) in the two [CuL (H
2
O)] moie-
Bond angles (°) around the metal centers in complexes 4–6.
ties is best described as square pyramidal with the four coordinat-
ing atoms from the di-anionic Schiff base ligand in the basal plane
and a weakly coordinated water molecule in one of the axial sites.
Atoms
4
5
6
Angles
Angles
Angles
The metal atoms Cu(3) and Cu(2) deviated from the N
2
O
2
basal
O(1)–Cu(1)–O(2)
O(1)–Cu(1)–O(7)/O(3)/O(2)
O(1)–Cu(1)–N(1)
O(1)–Cu(1)–N(2)
O(2)–Cu(1)–O(7)/O(3)/O(2)
O(2)–Cu(1)–N(1)
81.1(2)
97.0(2)
88.7(3)
170.2(3)
107.8(3)
161.1(3)
89.1(2)
89.1(3)
86.0(3)
100.6(6)
95.5(3)
81.9(2)
89.6(2)
162.1(2)
168.2(2)
89.7(2)
83.3(3)
89.4(3)
99.2(3)
100.7(3)
75.2(2)
88.8(2)
158.6(2)
97.3(2)
98.4(2)
84.3(2)
88.6(2)
95.6(2)
173.0(2)
75.6(2)
173.8(2)
93.0(2)
98.1(2)
96.9(2)
87.9(2)
–
81.4(4)
70.8(4)
91.6(5)
160.8(5)
67.2(4)
163.2(5)
90.5(5)
96.1(4)
121.9(4)
100.4(6)
89.2(5)
83.8(4)
88.7(5)
172.3(5)
171.9(4)
89.2(5)
90.6(5)
92.3(6)
93.9(5)
98.2(5)
74.4(4)
84.2(4)
157.3(4)
96.7(5)
96.2(4)
79.0(4)
89.0(4)
170.3(5)
94.5(5)
77.5(4)
96.8(5)
173.1(5)
98.7(5)
100.4(4)
90.0(5)
–
82.5(4)
71.8(4)
90.2(6)
166.5(5)
66.6(3)
164.7(5)
89.9(5)
98.3(4)
115.3(4)
99.7(6)
–
–
–
–
–
–
c
c
plane 0.124(1) and 0.003(1) Å, respectively towards the axially
coordinated water molecule. The Addison parameters [40] 0.15
for Cu(3) and 0.01 for Cu(2) indicate that the distortion towards
the trigonal bipyramid geometry of Cu(3) is greater than Cu(2).
2
In the remaining [CuL ] unit, both the axial positions of copper
O(2)–Cu(1)–N(2)
c
O(7)/ O(3)/ O(2) – Cu(1)–N(1)
atom Cu(1) are vacant. Thus the geometry around Cu(1) is square
planar. The r.m.s. deviation (0.205 Å) of donor atoms from their
mean plane indicates a tetrahedral distortion. The metal atom is
c
O(7)/ O(3)/ O(2) – Cu(1)–N(2)
N(1)–Cu(1)–N(2)
O(3)–Cu(2)–O(71)/ N(7)
O(3)–Cu(2)–O(4)
O(3)–Cu(2)–N(3)
O(3)–Cu(2)–N(4)
O(4)–Cu(2)–N(3)
O(4)–Cu(2)–N(4)
O(4)–Cu(2)–O(71)/N(7)
O(71)/N(7)–Cu(2)–N(3)
O(71)/N(7)–Cu(2)–N(4)
N(3)–Cu(2)–N(4)
O(1)–Ni(1)–O(2)
O(1)–Ni(1)–O(3)/O(3)/O1W
O(1)–Ni(1)–O(4)/O(4)/O1W
O(1)–Ni(1)–O(5)/O(5)/O(1)
O(1)–Ni(1)–O(6)/O(6)/O(2)
O(2)–Ni(1)–O(3)/O(3)/O1W
O(2)–Ni(1)–O(4)/O(4)/O1W
O(2)–Ni(1)–O(5)/O(5)/O(2)
0
.001(1) Å from this plane. The tetrahedral distortion is also appar-
Table 6
Bond distances (Å) around the metal centers in complexes 4–6.
–
–
–
–
Atoms
Complex 4
Complex 5
Complex 6
Distances
Distances
Distances
Cu1–O1
Cu1–O2
Cu1–N1
1.930(5)
1.934(6)
1.981(7)
1.967(7)
2.426 (8)
2.029(5)
2.086(5)
2.093 (5)
2.024(5)
2.073(6)
2.057(5)
1.935(5)
1.916(5)
1.938(7)
1.979(7)
2.567(11)
1.906(11)
1.909(10)
1.951(12)
1.956(16)
2.726(11)
2.035(10)
2.081(12)
2.092(10)
2.006(9)
2.061(17)
2.035(12)
1.925(9)
1.919(10)
1.947(15)
1.925(11)
2.78(2)
1.784(8)
1.766(10)
1.811(14)
1.831(10)
2.590(8)
1.863(10)
2.002(8)
–
74.5(4)
101.5(5)
96.0(5)
155.6(4)
86.4(4)
98.3(4)
169.4(5)
76.9(3)
–
–
–
–
–
–
–
c
c
Cu1–N2
Cu1–O7/O3/O2c
Ni1–O1
c
c
Ni1–O2
Ni1–O3
Ni1–O4
Ni1–O5/N5/O1W
Ni1–O6/N6
Cu2–O3
Cu2–O4
Cu2–N3
c
–
O(2)–Ni(1)–O(6)
O(3)–Ni(1)–O(4)
O(3)–Ni(1)–O(5)
O(3)–Ni(1)–O(6)
O(4)–Ni(1)–O(5)
O(4)–Ni(1)–O(6)
O(5)–Ni(1)–O(6)
1.915(11)
–
–
–
–
–
–
Cu2–N4
Cu2–O71/N7
c
O1W–Ni(1)–O1W
88.0(5)
Symmetry operation c = 2 ꢁx,y,1/2 ꢁz for complex 6.
Symmetry operation c = 2 ꢁx,y,1/2 ꢁz for complex 6.

3
30
S. Biswas, A. Ghosh / Polyhedron 65 (2013) 322–331
central atom and the structure becomes linear [43]. However, the
monodentate coligands usually coordinate to the cis positions of
the central atom making the structure angular or triangular. In
the present system, two axial positions of central Cu(II) atom in
complex 1 are weakly coordinated by two perchlorate oxygen
atoms and in 3 the perchlorate ions act as bridging bidentate li-
gands between terminal Cu(II) and central Zn(II). Hence, both the
molecules are linear. On the other hand, in complexes 2 and 4–6,
in addition to the phenoxido oxygen atoms, two monodentate sol-
vent molecules (water in 2 and 6, methanol in 4 and acetonitrile in
5) coordinate to the cis positions of the central metal ion and con-
sequently the molecules are angular or triangular.
The star-shaped tetra-nuclear complexes MCu
3
in which the
hetero atom, M, is surrounded by three ‘‘metalloligands’’ of Cu(II)
are less common in monoatomic brides and are usually formed
with polyatomic bridging ligands such as oxalate, oxamato,
oximato etc. Using Cu(II) complexes of salen type di-Schiff bases
as metalloligands, six examples of single atom oxido bridged
star-shaped tetra-nuclear complexes have been reported. These
Fig. 9. ORTEP View of the complex 7 with ellipsoids at 30% probability. Hydrogen
atoms are omitted for clarity.
+
+
examples include three with M = Na [20,44,45], one with M = K
2
+
2+
[
46] and one for each with Cd [17] and Mn [21]. Four of these
Table 8
2
complexes are constituted by the ‘‘metalloligands’’ [CuL ] and
other two by aother metalloligand [Cu(acacen)] (where
acacen] = N,N -ethylenebis(acety1acetoniminato)). There is no
Bond distances (Å) and angles (°) around the metal centers in complex 7.
Atoms
Distance (Å)
Atoms
Distance (Å)
2ꢁ
0
[
Cu1–O1
Cu1–N1
Cu1–N2
Cu1–O2
Cu2–O3
Cu2–O4
Cu2–N3
Cu2–N4
Cu2–O7
Cu3–O5
1.951(6)
1.983(8)
1.966(7)
1.934(7)
1.896(6)
1.939(6)
1.969(8)
1.959(9)
2.697(18)
1.934(6)
Cu3–O6
Cu3–N5
Cu3–N6
Cu3–O8
Zn1–O1
Zn1–O2
Zn1–O3
Zn1–O4
Zn1–O5
Zn1–O6
1.971(6)
1.991(9)
1.945(9)
2.466(11)
1.990(6)
2.561(7)
2.269(6)
2.002(6)
2.087(6)
2.076(6)
example of star-shaped tetranuclear ZnCu complex according to
the CCDC database (updated to December 2012) with any type
bridging ligands. Therefore, complex 7 of this article is the first
3
known example of star-shaped ZnCu
. Conclusions
The isolation of the seven complexes using neutral Cu(II) com-
3
complex.
4
0
1
Atoms
Angle (°)
Atoms
Angle (°)
2
plexes of N,N -bis(salicylidene)-1,3-propanediamine (H L ) and
0
2
2
N,N -bis(a-methylsalicylidene)-1,3-propanediamine (H L ) as met-
O1–Cu1–O2
O1–Cu1–N1
O1–Cu1–N2
O2–Cu1–N1
O2–Cu1–N2
N1–Cu1–N2
O3–Cu2–O4
O3–Cu2–N3
O3–Cu2–N4
O3–Cu2–O7
O4–Cu2–N3
O4–Cu2–N4
O4–Cu2–O7
N3–Cu2–N4
O15–Cu2–N3
O15–Cu2–N4
O6–Cu3–O8
O6–Cu3–N6
O6–Cu3–N5
O5–Cu3–O8
O5–Cu3–O6
83.3(3)
90.1(3)
166.4(3)
165.4(3)
91.7(3)
97.5(3)
81.9(3)
90.5(3)
168.2(3)
102.8(5)
168.8(3)
90.1(3)
88.4(5)
98.6(3)
85.2(5)
85.7(5)
104.6(3)
89.0(3)
161.1(3)
93.9(3)
82.0(2)
O5–Cu3–N5
O5–Cu3–N6
O8–Cu3–N5
O8–Cu3–N6
N5–Cu3–N6
O2–Zn1–O6
O3–Zn1–O4
O3–Zn1–O5
O3–Zn1–O6
O4–Zn1–O5
O4–Zn1–O6
O5–Zn1–O6
O1–Zn1–O2
O1–Zn1–O3
O1–Zn1–O4
O1–Zn1–O5
O1–Zn1–O6
O2–Zn1–O3
O2–Zn1–O4
O2–Zn1–O5
89.9(3)
170.1(3)
93.0(4)
84.5(4)
99.9(4)
168.6(2)
71.8(2)
176.2(2)
103.4(2)
104.8(3)
112.1(2)
76.0(2)
67.1(2)
83.0(2)
141.0(2)
100.8(2)
102.3(2)
72.1(2)
76.9(2)
109.3(2)
alloligands shows that this approach is very useful for the synthe-
sis of homo- and hetero-metallic complexes utilizing the bridging
capability of the phenoxido oxygen of the Schiff bases. Among
these seven complexes, six (1–6) are trinuclear, indicating that
these species are formed most commonly as was also found earlier.
The shape of the trinuclear species may vary from linear to trian-
gular depending upon various factors e.g. coordination mode of
the anionic coligand, coordination ability of the solvent molecules,
nature of the central metal ion etc. The other complex (7) which is
2
formed by coordination of three [CuL ] to a central Zn(II), is a rare
type of star-shaped tetranuclear species. We fail to isolate such a
star-shaped complex with Cu(II) or Ni(II) as central metal ion.
1
Moreover, [CuL ] does not produce such tetranuclear species with
none of the metal ion used here. Therefore, both the central metal
ions and the Schiff bases are important in determining the nuclear-
ity of the species obtained by this approach.
Acknowledgments
invariably linear. Moreover, when both the axial positions are coor-
dinated either by two weakly coordinating monodentate ligands
and by the bridging bidentate ligands the geometry is also linear.
However, if only one monodentate ligand coordinates to an axial
position of the central copper, its geometry may distort towards
trigonal bipyramidal and consequently the structure becomes bent
We thank CSIR, India for awarding a senior research fellowship
Sanction No. 09/028(0732)/2008-EMR-I] to S. Biswas. Crystallog-
[
raphy was performed at the DST-FIST, India-funded Single Crystal
Diffractometer Facility at the Department of Chemistry, University
of Calcutta. We are thankful to Prof. Michael G. B. Drew, School of
Chemistry, The University of Reading, U.K., for helpful discussions
on the crystallographic part.
[
23]. The structure can also be bent if the anionic coligands are
strongly coordinating and occupy the equatorial positions
24,42]. On the other hand, when the central metal ion is not a
[
Cu(II) and is hexa-coordinated, the coordination of two ligands
other than the four phenoxido atoms determine its geometry. A
bidentate bridging coligand that usually links the terminal metal
atom to the central one, coordinates to the trans positions of the
Appendix A. Supplementary data
CCDC 897775, 897776 and 932598–932602 contain the
supplementary crystallographic data for compounds 1, 2 and 3-7,

S. Biswas, A. Ghosh / Polyhedron 65 (2013) 322–331
331
respectively. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax: +44 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
[23] J.M. Epstein, B.N. Figgis, A.H. White, A.C. Willis, J. Chem. Soc., Dalton Trans.
1974) 1954.
(
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