Antiferromagnetic Mixed-Valence Cu(I)-Cu(II) Two-Dimensional Coordination Polymers Constructed by Double Oximato Bridged Cu(II) Dimers and CuISCN Based One-Dimensional Anionic Chains

Article abstract of DOI:10.1021/acs.cgd.5b00560

One dinuclear Cu(II) complex [Cu₂L²₂(EtOH)_0.5(ClO₄)](ClO₄) (1) has been synthesized by reacting an oxime-based tridentate Schiff base ligand, 3-[2-(diethylamino)ethylimino]butan-2-one oxime (HL²), with Cu^II(ClO₄)₂, whereas the reaction of another similar ligand, 3-[2-(dimethylamino)ethylimino]butan-2-one oxime (HL¹), and this ligand (HL²) with Cu^II(ClO₄)₂ in the presence of NaSCN yielded two rare mixed-valence Cu(I)-Cu(II) two-dimensional (2D) coordination polymers, ²_∞[{(Cu^II₂L¹₂)}{Cu^I₄(μ_1,3-SCN)₂(μ_1,1,3-SCN)₄}]_n (2) and ²_∞[{(Cu^II₂L²₂)}{Cu^I₂(μ_1,3-SCN)₂(μ_1,1,3-SCN)₂}]_n (3), respectively. The presence of SCN^- during the synthesis of the complexes induces reduction of a part of the Cu(II) to Cu(I) giving rise to these two novel mixed-valence 2D coordination polymers 2 and 3. All three complexes have been structurally and magnetically characterized. In complex 1, the square pyramidal Cu(II) atoms are joined by the double oximato bridges. On the other hand, the railroad track-like 2D sheet of 2 and stair-like arrangement of the 2D layer of 3 have been constructed by the connection of one-dimensional (1D) anionic chains ([Cu^I₂(SCN)₃]_n^n- in 2 and [Cu^I(SCN)₂]_n^n- in 3) through the cationic oximato bridged dinuclear units ([Cu^II₂L¹₂]²⁺ in 2 and [Cu^II₂L²₂]²⁺ in 3) via the sulfur atom of the thiocyanato ligand. In both complexes, Cu(I) and thiocyanato ligand form 1D infinite chains, but their different stoichiometry and coordination environments around the copper centers result in different structures. Variable-temperature (2-300 K) magnetic susceptibility measurements show that complexes 1-3 exhibit a strong antiferromagnetic interaction between two Cu(II) ions via N,O oximato bridges with J values -549.6, -578.7, and -663.8 cm^-1, respectively.

Full text of DOI:10.1021/acs.cgd.5b00560

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Article
Antiferromagnetic mixed-valence Cu(I)-Cu(II) 2D
coordination polymers constructed by double oximato
bridged Cu(II) dimers and CuISCN based 1D anionic chains
Lakshmi Kanta Das, Carmen Diaz, and Ashutosh Ghosh
Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.5b00560 • Publication Date (Web): 15 Jun 2015
Downloaded from http://pubs.acs.org on June 29, 2015
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Antiferromagnetic mixedꢀvalence Cu(I)ꢀCu(II) 2D coordination
polymers constructed by double oximato bridged Cu(II) dimers
and CuISCN based 1D anionic chains
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Lakshmi Kanta Dasa, Carmen Diazb and Ashutosh Ghosh*a
aDepartment of Chemistry, University College of Science, University of Calcutta, 92, APC
Road, Kolkataꢀ700009, India, eꢀmail: ghosh_59@yahoo.com
bDepartament de Química Inorgànica, Facultat de Química, Universitat de Barcelona, Martí i
Franquès 1ꢀ11, 08028 Barcelona, Spain.
ABSTRACT
One dinuclear Cu(II) complex [Cu2L2 (EtOH)0.5(ClO4)](ClO4) (1) has been synthesized by
2
reacting an oximeꢀbased tridentate Schiff base ligand, 3ꢀ[2ꢀ(diethylamino)ethylimino]butanꢀ
2ꢀone oxime (HL2) with CuII(ClO4)2 whereas the reaction of another similar ligand, 3ꢀ[2ꢀ
(dimethylamino)ethylimino]butanꢀ2ꢀone oxime (HL1) and this ligand (HL2) with CuII(ClO4)2
in presence of NaSCN yielded two rare mixedꢀvalence Cu(I)ꢀCu(II) 2D coordination
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polymers, ∞[{(CuII L1 )}{CuI4(µ1,3ꢀSCN)2(µ1,1,3ꢀSCN)4}]n (2) and ∞[{(CuII L2 )}{CuI2(µ1,3ꢀ
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SCN)2(µ1,1,3ꢀSCN)2}]n (3), respectively. The presence of SCN− during synthesis of the
complexes induces reduction of a part of the Cu(II) to Cu(I) giving rise to these two novel
mixedꢀvalence 2D coordination polymers 2 and 3. All three complexes have been
structurally and magnetically characterized. In complex 1, the square pyramidal Cu(II) atoms
are joined by the double oximato bridges. On the other hand, the railroad trackꢀlike 2D sheet
of 2 and stairꢀlike arrangement of 2D layer of 3 have been constructed by the connection of
n–
n–
1D anionic chains ([CuI2(SCN)3]n in 2 and [CuI(SCN)2]n in 3) through the cationic
oximato bridged dinuclear units ([CuII L1 ]2+ in 2 and [CuII L2 ]2+ in 3) via sulphur atom of
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2
thiocyanato ligand. In both complexes, Cu(I) and thiocyanato ligand form 1D infinite chains,
but their different stoichiometry and coordination environment around copper centers result
in different structures. Variableꢀtemperature (2–300 K) magnetic susceptibility measurements
show that complexes 1–3 exhibit a strong antiferromagnetic interaction between two Cu(II)
ions via N,O oximato bridges with J values −549.6, −578.7 and −663.8 cm−1 respectively.
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Introduction
The chemistry of mixedꢀvalence Cu(I/II) coordination complexes are gaining popularity due
to its great biological importance for their structural relevance with certain metalloꢀ
enzymes.1,2 In addition, they show interesting electronic properties3ꢀ6 as well as good
electrical conductivity and bistability.7,8 Copper(I) and copper(II) centers prefer different
geometries and stereochemistries and both oxidation states are highly labile and
stereochemically flexible,9ꢀ11 which is not usually the case for various other mixedꢀvalence
species e.g Fe, Co and Ru complexes. All these characteristics increase the possibility of
construction of coordination framework of Cu(I)/Cu(II) with diverse structural features and
topologies. However, there are great difficulties in controlling the final product with two
different oxidation states and thus the numbers of mixedꢀvalence copper complexes are
limited. The mixedꢀvalence copper complexes which are reported till date can largely be
grouped into four categories;12 (i) complexes containing Cu(II) cation and Cu(I) anion, (ii) biꢀ
and polynuclear complexes in which Cu(II) and Cu(I) centers bridged by polydentate ligands,
(iii) complexes containing Cu(II) and Cu(I) centers bridged by CN−/SCN−/SeCN−
pseudohalides and (iv) complexes with Cu(I) and Cu(II) ions enclosed in a cluster. The
general method for the synthesis of cyano, thiocyanato and selenocyanato Cu(II)ꢀCu(I)
complexes is the partial reduction of Cu(II) salts in the presence of a ligand
(CN−/SCN−/SeCN−) which serves both as a ligand and as a reducing agent.12ꢀ16 Such in situ
Cu(II) to Cu(I) reduction is a usual phenomenon when Cu(II) salts are subjected to high
energy closed vessel solvothermal reactions in presence of the ligand,17,18 but is a rare case at
room temperature open pot synthesis.19ꢀ21 The reduction leads to the formation of CuIX
(where X− = CN−/SCN−/SeCN−) based species which generates mixedꢀvalence polymeric
coordination framework with the help of Cu(II) and other ancillary ligands attached to the
Cu(II) ion.
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The linear triatomic pseudohalide, thiocyanate (SCN−), is an excellent versatile
ambidentate ligand with two donor atoms N and S. It can coordinate to metal ions both in
terminal and bridging coordination modes. The common bridging coordination modes of
thiocyanato ligand are ꢁ1,3ꢀNCS,22,23 ꢁ1,1ꢀNCS24 and ꢁ1,1ꢀSCN25 (Scheme 1, AꢀC). The rare
variety of coordination modes e.g. ꢁ1,1,3ꢀSCN26 and ꢁ1,1,1,3ꢀSCN27 (Scheme 1, DꢀE) have also
been reported in some complexes. It bridges Cu(I) and Cu(II) ions to form polymeric
complexes with different dimensionalities and topologies.25ꢀ29 The dimension and topology of
the final framework depend upon several factors. Firstly, the different binding modes of both
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thiocyanato and ancillary ligands furnish different coordination environment around both
Cu(I) and Cu(II) ion and this leads to the formation of various frameworks.28,29 Secondly, the
different dimensionalities of CuISCN based species influence the structure of polymers. As
for example, CuISCN based 1D chains are connected by Cu(II) moieties to construct 2D
polymer whereas CuISCN based 2D layers are associated with Cu(II) moieties to produce 3D
polymer.20,21,30 Finally, the nature, size and structure of the ancillary ligands attached to the
Cu(II) ion can also influence the resulting structure.21
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M
M
S
C N
N
C
A
S
N
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S
M
S
M
M
M
C
B
M
M
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N
C
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S
M
M N
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M
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E
Scheme 1. Different coordination modes of thiocyanato ligand.
In this paper, we report three new oximatoꢀbridged copper complexes by using two
oxime based monoꢀcondensed Schiff base ligands, 3ꢀ[2ꢀ(dimethylamino)ethylimino]butanꢀ2ꢀ
one oxime (HL1) and 3ꢀ[2ꢀ(diethylamino)ethylimino]butanꢀ2ꢀone oxime (HL2) having
different substitution in amine part. The reaction of copper(II) perchlorate with HL2 leads to
the formation of discrete dinuclear complex [Cu2L2 (EtOH)0.5(ClO4)](ClO4) (1). On the other
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hand, the reaction of copper perchlorate with either HL1 or HL2 in presence of SCN− at room
temperature leads to in situ Cu(II) to Cu(I) partial reduction generating two mixedꢀvalence
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Cu(I/II) 2D coordination polymers ∞[{(CuII L1 )}{CuI4(µ1,3ꢀSCN)2(µ1,1,3ꢀSCN)4}]n (2) and
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∞[{(CuII L2 )}{CuI2(µ1,3ꢀSCN)2(µ1,1,3ꢀSCN)2}]n (3) with different framework. Complex 2, in
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which the CuISCN based infinite chain is formed in an unprecedented manner, represents a
unique example of “supramolecular isomers” of a previously reported 3D mixedꢀvalence
coordination polymer.21 The structures and variableꢀtemperature magnetic susceptibility
measurement of complexes (1−3) is presented here in detail.
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Experimental section
Starting materials
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Diacetylmonoxime, N,Nꢀdimethylꢀ1,2ꢀethanediamine, N,Nꢀdiethylꢀ1,2ꢀethanediamine and
sodium thiocyanate were purchased from commercial sources and used as received.
Copper(II) perchlorate hexahydrate was prepared by the standard laboratory method; solvents
were of reagent grade and used without further purification.
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Caution! Perchlorate salts of metal complexes coordinated with organic ligands are
potentially explosive. Only a small amount of material should be prepared, and it should be
handled with care.
Syntheses of Schiff base ligands (HL1 and HL2)
The two monoꢀcondensed Schiff base ligands, 3ꢀ[2ꢀ(dimethylamino)ethylimino]butanꢀ2ꢀone
oxime (HL1) and 3ꢀ[2ꢀ(diethylamino)ethylimino]butanꢀ2ꢀone oxime (HL2) were prepared by
standard methods. 8 mmol of diacetylmonoxime (0.808 g) were mixed with 8 mmol of the
required amine (N,Nꢀdimethylꢀ1,2ꢀethanediamine (0.878 mL) or N,Nꢀdiethylꢀ1,2ꢀ
ethanediamine (1.120 mL)) in ethanol (20 mL). The resulting solutions were refluxed for ca.
5 h and allowed to cool. The yellow coloured ethanolic solutions were used directly for
complex formation.
Synthesis of complex [Cu2L2 (EtOH)0.5(ClO4)](ClO4) (1)
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An ethanolic solution of (20 mL) of CuII(ClO4)2·6H2O (1.480 g, 4 mmol) was allowed to
react with an ethanol solution of HL2 (4 mmol, 5 mL). The green coloured mixture was
stirred for 1 h at room temperature and it was filtered. The filtrate was allowed to stand at
open atmosphere. A prismatic shaped green (1) Xꢀray quality single crystals appeared at the
bottom of the vessel after 5 days. The crystal were then washed with diethyl ether and dried
in a desiccator containing anhydrous CaCl2, then characterized by elemental analysis,
spectroscopic methods and Xꢀray diffraction.
Complex 1: Yield: 1.318 g (88%). Anal. calc. for C21H42.5O10.5N6Cu2Cl2: C 33.85, H 5.75, N
11.28. Found: C 33.77, H 5.75, N 11.39 %. m. p. = 200°C. IR (KBr pallet, cm–1): 3473mb,
2979m, 1658w, 1525m, 1222m, 1101sb and 623m. UV/Vis (in (CH3CN): λmax in nm (ξmax in
M–1 cm–1) = 577 (1312), 429 (4750) and 282 (16030) nm.
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Syntheses of complexes
∞[{(CuII L1 )}{CuI4(µ1,3ꢀSCN)2(µ1,1,3ꢀSCN)4}]n (2) and
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∞[{(CuII L2 )}{CuI2(µ1,3ꢀSCN)2(µ1,1,3ꢀSCN)2}]n (3)
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To an ethanolic solution (20 mL) of copper(II) perchlorate hexahydrate (1.480 g, 4 mmol),
the ethanolic solution of HL1 (4 mmol, 5 mL) was added followed by the addition of an
aqueous solution (2 mL) of sodium thiocyanate (0.180 g, 2 mmol) to this solution. The
mixture was stirred for 1 h at room temperature and then filtered off. The green filtrate was
allowed to stand at open atmosphere resulting in the formation of green crystalline product
after 10 days. Needle shaped Xꢀray quality single crystals suitable for Xꢀray diffraction of 2
were grown in an ethanolic solution of the green mass by a slow diffusion of ether in a sealed
tube. Similarly, green needle shaped single crystals of 3 were obtained by following the same
procedure for 2, but using HL2 instead of HL1.
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Complex 2: Yield: 0.471 g (66%, based on metal). Anal. calc. for C22H32Cu6N12O2S6: C
24.69, H 3.01, N 15.71 %. Found: C 24.83, H 3.12, N 15.67%. m. p. = does not melt up to
300°C, above this temperature it starts to decompose. IR (KBr pallet, cm–1): 2901w, 2126sb,
2093sb, 1651w, 1509m and 1213m. UV/Vis (in CH3CN): λmax in nm (ξmax in M–1 cm–1) = 603
(1362), 420 (7650) and 278 (16290) nm.
Complex 3: Yield: 0.556 g (63%, based on metal). Anal. calc. for C24H40Cu4N10O2S4: C
32.64, H 4.57, N 15.86. Found: C 32.61, H 4.52, N 15.77 %. m. p. = 245°C. IR (KBr pallet,
cm–1): 2978m, 2112sb, 2091sb, 1651w, 1504m and 1217m. UV/Vis (in CH3CN): λmax in nm
(ξmax in M–1 cm–1) = 603 (1126), 419 (6210) and 280 (16300) nm.
Physical Measurements
Elemental analyses (C, H and N) were performed using a PerkinꢀElmer 2400 series II CHN
analyzer. IR spectra in KBr pellets (4000–500 cm–1) were recorded using a PerkinꢀElmer RXI
FTꢀIR spectrophotometer. Electronic spectra in acetonitrile were recorded in a Hitachi Uꢀ
3501 spectrophotometer. The magnetic measurements were carried out in the “Servei de
Magnetoquimica (Universitat de Barcelona)” on polycrystalline samples with a Quantum
Design SQUID MPMSXL magnetometer in an applied field of 7000 and 400 G in the
temperature ranges of 2–300 K and 2–30 K, respectively. The experimental magnetic
susceptibility data are corrected for the diamagnetism estimated from Pascal’s tables.31
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Crystallographic data collection and refinement
Suitable single crystals of each complex were mounted on a BrukerꢀAXS SMART APEX II
diffractometer equipped with a graphite monochromator and MoꢀKα (λ = 0.71073 Å)
radiation. The crystals were positioned at 60 mm from the CCD. Frames (360) were
measured with a counting time of 5 s. The structures were solved by Patterson method using
the SHELXS 97 program. The nonꢀhydrogen atoms were refined with anisotropic thermal
parameters. The hydrogen atoms bonded to carbon were included in geometric positions and
given thermal parameters equivalent to 1.2 times those of the atom to which they were
attached. Successful convergence was indicated by the maximum shift/error of 0.001 for the
last cycle of the least squares refinement. Absorption corrections were carried out using the
SADABS program.32 All the calculations were carried out using SHELXS 97,33 SHELXL
97,34 PLATON 99,35 ORTEPꢀ3236 and WINGX system verꢀ1.64.37 Data collection, structure
refinement parameters and crystallographic data for the three complexes (1−3) are given in
Table 1.
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Results and Discussion
Syntheses of the complexes
The Schiff base ligands HL1 and HL2 were synthesized using the reported procedures. When
the Schiff base ligand HL2 was allowed to react with copper perchlorate hexahydrate in EtOH
medium, it resulted in the dinuclear complex [Cu2L2 (EtOH)0.5(ClO4)](ClO4) (1). It is to be
2
to mentioned that the reaction of HL1 with copper perchlorate in EtOH medium also
produced a dinuclear Cu(II) complex [Cu2L1 (H2O)2](ClO4)2 which has been reported
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previously by other groups.21,38 In both complexes, the oximato oxygen atoms of Schiff base
ligand were deprotonated and coordinated to Cu(II). On the other hand, when HL1 and HL2
reacted with copper(II) perchlorate hexahydrate and sodium thiocyanate in EtOH medium,
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mixedꢀvalence Cu(I)ꢀCu(II) 2D coordination framework, ∞[{(CuII L1 )}{CuI4(µ1,3ꢀ
2
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SCN)2(µ1,1,3ꢀSCN)4}]n (2) and ∞[{(CuII L2 )}{CuI2 (µ1,3ꢀSCN)2(µ1,1,3ꢀSCN)2}]n (3) based on
2
2
double oximato bridged Cu(II) dimers were produced in both cases (Scheme 2). Here, the use
of sodium thiocyanate induced the partial reduction of Cu(II) to Cu(I) at room temperature,
giving rise to the mixedꢀvalence 2D coordination frameworks.
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N
O
O
N
N
II
Cu
II
Cu
N
N
N
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2D polymer (2)
Cu(ClO4)2:HL1
:SCN-(1:1:1)
X
Cu(ClO4)2:HL1
or HL2(1:1)
R R
N
O
O
N
N
N
N
II
Cu
N
II
-
X = H2O or EtOH or ClO4
Cu
N
OH
N
NR2
R
R
X
N
O
O
N
N
Cu(ClO4)2:HL2
:SCN-(1:1:1)
HL1 when R = -Me
HL2 when R = -Et
II
Cu
II
Cu
N
N
Dinuclear
(1)
N
S
C
N
Cu(I)
2D polymer (3)
Scheme 2. Formation of complexes (1−3).
It should be noted that using HL1 ligand, Mitra et. al. synthesized a mixedꢀvalence Cu(I/II)
3D coordination network by applying similar approach using methanol as solvent instead of
ethanol. The molecular building blocks [(CuII L1 ){CuI4(SCN)6}] of that 3D polymer have
2
2
identical chemical compositions to our 2D polymer (2) but their network structures and
topologies are completely different. Therefore, complex 2 represents an isomeric form of
reported 3D network and thus these two are “supramolecular isomers”. The crystal structure
and magnetic property of dinuclear complex, [Cu2L1 (H2O)2](ClO4)2) have been studied by
others21,38 However, as this complex is related to the other complexes reported in this paper,
we just mention it here but do not describe its structure and magnetic property.
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IR and UVꢀVis spectra of the complexes
The infrared spectra of complexes 1−3 show the characteristic bands of the coordinated
oxime based Schiff base ligands (Figures S1−S3, in Supporting Information). These display
strong and sharp absorption bands in the regions 1658−1651 and 1222−1213 cm–1 which can
be assigned to the ν(C=N) and ν(N−O) vibrational modes, respectively of the coordinated
Schiff base ligands. In addition, a couple of strong and mediumꢀintensity bands at ca. 1101
and 623 cm−1, readily confirming the presence of ionic perchlorate in complex 1. On the
other hand, complexes 2 and 3 exhibit intense doublets appearing in the regions 2126−2091
cm−1, confirm the presence of the bridging thiocyanato groups. In both cases, a strong and
broad peak at 2126 and 2112 cm–1 along with a shoulder at 2093 and 2091 cm–1 appeared in
the spectra of 2 and 3, respectively. The splitting of the thiocyanato band may be attributed to
the presence of two different types of SCN‾ anion in both the complexes.
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The electronic spectra of all three complexes are recorded in acetonitrile solution. The
complexes exhibit a broad absorption band in the visible region at 577, 603 and 603 nm for
1−3, respectively (Figure S4, in Supporting Information). These bands are attributed to d–d
transitions of Cu(II) ions in the square based environment. In addition, sharp, single
absorption bands are found near the respective wavelengths of 429, 420 and 419 nm for 1−3,
which can be attributed to ligandꢀtoꢀmetal charge transfer transitions. Moreover, absorption
bands at 282, 278 and 280 nm for 1−3, respectively, assignable to intraꢀligand charge transfer
transitions, are observed for all three complexes.
Structure descriptions of the complexes
The structure of 1 consists of cationic dinuclear unit of formula [Cu2L2 ]2+ (where HL2 is 3ꢀ
2
[2ꢀ(diethylamino)ethylimino]butanꢀ2ꢀone oxime) along with two perclorate anions and a
coordinated ethanol molecule with half occupancy. The dinuclear unit is shown in Figure 1,
while selected bond lengths and angles are summarized in Table 2. The two copper atoms
present different environments: one (Cu1) is a pentaꢀcoordinated square pyramid and the
other (Cu2) is a fourꢀcoordinated distorted square planar. The basal planes around both the
copper atoms are constituted by the three nitrogen atoms of one ligand and oxygen of a
second ligand from the tridentate Schiff base. However, one of the axial positions of Cu1 is
occupied by the oxygen atom (O31) of the ethanol solvent at a distance of 2.396(9) Å. The
four donor atoms around Cu1 are approximately planar showing r.m.s. deviations of 0.006 Å
while the metal atom (Cu1) is 0.115(1) Å from this plane towards the axially coordinating
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oxygen atom. The Addisons parameter (τ = 0.148) indicates a square pyramidal geometry
around Cu1 with a slight distortion. This value is 0 for the ideal square pyramid and 1 for the
trigonal bipyramid.39 On the other hand, in Cu2, there is slight tetrahedral distortion in the
square plane with r.m.s deviations of 0.033 Å for the donor atoms. The Cu2 atom deviates
0.075(1) Å from this plane. The Cu–O and Cu–N bond lengths of the two copper atoms in the
basal plane vary within a short range from 1.870(4) to 1.881(5) Å and from 1.905(6) to
2.104(7) Å, respectively.
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Figure 1. The structure of complex 1 with ellipsoids at 30% probability. Weak interaction is
−
shown by open bond. One nonꢀcoordinated ClO4 anion is not shown here. In this structure
both the copper atoms (Cu1 and Cu2) are divalent.
The Cu2 atom is weakly coordinated with oxygen atom of a perchlorate anion in its
axial position. Thus, the geometry of Cu2 may be viewed as distorted square pyramid by
considering the weak Cu2–O2 bond distance of 2.747(8) Å. The metals are separated by
3.652(1) Å in the dinuclear unit.
The structure of 2 is shown in Figure 2, while the selected bond lengths and angles are
summarized in Table 3. It contains a dinuclear cation [CuII L1 ]2+, being located on a
2
2
crystallographic inversion center and two [CuI2(SCN)3]− anionic fragments. The asymmetric
unit of it consists of half of the reported formula, [(CuIIL1)CuI2(SCN)3].
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Figure 2. The coordination environment of complex 2 with ellipsoids at 30% probability.
c
Symmetry transformation = −1−x,−y,−z. Here, the Cu1 is divalent while Cu2 and Cu3 are
monovalent.
The structure of dinuclear cation [CuII L1 ]2+ is comparable to that of 1, except the
2
2
axial positions of Cu(II) are occupied by Sꢀcoordinated SCN‾ ions located on the opposite
sides of the basal plane. Thus, the environments of the both copper atoms are square
pyramidal. The Addison parameter (τ) is 0.072 for the copper atom. Like 1, the basal plane
around Cu1 is constructed by the chelating tridentate N atoms of Schiff base and the oximato
oxygen (O11) of symmetry related ligand. The Cu−O and Cu−N bond distances are
comparable to those observed in 1 (see Table 1). The r.m.s. deviation of the four basally
coordinating atoms from the mean plane passing through them is 0.022 Å, while the metal
atom is 0.184(1) Å from this plane towards the axially coordinating sulphur atom. The axial
position is occupied by a S atoms (S1) of the µ1,1,3ꢀSCN ligand from the anionic part with a
Cu1−S1 distance of 2.713(2) Å. The Cu1···Cu1 separation in this dinuclear unit is 3.630 (1)
Å.
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nꢀ
Figure 3. Top: The 1D anionic chain, [CuI2(SCN)3]n is formed by Cu(I) and SCN¯ along
crystallographic ‘c’ axis. Bottom: The railroad trackꢀlike 2D sheet of polymer 2, constructed
by the connection of 1D chains by dinuclear cationic units via S atom of thiocyanato ligand
with in crystallographic ‘ac’ plane. Cu(I) and Cu(II) have been represented by green and
brown balls respectively.
The most interesting feature of the crystal packing of 2 is the formation of 1D anionic
chains formulated as [CuI2(SCN)3]nnꢀ constructed by two independent copper(I) ions, Cu2 and
Cu3 and three SCN‾ anions; one presents ꢁ1,3ꢀSCN bridging mode, while the rest two SCN‾
present a ꢁ1,1,3ꢀSCN coordination mode. The monovalent (Cu2) is tetrahedral with S3N
chromophore, whereas the coordination environment around the other monovalent (Cu3) is
trigonal planar with N2S chromophore. The tetrahedral environment around Cu2 is distorted
as confirmed by the τ4 index which is 0.882. The τ4 index is defined as τ4 = [360° − (α +
β)]/141°, with α and β (in °) being the two largest angles around the central metal in the
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compound with τ4 = 0 for a perfect square planar and τ4 = 1 for a perfect tetrahedron.40 The
CuI−S and CuI−N distances vary in the ranges 2.280(1)−2.508(1) Å and 1.890(2)−1.948(2) Å,
respectively. The CuI−S distances (2.280(1)−2.508(1) Å) are noticeably shorter than the
CuII−S distances (2.713(2) Å). The Cu2···Cu3 separation is 5.441 Å. The monovalent Cu2
and Cu3 atoms of the asymmetric unit are connected by a ꢁ1,1,3ꢀSCN ligand via N1 and S1,
respectively whereas those of two different units are linked by a ꢁ1,3ꢀSCN ligand through N3
and S3, respectively. Moreover, the Cu2 atoms of two different units form a CuI2S2 dinuclear
square grid by connecting the other ꢁ1,1,3ꢀSCN ligand through a pair of sulphur ends (S2)
while the Nꢀend (N2) connects the Cu3 atom of other unit. The shortest interꢀatomic distance
between two copper(I) within this dinuclear square grid is 2.823(1) Å which is slightly longer
than the sum of the van der Waals radii of copper(I) (2.8 Å). Thus, the connections of
monovalent copper ions by thiocyanato ligands furnish a 1D anionic chain. Finally, the
railroad trackꢀlike 2D sheet is constructed by the connection of the resulting anionic chains
through the divalent Cu(1) atom of dinuclear units via sulphur atom (S1) of ꢁ1,1,3ꢀSCN ligand
which connects all three metal atoms in asymmetric unit (Figure 3). The Cu1−S1−Cu3
bridging angle is 113.98 (4)°. The SCN¯ coordination through nitrogen is practically linear
with C−N−CuI angles in the range 163.3(3)−168.8(3)°. In contrast, the coordination through
sulphur is bent with C−S−CuI angles fall within the ranges 98.3(1)−103.4(1)°.
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The structure of complex 3 is shown in Figure 4, while the selected bond length and
angles are summarized in Table 4. The structure of 3 also contains a dinuclear cation
[CuII L2 ]2+, being located on a crystallographic inversion center and two [CuI(SCN)2]‾
2
2
anionic fragments similar to 2. The asymmetric unit of it consists of half of the reported
formula, [(CuIIL2)CuI(SCN)2]. The structure of the dinuclear cation [CuII L2 ]2+ is comparable
2
2
to that of 1 and 2. Thus, the basal plane of both the Cu1 atoms in the dinuclear fragments is
formed by the Schiff base ligand and SCN‾ ligands complete the square pyramidal
coordination geometry through Sꢀcoordination at the axial position from different sides of the
basal planes. As expected, the bond lengths and angles between 2 and 3 show very small
differences (Table 4). The r.m.s. deviation of these four donor atoms in the basal plane
around the Cu1 center is 0.108 Å while the metal atom deviates 0.212(1) Å from this plane
towards the axially coordinating sulphur atom. The Addison parameter of the Cu1 atom (τ =
0.257) indicates that it suffers less distortion from the square pyramidal geometry than that in
2. The Cu1···Cu1 separation in this dinuclear unit is 3.693(1) Å.
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Figure 4. The coordination environment of complex 3 with ellipsoids at 30% probability.
c
Symmetry transformation = x,−1/2−y,−1/2+z. Here, the Cu1 is divalent and the Cu2 is
monovalent.
Like 2, the crystal packing of 3 also forms the 1D anionic chains formulated as
nꢀ
[CuI(SCN)2]n . However, unlike 2, it is constructed by one independent copper(I) ion, Cu2
and by two SCN‾ anions. The monovalent Cu(2) atom has a tetrahedral coordination with
S2N2 chromophore. The τ4 index (0.811) confirms its tetrahedral coordination. Like 2, the
CuI−S and CuI−N distances vary in the ranges 2.549(1)−2.591(1) Å and 1.925(3)−1.928(3) Å,
respectively. Here, the 1D chain is formed by the connection of Cu2 atoms of two different
units by a ꢁ1,3ꢀSCN and a ꢁ1,1,3ꢀSCN ligands via both S and N ends. This type of binding
fashion comprises a 8ꢀmembered metallacyclic rings with Cu2···Cu2 separation of 5.371 Å.
The resulting 1D chains are connected by the divalent Cu1 atom of dinuclear units through
sulphur atom (S1) of ꢁ1,1,3ꢀSCN ligands to form a stair like 2D layer (Figure 5). Here, the
Cu1−S1−Cu2 bridging angle is 138.93 (5)°. The SCN‾ coordination through nitrogen and
sulphur are nearly linear and bent as are evident from C−N−CuI (161.3(4) and 163.4(4)°) and
C−S−CuI (97.8(2) and 100.3(2)°) angles, respectively.
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nꢀ
Figure 5. Top: The 1D anionic chain, [CuI(SCN)2]n is formed by Cu(I) and SCN¯ along
crystallographic ‘a’ axis. Bottom (Left): The stair like arrangement of 2D layer of 3
constructed by the connection of 1D chains by dinuclear cationic units via S atom of
thiocyanato ligand with in crystallographic ‘ac’ plane. Cu(I) and Cu(II) have been
represented by green and brown balls respectively. Bottom (Right): Stair like arrangement of
2D layer of 3 when view along ‘c’ axis. Here, brown colour indicates Cu atom and grey
colour represents dummy atom.
The 2D coordination framework of complexes 2 and 3 are very different (Figures 3 and 5)
although both are constructed by the connection of CuISCN based 1D chains via Cu(II) based
dinuclear linkers. They have different stoichiometry and coordination environment around
monovalent copper centers. Both trigonal planar and tetrahedral geometry around Cu(I) ions
in 2 forms a unique 1D chain formulated as [CuI2(SCN)3]n whereas, in the 1D chain,
[CuI(SCN)2]n of 3, Cu(I) adopts only trigonal planar geometry (Scheme 3). The different
nꢀ
nꢀ
substitution in amine part of Schiff base ligands (L) has no significant influence on the
molecular structure of the dinuclear linker of complexes 2 and 3. However, the dinuclear
Cu(II) unit in 3 is bulkier than that in complex 2 because the methyl groups of L1 have been
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replaced by ethyl groups in L2 (indicated by red circle in Figures 3 and 5). Thus, sterically
less demanding dinuclear Cu(II) moieties of complex 2 are accommodated between 1D
chains which are arranged in railroad trackꢀlike manner with the average interꢀchain
separation of 10.125 Å. On the other hand, presumably, in order to accommodate the bulkier
dinuclear Cu(II) moieties of complex 3, the 1D chains are organized like stairs with increased
average interꢀchain separation (10.864 Å).
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A
S
S
N
B
S
N
Cu
Cu
S
Cu(I)
N
N
Cu
N
Cu
S
S
N
N
S
Cu
N
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C
S
S
S
N
Cu
S
N
Cu
Cu
N
N
N
Cu
N
N
S
Cu
S
N
C
Scheme 3. The different coordination environment around Cu(I) by SCN‾ produces CuISCN
based different infinite chains (A and B) or layer (C). Complexes 2 and 3 are formed by
chains B and A respectively.
It is important to mention that previously one 2D and one 3D mixedꢀvalence Cu(I/II)
coordination polymers have been reported where cationic Cu(II) moieties associate with
CuISCN based anionic 1D chain and 2D layer (Scheme 3), respectively. The 2D polymer has
been reported by Ray et. al.30 In that structure, railroad trackꢀlike arrangement of 1D anionic
chains [CuI(SCN)2]nnꢀ from a 2D sheet as extended coordination framework host which traps
the imidazolidinyl phenolate bridged cationic Cu(II) dinuclear units through Hꢀbonding
interaction. It should be noted that formation of 1D anionic chain occurred in similar way as
in complex 3 but the arrangement of chains are different from 3. As mentioned before, Mitra
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et. al. reported21 the crystal structure of an isomeric 3D polymer that have identical molecular
building block [(CuIIL1)2CuI4(SCN)6] to 2D polymer, 2. However, the different
dimensionalities of these two isomers are due to the different structures of [CuI2(SCN)3]n
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anionic fragment. In the 3D isomer, the SCN ligands coordinate to Cu(I) only in trigonal
planar arrangement to form a 2D layers (Scheme 3C) which are interconnected by the
oximato bridged dinuclear Cu(II) moieties, (CuIIL1)2 to construct a 3D network. On the other
hand, in 2, the 1D chains (Scheme 3B) which are produced with the help of trigonal planar
and tetrahedral Cu(I), are connected by (CuIIL1)2 to form the 2D polymer.
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Magnetic properties of the complexes
The temperature dependent magnetic susceptibilities for complexes 1−3 were investigated in
the temperature ranges of 2−300 K and 2−30 K in applied fields of 7000 and 400 G,
respectively. The direct current (dc) magnetic properties of complexes 1−3 in the form of a
II
χ
MT vs. T plot (χM being the magnetic susceptibility per Cu2 unit and T the absolute
temperature) are shown in Figures 6−8. At room temperature, χ
MT is equal to 0.19 emu molꢀ1
K for 1, 0.19 emu molꢀ1 K for 2 and 0.15 emu molꢀ1 K for 3. These values are much lower
than the expected for the sum of two nonꢀinteracting CuII centers (0.75 emu molꢀ1 K, SCu = ½,
gCu = 2.0), providing evidence of strong antiferromagnetic interactions. For the three
complexes, the
0.01 emu molꢀ1 K for 2 and 0.02 emu molꢀ1 K for 3. For the three dinuclear CuII complexes
the M vs. T curve show a rapid increase of the M value below 100 K, due to the presence of
χ
MT product rapidly decreases to 100 K, reaching 0.002 emu molꢀ1 K for 1,
χ
χ
small amount of paramagnetic impurities (Figures 6−8 (inset)). Their structures reveal that
complex 1 contains two nonꢀequivalent CuII ions, while in complexes 2 and 3, the two
symmetry related CuII ions are equivalents. In the three cases the two metal ions CuII···CuII
are double bridged by two N,O oximato ligands.
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0.0007
0.0006
0.0005
0.0004
0.0003
0.0002
0.0001
0.20
0.15
0.10
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0.00
χ
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0
50 100 150 200 250 300
T
/ K
χ
0
50
100 150 200 250 300
T / K
Figure. 6. Plot of χMT vs. T for 1. The solid line represents the best fit to the experimental
data. The
χ
M vs. T plot is shown in the inset.
0.0035
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0.0030
0.0025
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0.0015
0.0010
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/ K
T
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T
χ
0
50
100 150 200 250 300
/ K
T
Figure 7. Plot of χMTvs. T for 2. The solid line represents the best fit to the experimental
data. The
χ
M vs.T plot is shown in the inset.
0.16
0.004
0.003
0.12
0.002
χ
0.001
0.08
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χ
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Figure 8. Plot of
data. The
χ
MT vs. T for 3. The solid line represents the best fit to the experimental
χ
M vs.T plot is shown in the inset.
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The fit of the experimental data was performed using the BleaneyꢀBowers equation
for dinuclear Cu(II) complexes, derived from the Hamiltonian H = −J(S1S2), and introducing
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a
ρ
term to evaluate the paramagnetic impurity.41 Best fit parameters are J = −549.6 cmꢀ1, g =
2.06,
= 0.9% and R = 3 x 10ꢀ6 for 1; J = −578.7 cmꢀ1, g = 2.17, = 2.2 % and R =3 x 10ꢀ6
for 2 and J = −663.8 cmꢀ1, g = 2.08, = 3.9 % and R = 4 x 10ꢀ6 for 3. The best fit curves are
ρ
ρ
ρ
plotted in Figures 6−8 along with the experimental data.
In the 2D polymers, the distances between the Cu(II) ions of the neighboring
dinuclear units are more than 10 Å and 8 Å for complexes 2 and 3 respectively. So any
possible interaction between the dinuclear Cu(II) units through the diamagnetic CuISCN
chains was not considered. Even if this interaction is present, its corresponding coupling
constant value should be several orders of magnitude less than the corresponding interaction
between the Cu(II) ions through the oximato ligand.
The large number of dinuclear Cu(II) complexes doubly bridged by two N,O oximato
ligands have been reported showing strong antiferromagnetic coupling,42ꢀ56 usually displaying
J values, in an absolute value, higher than −500 cmꢀ1 (even diamagnetism at room
temperature in some cases), so the strong antiferromagnetic coupling for complexes 1−3 was
not unexpected. Previous works, in this field, have shown that the mechanism of the
interaction between the two Cu(II) ions and the double oximatoꢀbridge depends on the good
orbital overlap in Cu−(R=NO)2−Cu core (R = different groups), as the most relevant
2
factor.30,31 The unpaired electron of each Cu(II) ion is located on the dx ꢀ y2 magnetic orbital,
so the planarity of the bridging region favors stronger antiferromagnetic coupling. According
to the literature data, the structural parameters that affect the strength of the magnetic
coupling, in Cu(II) dimers with double oximato ligands, are: the Cu−N and Cu−O distances,
the Cu−O−N and Cu−N−O angles, the distance from the Cu(II) ion(s) to the average plane of
the two NO bridges, the dihedral angle between the planes of each O−Cu−N unit and the
average plane of the two NO bridges and the dihedral Cu−N−O−Cu angle. The structural
values of the above mentioned parameters for complexes 1−3 are shown in Table 5.
Magnetoꢀstructural studies in complexes with high absolute J values, that imply small values
of the magnetic susceptibility along the temperature range, are not easy. Since theoretical
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calculations show that the most important parameter in determining the magnetic coupling
must be the planarity of the Cu(NO)2Cu ring,53ꢀ56 we have plotted the magnetic exchange, J,
constants as function of the average Cu−N−O−Cu dihedral angle for several analogous
complexes (Figure 9), since this angle reflects the planarity of this ring. Form this plot it is
evident that there is an approximate linear relationship between the coupling constant and the
dihedral Cu−N−O−Cu angle. In Figure 9, we have added the corresponding points to
complexes 1−3. From this result, it should be concluded that the magnetic exchange in
dinuclear Cu(II) complexes with double oximato ligands is in all cases very strong and
antiferromagnetic but a simple relation between planarity and the J parameter is not at all
consistent.
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60
Figure 9. J vs. the average value of the Cu−N−O−Cu dihedral angle. The regression line is
indicated.
Conclusions
We have synthesized and characterized three copper complexes (1−3) with oxime based
monoꢀcondensed Schiff base ligands. Complex 1 is a usual doubleꢀoximato bridged Cu(II)
dimer while complexes 2 and 3 are two rare mixedꢀvalence, Cu(I)ꢀCu(II) 2D coordination
polymers obtained by in situ reduction of a part of Cu(II) with NaSCN at room temperature.
–
–
The selfꢀreplication of the in situ generated CuI2(SCN)3 (in 2) or CuI(SCN)2 (in 3) anionic
fragments lead to the formation of CuINCS based 1D anionic chains which are linked by
cationic dimers. The 1D chain of 2 is formed in an unprecedented manner. The structures of
1D chains are different due to the different stoichiometry of Cu(I) and thiocyanoto ligand and
diverse coordination environment around copper(I) centers. The 1D chains are arranged
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railroad trackꢀlike in 2 and such arrangement is known but the stair like arrangement of 1D
chains which is found in 3 is unique for such species. The different substitutions in amine
part of Schiff base ligand in the Cu(II) dimers in 2 and 3 seems to be responsible for
different organization of 1D chains. Thus, the present system reveals that a subtle change in
the ligand system may lead to the formation of different network structures of mixedꢀvalence
Cu(I/II) coordination polymers. The magnetic coupling between the double oximato bridged
intraꢀdimer Cu(II) is antiferromagnetic and very strong, in agreement with the structurally
and magnetically characterized reported Cu(NO)2Cu dimers.
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Supporting Information
Figures of UVꢀVis spectra, IR spectra (Figures S1−S4) and crystallographic data in CIF
format for all three complexes (1−3). These material is available free of charge via the
Internet at http://pubs.acs.org.
Acknowledgments
L. K. D is thankful to CSIR, India for awarding Senior Research Fellowship [Sanction No.
09/028(0805)/2010ꢀEMRꢀI]. Crystallography was performed at the DSTꢀFIST, India funded
Single Crystal Diffractometer Facility at the Department of Chemistry, University of
Calcutta. The authors also thank the Department of Science and Technology (DST), New
Delhi, India, (SR/S1/IC/0034/2012) and the Spanish Government (Grant CTQ2012ꢀ30662)
for financial support.
References
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Table 1. Crystal data and structure refinement for complexes (1–3).
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Complexes
Formula
1
2
3
C21H42.5Cu2N6O10.5Cl2 C22H32Cu6N12O2S6 C24H40Cu4N10O2S4
M
745.09
Orthorhombic
P212121
1070.20
Triclinic
883.06
Monoclinic
P21/c
7
8
9
Crystal System
Space Group
P
1
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12
13
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19
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a/Å
b/Å
c/Å
7.8532(4)
18.8955(8)
22.8742(10)
90
90
90
3394.3(3)
4
1.458
1.466
1528
10.1247(3)
10.3908(3)
10.4233(6)
96.318(2)
102.640(2)
115.983(1)
934.96(7)
1
1.901
3.727
534
0.022
12968
3779
3342
0.0274, 0.0778
293
11.7972(6)
13.8115(7)
10.6670(5)
90
98.116(2)
90
1720.64(15)
2
1.705
2.721
900
0.050
19183
3057
α/°
β
/°
γ
/°
V/Å3
Z
Dc/g cm–3
µ/mm–1
F (000)
R(int)
0.047
38758
Total Reflections
Unique reflections 6018
4856
0.0631, 0.1922
293
2456
0.0381, 0.1022
293
I>2σ(I)
R1a, wR2b
Temp (K)
GOFc on F2
1.04
1.07
1.04
aR1 = ∑||Fo| − |Fc||/∑|Fo|, bwR2 (Fo ) = [∑[w(Fo − Fc2)2/∑w Fo ] and cGOF = [∑[w(Fo − Fc2)2/(Nobs – Nparams)]
2
2
4 ½
2
½
Table 2. Bond distances (Å) and angles (°) for complex 1.
Cu(1)–O(31)
Cu(1)–O(21)
Cu(1)–N(12)
Cu(1)–N(15)
2.396(9) Cu(2)–O(2)
1.881(5) Cu(2)–O(11)
1.997(5) Cu(2)–N(22)
1.921(5) Cu(2)–N(25)
2.104(7) Cu(1)–N(28)
95.7(3)
85.8(3)
92.8(3)
2.747(8)
1.870(4)
1.999(5)
1.905(6)
2.079(5)
101.2(3)
77.3(2)
Cu(1)–N(18a)
O(31)–Cu(1)–O(21)
O(31)–Cu(1)–N(12)
O(31)–Cu(1)–N(15)
O(31)–Cu(1)–N(18a) 101.5(3) O(2)–Cu(2)–N(28)
O(21)–Cu(1)–N(12)
O(21)–Cu(1)–N(15)
O(21)–Cu(1)–N(18a) 91.4(2)
N(12)–Cu(1)–N(15) 79.8(2)
N(12)–Cu(1)–N(18a) 161.7(2) N(22)–Cu(2)–N(28) 163.0(2)
O(2)–Cu(2)–O(11)
O(2)–Cu(2)–N(22)
O(2)–Cu(2)–N(25)
86.0(3)
101.8(3)
104.8(2) O(11)–Cu(2)–N(22) 105.8(2)
170.6(2) O(11)–Cu(2)–N(25) 171.2(3)
O(11)–Cu(2)–N(28) 91.0(2)
N(22)–Cu(2)–N(25) 80.4(2)
N(15)–Cu(1)–N(18a) 83.0(2)
N(25)–Cu(2)–N(28) 82.6(2)
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Table 3. Bond distances (Å) and angles (°) around metal atoms for complex 2.
Cu(1)–S(1)
Cu(1)–O(11)
Cu(1)–N(11)
Cu(1)–N(12)
2.713(2)
Cu(2)–S(2)
2.412(1)
Cu(3)–S(1)
Cu(3)–N(2)
Cu(3)–N(3)
2.358(1)
1.890(2)
1.898(3)
1.890(2)
2.007(2)
1.942(2)
2.073(2)
93.31(7)
91.09(7)
99.58(10)
99.00(10)
Cu(2)–S(3)
Cu(2)–N(1)
Cu(2)–S(2)c
2.280(1)
1.948(2)
2.508(1)
Cu(1)–N(13)
S(1)–Cu(1)–O(11)
S(1)–Cu(1)–N(11)
S(1)–Cu(1)–N(12)
S(1)–Cu(1)–N(13)
S(2)–Cu(2)–S(3)
112.33(3)
S(1)–Cu(2)–N(2) 112.68(9)
S(1)–Cu(2)–N(3) 110.29(9)
N(2)–Cu(2)–N(3) 136.98(13)
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S(2)–Cu(2)–N(1) 106.51(9)
S(2)–Cu(2)–S(2)c 110.01(3)
S(3)–Cu(2)–N(1) 123.28(9)
S(3)–Cu(2)–S(2)c 102.79(4)
O(11)–Cu(1)–N(11) 106.03(8)
O(11)–Cu(1)–N(12) 165.67(11) N(1)–Cu(2)–S(2)c 100.76(10)
O(11)–Cu(1)–N(13) 89.07(9)
N(11)–Cu(1)–N(12) 80.11(10)
N(11)–Cu(1)–N(13) 161.37(10)
N(12)–Cu(1)–N(13) 82.79(11)
Symmetry transformation c = −1−x,−y,−z.
Table 4. Bond distances (Å) and angles (°) around metal atoms for complex 3.
Cu(1)–S(1)
Cu(1)–O(11)
Cu(1)–N(11)
Cu(1)–N(12)
2.720(1)
1.896(2)
2.020(3)
1.944(4)
2.120(3)
96.87(9)
92.43(8)
90.01(9)
104.60(8)
Cu(2)–S(1)
Cu(2)–S(2)
Cu(2)–N(2)
Cu(2)–N(1)c
2.591(1)
2.549(1)
1.928(3)
1.925(3)
Cu(1)–N(13)
S(1)–Cu(1)–O(11)
S(1)–Cu(1)–N(11)
S(1)–Cu(1)–N(12)
S(1)–Cu(1)–N(13)
S(1)–Cu(2)–S(2)
S(1)–Cu(2)–N(2)
105.85(4)
97.24(11)
S(1)–Cu(2)–N(1)c 106.07(12)
S(2)–Cu(2)–N(2)
108.72(12)
O(11)–Cu(1)–N(11) 105.23(10) S(2)–Cu(2)–N(1)c 99.16(11)
O(11)–Cu(1)–N(12) 171.30(12) N(2)–Cu(2)–N(1)c 136.94(17)
O(11)–Cu(1)–N(13) 89.82(12)
N(11)–Cu(1)–N(12) 79.68(12)
N(11)–Cu(1)–N(13) 155.87(11)
N(12)–Cu(1)–N(13) 83.28(13)
Symmetry transformation c = x,−1/2−y,−1/2+z.
Table 5. Magnetic and structural parameters of complexes 1−3.
1
2
3
J (cmꢀ1)
−549.6
−578.7 −663.8
aθ (º)
168.60 / 171.15 163.89 170.76
bα (º)
10.02 /6.20
0.229 / 0.175
1.887 /1.866
2.002/2.006
23.65
0.325
1.890
2.007
14.00
0.191
1.897
2.019
cd (Å)
Cu–O (Å)
Cu–N (Å)
Cu–O–N (º) 122.87/123.70 122.11 124.20
Cu–N–O (º) 129.54/129.77 128.51 129.44
aθ = dihedral angle between the planes of each O
–Cu–N unit and the average plane of the two
NO bridges.bα= dihedral CuꢀNꢀOꢀCu angle. cd = distance from de CuII atom(s) to the average
plane of the two NO bridges.
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For Table of Contents Use Only
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Antiferromagnetic mixedꢀvalence Cu(I)ꢀCu(II) 2D coordination
frameworks constructed by double oximato bridged Cu(II)
dimers and CuISCN based 1D anionic chains
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Lakshmi Kanta Das, Carmen Diaz and Ashutosh Ghosh*
One oximato bridged Cu(II) dimer and two rare mixedꢀvalence Cu(I)ꢀCu(II) 2D coordination
polymers as a railroad trackꢀlike 2D sheet and a stair like 2D layer have been synthesized
using two oximeꢀbased tridentate Schiff bases. In situ partial reduction of Cu(II) to Cu(I) is
observed in presence of NaSCN at room temperature.
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