Synthesis, crystal structure and magnetic properties of a one-dimensional Mn(III) Schiff-base complex bridged by derivative of tetracyano-p-quinodimethane

Article abstract of DOI:10.1016/j.ica.2009.03.012

A new one-dimensional manganese(III) Schiff-base complex [Mn(III)(salophen) (MeOTCNQ)] · CH₃CN 1 (salophen = N,N′-bis(salicylidene)phenylenediamine) bridged by 7-methoxy-7,7,8,8-tetra-cyano-p-quinodimethane (MeOTCNQ), has been synthesized and c

Full text of DOI:10.1016/j.ica.2009.03.012

Inorganica Chimica Acta 362 (2009) 3333–3337
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Inorganica Chimica Acta
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Synthesis, crystal structure and magnetic properties of a one-dimensional Mn(III)
Schiff-base complex bridged by derivative of tetracyano-p-quinodimethane
a
Pei-Pei Yang a, Zong-Wei Li a, Xiao-Ling Wang a, Li-Cun Li a,b, , Dai-Zheng Liao
*
a Department of Chemistry, Nankai University, 94 Weijing Road, Tianjin 300071, PR China
b State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A new one-dimensional manganese(III) Schiff-base complex [Mn(III)(salophen) (MeOTCNQ)] ꢀ CH3CN 1
(salophen = N,N0-bis(salicylidene)phenylenediamine) bridged by 7-methoxy-7,7,8,8-tetra-cyano-p-
quinodimethane (MeOTCNQ), has been synthesized and characterized by X-ray crystallography and mag-
netic studies. Crystal structure study reveals that complex 1 has a 1D manganese(III) chain bridged by
MeOTCNQ ligand which was obtained unexpectedly from tetracyano-p-quinodimethane (TCNQ) reacting
with methanol. Noticeably, MeOTCNQ molecules in complex 1 adopt an unusual cis–syn coordination
mode. The analysis of magnetic data indicates that a weak intrachain antiferromagnetic interaction exists
in complex 1.
Received 12 October 2008
Received in revised form 1 March 2009
Accepted 6 March 2009
Available online 16 March 2009
Keywords:
1D complex
Manganese(III) Schiff base
TCNQ
Ó 2009 Elsevier B.V. All rights reserved.
Magnetic property
1. Introduction
displays unambiguous evidence of SCM behavior. From this point
of view, we expected to utilize TCNQ as bridging ligand to design
Magnetic coordination polymers have attracted intense interest
in view of their structure diversity and in the context of molecule-
based magnetic materials [1–5]. Their magnetic properties depend
on the nature of the interacting metal ions, and can be tuned by the
nature of the bridging ligand and by the whole structural arrange-
ment [6,7]. One synthetic strategy widely employed is the use of
organic ligand (e.g., salen-type Schiff base) to block several equato-
rial coordination sites of the paramagnetic cations, leaving two free
axial positions to be occupied by bridging ligands that can link
adjacent paramagnetic metal centers. An increasing number of
manganese(III) coordination polymers based on tetradentate Schiff
bases bridged by cyano, azido, oxalato, and nitride have been re-
ported that present a remarkable diversity in bridging topology,
and special magnetic properties in recent years [8–15]. Among
them, cyanide bridged metal coordination polymers including
magnetic materials based on organocyanide ligands such as
7,7,8,8-tetracyano-p-quinodimethane (TCNQ) exhibit interesting
electrical, optical and magnetic properties [15–18].
a 1D Mn(III) complex based on Schiff bases N,N0-bis(salicylid-
ene)-o-phenylenediamine (salophen). Interestingly, the TCNQ li-
gand was experienced with nucleophilic addition reaction and
MeOTCNQ was obtained by chance, which was scarcely observed
in previous literature [28]. In this text, we report the crystal struc-
ture and magnetic properties of the obtained complex,
[Mn(III)(salophen)(MeOTCNQ)] ꢀ CH3CN 1.
2. Experimental
2.1. General
All reagents were purchased commercially and used without
further purification. Deionized water was used for the conventional
synthesis. Elemental analyses of carbon, hydrogen and nitrogen
were carried out with a Perkin–Elmer 240 analyzer. The infrared
spectra of the complexes in KBr pellets were obtained on a BIO-
RAD FTS 3000 instrument in the range of 4000–400 cmꢁ1 region.
The magnetic susceptibility data were recorded using a Quantum
Design MPMS-7 SQUID Magnetometer in the temperature range
from 2 to 300 K at an applied magnetic field of 1 kG.
Because of the diverse coordination chemistry of TCNQ [19], a
large number of 0-D complexes [20], 1D chains [21–24], and 2-D
nets [25–27] have been designed and synthesized. However, few
TCNQ-bridged Mn(III) complexes have been reported. Very re-
cently, Miyasaka et al. have reported an alternated 1:1 chain com-
plex of a MnIII salen derivative and the TCNQ monoradical which
2.2. Syntheses of [Mn(III)(salophen)(MeOTCNQ)] ꢀ CH3CN 1
A mixture containing Mn(ClO4)2 ꢀ 6H2O (0.0362 g, 0.1 mmol)
and salophen (0.0346 g, 0.1 mmol) in 15 mL of CH3CN stirring for
0.5 h was added a solution of LiTCNQ (0.0213 g, 0.1 mmol) in
5 mL methanol. After stirring for 20 min at room temperature,
* Corresponding author. Address: Department of Chemistry, Nankai University,
94 Weijing Road, Tianjin 300071, PR China.
E-mail address: ypp@mail.nankai.edu.cn (L.-C. Li).
0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.03.012

3334
P.-P. Yang et al. / Inorganica Chimica Acta 362 (2009) 3333–3337
Table 2
the dark brown solution was filtered and allowed to stand for
about one week at room temperature to form dark black crystals
of [Mn(III)(salophen)(MeOTCNQ)] ꢀ CH3CN. The crystals were col-
lected by suction filtration, washed with a minimum amount of
cold methanol, and dried in vacuo. Yield: 65% based on Mn(III). Ele-
mental Anal. Calc. for C35H24MnN7O3: C, 64.80; H, 3.78; N, 14.62.
Selected bond lengths (Å) and angles (°) for complex 1.
Mn(1)–O(2)
Mn(1)–O(1)
Mn(1)–N(2)
Mn(1)–N(1)
1.8698(15)
1.8713(15)
1.9922(17)
1.9923(17)
Mn(1)–N(3)
Mn(1)–N(4)
N(4)–Mn(1)
2.3063(19)
2.3271(18)
2.3272(18)
86.30(7)
Found: C, 65.06; H, 3.72; N, 15.18%. IR (KBr):
C@N 1604 cmꢁ1 C„N 2181, 2113 cmꢁ1. The IR spectroscopy
study on 1 shows significant lower-energy C„N vibrations at
m ,
C–H 3453 cmꢁ1
O(2)–Mn(1)–O(1)
O(2)–Mn(1)–N(2)
O(1)–Mn(1)–N(2)
O(2)–Mn(1)–N(1)
O(1)–Mn(1)–N(1)
N(2)–Mn(1)–N(1)
O(2)–Mn(1)–N(3)
O(1)–Mn(1)–N(3)
N(2)–Mn(1)–N(3)
N(1)–Mn(1)–N(3)
O(2)–Mn(1)–N(4)
O(1)–Mn(1)–N(4)
91.61(6)
92.88(7)
175.49(7)
175.09(7)
92.88(7)
82.64(7)
94.34(7)
93.33(7)
85.96(7)
87.37(7)
91.26(7)
96.22(6)
N(1)–Mn(1)–N(4)
N(3)–Mn(1)–N(4)
C(7)–N(1)–Mn(1)
C(8)–N(1)–Mn(1)
C(14)–N(2)–C(13)
C(14)–N(2)–Mn(1)
C(13)–N(2)–Mn(1)
C(21)–N(3)–Mn(1)
C(23)–N(4)–Mn(1)
C(1)–O(1)–Mn(1)
C(20)–O(2)–Mn(1)
N(2)–Mn(1)–N(4)
168.79(7)
124.66(14)
112.66(13)
123.45(18)
123.93(14)
112.54(13)
166.58(17)
130.70(16)
127.50(13)
127.89(14)
84.06(7)
m
, m
m
2181(s) and 2113 cmꢁ1 compared with the monoradical TCNQ
form consistently with the vibration bands at 2197 and
2168 cmꢁ1 for Li(TCNQ) [29]. It indicates that TCNQ ligands may
be changed in the reaction, which is in agreement with the struc-
ture analysis.
2.3. X-ray crystallography
Single-crystal X-ray studies were performed on a Bruker SMART
1000 CCD diffractometer equipped with graphite crystal mono-
chromator situated in the incident beam for data collection. The
determination of unit cell parameters and data collections were
consists of the [Mn(III)(salophen)] moiety and the MeOTCNQ li-
gand in a 1:1 stoichiometry with the Mn atom located on the cen-
ter of the equatorial plane. The coordination sphere around the Mn
ion is an elongated octahedron with the salophen tetradentate li-
gand surrounding the manganese equatorial plane with bond
lengths of Mn(1)–O(1) 1.8713(15), Mn(1)–O(2) 1.8698(15),
Mn(1)–N(1) 1.9923(17) and Mn(1)–N(2) 1.9922(17) Å; On the
other hand, the two left Mn axial positions are occupied by nitro-
gen atoms of the MeOTCNQ ligands, which adopt an uncommon
cis–syn coordination fashion with Mn(1)–N(3) 2.3063(19) and
Mn(1)–N(4A) 2.3272(18) Å. The Mn(1)–N(3)–C(21), Mn(1)–N(4)–
C(23) angles in complex 1 are found to be 166.59° and 130.71°,
respectively. The axial distortion of the Mn octahedron coordina-
tion sphere corresponds to a Jahn–Teller axis typically observed
for MnIII salophen analogues (N(3)–Mn(1)–N(4A) 168.79(7)°, sym-
metry operation, x ꢁ 1/2,ꢁy + 1/2,z ꢁ 1/2). The two neighboring
Mn(III) ions in the 1D chain (shown in Fig. 2) are separated with
the shortest distances of Mn1ꢀꢀꢀMn1A 8.516 Å, indicating that the
magnetic interaction of the 1D chain may be very weak.
performed with Mo Ka radiation (k = 0.71070 Å). The structure
was solved by direct methods and semi-empirical absorption cor-
rections were applied using the SHELXS-97 program [30]. The final
refinement was performed with the SHELXL-97 program [31] by
full-matrix least-squares methods with anisotropic thermal
parameters for non-hydrogen atoms on F2. The hydrogen atoms
were generated theoretically onto atoms to which they are at-
tached and refined isotropically with fixed thermal factors. Further
details about crystal data and structure refinement are summa-
rized in Table 1. Selected bond lengths and bond angles for the ob-
tained complex are listed in Table 2.
3. Results and discussion
3.1. Structure description
It is worth to note that the side of TCNQ ligand which is not
coordinated with Mn(III) has changed. MeOTCNQ was obtained
by the uncoordinated side of TCNQ processing nucleophilic addi-
tion with methanol accidentally. The possible mechanism of this
addition reaction can be hypothesized as follows. The coordination
of TCNQ radical anion with Mn(III) cation makes itself act as an
eletrophilic group and the electron cloud of TCNQ migrates to
Complex 1 crystallizes in the monoclinic space group P21/n and
the asymmetrical unit of 1 is depicted in Fig. 1. The repeating unit
Table 1
Data collection and processing parameters for complex 1.
Complex
Formula weight
Crystal system
Space group
a (Å)
C35H24MnN7O3 (1)
645.55
monoclinic
P121/n1
15.381(4)
b (Å)
13.967(3)
c (Å)
15.629(4)
a
(°)
b (°)
(°)
90.00
116.221(4)
90.00
3012.0(14)
c
Volume (Å3)
Z
4
Dcalc (Mg mꢁ3
)
1.424
0.488
1328
Absorption coefficient (mmꢁ1
F(000)
)
Crystal size (mm)
h range for data collection (°)
Limiting indices
0.16 ꢂ 0.14 ꢂ 0.10
2.06–27.87
ꢁ20 ꢃ h ꢃ 20
ꢁ18 ꢃ k ꢃ 18
ꢁ20 ꢃ l ꢃ 20
37331/7182 [0.0581]
full-matrix least-squares on F2
7182/0/418
1.125
Reflections collected/unique [Rint
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
]
Final R indices [I>2
r
(I)]
R1 = 0.0530, wR2 = 0.1088
R1 = 0.0629, wR2 = 0.1139
0.335 and ꢁ0.447
R indices (all data)
Largest peak and hole (e Åꢁ3
)
Fig. 1. The repeating unit of complex 1 (hydrogen atoms and solvent molecule have
been omitted for clarity).

P.-P. Yang et al. / Inorganica Chimica Acta 362 (2009) 3333–3337
3335
Fig. 2. The one-dimensional chain structure in complex 1 (hydrogen atoms and solvent molecule have been omitted for clarity).
Mn(III), rendering the side of TCNQ approaching Mn(III) cation
more electrophilic. Therefore, the nucleophilic addition of metha-
nol to TCNQ could be facilitated, affording MeOTCNQ ligand.
where A = 2.0, B = 71.938, C = 10.482, D = 955.56. The J parameter
P
^
^ ^
is based on the Heisenberg–Hamiltonian H ¼ ꢁ2J i–jSiSj.
Ng2b2
AþBx2
vm
¼
1þCxþDx3
kT
ð1Þ
3.2. Magnetic properties
x ¼ jJj=kT
The simulative model provides a good result from 300 to 9 K.
The temperature dependence of the magnetic susceptibility for
1 has been investigated at a field of 1000 Oe in the temperature
range 2–300 K. The room-temperature leff value is around 4.90lB
per Mn(III) ion, which is in good agreement with the expected va-
lue for one isolated spin-only MnIII ion (4.90lB for g = 2, S = 2).
Upon cooling, the value of leff decreases smoothly with a value
of 3.65lB at 4 K, which indicates an intrachain antiferromagnetic
interaction. And then, after a small upturn, it exhibits a relatively
abrupt increase on further cooling at about 3.5 K, which can be
attributed to the result of spin canting [32–36].
The best fit of the magnetic data leads to J = ꢁ0.2 cmꢁ1, g = 2.01
P
and the agreement factor R = 1.35 ꢂ 10ꢁ3 (R is defined as
2
2
ð
vcmalcd
ꢁ
vombsdÞ =ðvmobsdÞ ). This fit is indicated in Fig. 3 as a solid
line, which show the magnetic coupling between Mn(III) ions is
very weak.
As well known, the Mn(III) ion usually has an important zero-
field splitting [38]. The decrease of vMT product in the low temper-
ature region may be due to the zero-field splitting of the ground
state of the Mn(III) ion and/or very weak Mn(III)–Mn(III) magnetic
interactions. Thus we analyzed the same set of data by the follow-
ing equations including both single ion zero-field splitting (D) and
weak magnetic coupling between Mn(III) ions with the use of
molecular field approximation [39]:
First, according to the structure of complex 1, we fitted the
experimental susceptibility by using the expression for antiferro-
magnetic one-dimensional S = 2 chain given by Hiller et al. [37].
The expression for the magnetic susceptibility is given by Eq. (1),
6.0
5.5
5.0
4.5
4.8
4.6
4.4
4.2
4.0
3.8
3.6
3.4
4.0
3.5
3.0
2.5
2.0
0
5
10 15 20 25 30 35 40 45 50 55
T(K)
0
50
100
150
200
250
300
T(K )
Fig. 3. Temperature dependence of vMT for 1 at 1000 Oe fitted by using the expression for antiferromagnetic one-dimensional chain; the solid lines represent the best fit of
the data.

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P.-P. Yang et al. / Inorganica Chimica Acta 362 (2009) 3333–3337
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
4.8
4.6
4.4
4.2
4.0
3.8
3.6
3.4
0
5
10 15 20 25 30 35 40 45 50 55
T(K)
0
50
100
150
200
250
300
T(K)
Fig. 4. Temperature dependence of vMT for 1 at 1000 Oe fitted by using the equations including both single ion zero-field splitting (D) and intermolecular effects with the use
of molecular field approximation; the solid lines represent the best fit of the data.
vjj þ 2v?
Acknowledgement
vZFC
¼
3
This work was financially supported by the National Science
Foundation of China (Nos. 20471032, 20331010, 50672037) and
the NSF of Tianjin (No. 09JCYBJC05600).
2Ng2jjb2
expðꢁD=kTÞ þ 4 expðꢁ4D=kTÞ
vjj
¼
kT 1 þ 2 expðꢁD=kTÞ þ 2 expðꢁ4D=kTÞ
Ng2?b2 ð6=xÞð1 ꢁ expðꢁxÞ þ ð4=3xÞðexpðꢁxÞ ꢁ expðꢁ4xÞÞ
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v?
¼
kT
1 þ 2 expðꢁxÞ þ 2 expðꢁ4xÞ
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