Cobalt(II), manganese(IV) mononuclear and zinc(II) symmetric dinuclear complexes of an aliphatic hydrazone schiff Base ligand with diversity in coordination behaviors and supramolecular architectures: Syntheses, structural elucidations, and spectroscopic

Article abstract of DOI:10.1246/bcsj.20110004

Three new complexes of cobalt, manganese, and zinc have been synthesized using a hydrazone Schiff base ligand {(E)-N'-[1-(2-hydroxyphenyl)ethylidene] acetohydrazide} (LH₂) produced by the 1:1 condensation of acetic hydrazide and 2-hydroxyacetop

Full text of DOI:10.1246/bcsj.20110004

7
64
Bull. Chem. Soc. Jpn. Vol. 84, No. 7, 764­777 (2011)
© 2011 The Chemical Society of Japan
Cobalt(II), Manganese(IV) Mononuclear and Zinc(II) Symmetric
Dinuclear Complexes of an Aliphatic Hydrazone Schiff Base Ligand with
Diversity in Coordination Behaviors and Supramolecular Architectures:
Syntheses, Structural Elucidations, and Spectroscopic Characterizations
1
1
2
3
4
Dipali Sadhukhan, Aurkie Ray, Guillaume Pilet, Georgina M. Rosair, Eugenio Garribba,
5
5
1
Aline Nonat, Loïc J. Charbonnière, and Samiran Mitra*
1Department of Chemistry, Jadavpur University, Raja S. C. Mullick Road, Kolkata 700032, West Bengal, India
2Groupe de Cristallographie et Ingénierie Moléculaire Laboratoire des Multimatériaux et Interfaces UMR 5615 CNRS ­
Université Claude Bernard Lyon 1, Bât. Jules Raulin, 43 bd du 11 Novembre, 1918 69622 Villeurbanne, Cedex, France
3School of Engineering and Physical Sciences, Heriot Watt University, Edinburgh EH14 4AS, UK
4Department of Chemistry and Center for Biotechnology Development and Biodiversity Research, University of Sassari,
Via Vienna 2, I-07100 Sassari, Italy
5Laboratoire d’Ingénierie Moléculaire Appliquée à l’Analyse, IPHC, UMR 7178, CNRS/UdS, ECPM,
25 rue Becquerel, 67087 Strasbourg Cedex 2, France
Received January 5, 2011; E-mail: smitra_2002@yahoo.com
Three new complexes of cobalt, manganese, and zinc have been synthesized using a hydrazone Schiff base ligand
{
(E)-N¤-[1-(2-hydroxyphenyl)ethylidene]acetohydrazide} (LH2) produced by the 1:1 condensation of acetic hydrazide
and 2-hydroxyacetophenone. The ligand has shown three different coordination modes in the three complexes: a
II
monoanionic tridentate coordination mode with the Co complex ([Co(LH)2]¢CH3OH, 1), a dianionic tridentate
IV
coordination mode with the Mn complex ([Mn(L)2], 2), and monoanionic ®2-phenoxo-bridged tridentate coordination
II
mode with the Zn complex ([Zn(LH)(OOCCF3)]2, 3). All three complexes show interesting supramolecular
architectures, especially for 3 a nanoporous supramolecular (4, 4) grid 2D framework is formed. The ligand and the
II
IV
complexes are well characterized by elemental analysis, IR and UV­vis spectroscopy. The spin states of the Co and Mn
metal ions and hence the coordination modes of the ligand in these complexes are in good agreement with the EPR
spectroscopic data. The fluorescence emission spectra of LH2 and the zinc complex 3 are measured in acetonitrile solution
as well as in solid state.
Hydrazones are a special class of Schiff base ligands which
enolisation and second deprotonation, thus behaving as a
1
6
contain a secondary amido group (R­CO­NH­) in addition
to the azomethine (­C=N­) functionality. It is not easy
to make the amido N of hydrazone Schiff bases coordinate to
dianionic ligand as reported by our research group and
1
7­19
others.
A favorable situation can be created to make
the CH ­CO­NH­ group of aliphatic hydrazone Schiff
3
1
the metal center by deprotonation of the amido N­H proton,
base easily enolisable if all other donor groups of the Schiff
2
0,21
but this amido group plays an important role to promote
inter- and intramolecular hydrogen-bonding interactions, to
stabilize the metal­organic framework and to generate various
interesting supramolecular architectures.2 Moreover the
base coordinate in their neutral form,
or if the metal ion
2
2
exists in its high oxidation state as shown by Pal et al. They
have structurally characterized two Ru complexes with an
III
,3
aliphatic hydrazone ligand N-acetyl-N¤-salicylidenehydrazine
2
azomethine N, containing a lone pair of electrons in an sp
(H acs). The first one [Ru(acs)(Hacs)] is an octahedral bis
2
4
hybrid orbital, is biologically important. Additionally, hydra-
chelated complex in which the amido proton of one ligand
dissociates, but both the ligand fragments are crystallograph-
ically equivalent suggesting a crystallographic static disorder
present in the complex. Another complex (PPh )[Ru(acs) ]
zone metal complexes have also attracted research interest
5,6
for their possible pharmacological applications, antimicro-
bial, and antitumor activities.7 Hydrazone complexes of NiII
were first characterized by Sacconi in 1952.15 In his report
Sacconi stated that the R­CO­NH­ group is easier to enolise
when R = phenyl, compared with that of the alkyl­CO­NH­.
There are plenty of crystal structures of transition-metal
complexes of aromatic hydrazones containing an ionic phe-
nolic ­OH group in which the Ar­CO­NH­ group undergoes
­14
4
2
III
exhibits the doubly deprotonated ligands coordinating the Ru
center via the enolic form of the amido oxygen. In this report
deprotonation of the amido N is assisted by the extensive use
of the strong base KOH and stabilization of the coordinated
ligands in their dianionic form requires an external cation
+
PPh4
.
Published on the web July 2, 2011; doi:10.1246/bcsj.20110004

D. Sadhukhan et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
765
O
H
N
O
+
2
H N
N
N
H
OH
O
OH
2-hydroxyacetophenone
Acetic hydrazide
{(E)-N'-[1-(2-hydroxyphenyl)
ethylidene]acetohydrazide} [LH2]
Form I: Neutral ligand
H
N
1stdeprotonation
N
H
O
or
N
N
O¯
O
Form IV: Phenoxo bridging coordination mode
in monoanionic state [LH]
O¯
-
Form II: Ketonic coordination mode
in monoanionic state [LH]-
Keto-enol tautomerization
and second deprotonation
N
N
O¯
O¯
Form III: Enolic coordination mode
2
-
in dianionic state [L]
Scheme 1. Design of the ligand [LH2] and its different coordination modes.
In the present work a similar aliphatic hydrazone {(E)-N¤-
2-hydroxyacetophenone. There are very few structural reports
II
III
[
1-(2-hydroxyphenyl)ethylidene]acetohydrazide} (LH ) is sub-
of Cu and Ru complexes of quite similar hydrazone ligands
synthesized of acetic hydrazide and different substituted/
2
II
II
II
jected to complexation with Co , Mn , and Zn precursors,
showing three different coordination modes: monoanionic
tridentate mode forming a Co complex, dianionic tridentate
mode forming a Mn complex and monoanionic ® -phenoxo
bridging tridentate mode forming a Zn complex. The different
1
3,26­28
unsubstituted salicylaldehydes.
We have prepared three
II
complexes of the ligand with cobalt, manganese, and zinc ions.
The X-ray crystal structures of the ligand and the complexes
exhibit the unique role of the metal ions to facilitate different
ligating behavior of the ligand (Scheme 1). The ligand as well
as the complexes exhibits various interesting supramolecular
architectures. The mode of ligand coordination to the metal
ions is further confirmed by the spin state investigation by EPR
spectroscopy of the cobalt and manganese complexes and by
the fluorescence spectroscopy of the zinc complex which
IV
2
II
coordination modes of the ligand LH2 are automatically
stabilized by the oxidation states and geometric requirements
II
IV
II
of the metal ions (Co , Mn , and Zn ) in the respective
complexes, no further assistance by base or any ionic
stabilizing agent being required.
Moreover, luminescent metal complexes of salicylaldimi-
nato ligands are being extensively studied after the develop-
ment of thin layer organic light-emitting diodes (OLED) by
Tang and VanSlyke in 1987.23 Hydrazone ligands containing a
salicylaldiminato component provide suitable ligand environ-
ment namely a hydroxy group, a coordinating imine N atom
and a delocalized ³ system24 so that their zinc complexes can
show excellent luminescence properties in blue, greenish, and
exhibits blue emission characteristics, typical of ® -phenoxo-
2
2
9,30
bridged zinc­salen complexes.
Experimental
Syntheses. All solvents were of reagent grade and used
without further purification. Acetic hydrazide and 2-hydroxy-
acetophenone were purchased from Aldrich Chemical Co.
and used as received. Cobalt perchlorate was prepared by the
reaction of cobalt carbonate (E. Merck, India) and 60%
perchloric acid (E. Merck, India). To prepare manganous
trifluoroacetate, aqueous solution of manganous sulfate was
2
5
red regions.
In this present work, we have spectroscopically and
structurally characterized a new aliphatic hydrazone ligand
LH synthesized by 1:1 condensation of acetic hydrazide and
2

7
66
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
Variable Ligand Coordination Modes
treated with aqueous sodium carbonate solution in 1:2 molar
ratio, the light pink precipitate of manganous carbonate was
collected by filtration and 60% trifluoroacetic acid (E. Merck,
India) was added immediately within the precipitate. Zinc
trifluoroacetate was prepared by treatment of zinc carbonate (E.
Merck, India) with 60% trifluoroacetic acid (E. Merck, India). In
all the cases the metal perchlorate and trifluoroacetate solutions
were filtered through a fine glass-frit and evaporated on a steam
were isolated by filtration and were air-dried. Yield: 0.5839 g
(79%). Elemental analysis. Found: C, 38.79; H, 2.80;
N, 7.38%. Calcd for C H F N O Zn (739.21): C, 38.96;
2
4
22
6
4
8
2
H, 2.98; N, 7.57%. Main FT-IR bands. ¯C=N 1624, ¯
¯N­H 3058, ¯Zn­N 438, ¯C­F 1189, ¯COOꢀðasymÞ 1685 cm . Main
UV­vis bands. ³­³* 252; n­³* 357 nm.
1600,
C=O
¹
1
Physical Measurements. The Fourier transform infrared
¹
1
spectra were recorded in the range 4000­400 cm on a Perkin-
Elmer RX I FT-IR spectrophotometer with solid KBr pellets.
The electronic spectra in HPLC grade acetonitrile were
recorded at 300 K on a Perkin-Elmer Lambda 40 (UV­vis)
spectrometer in a 1 cm quartz cuvette in the range 800­200 nm.
bath and preserved in a CaCl desiccator for further use.
2
Synthesis of the Hydrazone Ligand {(E)-N¤-[1-(2-hy-
droxyphenyl)ethylidene]acetohydrazide} [LH ]. The ligand
2
LH2 {(E)-N¤-[1-(2-hydroxyphenyl)ethylidene]acetohydrazide}
was prepared by the condensation of acetic hydrazide (0.74 g,
C, H, and N microanalyses were carried out with a Perkin-
1
1
0 mmol) with 2-hydroxyacetophenone (1.362 g, 10 mmol) in
Elmer 2400 II elemental analyzer. H NMR spectrum of LH
2
the presence of a catalytic amount of glacial acetic acid in
methanol medium (200 mL). On refluxing the methanolic
solution for 5 h a colorless solution was observed. The solvent
was removed under reduced pressure and the white residue was
purified by recrystallization from methanol from which color-
less shiny crystals were obtained. Yield 0.177 g (92%).
Elemental analysis. Found: C, 62.58; H, 6.23; N, 14.49%.
Calcd for C H N O (192.1): C, 62.49; H, 6.29; N, 14.57%.
was recorded on a BRUKER 300 MHz FT-NMR spectrometer
using trimethylsilane as an internal standard in CDCl . EPR
3
spectra were recorded at room temperature or at 100 K with an
X-band (9.15 GHz) Varian E-9 spectrometer. The steady state
fluorescence emission spectra for LH and 3 were recorded in
2
acetonitrile medium at 25 °C on a Perkin-Elmer LS55
luminescence spectrometer. The fluorescence quantum yields
(¤) were calculated with reference to quinine sulfate in 0.5 M
sulfuric acid with a known ¤r of 0.546 when excited at 356 nm
at 25 °C using the following equation:
1
0
12
2
2
¹
1
Main FT-IR bands. ¯C=N 1667, ¯C=O 1608, ¯N­H 3100 cm .
Main UV­vis bands. ³­³* 246, n­³* 320 nm.
Synthesis of [Co(LH) ]¢CH OH (1).
0.381 g, 1.5 mmol) was dissolved in 20 mL methanol. 20 mL
Co(ClO ) ¢xH O
4 2 2
2
3
2
¤x=¤ ¼ ½Ix=Irꢁ ꢂ ½Ar=Axꢁ ꢂ ½­r=­xꢁ ꢂ ½© =© ꢁ
ð1Þ
r
x
r
(
warm methanolic solution of the Schiff base LH (0.178 g,
Here, subscripts x and r refer to the unknown and reference
solutions, ¤ is a quantum yield, A is a calculated optical
density, ­ is excitation wavelength, I is the area under the
emission curve which was integrated using the software
available in the instrument and © is the index of refraction of
the solvent. The fluorescence lifetime of 3 was determined
by time-correlated single-photon counting using a nano-LED
excitation source at 370 nm and TBX-04 detector (both IBH,
U.K.). The decays were analyzed using IBH DAS-6 decay
analysis software.
Steady state emission and excitation spectra in the solid state
were recorded on a Horiba Jobin Yvon Fluorolog 3 spectrom-
eter working with a 450WXe lamp and fitted with an
integrating sphere Quanta-¯ from Horiba. Detection was
performed with a Hamamatsu R928 photomultiplier. All
spectra were corrected for the instrumental functions. When
necessary, a 350 nm cut-off filter was used to eliminate the
second generation harmonic artifacts.
Luminescence quantum yields were determined using an
absolute method with an integrating sphere Quanta-¯ from
Horiba. The quantum yield in the absolute method can be
calculated by eq 2
2
1
mmol) was added to the former. The mixture was allowed to
stir for 0.5 h with heating at 60 °C. The dark brown solution
was kept at room temperature. Orange plate shaped single
crystals suitable for X-ray diffraction were obtained within two
days. Crystals were isolated by filtration and were air-dried.
Yield: 0.201 g (85%). Elemental analysis. Found: C, 53.17; H,
3
1
5
.38; N, 11.75%. Calcd for C H Co N O (473.39): C, 53.23;
21
26
1
4
5
H, 5.49; N, 11.83%. Main FT-IR bands. ¯
¯N­H 2928, ¯Co­N 459 cm . Main UV­vis bands. ³­³* 300,
n­³* 382, LMCT 238 nm.
1591, ¯C=O 1544,
C=N
¹
1
Synthesis of [Mn(L) ] (2). Mn(OOCCF ) ¢xH O (0.4215 g,
2
3 2
2
1
.5 mmol) was dissolved in 20 mL acetonitrile. 20 mL warm
methanolic solution of the Schiff base LH (0.178 g, 1 mmol)
2
was added to the former. The mixture was allowed to stir for 1 h
with heating at 60 °C. The resulting dark brown solution was
kept undisturbed at room temperature for slow evaporation of
solvent. Red plate shaped single crystals suitable for X-ray
diffraction were obtained after one week. Crystals were isolated
by filtration and were air-dried. Yield: 0.178 g (82%). Elemental
analysis. Found: C, 55.05; H, 4.46; N, 12.75%. Calcd for
C H MnN O (435.34): C, 55.13; H, 4.59; N, 12.86%. Main
2
0
20
4
4
¹
1
FT-IR bands. ¯C=N 1577, ¯C=O 1542, ¯Mn­N 444 cm . Main
UV­vis bands. ³­³* 291, n­³* 350, LMCT 221, A ¼ T
2g
53, A ¼ T (F) 419 nm.
R
­
ꢀ
ꢁ
sam
em
ref
em
4
4
I
ð­Þ ꢀ I ð­Þ d­
2g
Nemission
hc
4
4
5
º ¼
¼
ð2Þ
2
g
1g
Nabsorption
R ­ ꢀ
ꢁ
Synthesis of [Zn(LH)(OOCCF )] (3). Zn(OOCCF3)2¢
ref
ex
sam
3
2
I
ð­Þ ꢀ Iex ð­Þ d­
hc
xH O (0.4371 g, 1.5 mmol) was dissolved in 20 mL acetonitrile.
2
2
0 mL warm methanolic solution of the Schiff base LH2
where Nabsorption is the number of photons absorbed by a sample
and Nemission is the number of photons emitted from a sample,
­ is the wavelength, h is Planck’s constant, c is the velocity of
light, Iex and Iex are the integrated intensities of the excitation
light with and without a sample, respectively, Iem and I are
(0.178 g, 1 mmol) was added to the former. The mixture was
allowed to stir for 1 h with heating at 60 °C. The colorless
solution was kept undisturbed at room temperature for slow
evaporation of solvent. Colorless cubic single crystals suitable
for X-ray diffraction were obtained after one week. Crystals
sam
ref
sam
ref
em
the photoluminescence intensities with and without a sample,

D. Sadhukhan et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
767
3
2
35
respectively. This method has been described in detail by
Rohwer and Martin.33
DENZO/SCALEPACK. Data reduction was performed with
38
CrysAlis RED. The structures were solved by direct method
using the program SIR97 and refined with the program
3
6
X-ray Crystallography. The X-ray diffraction data of LH2
were collected on a colorless cubic single crystal (0.08 mm ©
.24 mm © 0.25 mm) using a Nonius Kappa CCD diffractom-
eter containing area detector and graphite monochromator
with Mo K¡ radiation (­ = 0.71073 ¡). Empirical absorption
corrections were carried out by multi scan technique. Data
reduction was performed with DENZO/SCALEPACK pro-
3
7
CRYSTALS. All non-hydrogen atoms were refined aniso-
tropically by full-matrix least-squares based on F. All other H
atoms were generated geometrically and were included in the
refinement in the riding model approximation. The lattice
constants were refined by least-square refinement using 16338
total reflections (3.459° < ª < 29.290°), 3501 unique reflec-
tions (Rint = 0.037). Structure solution and refinement based on
2119 reflections with I > 3·(I) and 199 parameters gave final
R = 0.0325, wR = 0.0355, and S = 1.07. Selected crystallo-
graphic data, experimental conditions, and relevant features of
the structural refinements for all the complexes are summarized
in Table 1.
0
3
4
3
5
gram The structures were solved by direct method using the
program SIR97 and refined with the program CRYSTALS.
3
6
37
All non-hydrogen atoms were refined anisotropically by full-
matrix least-squares based on F. All other H atoms were
generated geometrically and were included in the refinement in
the riding model approximation. The lattice constants were
refined by least-square refinement using 7373 total reflections
Crystallographic data have been deposited with Cambridge
Crystallographic Data Centre: Deposition number CCDC-
(
2.630° < ª < 27.372°), 2037 unique reflections (Rint
=
0
.031). Structure solution and refinement based on 1327
805161, 790364, 790366, and 790365 for LH , 1, 2, and 3.
2
reflections with I > 3·(I) and 128 parameters gave final
R = 0.0395, wR = 0.0415, and S = 1.0955. The X-ray diffrac-
tion experiment of 1 was carried out at 293 K on an orange
plate shaped single crystal (0.02 mm © 0.05 mm © 0.10 mm).
The intensity data of 1 were collected with an Oxford
Diffraction XCALIBUR diffractometer34 containing area de-
tector and graphite monochromator using ½ scan technique
with Mo K¡ radiation (­ = 0.71073 ¡) and data reduction was
performed with CrysAlis RED program.38 The structures were
solved by direct method using the program SIR97 and refined
with the program CRYSTALS.37 All non-hydrogen atoms were
refined anisotropically by full-matrix least-squares based on F.
The lattice constants were refined by least-square refinement
using 8389 total reflections (3° < ª < 30°) and 4766 inde-
pendent reflections (Rint = 0.058). Structure solution and
refinement based on 2723 reflections with I > 2·(I) and 280
parameters gave final R = 0.0627, wR = 0.0514, and S = 1.11.
X-ray diffraction of 2 was carried out at 100(2) K on a red plate
shaped single crystal (0.42 mm © 0.24 mm © 0.06 mm). The
selected crystal was mounted on a X8 ApexII Bruker area
diffractometer with Mo K¡ radiation (­ = 0.71073 ¡). Data
reduction was performed with SAINT program.39 The lattice
constants were refined by least-square refinement using 15256
total reflections (1.54° < ª < 25.97°), 3558 unique reflections
Copies of the 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, U.K.; Fax: +44 1223 336033; e-mail:
deposit@ccdc.cam.ac.uk).
Results and Discussion
Fourier Transform Infrared Spectra. The IR spectra of
the complexes 1­3 were analyzed in comparison with that of
39
¹1
the free ligand LH in the region 4000­400 cm . The main
2
FT-IR bands are listed in Table 2 and a representative IR
spectrum of 2 is depicted in Figure S1. In the IR spectrum of
the free hydrazone ligand, imine (¯C=N) stretching band
¹
1
appeared at 1667 cm , but for the complexes the characteristic
imine bands were observed at lower stretching frequencies:
¹
1
1591, 1577, and 1624 cm respectively for the complexes 1­3,
indicating the coordination of the imine nitrogen atom to the
4
2,43
metal center.
¯
signal for the amide moiety (­CONH­)
C=O
¹
1
centered at 1608 cm in LH undergoes lower frequency shift
to 1544, 1542, and 1600 cm in complexes 1­3 respectively.
The broad band around 3100 cm for N­H stretching in the
spectrum of the ligand is shifted to 2928 and 3058 cm in
2
¹
1
¹
1
¹1
1 and 3 confirming the possibility of the amide moiety to
coordinate to the metal center in its ketonic form and the amide
protons to be involved in hydrogen-bonding interactions, but
the ¯N­H signal is absent in 2, suggesting the possibility of
second deprotonation of the ligand. Ligand coordination to the
metal center can further be substantiated by prominent ¯M­N
bands (M = Co, Mn, and Zn for 1, 2, and 3 respectively) at
(
3
Rint = 0.0532). Structure solution and refinement based on
558 reflections with I > 2·(I) and 266 parameters gave final
R = 0.0389, wR = 0.0787, and S = 1.021. Data collection and
data reduction were done with the APEX 240 and SAINT
programs respectively. The structures were solved by direct
methods using the SHELXS-97 and refined by full-matrix
least-squares methods in SHELXL-97.41 All non-hydrogen
atoms were refined anisotropically by full-matrix least-squares
39
¹
1
459, 444, and 438 cm
in the respective spectra of the
44
complexes 1­3. In the spectrum of 3 some new bands
appeared which were not present in the spectra of the free
ligand as well as in 1 and 2 and can be attributed to various
stretching frequencies of trifluoroacetate anion. Strong C­F
2
based on F . The H atoms were generated geometrically and
were included in the refinement in the riding model approx-
imation. The X-ray diffraction experiment of 3 was carried out
at 293 K on a colorless cubic single crystal (0.11 mm ©
¹
1
¹
stretching bands at 1189 cm and asymmetric COO stretch-
¹
1
ing at 1685 cm
indicate the presence of trifluoroacetate
4
5
0
.11 mm © 0.12 mm). The intensity data of 3 were collected
moiety in 3, also confirmed by the crystal structure.
Electronic Spectra. The electronic spectra for complexes
1­3 were analyzed in comparison with that of the free ligand
3
4
with an Oxford Diffraction XCALIBUR diffractometer
containing area detector and graphite monochromator using
multi scans with Mo K¡ radiation (­ = 0.71073 ¡). Empirical
absorption corrections were carried out by multi scans using
LH in the region 800­200 nm in HPLC grade acetonitrile as
2
well as in solid state using paraffin oil matrix. The observed

7
68
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
Variable Ligand Coordination Modes
Table 1. Crystal Structure Parameters of LH2, 1, 2, and 3
Compounds
LH2
1
2
3
Formula
Mol. weight/g mol
T/K
C10H12N2O2
192.22
293
C21H26CoN4O5
473.39
293
C20H20MnN4O4
435.34
100(2)
C24H22F6N4O8Zn2
739.21
293
¹1
Wavelength/¡
Crystal system
Space group
a/¡
b/¡
c/¡
0.71073
Monoclinic
P 1 21/c 1
7.5632(12)
13.637(2)
9.6739(15)
90
103.412(2)
90
970.6(3)
4
0.71073
Triclinic
P1 (No. 2)
0.71073
Triclinic
P1
0.71073
Monoclinic
C2/c (No. 15)
21.311(5)
9.012(5)
15.578(5)
90
109.306(5)
90
2824(2)
4
ꢀ
ꢀ
8.182(1)
10.559(1)
12.456(2)
73.12(1)
88.90(1)
88.67(1)
1029.4(2)
2
7.3651(17)
10.094(3)
13.558(3)
80.635(8)
79.573(8)
72.508(8)
939.1(4)
2
¡
¢
/°
/°
£
V/¡
/°
3
Z
¹
3
D/g cm
®
1.32
0.93
1.527
0.876
1.539
0.739
1.739
1.793
¹1
/mm
F(000)
408
494
450
1488
0.11 © 0.11 © 0.12
3.459 to 29.290°
16338
3501
Crystal size/mm3
ª range
0.08 © 0.24 © 0.25
2.630 to 27.372°
7373
2037
0.031
0.02 © 0.05 © 0.10
3 to 30°
8389
4766
0.058
0.42 © 0.24 © 0.06
1.54 to 25.97°
15256
3558
0.0532
Reflections collected
Ind. reflections
R(int)
0.037
Reflections used
Parameters refined
S
1327
128
1.0955
2723
280
1.11
3558
266
1.021
2119
199
1.07
R = 0.0395, wR = 0.0415 R = 0.0627, wR = 0.0514 R = 0.0389, wR = 0.0787 R = 0.0325, wR = 0.0355
Final R indices
[
I > 3·(I)]
[I > 2·(I)]
[I > 2·(I)]
[I > 3·(I)]
¹3
Δμmax and Δμmin/e ¡
0.23 and ¹0.14
0.96 and ¹0.70
0.341 and ¹0.383
0.67 and ¹0.47
Table 2. Important Band Positions of FT-IR and UV­vis Spectra
Compounds
LH2
1
2
3
¹1
FT-IR/cm
¯C=N 1667
¯C=N 1591
¯C=O 1544
¯N­H 2928
¯C=N 1577
¯C=O 1542
¯Mn­N 444
¯C=N 1624
¯C=O 1600
¯N­H 3058
¯Zn­N 438
¯
¯
C=O 1608
N­H 3100
¯
Co­N 459
¯
¯
C­F 1189
COOꢀðasymÞ 1685
UV­vis in CH3CN/nm
UV­vis in nujol/nm
³­³* 246
n­³* 320
³­³* 300
n­³* 382
LMCT 238
³­³* 291
n­³* 350
LMCT 221
³­³* 252
n­³* 357
4
4
A2g ¼ T2g 553
A2g ¼ T1g(F) 419
4
4
³­³* 250
n­³* 324
³­³* 304
n­³* 388
LMCT 242
³­³* 296
n­³* 356
LMCT 228
³­³* 265
n­³* 364
4
4
A2g ¼ T2g 558
4
4
A2g ¼ T1g(F) 426
UV­vis bands in both phases are listed in Table 2 and the
spectra in CH CN are shown in Figure 1. In CH CN solution
relating to phenoxide lone pair and the ³* orbital of imine i.e.,
[lp(phenoxide) ¼ ³*(imine)] within the Schiff base ligand.
3
3
the UV­vis spectrum of the Schiff base ligand LH exhibited
The ligand-centered transition bands of LH at 246 and 320 nm
2
2
two intense absorption bands at 246 and 320 nm which can be
attributed to ³ ¼ ³* (C=N) and n ¼ ³* transitions possibly
may have suffered large bathochromic shifts in the spectra of
the complexes appearing at 300 and 382 nm in 1, at 291 and

D. Sadhukhan et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
769
Wavelength/nm
Figure 1. UV­vis spectra of LH2 (green), 1 (blue), 2 (red),
and 3 (black).
3
50 nm (shoulder) in 2, and at 252 and 357 nm in 3. The sharp
and intense bands at 238 nm in 1 and 221 nm in 2 can be
considered as a L ¼ M charge-transfer transition since no band
in this region was observed in the spectra of the free ligand
II
LH2 and the zinc complex 3. The LMCT band for Co
complexes are generally expected in the visible region
4
6,47
but for 1 it is significantly blue shifted due to the presence of
strong axial donor group (imine) which destabilizes the metal
dz
2
orbital, thus creating a larger energy gap between ³*(imine)
4
8
and dz
2
(metal). For 2 the LMCT band position is in good
IV
49
agreement with a previously reported Mn system. The
d ¼ d transition is only clearly visible and well resolved. For
the octahedral Mn system three possible spin allowed d ¼ d
transitions are: A2g ¼ T2g, A2g ¼ T1g(F), and A2g ¼
T (P). Two broad bands of relatively weaker intensity
1
Figure 2. Cyclic voltammogram of 1 (a) and 2 (b).
IV
H142
4
4
4
4
4
141H
H61
H143
4
50
H101
N10
g
H131
C14
C8
centered at 553 and 419 nm in
2 can be assigned
to A2g ¼ T and 4A2g ¼ T (F). The 4A2g ¼ T (P)
4
4
4
51
4
2g
1g
1g
5
1H
C13
H132
C6
transition may have been obscured by the [lp(phenoxide) ¼
*(imine)] charge-transfer band. The unambiguous assignment
C5
C4
C7
C2
N9
C11
O12
³
H133
of d ¼ d transitions in 1 is very difficult due to very weak
absorption intensity of the d­d bands in the visible region in an
C3
O1
41H
H11
II
octahedral Co complex.
The UV­vis bands obtained in solid state for all the
compounds are in good agreement with the solution phase
spectra (Table 2). The small shifts in solution phase are due to
H31
Scheme 2. Proton numbering scheme for the 1H NMR
spectra of LH2.
solvatochromic effect of the polar solvent (CH CN) used.
3
Cyclic Voltammetric Studies of 1 and 2. Redox properties
of 1 and 2 were investigated by cyclic voltammetry in HPLC
grade acetonitrile medium with tetrabutylammonium perchlo-
rate as supporting electrolyte at a scan rate of 0.05 V s . The
cyclic voltammogram of 1 and 2 are depicted in Figures 2a and
more stabilized and in lower oxidation state than the Mn
species.
¹
1
1H NMR Spectroscopy of the Free Ligand LH2. 1H NMR
spectroscopy has been used to extract information regarding the
II
2
b respectively. The Co complex 1 showed an irreversible
exact conformation of the ligand LH in free state. The proton
2
IV
reductive response at ¹0.71 V. The Mn complex 2 showed a
single electron Mn ¼ Mn reduction at ¹0.064 Vand during
the anodic scan the reverse oxidative response was found at
numbering is depicted in Scheme 2 and the NMR spectrum of
IV
III
LH is shown in Figure 3. In the NMR spectrum of the free
2
ligand LH a broad 1H singlet peak was observed due to the
2
+
0.086 V. Another oxidation peak was present in the voltam-
amide proton (H101) at 8.64 ppm and another broad 1H singlet
was obtained at 11.76 ppm for the phenolic ­OH proton (H11).
These two peaks indicate that among the two ionic protons in
the ligand one is associated to the phenoxo oxygen and the
other to the amido nitrogen atoms, so the other oxygen atom
(O12) exists in keto conformation in the free ligand. The
broadening of the signals may have occurred due to involve-
mogram of 2 at more positive potential (+1.252 V) which
probably corresponds to L2 to L oxidation and was absent in
the voltammogram of 1. This oxidation peak at higher positive
potential indicates that the ligand exists in a lower oxidation
state in 2 than in 1. Additionally the more negative reduction
potential of 1 compared to 2 indicates that the Co ion is much
¹
¹

7
70
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
Variable Ligand Coordination Modes
Table 3. Selected Bond Distances and Bond Angles of LH2
Bond lengths/¡
Bond angles/°
O1­C2
C2­C3
C2­C7
C3­C4
C4­C5
C5­C6
C6­C7
C7­C8
C8­N9
C8­C14
N9­N10
N10­C11
C11­O12
C11­C13
1.356(2)
1.392(2)
1.415(2)
1.371(3)
1.378(3)
1.380(3)
1.396(2)
1.477(2)
1.289(2)
1.496(2)
1.3701(18)
1.358(2)
1.2200(19)
1.493(2)
O1­C2­C3
O1­C2­C7
C3­C2­C7
C2­C3­C4
C3­C4­C5
C4­C5­C6
C5­C6­C7
C2­C7­C6
C2­C7­C8
C6­C7­C8
C7­C8­N9
C7­C8­C14
N9­C8­C14
C8­N9­N10
N9­N10­C11
116.77(15)
123.06(15)
120.17(16)
120.71(16)
120.21(17)
119.71(18)
122.06(16)
117.13(15)
121.81(14)
121.06(14)
115.10(13)
120.55(14)
124.34(15)
121.65(13)
117.12(12)
Figure 3. 1H NMR spectrum of LH2.
N10­C11­O12 121.22(16)
N10­C11­C13 115.23(14)
O12­C11­C13 123.55(16)
Figure 4. Perspective view of the asymmetric unit of LH2.
ment of the protons in intra- and intermolecular hydrogen-
bonding interactions.52 The methyl protons attached to C13
enjoy deshielding from both O12 and N10 and appear as a 3H
singlet at 2.36 ppm and is downfield shifted compared to the
methyl protons attached to C14 which undergo paramagnetic
deshielding from N9 only and appear as a 3H singlet at
2
.32 ppm. Among the aromatic protons H31 being adjacent to
the phenolic ­OH group is distinctly deshielded compared to
the others and appears as a 1H doublet within 7.46 to 7.49 ppm
and the other aromatic protons appear as a multiplet within the
Figure 5. Crystal packing of LH2, showing the hydrogen-
bonded one-dimensional network.
region 6.88 to 7.05 ppm. The spectrum of LH contains a broad
2
singlet peak at 1.62 ppm for water molecule and a sharp singlet
at 7.26 ppm for CHCl3 which may be present as impurities. The
results obtained from the NMR spectrum are in agreement with
the structure of the free ligand obtained by the X-ray analysis
Table 4. Hydrogen-Bond Parameters for LH2, 1, 2, and 3
d(D­H) d(H£A) d(D£A) ¾(DHA)
D­H£A
(Figure 4).
/¡
/¡
/¡
/°
Crystal Structure of the Free Ligand (LH2). The single-
LH2
N10­H101£O12 0.85
2.07 2.907(3) 166.11
1.78 2.532(3) 148.38
1.97 2.808(7) 166
1.90 2.688(7) 162
2.44 3.361(7) 163
crystal structure of LH is evaluated in order to establish its
2
O1­H11£N9
0.84
0.86
0.82
0.95
0.98
actual configuration in metal free state. The asymmetric unit
of the free ligand is shown in Figure 4 and the bond lengths
and bond angles are listed in Table 3. The asymmetric unit
clearly shows that the tridentate Schiff base contains an
imine functional group, a phenolic hydroxy group and a
secondary amido carbonyl functionality. The phenolic C2­O1
bond distance is 1.356(2) ¡, distinctly longer than the ketonic
C11­O12 bond distance 1.2200(19) ¡. Thus it is evident from
the structure that among the two oxygen donor sites of the
ONO donor ligand one oxygen is enolic in nature and the other
is ketonic.
Complex 1 N24­H5£O41
O41­H1£O14
C27­H271£O1
Complex 2 C6­H6£O26
2.609 3.486
2.53 3.463
2.645 3.395
153
158
133
C27­H27B£O15 0.98
C14­H14B£O1
0.98
0.84
Complex 3 N11­H3£O23
2.13 2.947(7) 164
intramolecularly hydrogen bonded to the imine nitrogen (N9)
forms a stable six-membered ring assembly. The secondary
amido proton attached to N10 has a favorable orientation to
form intermolecular hydrogen bond with the ketonic oxygen
(O12) of the adjacent unit and by reiteration of this intermo-
lecular interaction the 1D supramolecular chain-like polymer
The crystal packing of LH can be envisaged as a tape-like
2
1
D supramolecular network resulting from intra- and intermo-
lecular hydrogen-bonding interactions shown in Figure 5 and
listed in Table 4. The phenolic proton associated with O1 being

D. Sadhukhan et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
771
resulted along the crystallographic c axis. A closer look at the
crystal packing reveals that any two adjacent molecules reside
in two different planes. Thus every alternative molecule of the
polymeric chain defines two molecular planes connected like a
hinge at an angle 50.07°.
and N25) and the deprotonated phenolic oxygens (O14 and
O34). The bond dimensions in the two ligands differ slightly in
1 (Table 5) but confirms their coordination via the ketonic form
(Form II in Scheme 1). The ligands are disposed around the
metal center in meridional orientation with the phenolic and
ketonic oxygens cis to each other and the azomethine nitrogen
Crystal Structure of [Co(LH) ]¢CH OH (1).
The
2
3
II
perspective view of 1 is shown in Figure 6 and the bonding
atoms trans. Thus Co adopts distorted octahedral coordination
II
parameters are listed in Table 5. In 1 the Co ion forms the bis-
geometry. The twelve cis angles range from 84.5(1) to 95.7(1)°
and the three trans angles held by O1­Co1­O14 (179.0(2)°),
N5­Co1­N25 (172.2(2)°), and O21­Co1­O34 (178.8(2)°)
suggest that these are quite close to the ideal 90 (cis)
and 180° (trans) values of a perfect octahedron. The slight
distortion from the idealized geometry may be attributed to the
restricted bite angles imposed by the planar tridentate Schiff
bases. The phenolic oxygens (O14 and O34) and two ketonic
oxygens (O1 and O21) are very close to the mean plane passing
through them and define the equatorial plane of the CoN O
chelated complex with two mono anionic tridentate ONO donor
II
hydrazone ligands. The ligands coordinate the Co ion via the
ketonic oxygen (O1 and O21), the azomethine nitrogens (N5
2
4
chromophore, while two axial sites are occupied by the two
azomethine nitrogen atoms (N5 and N25). The mean planes
defined by the donor atoms of the two ligands are almost
perfectly orthogonal to each-other being inclined at an angle of
8
9.41°.
The crystal packing of 1 exhibits intermolecular N­H£O,
O­H£O, and C­H£O hydrogen bonds shown in Figure 7
and listed in Table 4. The intermolecular hydrogen bonding
is mainly assisted by the methanol molecule present in the
lattice. Two neighboring monomeric units are linked through
methanol molecules by a pair of cooperative hydrogen bonds
N24­H5£O41 and O41­H1£O14 with the formation of a
Figure 6. Perspective view of the asymmetric unit of 1.
Table 5. Selected Bond Distances and Bond Angles of 1, 2, and 3
1
2
3
Bond lengths/¡
Co1­O1
Co1­O21
Co1­N5
Co1­N25
Co1­O14
Co1­O34
C2­O1
1.875(3)
1.923(3)
1.861(3)
1.902(3)
1.868(3)
1.849(3)
1.293(5)
1.241(5)
Mn1­O15
Mn1­O1
Mn1­O26
Mn1­O12
Mn1­N23
Mn1­N9
C11­O12
C25­O26
1.8448(17)
1.8493(17)
1.9067(17)
1.9161(18)
1.959(2)
1.966(2)
1.314(3)
1.315(3)
Zn1­O1
Zn1­O14
Zn1­O1
Zn1­O21
Zn1­N10
C12­O14
1.989(2)
2.069(2)
2.004(2)
1.978(2)
2.101(2)
1.241(3)
C22­O21
Bond angles/°
O1­Co1­N5
84.5(1)
179.0(2)
95.7(1)
90.4(2)
91.4(1)
88.6(2)
89.0(1)
172.2(2)
90.8(1)
84.3(1)
90.3(2)
89.6(1)
90.7(2)
178.8(2)
94.8(2)
O15­Mn1­O1
88.90(8)
170.93(8)
88.42(8)
89.77(8)
170.08(7)
94.33(7)
91.04(8)
97.43(8)
80.72(8)
92.42(8)
95.09(8)
90.20(8)
93.58(8)
80.13(8)
170.31(9)
O1­Zn1­O1
78.35(8)
84.21(9)
145.0(1)
104.11(9)
115.65(9)
100.95(9)
140.08(9)
100.20(8)
78.02(9)
111.1(1)
98.5(1)
O1­Co1­O14
N5­Co1­O14
O1­Co1­O21
N5­Co1­O21
O14­Co1­O21
O1­Co1­N25
N5­Co1­N25
O14­Co1­N25
O21­Co1­N25
O1­Co1­O34
N5­Co1­O34
O14­Co1­O34
O21­Co1­O34
N25­Co1­O34
O15­Mn1­O26
O1­Mn1­O26
O15­Mn1­O12
O1­Mn1­O12
O26­Mn1­O12
O15­Mn1­N23
O1­Mn1­N23
O26­Mn1­N23
O12­Mn1­N23
O15­Mn1­N9
O1­Mn1­N9
O1­Zn1­N10
O1­Zn1­O14
O1­Zn1­O21
N10­Zn1­O21
Zn1­O1­Zn1
O1­Zn1­N10
O1­Zn1­O14
N10­Zn1­O14
O1­Zn1­O21
O14­Zn1­O21
O26­Mn1­N9
O12­Mn1­N9
N23­Mn1­N9

7
72
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
Variable Ligand Coordination Modes
Figure 9. Packing diagram of 2, showing the zig-zag
bilayer 1D supramolecular architecture.
5
3­55
and dinuclear octahedral complexes having MnN O core.
2
4
The O­Mn­O and O­Mn­N cis angles have an average value
of 90.17° whereas the three trans angles deviate by about 10°
from ideal 180° value. The angle between the planes defined by
the ONO donor sets of the two ligands is 86.75°, close to 90°
suggesting that the ligands are essentially orthogonal.
Figure 7. Crystal packing of 1, showing the methanol
mediated centrosymmetric, cooperatively hydrogen-
bonded 1D bilayer network.
A closer look at the amido C­O bond distance in free LH2,
1
, and 2 reveals that this distance is 1.315(3) ¡ in 2, distinctly
longer than the amido C­O linkage in free LH and 1 (1.220(2)
2
and 1.267(5) ¡ respectively) and confirms the single bond
character of this C­O bond in complex 2 in contrast to the
double bond features in LH and 1. Thus quantitative evidence
2
in favor of enolic coordination of amido carbonyl group in 2
and ketonic coordination in 1 can be rationalized. These
different coordination modes of the ligand in 1 and 2 are
reflected in their hydrogen-bonding patterns. As the ligand in 2
is doubly deprotonated there is no favorable situation for usual
N­H£O and O­H£O hydrogen bonding as observed in LH2
and 1 but the adjacent mononuclear units are close packed
through the weak C­H£O interaction shown in Figure S2.
Thus three cooperative C­H£O hydrogen-bonding interactions
listed in Table 4 generate a bilayer supramolecular chain along
the crystallographic a axis in which the mononuclear unit of
each layer partly interdigitate between two neighboring units of
another layer (Figure 9) to strengthen the supramolecular self-
assembly.
Figure 8. Perspective view of the asymmetric unit of 2.
centrosymmetric dimer (Symmetry transformation: ¹x, ¹y,
z). Interaction between two such adjacent dimers is further
supported by another centrosymmetric nonclassical C27­
H271£O1 hydrogen-bonding interaction along the crystallo-
graphic a axis forming a one dimensional bilayer zig-zag
supramolecular assembly.
¹
Crystal Structure of [Zn(LH)(OOCCF )] (3).
The
3
2
II
perspective view of the asymmetric unit of the Zn complex 3
is shown in Figure 10 and the required bond lengths and bond
angles are listed in Table 5. 3 encounters a crystallographically
imposed rotational symmetry element (C2 axis) forming a
II
Crystal Structure of [Mn(L) ] (2). 2 consists of a central
bis(® -phenoxo) bridged dinuclear structure with each Zn ion
2
2
MnIV cation surrounded by two dianionic tridentate ONO
being penta-coordinated sharing two phenoxo oxygens from
two symmetry related ligand fragments (Figure S3). It is to
be noted here that unlike 1 and 2 the ligand in 3 exhibits
2
¹
donor hydrazone ligands (L ) (Figure 8). The bond dimen-
sions of the MnN O chromophore are listed in Table 5. The
2
4
overall geometry about the central Mn ion is octahedral with
the meridional disposition of the two tridentate ligands. As in 1,
the mean equatorial plane around the central metal ion in 2 is
also formed by the four oxygen atoms and the two azomethine
nitrogens occupy the trans (axial) positions to complete the
octahedron. Unlike in 1, the ligands in 2 coordinate the Mn ion
via the enol tautomeric form and behave as a dianionic species
to stabilize the +IV oxidation state of the Mn ion (Form III of
Scheme 1). The average Mn­N and Mn­O bond lengths for 2
are 1.9625 and 1.8792 ¡, respectively which are in good
the ® -bridging mode of the phenoxo oxygen (Form IV of
2
Scheme 1) which results in an increased nuclearity from
mononuclear complexes 1 and 2 to symmetric dinuclear
complex 3 along with growing symmetry elements leading to
triclinic (1 and 2) to monoclinic (3) space group. The Zn1 ion
in 3 adopts a square-pyramidal geometry as defined by the
Addison parameter ¸ = 0.082, (¸ = «¢ ¹ ¡«/60° where ¢ and
¡ are the two largest angles around the central atom; ¸ = 0 and
1 for perfect square-pyramidal and trigonal-bipyramidal geo-
5
6
metries, respectively). The three coordination sites of the
equatorial plane defined by O14, N10, O1, and O1 of another
IV
agreement with those for various reported Mn mononuclear

D. Sadhukhan et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
773
Figure 10. Perspective view of the asymmetric unit of 3.
Figure 11. The crystal packing of 3, showing the (4, 4) grid
D supramolecular architecture formed by the N­H£O
2
hydrogen-bonding interactions among the butterfly shaped
dimeric units related by ba glide plane symmetry.
unit (symmetry transformation: ¹x, y, 1/2 ¹ z) are occupied by
the ONO donor set of the Schiff base ligand. The ONO donor
ligand forms a five-membered chelate ring with the help of
the keto oxygen (O14) and the imine nitrogen (N10) and a
six-membered chelate ring using the imine nitrogen (N10)
and bridging phenoxo oxygen (O1) around the metal center
Zn1. The fourth equatorial position is blocked by another
bridging phenoxo oxygen which actually belongs to the other
b
symmetry related half of the Zn dimer. It is worth mentioning
2
here that the amido carbonyl group involving C12­O14 linkage
coordinates the Zn ion in ketonic form as in 1 and the C­O
a
II
bond distances in free LH , 1, and 3 are quite comparable but
Figure 12. A space filling model of 3, showing distinctly
visible supramolecular nanopores along c axis.
2
differ from those of 2 (Tables 3 and 5). The axial position
II
of the Zn ion is occupied by the oxygen atom (O21) of
a terminally coordinated trifluoroacetate anion. Thus each
II
Zn ion describes a distorted square-pyramidal geometry
within a NO coordination sphere. The distortion from ideal
4
square-pyramidal geometry as evident from the bond dimen-
sions is further supported by the axial displacement of the
Zn1 ion from the mean equatorial plane by 0.592 ¡. The
intradimer Zn£Zn distance is 3.080 ¡ and is consistent with
the reported Zn£Zn separations in double phenoxo-bridged
3
0,57
Zn complexes.
A further insight into the intermolecular interaction in 3
exhibits that the discrete butterfly shaped dimeric units are
associated through the N­H£O hydrogen bonds (Figure 11 and
Table 4) occurring between the amido nitrogen (N11) of one
dinuclear unit to the noncoordinated trifluoroacetato oxygen
(
(
O23) of the neighboring unit related by glide plane symmetry
ba glide) on either side. Thus the supramolecular self-assembly
of 3 can be best described as a 2D (4, 4) grid topology by
considering the dinuclear metallo-organic units as a node and
the N11­H3£O23 bonds to be linker (Figure 11). The single
layer 2D network exhibits supramolecular nanoporosity in the
structure having a dimension of 9.524 © 18.369 ¡ (based on
nearest intermolecular Zn£Zn distance along the b and a axes
respectively). A space filling model of the crystal packing
Figure 13. X-band EPR spectra of 1 recorded on the
polycrystalline powder (a) at 100 K and (b) at 298 K. With
the eight lines is indicated the hyperfine splitting due to
59
Co nucleus.
EPR Spectroscopic Studies of 1 and 2. EPR spectra of 1
recorded on polycrystalline powder are characterized by a
similar pattern from 100 to 298 K (Figure 13). They appear to
be close to axial symmetry with a negligible rhombicity. The g
(Figure 12) clearly shows the nanopores enclosed by the
supramolecular (4, 4) grids.

7
74
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
Variable Ligand Coordination Modes
values measured at liquid nitrogen temperature are g = 2.363
¦
7
and g = 2.016. The spectral features support a low-spin d
«
«
configuration with the unpaired electron in the dz
2
orbital. On
the whole, the spectra closely resemble those for other low-spin
II
58­65
Co species with axial or slight rhombic symmetry.
Theoretical treatments of the spin Hamiltonian parameters for
such situations have been developed by several authors, in
which g (and A) values can be related to the ground-state
electronic configuration and the energy separation of the
2
66­68
low-lying doublet ( A ) and the quartet excited states;
up to
1
first order approximation g values can be expressed by the
following equations:
6
­
g? ¼ ge þ
> 2:0023
ð3Þ
ꢁ
E
gk ¼ ge ꢃ 2:0023
ð4Þ
7
where ­ is the spin­orbit coupling (higher than 0 for a d
configuration) and ¦E is the energy difference between the set
Figure 14. X-band EPR spectra of 2 at room temperature,
(
d , d ) and d orbital.69 From eqs 3 and 4, it emerges that
z2
yz xz
(
a) recorded on the polycrystalline powder and (b) in
g > g μ 2, in agreement with the experimental observations.
At liquid nitrogen temperature, the coupling between the
¦
««
CH3CN. With the asterisk is indicated the hyperfine
splitting due to Mn nucleus.
55
unpaired electron and 59Co nucleus (characterized by nuclear
spin number I = 7/2 and natural abundance of 100%) is
detected; owing to such an interaction, it is expected that each
transition splits into 2I + 1 = 8 lines. They can be resolved
around the parallel region and appears partly observable in the
is reached, exhibiting a strong signal at g μ 2 region. 2 shows
a strong band at g = 2.01 and a weak band at g = 3.78;
therefore, it belongs to the second situation described
above and D ¹ 0.15 cm (h¯ μ 0.31 cm at X-band frequen-
cies). A simulation of the spectrum suggests that D is around
¹
4
¹1
¹1
¹1
perpendicular region; the approximated A of 96 © 10 cm
««
is compatible with the structure of 1 and with the data reported
5
8,59,62,64
14
¹1
in the literature.
No hyperfine coupling with N nuclei
0.08 cm and E/D around 0.14; the value of E º 0 can be
is observed. EPR spectrum at room temperature (Figure 13b)
also displays a very broad signal centered at 1380 Gauss with
g μ 4.74; this is possibly due to a high-spin Co contribution
explained with the rhombicity of the molecular geometry
of 2 (Mn­O1(O15) μ 1.85, Mn­O12(O26) μ 1.91, and Mn­
N9(N23) μ 1.96 ¡).
II
that occurs with increasing temperature: the value of g > 4 is
characteristic of such electronic configurations.7
The features are retained in the organic solvents, and
0­75
the spectrum recorded in CH CN is shown in Figure 14b.
3
EPR spectra of 1 dissolved in coordinating (DMF), slightly
Analogous signals are obtained in DMF or in a mixture
CH Cl /toluene 50/50 v:v. In the solution too, all the lines are
coordinating (CH CN) or in noncoordinating solvents (mixture
3
2
2
5
5
CH Cl /toluene 50/50 v:v) are comparable with those recorded
extremely broad; as a consequence, no Mn hyperfine splitting
was observable in the band at lower field and only three of the
six expected transitions can be observed in the broad resonance
centered at g μ 2 (indicated by an asterisk in Figure 14b):
2
2
on the powder and demonstrate that the solid-state structure is
retained in solution.
The X-band EPR spectrum recorded on a polycrystalline
sample of 2 is displayed in Figure 14a. The major feature of the
spectrum is a strong and well-defined g μ 2 resonance and a
weak, broad signal at low field. The complexity of interpreting
5
5
however the magnitude of the Mn hyperfine coupling (79 G)
IV
85
is consistent with previous reports for the Mn species. For
example, for the compound [Mn(salahp)], where H salahp is 1-
2
3
IV
III
the EPR spectra of d (Mn and Cr ) ions depending on
the magnitude of the zero-field splitting D and rhombic
hydroxy-3-salicylideneaminopropane, with identical MnO N
4
2
coordination and [(O(phen), N(imine), and O(alk)] donor set, a
7
6­78
24,86,87
distortion E has been widely discussed in the literature.
value of 77 G has been reported.
Thus, both the spectra
Such a complexity can be simplified in an axial field (E/D = 0)
and when the axial D is either much larger (2D º h¯) or
much smaller (2D ¹ h¯) than the applied microwave frequen-
cy. In the first case two signals occur, with the first being
a strong transition at the low field and the second a weaker
recorded on the solid sample and in solution support an
oxidation state of +IV for manganese.
Fluorescence Spectroscopic Study of LH and 3. The
2
steady state fluorescence emission spectra of the free ligand
LH and the zinc complex 3 in acetonitrile solution at room
2
IV
g μ 2 component. This observation is true for Mn complexes
temperature are shown in Figure 15. For the free ligand LH2
(­ex = 320 nm) there is a broad emission band at 449 nm. Upon
excitation in the UV region, 3 (­ex = 356 nm) exhibits a narrow
emission band with the maximum at 468 nm and a tail
extending up to 600 nm, indicating that it is a typical blue
emitter. A similar emission pattern, characteristic of imino-
7
9
80
like MnO formed by catecholate and sorbitolate, MnN O
6
4
2
8
1
formed by hexadentate amide­amino­phenolate,
MnN2O4 formed by hydroxyphenyl­imino­phenolate ligand.
and
8
2
In the second case, when D is small, the g μ 2 signal dominates
with relatively weak low-field signals. This is observed for
8
3
84
IV
24,29,30,86,87
thiohydroxamato and dithiocarbamato Mn species. The
EPR spectra become isotropic when the extreme limit of D = 0
phenolate complexes was also recently observed.
The emission maximum of 3 is distinctly (19 nm) red shifted

D. Sadhukhan et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
775
400
500
600
700
wavelength/nm
Figure 16. Solid-state fluorescence spectra of 3 (dark,
Wavelength/nm
­exc = 356 nm) and LH2 (gray, ­exc = 320 nm).
Figure 15. Emission spectra of LH2 (black line) and 3 (blue
line) in CH3CN following excitation at 320 and 356 nm for
LH2 and complex 3 respectively.
solid state at room temperature using a multichannel spec-
trometer fitted with an integrating sphere and are depicted in
Figure 16.
compared to the free ligand. The calculated fluorescence
quantum yield of 3 is 40.43%, significantly higher than that
recorded for the free ligand (0.15%).
Upon excitation at 356 nm, 3 exhibits a narrow emission
band centered at 440 nm and a tail expending up to 600 nm.
This emission pattern is very similar to the one previously
recorded in acetonitrile solution but with a hypsochromic shift
of the maximum of emission of 28 nm possibly due to stacking
interactions in the solid state. A similar emission pattern had
also been recently recorded for a dicyanoamide-bridged 2D
II
Luminescence properties of Zn complexes originate from
the organic ligand rather than LMCT because the d shell of the
central ion is completely filled.88 Therefore the large increase in
emission intensity and μ270 times enhancement of fluores-
II
93
cence quantum yield of 3 compared to the free ligand LH can
polynear Zn complex.
2
be rationalized by the presence of the zinc atom. The metal
plays a pivotal role in increasing the conformational rigidity
and the extent of conjugation of the ligand, thus restricting
energy loss via nonradiative decay such as vibrational motions
and/or photoinduced electron transfer (PET)89 leading to a
bright and intense emission. The hydrogen-bonding interaction
in the free ligand leads to 1D chain-like assembly whereas it
clips the complex molecules in 3 into a 2D supramolecular
sheet in the ground state. The hydrogen-bonding interactions
are expected to be stronger with increasing dipole moment of
the molecules in the excited state and stabilize the excited state
Upon excitation at 320 nm, LH exhibits a broad emission
2
spectrum with a maximum at 521 nm (Figure 16). This
spectrum differs significantly from the emission pattern
observed in acetonitrile solution, as a strong bathochromic
shift of 72 nm is observed. This is indicative of strong
intermolecular interactions in the solid state, as for instance,
the noncovalent interactions, the formation of excimers or
exciplexes.
The fluorescence quantum yields of LH and 3 have been
2
measured in the solid state with an absolute method based on
the use of the integrating sphere. The calculated fluorescence
quantum yield of 3 is 18%, which is twice lower than the value
obtained in acetonitrile and which may be attributed to self-
absorption processes.
9
0
of the species. But in solution state there is another
competitive influence of solvent molecules. The solvent
molecules may participate in hydrogen bonding with the
luminescent species and quench its luminescent properties by
bond vibration and other nonradiative processes. For com-
plexes [Co(LH) ]¢CH OH (1) and [Mn(L) ] (2) no fluores-
In contrast, the ligand LH displays a much higher quantum
2
yield in the solid state (25%) than in acetonitrile solution
(0.15%). It is surmised that the restricted motions in the solid
state drastically reduce the vibrational quenching phenomena
such as excited state proton transfer often observed with
2
3
2
cence emission spectra can be observed though the metal ions
II
play the same pivotal role as the Zn ion in 3 and impose
9
4
95
conformational rigidity to the ligand. Here the transition metal
salicylaldehyde and salicylideneaniline.
(
Co/Mn)­fluorophore (F) electron/energy transfer interaction
Conclusion
and d­d electronic transition results in quenching of fluores-
cence.
9
1,92
In conclusion this paper describes the differing coordination
behavior of an ONO donor hydrazone Schiff base ligand in the
presence of different metal ions. In its free state the ligand is
monobasic and shows interesting 1D supramolecular chain-like
assembly. In 1 the ligand coordinates in its tridentate mono-
negative keto form to stabilize the +II oxidation state of a
cobalt ion. In 2 the amido carbonyl group of the ligand
undergoes enolisation along with further deprotonation and
thus the ligand stabilizes the +IV oxidation state of a
Time-resolved luminescence measurement of 3 allowed the
intensity of the emission after a laser excitation pulse at 370 nm
to be followed. The decay shown in Figure S4 is clearly double
exponential. The decay function can be described by a fast
lifetime component ¸fast = 0.98 ns and a slow lifetime compo-
nent ¸slow = 2.93 ns.
The steady state fluorescence emission spectra of the free
ligand LH and the zinc complex 3 have been measured in the
2

7
76
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
Variable Ligand Coordination Modes
manganese ion. Apart from different oxidation states the ligand
also exhibits a variety of chelating properties. In 1 and 2 it
coordinates the metal ions via tridentate terminal fashion
leading to distorted octahedral bis chelate complexes, but in 3
7
S. Banerjee, S. Mondal, S. Sen, S. Das, D. L. Hughes, C.
Rizzoli, C. Desplanches, C. Mandal, S. Mitra, Dalton Trans. 2009,
849.
8
Gachhui, R. J. Butcher, A. M. Z. Slawin, C. Mandal, S. Mitra,
Polyhedron 2009, 28, 2785.
6
S. Banerjee, S. Mondal, W. Chakraborty, S. Sen, R.
the ligand shows tridentate bridging mode which leads to a
II
bis(® -phenoxo)-bridged dinuclear square-pyramidal Zn com-
2
9
S. Sridhar, M. Saravanan, A. Ramesh, Eur. J. Med. Chem.
001, 36, 615.
B. Bottari, R. Maccari, F. Monforte, R. Ottanà, E. Rotondo,
M. Vigorita, Bioorg. Med. Chem. Lett. 2000, 10, 657.
plex containing crystallographically imposed rotational sym-
2
metry (C ). All three complexes form supramolecular networks
2
1
0
via N­H£O, O­H£O, and C­H£O hydrogen bonds among
which the single layer 2D supramolecular (4, 4) grid network of
11
B. K. Kaymakçıoğlu, S. Rollas, Farmaco 2002, 57, 595.
E. W. Ainscough, A. M. Brodie, J. D. Ranford, J. M.
3
shows nanoporous characteristics.
1
2
Emphasis has been given in this work upon the different
Waters, Inorg. Chim. Acta 1995, 236, 83.
E. W. Ainscough, A. M. Brodie, A. J. Dobbs, J. D. Ranford,
J. M. Waters, Inorg. Chim. Acta 1998, 267, 27.
J. Easmon, G. Puerstinger, T. Roth, H. Fiebig, M. Jenny, W.
spectroscopic characterization and applications of the com-
plexes along with the ligand. Apart from the routine IR,
1
3
1
UV­vis spectroscopy LH2 was characterized by H NMR
1
4
spectroscopy which supports the ketonic form of the amido
carbonyl functionality of the ligand in free state. The
complexes 1 and 2 were characterized by cyclic voltammetry
and EPR spectroscopy. The X-band EPR spectra confirm the
presence of the cobalt ion in low-spin +II oxidation state and
manganese ion in +IV oxidation state, thus supporting the
monoanionic and dianionic coordination behavior of the ligand
in the respective complexes. The luminescence spectrum of 3
with respect to the free ligand shows that 3 is a typical blue
emitter. The ligand shows much enhanced luminescence in
solid state compared to solution state due to predominant
intermolecular interaction but this phenomenon is reversed in
the case of 3 probably due to self absorption process in solid
state.
Jaeger, G. Heinisch, J. Hofmann, Int. J. Cancer 2001, 94, 89.
15 L. Sacconi, J. Am. Chem. Soc. 1952, 74, 4503.
16 J. Chakraborty, S. Thakurta, G. Pilet, D. Luneau, S. Mitra,
Polyhedron 2009, 28, 819.
17 B. Mondal, M. G. B. Drew, T. Ghosh, Inorg. Chim. Acta
2009, 362, 3303.
18 B. Mondal, T. Ghosh, M. Sutradhar, G. Mukherjee,
M. G. B. Drew, T. Ghosh, Polyhedron 2008, 27, 2193.
1
9
P. B. Sreeja, M. R. P. Kurup, A. Kishore, C. Jasmin,
Polyhedron 2004, 23, 575.
A. Ray, S. Banerjee, R. J. Butcher, C. Desplanches, S.
Mitra, Polyhedron 2008, 27, 2409.
S. Sen, C. R. Choudhury, P. Talukder, S. Mitra, M.
2
0
2
1
Westerhausen, A. N. Kneifel, C. Desplanches, N. Daro, J.-P. Sutter,
Polyhedron 2006, 25, 1271.
2
2
13.
2
3
S. Pal, S. Pal, Eur. J. Inorg. Chem. 2003, 4244.
C. W. Tang, S. A. VanSlyke, Appl. Phys. Lett. 1987, 51,
D. Sadhukhan is thankful to University Grants Commission,
New Delhi, Government of India and S. Mitra acknowledges
Council of Scientific and Industrial Research, New Delhi,
Govt. of India for providing financial support to carry out
this work. The authors are also thankful to Mr. S. Roy,
Dr. C. R. Sinha, and Dr. N. Chattapadhyay, Department of
Chemistry, Jadavpur University, Kolkata, India for helping in
the fluorescence study.
9
2
4
T. Yu, W. Su, W. Li, Z. Hong, R. Hua, M. Li, B. Chu, B. Li,
Z. Zhang, Z. Z. Hu, Inorg. Chim. Acta 2006, 359, 2246.
V. Liuzzo, W. Oberhauser, A. Pucci, Inorg. Chem.
2
5
Commun. 2010, 13, 686.
26 V. V. Lukov, V. A. Kogan, S. I. Levchenkov, L. V. Zavada,
K. A. Lyssenko, O. V. Shishkin, Zh. Neorg. Khim. 1998, 43, 421.
2
7
F. B. Tamboura, M. Gaye, A. S. Sall, A. H. Barry, Y. Bah,
Supporting Information
Acta Crystallogr., Sect. E 2009, 65, m160.
It contains the FT-IR spectrum of 1 (Figure S1), the figure
presenting the H-bonds in 2 (Figure S2), the symmetric dimeric
view of 3 (Figure S3), and the time-resolved emission decay
curve of 3 (Figure S4). This materials are available free of
charge on the web at http://www.csj.jp/journals/bcsj/.
28 S. C. Chan, L. L. Koh, P.-H. Leung, J. D. Ranford, K. Y.
Sim, Inorg. Chim. Acta 1995, 236, 101.
2
9
C. Maxim, T. D. Pasatoiu, V. C. Kravtsov, S. Shova, C. A.
Muryn, R. E. P. Winpenny, F. Tuna, M. Andruh, Inorg. Chim. Acta
008, 361, 3903.
P. Roy, K. Dhara, M. Manassero, P. Banerjee, Inorg. Chim.
Acta 2009, 362, 2927.
C. A. Heller, R. A. Henry, B. A. McLaughlin, D. E. Bliss,
2
3
0
References
3
1
1
L. Antolini, L. P. Battaglia, A. B. Corradi, G.
Marcotrigiano, L. Menabue, G. C. Pellacani, J. Am. Chem. Soc.
985, 107, 1369.
S. Naskar, D. Mishra, S. K. Chattopadhyay, M. Corbella,
A. J. Blake, Dalton Trans. 2005, 2428.
A. Ray, C. Rizzoli, G. Pilet, C. Desplanches, E. Garribba,
E. Rentschler, S. Mitra, Eur. J. Inorg. Chem. 2009, 2915.
S. Patai, The Chemistry of the Carbon-Nitrogen Double
Bond, Interscience, New York, 1970.
J. Chem. Eng. Data 1974, 19, 214.
32 H. Ishida, S. Tobita, Y. Hasegawa, R. Katoh, K. Nozaki,
Coord. Chem. Rev. 2010, 254, 2449.
33 L. S. Rohwer, J. E. Martin, J. Lumin. 2005, 115, 77.
34 Xcalibur, Oxford-Diffraction, 2002.
35 Z. Otwinowski, W. Minor, in Methods in Enzymology:
Macromolecular Crystallography, Part A, ed. by C. W. Carter, Jr.,
R. M. Sweet, Academic Press, New York, 1997, Vol. 276,
pp. 307­326.
1
2
3
4
5
35.
6
J. R. Merchant, D. S. Chothia, J. Med. Chem. 1970, 13,
36 A. Altomare, M. C. Burla, M. Camalli, G. L. Cascarano, C.
Giacovazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori, R.
Spagna, J. Appl. Crystallogr. 1999, 32, 115.
3
J. R. Dilworth, Coord. Chem. Rev. 1976, 21, 29.

D. Sadhukhan et al.
D. J. Watkin, C. K. Prout, J. R. Carruthers, P. W. Betteridge,
CRISTAL, Issue 11, Chemical Crystallography Laboratory, Oxford,
UK, 1999.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
777
3
7
A. L. Rheingold, D. P. Goldberg, J. Am. Chem. Soc. 2004, 126,
2515.
65 A. Huber, L. Müller, H. Elias, R. Klement, M. Valko, Eur.
J. Inorg. Chem. 2005, 1459.
66 B. R. McGarvey, Can. J. Chem. 1975, 53, 2498.
67 W. C. Lin, Inorg. Chem. 1976, 15, 1114.
68 W. C. Lin, P. W. Lau, J. Am. Chem. Soc. 1976, 98, 1447.
69 R. S. Drago, Physical Methods in Chemistry, Saunders,
Philadelphia, 1977.
3
3
8
9
CrysAlis-RED 170, Oxford-Diffraction, 2002.
Area-Detector Integration Software, Siemens Industrial
Automation, Inc., Madison, WI, 1995.
APEX2 Version 2.1: Area Detector Control and Integration
4
0
Software, v. 6.45, Bruker Analytical X-ray Instruments, Inc.,
Madison, WI, USA, 2006.
4
4
4
1
2
3
G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112.
L. J. Farrugia, J. Appl. Crystallogr. 1999, 32, 837.
C. T. Yang, B. Moubaraki, K. S. Murray, J. D. Ranford, J. J.
70 R. H. Niswander, L. T. Taylor, J. Am. Chem. Soc. 1977, 99,
5935.
71 L. Banci, A. Bencini, C. Benelli, D. Gatteschi, C. Zanchini,
Struct. Bonding (Berlin, Ger.) 1982, 52, 37.
72 K. J. Berry, F. Moya, K. S. Murray, A. V. Bergen, B. O.
West, J. Chem. Soc., Dalton Trans. 1982, 109.
73 J. Zarembowitch, O. Kahn, Inorg. Chem. 1984, 23, 589.
74 P. Thuéry, J. Zarembowitch, Inorg. Chem. 1986, 25, 2001.
75 A. C. Rizzi, C. D. Brondino, R. Calvo, R. Baggio, M. T.
Garland, R. E. Rapp, Inorg. Chem. 2003, 42, 4409.
76 S. Pal, P. Ghosh, A. Chakravorty, Inorg. Chem. 1985, 24,
3704.
77 E. Pedersen, H. Toftlund, Inorg. Chem. 1974, 13, 1603.
78 J. C. Hempel, L. O. Morgan, W. B. Lewis, Inorg. Chem.
1970, 9, 2064.
79 K. D. Magers, C. G. Smith, D. T. Sawyer, Inorg. Chem.
1980, 19, 492.
Vittal, Inorg. Chem. 2001, 40, 5934.
K. Nakamoto, Infrared and Raman Spectra of Inorganic
4
4
and Coordination Compounds: Part A: Theory and Applications in
Inorganic Chemistry, 5th ed., John Wiley & Sons, Inc., New York,
1
997, p. 23.
Z. H. Sun, D. Xu, X. Q. Wang, G. H. Zhang, G. Yu, L. Y.
Zhu, H. L. Fan, Mater. Res. Bull. 2009, 44, 925.
A. Ray, G. M. Rosair, R. Kadam, S. Mitra, Polyhedron
009, 28, 796.
D. N. Kumar, B. S. Garg, J. Therm. Anal. Calorim. 2002,
9, 607.
K. Nakamoto, M. Suzuki, T. Ishiguro, M. Kozuka, Y.
Nishida, S. Kida, Inorg. Chem. 1980, 19, 2822.
4
5
4
6
2
4
7
6
4
8
4
5
9
0
D. M. Sherman, Am. Mineral. 1984, 69, 788.
A. B. P. Lever, Inorganic Electronic Spectroscopy, Elsevier,
80 D. T. Richens, D. T. Sawyer, J. Am. Chem. Soc. 1979, 101,
3681.
Amsterdam, 1984, p. 553.
R. A. Lal, S. Bhaumik, A. Lemtur, M. K. Singh, D.
Basumatari, S. Choudhury, A. De, A. Kumar, Inorg. Chim. Acta
006, 359, 3105.
W. Kemp, Organic Spectroscopy, 3rd ed., Palgrave Publish-
ers, 1991.
H. Torayama, T. Nishide, H. Asada, M. Fujiwara, T.
Matsushita, Polyhedron 1998, 17, 105.
H. Torayama, H. Asada, M. Fujiwara, T. Matsushita,
Polyhedron 1999, 17, 3859.
C. P. Pradeep, T. Htwe, P. S. Zacharias, S. K. Das, New J.
Chem. 2004, 28, 735.
A. W. Addison, T. N. Rao, J. Reedijk, J. V. Rijn, G. C.
Verschoor, J. Chem. Soc., Dalton Trans. 1984, 1349.
J. S. Matalobos, A. M. García-Deibe, M. Fondo, D.
Navarro, M. R. Bermejo, Inorg. Chem. Commun. 2004, 7, 311.
C. Busetto, F. Cariati, P. Fantucci, D. Galizzioli, F.
Morazzoni, J. Chem. Soc., Dalton Trans. 1973, 1712.
F. Cariati, D. Galizzioli, F. Morazzoni, C. Busetto, J. Chem.
Soc., Dalton Trans. 1975, 556.
A. Pezeshk, F. T. Greenway, G. Vincow, Inorg. Chem.
978, 17, 3421.
D. Reinen, A. Ozarowski, B. Jakob, J. Pebler, H.
Stratemeier, K. Wieghardt, I. Tolksdorf, Inorg. Chem. 1987, 26,
010.
5
1
81 S. K. Chandra, A. Chakravorty, Inorg. Chem. 1992, 31,
760.
82 T. M. Rajendiran, J. W. Kampf, V. L. Pecoraro, Inorg.
Chim. Acta 2002, 339, 497.
83 K. L. Brown, R. M. Golding, P. C. Healy, K. J. Jessop,
W. C. Tennant, Aust. J. Chem. 1974, 27, 2075.
84 P. G. Rasmussen, K. M. Beem, E. J. Hornyak, J. Chem.
Phys. 1969, 50, 3647.
85 D. P. Kessissoglou, X. Li, W. M. Butler, V. L. Pecoraro,
Inorg. Chem. 1987, 26, 2487.
86 O. Kotova, S. Semenov, S. Eliseeva, S. Troyanov, K.
Lyssenko, N. Kuzmina, Eur. J. Inorg. Chem. 2009, 3467.
87 S. Basak, S. Sen, S. Banerjee, S. Mitra, G. Rosair, M. T. G.
Rodriguez, Polyhedron 2007, 26, 5104.
88 J. He, Y.-G. Yin, X.-C. Huang, D. Li, Inorg. Chem.
Commun. 2006, 9, 205.
89 A. Majumder, G. M. Rosair, A. Mallick, N. Chattopadhyay,
S. Mitra, Polyhedron 2006, 25, 1753.
90 S. Das, P. K. Bharadwaj, Cryst. Growth Des. 2006, 6, 187.
91 P. S. Zhao, H. Y. Wang, J. Song, L. D. Lu, Struct. Chem.
2010, 21, 977.
2
5
2
5
3
5
4
5
5
5
6
5
7
5
8
5
9
6
0
1
6
1
92 K. Dhara, S. Karan, J. Ratha, P. Roy, G. Chandra, M.
Manassero, B. Mallik, P. Banerjee, Chem.®Asian J. 2007, 2, 1091.
93 D. Sadhukhan, A. Ray, G. Rosair, L. Charbonnière, S.
Mitra, Bull. Chem. Soc. Jpn. 2011, 84, 211.
94 L. Rodríguez-Santiago, M. Sodupe, A. Oliva, J. Bertran,
J. Am. Chem. Soc. 1999, 121, 8882.
4
6
2
K. Drabent, J. A. Wolny, M. F. Rudolf, P. J. Chmielewski,
Polyhedron 1992, 11, 271.
J. Faus, M. Julve, F. Lloret, M. C. Muñoz, Inorg. Chem.
993, 32, 2013.
B. Ramdhanie, J. Telser, A. Caneschi, L. N. Zakharov,
6
3
1
95 S. Mitra, N. Tamai, Chem. Phys. Lett. 1998, 282, 391.
6
4