Pyridone derivatives carrying radical moieties: Hydrogen-bonded structures, magnetic properties, and metal coordination

Article abstract of DOI:10.1016/j.poly.2012.07.056

Pyridone derivatives carrying radical moieties were prepared, namely a nitronyl nitroxide derivative 5-(4′,4′,5′,5′- tetramethylimidazoline-3′-oxide-1′-oxyl)-2(1H)-pyridone (1) and a verdazyl derivative 1,5-dimethyl-3-[2(1H)-pyridone]-6-oxoverdazyl (2). In the solid state, 1 and 2 form, via N-H?O intermolecular hydrogen bonds between the pyridone moieties, a zigzag one-dimensional chain structure and a cyclic dimer structure, respectively. These compounds exhibit antiferromagnetic intermolecular interactions. Mononuclear metal complexes [M(hfac) ₂(1)₂] (M = Cu^II, Mn^II; hfac = bis(hexafluoroacetylacetonate)) were prepared in which trans-[M(hfac) ₂] are coordinated with the carbonyl oxygen of the pyridone ligands. Cyclic hydrogen bonds between the mononuclear units result in the formation of one-dimensional chains. Small antiferromagnetic (for Cu^II) and ferromagnetic (for Mn^II) exchange interactions between the metal ion and the ligands were observed.

Full text of DOI:10.1016/j.poly.2012.07.056

Polyhedron 52 (2013) 755–760
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Pyridone derivatives carrying radical moieties: Hydrogen-bonded structures,
magnetic properties, and metal coordination
Mikio Ueda a,1, Tomoyuki Mochida a,b, , Hatsumi Mori c
⇑
a
Department of Chemistry, Faculty of Science, Toho University, Miyama, Funabashi, Chiba 274-8510, Japan
Department of Chemistry, Graduate School of Science, Kobe University, Rokkodai, Nada, Hyogo 657-8501, Japan
Institute for Solid State Physics, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 27 July 2012
Pyridone derivatives carrying radical moieties were prepared, namely a nitronyl nitroxide derivative
0
0
0
0
0
0
5-(4 ,4 ,5 ,5 -tetramethylimidazoline-3 -oxide-1 -oxyl)-2(1H)-pyridone (1) and a verdazyl derivative
1
,5-dimethyl-3-[2(1H)-pyridone]-6-oxoverdazyl (2). In the solid state, 1 and 2 form, via N–Hꢀ ꢀ ꢀO inter-
Dedicated to Alfred Werner on the 100th
Anniversary of his Nobel Prize in Chemistry
in 1913.
molecular hydrogen bonds between the pyridone moieties, a zigzag one-dimensional chain structure
and a cyclic dimer structure, respectively. These compounds exhibit antiferromagnetic intermolecular
interactions. Mononuclear metal complexes [M(hfac)
acetonate)) were prepared in which trans-[M(hfac) ] are coordinated with the carbonyl oxygen of the
pyridone ligands. Cyclic hydrogen bonds between the mononuclear units result in the formation of
one-dimensional chains. Small antiferromagnetic (for Cu ) and ferromagnetic (for Mn ) exchange inter-
actions between the metal ion and the ligands were observed.
Ó 2012 Elsevier Ltd. All rights reserved.
II
II
2 2
(1) ] (M = Cu , Mn ; hfac = bis(hexafluoroacetyl-
Keywords:
Pyridone
2
II
II
Nitronyl nitroxide
Verdazyl
Hydrogen bond
Metal complexes
Magnetic properties
Crystal structures
1
. Introduction
Pyridone derivatives are versatile molecules in supermolecular
extensively investigated [5,8]. We have also reported on several
metal complexes with these radical ligands [9]. Based on the fea-
tures of pyridones mentioned above, we were intrigued by the
use of pyridone derivatives for the construction of hydrogen-
bonded and metal-coordinated magnetic assemblies [10]. Several
organic radicals carrying hydrogen-bonding sites have been re-
ported to date [11]. In this study, we investigated the structures
and magnetic properties of pyridone-substituted nitronyl nitroxide
chemistry and their hydrogen-bonded aggregation patterns have
attracted attention [1]. For example, 2(1H)-pyridones produce
hydrogen-bonded structures such as cyclic dimers, one-dimen-
sional chains, and three-dimensional assemblies (Fig. 1). Pyridone
derivatives can assume keto and enol tautomeric forms as well as
the deprotonated form (Fig. 2). Since the establishment for the basis
of coordination chemistry by Werner [2], varying the ligand compo-
nents and their coordination modes has been the main strategy to
explore novel structures and functionalities of coordination com-
pounds. Thanks to their varied coordination modes, pyridone deriv-
atives act as highly versatile ligands that have produced a number
of metal cluster complexes [3]. In particular, the use of such ligands
has led to the understanding of metal–metal multiple bonds [3a]
and to the production of single-molecule magnets [3b,4].
0
0
0
0
0
and verdazyl radicals, 5-(4 ,4 ,5 ,5 -tetramethylimidazoline-3 -
0
oxide-1 -oxyl)-2(1H)-pyridone (1) and 1,5-dimethyl-3-[2(1H)-
pyridone]-6-oxoverdazyl (2) (Fig. 3), with the structure of 1 having
been briefly mentioned in a conference proceeding [12]. In this
paper, we also report the structures and properties of mononuclear
II
II
metal complexes [M(hfac)
oroacetylactonate)). We previously reported the structures and
magnetic properties of dinuclear copper complex and
2 2
(1) ] (M = Cu , Mn ; hfac = bis(hexaflu-
a
a
mononuclear palladium complex with 1 [9b], which have different
Magnetism of molecular compounds has attracted continued
interest over the last few decades [5]. Stable organic radicals, such
as nitronyl nitroxides [6] and verdazyls [7], have proven to be use-
ful building blocks for molecular magnets, and the magnetic prop-
erties of metal complexes with such radical ligands have been
coordination modes from the present complexes.
2
. Results and discussion
2.1. Preparation
⇑
Corresponding author. Tel./fax: +81 78 803 5679.
E-mail address: tmochida@platinum.kobe-u.ac.jp (T. Mochida).
Present address: Wayo Konodai Girls’ High School, Ichikawa, Chiba, Japan.
Compounds 1 and 2 were prepared from the corresponding
aldehyde precursors according to standard procedures [6,7]. The
1
0
277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.07.056

7
56
M. Ueda et al. / Polyhedron 52 (2013) 755–760
Fig. 1. Hydrogen-bonded structures of pyridone in the solid state: (a) cyclic dimer
and (b) one-dimensional chain.
Fig. 2. The keto, enol, and deprotonated forms of 2(1H)-pyridone.
Fig. 3. Structural formulae of (a) 1 and (b) 2.
II
II
reaction of 1 and [M(hfac)
2
] (M = Cu , Mn ) in methanol afforded
(1) ]. No crystalline metal
mononuclear metal complexes [M(hfac)
2
2
Fig. 4. Molecular arrangement of 1 in the solid state. (a) One-dimensional
complexes were obtained from 2, partly because the radical mole-
cule was less stable. In the IR spectra, the C=O stretching bands of
hydrogen-bonded structure. Dashed lines represent hydrogen bonds. (b) Overlap-
ping mode within the molecular stack. Dashed lines indicate the shortest
intermolecular N–Oꢀ ꢀ ꢀO–N distances. Hydrogen atoms have been omitted, except
for the NH hydrogens in (a).
1
, 2, and [M(hfac)
2
(1)
2
] in the solid state were observed at
ꢁ1
ꢁ1
ꢁ1
1
667 cm , 1653 cm , and 1646 cm , respectively. These are
ꢁ1
comparable to that in 2-pyridone (1650 cm ), indicating that
the keto form predominates in the crystals, as is confirmed by crys-
tallography discussed in the following sections.
2.2. Crystal structure and magnetic property of 1
1
Compound 1 crystallized in the monoclinic space group P2 /a.
The nitronyl nitroxide moiety and the pyridone ring in the mole-
cule are twisted from planar by about 22°. The molecules form a
zigzag chain structure via hydrogen bonds between the pyridone
moieties, as shown in Fig. 4a. The hydrogen bond distance (Nꢀ ꢀ ꢀO
distance: 2.680(4) Å) is significantly shorter than those observed
in other pyridone derivatives [1,13]. Further, the hydrogen-bonded
chains stack along the a-axis, and the molecules are weakly dimer-
ized with an intermolecular N–Oꢀ ꢀ ꢀO–N distance of 3.763(4) Å. The
dimeric molecular arrangement is shown in Fig. 4b.
The temperature dependence of the magnetic susceptibility of 1
is shown in the form of a
v
T-T plot (Fig. 5). The
v
T value at 300 K
Fig. 5. Temperature dependence of the magnetic susceptibilities of 1 and 2, plotted
in the form of
vT vs. T.
corresponds to the value of S = 1/2 non-interacting spins
ꢁ1
(
0.375 emu K mol ). With decreasing temperature, the vT value
shows a decrease from temperatures of about 50 K and below. Con-
sidering the dimeric molecular arrangement, the magnetic data
were analyzed on the basis of a singlet–triplet model using the
parameters of J/k
the intradimer interaction and h is the mean-field intermolecular
B
= ꢁ6.23 K and h = ꢁ0.61 K obtained, where J is
Bleaney–Bowers equation (H = ꢁ2J S
1
ꢀS
2
) [14], with the best-fit
interaction.

M. Ueda et al. / Polyhedron 52 (2013) 755–760
757
2.3. Crystal structure and magnetic property of 2
Compound 2 crystallized in the monoclinic space group C2/c,
with the verdazyl and pyridone rings in the molecule twisted from
planar by about 15°. In the crystal, 2 forms a cyclic hydrogen-
bonded dimer, as shown in Fig. 6a. The hydrogen-bond distance
(
Nꢀ ꢀ ꢀO distance: 2.751(4) Å) is typical of pyridone derivatives.
The packing diagram is shown in Fig. 6b. The radical molecules
assemble into head-to-tail arrangements and form a stair-like
structure along the a-axis, while, as shown by dashed lines in
Fig. 6b, there is dimer overlap between the verdazyl rings. The cen-
troid–centroid distance between the verdazyl rings is 3.39 Å.
The temperature dependence of the magnetic susceptibility of 2
ꢁ1
is shown in Fig. 5. The
vT value at 300 K (0.365 emu K mol ) is
close to the value of S = 1/2 non-interacting spins
ꢁ
1
(
0.375 emu K mol ). With decreasing temperature, the vT values
first steadily decreased and then decreased rapidly at temperatures
below around 130 K. This strong antiferromagnetic interaction is
ascribable to the dimerization of the verdazyl ring. Similar to the
case of 1, the magnetic data were analyzed on the basis of the sin-
glet–triplet model, which yielded the intradimer exchange cou-
pling of J ꢂ ꢁ100 K. The concentration of the Curie impurities
was estimated to be 1.5%.
Fig. 7. Molecular structure of [Cu(hfac)
represent hydrogen bonds. The trifluoromethyl groups have been omitted for
clarity. Hydrogen atoms, except for the NH hydrogens, have been omitted.
2
(1)
2
]
in the solid state. Dashed lines
manganese complexes are 2.897(3) Å and 2.936(3) Å, respectively.
II
In the Cu complex, the bond lengths around the metal center are
Cu–Opyridone = 2.310(2) Å and Cu–Ohfac = 1.958(2) Å. The axial bond
length is longer owing to Jahn–Teller distortion. In the Mn com-
plex, the bond lengths are Mn–Opyridone = 2.197(2) Å, and Mn–Ohfac
II
2 2
2.4. Structures and magnetic properties of [M(hfac) (1) ]
=
2.130(2) Å and 2.132(3) Å. The trifluoromethyl groups in the hfac
] (M = CuII and Mn ) crystallized in
II
Isomorphous [M(hfac)
2
(1)
2
ligands are disordered over two sites in both complexes, with an
occupancy of about 6:4.
ꢀ
II
the P1 space group. The crystal structure of the Cu complex is
shown in Fig. 7. The nitronyl nitroxide moiety and the pyridone ring
in the radical ligands are twisted by about 20° from planar. The
complexes form centrosymmetric trinuclear units in which two
radical molecules are coordinated to the trans positions of the metal
ion by the carbonyl oxygen of the pyridone moiety. Furthermore,
the trinuclear units interact via dimeric intermolecular hydrogen
bonds between the pyridone moieties, forming one-dimensional
chain structures. More particularly, the carbonyl oxygen in the li-
gand interacts both with the metal ion and the NH hydrogen. The
hydrogen bond distances (Nꢀ ꢀ ꢀO distances) for the copper and
II
The temperature dependence of the
v
T values for the Cu and
II
II
Mn complexes is shown in Fig. 8. In the Cu complex, the
at 300 K was 1.09 emu K mol , which corresponds to three iso-
lated S = 1/2 spins (1.125 emu K mol ). With decreasing tempera-
ture, the
decreased. The data were analyzed on the basis of a linear three-
spin model (H = ꢁ2J S ꢀS + S ꢀS ) [15]. The exchange coupling be-
tween the metal center and the radical was determined to be J/
v
T value
ꢁ1
ꢁ1
vT value remained nearly constant down to 10 K and then
1
M
M
2
II
k
B
= ꢁ0.35 K (g = 2.00). In the Mn complex, the
vT value at 300 K
ꢁ1
was 5.00 emu K mol , which is close to the theoretical value for
uncorrelated two S = 1/2 spin and an S = 5/2 for octahedrally coor-
II
ꢁ1
dinated Mn (5.12 emu K mol ). With decreasing temperature,
the T value remained constant down to 60 K and then gradually
v
Fig. 6. Molecular arrangement of 2 in the solid state. (a) The cyclic dimer unit.
Dashed lines represent hydrogen bonds. (b) Packing diagram viewed along the b-
axis. Dashed lines represent the dimer formation between radical moieties.
Fig. 8. Temperature dependence of the magnetic susceptibilities of (a) [Cu(h-
fac) (1) ] and (b) [Mn(hfac) (1) ], represented in the form of T vs. T plots.
2
2
2
2
v

7
58
M. Ueda et al. / Polyhedron 52 (2013) 755–760
assumed the enol form and the deprotonated form in the previ-
ously reported complexes [9b]. Thus, a series of open-shell molec-
ular assemblies were prepared that reflect the variety of hydrogen-
bonding modes and coordination modes obtainable with pyridone
ligands.
4
. Experimental
.1. General
,3-Bis(hydroxyamino)-2,3-dimethylbutane [16] and carbonic
4
2
acid bis(1-methylhydrazide) [17] were prepared according to liter-
1
ature methods. Other chemicals were commercially available. H-
NMR spectra were measured on a JEOL ECP400 spectrometer. Infra-
red spectra were recorded on a JASCO FT-IR 230 spectrometer
using KBr pellets. Elemental analyses were performed using a
Yanagimoto MT-3 CHN analyzer. ESR spectra were measured on
a JEOL JES-TE100 spectrometer (X-band microwave unit). The mag-
netic susceptibilities were measured using a Quantum Design
MPMS-2 SQUID susceptometer in the temperature range 2–300 K
under a magnetic field of 1 T.
Fig. 9. Schematic illustration of the molecular orbital arrangement relevant to the
magnetic exchange interactions in (a) [Cu(hfac) (1) ] and (b) [Mn(hfac) (1) ].
2
2
2
2
increased, reaching a maximum at 6 K and then rapidly decreased.
Fitting of the data on the basis of the linear three-spin model gave
J/k = +0.78 K (g = 2.00), indicating the presence of small ferromag-
B
netic coupling in the mononuclear unit.
The magnetic interactions were interpreted based on the con-
sideration of the magnetic orbitals. In the Cu complex (Fig. 9a),
the orthogonality of the singly occupied magnetic orbital dx2–y2
and the 2p orbital of the carbonyl oxygen may be responsible for
the antiferromagnetic interaction when one considers the spin
4
4
.2. Preparation of 1
II
.2.1. 2-Benzyloxy-5-bromopyridine
Benzyl alcohol (1.68 g, 15.5 mmol) was added to a suspension of
sodium hydride (0.61 g, 15.2 mmol, 60% dispersion in oil) in DMF
6 mL) cooled with an ice bath. After stirring the mixture for
0 min at room temperature, a DMF solution (10 mL) of 2,5-dib-
(
3
II
polarization in the radical ligand. In the Mn complex, however,
dxz and dyz of the five magnetic orbitals overlap with the 2p orbital
romopyridine (3.08 g, 13.0 mmol) was added dropwise to the solu-
tion. After stirring for 5 h, acetic acid (3 mL) was added dropwise to
the solution at 0 °C and stirred for 30 min. The solution was then
diluted with toluene (30 mL), washed with water (20 mL), before
of the carbonyl oxygen of 1 (Fig. 9b), which may thus be responsi-
ble for the ferromagnetic interaction. The small J values for the
present complexes are ascribed to very small spin densities on
the pyridone rings. Much stronger exchange couplings are reported
for ligands with aminoxyl radicals owing to the more extensive
spin delocalization onto the ligating sites: the metal–ligand mag-
5
3
% aqueous NaHCO (80 mL) was added. The organic layer was
dried over magnesium sulfate, filtered, and the solvent evaporated
under a reduced pressure. The crude product was purified by col-
netic interactions in mononuclear complexes of [M(hfac)
2
] with
umn chromatography (silica gel, eluent: CHCl
benzyloxy-5-bromopyridine was obtained as a colorless solid
3.41 g, yield 99%). Recorded analytical data were in accordance
with literature values [18].
3
:hexane = 1:2). 2-
bis{4-(N-tert-butyl-N-oxyamino)pyridine} are J/k = +60.4 K for
B
II
II
M = Cu and ꢁ12.4 K for M = Mn [15a].
(
We reported previously that 1 assumes the deprotonated form
in the dinuclear Cu complex and the enol form in the mononu-
clear Pd complex, coordinating via the nitrogen atom [9b]. The
II
II
4.2.2. 6-Benzyloxypyridine-3-carbaldehyde
2
formation of the keto form in the [M(hfac) ] complexes has further
n-Butyl lithium (9.0 mL, 1.59 M solution in n-hexane) was
demonstrated the variability of the coordination modes of the li-
gand. In all of the complexes studied, magnetic interactions within
the units are weak. In terms of spin delocalization, 2 is more
advantageous than 1, but the ligand produced no metal complexes.
In these complexes, the radical moieties have additional coordina-
tion ability, which may further lead to higher dimensional coordi-
nation structures when other additional metal ions are used.
added to a THF solution (20 mL) of 2-benzyloxy-5-bromopyridine
(
3.40 g, 12.9 mmol) at ꢁ78 °C. After stirring for 30 min, anhydrous
DMF (1.25 mL, 16.3 mmol) was added dropwise to this solution.
After stirring for 1 h at ꢁ78 °C, water (3.0 mL) was added and the
solution left at room temperature overnight. The reaction product
was extracted by dichloromethane, washed with water, and dried
over magnesium sulfate. The crude product was purified by col-
3
umn chromatography (silica gel, eluent: CHCl :hexane = 1:1). After
3
. Conclusion
evaporation of the solvent, a yellow oil of 6-benzyloxypyridine-3-
carbaldehyde was obtained (2.66 g, yield 97%). H-NMR (400 MHz,
1
Pyridone-substituted nitronyl nitroxide and verdazyl radicals
3
CDCl ) d 9.97 (1H, s), 8.65 (1H, s), 8.08 (1H, d, J = 10.7 Hz), 7.47–
were prepared and their structures and magnetic properties inves-
tigated. These radicals exhibited one-dimensional chain structures
and dimeric structures via hydrogen bonds. The [M(hfac) ] com-
2
plexes (M = Cu, Mn) with the nitroxide radical ligand produced
mononuclear complexes, which were further hydrogen bonded to
form chain structures in the crystals. The mononuclear units, re-
garded as linear three-spin systems, exhibited very weak magnetic
couplings between the metal center and the radical ligands. The
verdazyl ligand, for which larger spin delocalization is expected,
produced no metal complexes. The pyridone moieties in the
7.34 (5H, m), 6.90 (1H, d, J = 8.8 Hz), 5.49 (2H, s).
Palladium carbon (0.18 g, 10 wt.% on activated carbon) was
added to a methanol solution (30 mL) of thus obtained 6-benzyl-
oxypyridine-3-carbaldehyde (2.66 g, 12.5 mmol). Under hydrogen
atmosphere, the suspension was stirred at room temperature over-
night. Water (30 mL) was then added to the reaction mixture, fil-
tered, and the solvent evaporated under a reduced pressure.
Recrystallization from chloroform/hexane gave a white powder
of 6-benzyloxypyridine-3-carbaldehyde (0.88 g, yield 58%). 1H-
NMR (400 MHz, DMSO) d 9.59 (1H, s), 8.23 (1H, s), 7.79 (1H, d,
J = 9.7 Hz), 6.45 (1H, d, J = 9.3 Hz).
[
2
M(hfac) ] complexes assumed the keto form, whereas the ligand

M. Ueda et al. / Polyhedron 52 (2013) 755–760
759
0
0
0
0
0
0
4
.2.3. 5-(4 ,4 ,5 ,5 -Tetramethylimidazoline-3 -oxide-1 -oxyl)-2(1H)-
The solvent was removed by evaporation, to which diethylether was
added and the solution stored in a refrigerator for several days. The
product was filtered, washed with diethyl ether, and then dried to
pyridone (1)
A
methanol solution (40 mL) of 6-benzyloxypyridine-3-
carbaldehyde (475 mg, 3.86 mmol), 2,3-bis(hydroxyamino)-2,
max
produce dark red crystals (104 mg, yield 33%). FT-IR (KBr): m /
ꢁ1
3
-dimethylbutane (625 mg, 4.22 mmol), and 2,3-bis(hydroxyami-
cm 3442w, 1682s, 1653s 1628 m, 1442s; kmax/nm (DMF) 273,
320sh, 338sh, 394, 417, 529; ESR (in DMF): a = 0.56 mT (4 N) at
g = 2.005; Anal. Calc. for C : C, 49.09; H, 4.58; N, 31.80.
Found: C, 48.89; H, 4.49; N, 31.92%.
no)-2,3-dimethylbutane sulfonate (40 mg, 0.16 mmol) was stirred
at room temperature. After stirring for 4 d, the solvent was re-
moved by evaporation. The crude solid was suspended in dichloro-
N
9
10 5 2
H N O
methane (40 mL), to which an aqueous solution (10 mL) of NaIO
4
(
970 mg, 4.53 mmol) was added slowly. After stirring for 10 min,
2
4.4. Preparation of [M(hfac) ] complexes (M = Cu, Mn) with 1
4
the organic layer was separated, dried with MgSO , and evaporated
under a reduced pressure. The crude product was purified by col-
umn chromatography (silica gel, eluent: acetone:diethyl
ether = 1:2). The product was recrystallized from dichlorometh-
ane/hexane to give blue crystals of 1 (512 mg, yield 53%). ESR (in
[Cu(hfac)
(1 mL) of 1 (2 mg, 0.008 mmol) was added to a methanol solution
(1 mL) of bis(hexafluoroacetylacetonate)copper(II) (19 mg,
0.004 mmol). After standing the solution at room temperature for
several days, deep blue needle crystals of [Cu(hfac) (1) ] were ob-
/cm 3132(NH), 1646(C=O); Anal. Calc. for
12Cu: C, 41.75; H, 3.50; N, 8.59. Found: C, 41.72; H,
.54; N, 8.63%. [Mn(hfac) (1) ], which was prepared by the same
2
(1) ] was prepared as follows. A methanol solution
2
ꢁ1
CH
1
1
2
Cl
667(C=O); Anal. Calc. for C12
6.79. Found: C, 57.62; H, 6.42; N, 16.63%.
2
): a
N
= 0.78 mT (2 N) at g = 2.008; FT-IR (KBr):
m
/cm
2
2
ꢁ1
H
16
O
3
N
3
: C, 57.59; H, 6.44; N,
tained. FT-IR (KBr): m
H O N F
34 34 10 6
C
3
2
2
ꢁ
1
4
4
.3. Preparation of 2
method, gave deep blue needle crystals. IR (KBr):
m/cm
3
132(NH), 1646(C=O); Anal. Calc. for 12Mn: C,
34 34 10 6
C H O N F
.3.1. 1,5-Dimethyl-3-[2(1H)-pyridone]-1,2,4,5-tetrazane 6-oxide
42.12; H, 3.53; N, 8.67. Found: C, 41.85; H, 3.55; N, 8.59%.
A
methanol solution (15 mL) of 5-formyl-2(1H)-pyridone
(
215 mg, 1.7 mmol) was added dropwise to a warm solution of car-
4.5. X-ray crystal structure analyses
bonic acid bis(1-methylhydrazide) (254 mg, 2.2 mmol) in metha-
nol (35 mL). After the solution was refluxed for 24 h, the solvent
was evaporated under a reduced pressure, before the residue was
washed with chloroform and air dried. Pale yellow powder
The X-ray data for 1 and [Cu(hfac)
aku AFC-5S four circle diffractometer, and those for 2 and
[Mn(hfac) (1) ] on a Rigaku Mercury CCD diffractometer, using
MoK radiation. Crystallographic parameters are listed in Table 1.
The structures were solved by direct methods and refined using
the teXsan software package [19] for 2 and SHELX-97 [20] for the
other compounds. The hydrogen atoms were placed at idealized
positions and allowed to ride on the relevant heavier atoms. OR-
TEP-3 [21] was used to generate the molecular graphics.
2 2
(1) ] were collected on a Rig-
2
2
ꢁ1
(
1
372 mg, yield 95%). FT-IR (KBr):
432s, 1390s; H-NMR (400 MHz DMSO): d 11.56 (br, s, 1H), 7.52
m
/cm
3242s, 1664s, 1589s,
a
1
(
(
3
dd, 1H), 7.33 (s, 1H), 6.32 (d, 1H), 5.67 (d, 2H), 4.72 (t, 1H), 2.92
s, 6H) ppm; Anal. Calc. for C : C, 48.42; H, 5.87; N,
1.37. Found: C, 48.19; H, 5.92; N, 31.06%.
9
13 5 2
H N O
4.3.2. 1,5-Dimethyl-3-[2(1H)-pyridone]-6-oxoverdazyl (2)
A solution of NaIO (334 mg, 1.6 mmol) in water (20 mL) was
4
Acknowledgments
added to a methanol solution (20 mL) of 1,5-dimethyl-3-[2(1H)-
pyridone]-1,2,4,5-tetrazane 6-oxide (315 mg, 1.4 mmol) prepared
as above. The solution immediately turned deep red, and after
We sincerely thank Dr. Ulrich Schatzschneider and Prof. Eva
Rentschler (Max-Planck-Institut für Strahlenchemie, Germany)
for theoretical estimation of the magnetic properties in the early
3
0 min of stirring, the product was extracted with dichloromethane.
Table 1
Crystallographic parameters.
1
2
[Cu(hfac)
2
(1)
2
]
2 2
[Mn(hfac) (1) ]
Empirical formula
Formula weight
Crystal system
a (Å)
b (Å)
c (Å)
C
12
H
16
N
3
O
3
C
9
H
10
N
5
O
2
C
34
H
34CuF12
N
6
O
10
34 6 10
C H34MnF12N O
969.61
triclinic
7.4549(4)
11.4901(2)
13.7931(8)
69.381(18)
81.77(2)
77.39(2)
250.28
220.21
978.21
triclinic
monoclinic
8.9193(14)
19.093(3)
monoclinic
18.794(13)
7.637(5)
7.588(4)
11.127(3)
13.547(3)
71.603(16)
82.41(3)
76.86(3)
7.6035(12)
16.993(12)
a
(°)
b (°)
(°)
104.919(12)
128.259(9)
c
3
V (Å )
1251.2(3)
P2
1915.2(21)
C2/c
1054.7(6)
P1ꢀ
1076.28(17)
P1ꢀ
Space group
1
/c
Z value
4
8
1
1
D
calc
1.329
532
3264
2868
169
296
0.0569, 0.1503
0.1936, 0.2078
0.944
1.527
920
8759
2352
155
1.540
497
5082
4832
342
296
0.0403, 0.1137
0.0707, 0.1265
1.059
1.496
493
7913
4320
341
293
0.0644, 0.1691
0.0827, 0.1846
1.179
F(000)
No. of reflections
No. of observations
Parameters
T (K)
80
a
, wR b
c
R
R
1
2
(I > 2
(all data)
r
(I))
0.0790, –
a
b
c
1
, wR
2
– , 0.1910
Goodness-of-fit
1.036
a
b
c
R
wR
1
=
R
= [
||F
R
o
| ꢁ |F
c
||/
ꢁ F
R
|F
) /
o
|.
R
2
2 2
2)2]1/2.
w(F
o
2
w(F
o
c
Data not available.

7
60
M. Ueda et al. / Polyhedron 52 (2013) 755–760
stage of this study. We thank Yusuke Funasako (Kobe University)
for crystallographic analysis, Dr. Hideaki Suzuki (Tokyo University)
for his help with SQUID measurements, and Mr. Masaru Nakama
[6] (a) H. Sakurai, A. Izuoka, T. Sugawara, J. Am. Chem. Soc. 122 (2000) 9723;
b) J. Cirujeda, M. Mas, E. Molins, F. Lanfranc de Panthou, J. Laugier, J.G. Park, C.
(
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7] (a) K. Mukai, M. Nuwa, K. Suzuki, S. Nagaoka, N. Achiwa, J.B. Jamali, J. Phys.
Chem. B 102 (1998) 782;
[
(
Crayonsoft, Inc.) for providing a Web-based database system. This
(
(
b) F.A. Neugebauer, H. Fischer, R. Siegel, Chem. Ber. 121 (1988) 815;
c) R.G. Hicks, M.T. Lemaire, L. Öhrström, J.F. Richardson, L.K. Thompson, Z. Xu,
work was supported financially by KAKENHI (No. 23110719) and
was carried out under the Visiting Researcher’s Program of the
Institute for Solid State Physics, the University of Tokyo.
J. Am. Chem. Soc. 123 (2001) 7154.
[8] (a) T.M. Barclay, R.G. Hicks, M.T. Lemaire, L.K. Thompson, Z. Xu, Chem.
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Appendix A. Supplementary data
Trans. (2000) 2019.
[
9] (a) M. Ueda, T. Mochida, M. Itou, N. Asanagi, H. Mori, Inorg. Chim. Acta 348C
(
(
2
2003) 123;
CCDC 882833–882836 contains the supplementary crystallo-
graphic data for 1, 2, [Cu(hfac) (1) ], and [Mn(hfac) (1) ]. These
2 2 2 2
b) M. Ueda, M. Itou, K. Okazawa, T. Mochida, H. Mori, Polyhedron 24 (2005)
189.
data can be obtained free of charge via http://www.ccdc.cam.a-
c.uk/conts/retrieving.html, or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44-
[10] T. Mochida, M. Ueda, C. Aoki, H. Mori, Inorg. Chim. Acta 335 (2002) 151.
[
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