Dinuclear Mn(II), Ni(II), and Zn(II) complexes bridged by Bis(p-nitrophenyl) phosphate ion: Relevance to bimetallic phosphodiesterase

Article abstract of DOI:10.1246/bcsj.78.1072

2,6-Bis[N,N-di(2-pyridylmethyl)aminomethyl]-4-methylphenol (Hbpmp) has afforded dinuclear Mn(II), Ni(II), and Zn(II) complexes with two bis(p-nitrophenyl) phosphate (BNP^-) ions, [M₂(bpmp)(bnp) ₂]ClO₄ (M = Mn (1), Ni (2), Zn (3)). The structure of 1 · 2MeCN has been determined by the single crystal X-ray method. It has a dinuclear core structure bridged by the phenolic oxygen atom of bpmp^- and two BNP^- ions. Each metal center has a pseudo octahedral geometry with an average Mn-to-donor bond distance of 2.207 A. Physicochemical properties of 1-3 are studied and their relevance to biological phosphodiesterase is discussed.

Full text of DOI:10.1246/bcsj.78.1072

1072 Bull. Chem. Soc. Jpn., 78, 1072–1076 (2005)
ꢀ 2005 The Chemical Society of Japan
Dinuclear Mn(II), Ni(II), and Zn(II) Complexes Bridged
by Bis(p-nitrophenyl) Phosphate Ion: Relevance to
Bimetallic Phosphodiesterase
Hitomi Shiraishi, Reiko Jikido, Kanako Matsufuji, Tatsuaki Nakanishi, Takuya Shiga,
y
ꢀ
¯
Masaaki Ohba, Ken Sakai, Hiroshi Kitagawa, and Hisashi Okawa
Department of Chemistry, Faculty of Science, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581
Received December 24, 2004; E-mail: okawascc@mbox.nc.kyushu-u.ac.jp
2,6-Bis[N,N-di(2-pyridylmethyl)aminomethyl]-4-methylphenol (Hbpmp) has afforded dinuclear Mn(II), Ni(II), and
Zn(II) complexes with two bis(p-nitrophenyl) phosphate (BNPꢁ) ions, [M2(bpmp)(bnp)2]ClO4 (M ¼ Mn (1), Ni (2), Zn
(3)). The structure of 1 2MeCN has been determined by the single crystal X-ray method. It has a dinuclear core structure
bridged by the phenolic oxygen atom of bpmpꢁ and two BNPꢁ ions. Each metal center has a pseudo octahedral geom-
ꢂ
ꢀ
etry with an average Mn-to-donor bond distance of 2.207 A. Physicochemical properties of 1–3 are studied and their
relevance to biological phosphodiesterase is discussed.
Bimetallic cores exist at active sites of many metalloen-
zymes and play an essential role in biological systems.1 Dinu-
Me
clear or trinuclear Zn cores are found at the active sites of
phosphoesterases.2–5 It is known that phosphotriesterases2
use a pair of Zn ions to facilitate the concerted binding of a
N
N
OH
N
N
substrate at one Zn center and the nucleophilic attack of hy-
droxide or activated water provided at the adjacent Zn center.
Phosphodiesterases such as phospholipase C3 and P1 nuclease4
require an additional Zn ion to hydrolyze phosphodiester. It is
considered that the phosphodiesterases utilize a trinuclear Zn
core to bind a bidentate phosphodiester on a dinuclear Zn unit
and provide the nucleophile (hydroxide or activated water) on
the third Zn center. Another class of phosphodiesterases has a
dinuclear FeFe,6 FeZn,7,8 FeMn,9 or MnMn10 core instead of
trinuclear Zn core. Thus, model studies of the bimetallic phos-
phodiesterases using homo- and heterodinuclear metal com-
plexes are becoming a current subject.11–18
In order to gain an insight into the hydrolytic function
of bimetallic phosphodiesterases, phosphodiester adducts of
dinuclear metal complexes are informative.17,19–22 In this
work, phosphodiester adducts of dinuclear Mn(II), Ni(II), and
Zn(II) complexes, [M2(bpmp)(bnp)2]ClO4 (M ¼ Mn (1), Ni
(2), and Cu (3)), have been prepared, where Hbpmp is 2,6-bis-
[N,N-di(2-pyridylmethyl)aminomethyl]-4-methylphenol (Fig. 1)
and BNPꢁ is bis(p-nitrophenyl) phosphate ion. The structure
N
N
Fig. 1. Chemical structure of Hbpmp.
hydrogen and nitrogen were obtained at The Service Center of
Elemental Analysis of Kyushu University. Metal analyses were
obtained using a Shimadzu AA-680 Atomic Absorption/Flame
Emission Spectrophotometer. Infrared spectra were measured us-
ing a KBr disk on a PERKIN ELMER Spectrum BX FT-IR sys-
tem. Electronic absorption spectra in dimethyl sulfoxide (DMSO)
were recorded on a Shimadzu UV-3100PC spectrophotometer.
Magnetic susceptibilities of powdered samples were measured
on a Quantum Design MPMS XL SQUID susceptometer in the
temperature range of 2–300 K.
Preparation. Hbpmp was prepared by the literature method.23
Other chemicals were purchased from commercial sources
and used without further purification. [M2(dpmp)(bnp)2]ClO4
(M ¼ Mn (1), Ni (2), and Zn (3)) were prepared by two methods
given below.
of 1 2MeCN is determined to demonstrate a bis(ꢀ-bnp)-ꢀ-
ꢂ
Method I. A solution of M(ClO4)2 6H2O (M ¼ Mn, Ni, or Zn)
ꢂ
phenolato dinuclear structure. Physicochemical properties of
1–3 are examined and their relevance to biological phospho-
diesterase is discussed.
(1.0 mmol) in hot methanol (5 mL) was added to a solution of
Hbpmp (0.5 mmol) in hot methanol (10 mL), and the mixture
was stirred at ambient temperature for 30 minutes. A solution of
sodium bis(p-nitrophenyl) phosphate (NaBNP) (1.0 mmol) in
methanol (5 mL) was added, and the mixture was stirred for 30
minutes and allowed to stand to give [M2(dpmp)(bnp)2]ClO4 as
microcrystals.
Experimental
Physical Measurements.
Elemental analyses of carbon,
y Present address: Graduate School of Engineering, Department
of Synthetic Chemistry and Biological Chemistry, Kyoto Uni-
versity, Katsura, Nishikyo-ku, Kyoto 615-8510
Method II. A methanol solution of the bis(ꢀ-acetato) complex
of bpmpꢁ, [M2(bpmp)(AcO)2]ClO4 (M ¼ Mn,24 Ni,25 Zn26), and
NaBNP in the 1:2 molar ratio was refluxed for one hour and the
Published on the web June 6, 2005; DOI 10.1246/bcsj.78.1072

H. Shiraishi et al.
Bull. Chem. Soc. Jpn., 78, No. 6 (2005) 1073
mixture was concentrated to obtain [M2(dpmp)(bnp)2]ClO4.
[Mn2(bpmp)(bnp)2]ClO4 (1). Colorless microcrystals. Yield
by method I: 72%. Calcd for C57H49ClMn2N10O21P2: C, 48.30; H,
3.48; N, 9.88; Mn, 7.75%. Found: C, 48.23; H, 3.50; N, 9.92; Mn
7.80%. Selected IR data [ꢁ/cmꢁ1] using KBr: 1605, 1592, 1520,
1490, 1348, 1267, 1219, 1114, 1096, 913, 768, 623, 555. UV–vis
data [ꢂ/nm ("/Mꢁ1 cmꢁ1)] in DMSO: 280 (37000), 308 (39000).
[Ni2(bpmp)(bnp)2]ClO4 (2). Blue microcrystals. Yield by
method I: 81%. Calcd for C57H49ClN10O21P2Ni2: C, 48.05; H,
3.47; N, 9.83; Ni, 8.24%. Found: C, 47.98; H, 3.37; N, 9.84; Ni
8.30%. Selected IR data [ꢁ/cmꢁ1] using KBr: 1609, 1592,
1520, 1348, 1271, 1220, 1097, 905, 767, 623, 551. UV–vis data
[ꢂ/nm ("/Mꢁ1 cmꢁ1)] in DMSO: 280 (39000), 305 (41000),
597 (14), 988 (37).
Results and Discussion
Crystal Structures.
An ORTEP28 view of 1 2MeCN
ꢂ
is shown in Fig. 2 together with selected atom numberings.
Relevant bond distances and angles are summarized in
Table 2.
The asymmetric unit consists of one [Mn2(bpmp)(bnp)2]þ
cation, one perchlorate ion and two acetonitrile molecules.
The perchlorate ion and the acetonitrile molecules are free
[Zn2(bpmp)(bnp)2]ClO4 (3). Colorless microcrystals. Yield
by method I: 45%. Calcd for C57H49ClN10O21P2Zn2: C, 47.60;
H, 3.43; N, 9.74; Zn, 9.09%. Found: C, 47.48; H, 3.44; N, 9.72;
Zn, 8.61%. Selected IR data [ꢁ/cmꢁ1] using KBr: 1608, 1592,
1520, 1348, 1270, 1219, 1095, 910, 623, 553. UV–vis data [ꢂ/
nm ("/Mꢁ1 cmꢁ1)] in DMSO: 280 (38000), 305 (40000).
X-ray Crystallography. Single crystals of 1 2MeCN were
ꢂ
grown by slow recrystallization of 1 from acetonitrile. A single
crystal was mounted on a glass fiber and coated by epoxy resin.
Crystallographic measurementsꢃ were made on a Rigaku/MSC
Mercury diffractometer at ꢁ95 C with graphite monochromated
ꢀ
Mo Kꢃ radiation (ꢂ ¼ 0:71070 A). A symmetry-related absorp-
tion correction using the program ABSCOR and an empirical ab-
sorption correction based on azimuthal scans of several reflections
were applied. Pertinent crystallographic parameters are summariz-
ed in Table 1.
The structure was solved by the direct method and expanded
using the Fourier technique. Non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were included in the structure
analysis but not refined. All calculations were performed using
the teXsan crystallographic software package of Molecular Struc-
ture Corporation.27
Crystallographic data have been deposited at the CCDC, 12
Union Road, Cambridge CB2 1EZ, UK and copies can be ob-
tained on request, free of charge, by quoting the publication cita-
tion and deposition number CCDC 256446.
Fig. 2. An ORTEP view of [Mn2(bpmp)(bnp)2]ClO4
2MeCN (1 2MeCN).
ꢂ
ꢂ
Table 2. Selected Bond Distances and Angles of 1 2MeCN
ꢂ
ꢀ
Bond distances (A)
Mn(1)–O(1)
Mn(1)–O(10)
Mn(1)–N(2)
Mn(2)–O(1)
Mn(2)–O(11)
Mn(2)–N(5)
2.112(2) Mn(1)–O(2)
2.101(3) Mn(1)–N(1)
2.258(3) Mn(1)–N(3)
2.126(2) Mn(2)–O(3)
2.206(3) Mn(2)–N(4)
2.298(3) Mn(2)–N(6)
3.68
2.168(3)
2.280(3)
2.241(3)
2.134(3)
2.298(3)
2.249(3)
Table 1. Crystallographic Data of [Mn2(bpmp)(bnp)2]-
ClO4 2MeCN (1 2MeCN)
Mn(1) Mn(2)
ꢂꢂꢂ
ꢂ
ꢂ
Formula
C61H55ClMn2N12O21P2
1499.44
orthorhombic
Bond angles (degree)
O(1)–Mn(1)–O(2)
O(1)–Mn(1)–N(1)
O(1)–Mn(1)–N(3)
O(2)–Mn(1)–N(1)
O(2)–Mn(1)–N(3)
O(10)–Mn(1)–N(2)
N(1)–Mn(1)–N(2)
N(2)–Mn(1)–N(3)
O(1)–Mn(2)–O(11)
O(1)–Mn(2)–N(5)
O(3)–Mn(2)–O(11)
O(3)–Mn(2)–N(5)
O(11)–Mn(2)–N(4)
Formula weight
Crystal system
Space group
86.6(1) O(1)–Mn(1)–O(10) 101.6(1)
88.8(1) O(1)–Mn(1)–N(2) 159.0(1)
89.3(1) O(2)–Mn(1)–O(10) 100.1(1)
88.6(1) O(2)–Mn(1)–N(2) 82.4(2)
165.0(2) O(10)–Mn(1)–N(1) 166.7(1)
ꢁ
P1
ꢀ
a/A
12.3628(4)
13.2771(4)
20.5465(7)
83.208(7)
85.361(7)
76.624(5)
3253.03(18)
2
ꢀ
b/A
ꢀ
c/A
97.9(2) O(10)–Mn(1)–N(3)
73.2(1) N(1)–Mn(1)–N(3)
96.7(1) O(1)–Mn(2)–O(3)
91.0(1) O(1)–Mn(2)–N(4)
157.9(1) O(1)–Mn(2)–N(6)
94.2(2) O(3)–Mn(2)–N(4)
102.8(1) O(3)–Mn(2)–N(6)
92.3(1) O(11)–Mn(2)–N(5)
94.9(1)
76.8(1)
98.4(1)
87.2(1)
91.1(1)
171.4(1)
97.1(2)
81.2(1)
72.6(1)
92.6(2)
ꢃ/degree
ꢄ/degree
ꢅ/degree
ꢀ 3
V/A
Z value
Dcalc/g cmꢁ3
ꢀ(Mo Kꢃ)/cmꢁ1
No. reflections
R
1.531
5.65
13996
0.096
0.232
O(11)–Mn(2)–N(6) 168.1(1) N(4)–Mn(2)–N(5)
N(4)–Mn(2)–N(6) 76.2(1) N(5)–Mn(2)–N(6)
Mn(1)–O(1)–Mn(2) 119.9(1)
Rw

1074 Bull. Chem. Soc. Jpn., 78, No. 6 (2005)
Phosphodiester-Bridged Dinuclear Metal Complexes
from coordination and captured in the crystal lattice. Two
Mn ions in [Mn2(bpmp)(bnp)2]þ are bridged by the phenolic
oxygen atom of bpmpꢁ and by two BNPꢁ groups. The
6
Complex 1
5
ꢀ
Mn(1) Mn(2) interatomic separation is 3.68 A and the
ꢂꢂꢂ
4
3
Mn(1)–O(1)–Mn(2) angle is 119.9(1)ꢃ. Each Mn has a six-co-
ordinate geometry with an average Mn-to-donor bond distance
Complex 2
ꢀ
ꢀ
of 2.195 A for Mn(1) and 2.218 A for Mn(2). Two pyridine
residues on each articular nitrogen atom (N(1) and N(4)) are
not equivalent in the crystal: one pyridine nitrogen (N(2) or
N(5)) is situated trans to the phenolic oxygen O(1), whereas
the other pyridine nitrogen (N(3) or N(6)) is situated cis to
O(1). When the plane defined by O(1), N(1), and N(2)
(O(1), N(4), and N(5)) is assumed to be the equatorial base,
each BNPꢁ ion makes a bond to an equatorial site of one
Mn and to an apical site of another Mn. As the result, the com-
plex molecule shows a twist with respect to the C(5)–O(1)
bond of the phenol group. The twist angle between the
phenolic ring and the least-squares plane defined by Mn(1),
O(1), and Mn(2) is 51.3(1)ꢃ. The P(1)–O(2), P(1)–O(3),
P(2)–O(10), and P(2)–O(11) bond lengths fall in the range of
2
1
0
0
100
200
300
T / K
Fig. 3. Temperature-dependence of magnetic moment of
[Mn2(bpmp)(bnp)2]ClO4 (1) (top) and [Ni2(bpmp)(bnp)2]-
ClO4 (2) (bottom).
ꢆA ¼ fNg2ꢄ2=kTg ꢄ ½expðꢁ28J=kTÞ
þ 5 expðꢁ24J=kTÞ þ 14 expðꢁ18J=kTÞ
þ 30 expðꢁ10J=kTÞ þ 55ꢅ=½expðꢁ30J=kTÞ
þ 3 expðꢁ28J=kTÞ þ 5 expðꢁ24J=kTÞ
þ 7 expðꢁ18J=kTÞ þ 9 expðꢁ10J=kTÞ þ 11ꢅ: ð1Þ
ꢀ
1.473(3)–1.488(3) A.
It is of value to compare the structure of 1 2MeCN with the
ꢂ
structure of the analogous bis(ꢀ-acetato) complex, [Mn2-
(bpmp)(AcO)2]ClO4.29 This complex has the Mn(1) Mn(2)
ꢂꢂꢂ
ꢀ
separation of 3.412 A and the Mn(1)–O(1)–Mn(2) angle of
ꢂꢂꢂ
In this equation N is Avogadro’s number, g is the Lande g fac-
tor, ꢄ is the Bohr magneton, k is the Boltzmann constant, T is
the absolute temperature, and J is the exchange integral. As
shown by the solid lines in Fig. 3, a good magnetic simulation
is obtained using the best-fit parameters of J ¼ ꢁ2:72 cmꢁ1
and g ¼ 2:00.
107.9ꢃ. Thus, the Mn Mn separation and the Mn(1)–O(1)–
Mn(2) angle in 1 2MeCN are enlarged relative to those of
[Mn2(bpmp)(AcO)2]ClO4.
ꢂ
The bis(ꢀ-acetato) dinickel(II) complex, [Ni2(bpmp)-
(AcO)2]BF4,26 has the Ni(1) Ni(2) separation of 3.40 A and
ꢀ
ꢂꢂꢂ
the Ni(1)–O(1)–Ni(2) angle of 114.5ꢃ. The twist angle between
the phenolic ring and the least-squares plane defined by Ni(1),
O(1), and Ni(2) is 47.3ꢃ. A similar twist angle is recognized for
The magnetic moment of 2 at room temperature is 2.88 mB
(per Ni) and the moment decreases with decreasing tempera-
ture to 0.23 mB at 2 K (Fig. 3). The ꢆA vs T curve shows a
slight increase below 6 K, implying some contamination of a
small amount of a paramagnetic impurity. Magnetic analyses
were carried out using the magnetic susceptibility expression
for (S1 ¼ 1)–(S2 ¼ 1) based on the isotropic Heisenberg model
and taking into consideration a fraction (ꢇ) of paramagnetic
impurity:
[Zn2(bpmp)(AcO)2]BF4 2MeOH (48.8ꢃ).25
ꢂ
Properties. The IR spectral assignments of 1–3 are made
by comparison with the IR spectra of [M2(bpmp)(AcO)2]-
(ClO4)2 (M ¼ Mn, Ni, Zn).24–26 Two intense bands at 1520
and 1348 cmꢁ1 are assigned to the ꢁas(NO2) and ꢁs(NO2) vi-
brations of the nitro group of BNPꢁ, respectively. Two prom-
inent bands at 1270–1271 and 1219–1220 cmꢁ1 are attributed
to ꢁ(P=O) vibrations of the bridging BNPꢁ group.
Each electronic absorption spectrum of 1–3 in DMSO has
two intense bands at 280 and 305–308 nm. The band at 280
nm is assigned to an intra-ligand transition associated with
bpmpꢁ and the band at 305–308 nm to an intra-ligand band
associated with BNPꢁ ion. Complex 2 shows two weak bands
ꢆA ¼ ð1 ꢁ ꢇÞfNg2ꢄ2=kTg ꢄ ½5 þ expðꢁ4J=kTÞꢅ
=½5 þ 3 expðꢁ4J=kTÞ
þ expðꢁ6J=kTÞꢅ þ ꢇ ꢄ ðg2=4TÞ þ Nꢃ:
ð2Þ
In this equation, Nꢃ is the temperature-independent paramag-
netism and other symbols have the same physical meanings as
in Eq. (1). The cryomagnetic behavior of 2 is well reproduced
using the best-fit parameters of J ¼ ꢁ13:3 cmꢁ1, g ¼ 2:14,
Nꢃ ¼ 120 ꢄ 10ꢁ6 cm3 molꢁ1 and ꢇ ¼ 0:006. Complex 1
3
at 597 and 988 nm which can be assigned to the T1g(F)
3A2g(F) and T2g(F) 3A2g(F) transitions, respectively, of
3
octahedral Ni(II).30 The spectra of 1–3 were practically
independent of concentration for 10ꢁ4–10ꢁ6
M
ꢁ1, indicating
shows a slightly weak antiferromagnetic interaction relative
24,29
the considerable stability of the [M2(bpmp)(AcO)2]þ core in
DMSO solution.
to [Mn2(bpmp)(AcO)2]ClO4 (J ¼ ꢁ4:8 cmꢁ1
)
whereas 2
shows a strong antiferromagnetic interaction relative to
[Ni2(bpmp)(AcO)2]BF4 (J ¼ ꢁ2:3 cmꢁ1).26
The magnetic moment of 1 at room temperature is 5.70 mB
per Mn and the moment decreased with decreasing tempera-
ture to 0.52 mB at 2 K (Fig. 3). This fact means an antiferro-
magnetic interaction between the two Mn(II) ions. Magnetic
analyses were carried out using the magnetic susceptibility
expression for (S1 ¼ 5=2)–(S2 ¼ 5=2) based on the isotropic
Heisenberg model (H ¼ ꢁ2JS1S2):31
The magnetic interaction in bis(ꢀ-acetato)-ꢀ-phenolato
dinuclear complexes is essentially mediated by the phenolic
oxygen atom.32,33 This must be also the case of bis(ꢀ-bnp)-
ꢀ-phenolato dinuclear complexes. The exchange integral of
dinuclear Ni1(II)–Ni2(II) (d8–d8) is given by the mean of four
one-electron exchange integrals,

H. Shiraishi et al.
Bull. Chem. Soc. Jpn., 78, No. 6 (2005) 1075
Relevance to Biological Phosphodiesterase. The com-
partmental ligands of the ‘‘end-off’’ type, 2,6-bis{N-[2-(di-
methylamino)ethyl]iminomethyl}-4-methylphenol (HL1), 2-
{N-[2-(dimethylamino)ethyl]iminomethyl}-6-{N-methyl-N-[2-
(dimethylamino)ethyl]aminomethyl}-4-bromophenol (HL2),
and 2,6-bis{2-[(2-pyridyl)ethyl]iminomethyl}-4-methylphenol
(HL3) (Fig. 5), are often used along with Hbpmp for modeling
bimetallic biosites. We have found that the dinuclear manga-
nese(II) complexes of HL1–HL3 hydrolyze BNPꢁ, whereas
the dinuclear nickel(II) and zinc(II) complexes of HL1–HL3
have little activity to hydrolyze BNPꢁ.38 The dinuclear manga-
nese(II) complexes of L1–L3 illustrate the significance of a pair
of Mn ions in biological hydrolysis of a phosphodiester and
can be regarded as functional models of Mn phosphodiester-
ases.10 Based on preliminary mass spectrometric studies, a ꢀ-
acetato-ꢀ-bnp species, [M2(L1)(AcO)(bnp)]þ (M ¼ Mn, Ni,
Zn), is produced in solution (along with a small amount of
bis-ꢀ-bnp species, [M2(L1)(bnp)2]þ) when [M2(L1)(AcO)2]-
ClO4 is treated with one equivalent of HBNP in DMSO.38
Obviously the bridging acetate group is readily replaced
with BNPꢁ, in harmony with the derivation of 1–3 from
[M2(bpmp)(AcO)2]ClO4 in this work. We have also confirmed
that the mass peak of [Mn2(L1)(AcO)(bnp)]þ diminishes with
time and finally disappears, but the mass peak of [Ni2(L1)-
(AcO)(bnp)]þ and the mass peak of [Zn2(L1)(AcO)(bnp)]þ
remain intact. We presume that the hydrolysis of BNPꢁ by
the dinuclear manganese(II) complexes of HL1–HL3 occurs
through the [Mn2(L)(AcO)(bnp)]þ (and [Mn2(L)(bnp)2]þ)
intermediate.
In this regard, we are interested in the behavior of 1 in
hydrous solvents, and we found that the bound BNPꢁ in 1,
as well as the bound BNPꢁ in 2 and 3, is not hydrolyzed in
hydrous DMSO, in marked contrast to the case of [Mn2(L1)-
(AcO)(bnp)]þ. The substantial difference between 1 and
[Mn2(L1)(AcO)(bnp)]þ is in the coordination number about
the metal center. In the case of [Mn2(L1)(AcO)(bnp)]þ, the
Mn center has a five-coordinate geometry, so that it can
accommodate a water molecule for hydrolyzing the bound
BNPꢁ.38 In the case of 1, the Mn center in a six-coordinate en-
vironment cannot accommodate a water molecule for hydro-
lyzing the bound BNPꢁ. This must also be the case of analo-
gous [FeZn(bpmp)(dpp)2]ClO4 with diphenyl phosphate
(DPPꢁ);20 the bridging DPPꢁ seems to be inert to hydrolysis.
2
2
2
2
2
2
2
J ¼ ð1=4Þ½ jðdx ꢁy ; dx ꢁy Þ þ jðdx ꢁy ; dz Þ
2
2
2
2
2
þ jðdz ; dx ꢁy Þ þ jðdz ; dz Þꢅ;
where local x and y axes are taken on each metal. In general,
ð3Þ
2
2
2
2
jðdx ꢁy ; dx ꢁy Þ is dominant among the four one-electron ex-
change integrals,34 so the magneto-structural correlation estab-
lished for Cu(II)–Cu(II) (d9–d9)35–37 can be applied to dinu-
2
2
2
2
clear nickel(II) complexes. The jðdx ꢁy ; dx ꢁy Þ integral of
ꢀ-hydroxo- and ꢀ-phenolato dinuclear complexes depends
upon the M–O–M angle and a stronger antiferromagnetic
interaction occurs when the M–O–M angle becomes larger.
As inferred from the comparison of the Mn–O–Mn angle of
1 2MeCN (119.9ꢃ) and the Mn–O–Mn angle of [Mn2(bpmp)-
ꢂ
(AcO)2]ClO4 (107.9ꢃ), [Ni2(bpmp)(bnp)2]ClO4 (2) must have
a large Ni–O–Ni angle relative to that of [Ni2(bpmp)-
(AcO)2]BF4 (114.5ꢃ). The enhanced antiferromagnetic interac-
tion of 2 can be explained by the enlargement of the Ni–O–
Ni angle (Fig. 4) that gives rise to an efficient spin exchange
1
2
2
2
2
2
through the dx ꢁy (Ni )jjp (O)jjd
(Ni ) pathway.
ꢈ
x ꢁy
The exchange integral of dinuclear Mn1(II)–Mn2(II) (d5–d5)
is given by the mean of 25 one-electron exchange integrals,
jðdk; dlÞ,
J ¼ ð1=25Þꢂjðdk; dlÞ;
ð4Þ
2
2
2
where dk and dl represent one of the five d-orbitals (dx ꢁy , dz ,
dxy, dxz, and dyz) of Mn1 and Mn2, respectively. The sign and
the magnitude of each jðdk; dlÞ depend complicatedly upon
structure, and because of this reason no magneto-structural
correlation has been established for dinuclear manganese(II)
complexes. In general, the J value for dinuclear manganese(II)
complexes is small (ꢁJ < 5 cmꢁ1) as the result of the com-
pensation of positive and negative jðdk; dlÞ components.
Fig. 4. Schematic illustration of antiferromagnetic inter-
2
2
action in ꢀ-phenolato dinickel(II) through dx ꢁy (Ni)-
2
2
kp (O)kd
(Ni) pathway: (left) for a small Ni–O–Ni
ꢈ
angle and (right) for a large Ni–O–Ni angle.
x ꢁy
Me
Me
Br
Me
N
N
OH
N
N
N
OH
N
N
OH
N
N
N
N
N
Me
Me
Me
Me
Me
Me
Me
Me
HL1
HL2
HL3
Fig. 5. Chemical structures of 2,6-bis{N-[2-(dimethylamino)ethyl]iminomethyl}-4-methylphenol (HL1), 2-{N-[2-(dimethyl-
amino)ethyl]iminomethyl}-6-{N-methyl-N-[2-(dimethylamino)ethyl]aminomethyl}-4-bromophenol (HL2), and 2,6-bis{2-[(2-pyr-
idyl)ethyl]iminomethyl}-4-methylphenol (HL3).

1076 Bull. Chem. Soc. Jpn., 78, No. 6 (2005)
Phosphodiester-Bridged Dinuclear Metal Complexes
13 D. H. Vance and A. W. Czarnik, J. Am. Chem. Soc., 115,
12165 (1993).
Conclusion
14 M. J. Yound and J. Chin, J. Am. Chem. Soc., 117, 10577
(1995).
15 H. Machinaga, K. Matsufuji, M. Ohba, M. Kodera, and H.
¯
Okawa, Chem. Lett., 2002, 716.
16 M. Lanznaster, A. Neves, A. J. Bortoluzzi, B. Szpoganicz,
and E. Schwingel, Inorg. Chem., 41, 5641 (2002).
2,6-Bis[N,N-di(2-pyridylmethyl)aminomethyl]-4-methyl-
phenol (Hbpmp) forms dinuclear Mn(II), Ni(II), and Zn(II)
complexes with two bis(p-nitrophenyl) phosphate (BNPꢁ)
ions: [M2(bpmp)(bnp)2]ClO4 (M ¼ Mn (1), Ni (2), and Zn
(3)). Complexes 1–3 are also derived from the bis(acetato)
complexes, [M2(bpmp)(AcO)2]ClO4, by the treatment with
NaBNP. The crystal structure of 1 is determined to have a
bis(ꢀ-bnp)-ꢀ-phenolato dinuclear core. Complex 1 exhibits
a weak antiferromagnetic interaction (J ¼ ꢁ2:72 cmꢁ1) and
complex 2 exhibits a moderate antiferromagnetic interaction
(J ¼ ꢁ13:3 cmꢁ1). The enhanced antiferromagnetic interac-
tion in 2 relative to [Ni2(bpmp)(AcO)2]BF4 (J ¼ ꢁ2:3
cmꢁ1) is explained by a large Ni–O–Ni angle that allows
¯
17 M. Yamami, H. Furutachi, T. Yokoyama, and H. Okawa,
Inorg. Chem., 37, 6832 (1998).
18 K. Arimura, M. Ohba, T. Yokoyama, and H. Okawa,
Chem. Lett., 2001, 1134.
¯
19 C. Bazzicalupi, A. Bencini, A. Bianchi, V. Fusi, C. Giorgi,
P. Paoletti, B. Valtancoli, and D. Zanchi, Inorg. Chem., 36, 2784
(1997).
20 K. Schepers, B. Bremer, B. Krebs, G. Henkel, E. Althaus,
B. Mosel, and W. Muller-Warmuth, Angew. Chem., Int. Ed. Engl.,
2
2
an efficient spin exchange through the dx ꢁy (Ni)jjp (O)jj-
ꢈ
¨
ꢁ
2
2
dx ꢁy (Ni) pathway. The bound BNP of the complexes is
not hydrolyzed in hydrous DMSO, because the metal center
in a six-coordinate environment cannot accommodate a water
molecule for hydrolysis.
29, 531 (1990).
21 T. Tanase, J. W. Yun, and S. J. Jippard, Inorg. Chem., 35,
3585 (1996).
22 C. He and S. J. Lippard, J. Am. Chem. Soc., 122, 184
(2000).
This work was supported by a Grant-in-Aid for Scientific
Research (No. 07454178) from the Ministry of Education
and Technology.
23 M. Suzuki, H. Kanatomi, Y. Demura, and I. Murase, Bull.
Chem. Soc. Jpn., 57, 1003 (1984).
24 M. Suzuki, M. Mikuriya, S. Murata, A. Uehara, H. Oshio,
S. Kida, and K. Saito, Bull. Chem. Soc. Jpn., 60, 4305 (1987).
25 L. Que, Jr., T. R. Holman, and M. P. Hendrich, Inorg.
Chem., 31, 939 (1992).
References
¯
1
D. E. Fenton and H. Okawa, ‘‘Perspectives on Bioinorganic
Chemistry,’’ JAI Press, London (1993), Vol. 2, p 81.
J. L. Vanhooke, M. M. Benning, F. M. Raushel, and H. M.
Holden, Biochemistry, 35, 6020 (1996).
E. Hough, L. K. Hansen, B. Birkness, K. Jynge, S. Hansen,
26 H. Adams, D. Bradshaw, and D. E. Fenton, Inorg. Chim.
Acta, 332, 195 (2002).
27 teXsan Crystal Structure Analysis Package, Molecular
Structure Corporation, Houston, TX (1985 and 1999).
28 C. K. Johnson, Report 3794, Oak Ridge National Labora-
tory, Oak Ridge, TN (1965).
29 S. Blanchard, G. Blondin, E. Riviere, M. Nierlich, and
J. Girerd, Inorg. Chem., 42, 4658 (2003).
30 D. B. Powell and N. Sheppard, Spectrochim. Acta, 17, 68
(1961).
2
3
A. Hardvik, C. Little, E. J. Dodson, and Z. Derewenda, Nature,
338, 357 (1989).
4
Biol., 215, 207 (1990).
5
(1991).
6
A. Lahm, S. Volbeda, F. Sakijama, and D. Suck, J. Mol.
E. E. Kim and H. W. Wyckoff, J. Mol. Biol., 218, 449
31 a) J. H. van Vleck, ‘‘The Theory of Electric and Magnetic
Susceptibilities,’’ Oxford University Press, London (1932). b) P.
A. M. Dirac, ‘‘The Principle of Quantum Mechanics,’’ Oxford
University Press, London (1958).
L. Que, Jr. and A. E. True, Prog. Inorg. Chem., 38, 91
(1990).
7
a) S. K. Burley, R. R. David, R. M. Sweet, A. Taylor,
and W. N. Lipscomb, J. Mol. Biol., 224, 113 (1992). b) C. R.
Kissinger, H. E. Parge, D. R. Knighton, C. T. Lewis, L. A.
Pelletier, A. Tempczyk, V. J. Kalish, K. D. Tucker, R. E.
Showalter, E. W. Moomaw, L. N. Gastinel, N. Habuka, X. Chen,
F. Maldonado, J. E. Barker, R. Bacquet, and E. Villafranca,
Nature, 378, 641 (1995).
32 W. H. Armstrong and S. J. Stephen, J. Am. Chem. Soc.,
106, 4632 (1984).
33 R. Hotzelmann, K. Wieghardt, J. Ensling, H. Romstedt,
P. Gutlich, E. Bill, U. Florke, and H.-J. Haupt, J. Am. Chem.
¨
Soc., 114, 9470 (1992).
¨
34 C. J. Cairns and D. H. Busch, Coord. Chem. Rev., 69, 1
(1986).
35 D. L. Lewis, K. T. McGregor, W. E. Hatfield, and D. J.
Hodgson, Inorg. Chem., 13, 1013 (1973).
8
M. P. Engloff, P. T. W. Cohen, P. Reinemer, and D.
Barford, J. Mol. Biol., 254, 942 (1995).
J. Goldberg, H. Huang, Y. Kwon, P. Greengard, A. C.
9
Nairn, and J. Kuriyan, Nature, 376, 745 (1995).
10 A. K. Das, N. R. Helps, P. T. W. Cohen, and D. Barford,
EMBO J., 15, 6798 (1996).
11 E. Bernard, S. Chardon-Noblat, A. Deronzier, and J.-M.
Latour, Inorg. Chem., 38, 190 (1999).
36 P. J. Hay, J. C. Thibeault, and R. Hoffmann, J. Am. Chem.
Soc., 97, 4884 (1975).
37 M. Handa, N. Koga, and S. Kida, Bull. Chem. Soc. Jpn.,
61, 3853 (1988).
38 R. Jikido, Master Thesis, Faculty of Science, Kyushu
University (2004). Manuscript has been prepared for publication.
´
12 F. Verge, C. Lebrum, M. Fontecave, and S. Menage, Inorg.
Chem., 42, 499 (2003).