Synthesis and structural characterization of dinuclear manganese(III) complexes with cyclam-based macrocyclic ligands having Schiff-base pendant arms as chelating agents

Article abstract of DOI:10.1246/bcsj.81.348

Reaction of a series of dodecadentate ligands (H₄L), 1,4,8,11-tetrakis(salicylideneaminoethyl)-1,4,8,11-tetraaza-cyclotetradecane and its substituted derivatives, with manganese(II) salts afforded ten dinuclear manganese(III) complexes, [Mn

Full text of DOI:10.1246/bcsj.81.348

348 Bull. Chem. Soc. Jpn. Vol. 81, No. 3, 348–357 (2008)
Ó 2008 The Chemical Society of Japan
Synthesis and Structural Characterization of Dinuclear Manganese(III)
Complexes with Cyclam-Based Macrocyclic Ligands Having
Schiff-Base Pendant Arms as Chelating Agents
ꢀ
Shusaku Wada and Masahiro Mikuriya
Department of Chemistry and Open Research Center for Coordination Molecule-based Devices,
School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda 669-1337
Received October 5, 2007; E-mail: junpei@kwansei.ac.jp
Reaction of a series of dodecadentate ligands (H4L), 1,4,8,11-tetrakis(salicylideneaminoethyl)-1,4,8,11-tetraaza-
cyclotetradecane and its substituted derivatives, with manganese(II) salts afforded ten dinuclear manganese(III) com-
plexes, [Mn2X2L] (X = O2CCH3, O2CC6H5, and N3), which were characterized by analyzing infrared and electronic
spectra and determining the temperature dependence of magnetic susceptibilities (4.5–300 K). Single-crystal X-ray
crystallography of [Mn2(O2CCH3)2(tbsaec)] 2CHCl3 (3 2CHCl3) (H4tbsaec = 1,4,8,11-tetrakis(5-bromosalicylidene-
ꢁ
ꢁ
aminoethyl)-1,4,8,11-tetraazacyclotetradecane), [Mn2(O2CC6H5)2(tbsaec)] (4), [Mn2(O2CC6H5)2(tcsaec)] (6) (H4tcsaec =
1,4,8,11-tetrakis(5-chlorosalicylideneaminoethyl)-1,4,8,11-tetraazacyclotetradecane), [Mn2(N3)2(tnaec)] 2CHCl3 (7
ꢁ
ꢁ
2CHCl3) (H4tnaec = 1,4,8,11-tetrakis(2-hydroxy-1-naphthylmethylideneaminoethyl)-1,4,8,11-tetraazacyclotetradecane),
[Mn2(O2CCH3)2(tmsaec)] (8) (H4tmsaec = 1,4,8,11-tetrakis(3-methoxysalicylideneaminoethyl)-1,4,8,11-tetraazacyclo-
tetradecane) showed that each manganese(III) ion is chelated by two Schiff-base pendant arms outside the central tetra-
azacyclotetradecane ring, forming an axially compressed octahedron (for 3, 4, 6, and 8) or trigonal bipyramid (for 7)
˚
with an intramolecular Mn–Mn distance of 9.676(4)–10.096(2) A. In accordance with the crystal structures, the magnetic
interaction between the two manganese ions was very weak with a rather significant zero-field splitting of the manga-
nese(III) ions.
There is a continuing interest in the chemistry of metal
complexes of tetraazamacrocycles. Introduction of functional
pendant arms to tetraazamacrocycles has produced a large
number of metal complexes and attracted intensive interest be-
cause of their specific structures, chemical properties, and po-
tential applications, such as extraction of metal ions and phar-
maceutical and biomedical NMR studies.1 For example, the
thermodynamic stability and kinetic inertness of the 1,4,7,10-
tetraazacyclododecane-1,4,7,10-tetraacetate complexes with
trivalent metal ions make this pendant-appended macrocyclic
ligand one of the most effective and safest contrast agents
for magnetic resonance imaging.1h,2 These types of tetraaza-
macrocyclic ligands usually bind one metal ion within the
macrocyclic cavity forming complexes in a 1:1 molar ratio.
Contrary to most tetraazamacrocyclic ligands, an N-substituted
octadentate ligand derived from 1,4,8,11-tetraazacyclotetradec-
ane (cyclam) having four aminoethyl pendant arms, 1,4,8,11-
tetrakis(2-aminoethyl)-1,4,8,11-tetraazacyclotetradecane (taec),
exclusively forms dinuclear metal species with various metal
ions, such as CrII, CoII, NiII, CuII, ZnII, and CdII ions.3 So far
only two types of structures are known for these systems in
the solid state: one is a trans-III conformation4 involving a cy-
clam ring as found in [M2(taec)]X4 (M = CrII, NiII, and CuII;
X = ClO4ꢂ, BF4ꢂ, and Brꢂ), and the other is a trans-I form4
as found in anion-bridged complexes of [M2(taec)X]Y2or3
(M = CoII, NiII, CuII, ZnII, and CdII; X = Clꢂ, Brꢂ, Iꢂ,
OHꢂ, and CO32ꢂ; Y = ClO4ꢂ, PF6ꢂ, CF3SO3ꢂ, BPh4ꢂ, and
Clꢂ).3 As for manganese ion, we expected to be able to prepare
dinuclear metal complexes by using this ligand and examined
reactions of taec with several manganese salts. However, we
could not obtain manganese complexes with taec, possibly be-
cause of the low affinity of the pendant amino-nitrogen donors
for manganese ions. It is well known that Schiff-base ligands
have been often used to construct manganese systems, because
the combination of the oxygen and nitrogen donor atoms are
favorable for binding manganese ions.5 For example, tetraden-
tate N2O2 Schiff-base salen ligand (H2salen = disalicylidene-
ethylenediamine) forms a number of manganese(III) com-
plexes of type [Mn(salen)X] (X = monovalent anion).5a Many
manganese complexes of Schiff-base ligands have been pre-
pared as potential model compounds for the oxygen-evolving
complex (OEC) of photosystem II (PSII) in green plants, in
which the existence of tetranuclear manganese site in the
S0–S4 states is widely accepted.5–11 In this study, we intro-
duced six kinds of salicylideneaminoethyl derivatives in place
of the pendant aminoethyl groups of the cyclam ring by using
a condensation reaction with salicylaldehyde, four of its
commercially available 3-, 5-, and 3,5-substituted derivatives,
and 2-hydroxy-1-naphthaldehyde in order to design new
Schiff-base ligands and studied the reactivity of these ligands
with manganese(II) salts in the hope of obtaining new types
of manganese complexes. We report here the synthesis and
characterization of dinuclear manganese(III) complexes with
these cyclam-based Schiff-base ligands. A preliminary de-
scription of one of these complexes has been previously
reported.12
Published on the web March 13, 2008; doi:10.1246/bcsj.81.348

S. Wada et al.
Bull. Chem. Soc. Jpn. Vol. 81, No. 3 (2008)
349
CH3OH). H4tbsaec (33 mg, 0.03 mmol) was dissolved in CHCl3
(5 cm3). To this solution was added a methanol solution (10 cm3)
of manganese(II) acetate tetrahydrate (15 mg, 0.06 mmol). The
reaction mixture was allowed to stand at room temperature, which
gave dark brown crystals. Yield: 34 mg (70%). Anal. Found: C,
40.09; H, 4.18; N, 7.14%. Calcd for C50H58Br4Mn2N8O8 2CHCl3
CH3OH: C, 39.80; H, 4.03; N, 7.01%. IR (KBr): ꢀas(CH2) 2983,
ꢀs(CH2) 2803, ꢀ(C=N) 1618, ꢀas(CO2ꢂ) 1556, ꢀs(CO2ꢂ) 1458
cmꢂ1. Diffuse reflectance spectrum: ꢁmax 255br, 370, 453sh,
720 nm.
Experimental
Synthesis. Unless otherwise specified, all reagents were pur-
chased commercially and used without further purification. The
parent compound, 1,4,8,11-tetrakis(2-aminoethyl)-1,4,8,11-tetra-
azacyclotetradecane (taec), was synthesized by a previously re-
ported procedure.3b
1,4,8,11-Tetrakis(5-bromosalicylideneaminoethyl)-1,4,8,11-
tetraazacyclotetradecane (H4tbsaec). Taec (51 mg, 0.14 mmol)
was dissolved in methanol (5 cm3). To this solution was added
5-bromosalicylaldehyde (111 mg, 0.55 mmol) dissolved in 5 cm3
of methanol, and the mixture was stirred for 1 h at room temper-
ature. The resulting yellow precipitate was filtered off and washed
with methanol. Yield: 105 mg (70%). Anal. Found: C, 49.70; H,
ꢁ
ꢁ
[Mn (O CC H ) (tbsaec)] 0.5CHCl H O
2
(4 0.5CHCl
Á
3Á
Á
3Á
2
2
6
5 2
H2O). The complex was prepared in the same way as 3, except
that manganese(II) benzoate dihydrate was used instead of man-
ganese(II) acetate tetrahydrate. Yield: 28 mg (62%). Anal. Found:
5.18; N, 10.11%. Calcd for C46H56Br4N8O4 0.5CH3OH: C,
ꢁ
C, 47.31; H, 4.62; N, 7.34%. Calcd for C60H62Br4Mn2N8O8
0.5CHCl3 H2O: C, 47.48; H, 4.25; N, 7.32%. IR (KBr): ꢀ(Ar–
ꢁ
49.84; H, 5.22; N, 10.00%. IR (KBr): ꢀ(Ar–H) 3083, ꢀas(CH2)
2970, ꢀs(CH2) 2790, ꢀ(C=N) 1634 cmꢂ1. Diffuse reflectance spec-
ꢁ
ꢂ
H) 3050, ꢀas(CH2) 2979, ꢀs(CH2) 2792, ꢀ(C=N) 1623, ꢀas(CO2
)
trum: ꢁmax 227, 261, 332, 431 nm. UV–vis: ꢁmax ("/Mꢂ1 cmꢂ1
measured in CHCl3) 330 (16600), 424 (1300) nm.
,
1536, ꢀs(CO2ꢂ) 1454 cmꢂ1. Diffuse reflectance spectrum: ꢁmax
228, 265sh, 368, 446sh, 707 nm.
1,4,8,11-Tetrakis(5-chlorosalicylideneaminoethyl)-1,4,8,11-
tetraazacyclotetradecane (H4tcsaec). This ligand was obtained
as yellow precipitate by the reaction of taec (52 mg, 0.14 mmol)
and 5-chlorosalicylaldehyde (92 mg, 0.59 mmol) in methanol
using the same method as that for H4tbsaec. Yield: 91 mg (70%).
Anal. Found: C, 59.19; H, 6.18; N, 12.09%. Calcd for C46H56Cl4-
[Mn (O CCH ) (tcsaec)] 2H O (5 2H O).
The complex
was prepared in the same way as 3, except that H4tcsaec was used
Á
instead of H4tbsaec. Yield: 25 mg (71%). Anal. Found: C, 50.86;
Á
2
2
3
2
2
2
H, 5.30; N, 9.37%. Calcd for C50H58Cl4Mn2N8O8 2H2O: C,
ꢁ
50.60; H, 5.27; N, 9.44%. IR (KBr): ꢀas(CH2) 2984, ꢀs(CH2)
2792, ꢀ(C=N) 1620, ꢀas(CO2ꢂ) 1561, ꢀs(CO2ꢂ) 1461 cmꢂ1. Dif-
fuse reflectance spectrum: ꢁmax 236, 371, 453sh, 540br, 715 nm.
[Mn (O CC H ) (tcsaec)] 2H O (6 2H O). The complex
N8O4 0.5H2O: C, 59.04; H, 6.14; N, 11.97%. IR (KBr): ꢀ(Ar–H)
ꢁ
3088, ꢀas(CH2) 2975, ꢀs(CH2) 2791, ꢀ(C=N) 1635 cmꢂ1. Diffuse
reflectance spectrum: ꢁmax 224, 262, 330, 430 nm. UV–vis: ꢁmax
("/Mꢂ1 cmꢂ1, measured in CHCl3) 329 (16900), 424 (1030) nm.
1,4,8,11-Tetrakis(2-hydroxy-1-naphthylmethylideneamino-
Á
Á
2
2
6
5 2
2
2
was prepared in the same way as 5, except that manganese(II)
benzoate dihydrate was used instead of manganese(II) acetate
tetrahydrate. Yield: 22 mg (57%). Anal. Found: C, 54.74; H, 5.30;
ethyl)-1,4,8,11-tetraazacyclotetradecane (H4tnaec).
This li-
N, 8.66%. Calcd for C60H62Cl4Mn2N8O8 2H2O: C, 54.97; H,
ꢁ
gand was obtained as yellow precipitate by the reaction of
taec (50 mg, 0.13mmol) and 2-hydroxy-1-naphthaldehyde (96mg,
0.56 mmol) in methanol using the same method as that for
H4tbsaec. Yield: 103 mg (77%). Anal. Found: C, 70.66; H, 7.14;
N, 10.54%. Calcd for C62H68N8O4 0.5CH3OH 3H2O: C, 70.86;
5.08; N, 8.55%. IR (KBr): ꢀ(Ar–H) 3058, ꢀas(CH2) 2983, ꢀs(CH2)
2790, ꢀ(C=N) 1624, ꢀas(CO2ꢂ) 1542, ꢀs(CO2ꢂ) 1457 cmꢂ1. Dif-
fuse reflectance spectrum: ꢁmax 228, 257sh, 374, 454sh, 709 nm.
[Mn (N ) (tnaec)] 2CHCl 2CH OH
(7 2CHCl 2CH -
Á 3Á Á 3Á
2
3 2
3
3
OH).
H4tnaec (30 mg, 0.03 mmol) was dissolved in CHCl3
ꢁ
ꢁ
H, 7.23; N, 10.58%. IR (KBr): ꢀ(Ar–H) 3061, ꢀas(CH2) 2938,
ꢀs(CH2) 2807, ꢀ(C=N) 1630 cmꢂ1. Diffuse reflectance spectrum:
(7 cm3). To this solution were added a methanol solution (7 cm3)
of manganese(II) acetate tetrahydrate (15 mg, 0.06 mmol) and an
aqueous solution (0.1 cm3) of sodium azide (8 mg, 0.12 mmol).
The mixture was allowed to stand at room temperature to give
dark brown crystals. Yield: 27 mg (61%). Anal. Found: C, 53.22;
H, 4.97; N, 13.06%. Calcd for C62H64Mn2N14O4 2CHCl3 2CH3-
ꢁmax 225, 274, 307, 387, 424 nm. UV–vis: ꢁmax ("/Mꢂ1 cmꢂ1
measured in CHCl3) 264 (51900), 274sh (35900), 310 (38300),
,
404 (32700), 422 (33700) nm.
[Mn2(O2CCH3)2(tsaec)] (1). A methanol solution (2 cm3) of
salicylaldehyde (39 mg, 0.32 mmol) was added dropwise to a stir-
red solution of taec (30 mg, 0.08 mmol) in methanol (5 cm3) at
room temperature. To this solution was added a methanol solution
(7 cm3) of manganese(II) acetate tetrahydrate (40 mg, 0.16 mmol).
The reaction mixture was allowed to stand at room temperature,
affording dark brown crystals. Yield: 46 mg (56%). Anal. Found:
C, 59.49; H, 6.19; N, 10.89%. Calcd for C50H62Mn2N8O8: C,
59.29; H, 6.17; N, 11.06%. IR (KBr): ꢀ(Ar–H) 3052, ꢀas(CH2)
ꢁ
ꢁ
OH: C, 53.49; H, 5.03; N, 13.23%. IR (KBr): ꢀ(Ar–H) 3000,
ꢀas(CH2) 2933, ꢀs(CH2) 2797, ꢀ(N3) 2038, ꢀ(C=N) 1616 cmꢂ1
.
Diffuse reflectance spectrum: ꢁmax 241, 336, 428, 688 nm. UV–
vis: ꢁmax ("/Mꢂ1 cmꢂ1, measured in DMSO) 308 (34900), 330sh
(31600), 402 (16100), 422 (14700), 625 (868) nm.
[Mn (O CCH ) (tmsaec)] 3H O (8 3H O). To an aceto-
Á
Á
2
2
3
2
2
2
nitrile solution (15 cm3) of taec (31 mg, 0.08 mmol) were added
3-methoxysalicylaldehyde (51 mg, 0.33 mmol) and manganese(II)
acetate tetrahydrate (63 mg, 0.26 mmol). The mixture was heated
for 5 min at 60 ꢃC. The resulting dark brown solution was allowed
to stand at room temperature to give dark brown crystals. Yield:
46 mg (48%). Anal. Found: C, 54.79; H, 5.98; N, 9.48%. Calcd
2984, ꢀs(CH2) 2792, ꢀ(C=N) 1620, ꢀas(CO2ꢂ) 1551, ꢀs(CO2
)
ꢂ
1447 cmꢂ1. Diffuse reflectance spectrum: ꢁmax 227, 262, 360,
527br, 706 nm.
[Mn2(O2CC6H5)2(tsaec)] (2). The complex was prepared in
the same way as 1, except that manganese(II) benzoate dihydrate
was used instead of manganese(II) acetate tetrahydrate. Yield:
51 mg (58%). Anal. Found: C, 63.20; H, 5.87; N, 9.73%. Calcd
for C60H66Mn2N8O8: C, 63.38; H, 5.85; N, 9.85%. IR (KBr):
ꢀ(Ar–H) 3049, ꢀas(CH2) 2981, ꢀs(CH2) 2791, ꢀ(C=N) 1625,
ꢀas(CO2ꢂ) 1548, ꢀs(CO2ꢂ) 1445 cmꢂ1. Diffuse reflectance spec-
trum: ꢁmax 226, 263sh, 365, 438br, 705 nm.
for C54H70Mn2N8O12 3H2O: C, 54.64; H, 6.45; N, 9.44%. IR
ꢁ
(KBr): ꢀ(Ar–H) 3058, ꢀas(CH2) 2935, ꢀs(CH2) 2792, ꢀ(C=N)
1620, ꢀas(CO2ꢂ) 1558, ꢀs(CO2ꢂ) 1446 cmꢂ1. Diffuse reflectance
spectrum: ꢁmax 232, 284, 366, 707 nm. UV–vis: ꢁmax ("/
M
ꢂ1 cmꢂ1, measured in DMSO) 366 (14600), 664 (1020) nm.
[Mn (O CCH ) (tdtbsaec)] 5H O (9 5H O). To a stirred
Á
added 3,5-di-tert-butylsalicylaldehyde (75 mg, 0.32 mmol) and a
Á
2
2
3
2
2
2
solution of taec (30 mg, 0.08 mmol) in methanol (10 cm3) were
[Mn (O CCH ) (tbsaec)] 2CHCl CH OH
(3 2CHCl
Á
3Á
Á
3Á
2
2
3
2
3

350 Bull. Chem. Soc. Jpn. Vol. 81, No. 3 (2008)
Dinuclear Manganese(III) Complexes
Table 1. Crystal Data and Data Collection Details
[Mn2(O2CCH3)2(tbsaec)]- [Mn2(O2CC6H5)2(tbsaec)] [Mn2(O2CC6H5)2(tcsaec)] [Mn2(O2CCH3)2(tmsaec)]
2CHCl3 (3 2CHCl3)
(4)
(6)
(8)
ꢁ
ꢁ
Formula
FW
C52H60Br4Cl6Mn2N8O8
1567.30
123
C60H62Br4Mn2N8O8
1452.70
293
C60H62Cl4Mn2N8O8
1274.86
293
C54H70Mn2N8O12
1133.06
293
Temperature/K
Crystal system
Space group
Monoclinic
P21=c
Triclinic
ꢀ
P1
Triclinic
ꢀ
P1
Monoclinic
P21=n
˚
a/A
14.002(3)
16.674(4)
14.700(4)
10.2688(16)
10.9941(17)
14.136(2)
111.821(3)
93.270(3)
91.562(3)
1477.2(4)
1
10.2036(19)
11.003(2)
14.138(3)
112.408(4)
93.521(5)
91.220(4)
1463.0(5)
1
10.858(2)
22.054(4)
12.590(3)
˚
b/A
˚
c/A
ꢄ/ꢃ
ꢅ/ꢃ
ꢆ/ꢃ
117.847(4)
108.342(4)
3
˚
V/A
Z
3034.0(12)
2
1.72
1.70
0:37 ꢄ 0:15 ꢄ 0:12
3.372
1.64–28.63
18656
2861.8(10)
2
1.32
1.31
0:42 ꢄ 0:15 ꢄ 0:05
0.507
1.85–28.43
17270
Dcalcd/g cmꢂ3
Dm/g cmꢂ3
Crystal size/mm3
ꢂ(Mo Kꢄ)/mmꢂ1
ꢇ range/ꢃ
No. of reflections
No. of unique
reflections
1.63
1.62
1.45
1.43
0:25 ꢄ 0:08 ꢄ 0:07
3.194
1.56–28.47
9156
0:22 ꢄ 0:20 ꢄ 0:07
0.677
1.56–28.40
9014
7090
6542
0.0581, 0.1158
0.691
6399
0.0719, 0.1675
0.847
6565
0.0759, 0.1391
1.019
R1, wR2 [I > 2ꢈðIÞ]a) 0.0417, 0.0950
Goodness-of-fit on F2 0.860
2
2
1=2
a) R1 ¼ ꢁjjFoj ꢂ jFcjj=ꢁjFoj; wR2 ¼ ½ꢁwðFo2 ꢂ Fc2Þ =ꢁwðFo2Þ ꢅ
.
methanol solution (5 cm3) of manganese(II) acetate tetrahydrate
(39 mg, 0.16 mmol). The mixture was allowed to stand at room
temperature to give dark green crystals. Yield: 71 mg (57%). Anal.
X-ray Crystal Structure Analyses. A preliminary examina-
tion was made, and data were collected on a Bruker CCD X-ray
diffractometer (SMART APEX) using graphite-monochromated
Mo Kꢄ radiation. Crystal data and details concerning data collec-
tion are given in Table 1. The structures were solved by direct
methods and refined by full-matrix least-squares methods. The hy-
drogen atoms were inserted at their calculated positions and fixed
there. All of the calculations were carried out on a Pentium IV
Windows 2000 computer utilizing the SHELXTL software pack-
age.14 Crystallographic data have been deposited with Cambridge
Crystallographic Data Centre: Deposit numbers CCDC-641438–
641442. 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, UK; Fax: +44 1223 336033; e-mail:
deposit@ccdc.cam.ac.uk).
Found: C, 63.25; H, 8.51; N, 6.91%. Calcd for C82H126Mn2N8O8
ꢁ
5H2O: C, 63.46; H, 8.83; N, 7.22%. IR (KBr): ꢀas(CH2) 2955,
ꢀs(CH2) 2799, ꢀ(C=N) 1625, ꢀas(CO2ꢂ) 1552, ꢀs(CO2ꢂ) 1436
cmꢂ1. Diffuse reflectance spectrum: ꢁmax 229, 280sh, 376, 463sh,
757 nm. UV–vis: ꢁmax ("/Mꢂ1 cmꢂ1, measured in CHCl3) 270sh
(43700), 372 (16700), 736 (1410) nm.
[Mn (O CC H ) (tdtbsaec)] 3H O (10 3H O). The com-
2
Á
Á
2
6
5
2
2
2
plex was prepared in the same way as 9, except that manganese(II)
benzoate dihydrate was used instead of manganese(II) acetate
tetrahydrate. Yield: 80 mg (61%). Anal. Found: C, 67.28; H, 8.24;
N, 6.67%. Calcd for C92H130Mn2N8O8 3H2O: C, 67.38; H, 8.36;
ꢁ
N, 6.83%. IR (KBr): ꢀas(CH2) 2953, ꢀs(CH2) 2793, ꢀ(C=N) 1621,
ꢀas(CO2ꢂ) 1535, ꢀs(CO2ꢂ) 1437 cmꢂ1. Diffuse reflectance spec-
trum: ꢁmax 228, 271sh, 373, 462sh, 773 nm. UV–vis: ꢁmax ("/
M
ꢂ1 cmꢂ1, measured in CHCl3) 268 (46600), 373 (16400), 750
Results and Discussion
(1390) nm.
Measurements.
Schiff-Base Ligands. The synthetic route for the present
Schiff-base ligands is shown in Scheme 1. The analytical data
are in good agreement with the theoretical requirements of the
Schiff-base ligands. The ligands have a strong IR band at
1630–1635 cmꢂ1, which is attributed to a ꢀ(C=N) stretching
vibration. Manganese complexes were prepared by the reac-
tion of manganese(II) salts and the Schiff-base ligands in a
2:1 molar ratio in methanol, chloroform–methanol, or aceto-
nitrile in good yields. In the cases of H4tsaec, H4tmsaec, and
H4tdtbsaec, the reaction afforded an oily substance, and we
could not obtain any solid products of the Schiff-base ligands
by the same reaction as those of H4tbsaec, H4tcsaec, and
H4tnaec. Therefore, we used a template reaction to prepare
manganese complexes of these Schiff-base ligands. There is
Elemental analyses of carbon, hydrogen,
nitrogen, and sulfur were conducted using a Thermo Finnigan
FLASH EA 1112 series CHNO-S Analyzer. Infrared spectra were
measured with a JASCO MFT-2000 FT-IR Spectrometer in the
4000–600 cmꢂ1 region. The electronic spectra were measured
with a Shimadzu UV–vis–NIR Recording Spectrophotometer
Model UV-3100. The temperature dependence of the magnetic
susceptibilities was measured with a Quantum Design MPMS-
5S SQUID susceptometer operating at a magnetic field of 0.5 T
over a temperature range of 4.5–300 K. The susceptibilities
were corrected for the diamagnetism of constituent atoms using
Pascal’s constants.13 The effective magnetic moments were calcu-
pffiffiffiffiffiffiffiffiffiffi
lated from the equation ꢂeff ¼ 2:828 ꢃMT, where ꢃM is the
magnetic susceptibility per mole of MnIII dinuclear unit.
2

S. Wada et al.
Bull. Chem. Soc. Jpn. Vol. 81, No. 3 (2008)
351
NHTs
NHTs
TsHN
TsHN
NH2
NH2
H2N
H2N
H
H
H
H
N
N
N
N
N
N
N
N
N
N
N
N
a)
b), c)
O
Ts =
CH3
S
O
d)
e)
R2
R2
R1
R1
HO
N
N
N
N
OH
HO
N
N
N
N
OH
N
N
N
N
N
N
N
N
HO
OH
R2
HO
OH
R1
R1
R2
H4tnaec
H4tsaec (R1, R2 =H)
H4tbsaec (R1 = H, R2 = Br)
H4tcsaec (R1 = H, R2 = Cl)
H4tdtbsaec (R1, R2 = tert-Bu)
H4tmsaec (R1 = OCH3, R2 =H)
Scheme 1. Reagents: a) N-Tosylaziridine/CH3CN/81 ꢃC/15 h. b) HBr/CH3COOH/110 ꢃC/40h. c) Ion-exchange column. d) Salicyl-
aldehyde derivatives/CH3OH. e) 2-Hydroxy-1-naphthaldehyde/CH3OH.
one vibration band in the IR spectra of the manganese com-
plexes assignable to the coordinated ꢀ(C=N) stretching vibra-
tion (1616–1625 cmꢂ1), which is slightly shifted from the
stretching band of the free Schiff-base ligand toward lower fre-
quency by coordination to the metal ion. Elemental analyses
confirmed the 1:2:2 deprotonated Schiff-base ligand:metal
ion:anion stoichiometry of the manganese(III) complexes.
Dinuclear Manganese(III) Complexes with Acetate or
Benzoate as the Additional Ligands, [Mn2(O2CCH3)2(L)]
[L = tsaec (1), tbsaec (3), tcsaec (5), tmsaec (8), tdtbsaec
(9)] and [Mn2(O2CC6H5)2(L)] (L = tsaec (2), tbsaec (4),
tcsaec (6), tdtbsaec (10)). When manganese(II) acetate or
manganese(II) benzoate was reacted with the Schiff-base li-
gands, dinuclear manganese(III) complexes, [Mn2(O2CCH3)2-
(L)] (L = tsaec (1), tbsaec (3), tcsaec (5), tmsaec (8), tdtbsaec
(9)) and [Mn2(O2CC6H5)2(L)] (L = tsaec (2), tbsaec (4), tcsaec
(6), tdtbsaec (10)) were isolated in good yields (46–71%). In
the IR spectra of these complexes, two strong vibration peaks
of carboxylato groups appear at 1535–1561 and 1436–1461
cmꢂ1, which are attributed to the antisymmetric and symmet-
ric ꢀ(CO2ꢂ) stretching bands, respectively. The ꢂ values of
ꢀas(CO2ꢂ) ꢂ ꢀs(CO2ꢂ) are in the range of those of bidentate-
acetate complexes.15
tained for [Mn2(O2CCH3)2(tbsaec)] 2CHCl3 (3 2CHCl3),
ꢁ
ꢁ
[Mn2(O2CCH3)2(tmsaec)] (8), [Mn2(O2CC6H5)2(tbsaec)] (4),
and [Mn2(O2CC6H5)2(tcsaec)] (6). The crystal structures of
these complexes were determined by X-ray crystal structure
analysis. An ORTEP drawing of the molecular structure of
3 2CHCl3 is shown in Fig. 1. Selected bond distances and
ꢁ
angles are listed in Table 2. The structure is very similar to
that of a previously reported dinuclear manganese(III) com-
plex, [Mn2(O2CCH3)2(tcsaec)] 2CHCl3 (5 2CHCl3).12 The
ꢁ
ꢁ
asymmetric unit contains one-half of the dinuclear unit with
the cyclam-ring moiety centered on a crystallographic inver-
sion center. Two pairs of the pendant groups point away from
the cyclam ring, forming an extended conformation. It should
be noted that the cyclam ring moiety takes the trans IV form,4
which has never been found in metal complexes of taec (the
word ‘‘trans III’’ in Ref. 12a should be corrected to ‘‘trans
IV’’).3 The two manganese ions are bound to the two pendant
Schiff-base groups in a cis-ꢄ fashion16 (the word ‘‘cis-ꢅ’’ in
Ref. 12a should be corrected to ‘‘cis-ꢄ’’) below and above
the cyclam ring moiety. The distance between the two manga-
0
˚
nese ions (Mn1 Mn1 ) is 10.096(2) A. Each manganese ion is
ꢁꢁꢁ
coordinated by two imino-nitrogen atoms and two phenoxo-
oxygen atoms of two 5-bromosalicylideneaminoethyl pendant
arms of tbsaec4ꢂ and two oxygen atoms of the bidentate ace-
Single crystals suitable for X-ray diffraction study were ob-

352 Bull. Chem. Soc. Jpn. Vol. 81, No. 3 (2008)
Dinuclear Manganese(III) Complexes
ꢃ
C25
C24
˚
Table 2. Selected Bond Distances (A) and Angles ( ) with
Their Estimated Standard Deviations in Parentheses
O4
O3
C12
C11
C20
C21
C22
[Mn2(O2CCH3)2(tbsaec)] 2CHCl3 (3 2CHCl3)
Br1
C10
ꢁ
ꢁ
Mn1–N3
O2
C19
O1
Mn1
C13
C14
C9
Br2
C23 C18
Mn1–O1
Mn1–O2
Mn1–O3
1.863(2)
1.855(3)
2.195(3)
178.4(1)
89.8(1)
90.3(1)
91.1(1)
91.3(1)
58.8(1)
87.7(1)
89.7(1)
Mn1–O4
2.253(3)
2.105(3)
2.102(3)
91.0(1)
90.3(1)
87.8(1)
146.4(1)
146.5(1)
87.7(1)
C8
N3
N4
C17
C16
C7
C6
C15
N1
N2
Mn1–N4
C1
O1–Mn1–O2
O1–Mn1–O3
O1–Mn1–O4
O2–Mn1–O3
O2–Mn1–O4
O3–Mn1–O4
O1–Mn1–N3
O1–Mn1–N4
O2–Mn1–N3
O2–Mn1–N4
O3–Mn1–N3
O3–Mn1–N4
O4–Mn1–N3
O4–Mn1–N4
N3–Mn1–N4
C2
C3
C4
C5
N4'
N3'
O1'
Mn1'
O2'
O4'
O3'
125.7(1)
Fig. 1. ORTEP drawing of the structure of [Mn2(O2-
CCH3)2(tbsaec)] 2CHCl3 (3 2CHCl3) showing the 50%
probability thermal ellipsoids and atom labeling scheme.
Hydrogen atoms are omitted for clarity.
[Mn2(O2CC6H5)2(tbsaec)] (4)
ꢁ
ꢁ
Mn1–O1
Mn1–O2
Mn1–O3
1.843(5)
1.891(5)
2.130(5)
176.4(2)
88.6(2)
80.0(2)
94.5(2)
103.3(2)
55.3(2)
89.1(2)
92.3(2)
Mn1–O4
Mn1–N3
Mn1–N4
O2–Mn1–N3
O2–Mn1–N4
O3–Mn1–N3
O3–Mn1–N4
O4–Mn1–N3
O4–Mn1–N4
N3–Mn1–N4
2.513(6)
2.087(5)
2.135(6)
89.7(2)
˚
tate ligand. The manganese ion (Mn1) lies 0.031 A above the
O1–Mn1–O2
O1–Mn1–O3
O1–Mn1–O4
O2–Mn1–O3
O2–Mn1–O4
O3–Mn1–O4
O1–Mn1–N3
O1–Mn1–N4
plane described by the two imino-nitrogen atoms (N3, N4)
and the acetato-oxygen atoms (O3, O4). The coordination
geometry can be regarded as an axial compressed octahedron
with two short bonds with phenoxo-oxygen atoms (Mn1–
85.8(2)
138.8(2)
90.7(2)
83.8(2)
145.0(2)
130.5(2)
˚
˚
O1 = 1.863(2) A, Mn1–O2 = 1.855(3) A) and four long bonds
with imino-nitrogen and acetato-oxygen atoms (Mn1–O3 =
˚
˚
˚
2.195(3) A, Mn1–O4 = 2.253(3) A, Mn1–N3 = 2.105(3) A,
˚
Mn1–N4 = 2.102(3) A), in contrast to the fact that most
manganese(III) complexes show axially elongated octahedra
for MnIII centers.5,6 This may be ascribed to the combination
of the pseudo Jahn–Teller distortion of a high-spin d4 ion
and the preference of MnIII for phenoxo-oxygen donors over
imino-nitrogen and acetato-oxygen donor atoms.17 The tetra-
dentate N2O2 Schiff-base moiety is not planar in this complex;
the dihedral angle between the two salicylideneamino planes
defined by O1–C10–C11–C12–C13–C14–C9–C8 and O2–C19–
C20–C21–C22–C23–C18–C17 is 48.0ꢃ. Therefore, the plane
defined by O1–N3–N4–O2 deviates from the planar configura-
[Mn2(O2CC6H5)2(tcsaec)] (6)
Mn1–O1
Mn1–O2
Mn1–O3
1.830(4)
1.884(4)
2.128(5)
176.7(2)
88.1(2)
80.5(2)
94.5(2)
102.6(2)
55.8(2)
89.4(2)
91.9(2)
Mn1–O4
Mn1–N3
Mn1–N4
O2–Mn1–N3
O2–Mn1–N4
O3–Mn1–N3
O3–Mn1–N4
O4–Mn1–N3
O4–Mn1–N4
N3–Mn1–N4
2.482(6)
2.085(5)
2.123(5)
89.9(2)
O1–Mn1–O2
O1–Mn1–O3
O1–Mn1–O4
O2–Mn1–O3
O2–Mn1–O4
O3–Mn1–O4
O1–Mn1–N3
O1–Mn1–N4
86.2(2)
139.4(2)
90.2(2)
83.8(2)
145.1(2)
130.4(2)
˚
˚
tion within ꢆ0:48 A, and the manganese ion is 0.49 A above
this mean plane. A view of the molecular packing in the crystal
is shown in Fig. 2. The closest intermolecular Mn Mn dis-
ꢁꢁꢁ
˚
tance is 6.795(2) A of Mn1 Mn1 ðꢂx þ 1; ꢂy þ 1; ꢂz þ 1Þ,
[Mn2(O2CCH3)2(tmsaec)] (8)
ꢁꢁꢁ
which is shorter than the intramolecular Mn Mn distance.
ꢁꢁꢁ
Mn1–O1
Mn1–O3
Mn1–O5
1.867(3)
1.852(3)
2.063(3)
177.3(1)
91.8(1)
95.2(1)
89.9(1)
87.5(1)
56.9(1)
86.7(1)
90.2(1)
Mn1–O6
Mn1–N3
Mn1–N4
O3–Mn1–N3
O3–Mn1–N4
O5–Mn1–N3
O5–Mn1–N4
O6–Mn1–N3
O6–Mn1–N4
N3–Mn1–N4
2.466(3)
2.151(3)
2.059(3)
91.2(1)
89.6(1)
91.9(1)
144.4(1)
148.7(1)
87.5(1)
The crystal contains chloroform molecules, which form hydro-
gen bonds with the acetate ligands [O4 (O CCH ) C26
ꢁꢁꢁ
2
3
˚
(CHCl3) ðꢂx þ 1; y þ 0:5; ꢂz þ 0:5Þ 3.036(5) A].
O1–Mn1–O3
O1–Mn1–O5
O1–Mn1–O6
O3–Mn1–O5
O3–Mn1–O6
O5–Mn1–O6
O1–Mn1–N3
O1–Mn1–N4
ORTEP drawings of the crystal structures of 8, 4, and 6 are
shown in Figs. 3, 4, and 5, respectively. The structures of 8, 4,
and 6 are similar to those of 3 2CHCl3 and 5 2CHCl3, name-
ꢁ
ꢁ
ly, the coordination geometry is a similar compressed octa-
hedron with two shorter Mn–phenoxo bonds and four longer
bonds with imino-nitrogen and carboxylato-oxygen atoms
123.7(1)
(Table 2). The intramolecular Mn1 Mn10 distances are
ꢁꢁꢁ
˚
9.988(2), 9.865(3), and 9.847(3) A, for 8, 4, and 6, respective-
ly. Although the coordination modes of the carboxylato li-
gands are unsymmetrically bidentate, being different from
those of 3 2CHCl3 and 5 2CHCl3, the IR spectra of these
complexes exhibit absorptions indicative of the bidentate na-
ture of the carboxylato groups.15 For 4 and 6, the manga-
˚
nese(III) ion lies 0.05 A above the mean plane described by
the two imino-nitrogen atoms (N3 and N4) and the two ben-
zoato-oxygen atoms (O3 and O4). The dihedral angles be-
tween the two salicylideneamino planes defined by O1–C10–
ꢁ
ꢁ

S. Wada et al.
Bull. Chem. Soc. Jpn. Vol. 81, No. 3 (2008)
353
C28
C29
C27
C30
C26
C25
C24
O4
O3
C21
C20
Br2
C12
C11
C19
O2
O1
C10
C22
Mn1
C23
C18
C13
Br1
C9 C14
C17
N4
C8
N3
C7
C6
C16
C5
C15
N2
C4
N1
C1
C3
C2
N3'
N4'
Mn1' O2'
O3'
b
O1'
O4'
c
a
Fig. 2. Packing diagram of [Mn2(O2CCH3)2(tbsaec)]
2CHCl3 (3 2CHCl3). Hydrogen atoms are omitted for
ꢁ
ꢁ
clarity.
Fig. 4. ORTEP drawing of the structure of [Mn2(O2CC6-
H5)2(tbsaec)] (4) showing the 45% probability thermal
ellipsoids and atom labeling scheme. Hydrogen atoms
are omitted for clarity.
C27
C15
C26
O6
C12
C11
O5
C25
O2
O4
C13
C28
C14
C23
C27
C26
C22
O1
C24
Mn1
O3
C10
C29
C9
C21
C8
C19 C20
N3
C17
C25
C2
C30
N4
C18
C7
C6
O3
C1
O4
O1
C21
C22
C20
C23
C16
N1
C12
C11
C19
C18
Cl2
C2
O2
C10
Mn1
N2
C5
C13
Cl1
C3
C14
C9
C17
C8
N4
C7
N3
C4
C16
C5
N4'
C6
C15
N2
C4
N3'
N1
C3
C2
C1
Mn1'
O1'
O3'
O6'
O4'
O2'
N3'
N4'
O5'
Mn1'
O2'
O1'
O4'
O3'
Fig. 3. ORTEP drawing of the structure of [Mn2(O2-
CCH3)2(tmsaec)] (8) showing the 40% probability thermal
ellipsoids and atom labeling scheme. Hydrogen atoms are
omitted for clarity.
Fig. 5. ORTEP drawing of the structure of [Mn2(O2CC6-
H5)2(tcsaec)] (6) showing the 40% probability thermal
ellipsoids and atom labeling scheme. Hydrogen atoms
are omitted for clarity.
C11–C12–C13–C14–C9–C8 and O2–C19–C20–C21–C22–
C23–C18–C17 are 42.0 and 42.9ꢃ for 4 and 6, respectively.
The planes defined by the two imino-nitrogen atoms (N3 and
N4) and the two phenoxo-oxygen atoms (O1 and O2) are dis-
˚
torted from the plane by ꢆ0:42 A, and the manganese ion is
ꢂy þ 2; ꢂzÞ for 8, respectively.
˚
0.47 A above the mean planes for both the complexes. In the
Dinuclear Manganese(III) Complex with Azide as the
Additional Ligands, [Mn2(N3)2(tnaec)] (7). When manga-
nese(II) acetate was reacted with the tnaec ligand in chloro-
form–methanol, the reaction solution became yellowish
brown. However, the solution did not afford any precipitate
even after standing for months at room temperature. This con-
trasts with the case for the corresponding salen type Schiff-
base, bis(2-hydroxy-1-naphthylmethylidene)ethylenediamine
(Hbne), which forms a polymeric catena-ꢂ-acetatomanga-
nese(III) complex with bne, [Mn(O2CCH3)(bne)]n.18 By add-
ing azide ion to the solution, we isolated a dinuclear manga-
nese(III) complex, [Mn2(N3)2(tnaec)] (7), in good yield (61%).
case of 8, the tetradentate N2O2 Schiff-base moiety is severely
distorted, with a dihedral angle between the two salicylidene-
amino planes defined by O1–C14–C13–C12–C11–C10–C9–C8
and O3–C24–C23–C22–C21–C20–C19–C18 of 60.0ꢃ, which
is the largest of the present complexes. This may be due to
the steric hindrance of the 3-methoxy groups of tmsaec4ꢂ
.
Similarly, the plane defined by O1–N3–N4–O3 is distorted
˚
from the plane by ꢆ0:49 A and the manganese ion being
˚
0.52 A above the mean plane. In the crystals, the closest inter-
˚
molecular Mn Mn separations are 7.873(3) A of Mn1 Mn1
ꢁꢁꢁ ꢁꢁꢁ
˚
ðꢂx; ꢂy þ 1; ꢂz þ 1Þ for 4, 6.882(3) A of Mn1 Mn1 ðꢂx þ 1;
ꢁꢁꢁ
ꢂy þ 1; ꢂz þ 1Þ for 6, and 6.899(2) A of Mn1 Mn1 ðꢂx;
ꢁꢁꢁ
The IR spectrum of 7 showed a strong band at 2038 cmꢂ1
,
˚

354 Bull. Chem. Soc. Jpn. Vol. 81, No. 3 (2008)
Dinuclear Manganese(III) Complexes
N7'
N6'
N5'
336
241
226
428
O2'
Mn1'
O1'
688
N3'
N4'
C5
263sh
C3
C2
C4
N2
365
C1
N1
C6
C19
705
706
C20
N3
C7
N4
227
262
C21
C22
C31
O1
C8
C30
C10
C9
C11
C29
C12
Mn1
360
C28
C13
O2
C23
C24
C14
C18
C17
C27 C26
C25
C16
N5
C15
N6
N7
Fig. 6. ORTEP drawing of the structure of [Mn2(N3)2-
(tnaec)] 2CHCl3 (7 2CHCl3) showing the 25% probabili-
ꢁ
ꢁ
ty thermal ellipsoids and atom labeling scheme. Hydrogen
atoms are omitted for clarity.
200
400
600
800
1000 1200 1400
Wavelength/ nm
which was assigned to the asymmetric stretching vibration of
the terminal azide group,15 in good accord with the structural
results (vide infra). In the case of manganese complexes, most
Fig. 7. Diffuse reflectance spectra of [Mn2(O2CCH3)2-
(tsaec)] (1) (bottom), [Mn2(O2CC6H5)2(tsaec)] (2) (mid-
dle), and [Mn2(N3)2(tnaec)] (7) (top).
ꢂ
azide complexes have N3 bridges. Only a few structurally
characterized complexes of MnIII having terminal N3 ligands
oxygen to the MnIII d orbitals.17,21
ꢂ
have been reported.8h,19 Unfortunately, we failed to obtain
satisfactory crystallographic data and therefore a more detailed
analysis of the structure of 7 could not be attained.20 An
ORTEP drawing of the preliminary X-ray crystal structure of
In the case of azide complex 7, the diffuse reflectance spec-
tra had four bands at 241, 336, 428, and 688 nm. Compared
to those of the acetates and benzoates, the distinctive bands
ꢀ
at 336 and 428 nm were assigned to the ꢉ–ꢉ transition of
7 2CHCl3 is shown in Fig. 6. The manganese(III) ion is co-
coordinated azide ligands and the N3–Mn charge-transfer
bands, tentatively.19b,19c In DMSO solution, the azide complex
exhibited five absorptions at 308, 330sh, 402, 422, and 625 nm
with molar extinction coefficients of 17500, 15800, 8050,
7350, and 434 dm3 molꢂ1 cmꢂ1/Mn, respectively. Similar to
the acetates and benzoates, the lowest band at 688 nm was
assigned to d–d transition bands for the five-coordinate
MnIII ion.
ꢁ
ordinated by two imino-nitrogen atoms, two phenoxo-oxygen
atoms from tnaec4ꢂ, and one nitrogen atom from azide ligand,
forming a trigonal bipyramidal geometry. The axial sites are
occupied by the phenoxo-oxygen atoms (O1 and O2), with
shorter bond lengths (Mn1–O1 = 1.835(7), Mn1–O2 =
˚
1.856(7) A) compared with the equatorial Mn–N distances
(Mn1–N3 = 2.055(8), Mn1–N4 = 2.002(9), Mn1–N5 =
˚
2.064(12) A). These bond distances should be considered with
Magnetic Properties of Complexes 1–10. The tempera-
ture dependence of the magnetic susceptibilities of 1–10 was
measured on powdered samples in the temperature range of
4.5–300 K. The magnetic data of 3, 8, and 7 are shown in
Figs. 8, 9, and 10, respectively, in the form of ꢃM and ꢂeff
vs. T plots as representative examples. The magnetic moments
of these complexes at 300 K were in the range of 6.27–6.97 ꢂB
some care because of the low accuracy of this structure analy-
0
˚
sis. The intramolecular Mn1 Mn1 distance is 9.676(4) A. In
ꢁꢁꢁ
the crystal, the closest intermolecular Mn Mn separation is
˚
ꢁꢁꢁ
8.063(5) A between Mn1 Mn1 ðꢂx þ 1=2; ꢂy þ 3=2; ꢂz þ 1Þ.
ꢁꢁꢁ
Electronic Spectra of Complexes 1–10. The UV–visible
spectra of the present complexes were measured by diffuse re-
flectance spectra, because most of them are insoluble in water
and organic solvents. The diffuse reflectance spectra of 1, 2,
and 7 are shown in Fig. 7 as examples. The spectra of the ace-
tates and the benzoates are almost identical, confirming the
similar coordination environments. The complexes exhibited
two or three strong bands (226–236, 255–284, and 360–376
nm) in the UV region and a band at 705–773 nm with shoulder
at 438–540 nm in the visible region. In CHCl3 solution, acetate
complex 9 showed three absorptions at 270sh, 372, and 736 nm
with molar extinction coefficients of 21850, 8350, and 705
dm3 molꢂ1 cmꢂ1/Mn, respectively. Judging from the intensi-
ties of the absorption bands, we assigned the lowest-energy
broad band at 705–773 nm to d–d transition bands for MnIII
ion in a compressed octahedral environment.17 The shoulder
band around 438–540 was assigned by analogy to other man-
ganese(III) complexes to be a LMCT band from the phenoxo-
(per MnIII unit) and are in good agreement with the spin-only
2
value (6.93 ꢂB) of two noninteracting high-spin MnIII (S ¼ 2)
ions. For complexes 1–6, 8, and 9, the magnetic moments re-
mained constant upon lowering of the temperature to the range
of 5–20 K, suggesting almost no magnetic interaction between
manganese(III) ions. When the temperature was lowered
further, the magnetic moment decreased for these complexes,
which is thought to be due to the zero-field-splitting from
the manganese(III) ion or antiferromagnetic intermolecular
interactions. In the case of 7 and 10, the magnetic moment
slightly increased as the temperature decreased from 300 to
4.5 K, suggesting a weak ferromagnetic interaction between
manganese(III) ions. In order to evaluate the magnetic be-
haviors described above, the magnetic data were analyzed
with the van Vleck equation based on the Heisenberg model
(H ¼ ꢂ2JS1 S2 (S1 ¼ S2 ¼ 2)):22
ꢁ

S. Wada et al.
Bull. Chem. Soc. Jpn. Vol. 81, No. 3 (2008)
355
8
6
4
2
0
where J is an exchange integral for the two manganese(III)
ions and the other symbols have their usual meanings. The
best-fitting parameters obtained were as follows (Fig. 8):
g ¼ 2:02, J ¼ ꢂ0:16 cmꢂ1, ꢇ ¼ þ0:69 K for 1; g ¼ 1:93,
J ¼ ꢂ0:09 cmꢂ1, ꢇ ¼ þ0:50 K for 2; g ¼ 2:00, J ¼ þ0:53
cmꢂ1, ꢇ ¼ ꢂ2:3 K for 3; g ¼ 1:87, J ¼ þ0:54 cmꢂ1, ꢇ ¼
ꢂ2:8 K for 4; g ¼ 1:96, J ¼ ꢂ0:23 cmꢂ1, ꢇ ¼ þ0:78 K for
5; g ¼ 1:88, J ¼ ꢂ0:20 cmꢂ1, ꢇ ¼ þ0:73 K for 6; g ¼ 1:90,
J ¼ þ0:49 cmꢂ1, ꢇ ¼ ꢂ1:3 K for 7; g ¼ 2:01, J ¼ þ0:26
cmꢂ1, ꢇ ¼ ꢂ2:3 K for 8; g ¼ 1:91, J ¼ ꢂ0:14 cmꢂ1, ꢇ ¼
þ0:69 K for 9; g ¼ 1:86, J ¼ þ0:55 cmꢂ1, ꢇ ¼ ꢂ1:5 K for
10. The obtained J values are very small, showing that the
magnetic interaction within the dinuclear molecule can be neg-
ligibly weak. In our system, we did not expect any significant
magnetic interaction between the two manganese(III) ions be-
1.4
1.2
1.0
0.8
µ
µ
0.6
χ
0.4
0.2
0.0
50
100
150
200
250
300
T / K
Fig. 8. Temperature dependence of magnetic susceptibility
and effective magnetic moment of [Mn2(O2CCH3)2-
(tbsaec)] (3). Solid line was drawn with the parameters
g ¼ 2:00, J ¼ þ0:53 cmꢂ1, ꢇ ¼ ꢂ2:3 K for Eq. 1.
cause of the long Mn Mn distance and the intervening saturat-
ꢁꢁꢁ
ed macrocyclic ring. Compared with the J values, the absolute
values of ꢇ values are definitely larger. These facts suggest that
a zero-field-splitting of isolated manganese(III) ion cannot be
excluded in the present cases. Thus, we analyzed the magnetic
data by using the following equations based on two isolated
S ¼ 2 ions with a zero-field-splitting as the first approxima-
tion:23,24
8
1.2
1.0
6
0.8
µ
4
0.6
µ
ꢃM ¼ 2ð2ꢃx þ ꢃzÞ=3;
ð2Þ
χ
0.4
with
2
0.2
ꢃx ¼ ðNg2ꢂB2=kTÞ½ð6kT=DÞð1 ꢂ expðꢂD=kTÞÞ
þ ð4kT=3DÞðexpðꢂD=kTÞ
0.0
0
0
50
100
150
200
250
300
ꢂ expðꢂ4D=kTÞÞꢅ=½1 þ 2 expðꢂD=kTÞ
þ 2 expðꢂ4D=kTÞꢅ;
T / K
ð3Þ
ð4Þ
Fig. 9. Temperature dependence of magnetic susceptibility
and effective magnetic moment of [Mn2(O2CCH3)2-
(tmsaec)] (8). Solid line was drawn with the parameters
g ¼ 2:00, D ¼ þ3:9 cmꢂ1 for Eq. 2.
and
ꢃz ¼ ðNg2ꢂB2=kTÞ½2 expðꢂD=kTÞ
þ 8 expðꢂ4D=kTÞꢅ=½1 þ 2 expðꢂD=kTÞ
þ 2 expðꢂ4D=kTÞꢅ;
1.0
0.8
0.6
0.4
0.2
0.0
8
6
4
2
0
where D is the zero-field-splitting parameter. As shown in
Fig. 9, this model reproduced the magnetic data satisfactorily
with the following parameters: g ¼ 2:02, D ¼ ꢂ2:1 cmꢂ1 (or
µ
µ
+2.3 cmꢂ1) for 1; g ¼ 1:93, D ¼ ꢂ1:0 cmꢂ1 (or +1.1 cmꢂ1
)
for 2; g ¼ 2:01, D ¼ ꢂ0:02 cmꢂ1 (or +0.02 cmꢂ1) for 3;
g ¼ 1:87, D ¼ ꢂ1:9 cmꢂ1 (or +2.0 cmꢂ1) for 4; g ¼ 1:96,
D ¼ ꢂ3:3 cmꢂ1 (or +3.7 cmꢂ1) for 5; g ¼ 1:88, D ¼ ꢂ2:7
cmꢂ1 (or +3.0 cmꢂ1) for 6; g ¼ 2:00, D ¼ ꢂ3:5 cmꢂ1 (or
χ
+3.9 cmꢂ1) for 8; g ¼ 1:91, D ¼ ꢂ1:4 cmꢂ1 (or +1.5 cmꢂ1
)
for 9. The D values are in the range of those found in high-spin
manganese(III) complexes (jDj ꢇ 8 cmꢂ1),25,26 although the
sign of D cannot be determined from the powder magnetic
susceptibility data. For 7 and 10, this model does not explain
the increase in the magnetic moments in the low-temperature
region, which is thought to be due to intermolecular interac-
tions. In order to describe the intermolecular interactions, a
molecular field approximation was introduced:24
0
50
100
150
200
250
300
T / K
Fig. 10. Temperature dependence of magnetic susceptibili-
ty and effective magnetic moment of [Mn2(N3)2(tnaec)]
(7). Solid line was drawn with the parameters g ¼ 1:91,
D ¼ ꢂ3:3 cmꢂ1, zJ ¼ þ0:17 cmꢂ1 for Eqs. 2–5.
ꢃM ¼ 2Ng2ꢂB2=kðT ꢂ ꢇÞꢅ½30 þ 14 expðꢂ8J=kTÞ
þ 5 expðꢂ14J=kTÞ
0
2
ꢃM ¼ ꢃM=ð1 ꢂ 2zJꢃM=Ng2ꢂB Þ:
ð5Þ
þ expðꢂ18J=kTÞꢅ=½9 þ 7 expðꢂ8J=kTÞ
þ 5 expðꢂ14J=kTÞ þ 3 expðꢂ18J=kTÞ
þ expðꢂ20J=kTÞꢅ;
Using Eqs. 2–5 the magnetic data of 7 and 10 were analyzed,
and the best-fit parameters were as follows (Fig. 10): g ¼ 1:91,
D ¼ ꢂ3:3 cmꢂ1
,
zJ ¼ þ0:17 cmꢂ1 (or g ¼ 1:90, D ¼
ð1Þ

356 Bull. Chem. Soc. Jpn. Vol. 81, No. 3 (2008)
Dinuclear Manganese(III) Complexes
þ6:1 cmꢂ1, zJ ¼ þ0:27 cmꢂ1) for 7; g ¼ 1:87, D ¼ ꢂ3:3
cmꢂ1, zJ ¼ þ0:17 cmꢂ1 (or g ¼ 1:86, D ¼ þ6:8 cmꢂ1, zJ ¼
þ0:29 cmꢂ1) for 10. The positive zJ values suggest a weak
ferromagnetic intermolecular interaction in these complexes.
5
a) B. Chiswell, E. D. McKenzie, L. F. Lindoy, in Compre-
hensive Coordination Chemistry, ed. by G. Wilkinson, R. D.
Gillard, J. A. McCleverty, Pergamon, Oxford, 1987, Vol. 4,
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Enzymes, ed. by V. L. Pecoraro, VCH, New York, 1992.
Conclusion
The new Schiff-base ligands, 1,4,8,11-tetrakis(salicylidene-
aminoethyl)-1,4,8,11-tetraazacyclotetradecane (H4tsaec) and
its substituent derivatives, were shown to be good ligands
for the synthesis of a series of manganese(III) complexes with
6
a) G. W. Brudvig, R. H. Crabtree, Prog. Inorg. Chem.
1989, 37, 99. b) R. Machanda, G. W. Brudvig, R. H. Crabtree,
Coord. Chem. Rev. 1995, 144, 1. c) A. J. Wu, J. E. Penner-Hahn,
V. L. Pecoraro, Chem. Rev. 2004, 104, 903.
well-separated dinuclear systems having a long Mn Mn
˚
distance of 9.676(4)–10.096(2) A, which show essentially no
ꢁꢁꢁ
7
a) T. Matsushita, H. Kono, T. Shono, Bull. Chem. Soc. Jpn.
magnetic interaction. This type of manganese complexes is
unique and involves an undeveloped region of the dinuclear
1981, 54, 2646. b) T. Matsushita, Y. Hirata, T. Shono, Bull. Chem.
Soc. Jpn. 1982, 55, 108. c) T. Matsushita, T. Shono, Polyhedron
1983, 2, 613. d) M. Fujiwara, T. Matsushita, T. Shono, Poly-
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T. Matsushita, Polyhedron 1997, 16, 3787. h) H. Torayama, T.
Nishide, H. Asada, M. Fujiwara, T. Matsushita, Polyhedron
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metal systems that have a nano-level metal metal separation,
although they do not seem to be model compounds for the
OEC of PS-II.
ꢁꢁꢁ
The present work was partially supported by the ‘‘Open
Research Center’’ Project for Private Universities: matching
fund subsidy and Grants-in-Aid for Scientific Research
Nos. 16550062 and 19550074 from the Ministry of Education,
Culture, Sports, Science and Technology.
8
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Bull. Chem. Soc. Jpn. 1994, 67, 3128. c) M. Mikuriya, K.
Matsunami, Mater. Sci. (Poland) 2005, 23, 773. d) M. Mikuriya,
R. Nukada, W. Tokii, Y. Hashimoto, T. Fujii, Bull. Chem. Soc.
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O4, FW: 1417.89, monoclinic, space group C2=c, a ¼ 28:283ð10Þ
ꢃ
˚
˚
˚
A, b ¼ 16:057ð6Þ A, c ¼ 18:875ð7Þ A, ꢅ ¼ 131:536ð6Þ , V ¼
3
ꢂ3
6416ð4Þ A , Z ¼ 4, Dcalcd ¼ 1:47 g cmꢂ3, Dm ¼ 1:45 g cm , crys-
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0:2107, Goodness-of-fit on F2 ¼ 0:983.
˚
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