Template synthesis of macrocyclic dinuclear CuII complexes and conversion into mononuclear complexes by site-selective copper elimination

Article abstract of DOI:10.1246/bcsj.74.495

The acyclic dinucleating ligand, N,N′-dimethyl-N,N′-trimethylenedi-(3-formyl-2-hydroxy-5- methylbenzylamine) (H₂L), has been prepared. It combines two Cu^II ions with its N(amine)₂O₂ and O₄ metal-binding sites to form a dinuclear complex [Cu₂(L)](ClO₄)₂. The [1:1] condensation of [Cu₂(L)](ClO₄)₂ with an aliphatic or aromatic diamine has provided macrocyclic dinuclear Cu^II complexes [Cu₂(Lⁱ)](ClO₄)₂ (Lⁱ = L¹ for the diamine = ethylenediamine, L² for trimethylenediamine, L³ for tetramethylenediamine, L⁴ for o-phenylenediamine and L⁵ for 1,8-diaminonaphthalene). X-ray crystallographic studies for [Cu₂(L¹)(H₂O)](ClO₄) ₂MeCN and [Cu₂(L⁵)](ClO₄)₂2MeOH demonstrate a macrocyclic dinuclear core structure with the two Cu^II ions in the N(amine)₂O₂ and N(imine)₂O₂ sites, in the Cu-Cu separation of ca. 3.0 A. The dinuclear complexes are studied in magnetic, electronic spectral and electrochemical properties. The treatment of the dinuclear complexes with Na₂S in acetonitrile resulted in the elimination of one Cu to afford the mononuclear complexes [Cu(Lⁱ)]xNaClO₄. The X-ray crystallography for [Cu(L²)], [Cu(L³)NaClO₄ and [Cu(L⁴)] has demonstrated that the Cu in the N(amine)₂O₂ site is selectively eliminated. In the latter complex, the Na¹ion is accommodated in the aminic site.

Full text of DOI:10.1246/bcsj.74.495

© 2001 The Chemical Society of Japan
495
Bull. Chem. Soc. Jpn., 74, 495–503 (2001)
Template Synthesis of Macrocyclic Dinuclear CuII Complexes and
Conversion into Mononuclear Complexes by Site-Selective Copper
Elimination
Akiko Hori, Masami Yonemura, Masaaki Ohba, and Hisashi Okawa*
Department of Chemistry, Faculty of Science, Kyushu University, Hakozaki 6-10-1, Higashiku, Fukuoka 812-8581
(Received October 10, 2000)
The acyclic dinucleating ligand, N,N′-dimethyl-N,N′-trimethylenedi-(3-formyl-2-hydroxy-5-methylbenzylamine)
(H2L), has been prepared. It combines two CuII ions with its N(amine)2O2 and O4 metal-binding sites to form a dinuclear
complex [Cu2(L)](ClO4)2. The [1:1] condensation of [Cu2(L)](ClO4)2 with an aliphatic or aromatic diamine has provided
macrocyclic dinuclear CuII complexes [Cu2(Li)](ClO4)2 (Li = L1 for the diamine = ethylenediamine, L2 for trimethylene-
diamine, L3 for tetramethylenediamine, L4 for o-phenylenediamine and L5 for 1,8-diaminonaphthalene). X-ray crystallo-
graphic studies for [Cu2(L1)(H2O)](ClO4)2•MeCN and [Cu2(L5)](ClO4)2•2MeOH demonstrate a macrocyclic dinuclear
core structure with the two CuII ions in the N(amine)2O2 and N(imine)2O2 sites, in the Cu−Cu separation of ca. 3.0 Å.
The dinuclear complexes are studied in magnetic, electronic spectral and electrochemical properties. The treatment of the
dinuclear complexes with Na2S in acetonitrile resulted in the elimination of one Cu to afford the mononuclear complexes
[Cu(Li)]•xNaClO4. The X-ray crystallography for [Cu(L2)], [Cu(L3)]•NaClO4 and [Cu(L4)] has demonstrated that the Cu
in the N(amine)2O2 site is selectively eliminated. In the latter complex, the NaI ion is accommodated in the aminic site.
The design of dinucleating compartmental ligands capable
of binding two metal ions in close proximity is important for
providing functional bimetallic molecules and for modeling bi-
metallic biosites.1,2 Phenol-based macrocyclic ligands of the
type in Scheme 1, having dissimilar N(amine)2O2 and N(imi-
ne)2O2 metal-binding sites sharing the bridging phenolic oxy-
gens, have been used for the study of heterodinuclear metal
complexes.2–6 The macrocyclic ligands are synthesized by two
steps; (i) the preparation of an acyclic proligand possessing
N(amine)2O2 and O(formyl)2O2 metal-binding sites and (ii) the
1:1 condensation of the proligand with a diamine by a template
reaction. The key step in this synthesis is the preparation of an
appropriate proligand. Previously we reported two macrocyclic
ligands of this type (X = Br, R = CH3, La = ethylene, Lb = ethyl-
ene or trimethylene),4,5 where the proligand N,N′-dimethyl-
N,N′-ethylenedi (5-bromo-3-formyl-2-hydroxybenzylamine)
was easily prepared by the Mannich reaction between 5-bro-
mosalicylaldehyde and N,N′-dimethylethylenediamine. This
synthetic method seemed to be applicable to analogous proli-
gands with different lateral chains between the amine nitro-
gens. In our attempt to prepare the proligand, N, N′-dime-
thyl-N,N′-trimethylenedi(5-bromo-3-formyl-2-hydroxybenzy-
lamine), however, the Mannich reaction between 5-bromosali-
cylaldehyde and N,N′-dimethyl-1,3-trimethylenediamine re-
sulted in the recovery of the starting materials in spite of our
many efforts. Thus, one needs to develop a new synthetic meth-
od of proligands for the macrocyclic ligands of the type in
Scheme 1.
This work relates to a new preparation of an acyclic proli-
gand, N,N′-dimethyl-N,N′-trimethylenedi(5-methyl-3-formyl-
2-hydroxybenzylamine) (abbreviated as H2L), by the reaction
between 3-chloromethyl-5-methylsalicylaldehyde and N,N′-
dimethyl-1,3-propanediamine, and the template cyclization
with an aliphatic or aromatic diamine to afford macrocyclic di-
nuclear CuII complexes [Cu2(Li)](ClO4)2 (Scheme 2). The ab-
breviations of the macrocyclic ligands are as follows: Li = L1
for Z = ethylene, L2 for trimethylene, L3 for tetramethylene, L4
for o-phenylene and L5 for 1,8-naphthalene. The structures of
[Cu2(L1)(H2O)](ClO4)2•MeCN and [Cu2(L5)](ClO4)2•2MeOH
are determined, and physicochemical properties of [Cu2(Li)]-
(ClO4)2 are investigated. The treatment of [Cu2(Li)](ClO4)2
with Na2S in acetonitrile gave [Cu(Li)]•xNaClO4. The site-se-
lective elimination of the Cu in the N(amine)2O2 site is report-
ed.
Scheme 1. General synthetic scheme of macrocyclic
complexes.

496 Bull. Chem. Soc. Jpn., 74, No. 3 (2001)
Macrocyclic Di- and Mononuclear CuII Complexes
(50 cm3), and the solution was stirred for 20 minutes. To this was
added a solution of copper(II) perchlorate hexahydrate (3.84 g,
10.4 mmol) in methanol (20 cm3), and the mixture was stirred at
room temperature for 2 hours to give green microcrystals. Yield:
6.76 g (90%). Found: C, 38.09; H, 4.21; N, 3.79; Cu, 17.9%. Calcd
for C23H28Cl2Cu2N2O12: C, 38.24; H, 3.91; N, 3.88; Cu, 17.6%.
µ
eff per Cu: 1.03 µB at 290 K. Selected IR data (ν/cm–1) using KBr
disk: 1612, 1561, 1117, 1082, 814, 621. UV-vis λ/nm (ε/M–1 cm–1)
in dmf: 374 (7900), 668 (180) (1 M = 1 mol dm–3).
Recrystallization from dmf formed [Cu2(L)(dmf)2](ClO4)2 as
green prisms suitable for X-ray crystallography.
[Cu2(L1)](ClO4)2 (1). To a solution of [Cu2(L)](ClO4)2 (500
mg, 0.69 mmol) in acetonitrile (100 cm3) was added ethylenedi-
amine (41 mg, 0.69 mmol), and the mixture was stirred for 10 hours
and concentrated to 20 cm3 to give greenish brown microcrystals.
Yield: 390 mg (76%). Found: C, 39.84; H, 4.48; N, 7.87; Cu,
16.7%. Calcd for C25H32Cl2Cu2N4O10: C, 40.22; H, 4.32; N, 7.50;
Cu, 17.0%. µeff per Cu: 0.85 µB at 290 K. Selected IR data (ν/cm–1)
using KBr disk: 2926, 1642, 1570, 1463, 1110, 1087, 804, 622.
UV-vis λ/nm (ε/M–1 cm–1) in dmf: 348 (9100), ca. 470(sh), 654
(145).
Scheme 2. Synthetic scheme for L1–L5 as dinuclear
CuII complexes and conversion into mononuclear com-
plexes.
Recrystallization from acetonitrile formed 1•H2O•MeCN as
good crystals suitable for X-ray crystallography.
[Cu2(L2)](ClO4)2 (2). To a solution of [Cu2(L)](ClO4)2 (500
mg, 0.69 mmol) in acetonitrile (100 cm3) was added trimethylene-
diamine (51 mg, 0.69 mmol), and the mixture was stirred for 10
hours to result in the precipitation of the mononuclear complex
[Cu(L2)] (2′, see below) as brown crystals (127 mg). The solution
separated from 2′ was concentrated to 20 cm3 and allowed to stand
overnight to give the dinuclear complex 2 as green microcrystals.
Yield: 240 mg (46%). Found: C, 40.84; H, 4.54; N, 7.36; Cu,
16.5%. Calcd for C26H34Cl2Cu2N4O10: C, 41.06; H, 4.51; N, 7.37;
Cu, 16.7%. µeff per Cu: 1.05 µB at 290 K. Selected IR data (ν/cm–1)
using KBr disk: 2927, 1636, 1575, 1468, 1098, 812, 620. UV-vis λ/
nm (ε/M–1 cm–1) in dmf: 346 (11200), 64 (190).
Experimental
Measurements. Elemental analyses of C, H and N were ob-
tained from the Service Center of Elemental Analysis at Kyushu
University. Analyses of Cu were obtained using a Shimadzu AA-
660 atomic absorption/flame emission spectrophotometer. Infrared
spectra were recorded on a Perkin Elmer BX FT-IR system using
KBr disks. Electronic spectra in N,N-dimethylformamide (dmf)
were recorded on a Shimadzu UV-3100PC spectrometer. Magnetic
susceptibilities were measured on a Faraday balance in the temper-
ature range of 78–300 K. The apparatus was calibrated using
[Ni(en)3]S2O3;7 diamagnetic corrections for the constituting atoms
were performed using Pascal’s constants.8 Cyclic voltammograms
were recorded on a BAS CV-50W electrochemical analyzer in dmf
or dichloromethane containing tetrabutylammonium perchlorate
(TBAP) as the supporting electrolyte (Caution! TBAP is explosive
and should be handled with great care). A three-electrode cell was
used which was equipped with a glassy carbon as the working elec-
trode, a platinum coil as the counter electrode, and a Ag/Ag+
(TBAP/acetonitrile) electrode as the reference.
[Cu2(L3)](ClO4)2 (3). This was obtained as dark green crys-
tals by the reaction of [Cu2(L)](ClO4)2 with tetramethylenedi-
amine. Yield: 60%. Found: 41.79; H, 4.79; N, 7.30; Cu, 16.6%.
Calcd for C27H36Cl2Cu2N4O10: C, 41.87; H, 4.68; N, 7.23; Cu,
16.4%. µeff per Cu: 0.72 µB at 290 K. Selected IR data (ν/cm–1) us-
ing KBr disk: 2944, 1626, 1573, 1467, 1093, 810, 601. UV-vis (λ/
nm (ε/M–1 cm–1) in dmf: 348 (11900), 646 (195), ca. 730 (100).
[Cu2(L4)](ClO4)2 (4). This was obtained as brown microcrys-
tals by the reaction of [Cu2(L)](ClO4)2 with o-phenylenediamine.
Yield: 73%. Found: 43.62; H, 4.21; N, 7.27; Cu, 15.9%. Calcd for
C29H32Cl2Cu2N4O10: C, 43.84; H, 4.06; N, 7.05; Cu, 16.0%. µeff per
Cu: 0.77 µB at 290 K. Selected IR data (ν/cm–1) using KBr disk:
3010, 1614, 1561, 1460, 1087, 807, 622. UV-vis λ/nm (ε/
M–1 cm–1) in dmf: 346 (10300), 375 (6900), 402 (6700), 560 (180),
656 (170).
Preparation. 3-Chloromethyl-5-methylsalicylaldehyde was
prepared by the literature methods.9,10 Other chemicals were pur-
chased from commercial sources and used without further purifica-
tion.
N,N′-Dimethyl-N,N′-trimethylenedi(3-formyl-2-hydroxy-5-
methylbenzylamine) (H2L). A solution of N,N′-dimethyl-1,3-
propanediamine (1.38 g, 13.5 mmol) and triethylamine (2.74 g, 27
mmol) in tetrahydrofuran (20 cm3) was dropwise added to a stirred
solution of 3-chloromethyl-5-methylsalicylaldehyde (5.0 g, 27
mmol) in tetrahydrofuran (20 cm3), and the mixture was refluxed
for 3 hours. The reaction mixture was diluted with water (50 cm3)
and shaken with three 50 cm3 portions of chloroform. The extracts
were combined, washed with water, and dried over MgSO4. Crude
H2L was obtained as an oily substance when the solvent was evap-
orated to dryness. It was used for the preparation of the following
complex without further purification.
[Cu2(L5)](ClO4)2 (5). This was obtained as brown microcrys-
tals by the reaction of [Cu2(L)](ClO4)2 with 1,8-diaminonaphtha-
lene.Yield: 83%. Found: 46.45; H, 4.26; N, 6.46; Cu, 14.8%. Calcd
for C33H33Cl2Cu2N4O10: C, 46.93; H, 3.94; N, 6.64; Cu, 15.1%. µeff
per Cu: 0.77 µB at 290 K. Selected IR data (ν/cm–1) using KBr disk:
1622, 1594, 1572, 1553, 1236, 1093, 829, 627. UV-vis λ/nm (ε/
M–1 cm–1) in dmf: 392 (10200), 656 (170), 680 (140).
It was recrystallized from a dmf-methanol mixture as 5•2MeOH
suitable for X-ray crystallography.
Conversion of Dinuclear Complexes (1–5) into Mononuclear
Complexes (1′–5′). Each of 1–5 (0.1 mmol) and Na2S•9H2O (0.1
mmol) were added to acetonitrile (30 cm3), and the mixture was
[Cu2(L)](ClO4)2. H2L (4.18 g, 10.0 mmol) and copper(II) ac-
etate monohydrate (2.12 g, 10.4 mmol) were dissolved in methanol

A. Hori et al.
Bull. Chem. Soc. Jpn., 74, No. 3 (2001) 497
stirred at ambient temperature for 1 hour. The resulting CuS was
separated by filtration, and the filtrate was diffused with 2-propanol
to give a crystalline product.
anode generator. Data collections of 1•H2O•MeCN were made on a
Rigaku AFC5S diffractometer. Cell constants and an orientation
matrix for the data collection were obtained from 25 reflections and
the ω-2θ scan technique was used for the intensity collections.
Pertinent crystallographic parameters are summarized in Table 1.
The intensities of the representative reflections were monitored
every 150 reflections and decay corrections were applied. An em-
pirical absorption correction based on azimuthal scans of several
reflections was applied. Reflection data were corrected for Lorentz
and polarization effects.
The structures were solved by the direct method and expanded
using the Fourier technique. Non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were included in structure factor
calculations but were not refined. In the case of 5•2MeOH, one of
the perchlorate ions and the two MeOH molecules were refined
isotropically because of positional disorder. The neutral atom scat-
tering factors were taken from Cromer and Waber.11 Anomalous
dispersion effects were included in Fcalcd; the values for ∆f ′ and
∆f ′′ were those of Creagh and McAuley.12 The values for the mass
attenuation coefficients are those of Creagh and Hubbel.13 All cal-
culations were performed using the teXsan14 crystallographic soft-
ware of Molecular Structure Corporation.
[Cu(L1)]•0.8NaClO4 (1′•0.8NaClO4). Brown-purple micro-
crystalline powder.Yield: 58%. Found: 51.64; H, 5.56; N, 9.52; Cu,
10.9%. Calcd for C25H32CuN4O2•0.8NaClO4 C, 51.59; H, 5.54; N,
9.63; Cu, 10.9%. µeff per Cu: 1.84 µB at 290 K. Selected IR data (ν/
cm–1) using KBr disk: 2786, 1627, 1571, 1097, 620.
[Cu(L2)] (2′). Brown microcrystals. Yield: 75%. Found: C,
62.78; H, 6.59; N, 11.15; Cu, 12.6%. Calcd for C26H34CuN4O2: C,
62.69; H, 6.88; N, 11.25; Cu, 12.8%. µeff per Cu: 1.92 µB at 290 K.
Selected IR data (ν/cm–1) using KBr disk: 2940, 2788, 2757, 1619,
1601, 1543, 1448. UV-vis λ/nm (ε/M–1 cm–1) in dmf: 388 (11100),
607 (316).
It was recrystallized from a dmf-methanol mixture as single
crystals suitable for X-ray crystallography.
[Cu(L3)]•NaClO4 (3′•NaClO4). Dark green microcrystals.
Yield: 85%. Found: 51.49; H, 5.71; N, 9.02; Cu, 10.2%. Calcd for
C27H36ClCuN4NaO6: C, 51.10; H, 5.72; N, 8.83; Cu, 10.0%.
FABMS: m/z 534.4 for {NaCu(L3)}+. µeff per Cu: 1.93 µB at 290 K.
Selected IR data (ν/cm–1) using KBr disk: 2926, 2798, 1623, 1601,
1095, 1063, 621. UV-vis λ/nm (ε/M–1 cm–1) in dmf: 380 (9300),
600 (250).
Crystallographic data have been deposited at the CCDC, 12
Union Road, Cambridge CB2 1EZ, UK and copies can be obtained
on request, free of charge, by quoting the publication citation and
deposition numbers CCDC 154024–154027. The data are also de-
posited as Document No. 74021 at the Office of the Editor of Bull.
Chem. Soc. Jpn.
[Cu(L4)] (4′). Reddish brown microcrystals. Yield: 77%.
Found: 65.18; H, 6.06; N, 10.52; Cu, 12.0%. Calcd for
C29H32CuN4O2: C, 65.46; H, 6.06; N, 10.53; Cu, 11.9%. µeff per
Cu: 1.85 µB at 300 K. Selected IR data (ν/cm–1) using KBr disk:
2920, 2788, 1618, 1601. UV-vis λ/nm (ε/M–1 cm–1) in dmf: 313
(27000), 446 (21600), 590 (410).
Results and Discussion
[Cu(L5)]•2.1NaClO4 (5′•2.1NaClO4). Brown microcrystal-
line powder. Yield: 72%. Found: C, 47.07; H, 4.43; N, 6.79; Cu,
8.1%. Calcd for C33H34CuN4O2•2.1NaClO4: C, 47.22; H, 4.08; N,
6.68; Cu, 7.6%. µeff per Cu: 1.93 µB at 300 K. Selected IR data (ν/
cm–1) using KBr disk: 1622, 1581, 1549, 1539, 1227, 1093, 762,
624. UV-vis λ/nm (ε/M–1 cm–1) in dmf: 404 (28000).
X-Ray Crystallography. Crystallographic measurements for
[Cu2(L)(dmf)2](ClO4)2, 5•2MeOH, 2′, 3′•NaClO4 and 4′ were
made on a Rigaku AFC7R diffractometer using graphite-mono-
chromated MoKα radiation (λ = 0.71069 Å) and a 12 kW rotating
Precursor Complex [Cu2(L)](ClO4)2. Preparation. In
our previous work the proligand N,N′-dimethyl-N,N′-ethyl-
enedi(5-bromo-3-formyl-2-hydroxybenzylamine) formed
a
mononuclear CuII complex with the metal in the N(amine)2O2
site.5a The cyclization of the Cu complex with ethylenediamine
or 1,3-trimethylenediamine afforded the macrocyclic CuII
complexes, and a similar cyclization reaction in the presence of
PbII afforded the macrocyclic PbIICuII complexes. Both the
Table 1. Crystal Parameters
[Cu2(L)(dmf)2](ClO4)
1•H2O•MeCN
5•2MeOH
2ꢀ
3ꢀ•NaClO4
4ꢀ
Formula
Formula weight
Crystal system
Space group
a/Å
C29H42N4Cl2Cu2O14 C27H37N5Cl2Cu2O11 C34H38N4Cl2Cu2O11 C26H34N4CuO2 C27H36N4ClCuNaO6 C29H32N4CuO2
868.67
orthorhombic
P212121(#19)
18.338(10)
20.407(7)
9.954(2)
90
805.61
triclinic
P1(#2)
876.69
orthorhombic
Pbcn (#60)
20.805(5)
23.863(8)
15.122(2)
90
498.13
monoclinic
C2/c (#15)
19.885(5)
14.262(5)
9.451(4)
90
115.00(2)
90
2429(1)
8
634.59
monoclinic
P21/c(#14)
12.778(3)
13.100(4)
17.352(4)
90
97.198(2)
90
2881(1)
4
532.14
monoclinic
P21/c(#14)
8.371(3)
15.026(3)
19.854(2)
90
93.26(2)
90
2493(1)
4
10.682(2)
16.427(4)
10.082(2)
98.30(2)
104.56(1)
103.60(2)
1624.9(6)
2
b/Å
c/Å
α/◦
β/◦
90
90
3724(2)
4
90
90
7507(2)
4
γ /◦
V/Å−3
Z value
Dc/g cm−3
µ(MoKα)/cm−1
No. observations
(I > 3.00σ(I))
R
1.549
l.646
1.551
1.362
1.463
1.418
13.54
15.39
13.39
9.29
9.13
9.11
2474
0.048
0.056
3346
0.042
0.038
3882
0.066
0.090
1720
0.041
0.046
4543
0.049
0.075
2984
0.043
0.043
RW

498 Bull. Chem. Soc. Jpn., 74, No. 3 (2001)
Macrocyclic Di- and Mononuclear CuII Complexes
macrocyclic CuII and PbIICuII complexes could be used as pre-
cursors for the transition metal dinuclear MIICuII complexes.5
In this work the new proligand N,N′-dimethyl-N,N′-trimethyl-
enedi(5-methyl-3-formyl-2-hydroxybenzylamine) (H2L) al-
ways formed dinuclear [Cu2(L)](ClO4)2 even when syntheses
were attempted in the stoichiometry of H2L/CuII = 1/1. The cy-
clization of the proligand complex [Cu2(L)](ClO4)2 with di-
amines formed the macrocyclic dinuclear CuII complexes (1–5)
in a good or tolerable yield.
range of 1.991(6)–2.028(8) Å. The axial Cu1–O5(dmf) bond
distance is 2.196(6) Å; this is elongated owing to the
Jahn–Teller effect. The Cu1 is displaced by 0.160 Å from the
basal N2O2 least-squares plane towards O5. The two methyl
groups (C10 and C14) attached to the nitrogens are situated cis
to each other with respect to the mean {CuN2O2} plane. The
trimethylene chain combining the two amino nitrogens as-
sumes the usual chair conformation.
The Cu2 in the O4 site also has a square-pyramidal geometry
together with a dmf oxygen (O6) at the axial site. The basal
bond distances range from 1.909(7) to 1.932(6) Å. The axial
Cu2–O6 bond distance is elongated (2.248(8) Å). The dis-
placement of Cu2 from the basal least-squares plane towards
O6 is 0.151 Å. The dmf molecule bound to Cu1 and that bound
to Cu2 are situated cis with respect to the mean molecular
plane.
Crystal Structure. An ORTEP15 view of the dmf adduct,
[Cu2(L)(dmf)2](ClO4)2, is shown in Fig. 1 together with the
numbering scheme. Selected bond distances and angles are
summarized in Table 2.
The dinegative L2– accommodates two CuII ions in its N2O2
and O4 sites in the Cu−Cu separation of 3.040(2) Å. The geom-
etry about Cu1 in the N2O2 site is a square-pyramid with a dmf
oxygen at the axial site. The basal bond distances fall in the
The basal least-squares plane for Cu1 and that for Cu2 are
bent at the O2–O3 edge with a dihedral angle of 21.03°. Fur-
thermore, the molecule shows a bend at the Cu1–Cu2 edge,
providing a saddle-like shape for the molecule. The dihedral
angle defined by the two aromatic rings is 15.87°.
Properties. [Cu2(L)](ClO4)2 shows the ν(C=O) vibration
of the formyl group at 1610 cm–1. The low frequency of the
band is in harmony with the coordination of the formyl oxygen
to the Cu.16 The ν3 mode of perchlorate group is split into two
(1117 and 1082 cm–1), suggesting the coordinative interaction
of the perchlorate group.17 The perchlorate groups must be
bonded to the axial site of the two CuII ions, instead of the dmf
ligands of [Cu2(L)(dmf)2](ClO4)2. In fact, [Cu2(L)(dmf)2]-
(ClO4)2 shows a perchlorate ν3 vibration at 1100 cm–1. Elec-
tronic absorption spectrum of [Cu2(L)](ClO4)2 in dmf has an
intense band at 374 nm and a weak band at 668 nm. The
former is assigned to an intraligand transition and the latter
band to a superposition of the d–d transitions of the two CuII
ions. The magnetic moment at room temperature is 1.03 µB per
Cu, and the moment decreased with decreasing temperature to
0.29 µB at liquid nitrogen temperature due to an antiferromag-
netic interaction between the two CuII ions. The magnetic sim-
ulation of this complex is discussed later, together with the di-
nuclear complexes 1–5.
Fig. 1. An ORTEP view for [Cu2(L)(dmf)2](ClO4)2 with
the atom numbering scheme.
Table 2. Selected Bond Distances and Angles for
[Cu2(L)(dmf)2](ClO4)2
Bond Distances (Å)
Cu(1) O(1)
Cu(1) O(5)
Cu(1) N(2)
Cu(2) O(1)
Cu(2) O(3)
Cu(2) O(6)
2.023(6)
2.196(6)
2.028(8)
1.918(6)
1.915(7)
2.248(8)
Cu(1) O(2)
Cu(1) N(1)
1.991(6)
2.024(8)
Macrocyclic Dinuclear Complexes. Crystal Structures.
An ORTEP drawing of [Cu2(L1)(H2O)](ClO4)2•MeCN
(1•H2O•MeCN) is shown in Fig. 2 together with the atom num-
bering scheme. Relevant bond distances and angles are sum-
marized in Table 3.
Cu(2) O(2)
Cu(2) O(4)
1.932(6)
1.909(7)
Cu(1)· · · Cu(2) 3.040(2)
The crystal is comprised of the macrocycle (L1)2–, two Cu
ions and one water molecule: two perchlorate ions and one
MeCN molecule are free from coordination and captured in the
crystal lattice. The Cu1 in the N(amine)2O2 site (aminic site)
has a square-pyramidal geometry together with the aqua oxy-
gen O3 at the axial site. The basal bond distances range from
1.997(4) to 2.012(4) Å. The axial Cu1–O3 bond is short
(2.304(4) Å). The deviation of the Cu from the basal least-
squares plane toward O3 is 0.211 Å. The Cu2 in the N(imi-
ne)2O2 site (iminic site) has a planar geometry with the short
bond distances of 1.898(4)–1.914(4) Å.
Bond Angles (◦)
O(1) Cu(1) O(2) 76.3(2)
O(1) Cu(1) N(1) 91.5(3)
O(2) Cu(1) O(5) 96.1(3)
O(2) Cu(1) N(2) 91.9(3)
O(5) Cu(1) N(2) 90.4(3)
O(1) Cu(2) O(2) 80.2(2)
O(1) Cu(2) O(4) 95.2(3)
O(2) Cu(2) O(3) 96.2(3)
O(2) Cu(2) O(6) 94.4(3)
O(3) Cu(2) O(6) 92.2(3)
O(1) Cu(1) O(5) 98.2(3)
O(1) Cu(1) N(2) 166.1(3)
O(2) Cu(1) N(1) 165.0(3)
O(5) Cu(1) N(1) 94.3(3)
N(1) Cu(1) N(2) 98.8(3)
O(1) Cu(2) O(3) 170.8(3)
O(1) Cu(2) O(6) 96.5(3)
O(2) Cu(2) O(4) 170.0(3)
O(3) Cu(2) O(4) 87.0(3)
O(4) Cu(2) O(6) 95.1(3)

A. Hori et al.
Bull. Chem. Soc. Jpn., 74, No. 3 (2001) 499
Fig. 2. An ORTEP view for [Cu2(L1)(H2O)](ClO4)2•MeCN
(1•H2O•MeCN) with the atom numbering scheme.
Fig. 3. An ORTEP view for [Cu2(L5)](ClO4)2 •2MeOH
Table 3. Selected Bond Distances and Angles for
(5•2MeOH) with the atom numbering scheme.
1•H2O•MeCN
Bond Distances (Å)
Table 4. Selected Bond Distances and Angles for 5•2MeOH
Bond Distances (Å)
Cu(1) O(1)
Cu(1) O(3)
Cu(1) N(2)
Cu(2) O(1)
Cu(2) N(3)
Cu(1)· · · Cu(2)
1.997(4)
2.304(4)
2.010(4)
1.914(4)
1.900(5)
2.989(1)
Cu(1) O(2)
Cu(1) N(1)
2.005(3)
2.012(4)
Cu(1) O(1)
Cu(1) N(1)
Cu(2) O(1)
Cu(2) N(3)
Cu(1)· · · Cu(2)
1.980(6)
1.994(7)
1.937(6)
1.933(7)
3.060(2)
Cu(1) O(2)
Cu(1) N(2)
Cu(2) O(2)
Cu(2) N(4)
1.968(6)
1.994(8)
1.942(6)
1.943(7)
Cu(2) O(2)
Cu(2) N(4)
1.898(4)
1.902(5)
Bond Angles (◦)
O(1) Cu(1) O(2) 76.6(1)
O(1) Cu(1) N(1) 90.7(2)
O(2) Cu(1) O(3) 96.3(2)
O(2) Cu(1) N(2) 90.7(2)
O(3) Cu(1) N(2) 96.6(2)
O(1) Cu(2) O(2) 81.2(1)
O(1) Cu(2) N(4) 96.4(2)
O(2) Cu(2) N(4) 177.5(2)
O(1) Cu(1) O(3) 94.7(1)
O(1) Cu(1) N(2) 163.9(2)
O(2) Cu(1) N(1) 162.8(2)
O(3) Cu(1) N(1) 96.3(2)
N(1) Cu(1) N(2) 99.4(2)
O(1) Cu(2) N(3) 177.3(2)
O(2) Cu(2) N(3) 96.3(2)
N(3) Cu(2) N(4) 86.1(2)
Bond Angles (◦)
O(1) Cu(1) O(2) 75.4(2)
O(1) Cu(1) N(2) 165.0(3)
O(2) Cu(1) N(2) 90.1(3)
O(1) Cu(2) O(2) 76.9(2)
O(1) Cu(2) N(4) 96.5(3)
O(2) Cu(2) N(4) 167.9(3)
O(1) Cu(1) N(1) 92.7(3)
O(2) Cu(1) N(1) 163.1(3)
N(1) Cu(1) N(2) 100.7(3)
O(1) Cu(2) N(3) 168.4(3)
O(2) Cu(2) N(3) 93.0(3)
N(3) Cu(2) N(4) 94.4(3)
The two methyl groups attached to the nitrogens are cis to
each other. The water molecule at the axial site of Cu1 is situat-
ed trans to the N-methyl groups with respect to the mean mo-
lecular plane. The Cu1–Cu2 interatomic separation is 2.989(1)
Å.
tween the hydrogen on C22 (C33) and that on C24 (C29). The
Cu−Cu interatomic separation is 3.060(2) Å.
Physicochemical Properties. Complexes 1−5 each has a
subnormal magnetic moment at room temperature. The µeff vs.
T curves for 1 in the temperature range of 78–300 K are given
in Fig. 4(A). The magnetic moment per Cu is 0.85 µB at room
temperature and the moment decreased with decreasing tem-
perature to 0.25 µB at liquid nitrogen temperature. The result
indicates the operation of antiferromagnetic interaction within
the molecule.
An ORTEP view for [Cu2(L5)](ClO4)2•2MeOH (5•2MeOH)
is shown in Fig. 3 together with the atom numbering scheme.
Relevant bond distances and angles are summarized in Table 4.
The crystal consists of the macrocycle (L5)2– and two CuII
ions; two perchlorate ions and two methanol molecules are free
from coordination. The Cu1 in the aminic site assumes a nearly
planar geometry with the Cu-to-donor bond distances of
1.968(6)–1.994(8) Å. The two methyl groups attached to the
nitrogens N1 and N2 are situated cis to each other.
The geometry about Cu2 in the iminic site shows a large dis-
tortion to tetrahedron; the dihedral angle between the least-
squares plane defined by Cu2, O1 and N4 and the least-squares
plane defined by Cu2, O2 and N3 is 10.63°. The naphthalene
ring is bent by 33.13 and 48.47° against the phenolic rings.
This distortion about Cu2 arises from the steric repulsion be-
The cryomagnetic property of 1 was simulated by means of
Bleaney–Bowers equation,18
χA = (1 − ρ){Ng2β2/kT}[exp (−2J/kT) + 3]−1
+ρ{Ng2β2/4kT} + Nα
(1)
where ρ is the fraction of monomeric CuII impurity and other
symbols have their usual meanings. A good simulation was ob-
tained using the magnetic parameters J = –310 cm–1, g = 2.05,
Nα = 70 × 10–6 cm3 mol–1 and ρ = 0.015, as indicated by the
solid curve (A) in Fig. 4. The trace (B) is the best-fit for

500 Bull. Chem. Soc. Jpn., 74, No. 3 (2001)
Macrocyclic Di- and Mononuclear CuII Complexes
Fig. 4. Temperature-dependences of magnetic moment
for (A) [Cu2(L1)](ClO4)2 (1) and (B) [Cu2(L)](ClO4)2.
[Cu2(L)](ClO4)2 using the parameters of J = –252 cm–1, g =
2.10, Nα = 60 × 10–6 cm3 mol–1 and ρ = 0.015.
Similarly, the cyomagnetic properties of 2–5 can be repro-
duced by the Bleaney-Bowers equation using the magnetic pa-
rameters: J = –270 cm–1, g = 2.10, Nα = 60 × 10–6 cm3 mol–1
and ρ = 0.050 for 2, J = –354 cm–1, g = 2.10, Nα = 60 × 10–6
cm3 mol–1 and ρ = 0.005 for 3, J = –337 cm–1, g = 2.10, Nα = 60
× 10–6 cm3 mol–1 and ρ = 0.014 for 4, and J = –340 cm–1, g =
2.05, Nα = 100 × 10–6 cm3 mol–1 and ρ = 0.020 for 5. The re-
sults demonstrate a fairly strong antiferromagnetic interaction
for 1–5 and for their precursor [Cu2(L)](ClO4)2 as well.
Fig. 5. Cyclic voltammograms of 1 5. Conditions:
in dmf solution containing TBAP (1 × 10−1 M), V
vs. Ag/Ag+ (TBAP/CH3CN), scan rate 50 mV s−1,
glassy carbon electrode, Pt counter electrode.
Electronic spectra of 1–5 were measured in dmf in the range
of 300–900 nm. The numerical data are given in the Experi-
mental Section. Complexes 1–3 show an intense band around
cyclic voltammetry. All the complexes show two reversible or
quasi-reversible couples in negative potential (see Fig. 5). We
have confirmed that the CuIIMII complexes (M = Mn, Co, Ni,
Cu, Zn) with an analogous ligand (Scheme 1: X = Br, R = CH3,
La = ethylene and Lb = trimethylene) show the CuII/CuI process
at the aminic site at –0.69 0.10 V vs. Ag+/Ag (in DMSO)5b
whereas the corresponding MIICuII complexes show the CuII/
CuI process at the iminic site at lower potential (–0.96 0.04V
vs. Ag+/Ag, in DMSO).5c This means that the aminic site is
more flexible than the iminic site and is adaptable to a geomet-
rical change on going from CuII to CuI.22 Thus, the first couple
appearing at practically the same potential for 1–5 (–0.62
0.05 V vs. Ag+/Ag) is attributable to the CuII/CuI process in the
aminic site and the second couple to the CuII/CuI process in the
iminic site. The second reduction potential increases in the or-
der: 1 (–1.25 V) < 2 (–1.06 V) < 3 (–0.91 V) and 4 (–1.14 V) <
5 (–0.98 V). The trends are in accord with an increasing tetra-
hedral distortion about the metal in the iminic site.22
∗
346−348 nm attributable to the π-π transition associated with
the azomethine linkage.19,20 The ultraviolet spectral feature of 4
is complicated because of the conjugation of the azomethine
group with the o-phenylene bridge and the spectra show three
∗
absorption bands at 346, 375 and 402 nm. The π-π transition
band for 5 is seen at a longer wavelength (392 nm), probably
due to the distortion of the azomethine linkage (see Fig. 3).
In the visible region, 1–5 generally show two absorption
bands due to the two non-equivalent CuII ions: ca. 470 and 654
nm for 1, 646 and ca. 730 nm for 3, 560 and 656 nm for 4, and
656 and ca. 680 nm for 5. One exception is 2 that shows one
absorption band centered around 642 nm. This must be a super-
position of two bands at similar wavelengths. One absorption
band near 650 nm, commonly observed 1–5, can be ascribed to
the CuII in the aminic site. Another band appearing at different
wavelengths for 1–5 may arise from the CuII in the iminic
site.21 It is evident that the d–d band maximum for the CuII in
the iminic site shifts to longer wavelength in the order: 1 (ca.
470 nm) < 2 (ca. 640 nm) < 3 (ca. 730 nm); 4 (560 nm) < 5 (ca.
680 nm). This is in accord with an increasing order in tetrahe-
dral distortion about the metal.21
Macrocyclic Mononuculear Complexes. Preparation
and General Characterization. For our object to develop
heterodinuclear metal complexes using the macrocyclic
ligands L1–L5, it is important to obtain mononuclear complexes
that have a metal in either the aminic or iminic site. In this work
Electrochemical properties of 1–5 were studied by means of

A. Hori et al.
Bull. Chem. Soc. Jpn., 74, No. 3 (2001) 501
we attempted to convert the dinuclear complexes into mononu-
clear complexes by the demetallation of one Cu ion. Eventually
we succeeded in obtaining [Cu(Li)]•xNaClO4 by the treatment
of 1–5 with Na2S in acetonitrile: [Cu(L1)]•0.8NaClO4
(1′•0.8NaClO4), [Cu(L2)] (2′), [Cu(L3)]•NaClO4 (3′•NaClO4),
[Cu(L4)] (4′) and [Cu(L5)]•2.1NaClO4 (5′•2.1NaClO4). The IR
spectra of 1′•0.8NaClO4 and 5′•2.1NaClO4 each has an intense
band at 1100 cm–1 typical of NaClO4.23 Evidently, 1′ and 5′ are
contaminated by NaClO4. On the other hand, 3′•NaClO4 shows
a split of the ν3 perchlorate vibration into two (1095, 1063
cm–1). Furthermore, the FAB mass spectrum of 3′•NaClO4 has
a prominent ion peak at m/z 534.4 that corresponds to
{NaCu(L3)}+. The results suggest that the NaI is accommodat-
ed in the aminic site with the coordination of the perchlorate
ion. This has been demonstrated by X-ray crystallographic
studies as discussed later.
Fig. 7. An ORTEP view for [Cu(L3)]•NaClO4 (3ꢀ) with
the atom numbering scheme.
The visible spectrum of 2′ in dmf has a d–d maximum at 607
nm that is compared to that for N,N′-trimethylenedisalicyli-
deneaminatocopper(II) (602 nm in nujol mull21 and 605 nm in
acetonitrile24). Similarly, the d-d band maximum of 4′ (590
nm) is compared to that for N,N′-o-phenylene-disalicylidene-
aminatocopper(II).20 The spectral results for 2′ and 4′ add a
support to the suggestion that the Cu exists in the iminic site in
each complex. That is, the Cu in the aminic site is eliminated
by the treatment with Na2S.
Crystal Structures. The X-ray crystallographic studies
have been made for [Cu(L2)] (2′), [Cu(L3)]•NaClO4
(3′•NaClO4) and [Cu(L4)] (4′) to specify the site to which the
CuII is bound. ORTEP drawings of 2′, 3′•NaClO4 and 4′ are
shown in Figs. 6, 7 and 8, respectively, and the selected bond
distances and angles of the complexes are given in Tables 5, 6
and 7, respectively.
The X-ray crystallography for 2′ unambiguously demon-
strates that the CuII in the aminic site is eliminated (Fig. 6). The
Cu existing in the iminic site has a pseudo tetrahedral geome-
Fig. 8. An ORTEP view for [Cu(L4)] (4ꢀ) with the atom
numbering scheme.
Table 5. Selected Bond Distances and Angels for 2ꢀ
Bond Distances (Å)
Cu O(1)
1.906(2)
Cu N(2)
1.960(3)
Bond Angels (◦)
O(1) Cu O(1)a)
86.1(1)
O(1) Cu N(2) 93.0(1)
N(1) Cu N(2)a) 97.2(2)
O(1) Cu N(2)a) 156.1(1)
a) Symmetry operation (2-x, y, 3/2-z).
try; the dihedral angle between the least-squares plane defined
*
*
by Cu, O1 and N2 and the plane defined by Cu, O1 and N2 is
32.17°. This distortion is compared to that found for analogous
[Cu(L2;3)] (dihedral angle: 35.56°).6 The two methyl groups at-
Fig. 6. An ORTEP view for [Cu(L2)] (2ꢀ) with the atom
numbering scheme.

502 Bull. Chem. Soc. Jpn., 74, No. 3 (2001)
Macrocyclic Di- and Mononuclear CuII Complexes
complexes of the macrocyclic ligands (L1–L5), [Cu2(Li)]-
(ClO4)2 (Li = L1 with ethylenediamine) (1), L2 with trimethyl-
enediamine (2), L3 with tetramethylenediamine (3), L4 with o-
phenylenediamine (4) and L5 with 1,8-naphthalenediamine
(5)). The two CuII ions are bound to the N(amine)2O2 and
N(imine)2O2 sites of each macrocycle, bridged by the two phe-
nolic oxygens. A strong antiferromagnetic interaction occurs
between the two metal ions. The d–d band maximum of the Cu
in the iminic site shifts in the order: 1 (ca. 470 nm) < 2 (ca. 640
nm) < 3 (ca. 730 nm) and 4 (560 nm) < 5 (ca. 680 nm). Similar-
ly, the CuII/CuI reduction potential due to the Cu in the iminic
site shifts in the order: 1 (–1.25 V) < 2 (–1.06 V) < 3 (–0.91 V)
and 4 (–1.14 V) < 5 (–0.98 V). The trends are in accord with an
increasing order in tetrahedral distortion about the metal. The
d–d band maximum and the CuII/CuI reduction potential of the
CuII in the aminic site were invariant among the complexes.
The dinuclear complexes were converted into mononuclear
complexes, [Cu(Li)]•xNaClO4, when treated with Na2S in ace-
tonitrile. The selective demetallation of the CuII in the aminic
site is demonstrated based on X-ray crystallographic studies.
The mononuclear CuII complexes can be precursors for het-
erodinuclear CuIIMII complexes. Studies in this line are under
way in our laboratory.
Table 6. Selected Bond Distances and Angles for 3ꢀ•NaClO4
Bond Distances (Å)
Cu O(1)
Cu N(3)
Na O(1)
Na O(3)
Na N(1)
Cu(1)· · · Na
1.920(2)
1.949(3)
2.270(3)
2.615(4)
2.548(3)
3.040(2)
Cu O(2)
Cu N(4)
Na O(2)
Na O(5)
Na N(2)
1.893(3)
1.962(3)
2.296(3)
2.575(4)
2.405(4)
Bond Angles (◦)
O(1) Cu O(2)
O(1) Cu N(4)
O(2) Cu N(4)
87.8(1)
93.8(1)
148.7(1)
O(1) Cu N(3) 146.3(1)
O(2) Cu N(3) 93.4(1)
N(3) Cu N(4) 102.0(1)
Table 7. Selected Bond Distances and Angles for 4ꢀ
Bond Distances (Å)
Cu O(1)
Cu N(3)
l.901(3)
l.955(3)
Cu O(2)
Cu N(4)
1.915(3)
1.948(3)
Bond Angles (◦)
O(1) Cu O(2)
O(1) Cu N(4)
O(2) Cu N(4)
89.4(1)
93.5(1)
176.6(1)
O(1) Cu N(3) 176.2(1)
O(2) Cu N(3) 93.5(1)
N(3) Cu N(4) 83.5(1)
This work was supported by Scientific Research on Priority
Area “Metal-assembled Complexes” (No. 10149106) and an
International Scientific Research Program (No. 09044093)
from the Ministry of Education, Science and Culture. The au-
thors thank Mr. Naoki Usuki and Mr. Keisuke Arimura in our
laboratory for their help in magnetic analyses.
tached to the nitrogens are situated trans to each other with re-
spect to the mean N(amine)2O2 plane. The trimethylene chain
combining the imino nitrogens (N2 and N2 ) adopts a de-
formed conformation. Such conformational features in the va-
cant aminic site may arise from a strain within the macrocyclic
framework.
∗
The X-ray crystallography for 3′•NaClO4 demonstrates that
the Cu in the aminic site is eliminated and the NaI ion is accom-
modated in this site (Fig. 7). The NaI has a distorted six-coordi-
nate environment together with a chelating perchlorate group.
The Na-to-donor bond distances range from 2.270(3) to
2.615(4) Å. The two methyl groups attached to the amine nitro-
gens are situated trans to each other with respect to the mean
N(amine)2O2 plane. The geometry about the Cu in the iminic
site is significantly distorted to tetrahedron: the dihedral angle
between the plane defined by Cu, O1 and N4 and the plane de-
fined by Cu, O2 and N3 is 43.80°. The Cu–Na interatomic dis-
tance is 3.040(2) Å. It appears that the aminic site of 3′ has a
flexibility for accommodating NaI owing to the elongation in
the lateral chain in the iminic site.
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