Syntheses, structures and photoluminescence properties of Ag(I), Cu(II), Zn(II) and Mn(II) complexes with N,N′-bis(3-pyridylmethyl)-1,4-benzene-dimethyleneimine

Article abstract of DOI:10.1246/bcsj.76.761

Four novel coordination complexes, [Ag(bpb)] NO3 · 2H₂O (1), [Cu₂(CH₃COO)₄(bpb)] (2), [ZnCl₂(bpb)₂] (3) and [MnCl₂(bpb)₂] (4) [bpb = N,N′-bis(3-pyridylmethyl)-1,4-benzenedimethyleneimine], with one-dimensional chain structures were synthesized and their structures were determined by X-ray crystallography. A structure analysis revealed that the bpb acts as a bridging ligand using two pyridyl N atoms to link two metal atoms, while the two imine N atoms do not participate in the coordination with the metal atoms. The photoluminescence properties of the title complexes were also studied. Although Cu(II) (2) and Zn(II) (3) complexes show intense violet-blue photoluminescence, no clear' photoluminescence was observed for the Ag(I) (1) and Mn(II) (4) complexes.

Full text of DOI:10.1246/bcsj.76.761

Ó 2003 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 76, 761–767 (2003)
761
Syntheses, Structures and Photoluminescence Properties of Ag(a), Cu(b),
Zn(b) and Mn(b) Complexes with N,N0-Bis(3-pyridylmethyl)-1,4-benzene-
dimethyleneimine
ꢀ
Hui-Fang Zhu, Ling Li, Taka-aki Okamura,y Wei Zhao, Wei-Yin Sun, and Norikazu Ueyamay
Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, Nanjing University,
Nanjing 210093, China
yDepartment of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043
(Received August 20, 2002)
Four novel coordination complexes, [Ag(bpb)]NO3 2H2O (1), [Cu2(CH3COO)4(bpb)] (2), [ZnCl2(bpb)2] (3) and
ꢁ
[MnCl2(bpb)2] (4) [bpb = N,N0-bis(3-pyridylmethyl)-1,4-benzenedimethyleneimine], with one-dimensional chain structures
weresynthesizedandtheirstructuresweredeterminedbyX-raycrystallography. Astructureanalysisrevealedthatthebpbacts
as a bridging ligand using two pyridyl N atoms to link two metal atoms, while the two imine N atoms do not participate in the
coordination with the metal atoms. The photoluminescence properties of the title complexes were also studied. Although
Cu(b) (2) and Zn(b) (3) complexes show intenseviolet-blue photoluminescence, no clear photoluminescencewas observedfor
the Ag(a) (1) and Mn(b) (4) complexes.
Supramolecular chemistry is at the forefront of modern
chemistry and recent years have witnessed a growing number of
supramolecular systems which incorporate metal atoms as
assembling and organizing centers.1 Control of the molecular
structure and topology isone ofthe major goals insupramolecular
chemistry.2;3 The self-assembly of these molecules is greatly
influenced by such factors as the solvent,4 template,5 solution
pH,6 geometric requirements of metal ions and counter ions.7
Thus employing transition metal ions and appropriate bridging
organic ligands has become a dominant theme in the construction
of supramolecular arrays.8;9 Recently, coordination polymers of
one- (1D), two- (2D) and three-dimensional (3D) infinite frame-
works have been extensively studied. Infinite metal-organic
frameworks are often assembled through the metal coordination
of pyridone- or pyridine-based bridging ligands.10{12 For
example, the treatment of 1,4-bis(4-pyridylmethyl)-2,3,5,6-tetra-
fluorobenzene (L) with Cd(NO3)2 generates a 1D chain with a
backbone composed of a cyclic linkage with the stoichiometry of
ML2.12
demonstrated that the flexible didentate and bridging ligand L1
gave 1D or 2D frameworks, depending on the metal ions and the
counter anions, and the rigidity of organic ligandhas a great effect
on the construction of supramolecular frameworks. In order to
further probe the influence of organic ligands on the formation of
assemblies, we designed and synthesized a new flexible ligand,
N,N0-bis(3-pyridylmethyl)-1,4-benzenedimethyleneimine (bpb),
using the 1,4-benzenedimethylene group instead of the ethylene
unit in L1 and L2. Here, we report on the syntheses, structural
characterizations and properties of four novel compounds,
namely [Ag(bpb)]NO3 2H2O (1), [Cu2(CH3COO)4(bpb)] (2),
[ZnCl2(bpb)2] (3) and [MnCl2(bpb)2] (4).
ꢁ
Experimental
General Procedures and Measurements. All commercially
available chemicals were of reagent-grade and used as received
without further purification. Solvents were purified by the standard
methods before use. Elemental analyses of C, H and N were taken on
a Perkin-Elmer 240C elemental analyzer, at the Center of Materials
Analysis, Nanjing University. 500 MHz 1H NMR spectroscopic
measurements were performed on a Bruker DRX-500 NMR
spectrometer. Magnetic measurements on a poly-crystalline sample
of complexes 2 and 4 were carried out using a CHAN-2000 Faraday
magnetometerinthe75–300Ktemperaturerange. Theapparatuswas
calibrated with [Ni(en)3]S2O3 (en = ethylenediamine). Diamagnetic
corrections were made using Pascal’s constants. Luminescence
spectra were recorded on a Hitachi 850 fluorescence spectrophoto-
meter at room temperature (25 ꢂC).
Preparation of N,N0-Bis(3-pyridylmethyl)-1,4-benzenedi-
Chart 1.
methyleneimine (bpb).
This compound was synthesized by
modified procedures reported for the preparation of ꢀ; ꢀ0-bis[di(2-
pyridine)methylimino]-m-xylene.14 Terephthalaldehyde (1.34 g,
0.01 mol) was dissolved in methanol (45 mL), and the solution was
stirred for 0.5 h at room temperature; 3-(aminomethyl)pyridine (2.04
We have recently been exploring the assembly reaction of
didentate and the bridging ligands 1,2-bis(4-pyridylmethylami-
no)ethane (L1) and 1,2-bis(4-pyridylmethyleneamino)ethane
(L2) with transition-metal ions (Chart 1).7;13 The results

762 Bull. Chem. Soc. Jpn., 76, No. 4 (2003)
1D Metal Complexes with Bridging Ligand
mL, 0.02 mol) was then added dropwise. The reaction mixture was
refluxed for 8 h. After cooling to room temperature, the solution was
concentrated, and then excess diethyl ether was added to the residue.
8.59 (s, 2H), 8.60 (s, 2H).
Preparation of [MnCl2(bpb)2] (4).
obtained with a yield of 54% by the same method used for the
This compound was
ꢂ
After standing overnight at ꢃ18 C, a white crystalloid solid was
preparation of 3 using MnCl2 4H2O (19.8 mg, 0.1 mmol) instead of
ꢁ
obtained by filtration, washed with diethyl ether and dried in a
vacuum desiccator. Yield: 89%. Found: C, 76.36; H, 5.79; N,
17.62%. Calcd for C20H18N4: C, 76.41; H, 5.77; N 17.82%. 1H NMR
(CDCl3, 298 K) ꢁ 4.87 (s, 4H), 7.31 (dd, J ¼ 7:8, 4.8 Hz, 2H), 7.72
(d, J ¼ 7:8 Hz, 2H), 7.86 (s, 4H), 8.48 (s, 2H), 8.56 (d, J ¼ 4:8 Hz,
2H), 8.65 (s, 2H).
ZnCl2. Found: C, 63.70; H, 4.88; N, 14.88%. Calcd for C40H36Cl2-
MnN8: C, 63.67; H, 4.81; N, 14.85%.
Crystal Structure Determination. The intensity data for the
titledcomplexes werecollected at200 K on a Rigaku RAXIS-RAPID
Imaging Plate diffractometer using graphite-monochromated Mo-
ꢀ
Kꢀ radiation (ꢂ ¼ 0:7107 A). The structures were solved by a direct
Preparation of [Ag(bpb)]NO 2H O (1). All procedures, for
2
method with SIR92,15 expanded using Fourier techniques16 and
refined by a full-matrix least-square method anisotropically for non-
hydrogen atoms. The hydrogen atoms, except for those of water
molecules, were generated geometrically. All of the calculations
were carried out on a SGI workstation using the teXsan crystal-
lographic software package of Molecular Structure Corporation.17
Details of the crystal parameters, data collection and refinements
for complexes 1, 2, 3 and 4 are summarized in Table 1, and selected
bond distances and angles are listed in Table 2.
3ꢀ
example the synthesis and measurement, were carried out in the dark.
A mixture of AgNO3 (34.0 mg, 0.2 mmol) in water (3 mL) and bpb
(62.8 mg, 0.2 mmol) in acetonitrile (40 mL) was stirred for 10
minutes, and then filtered. Colorless crystals were obtained from the
filtrate after standing for several days at room temperature. Yield:
70%. Found: C, 46.05; H, 4.49; N, 13.25. Calcd for C20H22AgN5O5:
C, 46.17; H, 4.26; N, 13.46%. 1H NMR (CD3CN, 298 K) ꢁ 4.84 (s,
4H), 7.36 (dd, J ¼ 7:5, 4.5 Hz, 2H), 7.76 (d, J ¼ 7:5 Hz, 2H), 7.88 (s,
4H), 8.50 (s, 2H), 8.56 (d, J ¼ 4:5 Hz, 2H), 8.61 (s, 2H).
Preparation of [Cu2(CH3COO)4(bpb)] (2). A solution of
Result and Discussion
Cu(CH3COO)2 H2O (39.9 mg, 0.2 mmol) in methanol (6 mL) was
ꢁ
Description of Crystal Structures. The crystallographic
study provides direct evidence for the structure of the complexes.
As listed in Table 1, complexes 1, 2, 3 and 4 crystallize in the
carefully layered over a solution of bpb (62.8 mg, 0.2 mmol) in
methanol (6 mL). After a few days, single crystals suitable for X-ray
diffraction studies were obtained. Yield: 86% (based on copper
acetate). Found: C, 49.70; H, 4.51; N, 8.10%. Calcd for
C28H30Cu2N4O8: C, 49.63; H, 4.46; N, 8.27%.
Preparation of [ZnCl2(bpb)2] (3). It was also prepared by a
layering method using ZnCl2 (13.6 mg, 0.1 mmol) in methanol (10
mL) and bpb (62.8 mg, 0.2 mmol) in methanol (10 mL). After a few
days, crystals were obtained. Yield: 76%. Found: C, 62.57; H, 4.76;
N, 14.57%. Calcd for C40H36Cl2N8Zn: C, 62.80; H, 4.74; N, 14.65%.
1H NMR (DMSO-d6, 298 K)ꢁ4.83 (s, 4H), 7.39 (dd, J ¼ 7:5, 4.5 Hz,
2H), 7.76 (d, J ¼ 7:5 Hz, 2H), 7.87 (s, 4H), 8.48 (d, J ¼ 4:5 Hz, 2H),
ꢁ
same crystal system with the same space group of P1. However,
the shapes of these complexes are different. Complexes 1 and 2
havezigzagandalmostlinearchainstructures,respectively, while
the structures of complexes 3 and 4 are hinged chains.
Figure 1 shows the crystal structure of complex 1 together with
the atom numbering scheme. Each silver(a) atom is coordinated
with two N atoms of the pyridyl unit from two different bpb
ligands with nearly linear coordination geometry [N11–Ag–
N21B = 174.0(2)ꢂ, Table 2]; in turn, each bpb ligand connects
Table 1. Crystallographic and Refinement Data for Complexes 1, 2, 3 and 4
Complex
1
2
3
4
Chemical formula
Formula weight
Crystal system
Space group
C20H22AgN5O5
520.30
triclinic
C28H30Cu2N4O8
677.64
triclinic
C40H36Cl2N8Zn
765.04
triclinic
C40H36Cl2MnN8
754.61
triclinic
ꢁ
P1
ꢁ
P1
ꢁ
P1
ꢁ
P1
ꢀ
a/A
9.2704(7)
10.5258(6)
11.7711(14)
87.812(12)
73.059(10)
74.465(4)
1057.63(16)
2
7.5582(7)
8.3154(5)
12.5861(11)
71.888(2)
77.723(4)
82.196(5)
732.57(10)
1
7.6480(2)
9.2949(5)
12.7940(3)
100.916(3)
102.547(3)
95.331(3)
863.14(6)
1
7.7188(5)
9.3401(6)
12.8647(6)
100.6707(12)
102.597(5)
95.098(2)
881.38(9)
1
ꢀ
b/A
ꢀ
c/A
ꢀ/ꢂ
ꢃ/ꢂ
ꢄ/ꢂ
ꢀ 3
Volume/A
Z
Dcalcd/g cmꢃ3
ꢅ(Mo Kꢀ)/mmꢃ1
F(000)
Total data
Unique data
Observed data
No. of parameters
GOF on F2
1.634
0.995
528
7566
4412
2658
280
0.981
1.536
1.507
348
6813
3303
2810
190
1.048
1.472
0.910
396
7240
3790
2454
232
1.049
1.422
0.569
391
8136
3979
3097
232
1.039
R indices [ðIÞ > 2ꢆðIÞ]
wR [ðIÞ > 2ꢆðIÞ]
R indices (all data)
wR (all data)
0.0763
0.1943
0.1243
0.2175
0.0304
0.0732
0.0410
0.0770
0.0643
0.1819
0.1109
0.2033
0.0339
0.0807
0.0514
0.0853

H.-F. Zhu et al.
Bull. Chem. Soc. Jpn., 76, No. 4 (2003)
763
Fig. 1. Infinite 1D zigzag chain structure (cation part) of 1. The anions, solvents and hydrogen atoms are omitted for clarity, and the
thermal ellipsoids are drawn at 50% probability level.
ꢀ
Table 2. Selected Bond Distances (A) and Angles (deg) for
Complexes 1, 2, 3 and 4aÞ
1
Ag1–N21i
N21i–Ag1–N11
2.150(6)
174.0(2)
Ag1–N11
2.160(6)
2
Cu1–O1
Cu1–O3
1.9661(15) Cu1–O4ii
1.9675(16) Cu1–N11
1.9683(15) Cu1–Cu1ii
89.56(7)
168.10(6) O4ii–Cu1–N11
1.9732(15)
2.1797(17)
2.6288(5)
93.95(6)
94.24(7)
85.41(5)
85.61(5)
82.71(4)
82.63(5)
175.36(5)
Cu1–O2ii
O1–Cu1–O3
O1–Cu1–O2ii
O3–Cu1–O2ii
O1–Cu1–O4ii
O3–Cu1–O4ii
O2ii–Cu1–O4ii
O1–Cu1–N11
O3–Cu1–N11
O2ii–Cu1–N11
89.05(7)
88.07(7)
O1–Cu1–Cu1ii
O3–Cu1–Cu1ii
168.15(6) O2ii–Cu1–Cu1ii
90.89(7)
97.95(6)
97.59(7)
O4ii–Cu1–Cu1ii
N11–Cu1–Cu1ii
Fig. 2. Crystal packing diagram of complex 1 on bc plane
with hydrogen bonds indicated by dashed lines.
hydrogen bonds. The existence and structural importance of such
weak C–H O hydrogen bonding interactions have been reported
3
ꢁꢁꢁ
Zn1–N11
Zn1–Cl1
2.269(4)
2.4869(11)
Zn1–N21iii
2.366(4)
and discussed recently.18 For example, the C–H O hydrogen
bonds have been observed in the complex (C14H12N2)[Cu(opba)]
ꢁꢁꢁ
N11–Zn1–N21iv
N11–Zn1–N21iii
N11–Zn1–Cl1
Cl1–Zn1–Cl1v
90.56(14) N11v–Zn1–Cl1
89.44(14) N21iii–Zn1–Cl1
90.51(11) N21iv–Zn1–Cl1
89.49(11)
89.60(10)
90.40(10)
180.0
3H2O [opba = o-phenylenebis(oxamate)] with C–O distances
rangingfrom3.231(3)to3.448(17)A.18a Thedataofthehydrogen
ꢁ
ꢀ
bonds for the complexes 1–4 are summarized in Table 3.
A single-crystal X-ray structure analysis revealed that com-
pound 2 is composed of dicopper tetracarboxylate units (Fig. 3)
180.0
N11–Zn1–N11v
N21iii–Zn1–N21iv 180.0
ꢀ
with a short Cu–Cu internuclear separation of 2.6288(5) A, which
4
Mn1–N11
Mn1–Cl1
2.2840(14) Mn1–N21iv
2.5097(4)
2.3895(13)
90.68(4)
is longer than that observed in [Cu (CH COO) (H O) ] [Cu Cu:
2
ꢁꢁꢁ
3
4
2
2
14
ꢀ
2.616(1) A].
The average bond length of the Cu–O bonds
N11–Mn1–N21vi 89.12(5)
N11–Mn1–N21iv 90.88(5)
N11–Mn1–Cl1vii 89.32(4)
N11–Mn1–Cl1
ꢀ
[1.9688(15) A] is almost the same as that observed in
[Cu2(CH3COO)4(H2O)2]. Each copper(b) atom is in a square-
pyramidal coordination geometry, neglecting the Cu–Cu interac-
tion, withone pyridylNatom frombpbligandand fourO atomsof
four bridging acetate anions. The copper(b) atom is displaced by
N21vi–Mn1–Cl1 89.39(4)
N21iv–Mn1–Cl1 90.61(4)
N11–Mn1–N11vii 180.0
Cl1–Mn1–Cl1vii
N21iv–Mn1–N21v 180.0
180.0
ꢀ
about 0.203 A from the mean plane of four O atoms towards the
pyridyl N atom, at the apical position of the pyramid with a Cu–N
ꢀ
distance of 2.1797(17) A (Table 2). Each bpb ligand links two
dicopper tetracarboxylate units to generate a 1D linear sawtooth
chain (Fig. 3). The 1D chains in complex 2 were further
a) Symmetry code: (ffi) x, 1 þ y, ꢃ1 þ z; (ffl) 1 ꢃ x, ꢃy, 2 ꢃ z; (ƒ)
2 ꢃ x, 1 ꢃ y, 1 ꢃ z; (Ð) ꢃ2 þ x, ꢃ1 þ y, ꢃ1 þ z; (ð) ꢃx, ꢃy,
ꢃz; (Þ) 2 ꢃ x, 1 ꢃ y, 2 ꢃ z; (þ) ꢃx, ꢃy, 1 ꢃ z.
two silver(a) atoms to give a zigzag chain structure. The average
ꢀ
Ag–N bond length of 2.155(6) A of 1 is shorter than that of the
connected by inter-chain C–H O hydrogen bonds (Table 3) to
ꢁꢁꢁ
13
ꢀ
silver(a) complex with the L1 ligand [2.360(3) A].
It is
form a 2D network structure, as illustrated in Fig. 4. The bulk of
the dicopper tetracarboxylate unit makes the ligand bpb adopt a
near linear conformation.
noticeable that the imine N atoms of bpb did not participate in the
coordination with the silver(a) atoms in1. However, inthe case of
the copper(a) complex of L2, two imine N and one pyridyl N
atoms of the L2 coordinate to the metal atom.7 From the crystal
packing diagram of 1 shown in Fig. 2, it can be seen that the
In complexes 1 and 2, each metal atom was coordinated with
two pyridyl N atoms from two bpb ligands, as mentioned above.
However, in the case of complexes 3 and 4, both zinc(b) and
manganese(b) atoms are six-coordinated with a N4Cl2 binding set
cationic chains and nitrate anions are connected by C–H O
ꢁꢁꢁ

764 Bull. Chem. Soc. Jpn., 76, No. 4 (2003)
1D Metal Complexes with Bridging Ligand
aÞ
ꢀ
Table 3. Distances (A) and Angles (deg) of Hydrogen Bonding for Complexes 1, 2, 3 and 4
1
D–H AbÞ
Distance (D A)
D–H–A
Angle (D–H–A)
142.5
136.4
141.6
135.6
140.9
ꢁꢁꢁ
ꢁꢁꢁ
C12–H8 O3i
3.212(5)
3.286(5)
3.412(5)
3.339(5)
3.310(5)
C12–H8–O3i
C16–H11–O4
C21–H13–O3ii
C22–H15–O4
C26–H18–O3i
ꢁꢁꢁ
C16–H11 O4
ꢁꢁꢁ
ꢁꢁꢁ
C21–H13 O3ii
C22–H15 O4
C26–H18 O3i
ꢁꢁꢁ
ꢁꢁꢁ
2
3
C3–H2 O2iii
3.422(5)
3.457(5)
C3–H2–O2iii
160.1
150.5
ꢁꢁꢁ
C32–H10 O1iv
C32–H10–O1iv
ꢁꢁꢁ
C21–H14 Cl1v
3.724(5)
3.350(5)
3.390(5)
C21–H14–Cl1v
C22–H15–Cl1vi
C26–H18–Cl1vii
161.8
131.2
129.7
ꢁꢁꢁ
C22–H15 Cl1vi
ꢁꢁꢁ
C26–H18 Cl1vii
ꢁꢁꢁ
4
C21–H14 Cl1v
3.7566(18)
3.3681(18)
3.4174(17)
C21–H14–Cl1v
C22–H15–Cl1viii
C26–H18–Cl1vii
161.5
131.8
130.0
ꢁꢁꢁ
C22–H15 Cl1viii
ꢁꢁꢁ
C26–H18 Cl1vii
ꢁꢁꢁ
a) Symmetry code: (ffi) 1 ꢃ x, ꢃy, 1 ꢃ z; (ffl) x, 1 þ y, z; (ƒ) 1 ꢃ x, 1 ꢃ y, ꢃz; (Ð) 1 ꢃ x, 1 ꢃ y, ꢃz; (ð)
1 þ x, 1 þ y, 1 þ z; (Þ) 2 ꢃ x, 1 ꢃ y, 1 ꢃ z; (þ) 2 þ x, 1 þ y, 1 þ z; (¼) 2 ꢃ x, 1 ꢃ y, 2 ꢃ z. b) D:
donor; A: acceptor.
Fig. 3. Crystal structure of complex 2 with the thermal ellipsoids drawn at 50% probability level. Hydrogen atoms are omitted for
clarity.
additional positions are occupied by two chloride atoms with the
trans configuration. Each bpb ligand in turn binds to two metal
atomstogenerateaninfinite1Dhingedchainstructure (Fig. 5). A
similar hinged chain structure was observed in the silver(a)
complex with the L1 ligand.13a The 1D chains were further
connected by inter-chain C–H Cl hydrogen bonds to form a 3D
structure (Fig. 6). The distances of C Cl are in the range of
ꢁꢁꢁ
ꢁꢁꢁ
ꢀ
3.350(5)–3.724(5) A and the C–H–Cl angles are in the range from
129.7 to 161.8ꢂ (Table 3), which indicate the formation of
C–H Cl hydrogen bonds. Similar C–H Cl interactions with C–
ꢁꢁꢁ
ꢁꢁꢁ
ꢀ
Cl distances ranging from 3.335 to 3.821 A have been reported in
a anion-templated rotaxane-like complex and discussed in detail
recently.19
It is noteworthy that the conformations of the bpb ligand are
different incomplexes1, 2and3(aswellas4). Thebpbligandhas
‘‘Z’’ and ‘‘L’’ shapes in complexes 1 and 3 (4), respectively, while
the conformation of the bpb ligand in 2 is almost linear. Such
difference in the conformation of the bpb ligand causes different
intra-chain metal-metal distances in complexes 1, 2, 3 and 4. The
Fig. 4. 2D network structure of complex 2 with hydrogen
bonds indicated by the dashed lines.
and a distorted octahedral geometry. From the crystal data listed
in Table 1, it is clear that complexes 3 and 4 are isomorphous and
isostructural. Figure 5 shows the structure of complex 3 with the
atom-labeling scheme. The zinc(b) atom is coordinated by four
pyridyl N atoms from four different bpb ligands, and the two
ꢀ
longest intermetallic distance of 20.81 A (e.g. Cu1 Cu1A and
ꢁꢁꢁ
Cu1B Cu1C in Fig. 3) was observed in complex 2 with a near
ꢁꢁꢁ
ꢀ
linear conformation of the bpb ligand; the shortest one (15.49 A)
appeared in complex 1 with a ‘‘Z’’ shape of the bpb ligand. The

H.-F. Zhu et al.
Bull. Chem. Soc. Jpn., 76, No. 4 (2003)
765
Fig. 5. Atomic displacement ellipsoid drawing (50% probability level) and atomic labeling system for the complex 3. Hydrogen
atoms are omitted for clarity.
based bridging ligand. The specific orientations of N-donors (3-
pyridyl rather than well-studied 4-pyridyl) and the spacer moiety
between the two pyridyl groups may result in novel network
structures not achievable by other reported bridging ligands, such
as 1,2-bis(4-pyridyl)ethane, 1,2-bis(4-pyridyl)ethylene and 1,3-
bis(4-pyridyl)propane.20 Further studies on the reactions of the
bpb ligand with other metal salts are now in progress.
Magnetic Properties. The variable-temperature magnetic
susceptibilities of complexes 2 and 4 were measured over a
temperature range of 70–300 K (Fig. 7). For complex 2, the
observed magnetic moments are 1.87 ꢅB (ꢅB ꢄ 9:27 ꢅ 10ꢃ24
J Tꢃ1)at300Kand0.20ꢅB at75Kperdicoppertetracarboxylate
ꢁ
unit. The magnetic moment decreases upon cooling, which
indicates a typical behavior ofthe binuclearunit ofcopper(b) with
the presence of antiferromagnetic interactions. The variation of
the magnetic susceptibility with the temperature of 2 is similar to
that observed in [Cu2(CH3COO)4(H2O)2] with the same dicopper
Fig. 6. 3D structure of 3 linked by C–H Cl hydrogen bonds
ꢁꢁꢁ
tetracarboxylate unit, which implies that there is no practical
magnetic interactions between the neighboring dicopper tetra-
indicated by the dashed lines.
ꢀ
ꢀ
carboxylate units due to their large separations of 20.81 A (intra-
ꢀ
chain) (vide supra) and 7.56 A (inter-chains). The effective
Zn Zn and Mn Mn separations are 18.10 and 18.28 A in
ꢁꢁꢁ ꢁꢁꢁ
complexes 3 and 4 with an ‘‘L’’ shape of bpb, respectively.
From the crystal structures of complexes 1–4 described above
and related metal complexes with the L1 and L2 ligands reported
previously,7;13 it can be clearly seen that the structure of the
organic ligand has great influence on the structures of the
assembly products. The amine N atoms of L1 and the imine N
atomsofL2together withtheir pyridyl N atomscoordinatedtothe
metalatomstoformmetalcomplexeswith1Dor2Dstructures,7;13
whilethe imineNatomsof thebpbliganddidnotcoordinatetothe
metalatomsincomplexes1–4. TheL1ligandformeda1Dhinged
chain and 2D grid network complexes with AgNO3 and
magnetic moment of 4 is 5.68 ꢅB at 300 K, which is close to the
valueof5.92ꢅB expectedfortheisolatedhigh-spinMn(b)(S =5/
2). The effective moment decreases slightly to a value of 5.36 ꢅB
at 75 K, indicating that there is only very weak magnetic
interactions between the neighboring Mn(b) ions through the
bridging bpb ligand, due to the long intermetallic distances of
ꢀ
ꢀ
18.28 A (intra-chain) (vide supra) and 7.72 A (inter-chains), as
revealed by the X-ray crystal structure.
Photoluminescence Properties. The photoluminescence
properties of complexes 1, 2, 3 and 4 were studied in the solid
state. No clear photoluminescence was observed for the bpb and
its silver(a) (1) and manganese(b) (4) complexes at room
temperature. It is known that silver(a) and manganese(b) com-
plexes may emit weak photoluminescence at low temperature,
and that their luminescence at room temperature is unobserv-
able.21 In contrast to complexes 1 and 4, the copper(b) (2) and
zinc(b) (3) complexes show intense violet-blue photolumines-
cence under the same conditions. Complex 2 exhibits photo-
luminescence with emissions at 418 and 438 nm upon excitation
at 360 nm and complex 3 displays photoluminescence with an
emission maximum at 460 nm upon excitation at 398 nmand with
an emission maximum at 444 nm upon excitation at 364 nm, as
illustrated in Fig. 8. The photoluminescence behavior of
copper(b) and zinc(b) complexes with various organic ligands
has been extensively studied in recent years.22 No emissions
originating from metal-centered and metal-to-ligand (MLCT) or
Cu(CH3COO)2 H2O, respectively, in which the Ag(a) and
ꢁ
Cu(b) atoms are four-coordinated with a distorted tetrahedral
and square planar geometry; all four N atoms of each L1 ligand
coordinatetothe metalatoms,7,13a while inthe casesofcomplexes
1 and 2, the Ag(a) atom and dicopper tetracarboxylate unit
connect two bpb ligands to form 1D chains and only two of four N
atoms of each bpb ligand bind to the metal atoms (vide supra).
The non-coordination of the imine N atoms of the bpb ligand may
probably be caused by a much more rigid spacer group of 1,4-
benzenedimethylene in the bpb ligand compared with the flexible
ethylene group inthe L1 and L2ligands, and by the lower electron
density around the imine N atoms. The –C=N– groups in ligand
bpbconjugatewiththecentralbenzeneringgroupandtheelectron
density around the imine N atomsisdecreased, sothatthe electron
donation of the imine group is reduced. The non-coordination of
imine N atoms makes the bpb as a derivative of the bipyridyl-

766 Bull. Chem. Soc. Jpn., 76, No. 4 (2003)
1D Metal Complexes with Bridging Ligand
Fig. 8. Photo-induced emission spectrum of
2 with
ꢂex ¼ 360 nm (—) and photo-induced emission spectrum
of 3 with ꢂex ¼ 364 nm ( ) and ꢂ ¼ 398 nm (- - -) in the
ꢁꢁꢁ
ex
solid state at room temperature.
the coordination of Zn(b). Incontrasttothezinc(b)complex3, the
luminescence of complex 4 may probably be quenched by the
Mn(b) ion.22b The results indicate that the photoluminescence
propertiesofthemetal-organiccomplexesdependonthe nature of
the organic ligand as well as the metal ions.
This work was supported by National Natural Science
Foundation of China.
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