Syntheses, supramolecular structures and properties of six coordination complexes based on 5-sulfosalicylic acid and bipyridyl-like chelates

Article abstract of DOI:10.1016/j.poly.2007.05.037

Six new complexes constructed by 5-sulfosalicylic acid and bipyridyl-like ligands (2,2′-bipy and 1,10-phen), namely [Cu₄(OH)₂(ssal)₂(phen)₄ · 7H₂O] (1), [Cu₄(OH)₂(ssal)₂(bipy)₄ · 2H₂O] (2), [Cd(Hssal)(bipy)] (3), [Cd(HL)₂(phen)₂] (4), [Cr(ssal)(bipy)(H₂O)₂ · 2H₂O] (5) and [Cr(ssal)(phen)₂] (6) (H₃ssal = 5-sulfosalicylic acid, H₂L = p-hydroxybenzenesulfonic acid, bipy = 2,2′-bipy, phen = 1,10-phen) were prepared under hydrothermal conditions and their structures were determined by single-crystal X-ray diffraction. Complexes 1 and 2 are both tetranuclear copper complexes with a stepped topology. In complex 3, a new coordination mode of the Hssal^2- group is reported in this work. During the synthetic process of complex 4, in situ decarboxylation of 5-sulfosalicylic acid into p-hydroxybenzenesulfonic acid is involved. Two chromium 5-sulfosalicylates (5 and 6) are reported for the first time. These new complexes display different supramolecular structures by O-H?O, C-H?O hydrogen bonds as well as π?π, C-H?π and O?π interactions. The results of magnetic determination show that ferromagnetic interactions exist in complex 1, however, antiferromagnetic interactions exist in 2.

Full text of DOI:10.1016/j.poly.2007.05.037

Polyhedron 26 (2007) 4397–4410
www.elsevier.com/locate/poly
Syntheses, supramolecular structures and properties of six
coordination complexes based on 5-sulfosalicylic acid
and bipyridyl-like chelates
a
a
b
a
a
Jiang-Feng Song , Yan Chen , Zhi-Gang Li , Rui-Sha Zhou , Xiao-Yu Xu ,
a,
a
Ji-Qing Xu *, Tie-Gang Wang
a
College of Chemistry and State Key Laboratory of Inorganic, Synthesis and Preparative Chemistry, Jilin University, Changchun, Jilin 130023, PR China
b
Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China
Received 22 January 2007; accepted 22 May 2007
Available online 8 June 2007
Abstract
Six new complexes constructed by 5-sulfosalicylic acid and bipyridyl-like ligands (2,20-bipy and 1,10-phen), namely [Cu4(OH)2(ssal)2-
(phen)4 Æ 7H2O] (1), [Cu4(OH)2(ssal)2(bipy)4 Æ 2H2O] (2), [Cd(Hssal)(bipy)] (3), [Cd(HL)2(phen)2] (4), [Cr(ssal)(bipy)(H2O)2 Æ 2H2O] (5)
and [Cr(ssal)(phen)2] (6) (H3ssal = 5-sulfosalicylic acid, H2L = p-hydroxybenzenesulfonic acid, bipy = 2,20-bipy, phen = 1,10-phen) were
prepared under hydrothermal conditions and their structures were determined by single-crystal X-ray diffraction. Complexes 1 and 2 are
both tetranuclear copper complexes with a stepped topology. In complex 3, a new coordination mode of the Hssal2ꢀ group is reported in
this work. During the synthetic process of complex 4, in situ decarboxylation of 5-sulfosalicylic acid into p-hydroxybenzenesulfonic acid
is involved. Two chromium 5-sulfosalicylates (5 and 6) are reported for the first time. These new complexes display different supramo-
lecular structures by O–Hꢁ ꢁ ꢁO, C–Hꢁ ꢁ ꢁO hydrogen bonds as well as pꢁ ꢁ ꢁp, C–Hꢁ ꢁ ꢁp and Oꢁ ꢁ ꢁp interactions. The results of magnetic
determination show that ferromagnetic interactions exist in complex 1, however, antiferromagnetic interactions exist in 2.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Crystal structure; Hydrothermal synthesis; 5-Sulfosalicylic acid; Magnetic analysis
1. Introduction
tant synthetic method for design and tailor-making of such
supramolecular materials utilizes suitable organic ligands
that can coordinate to metal ions through one or more pri-
mary coordination sites, whilst at the same time can partic-
ipate in additional bonding interactions (hydrogen bonding
or other molecular contacts) at peripheral sites. An advan-
tage of this method is that it may combine the flexibility of
the weaker interactions with the strength of coordination
bonding. This method has been widely employed in poly-
carboxylate ligands, which have proven to be particularly
effective in the formation of both extended hydrogen
bonded networks and coordination complexes [4,3e]. The
choice of 5-sulfosalicylic acid (H3ssal) can be attributed
to the following reasons: (1) it possesses versatile coordina-
tion modes (Chart 1) and has the ability to construct a
Since 1989, the definition of crystal engineering was pro-
vided by G.R. Desiraju as ‘‘the understanding of intermo-
lecular interactions in the context of crystal packing and in
the utilization of such understanding in the design of new
solids with desired physical and chemical properties’’
[1]. The rational design and construction of novel supramo-
lecular materials based on discrete or polymeric
metal–organic coordination complexes have garnered con-
siderable interest owing to their intriguing topologies and
potential for use as functional materials [2,3]. An impor-
*
Corresponding author. Tel.: +86 431 8499132; fax: +86 431 8499158.
E-mail address: xjq@mail.jlu.edu.cn (J.-Q. Xu).
0277-5387/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.05.037

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J.-F. Song et al. / Polyhedron 26 (2007) 4397–4410
Chart 1. Coordination modes of 5-sulfosalicylates in recent reports (A, B, C, D, E, F, G denote that the 5-sulfosalicylate ligand acts as l1, l2, l3, l4, l5, l6,
l8 connectors to link metal ions, respectively).
novel metal–organic supramolecular network through
specific and directional hydrogen bonds as well as p–p
stacking due to the presence of aryl rings [5–7], (2) 5-sulfo-
salicylic acid has been found to have biological activity and
its metal complexes with Cu(II), Ni(II), Co(II), Mn(II),
Fe(II), Zn(II) and VO(II) exhibit antimicrobial activity

J.-F. Song et al. / Polyhedron 26 (2007) 4397–4410
4399
stronger than that of the free ligand [5b,8]. In order to
avoid the formation of higher dimensional coordination
networks, polycyclic aromatic chelating ligands such as
2,20-bipyridyl (2,20-bipy) and 1,10-phenanthroline (1,10-
phen) were introduced based on the following consider-
ations: (1) chelating bipyridyl-like ligands may provide
supramolecular recognition sites for p–p, C–Hꢁ ꢁ ꢁp stacking
and C–Hꢁ ꢁ ꢁO hydrogen bonding to form interesting supra-
molecular structures [4b,4f,9], (2) the conjugated p systems
containing (hetero) aromatic rings are currently of interests
in the development of fluorescent materials [10].
In order to understand the coordination chemistry of
H3ssal and to prepare new supramolecular materials with
intriguing structures and potential physical properties, we
have recently focused our research on coordination com-
plexes based on 5-sulfosalicylic acid and chelating bipyr-
idyl-like ligands. Here, we report the syntheses and
crystal structures of six new complexes, namely,
[Cu4(OH)2(ssal)2(phen)4 Æ 7H2O] (1), [Cu4(OH)2(ssal)2-
(bipy)4 Æ 2H2O] (2), [Cd(Hssal)(bipy)] (3), [Cd(HL)2(phen)2]
(4), [Cr(ssal)(bipy)(H2O)2 Æ 2H2O] (5) and [Cr(ssal)(phen)2]
(6), together with the magnetic properties of complexes 1
and 2. The crystal structures of complexes Mn(Hssal)
(bipy)2(H2O) Æ 2H2O (7) [6b] and Zn(Hssal)(bipy)(H2O)2
(8) [7d] were reported previously. The results demonstrate
that the discrete or polymeric complexes may build up
higher network connectivity through p–p stacking, C–
Hꢁ ꢁ ꢁp, Oꢁ ꢁ ꢁp and hydrogen-bonding interactions including
weak C–Hꢁ ꢁ ꢁO contacts.
3.57; N, 7.15; S, 4.08. Found: C, 47.52; H, 3.48; N, 7.13;
S, 4.12%. IR (KBr, cmꢀ1): 3407vs, 1603s, 1563m, 1522w,
1472m, 1414m, 1320m, 1221m, 1167m, 1131s, 1146s,
1020s, 849s, 722vs, 604m, 479w.
2.2.2. Cu4(OH)2(ssal)2(bipy)4 Æ 2H2O (2)
The hydrothermal procedure for the synthesis of com-
plex 2 is similar to that for 1 except for the replacement
of phen with 2,2-bipy (0.082 g, 0.5 mmol). Yield: 82%
based on Cu. Anal. Calc. for C54H44N8O16Cu4S2 2: C,
46.98; H, 3.19; N, 8.12; S, 4.64. Found: C, 46.85; H, 3.02;
N, 8.09; S, 4.58%. IR (KBr, cmꢀ1): 3444m, 1602s, 1562m,
1470m, 1413w, 1341w, 1253w, 1211m, 1186m, 1150m,
1030s 771m, 604m, 470w.
2.2.3. Cd(Hssal)(bipy) (3)
A mixture of 3CdSO4 Æ 8H2O (0.403 g, 0.5 mmol), 5-sul-
fosalicylic acid (0.132 g, 0.5 mmol), 2,20-bipy (0.081 g,
0.5 mmol), KOH (0.08 g, 1.4 mmol) and water (15 ml)
was stirred for 30 min at room temperature, transferred
to and sealed in a 25 ml Teflon-lined stainless steel reactor,
and then heated at 150 ꢁC for 72 h. Upon cooling to room
temperature, the light red crystals that were obtained were
filtered and washed with water. Yield: 58% based on Cd.
Anal. Calc. for C17H12N2O6CdS 3: C, 42.08; H, 2.48; N,
4.95; S, 6.60. Found: C, 41.94; H, 2.52; N, 4.87; S,
6.63%. IR (KBr, cmꢀ1): 3112m, 1626w, 1596m, 1559m,
1478m, 1440m, 1254m, 1158m, 1127s, 1017s, 769m,
676m, 602m.
2. Experimental
2.2.4. Cd(HL)2(phen)2 (4)
A mixture of 3CdSO4 Æ 8H2O (0.407 g, 0.5 mmol), 5-sul-
fosalicylic acid (0.132 g, 0.5 mmol), phen (0.108 g,
0.5 mmol), KOH (0.071 g, 1.3 mmol) and water (15 ml)
was stirred for 30 min at room temperature, transferred
to and sealed in a 25 ml Teflon-lined stainless steel reactor,
and then heated at 150 ꢁC for 72 h. Upon cooling to room
temperature, a colorless solution and a spot of white pre-
cipitate were obtained. The solution was filtered and the fil-
trate was allowed to stand at room temperature. After slow
evaporation over several days, red block single crystals
were obtained. Yield: 62% based on Cd. Anal. Calc. for
C36H26N4O8CdS2 4: C, 52.74; H, 3.17; N, 6.84; S, 7.81.
Found: C, 52.67; H, 3.23; N, 6.79; S, 7.83%. IR (KBr,
cmꢀ1): 3168m, 1586m, 1506m, 1424m, 1237s, 1156s,
1122s, 1031s, 844s, 728s, 566m, 451w.
2.1. Materials and physical measurements
All chemicals purchased were of reagent grade and were
used without further purification. Elemental analyses (C,
H, N) were performed on a Perkin–Elmer 240C elemental
analyzer. IR spectra were measured on a Perkin–Elmer
Spectrum One FT-IR spectrometer using KBr pellets.
Magnetic measurements were obtained using an MPMS-
XL magnetometer at H = 1000 Oe in the temperature
range 5–300 K. The magnetic susceptibility data were cor-
rected for the diamagnetism of the constituent atoms using
Pascal’s constants.
2.2. Syntheses of the complexes
2.2.1. Cu4(OH)2(ssal)2(phen)4 Æ 7H2O (1)
2.2.5. Cr(ssal)(bipy)2(H2O)2 Æ 2H2O (5)
A mixture of CuSO4 Æ 5H2O (0.131 g, 0.5 mmol), 5-sul-
fosalicylic acid (0.130 g, 0.5 mmol), phen (0.103 g,
0.5 mmol), KOH (0.062 g, 1.1 mmol) and water (15 ml)
was stirred for 30 min at room temperature, transferred
to and sealed in a 25 ml Teflon-lined stainless steel reactor,
and then heated at 150 ꢁC for 72 h. Upon cooling to room
temperature, the dark green crystals that were obtained
were filtered and washed with water. Yield: 58% based on
Cu. Anal. Calc. for C62H56N8O21Cu4S2 1: C, 47.47; H,
A mixture of Cr2(SO4)3 Æ 6H2O (0.255 g, 0.5 mmol),
5-sulfosalicylic acid (0.134 g, 0.5 mmol), 2,20-bipy
(0.082 g, 0.5 mmol), KOH (0.051 g, 0.9 mmol) and water
(15 ml) was stirred for 30 min at room temperature, trans-
ferred to and sealed in a 25 ml Teflon-lined stainless steel
reactor, and then heated at 150 ꢁC for 72 h. Upon cooling
to room temperature, the green crystals that were obtained
were filtered and washed with water. Yield: 5% based on
Cr. Anal. Calc. for C17H19N2O10CrS 5: C, 41.18; H, 3.84;

4400
J.-F. Song et al. / Polyhedron 26 (2007) 4397–4410
N, 5.65; S, 6.46. Found: C, 41.11; H, 3.90; N, 5.57%. IR
(KBr, cmꢀ1): 3446s, 1608s, 1571m, 1447m, 1472m, 1150s,
1031s, 763m, 602m.
gle crystals were obtained. Yield: 65% based on Mn. Anal.
Calc. for C27H26N4O9MnS 7: C, 50.82; H, 4.08; N, 8.78; S,
5.02. Found: C, 50.65; H, 3.96; N, 8.97; S, 5.18%. IR (KBr,
cmꢀ1): 3453s, 1592s, 1517m, 1469s, 1426m, 1311m, 1167vs,
1033s, 845m, 721s, 601m, 451m.
2.2.6. Cr(ssal)(phen)2 (6)
A mixture of Cr2(SO4)3 Æ 6H2O (0.253 g, 0.5 mmol),
5-sulfosalicylic acid (0.136 g, 0.5 mmol), phen (0.106 g,
0.5 mmol), KOH (0.062 g, 1.1 mmol) and water (15 ml)
was stirred for 30 min at room temperature, transferred
to and sealed in a 25 ml Teflon-lined stainless steel reactor,
and then heated at 150 ꢁC for 72 h. Upon cooling to room
temperature, a red solution was obtained, which was fil-
tered and the filtrate was allowed to stand at room temper-
ature. After slow evaporation over several days, red block
single crystals were obtained. Yield: 35% based on Cr.
Anal. Calc. for C31H19N4O6CrS 6: C, 59.28; H, 3.03; N,
8.92; S, 5.10. Found: C, 59.35; H, 2.84; N, 8.97; S,
5.18%. IR (KBr, cmꢀ1): 3078vw, 1608s, 1574m, 1517m,
1469s, 1426s, 1311m, 1167s, 1033s, 845m, 721m, 601m,
451m.
2.2.8. Zn(Hssal)(bipy)(H2O)2 (8)
The hydrothermal procedure for the synthesis of com-
plex 8 is similar to that for 6 except for the replacement
of Cr2(SO4)3 Æ 6H2O with ZnCl2 (0.074 g, 0.5 mmol). A col-
orless solution and a spot of white deposition were
obtained. The solution was filtered and the filtrate was
allowed to stand at room temperature. After slow evapora-
tion over several days, colorless block single crystals were
obtained. Yield: 72% based on Zn. Anal. Calc. for
C17H16N2O8SZn 8: C, 43.06; H, 3.38; N, 5.91; S, 6.75.
Found: C, 44.12; H, 3.66; N, 5.97; S, 6.68%. IR (KBr,
cmꢀ1): 3283s, 1584s, 1441s, 1153vs, 1053s, 672s, 567s.
2.3. X-ray diffraction data and crystal structure
determination
2.2.7. Mn(Hssal)(bipy)2(H2O) Æ 2H2O (7)
The hydrothermal procedure for the synthesis of com-
plex 7 is similar to that for 6 except for the replacement
of Cr2(SO4)3 Æ 6H2O with MnCl2 Æ 4H2O (0.108 g,
0.5 mmol). The yellow solution was obtained, filtered,
and the filtrate was allowed to stand at room temperature.
After slow evaporation over several days, yellow block sin-
The crystal structures were determined by a single-crystal
X-ray diffraction experiment. The reflection data were col-
lected on a Bruker SMART CCD area-detector diffractom-
eter (Mo Ka radiation, graphite monochromator) at room
temperature with the x-scan mode. Empirical adsorption
corrections were applied to all data using the SADABS
Table 1
The crystallographic data for complexes 1–6
1
2
3
4
5
6
Empirical
formula
Formula weight
Crystal system
Space group
C
62H56Cu4
C54H44Cu4
N8O16S2
1379.25
monoclinic
P2(1)/c
10.919(1)
12.405(7)
20.239(3)
90
104.452(2)
90
2654.0(6)
2
C17H12Cd
N2O6S
484.75
C36H26Cd
N4O8S2
819.16
monoclinic
C2/c
20.307(6)
13.753(9)
14.296(9)
90
123.917(4)
90
3313.1(4)
4
C17H19Cr
N2O10S
C31H19Cr
N4O6S
627.57
monoclinic
C2/c
31.602(4)
10.265(2)
16.536(2)
90
105.406(2)
90
5171.8(1)
8
N8O21S2
1567.43
monoclinic
P2(1)/c
10.839(2)
14.459(3)
19.674(4)
90
102.575(4)
90
3010.3(1)
2
495.40
monoclinic
P2(1)/c
10.102(2)
14.882(4)
14.206(3)
90
110.669(3)
90
1998.3(8)
4
triclinic
ꢀ
P1
˚
a (A)
8.553(2)
9.809(2)
10.562(3)
93.984(4)
103.786(4)
104.416(4)
825.7(3)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
Volume
Z
qcalc (g cmꢀ3
)
1.730
1.726
1.950
1.642
1.647
1.612
Absorption
coefficient (mmꢀ1
1.553
1.741
1.489
0.847
0.737
0.581
)
h Range (ꢁ)
Reflections collected
1.76–26.08
17220
1.94–26.09
15230
2.00–26.10
4660
1.91–26.06
9111
2.05–26.11
11286
1.34–26.04
14198
Unique reflections
5911 [0.0777]
5232 [0.0518]
3178 [0.0212]
3276 [0.0137]
3932 [0.0477]
5101 [0.0409]
[Rint
]
Completeness
Goodness-of-fit on
F2
99.1%
0.998
99.3%
1.024
97.0%
1.032
99.7%
1.060
98.8%
1.040
99.9%
1.023
R indexes [I > 2r(I)]a R1 = 0.0533,
wR2 = 0.1023
R1 = 0.0494,
wR2 = 0.1084
R1 = 0.0724,
R1 = 0.0403,
wR2 = 0.0872
R1 = 0.0512,
wR2 = 0.0921
R1 = 0.0423,
wR2 = 0.1106
R1 = 0.0438,
wR2 = 0.1121
R1 = 0.0697,
wR2 = 0.1646
R1 = 0.1054,
wR2 = 0.1841
R1 = 0.0529,
wR2 = 0.1175
R1 = 0.0797,
wR2 = 0.1318
R (all data)a
R1 = 0.1034,
wR2 = 0.1202
wR2 = 0.1203
P
P
P
P
a
2
R1 = ||Fo| ꢀ |Fc||/ |Fo|; wR2 = [ w(Fo ꢀ Fc2)2/ w(Fo2)2]1/2
.

J.-F. Song et al. / Polyhedron 26 (2007) 4397–4410
4401
Table 2
Table 2 (continued)
˚
Selected bond lengths (A) and angles (ꢁ) for complexes 1-6
O(2)–Cr(1)–O(3W)
O(3)–Cr(1)–O(4W)
88.1(6)
89.0(1)
O(3W)–Cr(1)–N(2)
O(4W)–Cr(1)–N(2)
N(1)–Cr(1)–N(2)
89.0(9)
90.5(4)
78.1(7)
Compound 1
Cu(1)–O(7)
Cu(1)–O(7)#1
Cu(1)–N(4)
Cu(1)–N(3)
Cu(1)–O(3)
Cu(1)–Cu(1)#1
Cu(2)–O(3)
Cu(2)–O(1)
Cu(2)–N(1)
Cu(2)–N(2)
1.947(3)
1.947(4)
2.009(4)
2.012(4)
2.297(3)
2.939(1)
1.882(3)
1.907(3)
2.005(4)
2.021(4)
82.0(7)
O(7)–Cu(1)–N(3)
O(7)#1–Cu(1)–N(3)
N(4)–Cu(1)–N(3)
O(7)–Cu(1)–O(3)
O(7)#1–Cu(1)–O(3)
N(4)–Cu(1)–O(3)
N(3)–Cu(1)–O(3)
O(3)–Cu(2)–O(1)
O(3)–Cu(2)–N(1)
O(1)–Cu(2)–N(1)
O(3)–Cu(2)–N(2)
O(1)–Cu(2)–N(2)
N(1)–Cu(2)–N(2)
161.3(4)
99.1(4)
82.0(2)
97.8(9)
85.0(1)
93.1(2)
100.8(1)
93.2(3)
171.1(9)
95.5(4)
90.5(4)
165.7(1)
81.2(6)
Complex 6
Cr(1)–O(3)
Cr(1)–O(1)
Cr(1)–N(3)
Cr(1)–N(1)
Cr(1)–N(4)
Cr(1)–N(2)
O(3)–Cr(1)–O(1)
O(3)–Cr(1)–N(3)
O(1)–Cr(1)–N(3)
O(3)–Cr(1)–N(1)
1.886(2)
1.912(2)
2.061(3)
2.064(3)
2.077(3)
2.091(3)
91.8(4)
92.5(3)
93.4(3)
94.3(3)
O(1)–Cr(1)–N(1)
N(3)–Cr(1)–N(1)
O(3)–Cr(1)–N(4)
O(1)–Cr(1)–N(4)
N(3)–Cr(1)–N(4)
N(1)–Cr(1)–N(4)
O(3)–Cr(1)–N(2)
O(1)–Cr(1)–N(2)
N(3)–Cr(1)–N(2)
N(1)–Cr(1)–N(2)
N(4)–Cr(1)–N(2)
93.8(1)
169.8(9)
87.6(3)
173.1(2)
79.7(5)
93.1(1)
173.6(5)
90.5(6)
93.2(3)
79.6(4)
90.7(3)
O(7)–Cu(1)–O(7)#1
O(7)–Cu(1)–N(4)
O(7)#1–Cu(1)–N(4)
97.4(3)
177.9(6)
Compound 2
Cu(1)–O(7)#2
Cu(1)–O(7)
Cu(1)–N(3)
Cu(1)–N(4)
Cu(1)–O(6)
Cu(1)–Cu(1)#2
Cu(2)–O(6)
Cu(2)–O(5)
Cu(2)–N(2)
#1 ꢀx + 1, ꢀy, ꢀz + 2; #2 ꢀx + 1, ꢀy, ꢀz; #3 ꢀx + 1, ꢀy, ꢀz + 1;
#4 ꢀx + 1, y, ꢀz + 1/2.
1.952(3)
1.966(3)
1.994(3)
2.012(3)
2.221(3)
2.989(1)
1.908(3)
1.916(3)
1.984(3)
2.017(4)
2.311(3)
80.5(8)
O(7)–Cu(1)–N(4)
N(3)–Cu(1)–N(4)
O(7)#1–Cu(1)–O(6)
O(7)–Cu(1)–O(6)
N(3)–Cu(1)–O(6)
N(4)–Cu(1)–O(6)
O(6)–Cu(2)–O(5)
O(6)–Cu(2)–N(2)
O(5)–Cu(2)–N(2)
O(6)–Cu(2)–N(1)
O(5)–Cu(2)–N(1)
N(2)–Cu(2)–N(1)
O(6)–Cu(2)–O(7)#2
O(5)–Cu(2)–O(7)#2
N(2)–Cu(2)–O(7)#2
N(1)–Cu(2)–O(7)#2
159.7(2)
80.6(7)
83.7(5)
96.0(1)
96.4(5)
104.2(5)
91.8(1)
175.0(2)
93.2(1)
93.9(6)
158.1(4)
81.3(2)
82.2(8)
102.4(7)
96.9(1)
99.2(3)
Table 3
Geometrical parameters of hydrogen bonds in complexes 1–6
D–Hꢁ ꢁ ꢁA
d(D–H)
d(Hꢁ ꢁ ꢁA)
d(Dꢁ ꢁ ꢁA)
\(DHA)
Compound 1
O7–H9ꢁ ꢁ ꢁO4(a)
0.69
2.28
2.98
2.89
2.89
3.13
2.79
2.76
2.90
2.89
2.79
176.24
Cu(2)–N(1)
O1wꢁ ꢁ ꢁO4w(b)
Cu(2)–O(7)#2
O(7)#1–Cu(1)–O(7)
O(7)#1–Cu(1)–N(3)
O(7)–Cu(1)–N(3)
O(7)#1–Cu(1)–N(4)
O1wꢁ ꢁ ꢁO4w(c)
O2wꢁ ꢁ ꢁO4(d)
179.2(7)
98.7(1)
100.0(1)
O2wꢁ ꢁ ꢁO3
O3w–H3wAꢁ ꢁ ꢁO2(e)
O3w–H3wBꢁ ꢁ ꢁO4w(f)
O4w–H4wBꢁ ꢁ ꢁO1w(g)
O4w–H4wAꢁ ꢁ ꢁO6
0.85
0.85
0.85
0.85
1.96
2.10
2.25
1.99
155.82
156.84
131.71
155.77
Compound 3
Cd(1)–N(2)
Cd(1)–O(2)
Cd(1)–O(6)
Cd(1)–N(1)
2.305(3)
2.305(3)
2.318(3)
2.327(4)
2.452(3)
2.584(3)
2.619(3)
168.1(8)
91.1(4)
97.4(1)
71.3(8)
103.2(6)
153.1(9)
133.3(9)
O(2)–Cd(1)–O(1)
O(6)–Cd(1)–O(1)
N(1)–Cd(1)–O(1)
N(2)–Cd(1)–O(4)
O(2)–Cd(1)–O(4)
O(6)–Cd(1)–O(4)
N(1)–Cd(1)–O(4)
O(1)–Cd(1)–O(4)
N(2)–Cd(1)–O(6)#3
O(2)–Cd(1)–O(6)#3
O(6)–Cd(1)–O(6)#3
N(1)–Cd(1)–O(6)#3
O(1)–Cd(1)–O(6)#3
O(4)–Cd(1)–O(6)#3
54.8(3)
91.9(4)
86.2(5)
86.4(1)
82.2(6)
120.0(6)
80.0(3)
130.2(8)
92.0(4)
83.9(7)
66.2(5)
132.4(3)
131.1(6)
54.0(5)
Compound 2
O1wꢁ ꢁ ꢁO1(h)
O1wꢁ ꢁ ꢁO4(i)
2.87
2.95
2.85
O7–H20ꢁ ꢁ ꢁO4(j)
0.83
2.02
172.30
Cd(1)–O(1)
Cd(1)–O(4)
Compound 3
Cd(1)–O(6)#3
N(2)–Cd(1)–O(2)
N(2)–Cd(1)–O(6)
O(2)–Cd(1)–O(6)
N(2)–Cd(1)–N(1)
O(2)–Cd(1)–N(1)
O(6)–Cd(1)–N(1)
N(2)–Cd(1)–O(1)
C7–H12ꢁ ꢁ ꢁO5(k)
0.96
0.97
2.44
2.43
3.41
3.39
174.72
175.51
C4–H1ꢁ ꢁ ꢁO5(k)
Compound 4
O4–H13ꢁ ꢁ ꢁO3(l)
0.91
1.93
2.71
141.49
Compound 5
O1w–H1wAꢁ ꢁ ꢁO4(m)
O1w–H1wBꢁ ꢁ ꢁO1(n)
O2w–H2wAꢁ ꢁ ꢁO1(o)
O2w–H2wBꢁ ꢁ ꢁO5(p)
O3w–H3wAꢁ ꢁ ꢁO2w(q)
O3w–H3wBꢁ ꢁ ꢁO4(r)
O4w–H4wAꢁ ꢁ ꢁO1w(s)
O4w–H4wBꢁ ꢁ ꢁO6(t)
0.87
0.85
0.86
0.85
0.84
0.85
0.84
0.82
2.28
1.95
1.94
1.83
1.78
1.97
1.78
1.88
3.00
2.80
2.79
2.67
2.61
2.72
2.61
2.67
140.36
168.89
167.20
176.29
172.77
146.25
172.12
162.98
Compound 4
Cd(1)–O(1)
Cd(1)–N(1)
Cd(1)–N(2)
O(1)–Cd(1)–O(1)#4
O(1)–Cd(1)–N(1)#4
O(1)–Cd(1)–N(1)
2.236(3)
2.341(3)
2.346(3)
88.4(3)
102.6(9)
89.0(5)
N(1)#4–Cd(1)–N(1)
O(1)–Cd(1)–N(2)#4
N(1)–Cd(1)–N(2)#4
O(1)–Cd(1)–N(2)
N(1)–Cd(1)–N(2)
N(2)#4–Cd(1)–N(2)
163.7(5)
160.2(8)
71.4(7)
92.8(9)
97.0(4)
92.4(8)
Compound 6
C10–H4ꢁ ꢁ ꢁO5(u)
0.95
0.94
2.30
2.35
3.11
3.07
141.26
132.46
Compound 5
Cr(1)–O(3)
Cr(1)–O(2)
Cr(1)–O(3W)
Cr(1)–O(4W)
Cr(1)–N(1)
Cr(1)–N(2)
O(3)–Cr(1)–O(2)
O(3)–Cr(1)–O(3W)
C22–H9ꢁ ꢁ ꢁO4(v)
1.881(3)
1.918(3)
1.997(4)
1.997(4)
2.062(4)
2.067(4)
93.2(6)
O(2)–Cr(1)–O(4W)
O(3W)–Cr(1)–O(4W)
O(3)–Cr(1)–N(1)
O(2)–Cr(1)–N(1)
O(3W)–Cr(1)–N(1)
O(4W)–Cr(1)–N(1)
O(3)–Cr(1)–N(2)
O(2)–Cr(1)–N(2)
91.4(2)
179.4(1)
93.8(9)
172.7(5)
90.2(9)
90.1(1)
172.0(3)
94.7(4)
Symmetry code: (a) ꢀx + 1, y ꢀ 1/2, ꢀz + 3/2; (b) 1 ꢀ x, 1 ꢀ y, 1 ꢀ z;
(c) ꢀ1 + x, y, ꢀ1 + z; (d) x, 0.5 ꢀ y, ꢀ0.5 + z; (e) x, y, z ꢀ 1; (f) ꢀx + 2,
ꢀy + 1, ꢀz + 1; (g) x + 1, y, z + 1; (h) ꢀ1 + x, y, z; (i) 1 ꢀ x, 1 ꢀ y, ꢀz; (j)
ꢀx + 1, y + 1/2, ꢀz + 3/2; (k) 1 ꢀ x, ꢀy, ꢀ;z; (l) x, ꢀy, z + 1/2;
(m) ꢀx + 1, ꢀy + 1, ꢀz + 1; (n) x + 1, ꢀy + 1/2, z + 1/2; (o) x + 1, y, z;
(p) ꢀx + 1, ꢀy + 1, ꢀz; (q) ꢀx + 1, y ꢀ 1/2, ꢀz + 1/2; (r) ꢀx, y ꢀ 1/2,
ꢀz + 1/2 (s) ꢀx + 1, y ꢀ 1/2, ꢀz + 1/2; (t) ꢀx + 1, y ꢀ 1/2, ꢀz + 1/2; (u)
x, 2 ꢀ y, ꢀ0.5 + z; (v) x, 1 ꢀ y, ꢀ0.5 + z.
91.4(6)

4402
J.-F. Song et al. / Polyhedron 26 (2007) 4397–4410
program. The structures were solved by direct methods and
refined by full-matrix least squares on F2 using SHELXTL97
software [11]. Non-hydrogen atoms were refined anisotrop-
ically. The hydrogen atoms were located from difference
maps and refined with isotropic temperature factors in
complexes 1–6. All calculations were carried out using
SHELXTL97 [11] and PLATON99 [12]. The crystallographic data
and pertinent information are summarized in Table 1, and
any additional refinement information is given below.
Complex 1 O1w showed disorder over two positions and
was refined at 0.50 and 0.50 occupancy for each position.
The hydrogen atoms of O1 w, O2w and O3w were not
located from difference Fourier maps, and the O–H dis-
tances of O4w were refined with a DFIX restraint of
6, 7 and 8 were synthesized through evaporation of the fil-
trate after the hydrothermal reaction. We tried to synthe-
size complexes 4, 6, 7 and 8 at room temperature, but
failed. This demonstrates that complexes 4, 6, 7 and 8 were
synthesized under hydrothermal conditions.
3.2. Crystal structures of the complexes
3.2.1. Structure description of
Cu4(OH)2(ssal)2(phen)4 Æ 7H2O (1)
X-ray single crystal diffraction reveals that compound 1
possesses a centrosymmetric Cu4O4 core based on a
stepped topology (Fig. 1) [13]. The Cu4O4 core is composed
of two crystallographically independent Cu (II) atoms
[namely, Cu1 and Cu2]. Cu1 and Cu2 both possess the con-
figuration of a distorted square pyramid, however, there
are two sets of coordination environments around the cop-
per atoms. Cu1 is located in a plane consisting of two nitro-
gen atoms (N3 and N4) from a chelating phen molecule
and two hydroxides (O7 and O7#1), and the axial position
is occupied by the phenolato oxygen atom (O3). For Cu2,
the plane is composed of two nitrogen atoms (N1 and N2)
from the phen molecule, one carboxylate oxygen (O1) and
one phenolato oxygen atom (O3), and the corresponding
axial position is taken by one hydroxide ion (O7#1). Cu1
and Cu2 atoms, with two symmetry-related copper centres,
are connected into a Cu4O4 core by two l3-hydroxo groups
and two phenolato oxygen atoms. The Cu4O4 core consists
of a stepped structure in which three Cu2O2 planes are
formed by Cu2 Cu1 O3 O7#1 I, Cu1 Cu1#1 O7 O7#1 II
and Cu2#1 Cu1#1 O3#1 O7 III. Planes I and III, with a
˚
0.85 A.
Complex 2 Hydrogen atoms of O1w were not located
from difference Fourier maps.
Complex 5 O2 and O3 atoms of the sulfonate group
both showed disorder over two positions and were refined
at 0.50 and 0.50 occupancy, and 0.41 and 0.59 occupancy,
respectively.
Selected bond lengths and angles for complexes 1–6 are
summarized in Table 2. Geometrical parameters of
the hydrogen bonds in complexes 1–6 are summarized in
Table 3.
3. Results and discussion
3.1. Synthesis
5-Sulfosalicylic acid and bipyridyl-like mixed ligands
were reacted in aqueous medium with different metal salts
(Cr2(SO4)3 Æ 6H2O, MnCl2 Æ 4H2O, CuSO4 Æ 5H2O, ZnCl2,
3CdSO4 Æ 8H2O) in a molar ratio of 1:1:1 at different pH
levels ranging from 5 to10 in an attempt to investigate
the reactivity. The reactions were carried out in a 25 ml
Teflon-lined stainless steel reactor at 150 ꢁC for 72 h. We
obtained compounds 1–8 (Scheme 1) at different pH values.
Coordination complexes of Cr(III), Cu(II) and Cd(II) were
obtained under weakly acidic, neutral and weakly basic
conditions, respectively. Complexes 7 and 8 were easily
obtained for the wider pH range 5–8. It is worth noting
that complexes 1, 2, 3 and 5 were all directly obtained
through the hydrothermal method, however, complexes 4,
˚
maximum deviation of 0.1308 A from their least-squares
planes, are parallel to each other, but both have the same
bihedral angle of 103ꢁ with plane II. In the Cu4O4 core,
we observed that the four Cu atoms form a flat rhomboid
with sides Cu1ꢁ ꢁ ꢁCu2 and Cu1#1ꢁ ꢁ ꢁCu2 of lengths 3.18
˚
and 3.59 A, respectively, a short diagonal (Cu1ꢁ ꢁ ꢁCu1#1)
˚
˚
of 2.94 A and a long diagonal (Cu2ꢁ ꢁ ꢁCu2#1) of 6.10 A.
Offset p–p interactions between phen molecules with a
face-to-face distance of 3.43 A and offset angle of 28.74ꢁ
˚
stabilize the tetranuclear complex. To the best of our
knowledge, only one copper complex constructed from
mixed organic ligands with a stepped topology has previ-
ously been reported [13a].
Scheme 1. The reactions to prepare complexes 1–8.

J.-F. Song et al. / Polyhedron 26 (2007) 4397–4410
4403
3.2.2. Structure description of
Cu4(OH)2(ssal)2(bipy)4 Æ 2H2O (2)
Complexes 1 and 2 have the same space group, P21/c.
The molecular structures of complexes 1 and 2 show some
similarities as follows: (a) Both possess the centrosymmet-
ric Cu4O4 (S-Fig. 3) core based on a stepped topology. (b)
The central copper atoms in both complexes have the same
coordination geometry, and the bond lengths and angles,
as shown in Table 2, are also similar. (c) Both possess sim-
ilar 2D supramolecular layers based on tetranuclear Cu (II)
units. However, the replacement of phen by bipy, a chelat-
ing aromatic ligand of a smaller size, leads to some subtle
differences. One difference worth noticing between the crys-
tal structures of 1 and 2 concerns the numbers of water
molecules in their asymmetric units: 3.5 water molecules
for 1 and one water molecule for 2. This results in the for-
mation of a 3D supramolecular network (Fig. 4) for com-
pound 2 differing from that of compound 1. In compound
2, the 2D layers are connected into a 3D supramolecular
network through O1w with symmetry-related layers and
p–p interactions between adjacent Cu4(OH)2(ssal)2(bipy)4
units (offset p–p interactions between 2,20-bipy molecules
Fig. 1. The molecular structure of complex 1.
Each Cu4(OH)2(ssal)2(phen)4 molecule is linked to four
neighboring tetrameric units to form a 2D supramolecular
layer (S-Fig. 1) of rhombic windows (with dimensions of
˚
6.05 · 13.44 A) through hydrogen bonding between l3-
˚
with a face-to-face distance of 3.54 A and offset angle of
24.71ꢁ).
hydroxo groups (O7) and the uncoordinated sulfonate oxy-
gen atoms (O4). The 2D layers are connected into a 3D
supramolecular network by water heptamers (Fig. 2), the
geometrical parameters of the hydrogen bonds are given
in Table 3. In addition to hydrogen bonding, inter-layer
contacts are strengthened by intermolecular p–p interac-
tions between adjacent Cu4(OH)2(ssal)2(phen)4 units (offset
p–p interaction between phen molecules with a face-to-face
3.2.3. Structure description of Cd(Hssal)(bipy) (3)
The crystal analysis of complex 3 reveals that it is a one-
dimensional ladder coordination polymer containing
Cd2O8 (2,20-bipy)2 units (Fig. 5a) with Hssal as the bridge
ligands. The asymmetric unit of complex 3 consists of one
Cd atom, one Hssal anion and one 2,20-bipy ligand. The
Cd center adopts a distorted capped-octahedral conforma-
tion (Fig. 5b) in which the basal plane is formed by two
nitrogen atoms (N1 and N2) from a chelating 2,20-bipy
ligand, a carboxylate oxygen atom (O2) and a sulfonate
oxygen atom (O6) from two different Hssal anions. The
axial positions are taken by a carboxylate oxygen atom
˚
distance of 3.47 A and offset angle 36.53ꢁ). Interestingly,
the water heptamers and sulfonate anions are intercon-
nected into a 2D supramolecular layer with very large
˚
rhombic windows (with dimensions of 12.57 · 17.77 A)
through hydrogen bonding (Fig. 3). The tetranuclear Cu
(II) units are right inside the large rhombic windows
between the 2D layers (S-Fig. 2).
Fig. 2. Perspective view of the 3D supramolecular network of complex 1, phen ligands and H atoms were removed for clarity.

4404
J.-F. Song et al. / Polyhedron 26 (2007) 4397–4410
(O1) and a sulfonate oxygen atom (O6#3). The sulfonate
oxygen atom (O4) occupies the capped position. Each pair
of Cd ions is bridged by a sulfonate oxygen atom (O6) with
symmetry-related partner (O6#3) to form a Cd2O8 (2,20-
bipy)2 unit. These dimeric Cd2 units, featuring a 1D ladder
(Fig. 6a) along the crystallographica axis, are intercon-
nected by Hssal2ꢀ anions. Each Hssal2ꢀ anion connects
three Cd (II) atoms (Fig. 6b) with the carboxylic group
and sulfonate group, adopting l1 ꢀ g1:g1-chelating and
l2 ꢀ g0:g1:g2-bridging/chelating coordination modes [14].
As far as we know, this kind of new coordination mode
of the Hssal2ꢀ group has not been reported previously.
The adjacent chains are further aggregated into a 2D sheet
(S-Fig. 4) through p–p interactions between phen ligands,
˚
with a face-to-face distance of 3.47 A and offset angle
36.52ꢁ,
chelating
C–Hꢁ ꢁ ꢁO
hydrogen
bonding
˚
Fig. 3. 2D supramolecular layer consisting of hydrogen bonded water
heptamers and sulfonate anions in complex 1.
(C4ꢁ ꢁ ꢁO5 = 3.39, C7ꢁ ꢁ ꢁO5 = 3.41 A) and C–Hꢁ ꢁ ꢁp interac-
tions between C8 and H5 from 2,20-bipy ligands and
Hssal2ꢀ rings containing C16 (S-Fig. 5, H5ꢁ ꢁ ꢁp = 2.72 and
˚
C8ꢁ ꢁ ꢁp = 3.59 A).
Fig. 4. Perspective view of the 3D supramolecular network of complex 2, 2,2-bipy ligands were removed for clarity.
Fig. 5. (a) Perspective view of a dimeric Cd unit in complex 3, the C atoms of 2,20-bipy are omitted for clarity. (b) A distorted capped-octahedral
conformation of the Cd (II) ion.

J.-F. Song et al. / Polyhedron 26 (2007) 4397–4410
4405
Fig. 6. (a) A 1D ladder constructed by dimeric Cd2O8N4 units along the a-axis. (b) The coordination mode of the Hssal2ꢀ ligand in complex 3.
3.2.4. Structure description of Cd(HL)2(phen)2 (4)
The crystal analysis of complex 4 reveals that it is a
mononuclear complex consisting of one Cd (II) ion, two
phen molecules and two p-hydroxybenzenesulfonic acid
anions. The Cd (II) center exhibits a distorted octahedral
surrounding (Fig. 7), in which the basal plane is formed
by three nitrogen atoms (N1, N1#4 and N2) from two sym-
metry-related phen molecules and one sulfonate oxygen
atom (O1#4). The axial positions are occupied by a nitro-
gen atom (N1#4) from a phen molecule and a sulfonate
oxygen atom (O1). The p–p interactions between the aro-
matic rings of the different ligands are favorable to stabilize
˚
complex 4. The closest centroid separation is 3.76 A from
the p-hydroxybenzenesulfonic ligand to the C6 ring of the
phen ligand, with an offset angle of 19.85ꢁ. Interestingly,
the Cd(L)2(phen)2 molecules are connected into 1D supra-
molecular double chains (S-Fig. 6), sharing Cd(phen)2 units
˚
by O–Hꢁ ꢁ ꢁO hydrogen bonding (O4ꢁ ꢁ ꢁO3 = 2.71 A) along
the crystallographic c-axis. The adjacent double chains
are further aggregated into a 3D supramolecular network
(Fig. 8) through p–p interactions between phen ligands
˚
(the closest centroid separation is 3.679 A between C6 rings
with an offset angle of 16.31ꢁ) and C–Hꢁ ꢁ ꢁO hydrogen
˚
bonding (C18ꢁ ꢁ ꢁO2 = 3.20 A).
Fig. 7. The molecular structure of complex 4.
3.2.5. Structure description of Cr(ssal)(bipy)-
(H2O)2 Æ 2H2O (5)
X-ray single crystal diffraction reveals that the asym-
metric unit of 5 contains one Cr(III) ion, one ssal anion,
one 2,20-bipy molecule, two coordinated water and two
lattice water molecules. The Cr(III) center exhibits a dis-
torted octahedral surrounding (Fig. 9), in which the basal
plane is formed by two nitrogen atoms from a chelating
2,20-bipy ligand (N1 and N2) and one carboxylate oxygen
(O2) and one phenolic oxygen (O3) from a ssal ligand.

4406
J.-F. Song et al. / Polyhedron 26 (2007) 4397–4410
(Fig. 9) resulting from O–Hꢁ ꢁ ꢁO hydrogen bonds involv-
ing O3w, O2w, O1, O1w and O4. Within the chain, the
p–p interactions between the aromatic rings of the differ-
ent ligands may stabilize the polymeric supramolecular
˚
chain. The closest centroid separation is 4.01 A from the
ssal3ꢀ ligand to the C5N ring (containing the N2 atom)
of the 2,20-bipy ligand with an offset angle of 26.09ꢁ.
The 1D chains are further linked into a 2D layer
(Fig. 10) through O–Hꢁ ꢁ ꢁO hydrogen bonding (O2wꢁ ꢁ ꢁ
O5, O1wꢁ ꢁ ꢁO4w), the geometrical parameters of the
hydrogen bonds of compound 5 are collected in Table 3.
The most remarkable feature of this 2D layer is that there
exist a supramolecular ring (S-Fig. 7) consisting of four
coordinated water molecules (O3w and O4w), six lattice
water molecules (O1w and O2w), three ssal3ꢀ anions
and three Cr3+ ions, formed through covalent bonds and
hydrogen bonds. Only the 2,20-bipy molecules occupy
the supramolecular rings, preventing interpenetration.
Finally, the 2D layers are hydrogen bonded through
O4wB-H4wBꢁ ꢁ ꢁO6 to afford a 3D supramolecular net-
work (S-Fig. 8). Compared with some active transition
metals (Zn, Cd, Cu, etc.), coordination complexes of Cr
are relatively fewer due to its inertness (slow polymeriza-
tion and difficulty of substitution) [15,16]. To the best of
our knowledge, complex 5 is the first example of a chro-
mium 5-sulfosalicylate complex.
Fig. 8. The 3D supramolecular network in complex 4.
The axial positions are occupied by O3w and O4w. Each
Cr(ssal)(bipy)2(H2O)2 unit is hydrogen bonded to two
other units to form a 1D supramolecular helical chain
Fig. 9. 1D supramolecular helical chains consisting of Cr(ssal)(bipy)2(H2O)2 units in complex 5.
Fig. 10. Perspective view of the 2D supramolecular layer in complex 5.

J.-F. Song et al. / Polyhedron 26 (2007) 4397–4410
4407
˚
3.2.6. Structure description of Cr(ssal)(phen)2 (6)
est centroid separation is 3.79 A between the C6 rings of
phen ligands with an offset angle of 25.79ꢁ). The 2D double
layers are further aggregated into a 3D supramolecular net-
work (Fig. 12) through infinite p-stacking between the phen
ligands in head-to-tail way (the closest centroid separation
The asymmetric unit of 6 (Fig. 11) contains one Cr (III)
ion, one ssal anion and two phen molecules. The Cr(III)
center exhibits a distorted octahedral surrounding, in
which the basal plane is formed by two nitrogen atoms
from two different phen ligands (N2 and N4) and two
bidentate chelating coordination oxygen atoms from one
carboxylate oxygen (O1) and one phenolic oxygen (O3).
The axial positions are occupied by N1 and N3 from two
different phen ligands. Each Cr(ssal)(phen)2 unit is hydro-
gen bonded to four other units to form a 2D puckered
supramolecular layer (S-Fig. 9) through C–Hꢁ ꢁ ꢁO (C10–
H8ꢁ ꢁ ꢁO5, C22–H9ꢁ ꢁ ꢁO4). Moreover, Oꢁ ꢁ ꢁp (S-Fig. 10, the
distance of O5 to the C5N ring containing the N3 atom is
˚
is 3.86 A with an offset angle of 13.27ꢁ).
3.3. Magnetic studies of complexes 1–2
The variable temperature magnetic susceptibility of
complexes 1 and 2 was measured at 1000 G in the temper-
ature range 5–300 K. The magnetic behaviors of 1 are
depicted in Fig. 13 in the forms of vM and leff versus T
plots (vM being the molar magnetic susceptibility). As the
temperature is lowered, vM increases slowly until about
50 K, then it dramatically increases at lower temperatures.
˚
3.10 A) [17] and pꢁ ꢁ ꢁp interactions between the aromatic
rings of different ligands (the closest centroid separation
˚
is 3.91 A from the aryl of the ssal anion ligand to the C6
The data between 300 and 5 K can be fit to the Curie–Weiss
P
ring of the phen ligand with an offset angle of 23.91ꢁ) sta-
bilize the 2D puckered supramolecular layer. The 2D layers
are held together into a 2D supramolecular double-layer
through pꢁ ꢁ ꢁp interactions between phen ligands (the clos-
expression, vM = C/(T ꢀ h), [C = 0.125 g2 S(S + 1)], with
the Curie constant C = 1.71 cm3 K molꢀ1, Weiss constant
h = 7.5 K and g = 2.14. On the other hand, at room tem-
perature the effective magnetic moment (leff) equals 3.701
lB, which is slightly higher than the spin-only value of four
4.5
0.4
0.3
0.2
0.1
0.0
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
180
160
140
120
100
80
60
40
20
0
-20
0
50
100
150
T/K
200
250
300
0
50
100
150
T/K
200
250
300
Fig. 11. The molecular structure of complex 6. Hydrogen atoms are
removed for clarity.
Fig. 13. Plots of vM and leff vs. T for complex 1. The inset is the plot of 1/
vM vs. T.
Fig. 12. The 3D representation of the packing arrangement for complex 6. The insets show the existence of infinite p-stacking in a head-to-tail way.
H atoms have been removed for clarity.

4408
J.-F. Song et al. / Polyhedron 26 (2007) 4397–4410
1.1
uncoupled copper (II) S = 1/2 ions (theoretical value for
g= 2, leff = 3.464 lB). The leff value increases gradually
until 5 K, reaching a value of 4.037 lB. This feature is char-
acteristic of the presence of significant ferromagnetic inter-
actions between the copper (II) ions [13b,13f]. Moreover,
the positive sign of the Weiss constant also indicates there
exist ferromagnetic interactions between the Cu (II)
centers.
The magnetic behavior of complex 2 is shown in Fig. 14
in the forms of vM and leff versus T plots. As the tempera-
ture is lowered, vM increases slowly until about 38 K, then
it dramatically increases at lower temperatures. The data
between 300 and 38 K can be fit to the Curie–Weiss expres-
sion, vM = C/(T ꢀ h), [C = 0.125 g2S(S + 1)], with the
Curie constant C = 0.784 cm3 molꢀ1 K and Weiss constant
h = ꢀ0.401 K. The effective magnetic moment (leff) in 2
decreases slowly from 3.43 lB at 300 K to 3.21 lB at
55 K, and then falls rapidly, reaching 2.46 lB at 5 K. At
room temperature the effective magnetic moment (leff)
equals 3.43 lB, which is slightly lower than the spin-only
value of four uncoupled copper (II) S = 1/2 ions (theoret-
ical value for g = 2, leff = 3.46 lB). These features indicate
that there exist anti-ferromagnetic interactions amongst the
Cu (II) centers [13e]. The difference in the magnetic proper-
ties of complexes 1 and 2 is possibly the result of the differ-
ent intermolecular contacts.
Em = 520 nm
486
Ex =347 nm
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
300
350
400
450
500
550
600
Wavenumber/nm
Fig. 15. Solid-state excitation fluorescent (dashed line) and emission (full
line) spectra of complex 3 at room temperature.
Em= 440nm
Ex= 329nm
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
3.4. Fluorescent properties of complexes 3–4
The solid-state fluorescent spectra of complexes 3 and 4
are depicted in Figs. 15 and 16, respectively. In order to
understand the nature of the emission bands of complex
3 and 4, we also investigated the luminescence of the free
2, 2-bipy, phen Æ H2O and H3ssal Æ 2H2O ligands in the solid
state at room temperature. The emission bands for free
phen Æ H2O are at 365, 381, 403 and 437 nm
(kexc. = 344 nm), which may be attributed to the p* ! p
transition (S-Fig. 11). Similar to free phen Æ H2O, the emis-
sion bands for the free 2, 2-bipy ligand, at 390, 413 and
300
350
400
450
500
550
600
650
Wavenumber/nm
Fig. 16. Solid-state excitation fluorescent (dashed line) and emission (full
line) spectra of complex 4 at room temperature.
438 nm (kexc. = 352 nm), are also attributed to the p* ! p
transition (S-Fig. 12). However, the emission bands for free
H3ssal Æ 2H2O are mainly located at about 387 nm with a
shoulder peak at 440 nm (H3ssal Æ 2H2O: kexc. = 335 nm)
and are attributed to p* ! n transitions (S-Fig. 13). Com-
plex 3 exhibits intense green photoluminescence with an
emission maximum at ca. 520 nm upon excitation at
347 nm (Fig. 15). Compared with the emission spectra of
the free 2, 2-bipy and H3ssal Æ 2H2O ligands, the band at
520 nm for 3 might be assigned to the emission of a
ligand-to-metal charge transfer (LMCT), similar to
reported Cd complexes [18]. Complex 4 displays intense
blue photoluminescence with an emission maximum at
ca. 440 nm upon excitation at 329 nm (Fig. 16), compared
with the emission spectra of the free phen Æ H2O and H3ssa-
l Æ 2H2O ligands, the band at 440 nm for 4 is neither LMCT
(ligand-to-metal charge transfer) nor MLCT (metal-to-
ligand charge transfer) in nature, and tentatively might
be assigned to an intraligand fluorescent emission [19,20].
3.5
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
3.0
2.5
2.0
1.5
1.0
0.5
0.0
200
150
100
50
0
0
50
100
150
200
250
300
T/K
0
50
100
150
T/K
200
250
300
Fig. 14. plots of vM and leff vs. T for complex 2. The inset is the plot of
1/vM vs. T.

J.-F. Song et al. / Polyhedron 26 (2007) 4397–4410
4409
Scheme 2.
4. Conclusion
for 1, 2, 3, 4, 5 and 6. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.
html, or from the Cambridge Crystallographic Data Cen-
tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
X-ray crystallographic files of compounds 1–6 in CIF
format, a perspective view of the 2D supramolecular layer
for complex 1 (S-Fig. 1), the plot of the tetranuclear Cu (II)
units included in large rhombic windows consisting of
water heptamers and sulfonate anions (S-Fig. 2), the
molecular structure of complex 2 (S-Fig. 3), the 2D packing
structure of complex 3 (S-Fig. 4), chelating C–Hꢁ ꢁ ꢁO
hydrogen bonding and C–Hꢁ ꢁ ꢁp interactions in complex 3
(S-Fig. 5), 1D supramolecular double chains for compound
4 (S-Fig. 6), the supramolecular ring of the 2D layer in
complex 5 (S-Fig. 7), a plot of the 3D supramolecular net-
work for complex 5 (S-Fig. 8), a plot of the 2D supramo-
lecular layer in complex 6 (S-Fig. 9), the mode of Oꢁ ꢁ ꢁp
and pꢁ ꢁ ꢁp interactions in complex 6 (S-Fig. 10), the plots
of the solid-state excitation fluorescent and emission spec-
tra of the 2,2-bipy ligand (S-Fig. 11), phen Æ H2O
(S-Fig. 12) and H3ssal Æ 2H2O (S-Fig. 13) at room temper-
ature. Supplementary data associated with this article can
be found, in the online version, at doi:10.1016/
j.poly.2007.05.037.
Six new complexes constructed from 5-sulfosalicylic acid
and bipyridyl-like ligands (2,20-bipy and 1,10-phen), namely
[Cu4(OH)2(ssal)2(phen)4 Æ 7H2O] (1), [Cu4(OH)2(ssal)2(bi-
py)4 Æ 2H2O] (2), [Cd(Hssal)(bipy)] (3), [Cd(HL)2(phen)2]
(4), [Cr(ssal)(bipy)(H2O)2 Æ 2H2O] (5) and [Cr(ssal)(phen)2]
(6), (H3ssal = 5-sulfosalicylic acid, H2L = p-hydroxyben-
zenesulfonic acid, bipy = 2,20-bipy, phen = 1,10-phen) were
prepared under hydrothermal conditions and their struc-
tures were determined by single-crystal X-ray diffraction.
Complexes 1 and 2 are both tetranuclear copper complexes
with a stepped topology. In complex 3, a new coordination
mode of the Hssal2ꢀ group is reported in this work. During
the synthetic process of complex 4, in situ decarboxylation of
5-sulfosalicylic acid into p-hydroxybenzenesulfonic acid is
involved. Two chromium 5-sulfosalicylates (5 and 6) are
reported for the first time. These new complexes display dif-
ferent supramolecular structures by O–Hꢁ ꢁ ꢁO, C–Hꢁ ꢁ ꢁO
hydrogen bonds as well as pꢁ ꢁ ꢁp, C–Hꢁ ꢁ ꢁp and Oꢁ ꢁ ꢁp inter-
actions (Scheme 2). Of the six complexes described in this
work, the p-stacking interactions (Oꢁ ꢁ ꢁp, C–Hꢁ ꢁ ꢁp and
pꢁ ꢁ ꢁp) play an important role in the observed structural sta-
bility. It is likely that studies on similar systems would be
favorable for understanding the nature of the p-stacking
and its role in structural stability.
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