Novel dithioether-silver(I) coordination architectures: Structural diversities by varying the spacers and terminal groups of ligands

Article abstract of DOI:10.1039/b416576b

An investigation into the dependence of the framework formation of coordination architectures on ligand spacers and terminal groups was reported based on the self-assembly of AgClO₄ and eight structurally related flexible dithioether ligands, RS(CH₂)_nSR (L _aⁿ, R = ethyl group, L_bⁿ, R = benzyl group, n = 1-4). Eight novel metal-organic architectures, [Ag(L _a¹)_3/2ClO₄]_n (1a), [Ag₂(L_a²)₂(ClO₄) ₂]₂ (2a), [AgL_a³ClO ₄]_n (3a), {[Ag(L_a⁴) ₂]ClO₄}_n (4a), [AgL_b ¹ClO₄]₂ (1b), [Ag(L_b ²)₂]ClO₄ (2b), {[Ag(L_b ³)_3/2(ClO₄)_1/2](ClO ₄)_1/2}_n(3b) and [Ag(L_b ⁴)_3/2ClO₄]_n (4b), were synthesized and structurally characterized by X-ray crystallography. Structure diversities were observed for these complexes: 1a forms a 2-D (6,3) net, while 2a is a discrete tetranuclear complex, in which the Ag¹ ion adopts linear and tetrahedral coordination modes, and the S donors in each ligand show monodentate terminal and μ₂-S bridging coordination fashions; 3a has a chiral helical chain structure in which two homo-chiral right-handed single helical chains (Ag-L_a³-)_n are bound together through μ₂-S donors, and simultaneously gives rise to left-handed helical entity (Ag-S-)_n. In 4a, left- and right-handed helical chains formed by the ligands bridging Ag¹ centers are further linked alternately by single-bridging ligands to form a non-chiral 2-D framework. 1b has a dinuclear structure showing obvious ligand-sustained Ag Ag interaction, while 2b is a mononuclear complex; 3b is a 3-D framework formed by ClO₄^- linking the 2-D (6,3) framework, which is similar to that of 1a, and 4b has a single, double-bridging chain structure in which 14-membered dinuclear ring units formed through two ligands bridging two Ag ¹ ions are further linked by single-bridging ligands. In addition, a systematic structural comparison of these complexes and other reported AgClO₄, complexes of analogous dithioether ligands indicates that the ligand spacers and terminal groups take essential roles on the framework formation of the Ag¹ complexes, and this present feasible ways for adjusting the structures of such complexes by modifying the ligand spacers and terminal groups.

Full text of DOI:10.1039/b416576b

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F U L L P A P E R
Novel dithioether–silver(I) coordination architectures: structural
diversities by varying the spacers and terminal groups of ligands†
Jian-Rong Li, Xian-He Bu,* Jiao Jiao, Wen-Ping Du, Xiu-Hua Xu and Ruo-Hua Zhang
Department of Chemistry, Nankai University, Tianjin, 300071, P. R. China.
E-mail: buxh@nankai.edu.cn; Fax: +86-22-23502458; Tel: +86-22-23502809
Received 28th October 2004, Accepted 25th November 2004
First published as an Advance Article on the web 10th January 2005
An investigation into the dependence of the framework formation of coordination architectures on ligand spacers
and terminal groups was reported based on the self-assembly of AgClO4 and eight structurally related flexible
n
n
dithioether ligands, RS(CH2)nSR (La , R = ethyl group; Lb , R = benzyl group, n = 1–4). Eight novel metal–organic
1
2
3
4
1
architectures, [Ag(La )3/2ClO4]n (1a), [Ag2(La )2(ClO4)2]2 (2a), [AgLa ClO4]n (3a), {[Ag(La )2]ClO4}n (4a), [AgLb ClO4]2
2
3
4
(1b), [Ag(Lb )2]ClO4 (2b), {[Ag(Lb )3/2(ClO4)1/2](ClO4)1/2}n (3b) and [Ag(Lb )3/2ClO4]n (4b), were synthesized and
structurally characterized by X-ray crystallography. Structure diversities were observed for these complexes: 1a forms
a 2-D (6,3) net, while 2a is a discrete tetranuclear complex, in which the AgI ion adopts linear and tetrahedral
coordination modes, and the S donors in each ligand show monodentate terminal and l2-S bridging coordination
fashions; 3a has a chiral helical chain structure in which two homo-chiral right-handed single helical chains
3
(Ag–La –)n are bound together through l2-S donors, and simultaneously gives rise to left-handed helical entity
(Ag–S–)n. In 4a, left- and right-handed helical chains formed by the ligands bridging AgI centers are further linked
alternately by single-bridging ligands to form a non-chiral 2-D framework. 1b has a dinuclear structure showing
obvious ligand-sustained Ag–Ag interaction, while 2b is a mononuclear complex; 3b is a 3-D framework formed by
−
ClO4 linking the 2-D (6,3) framework, which is similar to that of 1a, and 4b has a single, double-bridging chain
structure in which 14-membered dinuclear ring units formed through two ligands bridging two AgI ions are further
linked by single-bridging ligands. In addition, a systematic structural comparison of these complexes and other
reported AgClO4 complexes of analogous dithioether ligands indicates that the ligand spacers and terminal groups
take essential roles on the framework formation of the AgI complexes, and this present feasible ways for adjusting the
structures of such complexes by modifying the ligand spacers and terminal groups.
AgI is a favorable and fashionable building block or connect-
Introduction
ing node for constructing coordination architectures due to its
In recent years, the construction of metal–organic coordination
coordination diversity and flexibility.13 Therefore, the investiga-
architectures has continued to attract great attention due
tions of AgI complexes with flexible ligands are of significance
to not only the intriguing variety of their structures and
for investigating the relationship between the complex structures
new topologies, but also their potential applications as new
and ligands nature, solvent, counter anions and other factors.
materials.1–3 Considerable efforts have been made on the theoret-
In order to obtain information at the basic structural level,
ical predication and network-based approaches for controlling
the topology and geometries of the networks to produce useful
of interest for the crystal engineering of novel coordination
12i–o
architectures, our recent efforts
have focused on the investiga-
functional materials,4,5 and some successes have been reported,
however, no method gave consistently reliable predictions, as
stated by Dunitz,6 because the self-assembly progress is highly
affected by several factors such as the nature of the ligand,7
solvents,8 templates (or guests),9 and counterions,10 and so on.
Therefore, to understand the fine-drawn connection between
complex structures and the factors that affecting the framework
formation is still one of the key points for the rational design of
crystalline materials, and still seems to be a great challenge.
Although rigid pillar organic units are usually employed as
bridging ligands to build extended networks with metal ions,11
recently, there is an increasing interest to coordination architec-
tures using flexible bridging ligands,12 and various coordination
architectures with diverse structures and different types of
flexible bridging ligands have been reported, particularly, those
tion of the framework formations of flexible dithioether ligands
(as depicted in Chart 1) with AgI salts. Herein, we report a
systematic study of the self-assembly of eight structurally related
flexible dithioether ligands RS(CH2)nSR (R = ethyl or benzyl
group, n = 1–4) with AgClO4. Combining other reported AgI
complexes with related ligands, the relationships among complex
structures and the spacer length and terminal groups of such
ligands were also discussed.
Experimental
General
All the reagents for synthesis were commercially available and
used as received. Elemental analyses were performed on a
Perkin-Elmer 240C analyzer. IR spectra (KBr pellets) were
taken on a FT-IR 170SX (Nicolet) spectrometer. 1H NMR
spectra were measured on a Bruker AC-P500 spectrometer
(300 MHz) at 25 ◦C with tetramethylsilane as the internal refer-
12f
containing N- or O-donors, for example, bis(4-pyridyl). Such
studies have shown that the nature of the anions, terminal groups
and the spacer length of these bridging ligands play fundamental
roles in determining the structural types of the final assemblies.
However, systematic investigations on the dependence of such
factors with the framework formations of complexes are sill
comparatively rare.
1
ence. The dithioether ligands: bis(ethylthio)methane (La ), 1,2-
2
3
bis(ethylthio)ethane (La ), 1,3-bis(ethylthio)propane (La ), 1,4-
4
1
bis(ethylthio)butane (La ), bis(benzylthio)methane (Lb ), 1,2-
2
3
bis(benzylthio)ethane (Lb ), 1,3-bis(benzylthio)propane (Lb )
and 1,4-bis(benzylthio)butane (Lb ) were synthesized by the
† Electronic supplementary information (ESI) available: Experimental
and calculated powder diffraction patterns. See http://www.rsc.org/
suppdata/dt/b4/b416576b/
4
reaction of homologous bis(bromo)alkane with potassium
4 6 4
D a l t o n T r a n s . , 2 0 0 5 , 4 6 4 – 4 7 4
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
©

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2
[Ag(Lb )2]ClO4 2b. Yield: 69%. Anal. Calc. for C32H36S4-
AgClO4: C, 50.83; H, 4.80. Found: C, 50.61; H, 4.54%. IR
(KBr pellet, cm−1): 3027w, 2915w, 1601w, 1494m, 1453m, 1421w,
1241w, 1094s, 941w, 768w, 698m, 627m, 564w, 472w.
3
{[Ag(Lb )3/2(ClO4)1/2](ClO4)1/2}n 3b. Yield: 69%. Anal. Calc.
for C25.5H30S3AgClO4: C, 47.86; H, 4.72. Found: C, 47.61; H,
4.24%. IR (KBr pellet, cm−1): 3021, 2960w, 1637w, 1494m,
1453m, 1359s, 1200s, 1071s, 784m, 714s, 700s, 562w.
4
[Ag(Lb )3/2ClO4]n 4b. Yield: 59%. Anal. Calc. for C27H33S3-
AgClO4: C, 49.06; H, 5.03. Found: C, 48.96; H, 4.94%. IR (KBr
pellet, cm−1): 3018, 2918m, 1630w, 1494m, 1453m, 1282w, 1144s,
1092s, 769w, 700m, 628s, 566w.
CAUTION. Although we experienced no problems in this
work, perchlorate salts of metal complexes with organic ligands
are often explosive and should be handled with great caution.
X-Ray structure determination
Single-crystal X-ray diffraction measurements for all the com-
plexes were carried out on a Bruker Smart 1000 CCD diffrac-
tometer equipped with a graphite crystal monochromator at
298(2) K. The determination of unit cell parameters and
data collections were performed with Mo-Ka radiation (k =
Chart 1 Some flexible dithioether ligands involved in this paper.
˚
0.71073 A). Unit cell dimensions were obtained with least-
squares refinements. The program SAINT15 was used for integra-
tion of the diffraction profiles. All the structures were solved by
direct methods combining successive difference Fourier synthe-
ses using the SHELXS program of the SHELXTL package and
refined with SHELXL.16 The final refinement was performed
by full matrix least-squares methods with anisotropic thermal
parameters for non-hydrogen atoms on F2. The hydrogen atoms
were added theoretically, and riding on the concerned atoms and
refined with fixed thermal factors. The disorders of the ligands
or perchlorate were found in some complexes, and a suitable
site occupation separation was used for refinement in each case.
Especially, in 4a, there is imposed symmetry at the disordered
C12 and C16 sites, and the disordered atoms (C12 and C12ꢀ; C16
and C16ꢀ) are related by an inversion center in each case. For C16,
the refinement gives a cyclohexane-like ring. In 3b, perchlorate
ions are highly disordered and lie on high symmetry sites.
Although the relevant modes have been developed, attempts
for obtaining a perfect data are unsuccessful. In this text part
of disordered atoms/groups were omitted in drawing figures.
Crystallographic data and experimental details for structural
analyses are summarized in Table 1 and the selected bond lengths
and angles are listed in Table 2.
ethylthiolate (or benzylthiolate) according to the similar liter-
1
ature method.14 1H NMR (CDCl3) for La : d 3.70 (s, 2H, S–
2
CH2–S), 2.66 (q, 4H, MeCH2–S), 1.27 (t, 6H, Me); La : d 2.74
3
(s, 4H, CH2–S), 2.57 (q, 4H, MeCH2–S), 1.27 (t, 6H, Me); La :
d 2.63 (t, 4H, CH2–S), 2.55 (q, 4H, MeCH2–S), 1.88 (t, 2H,
4
CH2CH2–S), 1.26 (t, 6H, Me); La : d 2.57 (t, 4H, CH2–S), 2.53
(q, 4H, MeCH2–S), 1.68 (t, 4H, CH2CH2–S), 1.26 (t, 6H, Me);
1
Lb : d 7.22–7.31 (m, 10H, Ph), 3.84 (s, 4H, S–CH2–Ph), 3.37
2
(s, 2H, S–CH2–S); for Lb : d 7.22–7.34 (m, 10H, Ph), 3.68 (s,
3
4H, S–CH2–Ph), 2.56 (s, 4H, CH2–S); Lb : d 7.21–7.33 (m, 10H,
Ph), 3.66 (s, 4H, S–CH2–Ph), 2.46 (t, 4H, CH2–S), 1.80 (t, 2H,
4
CH2CH2–S); Lb : d 7.22–7.32 (m, 10H, Ph), 3.68 (s, 4H, S–CH2–
Ph), 2.37 (t, 4H, CH2–S), 1.61 (t, 4H, CH2CH2–S).
Syntheses of complexes
Colorless single crystals suitable for X-ray analyses for all
complexes were obtained by the similar method as described
below: to a solution of AgClO4·H2O (0.3 mmol) in acetone
(6 mL) was slowly added a chloroform solution (6 mL) of
ligand (0.6 mmol). The mixture was stirred for about 10 min
and filtered. Crystals were obtained by slow diffusion of ether
to above filtrate in the dark. All general characterizations are
carried out based upon the crystal samples.
CCDC reference numbers 231504–231511.
See http://www.rsc.org/suppdata/dt/b4/b416576b/ for cry-
stallographic data in CIF or other electronic format.
1
[Ag(La )3/2ClO4]n 1a. Yield: 71%. Anal. Calc. for C7.5H18S3-
AgClO4: C, 21.88; H, 4.41. Found: C, 21.41; H, 4.06%. IR (KBr
pellet, cm−1): 2967m, 2019w, 1633w, 1456m, 1382m, 1212m,
1097s, 838w, 782w, 729m, 624s.
Results and discussion
2
Synthesis and general characterization
[Ag2(La )2(ClO4)2]2 2a. Yield: 78%. Anal. Calc. for C12H28S4-
Ag2Cl2O8: C, 20.15; H, 3.95. Found: C, 19.97; H, 3.62%. IR (KBr
pellet, cm−1): 2966m, 2019w, 1624w, 1451w, 1376w, 1257w, 1094s,
941w, 716w, 628s.
All the complexes were obtained by the self-assembly of AgClO4
n
n
with bis(ethylthio)alkane (La ) or bis(benzylthio)alkane (Lb )
ligand in the similar reaction conditions. Although the same
ratio of Ag/L (1 : 2) was used in the procedures for synthesizing
all these complexes, that in the resulted products was found
to be different (1 : 1, 2 : 3 or 1 : 2). The elemental analyses
showed that the components of these complexes are consistent
with the results of crystal structures. The syntheses were repeated
for all the eight compounds with the reaction stoichiometric
ratio of the corresponding crystal structure, respectively, in order
to confirm if the resulted materials in such situation are the
same as the corresponding single crystals. The polycrystalline
compound was obtained by adding ether directly to the reaction
system. X-Ray powder diffraction results show that only 1a,
3a and 3b have the same diffraction patterns (see ESI†) to those
simulated by the crystal data of the corresponding complex. This
3
[AgLa ClO4]n 3a. Yield: 75%. Anal. Calc. for C7H16S2-
AgClO4: C, 22.62; H, 4.34. Found: C, 22.38; H, 4.09%. IR
(KBr pellet, cm−1):2964m, 2921m, 2017w, 1636w, 1450m, 1375w,
1254w, 1142s, 1094s, 839w, 783w, 628s.
4
{[Ag(La )2]ClO4}n 4a. Yield: 69%. Anal. Calc. for C16H36S4-
AgClO4: C, 34.07; H, 6.43. Found: C, 33.91; H, 6.14%. IR (KBr
pellet, cm−1): 2971m, 2020w, 1631w, 1457m, 1370m, 1251w,
1106s, 1093s, 724w, 621m.
1
[AgLb ClO4]2 1b. Yield: 81%. Anal. Calc. for C15H16S2-
AgClO4: C, 38.52; H, 3.45. Found: C, 38.31; H, 3.12%. IR
(KBr pellet, cm−1): 3027w, 2915w, 1628w, 1493m, 1453m, 1417w,
1242w, 1095s, 915w, 769w, 699m, 628m, 564w, 471w.
D a l t o n T r a n s . , 2 0 0 5 , 4 6 4 – 4 7 4
4 6 5

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◦
˚
Table 2 Selected bond lengths (A) and angles ( ) for complexes 1a–4b
1a
Ag(1)–S(1)
Ag(1)–O(1)
2.509(1) S(1)–Ag(1)–S(1A)
2.589(7) S(1)–Ag(1)–O(1)
117.84(2)
98.52(3)
2a
Ag(1)–S(1)
Ag(1)–S(4A)
Ag(2)–S(1)
Ag(2)–S(2)
Ag(2)–S(3)
Ag(2)–S(4)
Ag(1)–O(1)
Ag(1)–O(6A)
2.464(2) S(1)–Ag(1)–S(4A)
2.447(2) S(1)–Ag(2)–S(2)
2.632(2) S(1)–Ag(2)–S(3)
2.545(2) S(1)–Ag(2)–S(4)
2.520(2) S(2)–Ag(2)–S(3)
2.651(2) S(2)–Ag(2)–S(4)
2.648(5) S(3)–Ag(2)–S(4)
162.36(5)
82.54(5)
124.47(5)
115.12(5)
145.02(6)
106.22(5)
83.43(5)
2.67(2)
Ag(1)–S(1)–Ag(2)
Ag(2)–S(4)–Ag(1A)
125.48(6)
121.10(6)
3a
Ag(1)–S(1)
Ag(1)–S(1B)
Ag(1)–S(2A)
Ag(1)–O(3)
2.544(2) S(1)–Ag(1)–S(2A)
2.565(2) S(1)–Ag(1)–S(1B)
2.504(2) S(1)–Ag(1)–O(3)
125.85(8)
122.04(5)
99.6(4)
111.40(8)
92.7(7)
85.0(6)
120.20(8)
2.53(2)
S(2A)–Ag(1)–S(1B)
O(3)–Ag(1)–S(2A)
O(3)–Ag(1)–S(1B)
Ag(1)–S(1)–Ag(1C)
4a
Ag(1)–S(1)
Ag(1)–S(3)
Ag(1)–S(4)
Ag(1)–S(2A)
2.598(3) S(1)–Ag(1)–S(3)
2.607(3) S(1)–Ag(1)–S(4)
2.553(3) S(1)–Ag(1)–S(2A)
2.609(3) S(3)–Ag(1)–S(4)
S(3)–Ag(1)–S(2A)
105.7(1)
107.78(9)
113.0(1)
116.4(1)
100.6(1)
113.21(9)
S(4)–Ag(1)–S(2A)
1b
Ag(1)–S(1)
Ag(1)–S(2)
Ag(1)–Ag(1A)
Ag(1)–O(1)
Ag(1)–O(2B)
2.442(2) S(1)–Ag(1)–S(2)
166.65(5)
2.445(2)
3.036(1)
2.639(5)
2.639(6)
2b
Ag(1)–S(1)
Ag(1)–S(2)
Ag(1)–S(3)
Ag(1)–S(4)
2.604(1) S(1)–Ag(1)–S(2)
2.515(1) S(1)–Ag(1)–S(3)
2.523(1) S(1)–Ag(1)–S(4)
2.590(1) S(2)–Ag(1)–S(3)
S(2)–Ag(1)–S(4)
85.17(5)
110.93(4)
120.14(4)
141.27(4)
116.36(5)
86.58(5)
S(3)–Ag(1)–S(4)
3b
Ag(1)–S(1)
Ag(1)–O(1)
2.502(1) S(1)–Ag(1)–S(1A)
2.22(1)
119.766(5)
4b
Ag(1)–S(1)
Ag(1)–S(2)
Ag(1)–S(3)
Ag(1)–O(1)
2.509(2) S(1)–Ag(1)–S(2)
2.524(2) S(1)–Ag(1)–S(3)
2.512(2) S(2)–Ag(1)–S(3)
2.723(6)
110.82(6)
124.19(6)
122.56(5)
Symmetry codes: 1a, A: 1 − y, x − y + 1, z. 2a, A: 1 − x, 1 − y, 1 − z.
3a, A: x + 1, y, z; B: x + 1/2, 3/2 − y, −z; C: x − 1/2, 3/2 − y, −z. 4a,
A: 2 − x, y + 1/2, 1/2 − z. 1b, A: 1 − x, 1 − y, 1 − z; B: x, y − 1, z. 3b,
A: 2 − y, x − y + 1, z.
result shows that maybe the 1 : 2 ratio is suitable for obtaining
the corresponding crystals, but that the correct stoichiometry
may lead to the formation of other compounds. It should be
noted that some of these AgI complexes are not stable in light.
The difference between the diffraction patterns of the powder
samples and the crystal data of the same complex may also be
attributed to this instability.
IR spectra of the complexes are similar and show the
characteristic S–C vibrations at about 700 cm−1 and the existence
4 6 6
D a l t o n T r a n s . , 2 0 0 5 , 4 6 4 – 4 7 4

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of ClO4 (m 1071–1097 cm−1). All the complexes are moderately
highly disorder of ClO4−, the weak coordination interactions
between O atoms in one layer and AgI ions from adjacent layers
can not be established, however, they can be regarded as pillars
to sustain such layers. Thus, this type of layer packing gives
rise to a quasi-3-D framework and shows brick-wall structure
in the direction paralleling such layers. Space-filling views of
the structure reveal small channels that run parallel to the z axis.
Calculations from the X-ray structural parameters show that the
solvent-accessible void space in the channels is approximately
6.5%.17 The smallest diameter of these channels, after taking
−
sensitive to light, and are soluble in DMF and acetonitrile,
slightly soluble in acetone, ethanol and methanol but insoluble
in water.
Description of crystal structures
1
[Ag(La )3/2ClO4]n 1a, a 2-D (6,3) net. 1a has a 2-D layer
structure of (6,3) topology, with the AgI ions, related by a
three-fold axis equally coordinated to three S donors from three
1
−
distinct La , and an O atom of disordered ClO4 (Fig. 1(a))
The coordination geometry of AgI center can be described as
a regular triangle pyramid with three S donors lying in the
equatorial plane and one O atom in the apical position. The
˚
into account the van der Waals radii, is ca. 2.3 A.
2
[Ag2(La )2(ClO4)2]2 2a, a tetranuclear complex. 2a is a
2
tetranuclear molecule, consisting of tetranuclear [Ag2(La )2]2
−
˚
Ag–S and Ag–O bond lengths are 2.509(1) and 2.589(7) A,
cations and ClO4 anions which weakly coordinate to AgI
respectively, and the S–Ag–S angle is 117.84(2)◦. The AgI ion
ions (Fig. 2(a)), and the cation has a “hexagonal” tetranuclear
macrometallacyclic geometry with the crystallographic inver-
sion center located at the center of the molecule, and consists
˚
deviates from the S3 plane by 0.372(1) A due to the axial coordi-
nation of ClO4−. As shown in Fig. 1(b), in 1a each ligand links
two AgI through the S atoms and each AgI is bridged to three
neighboring AgI ions by La1 to form centrosymmetric hexagonal
of four AgI and four La ligands. In the macrometallacycle, two
2
pairs of AgI ions adopt different coordination modes and envi-
1
2
24-membered (AgLa )6 macrometallacyclic units (Fig. 1(c)), in
ronments. Ag1 is coordinated to two S donors from two La in
which six AgI atoms are located alternately up and down. The
central C atom (C3) of each ligand lies on a twofold axis. In
quasi-linear geometry with the S–Ag–S angle being 162.36(5)◦,
which deviates from 180◦ due to the weak coordination of ClO4
−
the macrometallacyclic unit the distance of adjacent AgI ions
(vide infra), and the Ag1–S1 and Ag1–S4A bond distances are
1
˚
˚
˚
is 6.475(2) A and the S · · · S distance in La is 3.012(3) A.
Eventually, the macrometallacyclic unit extends out along a and
b directions to form a 2-D (6,3) layer (Fig. 1(c)). In addition,
three ethyl groups of the La ligand and ClO4 around each
AgI are located at the same side of the layer and those around
adjacent AgI are at the opposite sides, which may help to reduce
the steric hindrance. The two S atoms of each ligand show R,S
(or S,R) configuration, but three around each AgI center are the
same S or R configuration.
Another particular feature of 1a is that the 2-D layers stack in
an ABAB alternating fashion with 30◦ turning around the three-
fold axis through AgI centers, but without offsetting each other,
and ClO4− is located between these layers (Fig. 1(d)). Due to the
2.464(2) and 2.447(2) A, respectively. While Ag2 has a highly
distorted tetrahedral coordination geometry formed by four S
2
donors from two chelating La ligands, and the Ag2–S bond
1
−
˚
distances lie between 2.520(2) and 2.651(2) A which are longer
than those of Ag1–S, but being normal for AgI complexes of
thioether ligands,18 andthe bondangles aroundAg2 center range
from 82.54(5) to 145.02(6)◦.
In 2a each ligand takes chelating and bridging coordination
roles, with the S donors exhibiting monodentate terminal and
l2-bridging coordination modes. As shown in Fig. 2(a), in the
cation unit, a pair of ligands coordinate to Ag2 atom in chelating
mode using its two S donors to form two five-membered rings
and simultaneously bridge Ag1 and Ag1A ions through one of
Fig. 1 (a) View of the coordination environment of AgI in 1a, (b) the ligand linking mode in 1a, (c) the 2-D (6,3) layer structure of 1a (the ethyl
groups were omitted for clarity) and (d) quasi-3-D framework perspective viewing along z-axis showing channels. Symmetry codes, A: 1 − y, x − y +
1, z; B: y − x, 1 − x, z; C: x − y + 1, 2 − y, 1/2 − z.
D a l t o n T r a n s . , 2 0 0 5 , 4 6 4 – 4 7 4
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and Ag2A ions of adjacent Ag4S4 units (Ag2–O7B = 3.044(9)
˚
A, symmetry code B: 1 − x, 1/2 + y, 1/2 − z) to form a 2-D
network along the bc plane. If the Ag4S4 entity could be regarded
−
as a “node” and the ClO4 as a “spacer”, the 2-D network can
be described as a (4,4) topology.
3
[AgLa ClO4]n 3a, a chiral helical chain. 3a is a chiral helical
3
chain polymer consisting of (AgLa ClO4) units (Fig. 3(a)), in
Fig. 2 (a) View of the tetranuclear structure of 2a and (b) 2-D (4,4)
−
network along the bc plane in 2a formed through ClO4 linking the
tetranuclear cations (the ethyl groups are omitted for clarity in (b)).
Symmetry code, A: 1 − x, 1 − y, 1 − z.
the S donors of each ligand in l2-S bridging coordination mode.
Similarly, the other pair of ligands coordinate to Ag2A and
bridge Ag1 and Ag1A ions. The chelating and bridging coordi-
nation give rise to a tetranuclear Ag4S4 ring entity, in which four
Ag atoms and four S atoms are coplanar, respectively, and the
dihedral angle between them is 10.69(5)◦. The intramolecular
˚
Ag · · · Ag separations are 4.531(1) A for Ag1 · · · Ag2, 4.441(1)
˚
˚
˚
A for Ag1 · · · Ag2A, 4.768(2) A for Ag1 · · · Ag1A and 7.600(2)
A for Ag2 · · · Ag2A, respectively. The S atoms of each La2 ligand
around Ag2 (or Ag2A) show R,S (or S,R) configuration, and
those around Ag1 (or Ag1A) are also R,S (or S,R). This type
of structure, and the coordination modes of the ligand in 1a are
unique for AgI complexes with bithioethers.
It is interesting that these tetranuclear cations are further
linked through weak coordination of Ag · · · O by disordered
−
2
ClO4 to form a 2-D sheet (Fig. 2(b)). In each [Ag2(La )2]2
−
molecule, two ClO4 anions weakly coordinate to Ag1 and
Ag1A ions in the periphery with the Ag1–O1 (Ag1A–O1A) and
˚
Ag1–O2 (Ag1A–O2A) distances of 2.648(5) and 3.080(6) A,
respectively. The other two also weakly coordinate to Ag1 and
Ag1A ions with Ag1–O5 = 2.93(2), Ag1–O6A = 2.67(2) and
Fig. 3 (a) View of the coordination environment of AgI in 3a, (b)
ꢀ
˚
Ag1A–O6 = 2.68(1) A in O–Cl–O bridging fashion to form an
side view of the 1-D helical chain showing pair of right-handed helical
3
eight-membered (–Ag–O–Cl–O)2 ring, then the other O atoms
(Ag–La –)n chains in 3a and (c) top view of the helical chain. Symmetry
−
(O7 and O7A) in the two ClO4 anions further link the Ag2
codes, A: x + 1, y, z; B: x + 1/2, 3/2 − y, −z.
4 6 8
D a l t o n T r a n s . , 2 0 0 5 , 4 6 4 – 4 7 4

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which the AgI ion is coordinated by three S donors of three
distinct La3 ligands and one O atom of ClO4−, showing highly dis-
torted tetrahedral (or distorted triangle pyramid) coordination
˚
geometry. The Ag1–O3 distance of 2.53(2) A lies in the normal
Ag–O bond length range,18 and the average length of Ag–S
˚
bonds [2.538(2) A] is also normal, but the Ag1–S1 bond distance
˚
˚
[2.544(2) A] is slightly longer than that of Ag1–S2A [2.504(2) A]
due to S1 adopting l2-bridging coordination mode while S2
adopts a monodentate terminal coordination mode (vide infra).
Three S–Ag–S bond angles range from 111.40(8) to 125.85(8)◦,
and the Ag is 0.123(1) A above the S3 coordination plane.
Similar to those in 2a, the S donors of the ligands La
I
˚
3
also adopt l2-bridging and monodentate terminal coordination
modes. The whole chain can be described as two single helical
chains bound together by l2-S donors (Fig. 3(b), (c)). In each sin-
gle chain, the ligands bridge AgI centers in bis-monodentate co-
3
ordination mode to form right-handed single helix (Ag–La –)n,
˚
which are intertwined themselves with a period of 7.506(2) A, viz.
the shortest intrachain Ag · · · Ag distance in the chain. Two such
helical single chains are linked together (in couple and slippage
along the chain) by l2-bridging S donors of ligands to form a
double chain. Interestingly, based on the l2-S bridging AgI ions,
a left-handed chiral helical chain entity (Ag–S–)n related by a 21
screw axis is also formed, simultaneously. In the whole helical
chain, the AgI ions arrange in two lines and the shortest distance
˚
is 4.429(1) A. It should also be pointed out that in the crystal
structure of 3a, such helical chains arrange parallel along the
crystallographic a axis, and the molecule crystallizes in chiral
P212121 space group. The origin of the chirality can probably be
explained as that in the chain, two S atoms of each ligand all
adopt S configuration when coordinated to AgI ions, therefore,
the resultant chain, as a whole, is also chiral.
4
{[Ag(La )2]ClO4}n 4a, a 2-D framework. 4a is 2-D coordi-
nation network containing cationic layers with left- and right-
−
handed single helical chains and ClO4 anions. As shown in
Fig. 4(a), each AgI center involves in a distorted tetrahedral
coordination geometry comprising four S donors from four
4
distinct La ligands with S–Ag–S bond angles ranging from
100.6(1) to 116.4(1)◦. The average Ag–S bond length of 2.592(3)
˚
A is slightly longer than those of the complexes 1a–3a, probably
due to the differences of the coordination geometries.
At first sight, in the cationic layer, each ligand bridges two
adjacent four-coordinate AgI centers to form 28-membered
4
twisted rectangular macrometallacycles, Ag4(La )4, and such
repeating units are extended along the a and b directions to form
a 2-D network. With a delicate observation, we can find that the
ligands play two roles in the 2-D network (Fig. 4(b), (c)). First,
half of the ligands link AgI ions to form left- and right-handed
helical chains running along the b direction. In each chain AgI
ions are arranged in two lines and two AgI and two ligands finish
˚
one whorl with the screw-pitch of 9.76(1) A. Then these left- and
right-handed helical chains are further bridged alternately by the
other half of the ligands to form an achiral 2-D layer, in which the
shortest inter-chain (helical single chain) Ag · · · Ag distances are
Fig. 4 (a) View of the coordination environment of AgI in 4a, (b)
the 2-D network of 4a showing the two types of ligand linkage modes
and left- and right-handed helixes and (c) view of the 2-D layer along
another direction (the ethyl groups were omitted for clarity in (a) and
(b)). Symmetry codes, A: 2 − x, y + 1/2, 1/2 − z; B: 1 − x, 2 − y, −z.
4
˚
9.621(7) A. Similarly to those in 1a, the two S atoms of one La
ligand adopt R,S (or S,R) configuration, while the four around
each AgI center are the same S or R configuration. In addition,
in the crystal, the 2-D layers stack face-to-face along the c axis
without offsetting, however no channel is left in the stacking
direction because of the existence of the ethyl groups of ligands
and the included ClO4−, which is different from that in other
2-D dithioether AgI complexes reported in this work.
Although many chiral helix complexes have been reported,19
in 3a and 4a, the combination of helixes to form complicated
chiral or meso structures are rare and interesting in chiral
coordination polymers.
Fig. 5(a), in the complex cation related by a crystallographic
center of symmetry, each AgI is two-coordinated to two S
donors from two ligands in an approximate linear geometry,
and two AgI ions are bridged equivalently by two ligands which
adopt a bis-monodentate coordination mode to form a unique
box-like dimeric entity. Two Ag–S bond distances are almost
equivalent and shorter than those in other three- or four-
coordinate thioether AgI complexes in this work (see Table 2).
The S–Ag–S bond angle is 166.65(5)◦, which deviates from 180◦
due to the weak coordination of two perchlorate O atoms to
1
[AgLb ClO4]2 1b, a dinuclear complex. The structure of
1
complex 1b consists of a (AgLb )22+ cation and two ClO4− anions
which weakly coordinate to the central AgI ions. As shown in
D a l t o n T r a n s . , 2 0 0 5 , 4 6 4 – 4 7 4
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and the AgI center is coordinated by four S donors of two
2
Lb ligands. The four Ag–S bond distances can be divided
˚
into two groups: 2.604(1), 2.590(1) and 2.515(1), 2.523(1) A,
˚
with the average value of 2.558(1) A, being in the normal
range expected for such coordination bonds.18 The coordination
geometry around each AgI center can be described as a distorted
tetrahedron with the S–Ag–S angles ranging from 85.17(5) to
141.27(4)◦. The angle between the two coordination planes
defined by S1–Ag1–S2 and S3–Ag1–S4 is 76.45(5)◦. In 2b, two
ligands bond one AgI center in bidentate coordination mode to
form two five-membered chelate rings. It is interesting that the
two ligands show different configurations, cis and trans, based
on the two phenyl rings of each ligand locating at the same side
or the opposite side of their corresponding coordination planes
(S–Ag–S). Further, the coordinated S atoms of two ligands have
different configuration, R,S for one ligand (cis), and S,S for the
other one (trans).
Fig. 5 (a) View of the dinuclear cationic structure of 1b and (b) 1-D
−
chain formed by ClO4 linking the dinuclear cations. Symmetry codes,
A: 1 − x, 1 − y, 1 − z; B: x, y − 1, z.
the central AgI ion, with the Ag–O distances being 2.639(5) and
˚
2.639(6) A for Ag1–O1 and Ag1–O2B, respectively. It should
be noted that in the dinuclear unit, the Ag · · · Ag distance of
˚
˚
3.036(1) A lies in the range (2.86–3.22 A) found in similar
systems,20 showing weak ligand-sustained Ag–Ag interaction.
In addition, in the cationic dimer the coordinated S atoms show
S,S configuration for one ligand and R,R for the other, and two
phenyl groups reside in the same side of each S–C–S skeleton.
This arrangement may help to decrease the space hindrance.
Another interesting point is the presence of weak coordination
−
linkages between such dinuclear cations and ClO4 anions. As
shown in Fig. 5(b), ClO4 anions link the dinuclear units in
−
bidentate bridging mode (O–Cl–O) through the weak coordina-
tion of O atoms to the central AgI ions, forming a 1-D chain,
˚
in which the intermolecular Ag · · · Ag distance is 4.047(2) A. In
addition, the intermolecular S · · · S, S · · · Cl and S · · · Ag weak
interactions are also observed.
2
[Ag(Lb )2]ClO4 2b, a mononuclear complex. Complex 2b
consists of discrete [Ag(Lb )2]+ cations (Fig. 6) and ClO4− anions,
2
Fig. 7 (a) View of the coordination environment of AgI and the
ligand linking mode, (b) 2-D (6,3) layer structure of 3b and (c) 3-D
−
framework showing ClO4 linkages (the benzyl groups were omitted in
(c)). Symmetry codes: A: 2 − y, x − y + 1, z; B: y − x + 1, 2 − x, z.
Fig. 6 The cationic structure of 2b.
4 7 0
D a l t o n T r a n s . , 2 0 0 5 , 4 6 4 – 4 7 4

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3
3
is also interesting that when AgNO3 reacted with Lb under
{[Ag(Lb )3/2(ClO4)1/2](ClO4)1/2}n 3b, a 3-D framework. Com-
−
similar reaction conditions, the resultant complex has the same
structural features as 3b, except for different anions. This result
reveals that the anions do not have an obvious influence on the
plex 3b has a 3-D framework structure constructed by ClO4
bridging cationic 2-D (6,3) layers [Ag(Lb )3/2]n+, which are similar
3
12o
to those in 1a. The AgI center, with a threefold axis passing
structures of the AgI complexes with this ligand.
through it, is coordinated equivalently to three S donors from
three distinct Lb ligands in the equatorial positions and an O
3
4
−
[Ag(Lb )3/2ClO4]n 4b, a 1-D single, double-bridging chain. 4b
atom of disordered ClO4 ions in the axial position (Fig. 7(a)).
−
Thus, the AgI ion resides in a trigonal pyramid environment
with the Ag–S and Ag–O bond lengths of 2.502(1) and 2.22(1)
consists of 1-D single, double-bridging chain cations and ClO4
anions. The AgI ion is trigonally coordinated to three S donors
4
◦
˚
from three distinct Lb ligands with Ag–S bond lengths of
2.524(2) A (Ag1–S2) and 2.512(2) A (Ag1–S3) for the double-
bridging unit and 2.509(2) A (Ag1–S1) for the single-bridging
A, respectively, and the S–Ag–S bond angle of 119.766(5) (near
120◦). In the cationic layer of 3b each ligand links two AgI centers
through two S donors in bis-monodentate bridging mode to
˚
˚
˚
3
one (Fig. 8(a)). The sum of three S–Ag–S bond angles is
form centrosymmetric 36-membered [Ag6(Lb )6] macrometalla-
357.57(6)◦, slightly deviating from 360◦ of the trigonal plane due
cyclic units, in which six AgI ions are located alternately up and
down. As in 1a, the central C atom (C9) of the ligand lies on a
twofold axis. In the macrometallacycle, the distance of adjacent
to one O atom of ClO4− weakly coordinating to the AgI ion [the
I
˚
Ag1–O1 distance is 2.723(6) A]. In 4b a pair of Ag ions are linked
by two bridging Lb ligands to form binuclear 14-membered
4
I
3
˚
Ag ions is 9.057(2) A and the S · · · S distance in Lb is 5.545(2)
4
4
˚
macrometallacyclic units (AgLb )2. Adjacent (AgLb )2 units
are further linked by other ligands in single-bridging fashion
to result in a single, double-bridging chain (Fig. 8(b)). The
Ag · · · Ag distances within the ring unit and in single bridge
A. Eventually, the macrometallacycle extends out in a and b
directions to form a 2-D (6,3) net (Fig. 7(b)) in which the benzyl
groups of ligands are located alternately up and down the layer
probably for reducing the steric hindrance. Three benzyl groups
around one AgI center lie in the same side of the whole layer
and the dihedral angle between them is 77.8(2)◦. Each ligand
shows R,S (or S,R) configuration based on its two coordination
S atoms.
˚
one are 7.294(3) and 8.626(3) A, respectively. The two S atoms
of each one ligand show S,R (or S,R) configuration for all of
them. In addition, in the crystal packing, such 1-D chains are
arranged paralleling to each other along the crystallographic
[1/2 0 1] direction.
−
In 3b, the ClO4 ions are highly disordered and are located
in the symmetry point, with half residing in the hexagonal
3
[Ag6(Lb )6] macrometallacyclic cavities of each layer, which may
Discussion
act as a template, and the other half link such layers to form
a 3-D framework (Fig. 7(c)). It should also be noted that in
The structural differences of 1a–4b in the solid state, may be
attributed to the differences of the spacer length and terminal
groups of such ligands. These results further confirm that the
spacers and terminal groups of ligands have great influence on
−
3b, the 2-D layers linked by ClO4 ions stack in an ABC
sequence along the c axis, and the face-to-face stacking of
such sheets does not produce substantial channels viewed down
the stacking direction. This is different from that in 1a. It
I
12h–o
the structures of their Ag complexes.
Table 3 summarizes
Fig. 8 (a) View of the coordination environment of AgI and (b) 1-D single, double-bridging chain structure of 4b. Symmetry codes: A: −x, −y, −z;
B: 1 − x, − y, 1 − z.
D a l t o n T r a n s . , 2 0 0 5 , 4 6 4 – 4 7 4
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4 7 2
D a l t o n T r a n s . , 2 0 0 5 , 4 6 4 – 4 7 4

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the basic structural parameters and features for four series
of the complexes with structurally related dithioether ligands
(Chart 1), which helps to examine the effects of some alterable
factors on the structures of such complexes. The structural
differences of such complexes imply that the flexible –(CH2)n–
backbone can allow the ligands to rearrange so as to minimize
the steric hindrance when coordinated to metal ions, leading
to the conformational variation of such ligands to result in the
structural diversities of their complexes. It should also be noted
that the coordination behavior of the ligands with AgClO4 is
flexible and diverse. The S atom in thioether ligands has two
lone electron pairs, which can take part in coordination to
metal ions. In these complexes the S donors adopt monodentate
and l2-S bridging modes, and the former is prior to the latter,
probably for reducing the steric hindrance. In addition, the Ag–
S bond distance increases with the increasing of the number of
the coordinated S atom around AgI (Fig. 9).
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Fig. 9 Graphic presentation of the relationship between AgI coordina-
tion number with S and Ag–S bond length in the twenty complexes.
In conclusion, eight dithioether–AgI metal–organic architec-
tures with different structures have been constructed by self-
assembly of AgClO4 with two series of dithioether ligands that
are related in structure, and a variety of coordination modes
of AgI and the ligands were observed. Comparison with the
structures of other AgClO4 complexes of closely related ligands
further indicates that the structures of such complexes could be
adjusted by the ligand spacers and terminal groups. Such results
present a feasible way for varying the structures of complexes by
modifying the ligand spacers and terminal groups. In addition,
other factors such as the diversity of the AgI coordination, the
flexibility of the ligands, and the variable coordination modes of
S donors also play important roles in affecting the framework
formations of such complexes.
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Acknowledgements
This work was financially supported by the National Sci-
ence Funds for Distinguished Young Scholars of China (No.
20225101) and the National Natural Science Foundation of
China (No. 20373028).
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