Silver(I) supramolecular complexes generated from isophorone-based ligands: Crystal structures and enhanced nonlinear optical properties through metal complexation

Article abstract of DOI:10.1039/c3dt52364k

By self-assembly of (E)-2-(3-(4-(1H-imidazol-1-yl)styryl)-5,5- dimethylcyclohex-2-enylidene)malononitrile (L¹) and (E)-2-(3-(4-(1H-1,2,4-triazol-1-yl)styryl)-5,5-dimethylcyclohex-2-enylidene) malononitrile (L²) with silver(i) salts, eight new complexes, namely AgL¹₂ClO₄ (1), AgL¹ ₂NO₃ (2), [AgL¹₂NO ₃]·C₆H₆ (3), [AgL¹ ₂OOCCF₃]·C₆H₆ (4), [AgL ¹₂PF₆]·C₆H₆ (5), AgL²₂NO₃ (6), [AgL²OOCCF ₃]₂ (7) and AgL²₂PF₆ (8), are presented along with an analysis of their structural features. The structures are built up through the combination of coordination bonds, Ag...π, Ag...F (or O), hydrogen bonding, and π...π stacking interactions to generate new supramolecular architectures. We observed the formation of two-dimensional coordination polymers for complex 7. Solvent benzene molecules and anions are dispersed in the supramolecular structure and play a vital role in building the supramolecular structures of the complexes. The nonlinear optical (NLO) properties of the complexes were investigated using the Z-scan technique and complexes 1, 2, 3, 4 and 7 show obviously nonlinear absorption compared with ligands (L¹ and L²). The Royal Society of Chemistry 2014.

Full text of DOI:10.1039/c3dt52364k

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Silver(I) supramolecular complexes generated from
isophorone-based ligands: crystal structures and
enhanced nonlinear optical properties through
metal complexation†
Cite this: Dalton Trans., 2014, 43,
1139
Zheng Zheng,a Zhi-Peng Yu,a Ming-Di Yang,a Feng Jin,*a,b Li-Na Ye,a Min Fang,a
Hong-Ping Zhou,*a Jie-Ying Wua and Yu-Peng Tiana,c
By self-assembly of (E)-2-(3-(4-(1H-imidazol-1-yl)styryl)-5,5-dimethylcyclohex-2-enylidene)malono-
nitrile (L1) and (E)-2-(3-(4-(1H-1,2,4-triazol-1-yl)styryl)-5,5-dimethylcyclohex-2-enylidene)malononitrile
(L2) with silver(I) salts, eight new complexes, namely AgL12ClO4 (1), AgL12NO3 (2), [AgL12NO3]·C6H6 (3),
[AgL12OOCCF3]·C6H6 (4), [AgL12PF6]·C6H6 (5), AgL22NO3 (6), [AgL2OOCCF3]2 (7) and AgL22PF6 (8), are
presented along with an analysis of their structural features. The structures are built up through the com-
bination of coordination bonds, Ag⋯π, Ag⋯F (or O), hydrogen bonding, and π⋯π stacking interactions to
generate new supramolecular architectures. We observed the formation of two-dimensional coordination
polymers for complex 7. Solvent benzene molecules and anions are dispersed in the supramolecular
structure and play a vital role in building the supramolecular structures of the complexes. The nonlinear
optical (NLO) properties of the complexes were investigated using the Z-scan technique and complexes
1, 2, 3, 4 and 7 show obviously nonlinear absorption compared with ligands (L1 and L2).
Received 23rd August 2013,
Accepted 25th September 2013
DOI: 10.1039/c3dt52364k
www.rsc.org/dalton
complexes, owing to the complicated influencing factors of the
assembly reactions, such as the organic ligands, anions, the
Introduction
In recent years, the design and synthesis of metal–organic nature of transition metal ions and the experimental con-
complexes based on strong coordinate bonds and multiple ditions like solvent, metal-to-ligand ratio and the reaction
weak non-covalent forces have become one of the most active temperature.
fields in coordination chemistry and crystal engineering due
The design and synthesis of new organic ligands is the key
to their fascinating structural features and interesting pro- approach for construction of metal–organic complexes with
perties.1 Many supramolecular coordination complexes with desired structures and properties.4 At present, it is still a chal-
specific topologies and excellent properties have been syn- lenge to synthesize new organic ligands in supramolecular
thesized by assembly of metal salts and organic ligands.2 architectures because of the synthetic difficulties involved. In
Hence, in order to synthesize specific coordination complexes, designing coordination complexes, imidazolyl, triazolyl and
many strategies have been studied and used by researchers.3 cyano derivatives have been widely used as ligands due to their
However, at present it is still a challenge for chemists to ability to coordinate to several metal centers in various
predict and control the structures of such metal–organic modes.5 Two new multidentate ligands based on isophorone,
namely, (E)-2-(3-(4-(1H-imidazol-1-yl)styryl)-5,5-dimethylcyclo-
hex-2-enylidene)malononitrile (L1) and (E)-2-(3-(4-(1H-1,2,4-
aCollege of Chemistry and Chemical Engineering, Anhui University, Key Laboratory of
triazol-1-yl)styryl)-5,5-dimethylcyclohex-2-enylidene)malononi-
Functional Inorganic Materials Chemistry of Anhui Province, 230601 Hefei,
trile (L2)6 have been used to construct new coordination com-
P. R. China. E-mail: zhpzhp@263.net; Fax: +86-551-5107342; Tel: +86-551-5108151
bDepartment of Chemistry, Fuyang Normal College, Fuyang 236041, P. R. China
plexes with specific structures and properties. On the other
hand, Ag(I), as a soft Lewis acid, may adopt various coordi-
nation modes such as linear, trigonal planar, trigonal pyrami-
dal and tetrahedral coordination geometries.7 So, the
combination of rigid organic spacers (L1 and L2) and Ag(I)
metal ions would allow the formation of fascinating structural
cState Key Laboratory of Coordination Chemistry, Nanjing University,
Nanjing 210093, P. R. China
†Electronic supplementary information (ESI) available: Synthetic route to the
ligands, synthesis of ligands, the open and closed aperture Z-scan data. CCDC
917019–917026. For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/c3dt52364k
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parameters, data collections and refinements for the com-
plexes are summarized in Table 1, and selected bond distances
and angles are listed in Table 2.
Synthesis of the complexes
AgL1 ClO4 (1). L1 (0.340 g, 1 mmol) in 25 mL of dichloro-
2
methane was added into a 50 mL colorimeter tube and care-
fully layered with a clear benzene solution (25 mL) of
AgClO4·H2O (0.112 g, 0.5 mmol). Yellow, needle-like crystals
suitable for single crystal X-ray diffraction were obtained by
slow interlayer diffusion. Yield: 0.32 g (72%). Anal. Calc. for
C44H40AgClN8O4: C, 59.50; H, 4.54; N, 12.62. Found: C, 59.32;
H, 4.49; N, 12.67%. IR ν (cm−1): 3133 (m), 2948 (m), 2926 (m),
2869 (w), 2218 (s, –CuN), 1563 (s), 1519 (s), 1398 (w), 1332 (s),
1308 (m), 1188 (m), 1085 (s), 962 (m), 854 (m), 818 (m).
Scheme 1 The coordination modes of ligands L1 and L2 in complexes
1–8.
diversities and interesting properties. Besides the ligand and
metal centre, the anions, as charge-balance components, can
adjust the topologies and properties of complexes through
different coordinate bonds or non-covalent interactions.8,9
Thus, when designing the coordination-driven architectures,
the roles of the metal centre, anion, solvent and ligand all
need to be considered. In this study, the syntheses and struc-
tures of eight novel Ag(I) complexes based on L1 or L2 and
AgL1 NO3 (2). L1 (0.340 g, 1 mmol) in 25 mL of dichloro-
2
methane was added into a 50 mL colorimeter tube and care-
fully layered with a clear benzene solution (25 mL) of AgNO3
(0.085 g, 0.5 mmol). Yellow, needle-like crystals suitable for
single crystal X-ray diffraction were obtained by slow interlayer
diffusion. Yield: 0.28 g (66%). Anal. Calc. for C44H40AgN9O3:
C, 62.12; H, 4.74; N, 14.82. Found: C, 61.80; H, 4.69; N,
14.95%. IR ν (cm−1): 3121 (m), 2951 (m), 2926 (m), 2868 (w),
2217 (s, –CuN), 1565 (s), 1520 (s), 1384 (s), 1339 (s), 1305 (s),
1186 (m), 1130 (m), 1063 (s), 960 (s), 852 (m), 817 (m).
−
various Ag(I)X salts (X = ClO4−, NO3−, OOCCF3 and PF6−) are
described (Scheme 1). The third-order nonlinear optical (NLO)
properties were measured by the Z-scan method. The results
indicate that the two-photon absorption (TPA) coefficient β
and TPA cross section σ of complexes 1, 2, 3, 4 and 7 are
larger than those of complexes 5, 6, 8 and free ligands (L1 or
L2). The detailed structure–properties relationships are
discussed.
[AgL1 NO3]·C6H6 (3). L1 (0.340 g, 1 mmol) in 25 mL of
2
dichloromethane was added into a 50 mL colorimeter tube
and carefully layered with a clear methanol and benzene
mixed solution (25 mL) of AgNO3 (0.085 g, 0.5 mmol). Yellow,
needle-like crystals suitable for single crystal X-ray diffraction
were obtained by slow interlayer diffusion. Yield: 0.38 g (82%).
Anal. Calc. for C50H46AgN9O3: C, 64.66; H, 4.99; N, 13.57.
Found: C, 64.56; H, 5.03; N, 13.50%. IR ν (cm−1): 3127 (m),
2955 (m), 2925 (m), 2868 (w), 2219 (s, –CuN), 1562 (s),
1520 (s), 1384 (s), 1326 (s), 1278 (s), 1156 (m), 1051 (w), 972 (s),
851 (m), 813 (m).
Experimental section
General procedure
All commercially available chemicals and solvents are of
reagent grade and were used as received without further purifi-
cation. Elemental analyses were carried out on Perkin-Elmer
240 analyzer. IR spectra were recorded with a Nicolet FT-IR
NEXUS 870 spectrometer (KBr discs) in the 4000–400 cm−1
region.
Complexes 4–8 were prepared by a similar procedure.
A clear acetonitrile and benzene mixed solution (25 mL) of the
−
−
−
silver salt AgX (0.5 mmol, X = OOCCF3 4, 7, PF6 5, NO3 6,
ClO4 7,) was carefully layered onto a solution of L1 or L2
−
(0.341 g, 1 mmol) in dichloromethane (25 mL). Single crystals
of 4–8 suitable for single crystal X-ray diffraction analyses were
obtained by slow interlayer diffusion.
X-ray crystallography and structure solution
The X-ray diffraction measurements were performed on a
[AgL1 OOCCF3]·C6H6 (4). Yield: 0.33 g (67%). Anal. Calc. for
2
Bruker SMART CCD area detector using graphite monochro- C52H46AgF3N8O2: C, 63.74; H, 4.73; N, 11.44. Found: C, 63.58;
mated MoKα radiation (λ = 0.71069 Å) at 298(2) K. Intensity H, 4.81; N, 11.38%. IR ν (cm−1): 3125 (m), 2949 (m), 2926 (m),
data were collected in the variable ω-scan mode. The structures 2870 (w), 2217 (s, –CuN), 1688 (s), 1564 (s), 1519 (s), 1398 (w),
were solved by direct methods and difference Fourier synth- 1332 (m), 1308 (m), 1193 (m), 1129 (m), 1061 (s), 962 (s),
eses. The non-hydrogen atoms were refined anisotropically 854 (m), 817 (m).
and hydrogen atoms were introduced geometrically. Calcu-
[AgL1 PF6]·C6H6 (5). Yield: 0.38 g (75%). Anal. Calc. for
2
lations were performed with the SHELXTL-97 program C50H46AgF6N8P: C, 59.35; H, 4.58; N, 11.07. Found: C, 59.54;
package. Crystallographic data (excluding structure factors) for H, 4.39; N, 11.02%. IR ν (cm−1): 3154 (m), 2949 (m), 2925 (m),
the structures reported in this paper have been deposited with 2870 (w), 2218 (s, –CuN), 1564 (s), 1520 (s), 1398 (w), 1332 (m),
the Cambridge Crystallographic Data Centre as supplementary 1308 (m), 1189 (m), 1131 (m), 1064 (m), 964 (m), 841 (s).
publication no. CCDC: 917019, 917020, 917021, 917022,
AgL2 NO3 (6). Yield: 0.33
g
(78%). Anal. Calc. for
2
917023, 917024, 917025, 917026. Details of the crystal C42H38AgN11O3: C, 59.16; H, 4.49; N, 18.07. Found: C, 59.01; H,
1140 | Dalton Trans., 2014, 43, 1139–1150
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Paper
Table 1 Crystallographic data for 1–8
1
2
3
4
Empirical formula
Formula weight
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C
44H40AgClN8O4
C44H40AgN9O3
850.72
Monoclinic
P21/c
7.727(5)
32.015(5)
8.917(5)
90
112.829(5)
90
2033.1(18)
2
C50H46AgN9O3
928.83
Triclinic
ˉ
P1
6.991(14)
13.22(3)
13.23(3)
80.11(2)
81.34(2)
77.57(2)
1168(4)
1
C52H46AgF3N8O2
979.84
Triclinic
ˉ
P1
9.667(5)
11.899(5)
21.743(5)
93.227(5)
99.083(5)
100.103(5)
2422.3(17)
2
888.16
Triclinic
ˉ
P1
9.556(5)
11.468(5)
22.267(5)
93.896(5)
98.182(5)
100.288(5)
2365.6(17)
2
γ [°]
V [Å3]
Z
T [K]
298(2)
1.247
0.529
1.81–25.00
16 709
298(2)
1.390
0.547
1.27–25.00
14 283
3572
293(2)
1.320
0.483
1.57–25.00
8274
4059
298(2)
1.343
0.476
0.95–25.00
17 293
Dcalcd [g cm−3
]
μ [mm−1
θ Range [°]
Total no. data
]
No. unique data
8225
8460
No. params refined
R1
wR2
GOF
572
306
303
599
0.0880
0.2129
1.025
0.0524
0.1542
1.038
0.0459
0.1199
1.057
0.0686
0.2099
1.020
5
6
7
8
Empirical formula
Formula weight
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C
50H40AgF6N8P
C42H38AgN11O3
852.70
Monoclinic
C2/c
26.621(5)
7.851(5)
18.755(5)
90
92.618(5)
90
3916(3)
4
C46H38Ag2F6N10O4
1124.60
Triclinic
ˉ
P1
10.750(5)
12.813(5)
20.012(5)
73.540(5)
80.240(5)
65.257(5)
2396.7(16)
2
C42H38AgF6N10
935.66
Monoclinic
C2/c
26.768(5)
7.990(5)
19.600(5)
90
96.028(5)
90
4169(3)
4
P
1005.74
Triclinic
ˉ
P1
9.738(2)
11.756(2)
21.462(4)
94.268(3)
96.334(3)
98.170(3)
2407.1(9)
2
γ [°]
V [Å3]
Z
T [K]
298(2)
1.388
0.518
1.76–25.00
17 215
8383
298(2)
1.446
0.570
1.53–25.00
13 435
3445
298(2)
1.558
0.894
1.06–25.00
16 562
298(2)
1.491
0.593
1.53–25.00
14 264
3669
Dcalcd [g cm−3
]
μ [mm−1
θ Range [°]
Total no. data
]
No. unique data
8307
No. params refined
R1
wR2
GOF
599
261
617
274
0.0688
0.1746
1.049
0.0389
0.1121
1.002
0.0614
0.1649
1.063
0.0351
0.0965
1.025
4.56; N, 17.95%. IR ν (cm−1): 3128 (m), 2956 (m), 2925 (m),
2869 (w), 2218 (s, –CuN), 1561 (s), 1514 (s), 1384 (s), 1319 (s),
1279 (m), 1158 (m), 972 (s), 850 (m).
Results and discussion
Synthesis and structural analysis
[AgL2OOCCF3]2 (7). Yield: 0.20 g (71%). Anal. Calc. for Compounds 1–8 were obtained as supramolecular complexes
C46H38Ag2F6N10O4: C, 49.13; H, 3.41; N, 12.45. Found: C, by combination of L1 or L2 with different inorganic Ag(I) salts.
48.97; H, 3.52; N, 12.21%. IR ν (cm−1): 3084 (w), 2950 (m), Well-shaped X-ray quality crystals of 1–8 were obtained by
2919 (m), 2870 (w), 2218 (s, –CuN), 1675 (s), 1563 (s), 1522 (s), direct metal–ligand assembly in different solvents. As a result,
1416 (m), 1330 (m), 1278 (m), 1205 (s), 1139 (s), 973 (s), complexes 1 and 2 were isolated from CH2Cl2–C6H6, and 3 was
857 (m).
AgL2 PF6 (8). Yield: 0.37
isolated from CH2Cl2–CH3OH–C6H6, whereas 4–8 were isolated
(80%). Anal. Calc. for from CH2Cl2–CH3CN–C6H6. All eight complexes were fully
g
2
C42H38AgF6N10P: C, 53.91; H, 4.09; N, 14.97. Found: C, 53.72; characterized by IR spectra and elemental analysis. Compared
H, 4.24; N, 14.73%. IR ν (cm−1): 3162 (m), 2950 (m), 2927 (m), to ligand L1, L2 is endowed with more structural potential. The
2869 (w), 2217 (s, –CuN), 1564 (s), 1523 (s), 1399 (m), 1325 (s), two coordinating sites on the triazole ring could serve as an
1289 (m), 1230 (w), 1154 (m), 976 (s), 845 (m).
additional coordinating donors compared with L1, which is
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Table 2 Selected bond lengths (Å) and angles (°) for 1–8
[C22H20N4]2·AgClO4 (1)
Ag(1)–N(4)
2.083(6)
2.117(3)
2.186(5)
Ag(1)–N(5)
Ag(1)–N(4)A
Ag(1)–N(1)A
2.103(6)
2.117(3)
2.186(5)
N(4)–Ag(1)–N(5)
N(4)A–Ag(1)–N(4)
N(1)A–Ag(1)–N(1)
178.9(3)
[C22H20N4]2·AgNO3 (2)
Ag(1)–N(4)
180.000(1)
180.00(14)
[C22H20N4]2·AgNO3·C6H6 (3)
Ag(1)–N(1)
Ag(1)–N(5)
2.110(4)
Ag(1)–O(1)
2.552(6)
N(4)–Ag(1)–N(5)
[C22H20N4]2·AgPF6·C6H6 (5)
Ag(1)–N(4)
[C21H19N5]2·AgNO3 (6)
Ag(1)–N(1)
170.24(16)
2.072(5)
2.120(2)
N(4)–Ag(1)–O(1)
91.59(18)
N(5)–Ag(1)–O(1)
97.74(18)
Ag(1)–N(5)
2.090(5)
2.120(2)
N(4)–Ag(1)–N(5)
N(1)–Ag(1)–N(1)A
175.4(2)
Ag(1)–N(1)A
166.12(13)
[C21H19N5]2·[AgOOCCF3]2 (7)
Ag(1)–N(6)
Ag(2)–O(2)
2.144(4)
2.304(5)
2.403(4)
85.75(15)
111.2(3)
111.2(2)
Ag(1)–N(5)
Ag(2)–O(4)
N(6)–Ag(1)–N(5)
O(2)–Ag(2)–O(4)
O(2)–Ag(2)–N(4)
2.171(4)
2.309(5)
167.74(14)
121.65(19)
114.45(18)
Ag(1)–O(1)
Ag(2)–N(2)
N(6)–Ag(1)–O(1)
O(2)–Ag(2)–N(2)
O(4)–Ag(2)–N(4)
2.501(4)
2.351(7)
106.51(15)
111.9(3)
83.21(15)
Ag(2)–N(4)
N(5)–Ag(1)–O(1)
O(4)–Ag(2)–N(2)
N(2)–Ag(2)–N(4)
[C21H19N5]2·AgPF6 (8)
Ag(1)–N(5)
2.114(2)
Ag(1)–N(5)A
2.114(2)
N(5)–Ag(1)–N(5)A
175.44(13)
one of the most important factors in control of the polymeric Crystal structure of complexes 1–5 based on L1
motifs. Furthermore, in complex 7, it is worthwhile to point
out that the cyano of ligand has the ability to coordinate Single crystal X-ray diffraction analyses provide direct evidence
Ag(I).5c In these Ag(I) compounds, different coordination for the structure of the complexes, and the results showed that
modes of triazole-containing ligand L2 were observed, which 1, 3, 4, 5 crystallize in the same triclinic space group P1
ˉ
result in the polymeric structure of complex 7 not achievable (Table 1), and have similar supramolecular structures. As
by other rigid linear organic spacers. In this paper, the crystal shown in Fig. 1a, 3a–5a, L1 adopts the trans-conformation to
structures were divided into two groups with different ligands: bind Ag(I) ions with two imidazolyl nitrogen atoms from two
L1 (1–5) and L2 (6–8), respectively, to discuss the structures of different molecules in 1, 3, 4 and 5. The bond angle of N–Ag–N
the silver complexes.
is 178.9(3)° for 1, 180.00(14)° for 3, 170.24(16)° for 4 and
Fig. 1 (a) ORTEP drawing of 1 with the ellipsoids drawn at the 30% probability level. (b) The 1D chain structure of complex 1 formed by multiple
C–H⋯O hydrogen bonding and Ag⋯O interactions. (c) The 2D layer structure of complex 1 formed by multiple C–H⋯O hydrogen bonding,
Ag⋯π interactions and C–H⋯π interactions. Dotted lines represent the weak interactions. Hydrogen atoms not participating in hydrogen bonding
are omitted for clarity.
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Fig. 2 (a) ORTEP drawing of 2 with the ellipsoids drawn at the 30% probability level. (b) The 1D chain structure of complex 2 formed by multiple C–
H⋯O hydrogen bonding and Ag⋯O interactions. (c) The 2D layer structure of complex 2 formed by C–H⋯N hydrogen bonding, Ag⋯π interactions,
C–H⋯O hydrogen bonding and π⋯π interactions. (d) The 3D supramolecular structure of complex 2 formed by multiple C–H⋯N hydrogen bonding
interactions. Dotted lines represent the weak interactions. Hydrogen atoms not participating in hydrogen bonding are omitted for clarity.
175.4(2)° for 5, indicating a linear coordination geometry.10 together through multiple C–H⋯F hydrogen bonding inter-
The deviation of the value of the N–Ag–N angle for 1, 4 and 5 actions to generate a two-dimensional supramolecular structure.
is probably due to the internal steric hindrance between the
Complex 2 was prepared from the same ligand (L1) and
anions and the two coordinated ligand molecules. The Ag–N metal salt (NO3−) as complex 3. Different from 3, the crystals
bond lengths of 1, 3, 4 and 5 fall within the normal range as of complex 2 were obtained from dichloromethane–benzene
seen in Table 2.11 Furthermore, the Ag(I) cation in each mixed solution. Compared to 3, complex 2 crystallizes in the
complex is charge balanced by free anions while CF3COO− monoclinic form with space group P21/c rather than in the tri-
ˉ
anions have strong coordination ability and they coordinate clinic space group P1 as shown in Table 1. The molecular
with Ag(I) ions in the AgL1 OOCCF3·C6H6 (4) unit.12 The dis- structure of complex 2 is illustrated in Fig. 2a. The ligand L1 in
2
order appears in the O atoms of the free nitrate anion in 2 adopts the same coordination mode as complexes 1, 3 and 5.
complex 3.
Complex 2 has the same linear coordination geometry as com-
Fig. 1b and 3b indicate that the uncoordinated perchlorate plexes 1, 3 and 5. The disorder appears in the O atoms of the
and nitrate anions play a significant role in forming a 1D free nitrate anion and C7, C8, C9 of the ligands. The adjacent
chain structure through Ag⋯O interactions with distances in mononuclear complex molecules are linked together along the
the range of 2.736–2.954 Å and various C–H⋯O hydrogen a-axis through multiple C–H⋯O hydrogen bonds (O⋯H dis-
bonds with distances in the range of 2.186–2.954 Å. Addition- tances in the range of 2.278–2.680 Å) and Ag⋯O interactions
ally, we can find that it is the weak force of C–H⋯N hydrogen (d = 3.022 Å) based on NO3− to form an infinite chain, as illus-
bond (d = 2.739 Å) that constructs the 1D chain structure of 1. trated in Fig. 2b. The neighboring chains are further linked by
However, different from 1 and 3, the benzene molecules play a intermolecular interactions, giving rise to an extended layer
critical role in determining the 1D chain structure in the structure along the c plane, as shown in Fig. 2c. Seen along the
crystal packing of complexes 4 and 5 (Fig. 4b and 5b). Further- b-axis in Fig. 2d, significantly different from complex 3, the
more, the chains of 1, 3 and 4 are further connected via inter- nitrogen atoms of –CuN are not directly involved in coordi-
molecular interactions to generate a layer structure (Fig. 1c, 3c nation, but the lone pair electrons from the N atom still have a
and 4c). While in the crystal structure of complex 5 (Fig. 5c), strong pro-E competence, which generates a 3D zigzag supra-
multiple C–H⋯F hydrogen bonding interactions, including molecular structure through C8A–H8A⋯N1 hydrogen bonds
C28–H28⋯F2 (d = 2.516 Å), C20–H20⋯F3 (d = 2.329 Å) and (d = 2.702 Å).
−
C24–H24⋯F6 (d = 2.365 Å) based on the uncoordinated PF6
The assembled reactions of L1 with AgNO3 by varying the
−
counterions are formed. The PF6 anions link the chains solvent from CH2Cl2–C6H6 to CH2Cl2–CH3OH–C6H6 afford
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Fig. 3 (a) ORTEP drawing of 3 with the ellipsoids drawn at the 30% probability level. (b) The 1D chain structure of complex 3 formed by multiple
C–H⋯O hydrogen bonding and Ag⋯O interactions. (c) The 2D layer structure of complex 3 formed by multiple C–H⋯O hydrogen bonding,
C–H⋯N hydrogen bonding, Ag⋯π interactions and π⋯π interactions. Dotted lines represent the weak interactions. Hydrogen atoms not participating
in hydrogen bonding are omitted for clarity.
Fig. 4 (a) ORTEP drawing of 4 with the ellipsoids drawn at the 30% probability level. (b) The 1D chain structure of complex 4 formed by C–H⋯π
interactions. (c) The 2D layer structure of complex 4 formed by C–H⋯O hydrogen bonding, Ag⋯π interactions and C–H⋯π interactions. Dotted
lines represent the weak interactions. Hydrogen atoms not participating in hydrogen bonding are omitted for clarity.
complexes 2 and 3, respectively. Taking complexes 2 and 3 into zigzag supramolecular structure along the b-axis is formed
account, the main difference is the existence of solvent through C8A–H8A⋯N1 hydrogen bonds. The result shows that
benzene molecules in complex 3 while there are no solvent the steric hindrance of solvent benzene molecules in 3 have a
molecules in complex 2, which results in an extremely direct influence on the formation of the 3D supramolecular
different supramolecular structure. In complex 2, the final 3D structure.
1144 | Dalton Trans., 2014, 43, 1139–1150
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Fig. 5 (a) ORTEP drawing of 5 with the ellipsoids drawn at the 30% probability level. (b) The 1D chain structure of complex 5 formed by C–H⋯π
interactions. (c) The 2D layer structure of complex 5 formed by multiple C–H⋯F hydrogen bonding, Ag⋯F interactions, Ag⋯π interactions and
C–H⋯π interactions. Dotted lines represent the weak interactions. Hydrogen atoms not participating in hydrogen bonding are omitted for clarity.
Fig. 6 (a) ORTEP drawing of 6 with the ellipsoids drawn at the 30% probability level. (b) The 1D chain structure of complex 6 formed by multiple C–
H⋯O hydrogen bonding and Ag⋯O interactions. (c) The 2D layer structure of complex 6 formed by C–H⋯N hydrogen bonding and π⋯π inter-
actions. (d) The 3D supramolecular structure of complex 6 formed by π⋯π interactions. Dotted lines represent the weak interactions. Hydrogen
atoms not participating in hydrogen bonding are omitted for clarity.
Crystal structure of complexes 6–8 based on L2
triazolyl moieties located on the same side of ligand in 6 and 8
as shown in Fig. 6a and 8a. The N1–Ag1–N1A and N5–Ag1–N5A
Complexes 6 and 8 crystallize in the same monoclinic C2/c angles deviate from 180.00° probably due to the influence of
space group (Table 1). Fig. 6a and 8a show the coordination the weak C–H⋯O or C–H⋯F interactions. The Ag–N bond
environments of the Ag(I) ions with the atom numbering lengths (Table 2) are comparable to those in the reported Ag(I)
scheme. The ligand L2, quite different from L1 in complexes complexes.11 Similar to 1–3, the free anions play a significant
1–5 and 7, adopts the cis-conformation to bind Ag(I) ions with role in forming the 1D chain structure along the b-axis
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Fig. 7 (a) ORTEP drawing of 7 with the ellipsoids drawn at the 30% probability level. (b) The 1D chain structure of complex 7. (c) The 2D layer struc-
ture of complex 7 and (d) further formed by C–H⋯π interactions, Ag⋯π interactions and π⋯π interactions. Dotted lines represent the weak inter-
actions. Hydrogen atoms not participating in hydrogen bonding are omitted for clarity.
through Ag⋯O interactions and various C–H⋯O hydrogen noteworthy that the Ag2 ions bridge two neighboring Ag1L2
−
bonds based on NO3 anions for 6, or through Ag⋯F inter- units to generate
a
1D coordination polymer with the
−
actions and various C–H⋯F hydrogen bonds based on PF6
Ag1⋯Ag2 distance of 6.433 Å (Fig. 7b). The chains are further
anions for 8. The neighboring chains are further linked by connected via F3CCOO− to generate a layer structure of
C12A–H12A⋯N4 (2.743 Å) and π–π stacking interactions polymer 7 (Fig. 7c). The bond angles around the silver atom
(3.345 Å and 3.349 Å) for 6, or by C15–H15⋯F1 (2.644 Å), are in the range of 83.21(15)–167.74(14)°. Additionally, C37B–
C9B–H9B⋯F1 (2.464 Å) and π–π stacking interactions (3.321 Å) H37B⋯π, Ag⋯π and π⋯π interactions with distances of 2.895,
for 8, giving rise to an extended layer staircase structure along 3.735 and 3.878 Å, respectively, provide further stability to the
the c plane, as shown in Fig. 6c and 8c, respectively. As shown layer structure (Fig. 7d). The results indicate that the similar
in Fig. 6d and 8d, the uncoordinated –CuN moieties of the supramolecular structures of 6 and 8 are different from that of
ligand L2 play an important role in generating the 3D supra- 7, which is probably ascribed to the different coordination
molecular structure along the ac plane through π⋯π inter- modes of the ligands L2 in 6, 8 and 7 (Scheme 1).
actions with the distance of 3.290 Å for 6 and 3.301 Å for 8.
Structural comparison and effect of ligands and anions on the
Single-crystal analysis indicates that complex 7 with two
structures
silver(I) ions in the asymmetric unit crystallizes in the triclinic
2
ˉ
system, space group P1. As shown in Fig. 7a, L adopts the
trans-conformation to bind Ag1 ions with two triazolyl nitro-
gen atoms from two different molecules located on different
sides of the ligand. The N6–Ag1–N5 angle is not 180.00° but
167.74(14)°, which should be due to the influence of the Ag1–
O1 interactions. Notably, the two crystallographically indepen-
dent Ag(I) centers display different trigonal and tetrahedral
coordination geometries, respectively (see Fig. 7c). Similar to
4, the Ag1 center is also coordinated by one oxygen atom from
CF3COO− due to their strong coordination ability, with the dis-
tance of 2.501 Å to form a trigonal planar geometry.12
However, the Ag2 center is surrounded by two oxygen atoms
from two F3CCOO− anions, one triazolyl nitrogen atom from
one ligand and one –CuN nitrogen atom from the other
ligand to form a distorted tetrahedral geometry.13 It is
The diverse coordination modes of the organic ligands have
been proven to have a great influence on the structure of com-
plexes.14 The coordination modes of the L1 and L2 ligands are
shown in Scheme 1. The complexes containing L1 with
different anions have an almost identical coordination sphere
around the silver cation (except in 4) and the arrangement of
their building blocks is similar. Complexes 6 and 8 with L2
also have an almost identical coordination sphere around the
silver cation and supramolecular structure, which is different
from 1–5. The L1 ligands in complexes 1–5 adopt the trans-con-
formation to bind Ag(I) ions while they adopt the cis-confor-
mation to bind Ag(I) ions in complexes 6 and 8. Obviously, the
L1 and L2 ligands show distinct binding features upon metal
complexation due to the imidazolyl group in L1 being replaced
by the triazolyl in L2. The structures of 1–6 and 8 show that
1146 | Dalton Trans., 2014, 43, 1139–1150
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Fig. 8 (a) ORTEP drawing of 8 with the ellipsoids drawn at the 30% probability level. (b) The 1D chain structure of complex 8 formed by multiple C–
H⋯F hydrogen bonding and Ag⋯F interactions. (c) The 2D layer structure of complex 8 formed by multiple C–H⋯F hydrogen bonding and π⋯π
interactions. (d) The 3D supramolecular structure of complex 8 formed by π⋯π interactions. Dotted lines represent the weak interactions. Hydrogen
atoms not participating in hydrogen bonding are omitted for clarity.
they are all mononuclear complexes and only one nitrogen preparing coordination complexes, which can be divided into
atom of the imidazolyl group in L1 or the triazolyl group in L2 two key effects depending on the final supramolecular struc-
is bound to the Ag(I) atom. In the structures of 1–8, it was ture. The anions influence the coordination environment of
found that there is one coordination F3CCOO− anion in 4 and the metal cations by coordination with them and which in
7, while no coordinated anions were detected in 1, 2, 3, 5, 6 turn dictates the construction of the supramolecular structure.
and 8. For complex 7, interestingly, two nitrogen atoms of the
We are of the opinion that this study further leads to the
triazolyl group and one nitrogen atom of cyano group all co- systematic investigation of the supramolecular structure of
ordinate with the Ag(I) atoms in a special mode, to generate silver coordination complexes based on weak interactions
the 2D coordination polymer. The two Ag(I) atoms in complex adjusted by the selection of different ligands, various anions
7 adopt three-coordination and four-coordination respectively and solvent molecules. This study demonstrates that the tri-
due to F3CCOO− chelating with two silver atoms. The results azole-containing rigid organic ligand (E)-2-(3-(4-(1H-1,2,4-
confirm that there are plentiful different coordination modes triazol-1-yl)styryl)-5,5-dimethylcyclohex-2-enylidene)malononi-
for the L2 ligand in their silver metal complexes 6–8 and, fur- trile (L2) is capable of coordinating metal centers with both
thermore, the F3CCOO− anion is easy to chelate with silver Ncyano and Ntriazole donors, and generating novel coordination
atoms compared with other anions. Additionally, the above polymers.
new silver(I) coordination complexes are built up through the
combination of silver coordination, Ag⋯π, Ag⋯F (or O), hydro-
Third-order nonlinear optical properties
gen bonding, and π⋯π stacking interactions to generate new
supramolecular architectures.15
The third-order NLO properties were measured at a concen-
Solvent benzene molecules are dispersed in the supramole- tration of 1.0 × 10−3 mol L−1 in DMSO solution using the
cular structure and play a vital role in building the supramole- Z-scan technique. For the experiments, the pulse length was
140 fs and the repetition rate was kept at 10 Hz. Because L2,
cular structures by forming different C–H⋯π interactions in
complexes 4 and 5, while no weak interaction involving them L2, 5, 6 and 8 have no nonlinear absorption in DMSO, only the
was observed in the solid state of 3. Different from L1, the third-order optical nonlinearities of complexes 1, 2, 3, 4 and 7
assembled systems of L2 and Ag(I) are also not sensitive to
are presented. The excitation wavelengths of complexes 1, 2, 3,
−
solvent media. It is worth pointing out that the ClO4−, NO3
,
4 and 7 are 700, 750, 740, 720 and 740 nm, respectively.
The open aperture Z-scan curves are shown in Fig. 9(a) and
Fig. S1 (ESI†). The filled squares represent the experimental
and PF6− anions are near to the Ag(I) centre in their complexes
and are weakly coordinated to the Ag(I). It has been further
demonstrated that anions also play an important role in data and the solid line is the theoretical data fitted by using
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Fig. 9 (a) The open aperture and (b) close aperture Z-scan data of complex 1. The filled squares represent the experimental data and the solid
curve is the theoretical data.
the following equations:16,17
equations:18
Reχ ð3Þ ¼ 10ꢀ4n02ε0c2γ=π
1
m
X
½ꢀq0ðzÞꢁ
Tðz; s ¼ 1Þ ¼
for jq0j , 1
3=2
m¼0 ðm þ 1Þ
Imχ ð3Þ ¼ 10ꢀ2n02ε0c2βλ=4π2
βI0Leff
1 þ x2
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
q0ðzÞ ¼
2
2
χð3Þ
¼
ðReχð3ÞÞ þ ðImχð3ÞÞ
where x = z/z0, z is the distance of the sample and beam focus,
z0 = πω0 /λ is the diffraction length of the beam with ω0 the
spot size at focus, λ is the wavelength of the beam, β is the TPA
where ε0 is the vacuum permittivity, c is the light velocity in a
vacuum and n0 is the linear refractive index of DMSO. In this
case, the third-order nonlinear refractive index γ can be
derived from the equations:19
2
coefficient, I0 is the input intensity at the focus (z = 0) calcu-
lated by the input energy divided by πω0 , Leff = (1 − e−αL)/α is
2
0:25
ΔTpv ¼ 0:406ð1 ꢀ SÞ jΔφj; Δφ ¼ KLeff γI0
the effective length with α the linear absorption coefficient
and L the sample length. Furthermore, the molecular TPA
cross-section (σ) could be determined by using the following
relationship:17
In the equations, ΔTpv is the difference between the peak
and the valley of the normalized transmission, S is the fraction
of the transmitted beam through the aperture, and Δφ is the
on-axis phase shift, where ΔTpv = 0.92 (1), 0.33 (2), 0.62 (3),
0.45 (4) and 0.40 (7), S = 0.210, K = 2π/λ. The obtained γ and
σ ¼ hγβ=NAd ꢂ 10ꢀ3
here h is the Planck’s constant, γ is the frequency of input
intensity, NA is the Avogadro constant, and d is the concen-
χ
(3) are listed in Table 3.
Free ligands L1 and L2 do not show any nonlinear absorp-
tration of the sample. Based on the above equations, the tion behavior at ∼700 nm. In contrast, significant nonlinear
values of β and σ of the complexes are given in Table 3. absorption performance is observed for each of the complexes
Obviously, the TPA coefficient β and TPA cross section σ of 1, 2, 3, 4 and 7 at the excitation wavelength which may be
complexes 1, 2, 3, 4 and 7 are larger than those of free ligands caused by cooperative intermolecular interactions in the com-
(L1, L2).
plexes.20 The isophorone ligands (L1, L2) belong to the D–π-A
The nonlinear refraction indexes of complexes 1, 2, 3, 4 and analogue since the terminal imidazole or triazole part pos-
7 were determined by the close aperture Z-scan technique. The sesses very weak electron-donating character. Complexation
resulting data and fitted curve are shown in Fig. 9(b) and with Ag(I) enhances the electron-acceptor character of the imi-
Fig. S1 (ESI†). According to the figures, the reported complexes dazole or triazole moiety, converting L1 or L2 to a more
1, 2, 3, 4 and 7 exhibit a self-defocusing effect (Δn < 0) with a strongly polarized A–π-D unit (Fig. 10) that makes the com-
peak-to-valley configuration. The effective third-order NLO sus- plexes 1, 2, 3, 4 and 7 potential candidates for third-order non-
ceptibility χ(3) of the sample can be calculated by the following linear responses.
Table 3 Third-order NLO data for complexes 1, 2, 3, 4 and 7
Complex
1
2
3
4
7
β (cm GW−1
)
1.88
0.12
0.14
0.08
0.44
σ (cm4 s photon−1 molecule−1
)
8.86 × 10−46
1.17 × 10−17
5.86 × 10−15
5.28 × 10−47
5.12 × 10−18
4.90 × 10−16
6.24 × 10−47
9.27 × 10−18
6.90 × 10−16
3.80 × 10−47
6.22 × 10−18
4.35 × 10−16
1.96 × 10−46
5.99 × 10−18
1.48 × 10−15
γ (m2 W−1
(3) (esu)
)
χ
1148 | Dalton Trans., 2014, 43, 1139–1150
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Conclusions
In summary, eight novel Ag(I) coordination polymers or dis-
crete supramolecular complexes (1–8) with rigid multidentate
ligands (L1 and L2) have been prepared and structurally
characterized. Single crystal X-ray structures indicated that the
ligands adopted several coordination modes to coordinate
with Ag(I) ions in the complexes. The complexes exhibit
different molecular structures and packing characteristics
suggesting that the ligands, the solvents and the counter-
anions have a subtle but important influence on the structure
of the complexes. In addition, the third-order NLO properties
of the complexes were investigated in detail, and the results
showed that complexes 1, 2, 3, 4 and 7 may be good candidates
for non-linear optical materials.
Fig. 10 Plan for metal-mediated third-order nonlinear responses in
D–π-A ligands.
Acknowledgements
This work was supported by the Program for New Century
Excellent Talents in University (China), the Doctoral Program
Foundation of the Ministry of Education of China
(20113401110004), the National Natural Science Foundation of
China (21271003 and 21271004), the Natural Science Foun-
dation of Education Committee of Anhui Province
(KJ2012A024, KJ2013B201), the Natural Science Foundation of
Anhui Province (1208085MB22), the 211 Project of Anhui Uni-
versity, the Excellent Youth Fund in University of Anhui Pro-
vince (2012SQRL025), Dr Start-up funds of Anhui University
(33190224, 33190212) and the Ministry of Education Funded
Projects Focus on Returned Overseas Scholar.
Fig. 11 The scheme of ligands and complexes, the 21 atoms forming
the mean plane are drawn in red. The anions are omitted for clarity.
Notes and references
As shown in Fig. 11, the conjugated system of ligand (L1 or
L2) in the complex is almost planar with 21 atoms forming a
mean plane. The puckering amplitude to the mean plane for
the 21 atoms Δ does not exceed 0.253 Å. The dihedral angles
measured between the two mean planes in a complex unit are
0.75° (1), 0.00° (2), 0.00° (3), 0.38° (4), 1.39° (5), 7.78° (6), 6.55°
(7) and 10.58° (8), respectively. Compared with complexes 1, 2,
3, 4 and 7, complexes 5, 6 and 8 do not show any nonlinear
absorption behavior, which is probably ascribed to the larger
dihedral angle between the two mean planes, and the dis-
torted conformations do not permit effective conjugation.21
The enhanced nonlinear absorption is also observed for the
complex 7 although it has a larger dihedral angle between the
two mean planes, which is probably due to the formation of
two-dimensional coordination polymers increasing the conju-
gation length of complex 7. The results indicate that the
effective intramolecular charge transfer and increased conju-
gation length in complexes 1, 2, 3, 4 and 7 may be responsible
for the large TPA cross sections compared to those of the com-
plexes 5, 6, 8 and ligands (L1, L2).
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