Aminobenzonitrile Compounds

Article pubs.acs.org/crystal

Anion-Controlled Assembly of Silver(I)/Aminobenzonitrile Compounds: Syntheses, Crystal Structures, and Photoluminescence Properties Fu-Jing Liu,†,§ Di Sun,*,‡,§ Hong-Jun Hao,† Rong-Bin Huang,*,† and Lan-Sun Zheng† †

State Key Laboratory of Physical Chemistry of Solid Surface, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China ‡ School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong, 250100, China S Supporting Information *

ABSTRACT: Five coordination compounds (CCs) of the formulas {[Ag(mabn)2]·NO3}n (1), {[Ag2(m-abn)6]·(ClO4)2} (2), {[Ag(o-abn)2]·NO3}n (3), [Ag(oabn)2(NO2)]n (4), and {[Ag(o-abn)2]·PF6}n (5) (m-abn = 3-aminobenzonitrile, and o-abn = 2-aminobenzonitrile) were synthesized and structurally characterized by element analysis, IR, powder X-ray diffraction, and X-ray single-crystal diffraction. Structural analysis reveals that aminobenzonitrile acts as bidentate μ2-N,N′ or monodentate μ1-N ligands in 1−5. Complex 1 is a 1D chain comprised of C2symmetric [Ag(m-abn)]2 14-membered rings. The uncoordinated NO3− anions interact with the 1D chain to form a resulting 2D supramolecular sheet through N−O···N hydrogen bond. Complex 2 is a discrete binuclear Ag(I) CC incorporating concurrent bidentate μ2-N,N′ and monodentate μ1-N m-abn ligands. The variation of anions from NO3− to ClO4− results in the dimensionalities of 1 and 2 decreasing from 1D to 0D. When using o-abn, complexes 3−5 are obtained as 1D chain with C2-symmetric [Ag(o-abn)]2 12-membered rings, 2D sheet with coordinated μ2-η1:η2 NO2− anions, and 1D chain with centrosymmetric [Ag(o-abn)]2 12-membered rings, respectively. Supramolecular interactions such as hydrogen bonding and π···π stacking are also proven effective in shaping the dimensionalities of the solid state structures of 1−5. Our results demonstrate that the anions are driving forces for the selection of different structures. Moreover, results about emissive behaviors and thermal stabilities of them are discussed.

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INTRODUCTION Over the past decades, the crystal engineering of coordination polymers and metallo-supramolecular architectures has been studied extensively due to their structural versatility, distinctive properties, and potential applications in different fields of science.1 Despite some evolution, the ability to predict and control the supramolecular assembly is seriously restricted by the bewildering structure-directing factors such as inbeing of the metal ions, the predesigned organic linkers,2 solvent,3 pH value of the solution,4 the temperature,5 the counterion with different bulk or coordination ability, the template, and metalto-ligand stoichiometry,6 and much more elaborate studies are required to comprehend the inter- and intramolecular forces that determine the fashions of molecular structure and molecule packing in the solid state. Including the abovementioned factors, the noncovalent forces such as hydrogenbonding, π···π stacking, metal···metal interactions based on d10 metal cations, metal···π, C−H···π, and anion···π interactions also determine the supramolecular topology and dimensionality.7 On the other hand, although the abn (aminobenzonitrile) ligand has diverse coordination preferences such as monodentate (albeit ambidentately using either Namino or Ncyano), bridging, or bidentate fashion (using both N donors),8 © 2011 American Chemical Society

coordination chemistry of it was still less reported because both Namino and Ncyano atoms of abn ligand are weak coordinative sites due to the conjunction of electrons on p-orbital with phenyl ring, and the cyano group is volatile in both acidic and alkaline environments.9 Recently, we synthesized four similar (6,3) nets in the presence of four different anions (NO3−, ClO4−, PF6−, and CF3COO−) in Ag/p-abn (4-abn) system,10 which indicates the negligible effect of anions in that system and is an abnormal phenomena as compared to the fact that inorganic or organic anions with different sizes, geometries, and coordinating abilities usually influence the coordination versatility of the organic ligand and thus influence the architectures and properties of the CCs.11 As an extension of our previous work, herein we focused on the Ag/o-abn and Ag/ m-abn system to investigate whether and how the anions exert the effect on the structures of CCs as well as their properties. In this paper, we report the syntheses, crystal structures, and properties of five new CCs, namely, {[Ag(m-abn)2]·NO3}n (1), {[Ag2(m-abn)6]·(ClO4)2} (2), {[Ag(o-abn)2]·NO3}n (3), Received: September 4, 2011 Revised: October 23, 2011 Published: November 14, 2011 354

dx.doi.org/10.1021/cg201159z | Cryst. Growth Des. 2012, 12, 354−361

Crystal Growth & Design

Article

from 30 to 750 °C on a NETZSCH TG 209 F1 Iris Thermogravimetric Analyzer at a heating rate 10 °C/min under N2 atmosphere (20 mL/min). Preparation of Compounds 1−5. {[Ag(m-abn)2]·NO3}n (1). A mixture of AgNO3 (17 mg, 0.1 mmol) and m-abn (12 mg, 0.1 mmol) was stirred in methanol−water mixed solvent (5 mL, v/v: 3/2). Then, aqueous NH3 solution (25%, 1 mL) was dropped into the mixture to give a clear solution under ultrasonic treatment. The resultant solution was allowed to evaporate slowly in darkness at room temperature for several days to give colorless crystals of 1 (yield, 51%, based on silver). Anal. calcd (found) for AgC14H12N5O3: C, 41.40 (40.69); H, 2.98 (2.58); N, 17.24 (17.30) %. IR (KBr): ν (cm−1) = 3399 (s), 3320 (s), 3225 (s), 2234 (s), 1643 (m), 1599 (s), 1582 (s), 1551 (m), 1492 (m), 1447 (m), 1384 (s), 1322 (s), 1294 (s), 1167 (w), 895 (w), 863 (s), 825 (w), 789 (s), 686 (s), 676 (m), 609 (w), 567 (w), 530 (w). {[Ag2(m-abn)6]·(ClO4)2} (2). A mixture of Ag2O (23 mg, 0.1 mmol), m-abn (24 mg, 0.2 mmol), and NaClO4 (25 mg, 0.2 mmol) was stirred in methanol−ethanol mixed solvent (6 mL, v/v: 1/1). Then, aqueous NH3 solution (25%, 2 mL) was dropped into the mixture to give a clear solution under ultrasonic treatment. The resultant solution was allowed to evaporate slowly in darkness at room temperature for several days to give colorless crystals of 2 (yield, 71%, based on silver). Anal. calcd (found) for Ag2C42H36Cl2N12O8: C, 44.90 (44.32); H, 3.23 (3.34); N, 14.96 (14.04)%. IR (KBr): ν (cm−1) = 3400 (s), 3329 (s), 3226 (s), 2234 (s), 1643 (m), 1599 (s), 1582 (s), 1492 (m), 1478 (w), 1447 (m), 1328 (m), 1294 (s), 1144 (s), 1111 (s), 1088 (s), 863 (s), 789 (s), 725 (m), 686 (s), 626 (s), 530 (m), 477 (s). {[Ag(o-abn)2]·NO3}n (3). A mixture of AgNO3 (17 mg, 0.1 mmol) and o-abn (12 mg, 0.1 mmol) was stirred in methanol−ethanol mixed solvent (6 mL, v/v: 1/1) to give a clear solution under ultrasonic treatment. The resultant solution was allowed to evaporate slowly in darkness at room temperature for several days to give colorless crystals of 3 (yield, 35%, based on silver). Anal. calcd (found) for AgC14H12N5O3: C, 41.40 (39.86); H, 2.98 (3.04); N, 17.24 (17.09) %. IR (KBr): ν (cm−1) = 3459 (s), 3367 (s), 2209 (m), 1626 (m), 1569 (m), 1495 (m), 1457 (m), 1384 (s), 1314 (m), 1266 (m), 1156 (w), 825 (w), 746 (m), 493 (m). [Ag(o-abn)2(NO2)]n (4). A mixture of AgNO2 (31 mg, 0.2 mmol) and o-abn (48 mg, 0.2 mmol) was stirred in methanol−ethanol mixed

[Ag(o-abn)2(NO2)]n (4), and {[Ag(o-abn)2]·PF6}n (5) (m-abn = 3-abn, and o-abn = 2-abn) (Scheme 1). Scheme 1. Preparation Route of Ag(I)/abn CCs in the Presence of Different Anions

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EXPERIMENTAL SECTION

Materials and General Methods. All of the reagents and solvents employed were commercially available and used as received without further purification. Infrared spectra were recorded on a Nicolet AVATAT FT-IR330 spectrometer as KBr pellets in the frequency range 4000−400 cm−1. The elemental analyses (C, H, N contents) were determined on a CE instruments EA 1110 analyzer. Photoluminescence measurements were performed on a Hitachi F-7000 fluorescence spectrophotometer with solid powder on a 1 cm quartz round plate. Thermogravimetric (TG) curves were measured

Table 1. Crystal Data for 1−5 compound formula Mr crystal system space group a (Å) b (Å) c (Å) β (deg) Z V (Å3) Dc(g cm−3) μ (mm−1) F(000) no. of unique reflns no. of obsd reflns [I > 2σ(I)] parameters GOF final R indices [I > 2σ(I)]a,b R indices (all data) largest difference peak and hole (e Å−3) a

1

2

3

4

5

AgC14H12N5O3 406.16 monoclinic C2/c 8.251(2) 11.315(2) 16.222(4) 101.949(6) 4 1481.7(6) 1.821 1.383 808 1451 1418 106 1.138 R1 = 0.0275 wR2 = 0.0632 R1 = 0.0285 wR2 = 0.0640 0.591 and −0.245

Ag2C42H36Cl2N12O8 1123.47 monoclinic P21/n 11.632(2) 7.5766(15) 25.228(5) 97.10(3) 2 2206.4(8) 1.691 1.077 1128 4318 3126 298 1.086 R1 = 0.0396 wR2 = 0.0799 R1 = 0.0618 wR2 = 0.0935 1.343 and −0.758

AgC14H12N5O3 406.16 monoclinic P2/c 7.889(2) 5.7444(17) 16.373(5) 101.986(6) 2 725.8(4) 1.858 1.412 404 1370 1310 106 1.143 R1 = 0.0316 wR2 = 0.0759 R1 = 0.0329 wR2 = 0.0769 0.581 and −0.726

AgC7H6N3O2 272.02 monoclinic P21/n 8.2396(7) 5.8279(3) 17.5896(10) 96.827(3) 4 838.66(10) 2.154 2.370 528 1637 998 119 1.158 R1 = 0.0488 wR2 = 0.0965 R1 = 0.0962 wR2 = 0.1607 1.389 and −1.470

AgC14H12F6N4P 489.12 monoclinic C2/c 9.6802(19) 16.899(3) 10.494(2) 91.02(3) 4 1716.5(6) 1.893 1.334 960 1511 1345 149 1.092 R1 = 0.0221 wR2 = 0.0513 R1 = 0.0283 wR2 = 0.0541 0.378 and −0.370

R1 = ∑∥Fo| − |Fc∥/∑|Fo|. bwR2 = [∑w(Fo2 − Fc2)2/∑w(Fo2)2]0.5. 355



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Table 2. Selected Bond Lengths (Å) and Angles (°) for 1−5 i

Ag1−N2 N2i−Ag1−N2ii

2.301 (2) 93.86 (11)

Ag1−N1 N2i−Ag1−N1

Ag1−N5 N5−Ag1−N1 N1−Ag1−N3

2.314 (3) 117.71 (10) 120.17 (11)

Ag1−N6i N5−Ag1−N6i N3−Ag1−N6i

Ag1−N1 N1i−Ag1−N1

2.316 (2) 120.30 (12)

Ag1−N2ii N1i−Ag1−N2iii

Ag1−N2 Ag1−O1i N2−Ag1−O1i O1−Ag1−O1i O1−Ag1−N1ii

2.328 (10) 2.464 (8) 95.5 (3) 81.47 (14) 127.5 (3)

Ag1−N1ii

Ag1−N2i N2i−Ag1−N2ii

2.299 (2) 110.67 (10)

Ag1−N1 N2ii−Ag1−N1

N2−Ag1−O2 O1−Ag1−O2 N1ii−Ag1−O2

compound 1a 2.354 (2) 99.97 (7) N1iii−Ag1−N1 compound 2b 2.544 (3) Ag1−N1 99.16 (10) N5−Ag1−N3 90.94 (11) compound 3c 2.353 (3) 127.00 (9) N1i−Ag1−N2ii compound 4d 2.466 (9) Ag1−O2 110.4 (3) 49.4 (2) 87.8 (3) compound 2.3490 (18) 110.68 (7)

N2−Ag1−O1 N2−Ag1−N1ii

101.31 (10)

N2ii−Ag1−N1

133.86 (8)

2.321 (3) 119.40 (11)

Ag1−N3 N1−Ag1−N6i

2.331 (3) 96.50 (10)

96.52 (9)

N2ii−Ag1−N2iii

88.11 (13)

2.582 (8)

Ag1−O1

2.428 (8)

127.3 (3) 91.7 (3)

O1i−Ag1−N1ii O1i−Ag1−O2

133.9 (3) 130.7 (3)

N1−Ag1−N1iii

117.61 (9)

5e N2i−Ag1−N1

103.65 (7)

Symmetry codes: (i) −x + 1/2, −y + 1/2, −z + 1. (ii) x + 1/2, −y + 1/2, z + 1/2. (iii) −x + 1, y, −z + 3/2. Symmetry code: (i) −x + 1, −y + 1, −z + 1. cSymmetry codes: (i) −x + 1, y, −z + 1/2. (ii) −x + 1, y − 1, −z + 1/2. (iii) x, y − 1, z. dSymmetry codes: (i) −x + 1/2, y + 1/2, −z + 3/2. (ii) −x + 3/2, y − 1/2, −z + 3/2. eSymmetry codes: (i) −x + 1, −y + 1, −z + 2. (ii) x, −y + 1, z − 1/2. (iii) −x + 1, y, −z + 3/2. a

b

solvent (6 mL, v/v: 1/2). Then, aqueous NH3 solution (25%, 0.5 mL) was dropped into the mixture to give a clear solution under ultrasonic treatment. The resultant solution was allowed to evaporate slowly in darkness at room temperature for several days to give yellow crystals of 4 (yield, 26%, based on silver). Anal. calcd (found) for AgC7H6N3O2: C, 30.91 (30.66); H, 2.22 (2.25); N, 15.45 (14.81) %. IR (KBr): ν (cm−1) = 3460 (s), 2210 (w), 1268 (m), 1569 (m), 1495 (w), 1457 (w), 1414 (w), 1269 (s), 746 (w), 493 (w). {[Ag(o-abn)2]·PF6}n (5). A mixture of Ag2O (23 mg, 0.1 mmol), o-abn (48 mg, 0.4 mmol), and NH4PF6 (33 mg, 0.2 mmol) was stirred in methanol−ethanol mixed solvent (6 mL, v/v: 1/2). Then, aqueous NH3 solution (25%, 0.5 mL) was dropped into the mixture to give a clear solution under ultrasonic treatment. The resultant solution was allowed to evaporate slowly in darkness at room temperature for several days to give colorless crystals of 5 (yield, 50%, based on silver). Anal. calcd (found) for AgC14H12F6N4P: C, 34.38 (34.37); H, 2.47 (2.40); N, 11.46 (11.41) %. IR (KBr): ν (cm−1) = 3460 (s), 3368 (s), 3241 (m), 3080 (w), 2210 (s), 1627 (s), 1570 (m), 1495 (s), 1457 (s), 1339 (w), 1315 (m), 1267 (s), 1156 (w), 832 (s), 746 (s), 559 (s), 493 (s). X-ray Crystallography. Single crystals of the compounds 1−5 with appropriate dimensions were chosen under an optical microscope and quickly coated with high vacuum grease (Dow Corning Corporation) before being mounted on a glass fiber for data collection. Data were collected on a Rigaku R-AXIS RAPID Image Plate single-crystal diffractometer with graphite-monochromated Mo Kα radiation source (λ = 0.71073 Å) operating at 50 kV and 90 mA in ω scan mode for 1−5. A total of 44 × 5.00° oscillation images were collected, each being exposed for 5.0 min. Absorption correction was applied by correction of symmetry-equivalent reflections using the ABSCOR program.12 In all cases, the highest possible space group was chosen. All structures were solved by direct methods using SHELXS9713 and refined on F2 by full-matrix least-squares procedures with SHELXL-97.14 Atoms were located from iterative examination of difference F maps following least-squares refinements of the earlier models. Hydrogen atoms were placed in calculated positions and included as riding atoms with isotropic displacement parameters 1.2− 1.5 times Ueq of the attached C or N atoms. All structures were examined using the Addsym subroutine of PLATON15 to ensure that no additional symmetry could be applied to the models. The crystallographic details of 1−5 are summarized in Table 1. Selected bond lengths and angles for 1−5 are collected in Table 2. The

hydrogen bond geometries for 1−5 are shown in Table S1 in the Supporting Information.

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RESULT AND DISCUSSION Syntheses. The syntheses of compound 1−5 were carried out in the darkness to avoid photodecomposition and are summarized in Scheme 1. An ultrasonic technique can produce high local temperatures and pressures, combined with extraordinarily rapid cooling, providing a unique means for driving chemical reactions under extreme conditions. In this system, the ultrasound technique also realizes the rapid (10 min) and efficient (maximum 30 different experiments in one batch) preparation of CCs.16 Structure Descriptions. {[Ag(m-abn)2]·NO3}n (1). X-ray single-crystal analysis reveals that 1 crystallizes in the monoclinic space group C2/c, and the asymmetric unit contains a half of Ag(I) ion, one m-abn ligand, and a half of NO3− anion. Two independent 2-fold axes pass through the Ag1 and N3− O1 bond of NO3− anion, respectively. As shown in Figure 1a, the Ag(I) ion is coordinated by four nitrogen atoms (two Namino and two Ncyano) from four different m-abn ligands to form a [AgN4] distorted tetrahedral coordination geometry [Ag1−N2i = 2.301 (2) and Ag1−N1 = 2.354 (2) Å], and the angles around it fall in the range of 93.86(11)−133.86(8)o. The distortion of the tetrahedron can be indicated by the calculated value of the τ4 parameter introduced by Houser17 to describe the geometry of a four-coordinate metal system, which is 0.89 for Ag1 (for perfect tetrahedral geometry, τ4 = 1). The Ag−N bond lengths are obviously longer than Ag−Nheterocycle bond lengths,18 which indicates the weak coordinative abilities of both Namino and Ncyano atoms. It is noteworthy that two symmetry-related Ag(I) ions are ligated by a pair of μ2-m-abn ligands with a head-to-tail fashion to form a centrosymmetric [Ag2(m-abn)2] 14membered ring, which links each other to form an infinite 1D chain by sharing vertex Ag(I) ions (Figure 1b). As shown in Figure 1c and 1d, the 1D chain can be extended into a 2D network by the hydrogen bond between NO3− anion and 356



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Figure 2. (a) Coordination environment of the Ag(I) ion and the linkage mode of ligand in 2 with 50% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity. (b) The binuclear [Ag2(mabn)6] molecule. (c) The 2D network extended by hydrogen bonds. (d) The π···π interactions between adjacent binuclear motifs. Symmetry code: (i) −x + 1, −y + 1, −z + 1.

Figure 1. (a) Coordination environment of the Ag(I) ion and the linkage mode of ligand in 1 with 50% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity. (b) The 1D chain viewed along the a-axis. (c) The 2D network extended by hydrogen bond. (d) The 3D supramolecule. Symmetry codes: (i) −x + 1/2, −y + 1/2, −z + 1; (ii) x + 1/2, −y + 1/2, z + 1/2; (iii) −x + 1, y, −z + 3/2; (v) −x, y, −z + 3/2.

120.17(11)°. In addition to the coordination bonds, a weak Ag···O interaction [Ag1···O3ii = 2.904(3) Å] also exists, which falls in the secondary bonding range (the sum of van der Waals radii of Ag and O is 3.24 Å).19 Two Ag(I) ions are linked by two μ2-N,N′- and four μ1-N-m-abn ligands to form a centrosymmetric binuclear [Ag2(m-abn)6] motif (Figure 2b). The Namino−H···OClO4− hydrogen bonds [average N−H···O = 3.189(4) Å] and Namino−H···Ncyano hydrogen bond [N5− H5C···N4i = 3.169(5) Å] arrange the binuclear motifs into a 2D network (Figure 2c), which is consolidated by two kinds of π···π interactions [as shown in Figure 2d and Table S2 in the Supporting Information, the average centroid···centroid distance and dihedral angle are 3.796(3) Å and 5.38°, respectively] [symmetry codes: (i) −x + 1, −y + 1, −z + 1; (ii) −x + 3/2, y + 1/2, −z + 3/2]. {[Ag(o-abn)2]·NO3}n (3). When o-abn is used as an N-donor ligand and reacts with AgNO3, compound 3 is obtained as a 1D coordination polymer. It crystallizes in the monoclinic space group P2/c. The asymmetric unit of 3 consists of a half of Ag(I) ion, one o-abn ligand, and a half of NO3− anion. Two independent 2-fold axes pass through the Ag1 and N3−O1 bond of NO3− anion, respectively. As shown in Figure 3a, the

m-abn [N1−H1A···O1 = 2.953(2) Å]. The intersheet N−H···O hydrogen bond [N1−H1C···O2iv = 3.113(3) Å] contributes to the stability of the resulting 3D supramolecular framework [symmetry codes: (i) −x + 1/2, −y + 1/2, −z + 1; (iv) −x + 1/2, y + 1/2, −z + 3/2]. {[Ag2(m-abn)6]·(ClO4)2} (2). X-ray crystallographic analysis revealed that compound 2 crystallizes in the monoclinic P21/n space group. There is one Ag(I) ion, three m-abn ligands, and one ClO4− anion in the asymmetric unit. As illustrated in Figure 2a, the Ag1 adopts distorted [AgN4] tetrahedral geometry, where only one N atom comes from cyano group of the m-abn ligand and the rest of the N atoms are from the amino group of three different o-abn ligands. The τ4 parameter is 0.85 for Ag1. The Ag−Ncyano bond length is 2.544(3) Å, and the Ag−Namino bond lengths fall in the range 2.314(3)− 2.331(3) Å. The angles around Ag1 span from 90.94(11) to 357



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Figure 3. (a) Coordination environment of the Ag(I) ion and the linkage mode of ligand in 3 with 50% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity. (b) The 1D chain structure. (c) The 2D network extended by hydrogen bonds. (d) The π···π interactions between adjacent chains. Symmetry codes: (i) −x + 1, y, −z + 1/2; (ii) −x + 1, y − 1, −z + 1/2; (iii) x, y − 1, z; (vi) −x, y, −z + 1/2.

Figure 4. (a) Coordination environment of the Ag(I) ion and the linkage mode of ligand in 4 with 50% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity. (b) The 2D network constructed by two kinds of helix. (c) The hydrogen bonds within the 2D network. Symmetry codes: (i) −x + 1/2, y + 1/2, −z + 3/2; (ii) −x + 3/2, y − 1/2, −z + 3/2.

Ag(I) ion adopts a distorted [AgN4] tetrahedral geometry by coordination with two Namino and two Ncyano atoms [Ag1−N2i = 2.353(3) and Ag1−N1 = 2.316(3) Å], and the angles around it fall in the range 88.11(13)−127.00(9)°. The τ4 parameter is 0.75 for Ag1. Two Ag(I) ions are ligated by a pair of μ2-N,N′-oabn ligands with a head-to-head fashion to form a [Ag2(o-abn)2] 12-membered ring, which links each other to form an infinite 1D chain (Figure 3b). Furthermore, the 1D chain is extended to a 2D network by two kinds of hydrogen bonds [N1− H1A···O1 = 2.880(3) and N1−H1B···O2iv = 2.959(4) Å; Figure 3c]. Then, it is extended to a 3D supramolecular framework by π···π interaction [as shown in Figure 3d and Table S2 in the Supporting Information, the centroid···centroid distance and dihedral angle are 3.708(2) Å and 0°, respectively] [symmetry codes: (i) −x + 1, y, −z + 1/2; (iv) x, y + 1, z]. [Ag(o-abn)2(NO2)]n (4). When the NO3− anion of 3 is replaced by the NO2− anion, a 2D net structure is produced, which crystallizes in the monoclinic space group P21/n. As shown in Figure 4a, the asymmetric unit of 4 consists of one Ag(I) ion, one o-abn ligand, and one NO2− anion. Each Ag(I) ion is five-coordinated in a distorted square pyramidal coordination geometry by three oxygen atoms from two

NO2− anions with an average Ag−O bond length of 2.491(8) Å and two N atoms from two μ2-N,N′-o-abn ligands [one Namino and one Ncyano, Ag−Namino = 2.466(9) and Ag−Ncyano = 2.328(10) Å]. The angles around Ag1 range from 49.4(2) to 133.9(3)°. The distortion of the trigonal bipyramidal geometry can be indicated by the calculated value of the τ5 parameter introduced by Addison20 to describe the geometry of a fivecoordinated metal system, which is 0.05 for Ag1, indicating that the Ag1 locates in a square pyramidal geometry (for a trigonal bipyramidal structure with D3h symmetry, τ5 = 1, then for a square pyramidal structure with C4v symmetry, τ5 = 0). As shown in Figure 4b, a 2-fold left-handed helix is constructed by Ag(I) ion and o-abn ligand alternately, and then, the NO2− anions extended the helix into 2D network by coordination with Ag ions by μ2-η2:η1 mode; meanwhile, another kind of 2-fold helix (right-handed) is constructed by O atoms and Ag ions. These two kinds of 2-fold helices arrange in an alternating left-handed and right-handed fashion with the same pitch [5.828(4) Å, cyclical Ag···Ag separation] along the b-axis. The hydrogen bonds between Namino and NO2− also reinforce the 2D network. 358



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{[Ag(o-abn)2]·PF6}n (5). When the PF6− is used to replace the NO3− anion of 3, the 1D chain is formed. The asymmetry unit of 5 consists a half of Ag(I) ion, one o-abn ligand, and a half of PF6− anion. One 2-fold axis passes through the Ag1, giving it half-occupancy, and the PF6− locates on the inversion center. As shown in Figure 5a, the Ag(I) ion adopts distorted

Anion Influence on Structures of Silver(I)/abn Coordination Compounds. On the basis of the above results, the roles of the anions in determining the structures of the CCs are unambiguously exhibited. The nature (coordinating ability, size, and geometry) of the anions is the primary reason behind the dissimilarities in the structures of two series of Ag(I) CCs.21 We assume that the anion's influence on these structures is attributed to two aspects. One is the diverse coordination sphere of d10 Ag(I) ions. It is known that the coordination geometies of Ag(I) CCs are easily changed because d-orbitals are completely occupied by electrons to give the spherical electronic configuration. Although all Ag(I) centers in 1−3 and 5 are four-coordinated, different anions exert impact on the distortion degree of tetrahedral geometry, which can be defined by the τ4 parameter (0.89 for 1, 0.85 for 2, 0.75 for 3, and 0.93 for 5). For 4, the NO2− is the only coordinative anion in this system, which induces the Ag(I) center to adopt a square pyramidal coordination geometry. Another aspect is the coordination modes of abn ligands. To the best of our knowledge, only few coordination polymers have been reported involving abn ligands, and most of them are not linking ligands. They usually solely coordinate to the metal center by the amino group or cyano group.22 In this system, the abn ligands adopt bidentate μ2-N,N′ mode in 1 and 3−5, while the concurrent bidentate μ2-N,N′ and monodentate μ1-N m-abn ligands are observed in 2 exceptively. For 1 and 2, the variation of anions from trigonal-planar NO3− to tetrahedal ClO4− results the dimensionalities of 1 and 2 decrease from 1D to 0D. For 3−5, their structures vary from 1D chain to 2D net in the presence of different anions. For the 1D chain structures of 3 and 5, the arrangements of o-abn in [Ag2(o-abn)2] 12-membered rings are also distinct (head-to-head for 3 and head-to-tail for 5, Scheme 2). In a word, different anions are responsible for the structural diversity of the resultant coordination networks. Scheme 2. Arrangements of the o-abn Ligands in the 12-Membered Rings of Compounds 3 and 5

Figure 5. (a) Coordination environment of the Ag(I) ion and the linkage mode of ligand in 5 with 50% thermal ellipsoid probability. Hydrogen atoms are omitted for clarity. (b) The 1D chain structure. (c) The 2D network extended by hydrogen bond. (d) The π···π interactions inside the 1D chain. Symmetry codes: (i) −x + 1, −y + 1, −z + 2; (ii) x, −y + 1, z − 1/2; (iii) −x + 1, y, −z + 3/2; (v) −x, −y + 1, −z + 1.

IR Spectra, X-ray Powder Diffraction Analyses, and Thermal Analyses. The IR spectra (Figure S1 in the Supporting Information) of compounds 1−5 show features attributable to the amino and cyano groups stretching vibrations. Their IR spectra exhibit strong absorptions centered at ∼3400 to ∼3300 cm−1 corresponding to asymmetric and symmetric N−H stretching bands of amino group. The peak at ∼2200 cm−1 can be assigned to the characteristic vibrations of CN of the cyano group. Powder X-ray diffraction (XRD) has been used to check the phase purity of the bulky samples in the solid state. For compounds 1−5, the measured XRD patterns closely match the simulated patterns generated from the results of single-crystal diffraction data (Figure S2 in the Supporting Information), indicative of pure products. The dissimilarities in intensity may be due to the preferred orientation of the crystalline powder samples. The TG analysis was performed in N2 atmosphere on polycrystalline samples of compounds 1−5, and the TG curves

[AgN4] tetrahedral geometry by coordination with two Namino and two Ncyano [Ag1−N2i = 2.299 (2) and Ag1−N1 = 2.3490 (18) Å] and the angles around Ag1 range from 103.65(7) to 117.61(9)°. The τ4 parameter is 0.93 for Ag1 [symmetry code: (i) −x + 1, −y + 1, −z + 2]. Two Ag(I) ions are ligated by a pair of oppositely arranged μ2-N,N′-o-abn ligands to form a centrosymmetric [Ag2(o-abn)2] 12-membered ring, and the binuclear Ag(I) units link each other to form an infinite 1D chain by sharing Ag(I) ions (Figure 5b). Furthermore, the 1D chain is extended to a 2D network by hydrogen bonds between Namino and F atoms [N1− H1A···F2iv = 3.186(3) and N1−H1B···F2v = 3.099(3) Å; Figure 5c]. The π···π interactions exist within the 1D chain [Figure 5d and Table S2 in the Supporting Information, the centroid···centroid distance and dihedral angle are 3.7197(13) Å and 6°, respectively] [symmetry codes: (iv) −x, y, −z + 3/2; (v) −x, −y + 1, −z + 1]. 359



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(λex = 270 nm) for 3, 386 nm (λex = 270 nm) for 4, and 402 nm (λex = 300 nm) for 5 are observed at room temperature, which are similar to that of the corresponding abn ligands. These broad emissions of compound 1−5 could originate from π* → π IL (intraligand) transitions or with the admixture of IL and MLCT (metal-to-ligand charge transfer) characters.25

are shown in Figure 6. In five compounds, only 4 have two identifiable weight loss steps, and the rest four compounds have

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CONCLUSIONS Using two abn isomers, we synthesized and characterized two series Ag(I)/abn CCs under the ultrasonic treatment. They show diverse structures and dimensionalities from 0D binuclear molecule (2), 1D chains with different [Ag2(abn)2] rings (1, 3, and 5) to a 2D sheet (4). The changes of structure result from the various anions with different geometries, coordinative abilities, and sizes that induce the different coordination spheres of Ag(I) ions and different arrangements and coordination fashions of abn ligand. In addition, such CCs display modest thermal stability and strong solid-state photoluminescent emission.

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Figure 6. TGA curves for compounds 1−5.

ASSOCIATED CONTENT

S Supporting Information *

only one weight loss step. However, the initial decomposition temperatures of 1−3 and 5 are obviously different with each other. In 4, the metal−organic frameworks start to decompose at about 100 °C, accompanying a loss of organic ligands with two stages (calcd and found: 39.7 and 41.4%), while 1−3 and 5 start to decompose at about 150, 80, 120, and 170 °C, respectively, accompanying the release of the abn ligand and anions (calcd and found: 26.6 and 27.9% for 1, 19.2 and 17.8% for 2, 26.6 and 28.1% for 3, and 22.1 and 23.2% for 5). Photoluminescence Properties. Emissive CCs are of great current interest because of their various applications in chemical sensors, photochemistry, and electroluminescent display.23 Thus, the photoluminescence properties of 1−5 as well as free ligands were examined in the solid state at room temperature (Figure 7). The m-abn and o-abn ligands display

Crystallographic data in CIF format, additional figures of the structures, hydrogen-bonding geometries, powder X-ray diffraction (PXRD) patterns,and IR spectra for 1−5. This material is available free of charge via the Internet at http:// pubs.acs.org.

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AUTHOR INFORMATION Corresponding Authors *Fax: +86-531-88364218. E-mail: [email protected] (D.S.). Fax: +86-592-2183047. E-mail: [email protected] (R.-B.H.). Author Contributions § These authors contributed equally to this work.

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ACKNOWLEDGMENTS This work was financially supported by the National Natural Science Foundation of China (No. 20721001) and Project (Grant 2007CB815301) from MSTC and Independent Innovation Foundation of Shandong University, IIFSDU (2011GN030).

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REFERENCES

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Figure 7. Photoluminescences of free ligands and compounds 1−5.

photoluminescent emissions at 375 and 408 nm, respectively, under 300 nm radiation, which are probably attributed to the π* → π transition.24 The intense emission bands at 395 nm (λex = 300 nm) for 1, 437 nm (λex = 300 nm) for 2, 382 nm 360



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Aminobenzonitrile Compounds

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