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Structural Transformations Induced by Selective and Irreversible Anion-Exchanges for a Layered Ag(I) Nitrite Coordination Polymer Cheng-Peng Li, Hang Zhou, Yu-Hai Mu, Wei Guo, Yan Yan, and Miao Du Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.7b00020 • Publication Date (Web): 10 Mar 2017 Downloaded from http://pubs.acs.org on March 11, 2017

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Crystal Growth & Design

Structural Transformations Induced by Selective and Irreversible Anion-Exchanges for a Layered Ag(I) Nitrite Coordination Polymer Cheng-Peng Li, Hang Zhou, Yu-Hai Mu, Wei Guo, Yan Yan, and Miao Du*

College of Chemistry, Tianjin Normal University, Tianjin 300387, P. R. China

* Corresponding author. E-mail: [email protected].


ACS Paragon Plus Environment

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ABSTRACT: A series of AgI coordination polymers, {[Ag2L][Ag1/2(ONO)2(NO2)1/2](H2O)}n (1), {[AgL](BF4)}n (2), and {[Ag2L2](ClO4)2}n (3), have been prepared by assembly of AgX (X− = NO2−, BF4−, and ClO4−) with 3,4-bis(2-pyridyl)-5-(4-pyridyl)-1,2,4-triazole (L). Single-crystal Xray diffraction analyses indicate that 1–3 show distinct two-dimensional (2D) networks and lattice stacking, with the counter anions [Ag1/2(ONO)2(NO2)1/2]2–, BF4−, and ClO4− located in the interlayered voids. Interestingly, when the crystals of 1 were immersed in a water solution of BF4− or ClO4− anion, 2 or 3 can be irreversibly formed via anion-driven structural transformation. This process has also been investigated by means of PXRD, elemental analysis, FT-IR and SEMEDS, revealing a solvent-mediated mechanism. Moreover, the dynamic anion-exchange behavior is highly anion-selective but cation-independent.


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Introduction In the field of crystal engineering, anionic components play an important role in construction of crystalline supramolecular systems.1–9 Nitrite, a toxic anion in vivo, is also a well-known ambidentate ligand and capable of binding to metal ions via its N or O donors, resulting in the phenomenon of nitro–nitrito linkage isomerism.10,11 Moreover, the use of nitrite to construct coordination polymers (CPs) has been achieved in recent years,12–15 although success is quite scarce, probably owing to the limited source of nitrite, mainly including NaNO2, KNO2, AgNO2 and MI3[MIII(NO2)6]. At present, the synthetic approach to nitrite-involved CPs is dominantly based on the combination of transition metal salts with sodium nitrite,12,13 but obviously, the nitrite anion is likely absent from the final products due to the competition of anions. Coordination polymers have shown important applications in a wide range of realms.16–22 In this context, selective anion-exchange or separation with CPs is of great interest, because anions play a critical role in many chemical and biological processes.23–25 Though resins with cationic groups and exchangeable counterions are currently viewed as the standard ion-exchange materials, CPs exhibit a sign of promising future for their higher thermal and chemical stability. Normally, the CPs for anion exchanges can be assembled with neutral organic ligands and metal ions to construct the cationic frameworks, where the charge-balancing anions will occupy the lattice voids and sometimes, are weakly coordinated to the metal ions. In most cases, the lattice or weakly interacted anions can be involved in the anion-exchange process,26–28 even in a single-crystal to single-crystal mode. However, the exchange of coordinated anions seems more difficult, as such process is always concomitant with the reorganization of coordination bonding and moreover, the modification of framework. As a consequence, the examples for structural transformations of CPs induced by anion-exchange with the variation of coordination bonding and network structures


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have been rarely known so far.29–32 As a matter of fact, there is only one report on anion-exchange by nitrite involving the reformation of coordination network, in which the structural transformation from a 1D helix to a 0D molecular loop occurs.15 In this work, we describe a series of twodimensional (2D) CPs constructed by 3,4-bis(2-pyridyl)-5-(4-pyridyl)-1,2,4-triazole (L) and AgX salts (X− = NO2− for 1, BF4− for 2, and ClO4− for 3). Interestingly, the coordinated nitrite in 1 can be fully exchanged by tetrafluoroborate and perchlorate in water solution to produce 2 and 3. Such exchange behaviors represent solvent-mediated structural conversions between different 2D networks of 1–3 (Scheme 1).

Scheme 1. Representative diagram of the anion-exchange behaviors from 1 to 2 or 3.

Experimental Section Materials and General Methods. All starting reagents were obtained commercially and used as received, except the ligand L which was prepared according to a literature method.33 Distilled water was used throughout. Elemental analyses were taken on a CE-440 (Leemanlabs) analyzer. IR spectra (KBr pellets) were recorded on an AVATAR-370 (Nicolet) spectrometer. Powder Xray diffraction (PXRD) patterns were measured on a Rigaku D/Max-2500 diffractometer (40 kV and 100 mA) for a Cu-target tube (λ = 1.5406 Å), with a scan speed of 2 °/min and a step size of 0.02° in 2θ. The calculated PXRD patterns were produced from the single-crystal diffraction data with the PLATON software. Thermogravimetric analysis (TGA) experiments were performed on a NETZSCH TG209 thermal analyzer from 25 to 650 °C at a heating rate of 10 °C/min under N2


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atmosphere. Solid-state fluorescent spectra were performed on a Cary Eclipse spectrofluorimeter (Varian) at ambient temperature. Field emission scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were taken using a Nova Nano SEM 230 (FEI) scanning electron microscope equipped with Genesis Apollo 10 (EDAX). UV-Vis diffuse reflectance spectra were recorded on a Hitachi UH-4150 spectrometer. Synthesis of 1–3. {[Ag2L][Ag1/2(ONO)2(NO2)1/2](H2O)}n (1). A methanol solution (10 mL) of L (30.0 mg, 0.1 mmol) was carefully layered on an aqueous solution (10 mL) of AgNO2 (15.3 mg, 0.1 mmol) in a straight glass tube, which was left to stand in darkness at room temperature. Colorless block crystals of 1 were obtained by slow evaporation of the solvent after ca. one week. Yield: 18.2 mg (65%, based on AgI). Anal. Calcd for C17H14Ag2.5N8.5O6: C, 29.04; H, 2.01; N, 16.94%. Found: C, 29.18; H, 1.92; N, 16.79%. IR (cm−1): 3433b, 1586s, 1459s, 1416m, 1270vs, 1066w, 1017w, 989w, 825w, 797m, 745m, 722m, 627w, 605m, 534w. {[AgL](BF4)}n (2). The same synthetic procedure as that for 1 was used except that AgNO2 was replaced by AgBF4 (19.5 mg, 0.1 mmol), forming colorless block crystals of 2 after ca. three days in a yield of 56% (27.7 mg). Anal. Calcd for C17H12AgBF4N6: C, 41.25; H, 2.44; N, 16.98%. Found: C, 41.33; H, 2.28; N, 17.16%. IR (cm−1): 1599s, 1524w, 1463s, 1346w, 1292w, 1058vs, 830m, 799m, 749m, 725m, 611s, 568w, 522m. {[Ag2L2](ClO4)2}n (3). The same synthetic route as that for 1 was used except that AgNO2 was replaced by AgClO4·H2O (22.5 mg, 0.1 mmol), forming colorless block crystals of 3 after ca. five days in a yield of 63% (32.0 mg). Anal. Calcd for C34H24Ag2Cl2N12O8: C, 40.22; H, 2.38; N,


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16.56%. Found: C, 40.39; H, 2.29; N, 16.62%. IR (cm−1): 1596m, 1526w, 1463s, 1422m, 1344w, 1248w, 1086vs, 1010w, 999m, 830m, 804m, 750m, 726m, 698w, 621s, 537w. Single Crystal X-Ray Diffraction. Data collection was performed on a Bruker Apex II CCD diffractometer at ambient temperature with Mo Kα radiation (λ = 0.71073 Å). In each case, there was no evidence of crystal decay during data collection. A semi-empirical absorption correction was applied using SADABS and the program SAINT was used for integration of the diffraction profiles.34 All structures were solved by direct methods with SHELXS program and refined with SHELXL.35 The non-H atoms were modeled with anisotropic thermal parameters and refined by full-matrix least-squares methods on F2. In general, C-bound H atoms were placed geometrically and refined as riding, whereas O-bound H atoms were firstly located in difference Fourier maps, and then fixed in the calculated positions. Further details for crystallographic data and refinement conditions are listed in Table 1, and selected bond parameters are shown in Table S1. (Insert Table 1 here) Results and Discussion Crystal Structure of {[Ag2L][Ag1/2(ONO)2(NO2)1/2](H2O)}n (1). 1 shows a 2D polymeric structure, and the asymmetric unit consists of two and a half AgI ions, one L ligand, two and a half NO2– anions, and one lattice water. As depicted in Figure 1a, the coordination environments of three independent AgI ions are different. Ag1 adopts a trigonal N3-coordination geometry, surrounded by one 4-pyridyl group and two triazole groups from three L ligands. The Ag2 center takes a square planar N4-coordination geometry with four 2-pyridyl groups from two L ligands around it. Ag3 displays a trigonal NO2-coordination sphere with three independent nitrite ligands bound with their N (N7 containing) or O atoms (N8 and N9 containing). Thus, those three nitrite


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anions adopt the nitro-η1-κN and nitrito-η1-κO coordination modes, respectively (Figure S1a). It is well known that the nitrite anion can exhibit flexible nitro- and nitrito-binding fashions whereas the coexistence of such two modes within the same structure is quite unusual.4 Of further importance, the [M(ONO)x(NO2)y] subunit has not been documented for nitrite coordination chemistry so far. The L ligand takes the cis-I-(η5, µ4) coordination mode (Figure S1b) to interlink the Ag1 and Ag2 ions to form a 2D network (Figure 1b left). In this polymeric layer, a pair of Ag1 centers are connected by two triazole groups of paired L ligands to form a [Ag2N4] ring, with the Ag···Ag distance of 4.010(6) Å. Topological analysis suggests a binodal (3,4)-connected network with the point symbol of (42.6)(42.63.8), considering Ag1 and L as the three- and four-connected nodes, respectively (Figure 1b right). Alternatively, if the binuclear [Ag2N4] unit is considered as a node, the overall layer can also be simplified into a (3,4)-connected network but with a (4.62)2(42.62.82) topology. Further structural analysis of 1 indicates that such wavelike networks are arranged in a parallel way to allow interspace among them (336.1 Å3, 30.3% per unit cell volume as estimated by PLATON36), occupied by the airfoil-like [Ag1/2(ONO)2(NO2)1/2]2– units and lattice aqua molecules (Figure 1c). The cationic [Ag2L]2+ network and anionic [Ag1/2(ONO)2(NO2)1/2]2– units are weakly interacted through the longer Ag···O contacts of 2.778(4)–2.792(5) Å. Further structural analysis reveals the presence of multiple weak C−H···O interactions involving the L ligands, lattice water molecules and nitrite anions (C···O = 3.308–3.469 Å, C−H···O =128–159°, Table S2), and aromatic stacking interactions between the parallel pyridyl groups (centroid-to-centroid distances = 3.711–3.977 Å, Table S3) within the 2D layered networks. (Insert Figure 1 here)


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Crystal Structure of {[AgL](BF4)}n (2). The structure of 2 also indicates a 2D network, in which the asymmetric unit consists of one AgI ion, one L ligand, and one lattice BF4– counterion. Each AgI center shows a tetrahedral N4-coordination geometry, ligating to two 2-pyridyl groups, one 4-pyridyl group, and one triazole ring from four different L ligands, respectively (Figure 2a). In this case, the neighboring AgI centers are interconnected by the trans-(η4, µ4) L ligands (Figure S1b) to afford a 2D layer, with the most familiar (4,4) motif by regarding both AgI ions and L ligands as the 4-connected nodes (Figure 2b). Moreover, the lattice BF4– anions are connected to the 2D layer via weak C−H···F interactions (C···F = 3.117–3.304 Å, C−H···F =124–156°, Table S2). Also, two types of intralayer π−π stacking interactions are observed between the parallel triazolyl groups as well as the 4-pyridyl rings of the L ligands with the centroid-to-centroid distances of 3.556(2) and 3.646(2) Å, respectively (Table S3). These parallel 2D layers are stacked without interlayer interactions and the voids between the layers are 119.0 Å3 (13.7% per unit cell volume), which can accommodate the lattice BF4– anions (Figure 2c). (Insert Figure 2 here) Crystal Structure of {[Ag2L2](ClO4)2}n (3). The asymmetric unit of 3 consists of two AgI ions, two L ligands, and two lattice ClO4– counterions (Figure 3a). The Ag1 center exhibits the tetrahedral N4-coordination geometry, provided by two 2-pyridyl groups, one 4-pyridyl ring, and one triazole group from four different L ligands. Ag2 adopts a trigonal N3-coordination sphere, surrounded by two triazole rings and one 4-pyridyl ring from three L ligands. Notably, the two crystallographically independent L ligands similarly adopt the cis-II conformation (Figure S1b) but distinct (η4, µ4) and (η3, µ3) coordination modes, where the triazole groups serve as the bidentate and monodentate ligands, respectively. As a result, a 2D coordination network is also formed (Figure 3b left). Interestingly, due to the different connectivity of the L ligands, two distinct 1D


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arrays are observed with ···ABAB··· sequence in each 2D layer. Further analysis indicates that such a 2D layer is topologically equivalent to that of 1, with a (3,4)-connected (42.6)(42.63.8) net (Figure 3b right). In this structure, two independent AgI centers can be considered as the 3- or 4connnected nodes and the two L ligands are also 3- or 4-connected connectors, respectively. Two types of intralayer π−π stacking interactions are found between the parallel triazole rings of one type of L ligands and 4-pyridyl groups of the other type of L ligands, respectively, with the centroid-to-centroid separations of 3.659(4) and 3.551(4) Å (Table S3). These corrugated 2D layers adopt a parallel stacking mode, generating interlayer voids along the [010] axis (Figure 3c). Also, the lattice perchlorate anions form multiple C–H⋅⋅⋅O hydrogen bonding with the 2D layer (C···O = 3.179–3.366 Å, C−H···O =125–165°, Table S2). Computation of the interspace with PLATON indicates a value of 278.3 Å3 (15.7% per unit cell volume), which is fully occupied by the ClO4– anions. (Insert Figure 3 here) Structural Transformations Induced by Anion-Exchanges. The structural transformations for CPs can be triggered upon different external stimuli, which have been well explored in recent years.37–39 In this work, the qualified single crystals for 2 and 3 could not be achieved via anion exchange and thus, IR, microanalysis, SEM, EDS, and PXRD techniques were applied to prove the conversions between 1 and 2/3. In a typical test for anion-exchange process, the as-synthesized single-crystals of 1 (0.1 mmol) were immersed in a H2O solution (20 mL) of AgBF4 or AgClO4 (1.0 mmol) and kept in darkness under mild stirring at room temperature. After ca. one week, the solids were filtrated off, washed with water, and dried in vacuum for further characterization. The IR spectra for anion-exchanged products illustrate the disappearance of intense absorption peak for NO2– anion at 1270 cm–1, and


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the appearance of strong band for BF4– or ClO4– anion at 1053 or 1090 cm–1, respectively (Figure S2). Moreover, SEM-EDS elemental mapping for the crystal samples after exchanged by AgBF4 or AgClO4 indicates a higher content of F or Cl element (Figures 4 and 5). The anion-exchanged solids are compositionally consistent with those for 2 and 3 according to the results of elemental analysis (Figure S3). These results indicate the preferential exchange of NO2– anion with BF4– or ClO4– under specific circumstance. (Insert Figure 4 and Figure 5 here) In addition, PXRD patterns of the anion-exchanged products suggest that each transformation affords the identical high purity phase of 2 or 3 (Figure 6). The SEM images (Figures 4a and 5a) and optical microscopy (Figure 7) indicate that the crystals of 1 turn to be more opaque in color and thinner in shape upon anion exchange, indicating a solvent-mediated process for such anioninduced structural transformations. The mechanism of anion exchange for CPs normally includes diffusion controlled “solid-state” exchange (as observed in ion-exchange resins and zeolites) and “solvent-mediated” dissolution and recrystallization of CPs. For the former, it implies that anion exchange proceeds through the diffusion of free ions within the channels of CP crystals. For the latter, it involves part dissolution of the initial crystals, followed by the formation and crystallization of a new phase from the solution, which thus represents a dynamic equilibrium. The reversible anion exchange occurs only if the starting and final crystals of CPs have comparable solubility. In this regard, Schröder et al have done much invaluable work,31 to demonstrate that ion exchange in AgI CPs with heterocyclic ligands occurs through a solvent-mediated mechanism. To confirm whether the anion-exchange reactions are reversible, the as-synthesized crystalline sample of 2 or 3 was similarly immersed in a water solution of AgNO2. The characterizations for products by microanalysis, IR, and PXRD obviously indicate that such processes are irreversible.


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As suggested,31 the structural transformation followed by a water-mediated mechanism can be explained by solubility of the starting and final crystals of CPs. In this case, solubility for 1–3 in water (20 °C) is ca. 0.31, 0.06, and 0.06 mmol L–1 (Table S4). The significant difference in solubility for 1–3 will result in the irreversible structural transformations from 1 to 2/3, which follow the water-mediated mechanism. (Insert Figure 6 and Figure 7 here) Moreover, while 1 was immersed into a water solution of NaX or KX (X = BF4– and ClO4–), 2 or 3 can also be readily obtained (Figure S4), which reveals that the anion-exchange reaction will be independent to the associated metal cations (Figure 8). Further attempts of the anion-exchange with other common univalent anions of Cl–, NO3– and CH3COO– and the bivalent anion of SO42– were unsuccessful (Figure S5 and Figure 8). Therefore, these structural transformations induced by selective anion-exchange can be presumably ascribed to the similar tetrahedral geometry and ionic radius (bond length: B–F = 1.38 Å vs Cl–O = 1.40 Å) of the targeted anions. Significantly, homologous BF4– and ClO4– anions result in distinct exchanged products 2 and 3, also indicating the sensitivity for such reactions. (Insert Figure 8 here) Structural Comparison. Considering the similar layered structures for CPs 1–3 and layered double hydroxides (LDHs), a comparison on their structural features and ion-exchange behaviors will be of significance. LDHs are lamellar mixed hydroxides containing positively charged main layers and undergoing anion exchange chemistry.40 The prominent difference between these two anion-exchange materials is that, during the anion-exchange process, the positive layers of LDHs normally show the rigid character with insignificant structural change, while CPs can suffer drastic structural transformations with breakage or formation of the coordination bonding.


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In this case, the L ligand in CPs 1–3 shows the flexible nature, in which the three substituted pyridyl rings can freely rotate to adopt different distortion angles to the central triazolyl group, to display the cis-I, cis-II, and trans-conformations (Figure S1). For 1, the L ligand features cis-I(η5, µ4) coordination mode, with the dihedral angles between the three substituted pyridyl groups and the central triazolyl ring of 53.8, 75.6, and 44.2°. Upon anion-exchange by BF4– to produce 2, the L ligand adopts trans-(η4, µ4) mode, where the three substituted pyridyl rings deviate from the triazole group by 57.8, 64.5, and 18.1°. As for the ClO4– exchanged product 3, two independent L ligands exhibit the similar cis-II conformation but distinct (η4, µ4) and (η3, µ3) coordination modes, and the three dihedral angles are 46.3/54.0/47.9° and 41.7/68.8/48.4°, respectively. Thermal Stability and Photoluminescence Properties. Considering the explosion hazard of perchlorate in 3, only the thermal stability of 1 and 2 was explored by TGA experiments (Figure S6). In TGA curve of 1, the first weight loss of 2.59% from room temperature to 180 °C reveals the exclusion of lattice water molecule (calculated: 2.56%). Then, the residual species undergoes a series of weight loss that will not end till heating to 650 °C. The solvent-free coordination solid 2 can be thermally stable to 280 °C, beyond which a mild weight loss occurs, followed by a quite sharp weight loss that does not stop until heating to 650 °C. Silver(I) CPs with the aromatic organic ligands represent potentially hybrid luminescent materials.41 Thus, solid-state fluorescent properties for 1–3 and the L ligand were explored at room temperature (Figure S7). The L ligand shows the maximal emission peak at 488 nm (λex = 342 nm), which should be ascribed to the π → π* and/or n → π* transitions. The excitation of microcrystalline solids for 1–3 at 325, 337, and 338 nm, respectively, leads to the generation of different fluorescent emissions with the peaks maxima observed at 523 nm (for 1), 470 nm (for 2), and 474 nm (for 3). The emission red-shift of 1 (∆λ = 35 nm) or blue-shift of 2 and 3 (∆λ = 18 and 14


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nm) may be attributed to the metal-to-ligand charge transfer (MLCT),41 and the obvious emission enhancement of their intensity compared with that of the free ligand is due to the increased rigidity of L ligand when bound to the AgI ions, which will effectively reduce the loss of energy.42–44 In addition, the UV-Vis diffuse reflection spectra (Figure S8) indicate a maximal absorption at 217 nm and a shoulder peak around 300 nm for the free L ligand, corresponding to the π→π* transitions of aromatic rings, while two clear absorption peaks are observed at 216 / 297 nm for 1, 220 / 290 nm for 2, and 218 / 289 nm for 3, respectively. Conclusions In conclusion, this work presents three 2D Ag(I) coordination polymers with different layered networks and stacking modes, where the coordinated nitrite anions can be irreversibly exchanged with tetrafluoroborate or perchlorate anions, being concomitant with solvent-mediated structural transformations. Such anion-exchange reactions possess the unique sensitivity to BF4– and ClO4–, affording structurally distinct products although both anions have similar tetrahedral geometries. Also, the anion-exchange processes exhibit extraordinary selectivity toward other familiar anions and are independent to the simultaneously ingoing metal cations. In fact, the structural transformations of 2D CPs are normally observed as hetero-dimensional transformations (from 2D to 1D or 3D)45,46 or homo-dimensional transformations (from 2D to 2D) where the 2D networks are intact with the exchange of interlayer guests.47,48 While in this work, interesting homodimensional structural transformations of 2D CPs are achieved with the breakage of coordination bonds and reconstruction of the 2D networks. Inspired by these results, further efforts on anioninduced structural transformations of dynamic CPs with such versatile multidentate ligands are underway in our lab, which may develop new functional crystalline materials with interesting properties and potential applications.


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ASSOCIATED CONTENT Supporting Information. Selective bond parameters, hydrogen bonding and π···π stacking geometries parameters, solubility experiments, coordination modes of nitrite, conformations of the L ligand, IR spectra, PXRD patterns, elemental analysis, TGA plots, solid-state fluorescent emission spectra, UV-Vis diffuse reflection spectra and crystallographic data (CIF). This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author * E-mail: [email protected] Notes The authors declare no competing ﬁnancial interest. ACKNOWLEDGMENT This work was supported by the National Natural Science Foundation of China (Nos. 21031002 and 21541002) and Innovation Foundation of Tianjin Normal University (No. 52XC1402).

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Table 1. Summary of the Crystallographic Data and Structural Refinements for 1–3.

1

2

3

C17H14Ag2.5N8.5O6

C17H12AgBF4N6

C34H24Ag2Cl2N12O8

Formula weight

703.04

495.01

1015.29

Crystal system

Triclinic

Triclinic

Triclinic

P-1

P-1

P-1

a (Å)

9.3174(13)

7.7368(6)

10.411(3)

b (Å)

10.4352(14)

9.6195(7)

12.850(3)

c (Å)

11.8586(17)

12.4365(10)

14.179(4)

α (°)

75.724(2)

97.7300(10)

74.398(5)

β (°)

87.395(2)

98.0100(10)

86.790(4)

γ (°)

82.698(2)

105.9940(10)

75.775(4)

V (Å3)

1108.2(3)

866.41(12)

1770.9(8)

2

2

2

2.107

1.897

1.904

682

488

1008

µ (mm−1)

2.250

1.222

1.330

Rint

0.0140

0.0119

0.0345

0.0327 and 0.0872

0.0332 and 0.0763

0.0583 and 0.1692

1.059

1.036

1.068

Empirical formula

Space group

Z

ρcalcd (g cm−3) F(000)

Ra and wRb GOF a

R = Σ||Fo| − |Fc|| / Σ|Fo|; b wR = [Σ[w(Fo2 − Fc2)2] / Σw(Fo2)2]1/2.


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Caption to Figures Figure 1

Views of 1. (a) Coordination environments of AgI (symmetry codes for A: −x, −y + 1, −z + 1; B: −x, −y + 2, −z + 1; C: −x, −y + 1, −z + 2; D: −x + 1, −y + 1, −z + 1). (b) The 2D coordination network and its topologically equivalent pattern. (c) Crystal packing of the 2D layers, with the airfoil-like [Ag1/2(ONO)2(NO2)1/2] entities in the interspace.

Figure 2

Views of 2. (a) Coordination environment of AgI center (symmetry codes for A: −x + 2, −y + 1, −z + 2; B: −x + 3, −y + 2, −z + 2; C: x + 1, y, z). (b) A portion view of the 2D coordination network and its topologically equivalent pattern. (c) Crystal packing of the 2D layers, with the BF4– anions (space-filling model) in the interspace.

Figure 3

Views of 3. (a) Coordination environments of AgI centers (symmetry codes for A: x − 1, y, z; B: −x + 2, −y + 1, −z; C: −x + 1, −y + 1, −z + 1). (b) The 2D network and its topologically equivalent pattern. (c) Crystal packing of the 2D layers, with the ClO4– anions (space-filling model) in the interspace.

Figure 4

(a) SEM image and (b–d) EDS spectra for the exchanged product of 1 with AgBF4.

Figure 5

(a) SEM image and (b–d) EDS spectra for the exchanged product of 1 with AgClO4.

Figure 6

PXRD patterns for (a) the anion-exchanged product (1 + AgBF4), 1, and 2 as well as (b) the anion-exchanged product (1 + AgClO4), 1, and 3.

Figure 7

Crystal photos for 1 and the anion-exchanged products 2 and 3.

Figure 8

Results of anion-exchange experiments with other anions (Cl–, NO3–, CH3COO–, and SO42–) or cations (Na+ and K+), in which blue and red columns represent the positive and negative results, respectively, and black columns indicate the insoluble nature of metal salts (AgCl and Ag2SO4) in water.


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(a)

(b)

(c)


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Figure 1


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(a)

(b)

(c) Figure 2


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(a)

(b)

(c) Figure 3


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(a)

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(b)

(c)

(d)

Figure 4


24

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(a)

(b)

(c)

(d)

Figure 5


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1+ AgBF4 1 2

5

10

15

20

25

30

2θ (deg)

(a)

1+ AgClO4 1 3

5

10

15 20 2θ (deg)

25

30

(b)

Figure 6


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BF4–

2

ClO4–

1

3

Figure 7

Figure 8


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For Table of Contents Use Only

Structural Transformations Induced by Selective and Irreversible Anion-Exchanges for a Layered Ag(I) Nitrite Coordination Polymer Cheng-Peng Li, Hang Zhou, Yu-Hai Mu, Wei Guo, Yan Yan, and Miao Du* Structural transformations of a layered Ag(I) coordination polymer with coordinated nitrite could be driven by tetrafluoroborate or perchlorate anion to produce distinct 2D networks. The unprecedented anion-exchange behaviors are unidirectional, highly selective, and cation independent.


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Structural Transformations Induced by Selective ... - ACS Publications

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