Switching the Zinc Diphosphonates from 1D Chain to 2D Layer and

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Switching the Zinc-Diphosphonates from 1D Chain to 2D Layer and 3D Framework by the Modulation of a Flexible Organic Amine Jie Pan, Yu-Juan Ma, Song-De Han, Zhen-Zhen Xue, and Guo-Ming Wang Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.9b00139 • Publication Date (Web): 15 Apr 2019 Downloaded from http://pubs.acs.org on April 16, 2019

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Crystal Growth & Design

Switching the Zinc-Diphosphonates from 1D Chain to 2D Layer and 3D Framework by the Modulation of a Flexible Organic Amine

Jie Pan,† Yu-Juan Ma,† Song-De Han,*,† Zhen-Zhen Xue,† Guo-Ming Wang*,† †College

of Chemistry and Chemical Engineering, Qingdao University, Shandong 266071, China

Supporting Information ABSTRACT: A series of zinc-diphosphonates mediated by a long and flexible amine 1,2-bis(3-aminopropylamino)ethane (BAPEN), [Zn3(HEDP)2(H2BAPEN)(H2O)]·5H2O (1), (H4BAPEN)0.5·[Zn3(HEDP)2(H2O)]·2H2O (2) and (H4BAPEN)0.5·[Zn3(HEDP)2]·H2O (3) (HEDP = 1-hydroxyethylidenediphosphonate, CH3C(OH)(PO3)2), were successfully assemblied showing diverse structures with different dimensions. Compound 1 displays an infinite Zn-HEDP chain which is decorated by chelating BAPEN. For compound 2, it possesses an anionic Zn-HEDP layer structure with the protanated BAPEN as charge balancer. Compound 3 features a three-dimensional (3D) Zn-HEDP network with protonated BAPEN as the template. The structural diversity for 1-3 from 1D to 2D and 3D was modulated by BAPEN in the assembly process (coordination role for 1 and template role for 2 and 3) together with the different reaction conditions. The photoluminescence properties of compounds 1-3 are investigated. The results show that the solids 1-3 exhibit intense blue fluorescence at ambient temperature under UV light irradiation. Moreover, the proton conduction behavior for compound 3 has been studied.

INTRODUCTION Metal-organic materials (MOMs), as an emerging class of hybrid solids, have attracted huge interest thanks to their great diversity of structures as well as promising properties.1-5 As an important kind of MOMs, the metal-phosphonate has received continuous attention during the past three decades.6-11 The integration of metal ions and organophosphonates offers a good chance to generate versatile molecular materials bearing diverse structure (from isolated clusters to polymeric structure, such as metal-organic frameworks, MOFs) and appealing properties (adsorption, proton conductivity, optics, catalysis, magnetism, etc.).12-17 To fabricate diverse MOMs, the template-directed synthesis approach has been widely adopted and employed.18-24 Generally, the introduction of organoamine to metal-phosphate (or phosphite) greatly promoted the blossom of synthetic and structural chemistry, which indirectly pushed the exploration of promising structure-related properties and potential applications.25-27 Compared with the great achievement in organoamines-directed metal-phosphate (or phosphite), the metal-phosphonate driven by organoamines is still underdeveloped in terms of types and number. In view of the similarity between inorganic phosphorus units and phosphate, HPO32-) and (phosphate, PO43organophosphonates (RPO32−, R represents the organic moiety), the organoamines-directed assembly is feasible for the production of metal phosphonate. Hitherto, the early works mainly centered on the small molecular organoamines such as aliphatic or heterocyclic amine.28-30 While the long flexible aliphatic amine and large heterocyclic amine,31-35 by contrast, are relatively less investigated.

In our previous works, we have focused on the investigation of synthetic methodology with respect to novel metalphosphonates directed by various organic amines,36-41 including rigid heterocyclic amines (4,4'-bipyridine, 1,3,5tris(1-imidazolyl)benzene, 2,4,6-tri(4-pyridyl)-1,3,5-triazine) and small flexible organic amines (imidazole, 1,3propanediamine). As a continuous study on the exploration and acquisition of novel metal-phosphonate with both captivating structures and unique properties, we are attempting to select and graft the long and flexible organoamine 1,2bis(3-aminopropylamino)ethane (C8N4H22, BAPEN) to metal1-hydroxyethylidenediphosphonate system, on account of the following concerns: (a) the cheap diphosphonate HEDP with multiple coordination modes is helpful for the manufacture of phosphonate-based MOMs;42,43 (b) the zinc(II) ion with flexible coordination number (from 4 to 6 or even higher) and geometric configuration (tetrahedra, trigonal bipyramid and octahedra), is a promising candidate for the fabrication of phosphate-based MOMs;44-46 (c) the phosphonate-based MOMs possess advantages in seeking framework structure with high photoluminescence or other properties (Scheme 1).47 We, herein, reported three BAPEN-mediated zincdiphosphonates, [Zn3(HEDP)2(H2BAPEN)(H2O)]·5H2O (1), (H4BAPEN)0.5·[Zn3(HEDP)2(H2O)]·2H2O (2) and (H4BAPEN)0.5·[Zn3(HEDP)2]·H2O (3). Compound 1 has a ZnHEDP chain structure modified by BAPEN via chelating intrachain zinc ion. Unlike 1, compound 2 exhibits an anionic Zn-HEDP layer with the protanated BAPEN as charge balancer. While a protonated BAPEN-templated Zn-HEDP frame was constructed for compound 3. The diverse structures with 1D, 2D and 3D for compounds 1-3, respectively, were

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Table 1. Detailed crystal data for compounds 1-3.

Formula Mr (g mol-1) Space group Crystal system a (Å) b (Å) c (Å) α(°) β(°) γ(°) V (Å3) Z F(000) Dc (gcm-3) μ (mm-1) Rint Collected reflections Unique reflections GOF on F2 R1, wR2 [I>2σ(I)]a R1, wR2 [all data]b aR =∑ 1

1 C12H44N4O20P4Zn3 884.61 P21/n Monoclinic 11.841(3) 9.809(5) 27.911(5) 90 102.242(15) 90 3168(2) 4 1696 1.741 2.527 0.0783 9438 5524 1.048 0.0888 0.2082 0.1184 0.2442

2 C8H27N2O17P4Zn3 743.43 P-1 Triclinic 8.0782(8) 11.5706(14) 13.1353(11) 101.528(9) 98.969(8) 101.632(9) 1153.4(2) 2 730 2.088 3.448 0.0537 6177 4074 1.016 0.0581 0.1468 0.0858 0.1760

3 C8H23N2O15P4Zn3 707.39 C2/c Monoclinic 20.2470(11) 9.2107(7) 22.6219(13) 90 92.125(5) 90 4215.8(5) 8 2840 2.229 3.767 0.0259 8113 3709 1.114 0.0472 0.1385 0.0596 0.1480

||Fo| - |Fc||/∑|Fo| . b wR2={∑[w(Fo2 - Fc2)2]/∑w(Fo2)2}1/2

modulated by the organic amines in the process of assembly (coordination role for 1 and template role for 2 and 3) together with the distinct reaction conditions. The syntheses, structural characterization, photoluminescence and proton conduction properties for the compounds have been well investigated.

A mixture of 0.29 g ZnSO4 (1.00 mmol), 0.30 mL BAPEN (1.64 mmol), 0.28 mL H4HEDP (1.97 mmol) and 10 mL H2O was mixed together and put into a Teflon-lined autoclave with volumetric capacity of 20 mL. The content was heated and kept at 145 °C for 4 days, followed by the temperature cooling. Colorless sheet crystals could be acquired in a 60% yield on the basis of Zn. Elemental analysis (EA) (%) for C12H44N4O20P4Zn3 (Mr = 884.61), calcd: C, 16.29; H, 5.01; N, 6.33. Found: C, 16.58; H, 5.47; N, 6.13. IR (KBr pellets, cm–1): 3420(s), 2971(m), 2365(w), 1632(s), 1546(m), 1446(m), 1394(m), 1096(s), 1046(s), 996(m), 962(m), 876(m), 826(m), 668(m), 582(s), 513(w), 474(w). Preparation of (H4BAPEN)0.5·[Zn3(HEDP)2(H2O)]·2H2O (2). 0.29 g ZnSO4 (1.00 mmol), 0.28 mL BAPEN (1.53 mmol), 0.28 mL H4HEDP (1.97 mmol) and 10 mL H2O were mixed into a Teflon-lined autoclave. The mixture was allowed to heat to 160 °C in 2 hours and kept for 96 hours. After being cooled to 30 °C slowly, the plate-like colorless crystals could be obtained in a 35% yield on the basis of Zn. EA (%) calcd for C8H27N2O17P4Zn3 (Mr = 743.43): C, 12.92; H, 3.66; N, 3.77. Found: C, 12.73; H, 4.02; N, 3.35. IR (KBr pellets, cm–1): 3440(s), 2972(w), 2365(w), 1632(s), 1535(m), 1446(w), 1384(w), 1085(s), 1012(w), 966(s), 826(m), 668(m), 582(s), 480(m). Preparation of (H4BAPEN)0.5·[Zn3(HEDP)2]·H2O (3). A mixture of 0.29 g ZnSO4 (1.00 mmol), 0.20 mL BAPEN (1.09 mmol) and 0.28 mL H4HEDP (1.97 mmol) was put into a Teflon-lined autoclave, then 10 mL H2O was added. The content was kept at 160 °C for four days followed by the temperature cooling. Block colorless crystals were isolated in a 50% yield on the basis of Zn. EA (%) calcd for

Scheme 1. View of the structures for BAPEN and HEDP.

EXPERIMENTAL SECTION All chemicals (analytical grade) were bought and used directly without any purification. A Philips X’Pert-MPD diffractometer with a Cu-target tube was utilized to carry out the powder X-ray diffraction (PXRD) spectroscopy. Thermogravimetric (TG) measurement was performed on a NETZSCH STA 449 F5 analyzer with the temperature ranging from 30 to 800 °C with N2 as protective gas. Elemental analysis for C H N data were obtained from a Perkin-Elmer 240C analyzer. The MAGNA-560 FT-IR spectrometer was employed to conduct the IR spectroscopy. Photoluminescent spectra were obtained from a FLS920 spectrophotometer. The proton conduction behavior was studied on a Solartron 1287 electrochemical interface. Preparation of [Zn3(HEDP)2(H2BAPEN)(H2O)]·5H2O (1).

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Figure 1. (a) The asymmetric unit of 1; (b) the simplified chain along different directions; (c) the 1D zinc diphosphonate chain decorated by H2BAPEN; (d) the packing structure along b axis.

(Figure 1a). For Zn(1), the coordinative O-atoms are from water and –PO3 group of HEDP, while the coordinative Oatoms for Zn(2) are from –PO3 group of HEDP. The fivecoordinated Zn(3) exhibits a square pyramid [ZnO3N2] geometry, wherein the basal plane is composed of two Natoms from BAPEN ligand (Zn–N 2.140(9)/2.158(7) Å) and two O-atoms from a HEDP species, whereas the apical site is occupied by O-atom from another HEDP species. Each HEDP ligand features η1:η1:η1:η1:η1:η0:η0:μ3 mode to link three Zn2+ ions (the first six η represents the coordination mode of two – PO3 groups of HEDP, and the last η represents the coordination mode of –OH group of HEDP) (Figure S1). The bond lengths between Zn(II) and O atoms are in 1.912(7)2.115(7) Å, and the angles around Zn(II) ions range from 82.1(3)° to 159.7(3)°.49,50 The chelating-bridging HEDP ligand bonds with Zn-atoms to form a zinc diphosphonate chain as supramolecular building units, which are further linked by [ZnO3N2] square pyramid to generate the final double parallel chain (Figure1b). Notably, the protonated BAPEN (H2BAPEN) not only acts as chelating ligands to coordinate the Zn(3) atoms, but also serves as counter ions to balance the negative charge of the chain. The chelating H2BAPEN ligands feature relatively long flexible non-coordinative units, which hinds the further extension of the chain (Figure 1c, 1d). Intermolecular forces such as hydrogen bond (Table S4) between the guest BAPEN and the host extend the 1D chain to 3D solid-state packed structure.

C8H23N2O15P4Zn3 (Mr = 707.39): C, 13.58; H, 3.28; N, 3.96. Found: C, 13.73; H, 3.62; N, 4.27. IR (KBr pellets, cm–1): 3175(s), 2025(w), 1632(s), 1535(w), 1478(m), 1384(s), 1066(s), 1006(w), 966(w), 1094(s), 966(w), 826(s), 753(w), 680(s), 574(s), 504(w). Crystallographic data and refinement. Data collection for X-ray-quality crystals 1-3 were performed at room temperature on an XtaLAB-mini diffractometer with Mo-Kα radiation. The SHELX-2016 software was utilized to solve and refine the structures of 1-3.48 The highly disordered water molecules in the first two structures are treated by the “SQUEEZE” procedure in PLATON software suite. Through the TG curves and elemental analysis data, we calculated the final number of the guest molecules. Table 1 summarizes the detailed data and Table S1-S3 lists the selected bond distances and bond angles for the structures of 1-3. CCDC 1890697, 1890696 and 1890695 for 1, 2 and 3, respectively.

RESULTS AND DISCUSSION Structural description of [Zn3(HEDP)2(H2BAPEN)(H2O)]·5H2O (1). Compound 1 belongs to monoclinic P21/n space group with asymmetric unit containing three Zn(II) ions, two HEDP molecules, one H2BAPEN moiety, one coordinated and five guest water molecules. Both Zn(1) and Zn(2) centers are four-coordinated and adopt the [ZnO4] tetrahedral coordination geometry



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Figure 2. (a) The asymmetric unit of 2; (b) view of the Zn-HEDP layer; (c) and (d) the topological net and packing structure of 2.

and 4-connected nodes. Thus, based on this simplification, compound 2 can be treated as a new (3,4,5)-connected 4-nodal net with stoichiometry (3-c)(4-c)2(5-c) (Figure 2c). As illustrated in Figure 2d, the protonated BAPEN moieties as counter ions occupy the spaces between adjacent layers. Moreover, the parallel layers are gathered together through electrostatic interaction and hydrogen bond with the guest molecules (Table S5), to construct a 3D supramolecular architecture. Structural description of (H4BAPEN)0.5·[Zn3(HEDP)2]·H2O (3). Compound 3 belongs to monoclinic C2/c space group and presents a 3D framework. The asymmetric unit of 3 contains three Zn(II) ions, two HEDP molecules, a half of one protonated BAPEN and a guest water molecule. As displayed in Figure 3a, all Zn centers have a similar coordination geometry and locate in the [ZnO4] tetrahedron with the coordinative O-atoms coming from two different HEDP ligands. The Zn-O distances are from 1.895(4) to 1.988(4) Å, and the angles for O-Zn-O ranges from 99.64(19) to 125.0(2)°. The HEDP ligands in 3 display the η1:η1:η1:η1:η1:η1:η0:μ4 pattern to link four Zn atoms (Figure S3).51-54 Two Zn1 metal ions are linked by two HEDP molecules, generating the [Zn2(HEDP)2] dimeric moiety with Zn1···Zn1 distance being 4.490(7) Å. Meanwhile, another μ4-bridging HEDP ligands connect the Zn2 and Zn3 atoms with the Zn2···Zn3 distances being 4.704(4) Å, forming a 1D [Zn(HEDP)]n wave chain. These dimmers and 1D chains are alternatively interlaced by sharing O-atoms, generating an intricate 3D framework (Figure 3b). Notably, a 1D channel with size of 11.936 Å × 8.113 Å is observable along b axis (Figure S4),

Structural description of (H4BAPEN)0.5·[Zn3(HEDP)2(H2O)]·2H2O (2). It is revealed from the structural analysis that compound 2 belong to a lowsymmetrical triclinic crystal system with space group of P-1. There are three independent Zn(II) ions, two HEDP molecules, a half of one fully protonated BAPEN (H4BAPEN), one coordinated and two lattice water molecules in the asymmetric unit. As depicted in Figure 2a, Zn(1) and Zn(2) atoms adopt the four-coordinated mode and locate in the center of [ZnO4] tetrahedron whose vertexes are defined by four phosphonate O-atoms from two independent HEDP molecules. Unlike Zn(1) and Zn(2), Zn(3) adopts a six-coordinated [ZnO6] environment and locates in the center of a distorted octahedron. The equatorial positions are generated with four oxygen atoms from two HEDP molecules, and the axial positions are defined by one O atom from -OH of HEDP as well as one water molecule. The two HEDP ligands exhibit two different bridging modes: one displays the η1:η1:η1:η1:η1:η0:η0:μ4 mode to link four Zn2+ ions (Figure S2a); the second one shows the η1:η1:η1:η1:η1:η1:η1:μ5 pattern to connect five Zn2+ ions (Figure S2b). The distances between Zn and O centers are in the scope of 1.903(5)-2.343(5) Å, while the angles are found to be in the range of 76.89(17)-166.6(2)° around Zn(II) ions. The chelating-bridging HEDP moieties connect Zn-atoms to generate a 2D anionic layer in which two types of rings (4and 8-membered) exist and are constructed from vertexsharing of [ZnO6] octahedra, [ZnO4] and [CPO3] tetrahedra (Figure 2b). To assist the better understanding of this intricate layer, topology analysis is introduced. The two HEDP units could be considered as a 4- and 5-linked node, respectively. While for different Zn centers, they could be regarded as 3-


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Figure 3. (a) The asymmetric unit of 3; (b) and (c) view of the 3D framework along c and b axis; (d) the (3,4)-connected net of 3.

Zn···Zn distances of 4.490(7) and 4.704(4) Å, respectively. These two kinds of building units are alternatively interweaved with each other, generating the 3D 3,4-connected architecture. Moreover, structural analysis demonstrates that the flexible organic amine plays a critical role on the fabrication of different structures, as the coordination role results in a 1D chain for 1 while the template role gives rise to 2D layer and 3D network for 2 and 3, respectively. In a word, the structural differences indicate that conformations and coordination modes of organic amine as well as reaction conditions influence the construction of structures with different dimensions for compounds 1-3. Distinct from the metal-phosphonates directed by the small or rigid heterocyclic amines, such as (HN(C2H5)3)4[Zn7(L)6]·2H2O,29 [H2pip]3[Ge(hedp)2]·14H2O,30 [H3TPT][Zn3(CH3C(O)(PO3)2)(CH3C(O)(PO3)2H)]·(H2O),41 the long and flexible organoamine (BAPEN)-directed metal diphosphonates are seldom reported in spite of some metalphosphates (or phosphites) with BAPEN as the template have been investigated including [C8N4H26][Zn3Cl(HPO4)3(PO4)],57 [C8N4H26][Ga6F4(PO4)6]58 and so on. BAPEN contains eight methylene groups, which can generate different bond angles through the rotation of C-C bonds to conform to the space requirement. On the other hand, four amino units of BAPEN can also be deprotonated to coordinate to metal ions or protonated to serve as cationic species. Though the assembly of suitable metal ions with HEDP to fabricate desirable metaldiphosphonates has been reported, the structures of compounds 1-3 are different with the reported ones due to the different template. In view of the developmental synthesis strategy, the employment of long and flexible organoamine as template is an excellent choice for the generation of novel structures and topologies.

where contains the protonated BAPEN molecules (Figure 3c). Topology analysis is conducted to comprehend the complicated 3D framework. If the two HEDP units are regarded as 4-connected nodes, and the Zn centers are viewed as 3- and 2-connected nodes (2-connected nodes are omitted), the 3D skeleton of 3 thus could be delineated as a (3,4)connected net with (4·5·6·83)(4·6·8)(52·6·83)(52·8) point symbol (Figure 3d).

Structural diversity and comparison of 1-3. As described above, compounds 1-3 possess quite different architectures. All of them are constructed by sulfates and thus the influence of anion can be neglected. Compared with the syntheses and structures of 1-3, it could be indicated that the dosage of structure-directing agents as well as temperature play remarkable roles on the formation of zincdiphosphonates. 55,56 Compound 1 shows a 1D double chain constructed from Zn centers, HEDP ligands, and H2BAPEN molecules, in which HEDP displays two kinds of μ3connection modes. The neighbouring Zn···Zn distance separated by μ3-HEDP is 3.903(9)-6.028(2) Å. In order to generate different structural motifs, various reaction conditions were employed and adjusted in compounds 2 and 3. When less BAPEN was used at a higher temperature 160 °C, compound 2 with 2D grid-like network was obtained. In 2, – PO3 groups of HEDP with tetradentate and pentadentate bridging modes link the neighboring Zn centers to generate 2D inorganic-organic hybrid layer. The uncoordinated HEDP in 2 is doubly protonated to become a cationic structure-directing agent. When decreasing the amount of HEDP in compound 3, as expected, a novel 3D framework was obtained. Each HEDP in 3 adopting a μ4 mode links the adjacent Zn cations to yield two types of building blocks, in which there are two kinds



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Figure 6. The Nyquist plots of 3 at various temperature under 100% relative humidity.

Figure 4. The TG plots of 1-3.

TG and PXRD analyses. TG measurements for powder

Photoluminescence and proton conduction behavior.

samples 1-3 were performed under N2 atmosphere from 30 to 800 °C. The TG curves for the compounds are displayed in Figure 4. A weight loss of 9.01% for 1 in the beginning below 130 °C is due to the release of guest water molecules (cal: 10.17%). No obvious weight loss could be observed with temperature being in 123-200 °C. A next weight loss of 2.25% is ascribed to the removal of coordinated water molecules (cal: 2.03%) upon further heating to about 220 °C. A platform from 220 to 300 °C appears then, followed by the collapse of the desolvated framework. Likewise, the release of water molecules (cal: 7.27%) also gives rise to the first weight loss of compound 2 below 135 °C (exp: 6.85%). Further heating to 390 °C leads to the following continuous weight loss of 11.38% which could be attributed to the removal of protonated H4BAPEN (cal: 11.97%). Then the skeleton starts to collapse. For compound 3, the first weight loss is found to be 2.75% below 120 °C, owing to the removal of lattice water molecules (cal: 2.55%). Along-lived steady plateau occurs from 130 °C to 380 °C. Upon being further heated, the compound shows continuous multi-step weight loss which may be caused by the removal of protonated BAPEN and the collapse of framework. In short, compounds 1-3 can be stable up to ca. 300 °C, 390 °C and 380 °C, respectively. In addition, before property measurements, PXRD experiments were performed to substantiate the phase purity for the bulk samples of compounds 1-3. As presented in Figure S5-S7, the main peaks of the experimental patterns are in accordance with the simulated curves derived from crystallographic data, indicating the samples’ purity.

Coordination networks based on d10 transition metal ions are of great importance and has attracted numerous attention owing to their potential applications when serving as optical function materials.59,60 Therefore, the solid-state photoluminescence properties of compounds 1-3 were investigated at ambient temperature (Figure 5), and the observed spectra were compared with the spectral data of pure H4-HEDP solution. The free diphosphonate molecule exhibits a fluorescence emission band centered at 359 nm upon being excitated with UV light (λex = 320 nm).61,62 This emission band for diphosphonic acid corresponds to π–π* transitions. Compounds 1-3 display the similar emission behavior, and they can emit blue fluorescence emission bands with maxima at 430 nm for 1, 424 nm for 2, and 427 nm for 3, respectively (λex = 370 nm). Due to the difficulty to oxidize or reduce for electrochemically inert Zn(II) cation, thus ligand-to-metal charge transfer (LMCT) or metal-to-ligand charge transfer (MLCT) could hardly occur essentially. According to the previous studies, these emissions may be attributed to the intra-ligand emissions, as reported for other zincdiphosphonates.63 The emission bands of the present compounds have been shown to red shift compared to the pure ligand, as the crystal packing interactions and the coordination interactions in the solid samples could reduce the loss of energy by radiationless decay of the intraligand.64 Furthermore, the difference of luminescent intensities of these compounds might be attributed to the diverse coordination environment of metal centers as well as variation of solid-state crystal packing. Inspired by the plentiful hydrogen bonds between the protonated aliphatic amine and guest water molecules as well as phosphonate oxygen of Zn-HEDP host (Table S6) in the structure of 3, we further investigated its proton conduction behavior by Nyquist plots. Moreover, the adsorbed water molecules could also be employed to assist the formation of H-bonding chains with diphosphonate moleclules serving as proton-conducting pathways, which may further improve the property of proton conduction. Interestingly, the conductivity of samples 3 exhibits humidity dependence. When being in an ambient environment with room temperature and humidity, compound 3 shows a negligible conductivity, which probably due to the lack of efficient path for proton transmission. Once exposing the tablets of sample 3 in a closed chamber with

Figure 5. Photoluminescent spectra of solids 1-3.


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deionized water vapor for 10 hours, the conductivity could reach 6.28 × 10-5 S cm-1. As displayed in Figure 6, the impedance of 3 as a function of temperature was performed by modulating the temperature from 25 to 80 °C under 100% relative humidity. With the temperature being gradually elevated, the conductivity of sample 3 increases smoothly and finally reaches to a relatively high value of 1.82 × 10-4 S cm-1 at 80 °C. The temperature-dependent behavior of compound 3 suggests that the Zn-phosphonate solids could provide a promising platform to serve as a novel temperature sensor.

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CONCLUSIONS By virtue of a long flexible aliphatic amine, three zincdiphosphonates exhibiting different dimensions (from 1D to 3D) were constructed. Compound 1 displays a Zn-HEDP chain structure decorated by chelating BAPEN. Compound 2 possesses an anionic Zn-HEDP layer structure with the protanated BAPEN as charge balancer and space filling. Compound 3 features a 3D complicate Zn-HEDP network with protonated BAPEN acting as the template. The structure diversities were modulated by the distinct role of BAPEN in the assembly process, as the coordination role generates 1 and template role is responsible for 2 and 3. The photoluminescence as well as the proton conduction properties of the solids are studied in this work. The construction of compounds 1-3 not only develops the types and numbers of metal organophosphonates but emphasizes the critical role of long flexible aliphatic amine in the fabrication of novel corresponding products. Further researches on the exploration of other metal organophosphonate systems driven by long flexible aliphatic amine, following the goal for the acquisition of novel functional crystalline materials, are underway in our laboratory.

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ASSOCIATED CONTENT

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Supporting Information. Selected bond lengths and angles, selected hydrogen bond, PXRD and additional figures. CCDC number 1890697, 1890696, 1890695. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION (15)

Corresponding Author

*E-mail: [email protected]. Notes

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The authors declare no competing ﬁnancial interest.

ACKNOWLEDGMENTS

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We are thankful to the support from National Natural Science Foundation of China (21571111, 21601099 and 21601100).

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Switching the Zinc-Diphosphonates from 1D Chain to 2D Layer and 3D Framework by the Modulation of a Flexible Organic Amine Author list: Jie Pan, Yu-Juan Ma, Song-De Han,* Zhen-Zhen Xue, Guo-Ming Wang*

Synopsis: Three zinc-diphosphonates templated by protonated 1,2-bis(3-aminopropylamino)ethane were constructed with diverse structures.

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Switching the Zinc Diphosphonates from 1D Chain to 2D Layer and

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