Series of Coordination Polymers Based on Different Carboxylates and a Tri(4-imidazolylphenyl)amine...

Published: April 08, 2011

r 2011 American Chemical Society 2317 dx.doi.org/10.1021/cg200005q | Cryst. Growth Des. 2011, 11, 2317–2324

ARTICLE

pubs.acs.org/crystal

Series of Coordination Polymers Based on Different Carboxylatesand a Tri(4-imidazolylphenyl)amine Ligand: Entangled Structuresand PhotoluminescenceHua Wu,†,‡ Hai-Yan Liu,† Jin Yang,*,† Bo Liu,† Jian-Fang Ma,*,† Ying-Ying Liu,† and Yun-Yu Liu†

†Key Lab of Polyoxometalate Science, Department of Chemistry, Northeast Normal University, Changchun 130024,People’s Republic of China‡Heilongjiang Agricultural College of Vocational Technology, Jiamusi 154007, People’s Republic of China

bS Supporting Information

’ INTRODUCTION

The current interest in design and synthesis of coordinationpolymers not only stems from their intriguing aesthetic molec-ular topologies but also from their potential applications in thefields of ion exchange, gas storage, heterogeneous catalysis,luminescence, and nonlinear optics (NLO).1 Structural diversityin coordination networks can occur as a result of various pro-cesses, including supramolecular isomerism, interpenetration, orinterweaving. Among these, the entangled system has receivedremarkable attention for chemists because of its intricate frame-work topologies.2 So far, a variety of entangled arrays, such aspolycatenation, polythreading, polyrotaxane, and polyknotting,have been constructed and comprehensively reviewed by Ciani,Robson, and co-workers.2 Among the entangled system, thepolyrotaxane and polycatenane networks are particularly inter-esting. Their significant potential applications as molecular mate-rials for drug delivery vehicles, molecular machines, and sensordevices have been studied because of their special entangledmodes.3 Currently, the rational design and synthesis of novel en-tangled frameworks still strongly arouses the extensive interests ofchemists.

Usually, the construction of coordination polymers can be greatlyinfluenced by several factors, such as the nature of the metal ions,temperature, the organic ligands, solvent, and sometimes the

ratio of the metal ions to ligands.4 By the elaborate choice of theorganic spacers, it is possible to produce different types ofcoordination polymers with novel topological architectures.Among various organic ligands, N-donor ligands have attracteda great deal of attention from chemists due to their diversities incoordination modes and conformations. Up to now, a number offascinating architectures have been rationally designed throughusing the N-donor polyimidazole ligands.5 However, the tri(4-imidazolylphenyl)amine (Tipa), as a bridging ligand, is rarelyused in the construction of coordination networks (Scheme 1).The Tipa ligand possesses three Ph-imidazole (Ph = phenyl)arms with conformational and geometrical flexibility, where thearms can rotate freely and adjust themselves sterically around thecentral N moiety when coordinating to the metal atoms. In thiswork, seven coordination polymers, [Cd(Tipa)(L1)2] 3H2O (1),[Cd(Tipa)(L2)] 3H2O (2), [Cd(Tipa)(L2)] 3CH3OH 3H2O(3), Cd(Tipa)(L3)(H2O) (4), [Mn(Tipa)(L2)] 3H2O (5),[Ni2(Tipa)2(L4)(H2O)2]2 3Cl4 3 4H2O (6), and [Ni2(Tipa)2-(L5)(H2O)4] 3 (H4L5) 3 0.5H2O (7), have been synthesizedby using Tipa ligand and different carboxylate anions, where

Received: January 3, 2011Revised: April 7, 2011

ABSTRACT: Seven new coordination polymers, namely, [Cd(Tipa)(L1)2] 3H2O(1), [Cd(Tipa)(L2)] 3H2O (2), [Cd(Tipa)(L2)] 3CH3OH 3H2O (3), Cd(Tipa)-(L3)(H2O) (4), [Mn(Tipa)(L2)] 3H2O (5), [Ni2(Tipa)2(L4)(H2O)2]2 3Cl4 34H2O (6), and [Ni2(Tipa)2(L5)(H2O)4] 3 (H4L5) 3 0.5H2O (7), where HL1 =benzoic acid, H2L2 = 5-NH2-1,3-benzenedicarboxylic acid, H2L3 = 2-(4-carbox-ybenzylamino)benzoic acid, H2L4 = 1,4-benzenedicarboxylic acid, H4L5 = 1,2,4,5-benzenetetracarboxylic acid, and Tipa = tri(4-imidazolylphenyl)amine, have beensynthesized by varying the carboxylate anions and metal centers under hydro-thermal conditions. Compound 1 shows a one-dimensional (1D) chain. Com-pounds 2 and 5 are isostructural and display (3,5)-connected (42 3 6)(4

23 6

73 8)

topology. In the two compounds, the identical 2D networks entangle in highly rareparallel fashions to give fascinating 2D f 3D frameworks with polycatenation and polyrotaxane characters. Compound 3 displays a2-fold interpenetrating 3D framework with (3,5)-connected (63)(65 3 8

5) topology. The structure of 4 is a 4-fold interpenetrating 3D(10,3)-b framework. 6 is an uncommon 4-fold interpenetrating 3D framework with (3,4)-connected (4 3 8

2)(4 3 85) topology. 7 exhibits

an unprecedented 2Df 2D polyrotaxane layer with (3,4)-connected (42 3 6)(423 6

33 8) topology. The IR spectra, elemental analyses,

and luminescent properties for the compounds were also investigated.

2318 dx.doi.org/10.1021/cg200005q |Cryst. Growth Des. 2011, 11, 2317–2324

Crystal Growth & Design ARTICLE

HL1 = benzoic acid, H2L2 = 5-NH2-1,3-benzenedicarboxylicacid, H2L3 = 2-(4-carboxybenzylamino)benzoic acid, H2L4 =1,4-benzenedicarboxylic acid, and H4L5 = 1,2,4,5-benzenetetra-carboxylic acid (Scheme 1). The effects of anions on theircomplex structures are unraveled in detail. Further, the photo-luminescent properties of the coordination polymers have alsobeen studied.

’EXPERIMENTAL SECTION

Materials. The tris(4-iodophenyl)amine and tri(4-imidazolylphe-nyl)amine were synthesized by a procedure reported earlier.6 Otherreagents and solvents employed were commercially available and usedas received without further purification. All other reagents of analyticalgrade were purchased and used without further purification.Synthesis of 2-(4-Carboxybenzamido)benzoic Acid. 4-Car-

boxybenzaldehyde (1.50 g, 10 mmol) was dissolved in MeOH (20 mL),and 2-aminobenzoic acid (1.51 g, 10 mmol) in 20 mL of MeOH wasadded dropwise over 30min. The reactionmixture was stirred for 2 h, anda yellow powdery precipitate was obtained. The precipitate was sus-pended, and 0.8 g of NaBH4 was added during a period of 30min. Then, aclear reaction mixture was obtained and filtered. The clear filtrate wasdiluted with 30 mL of water and then acidified with cold dilute HClsolution until the precipitate was not producedwhen the pH value is about5. The white powdery precipitate was filtered, washed with water threetimes, and dried for 24 h under vacuum. Yield: 71%. Anal. Calcd forC15H13O4N (Mr = 271.27) (%): C, 66.41; H, 4.83; N, 5.16. Found: C,66.25; H, 4.96; N, 5.26. 1H NMR (500 MHz DMSO) δ/ppm: 4.56 (2H,singlet, N-CH2-CH), 6.55�7.91 (8H, multiplet, aromatic protons), 8.36(1H, singlet, C-NH-C). IR data (KBr, cm�1): 3360 (m), 3011 (m), 2854(m), 1679 (s), 1578 (s), 1516 (m), 1442 (m), 1255 (s), 1166 (w), 1126(w), 905 (w), 851 (w), 751 (m), 670 (w), 567 (w), 526 (m).Synthesis of [Cd(Tipa)(L1)2]H2O (1). Amixture of Tipa (0.044 g,

0.1mmol), Cd(CH3COO)2 3 2H2O (0.08 g, 0.3mmol),HL1 (0.073 g, 0.6mmol), NaOH (0.024 g, 0.6 mmol), and water (10 mL) was placed in aTeflon reactor (18mL) and heated at 140 �C for 3 days. After themixturehad been cooled to room temperature at a rate of 10 �C 3 h

�1, colorlesscrystals of 1 were obtained with a yield of 68%. Anal. Calcd forC41H33CdN7O5 (Mr = 816.16) (%): C, 60.34; H, 4.08; N, 12.01. Found:C, 60.45; H, 4.01; N, 11.91. IR data (KBr, cm�1): 3420 (m), 3121 (w),1598 (m), 1556 (m), 1513 (s), 1383 (m), 1260 (m), 1119 (w), 1060 (s),963 (w), 928 (w), 840 (m), 713 (m), 665 (w), 548 (m).Synthesis of [Cd(Tipa)(L2)] 3H2O (2). Tipa (0.044 g, 0.1 mmol),

Cd(CH3COO)2 3 2H2O (0.08 g, 0.3 mmol), H2L2 (0.054 g, 0.3 mmol),andwater (10mL) weremixed and then transferred and sealed in a 18mLTeflon-lined reactor. This reactor was heated at 140 �C for 3 days.Colorless crystals of 2 were collected in a 60% yield. Anal. Calcd forC35H27CdN8O5 (Mr = 752.05) (%): C, 55.88; H, 3.62; N, 14.90. Found:C, 55.97; H, 3.69; N, 14.81. IR data (KBr, cm�1): 3426 (m), 3124 (m),

1606 (m), 1560 (m), 1514 (s), 1367 (m), 1305 (m), 1281 (w), 1120 (w),1060 (w), 963 (m), 927 (w), 830 (m), 776 (m), 729 (m), 653 (m),543 (m).Synthesis of [Cd(Tipa)(L2)] 3CH3OH 3H2O (3). Tipa (0.044 g,

0.1 mmol), Cd(CH3COO)2 3 2H2O (0.08 g, 0.3 mmol), H2L2 (0.054 g,0.3 mmol), water (7 mL), and CH3OH (3 mL) were mixed and thentransferred and sealed in a 18 mL Teflon-lined reactor. The pH value wasadjusted to 9 with diluted Et3N solution. This reactor was heated at140 �C for 3 days. Colorless crystals of 3 were collected in a 56% yield.Anal. Calcd for C36H32CdN8O6 (Mr = 785.10) (%): C, 55.07; H, 4.11; N,14.27. Found: C, 55.15; H, 4.03; N, 14.16. IR data (KBr, cm�1): 3422(m), 3119 (m), 1557 (w), 1515 (s), 1305 (m), 1284 (m), 1120 (m), 1059(s), 962 (m), 828 (m), 734 (w), 537 (w).Synthesis of Cd(Tipa)(L3)(H2O) (4). The preparation of 4 was

similar to that of 1 except that H2L3 was used instead of HL1. Colorlesscrystals of 4were collected in 45% yield. Anal. Calcd for C42H33CdN8O5

(Mr = 842.17) (%): C, 59.90; H, 3.95; N, 13.31. Found: C, 59.79; H,3.88; N, 13.24. IR data (KBr, cm�1): 3308 (m), 3110 (m), 1609 (m),1515 (s), 1388 (m), 1276 (m), 1126 (w), 1062 (m), 962 (w), 961(w),827 (m), 654 (m), 543 (w), 417 (w).Synthesis of [Mn(Tipa)(L2)] 3H2O (5). The preparation of 5 was

similar to that of 1 except that Mn(CH3COO)2 3 4H2O and H2L2 wereused instead of Cd(CH3COO)2 3 2H2O and HL1, respectively. Thereactor was heated at 170 �C for 3 days. Colorless crystals of 5 werecollected in 72% yield. Colorless crystals of 5were collected in a 68%yield.Anal. Calcd for C35H28MnN8O5 (Mr = 695.59) (%): C, 60.43; H, 4.06; N,16.11. Found: C, 60.32; H, 4.15; N, 16.02. IR data (KBr, cm�1):3451 (m), 3125 (w), 1608 (m), 1568 (m), 1514 (s), 1372 (m),1310 (m), 1274 (m), 1116 (w), 1508 (m), 962 (w), 924 (w), 838 (m),730 (m), 652 (m), 547 (m).Synthesis of [Ni2(Tipa)2(L4)(H2O)2]2 3Cl4 3 4H2O (6). The pre-

paration of 6 was similar to that of 5 except that NiCl2 3 6H2O and H2L4were used instead of Mn(CH3COO)2 3 4H2O and H2L2, respectively.Green crystals of 6 were collected in 57% yield. Anal. Calcd forC124H108Cl4N28Ni4O16 (Mr = 2623.02) (%): C, 56.78; H, 4.15; N,14.95. Found: C, 56.66; H, 4.24; N, 14.86. IR data (KBr, cm�1):3405 (m), 3131 (m), 1601 (s), 1516 (s), 1370 (m), 1305 (w), 1062(s), 964 (s), 935 (m), 822 (m), 727 (m), 655 (m), 545 (m).Synthesis of [Ni2(Tipa)2(L5)(H2O)4] 3 (H4L5) 3 0.5H2O (7).

The preparation of 7 was similar to that of 6 except that H4L5 was usedinstead of H2L4. Green crystals of 7 were collected in 55% yield. Anal.Calcd for C74H55N14Ni2O21 (Mr = 1593.74) (%): C, 55.77; H, 3.48; N,12.30. Found: C, 55.86; H, 3.59; N, 12.42. IR data (KBr, cm�1):3425 (m), 3149 (m), 3127 (m), 1715 (m), 1577 (m), 1519 (s), 1386(m), 1342 (m), 1253 (m), 1066 (m), 961 (w), 831 (w), 763 (w), 748(m), 655 (w), 536 (w).Physical Measurements. Elemental analyses were carried out with

a Carlo Erba 1106 elemental analyzer, and the FT-IR spectra wererecorded from KBr pellets in the range 4000�400 cm�1 on a MattsonAlpha-Centauri spectrometer. The photoluminescent properties of theligands and compounds were measured on a Perkin-Elmer FLS-920spectrometer.X-ray Crystallography. Experimental details of the X-ray analyses

are provided in Table 1. Diffraction intensities for 1�3, 5, and 7 wererecorded on a Oxford Diffraction Gemini R Ultra diffractometer withgraphite-monochromated Mo KR radiation (λ = 0.71073 Å) at 293 K.Diffraction data for 4 and 6 was collected on a Oxford Diffraction GeminiR Ultra diffractometer with graphite-monochromated Cu KR radiation(λ = 1.54184 Å) at 293 K. The structures were solved with the directmethod of SHELXS-977 and refined with full-matrix least-squares tech-niques using the SHELXL-97 program8 within WINGX.9 The hydrogenatoms attached to carbons were generated geometrically. The hydrogenatom positions were fixed geometrically at calculated distances andallowed to ride on the parent atoms. The disordered C atoms of

Scheme 1. Structures of the Carboxylic Acids and TipaLigand Used in This Work



compound 2 (C7 and C8), compound 5 (C35 and C36), and compound7 (C18 and C19) were refined using C atoms split over two sites. Thedisordered chlorine ions of 6 (Cl2 and Cl4) were refined using a Cl atomsplit over quarter sites. The H atoms of the disordered C atoms were notincluded in themodel.Non-hydrogen atomswere refinedwith anisotropictemperature parameters.

The detailed crystallographic data and structure refinement param-eters for these compounds are summarized in Table 1. Selected bonddistances and angles are listed in Table S1 (Supporting Information).

’RESULTS AND DISCUSSION

Structure of [Cd(Tipa)(L1)2] 3H2O (1).Compound 1 containsone crystallographically unique CdII atom, two unique L1 anions,

and one Tipa ligand (Figure 1a). The CdII atom is six-coordi-nated by three nitrogen atoms from three different Tipa ligands[Cd1�N3 = 2.307(3), Cd1�N6#1 = 2.306(3), and Cd1�N7#2 =2.359(3) Å], and three oxygen atoms from two different L1anions [Cd1�O1 = 2.704(5), Cd1�O2 = 2.260(2), andCd1�O3 = 2.253(2) Å] in a distorted octahedral geometry.The CdII�O and CdII�N distances are similar to the pre-viously reported ones.10 The Tipa ligands in trimonodentatemodes bridge adjacent CdII atoms to give an infinite 1D chain(Figure 1b). Two types of L1 anions are attached on both sidesof the chain.Structure of [Cd(Tipa)(L2)] 3 2H2O (2). As shown in

Figure 2a, the structure of 2 contains one unique CdII atom,one unique L2 anion, one unique Tipa ligand, and oneuncoordinated water molecule. The CdII atom is six-coordi-nated by three nitrogen atoms from three Tipa molecules[Cd1�N4 = 2.345(9), Cd1�N7#1 = 2.279(8), and Cd1�N3#2 =2.293(8) Å], and three carboxylate oxygen atoms from two L2anions [Cd1�O2 = 2.277(7), Cd1�O3#3 = 2.529(7), andCd1�O4#3 = 2.340(6) Å] in a distorted octahedral coordinationgeometry. Adjacent CdII atoms are linked by L2 anions to generateCd-carboxylate chains. The chains are further extended by Tipaligands to give a novel puckered double sheet with a 1D channel(Figure 2b). The puckered sheet has two kinds of large rectangleand rhombic windows of Cd2(Tipa)2 and Cd4(Tipa)2(L2)2,respectively. The Cd2(Tipa)2 window (Figure 2c, green one) isbuilt by two CdII atoms and two Tipa ligands with dimension of9.88 � 9.92 Å2, while the rectangle Cd4(Tipa)2(L2)2 window(Figure 2c, blue one) is built by four CdII atoms, two Tipa ligands,and two L2 ligands with dimension of 10.20 � 18.46 Å2. If eachTipa ligand is considered as a three-connected node, and theCdII atom is considered as a five-connected node, the frameworkcan be classified as a (3,5)-connected (42 3 6)(4

23 6

73 8) topology

(Figure 2c).Notably, adjacent windows [Cd2(Tipa)2] of each layer are

passed by L2 ligands of above and below layers, and the rest maybe deduced by analogy. As highlighted in Figure 2d, adjacentwindows [Cd2(Tipa)2] of middle yellow are passed by L2 ligandsof blue (above) and green (below) layers. If the Cd2(Tipa)2windows are considered as loops, and L2 ligands are consideredas rods, compound 2 is a fascinating 2D f 3D entangled

Figure 1. (a) Coordination environment (at 30% probability level)of the CdII atom in 1. The uncoordinated water molecule and H atomsare omitted for clarity. (b) An infinite 1D chain structure of compound 1.Symmetry code: (#1) �x þ 3, �y, �z þ 1; (#2) x � 1, y � 1, z þ 1.

Table 1. Crystal Data and Structure Refinements for Compounds 1�7

1 2 3 4 5 6 7

empirical formula C41H33CdN7O5 C35H27CdN8O5 C36H32CdN8O6 C42H33CdN8O5 C35H28MnN8O5 C124H108Cl4N28Ni4O16 C74H55N14Ni2O21

fw 816.16 752.05 785.10 842.16 695.59 2623.02 1593.74

crystal system triclinic monoclinic monoclinic monoclinic monoclinic tetragonal triclinic

space group P1 P21/c P21/n P2/n P21/c P4/n P1

a (Å) 11.8990(6) 10.1973(10) 12.0550(3) 14.9127(2) 10.1120(3) 22.4660(1) 11.0480(3)

b (Å) 12.7120(7) 18.464(2) 9.9570(2) 9.2663(3) 18.3860(7) 22.4660(1) 11.5630(4)

c (Å) 14.0190(7) 18.495(2) 29.0930(6) 27.2481(4) 18.4730(6) 13.3870(1) 16.1690(7)

R (deg) 67.000(5) 90 90 90 90 90 76.974(4)

β (deg) 72.669(4) 104.565(10) 98.020(2) 98.2530(10) 104.583(4) 90 89.733(3)

γ (deg) 79.114(4) 90 90 90 90 90 63.126(4)

V (Å3) 1856.98(17) 3370.5(6) 3457.93(13) 3726.30(14) 3323.84(19) 6756.70(7) 1783.80(11)

Z 1 4 4 4 4 2 1

Rint 0.0414 0.1382 0.0311 0.0872 0.0505 0.0320 0.0213

R1 [I > 2σ(I)] 0.0463 0.0701 0.0329 0.0654 0.0564 0.0591 0.0520

wR2 (all data) 0.0802 0.1847 0.0749 0.1874 0.1448 0.1963 0.1565



framework with both polyrotaxane and polycatenane characters(Figure 2d).According to previous documents, only a few examples of

dimensionality increasing from 2D layers to an overall 3D entangle-ment have been observed for systems polycatenating in a parallelfashion.11However,most of the studies have been focused on thehcband sql networks. The 2D f 3D entangled frameworks with bothpolyrotaxane and polycatenation characters are exceedingly rare.12

Structure of [Cd(Tipa)(L2)] 3CH3OH 3H2O (3). The structureof 3 contains one unique CdII atom, one unique L2 anion, oneunique Tipa ligand, one water molecule, and one methanolmolecule (Figure 3a). CdII atom is six-coordinated by threenitrogen atoms from three different Tipa ligands [Cd1�N5#1 =2.276(2), Cd1�N7#2 = 2.313(2), and Cd1�N3 = 2.373(2) Å],and three oxygen atoms from two L2 anions [Cd1�O1#3 =2.352(2), Cd1�O2#3 = 2.636(3), and Cd1�O4 = 2.268(2) Å]in a distorted octahedral geometry. The CdII atoms are bridged byL2 anions to form an infinite 1D chain. The chains are furtherconnected by Tipa ligands and L2 anions to give a 3D framework(Figure 3b). If the L2 anion is considered as a single linker, theTipa ligand is considered as a three-connected node, and the CdII

atom can be viewed as a five-connected node, the structure can beclassified as a (3,5)-connected (63)(65 3 8

5) topology (Figure 3c).

An interesting feature of this 3D framework is the presence of1D honeycomb hexagonal channels along the b axis withdimension about 12.06 � 14.98 Å. The void space in the singleframework is so large that two identical 3D frameworks inter-penetrate each other in a 2-fold mode (Figure 3d).Structure of Cd(Tipa)(L3)(H2O) (4). In the asymmetric unit of

compound 4, there are one unique CdII atom, one unique Tipaligand, one L3 anion, and one water molecule. As shown inFigure 4a, the CdII atom is six-coordinated by three nitrogenatoms from three different Tipa ligands [Cd1�N1 = 2.302(7),Cd1�N5#1 = 2.248(5), and Cd1�N7#2 = 2.291(6) Å], and threeoxygen atoms from one L3 anion and one water molecule[Cd1�O1 = 2.495(5), Cd1�O2 = 2.316(4), and Cd1�O1W =2.308(6) Å] in a slightly distorted octahedral coordinationgeometry. Each Tipa links three CdII atoms to generate a 3Dframework with large voids (Figure 4c). In the independent 3Darchitecture, there is a penta-metal macrocyclic unit [Cd5-(Tipa)5(L3)5], in which five CdII atoms are noncoplanar(Figure 4b). If the Tipa ligand is considered as a three-connectednode, the CdII atom also can be viewed as a three-connectednode, and the structure can be classified as an unusual (10,3)-b(or ThSi2) net (Figure 4d).

Figure 3. (a) Coordination environment (at 30% probability level) ofthe CdII atom in 3. All H atoms and solvent molecules are omitted forclarity. (b) Single 3D framework of 3. (c) Schematic illustration of thetopology of 3. (d) Schematic representation of the 2-fold interpenetrat-ing framework. Symmetry codes: (#1) xþ 1, yþ 1, z; (#2) xþ 1/2,�y�1/2, z þ 1/2; (#3) x, y � 1, z.

Figure 2. (a) Coordination environment (at the 30% probability level)of the CdII atom in 2. The uncoordinated water molecule and H atomsare omitted for clarity. (b) 2D puckered layer with a large channel.(c) Schematic representation of the topology of the 2D layer with twokinds of windows. (d) Schematic representation of the windows of themiddle layer (yellow) passed by rods of the above (blue) and below(green) layers. (e) Schematic representation of the 2Df 3D entangledframework. Symmetry codes: (#1)�xþ 1, y� 1/2,�z� 1/2; (#2) x, y� 1, z;(#3) x þ 1, y, z.



To increase the stability of the packing structure with largecavities, these voids are partially filled by three other symmetry-equivalent frameworks, leading to an unusual 4-fold inter-penetrating structure (Figure 4e). According to the literature,although the interpenetrating (10,3)-b frameworks havebeen reported, the 4-fold interpenetrating example is rarelyobserved.13,3b

Structural Description of [Mn(Tipa)(L2)] 3H2O (5). Com-pound 5 is isostructural with 2 except that MnII ions were usedinstead of CdII ions (Figure S1, Supporting Information).Structure of [Ni2(Tipa)2(L4)(H2O)2]2 3Cl4 3 4H2O (6). In the

asymmetric unit of compound 6, theNiII atom is six-coordinated bythree nitrogen atoms from different Tipa ligands [Ni1�N8 =2.109(3), Ni1�N5#1 = 2.040(3), and Ni1�N3#2 = 2.113(3) Å],and three oxygen atoms fromone L4 anion andonewatermolecule[Ni1�O1 = 2.172(2), Ni1�O2 = 2.071(2), and Ni1�O1W =2.089(3) Å] in a distorted octahedral coordination geometry(Figure 5a). The adjacent NiII atoms are bridged by L4 anionsand Tipa ligands to generate a 3D framework with a large channel

ca. 15� 19 Å2 (Figure 5b). If the L4 anion is considered as a singlelinker, the Tipa ligand is considered as a three-connected node, andthe NiII atom can be viewed as a four-connected node, and thestructure can be classified as a (3,4)-connected framework with aSchl€afli symbol of (4 3 8

2)(4 3 85) (Figure 5c). Interestingly, four

independent equivalent frameworks interlaced each other in anunusual [2 þ 2] mode, resulting in a 4-fold interpenetrating 3Dframework (Figure 5d and e).Structure of [Ni2(Tipa)2(L5)(H2O)4] 3 (H4L5) 3 0.5H2O (7). In

the asymmetric unit of compound 7, there are one uniqueNiII atom, one unique Tipa ligand, two half L5 anions, andthree water molecules (Figure 6a). The NiII atom is six-coordi-nated by three nitrogen atoms from different Tipa ligands

Figure 4. (a) Coordination environment (at the 30% probability level)of the CdII atom in 4. All H atoms are omitted for clarity. (b) Cd5-(Tipa)5(L5)5 unit. (c) View of the single (10,3)-b network. (d) Schematicrepresentation of the topology. (e) View of the 4-fold interpenetrationof 4. Symmetry codes: (#1) x� 1/2,�yþ 1, z� 1/2; (#2) x� 1, y� 1, z;(#3) x þ 1/2, �y þ 1, z þ 1/2.

Figure 5. (a) Coordination environment (at 30% probability level) ofthe NiII atom in 6. All H atoms, uncoordinated water molecules, andchloride ions are omitted for clarity. (b) 3D framework of 6. (c) View ofthe topology of 6. (d) View of two sets interpenetration along the a axis.(e) Schematic view of the 4-fold interpenetrating framework. Symmetrycodes: (#1) x þ 1/2, y � 1/2, �z; (#2) �x þ 1/2, �y þ 1/2, z � 1.



[Ni1�N3 = 2.068(3), Ni1�N5#2 = 2.101(2), and Ni1�N7#1 =2.089(2) Å], and three oxygen atoms from one L5 anion and twowater molecules [Ni1�O5 = 2.075(2), Ni1�O1W = 2.146(2),and Ni1�O2W = 2.099(2) Å] in a slightly distorted octahedralcoordination geometry. For convenience, the L5 anions contain-ing O5 and O1 are designated L50 and L500, respectively. Theprotonated L500 ligand is free. The adjacent NiII atoms arebridged by Tipa ligands and L50 anions to form a 2D layer withrhombic Ni2(Tipa)2 windows (dimensions of 9.58 � 9.55 Å2)(Figure S2). If the L50 anion is considered as a single linker, theTipa ligand is considered as a three-connected node, and the NiII

cation can be viewed as a four-connected node, the structure can

be classified as a (3,4)-connected network with a Schl€afli symbolof (42 3 6)(4

23 6

33 8).

The most fascinating structural feature of 7 is that such layersinterlace each other in a parallel fashion to give a 2D interpene-trating network (Figure 6b). One Ni2(Tipa)2 window of eachlayer is passed by the L50 ligand of another layer, and every otherNi2(Tipa)2 window is threaded by a L50 ligand in the sameway. Ifthe Ni2(Tipa)2 windows are considered as loops and L50 ligandsare considered as rods, the compound 7 belongs to a 2D f 2Dpolyrotaxane network.More interestingly, the neighboring 2D f 2D polyrotaxane

sheets are staggered parallel with each other, where the proto-nated L500 ligands are sandwiched between the layers (Figure 6c).Obviously, this packing mode decreases the molecular repulsionand stabilizes the whole structure of 7.Effect of Organic Acid on the Structure of the Compound.

The organic anions play a crucial role in determining themolecular structures of the resultant complexes. In this study,the structural features of the carboxylate anions, such as thenumbers of carboxylate groups and the length and flexibility ofthe spacers are the underlying reason for the structural differ-ences of the complexes. The structural differences of 1 relative to2 and 4, and of 6 relative to 7 are mainly determined by thenumbers of the carboxylate groups. Compared with L2 and L3ligands, the L1 ligand contains one carboxylate group and acts asa terminal ligand. In compound 1, the Tipa ligands bridgeadjacent CdII atoms to generate a 1D chain structure with theL1 ligand attached to the chain rather than the intricate 3Dstructures of 2 and 4. The L4 ligand has two carboxylate groups,while the L5 ligand has four carboxylate groups. Although twocarboxylate groups of the L5 ligand do not coordinate to NiII

atoms, the structures of 6 and 7 are very different. Compound 6 isan unusual 4-fold interpenetrating framework in a [2þ 2] mode,while 7 is an unprecedented 2D f 2D polyrotaxane network.L2 is a rigid dicarboxylate ligand, while L3 is a long flexible

dicarboxylate ligand. The structural difference between 2 and4 may be attributed to the difference of the spacer length andflexibility of the two ligands. As expected, compound 2 exhibits a2D f 3D polyrotaxane network, while 4 shows a 4-fold inter-penetrating (103)-b framework.It should be pointed out that although the starting materials

used for syntheses of 2 and 3 are the same, their complexstructures are entirely different. Compared with 2, there is an

Figure 6. (a) Coordination environment (at 30% probability level) ofthe NiII atom in 7. All H atoms, uncoordinated water molecules, andchloride ions are omitted for clarity. (b) View of the 2D f 2Dpolyrotaxane framework of 7. (c) View of the packing diagram offramework 7. Symmetry codes: (#1) �x þ 1, �y þ 1, �z þ 2;(#2) �x, �y þ 2, �z þ 1.

Figure 7. Excitation (black curves) and emission (blue curves) spectra of free ligands and 1�3 at room temperature.



additional methanol molecule in 3. The presence of themethanolmolecule in 3may be themain reason for the structural differencebetween 2 and 3.Luminescent Properties. The photoluminescent spectra of

1�3 and free ligands (HL1 and Tipa) were examined in the solidstate at room temperature. The emission and excitation peaks ofthe compounds are shown in Figure 7 and Table 2. Emissionbands were observed at 320 (λex = 210 nm) and 420 nm (λex =365 nm) for HL1 and Tipa, respectively. H2L2 does not displayany emission. The emission bands for the free ligands are probablyattributable to theπ*f norπ*fπ transitions.14 The luminescentdecay profiles can be fitted with a double-exponential decayfunction with τ1 =1.998 ns (81.57%) and τ2 = 6.945 ns (18.43%)for Tipa, and τ1 = 1.594 ns (56.36%) and τ2 = 3.83 ns (43.64%)for HL1.Compounds 1�3 display fluorescence at room temperature.

For 1, the emission peak was observed at 455 nm under anexcitation wavelength at 380 nm. For 2, the emission peak with amaximum at 423 nm (λex = 375 nm) was observed. Compound3 exhibits photoluminescence with an emission maximum at430 nm upon excitation at 365 nm. These emissions have similarprofiles observed in the free Tipa ligand. The luminescent decaycurves can be fitted with a double-exponential decay functionwith τ1 =2.106 ns (71.55%) and τ2 = 6.787 ns (28.45%) for 1,τ1 = 1.904 ns (80.72%) and τ2 = 6.771 ns (19.28%) for 2, andτ1 =1.985 ns (84.62%) and τ2 = 6.652 ns (15.38%) for 3. Theshort luminescent lifetimes of 1�3 are very close to the ones ofthe free Tipa ligand. On the basis of the luminescent lifetimes, theemissions of compounds 1�3 are probably attributed to theligand-centered π*�π transitions of the Tipa ligands.15

’CONCLUSION

In conclusion, a series of coordination polymers with a triden-tate ligand and different carboxylate anions have been preparedand characterized through single-crystal X-ray diffraction analyses.These compounds display architectures from 1D chain to 3Dentangled frameworks. The results indicate the importance of thedifferent carboxylate anions in the construction of the finalframeworks. Also, the different entangled modes observed hereprovide new perspectives in the topology of interpenetration.

’ASSOCIATED CONTENT

bS Supporting Information. X-ray crystallographic files(CIF); selected bond lengths and angles; figures for the struc-tures of 5 and 7. This material is available free of charge via theInternet at http://pubs.acs.org.

’AUTHOR INFORMATION

Corresponding Author*E-mail: J.Y., [email protected]; J.-F.M., [email protected].

’ACKNOWLEDGMENT

We thank the Program for Changjiang Scholars and InnovativeResearch Teams in Chinese Universities, the National NaturalScience Foundation of China (Grant No. 21071028, 21001023),the Science Foundation of Jilin Province (20090137, 20100109),the Fundamental Research Funds for the Central Universities,the Specialized Research Fund for the Doctoral Program ofHigher Education, the China Postdoctoral Science Foundation(20080431050 and 200801352), the Training Fund of NENU’sScientific Innovation Project, and the Analysis and Testing Foun-dation of Northeast Normal University for support.

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