1D Tube, 2D Layer, and 3D Framework Derived from a New Series of

Three novel coordination polymers, [Cu2(adip)(H2O)4]n·nH2O (1), ... Qian Chu, Zhi Su, Jian Fan, Taka-aki Okamura, Gao-Chao Lv, Guang-Xiang Liu, Wei-Yi...
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1D Tube, 2D Layer, and 3D Framework Derived from a New Series of Metal(II)-5-Aminodiacetic Isophthalate Coordination Polymers Yanqing Xu, Daqiang Yuan, Benlai Wu, Lei Han, Mingyan Wu, Feilong Jiang,* and Maochun Hong

CRYSTAL GROWTH & DESIGN 2006 VOL. 6, NO. 5 1168-1174

State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China ReceiVed December 26, 2005; ReVised Manuscript ReceiVed March 12, 2006

ABSTRACT: Three novel coordination polymers, [Cu2(adip)(H2O)4]n‚nH2O (1), [Co3(Hadip)2(H2O)6]n‚2nH2O (2), and [Zn7(adip)4(H2O)10K2(H2O)2]n‚4nH2O (3), were solvothermally synthesized by adopting a new type of multicarboxylate ligand, H4adip (H4adip ) 5-aminodiacetic isophthalic acid). Compound 1 features a 1D tube-like structure, compound 2 shows novel 2D (3,4)-connected nets, and compound 3 possesses an interesting 3D architecture, all of which possess channels hosting guest water molecules. A particular interest of the adip4- ligand is its propensity to bind metal ions forming various metallocycles, which could be viewed as the basic building blocks in the construction of supramolecular frameworks. Thermogravimetric analyses (TGA) were performed on compounds 1, 2, and 3. Variable-temperature magnetic susceptibility of 2 was investigated. An intense blue luminescence with an emission band peaking at 454 nm observed for 3 may result from ligand-to-metal charge transfer (LMCT). Introduction Crystal engineering has grown into a subject that attracts intense attention because controlling the molecular organization in the solid state can lead to new materials with novel structures and promising properties.1 But in many cases it is quite difficult to design and synthesize a desired metal-organic framework in a truly deliberate manner, due to the influence of many factors upon the final product structures, such as the coordination geometry of the central metal ion and the shape, functionality, flexibility, and symmetry of the ligand.2 Presently, a rational synthetic strategy widely used in this area is linking metal ions with polydentate ligands that function as connectors.3 Polydentate ligand compounds, which provide metal-binding sites, can act as either bridging or chelating ligands, yielding desired networks in metal-organic coordination polymers.4 As an important family of multidentate O-donor ligands, organic aromatic tetracarboxylate ligands, such as 1,2,4,5-benzenetetracarboxylate (1,2,4,5-btec), have been extensively employed in the preparation of such metal-organic compounds.5 Furthermore, the new tetracarboxylate ligands, 3,3′,4,4′-benzophenonetetracarboxylate1a and 1,4,5,8-naphthalenetetracarboxylate,6 were also reported recently. However, the carboxyl groups on the above-mentioned aromatic rings are all rigid, which to some degree limit the outspread in 3D direction of metalorganic frameworks and hinder the assembly of certain crystalline products.6a Very recently, we designed and synthesized a new bridgingchelating multicarboxylate ligand compound, 5-aminodiacetic isophthalic acid (H4adip), based on 5-aminoisophthalic acid. Compared with the 1,2,4,5-btec ligand compound, H4adip not only has two rigid carboxyl groups affixed to the aromatic ring but also extends two flexible acetic arms from its aminodiacetic group to further participate in the coordination process. Thus, adip4- possesses four carboxyl groups and one amino nitrogen atom, adding up to nine potential coordination sites, and would act as a versatile connector in the construction of novel metalorganic hybrid compounds. Herein, we report three novel coordination polymers assembled from this new ligand and * To whom correspondence should be addressed. E-mail: fjiang@ fjirsm.ac.cn. Tel: 86-591-83774605. Fax: +86-591-83794946.

divalent transition metal ions: [Cu2(adip)(H2O)4]n‚nH2O (1), [Co3(Hadip)2(H2O)6]n‚2nH2O (2), and [Zn7(adip)4(H2O)10K2(H2O)2]n‚4nH2O (3). Our results show that the nitrogen atom of the aminodiacetic group in adip4- acts as an endodentate site, binding metal(II) ions in conjunction with the other carboxyl groups, which forms diverse basic building blocks in the coordination polymers. Experimental Section All commercially available chemicals are of reagent grade and were used as received. Elemental analyses were determined on an Elemental Vario ELIII elemental analyzer. 1H NMR spectra were recorded on a Varian Unity-500 spectrometer (DMSO-d6 as solvent), operating at 499.802 MHz. IR spectra were measured as KBr pellets on a Nicolet Magna 750 FT IR spectrometer in the range of 200-4000 cm-1. Thermogravimetric analyses were carried out with a NETZSCH STA 449C unit from 30 to 900 °C at a heating rate of 10 °C‚min-1 under nitrogen. Variable-temperature (2.0-300.0 K) magnetic susceptibility measurements were carried out on a Quantum Design PPMS60000 in a magnetic field of 10 kOe, and the diamagnetic corrections were evaluated by using Pascal’s constants.7 Fluorescent analyses were performed on an Edinburgh Instruments FL920 analyzer. Synthesis of 5-Aminodiacetic Isophthalic Acid (H4adip). The ligand compound, H4adip, was prepared following the comparative method as described for H3CPIDA.4a A solution of KOH (22.4 g, 0.40 mol) in water (50 mL) was added dropwise to chloroacetic acid (18.9 g, 0.20 mol) in water (50 mL) with stirring. 5-Aminoisophthalic acid (9.05 g, 0.05 mol) was slowly added to the reaction mixture, and then the mixture was refluxed at about 80 °C for 30 h. The reaction solution was cooled to room temperature and acidified with HCl (6 mol/L) until the desired pale yellow acidic material precipitated (pH ≈ 2.5), which was filtered, washed with water, and dried in air. Yield 9.5 g, 71.7%. IR (KBr pellet, cm-1): 3434 (b), 3147 (w), 2926 (m), 2844 (w), 1698(s), 1665 (w), 1600 (s), 1470 (s), 1443 (m), 1384 (vs), 1443 (m), 1338 (w), 1288 (m), 1214 (m), 1198 (m), 996 (m), 903 (m). 1H NMR (DMSO-d6): δ 7.799 (s, 1 H, Ph-H), 7.254 (s, 2 H, Ph-H), 4.048 (s, 4 H, -CH2-). Anal. Calcd for C12H11NO8: C 48.49, N 4.71, H 3.73%. Found: C 48.42, N 4.66, H 3.82%. Synthesis of [Cu2(adip)(H2O)4]n‚nH2O (1). Preparation was processed by reaction of Cu(OAc)2‚2H2O (0.040 g, 0.20 mmol), H4adip (0.045 g, 0.15 mmol), and 4,4′-bipyridine (4,4′-bpy, 0.032 g, 0.20 mmol) in CH3OH/H2O solution (1:1, 8 mL) under solvothermal conditions. The above mixture was stirred fully first and sealed in a 23-mL Teflonlined stainless steel container, heated at 90 °C for 3 days, and then cooled to room temperature. After filtration, the green prismatic crystals

10.1021/cg0506774 CCC: $33.50 © 2006 American Chemical Society Published on Web 04/08/2006

New Series of Metal(II)-H4adip Coordination Polymers

Crystal Growth & Design, Vol. 6, No. 5, 2006 1169

Table 1. Crystallographic Data for the Compounds 1-3

empirical formula temp (K) cryst color cryst size (mm3) Mr crystal system space group a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3) Z density (Mg/m3) abs coeff (mm-1) F(000) reflns collected independent reflns params S on F2 R1, wR2 [I > 2σ(I)] R1, wR2 (all data)

1

2

3

C12H17Cu2NO13 173(2) green 0.20 × 0.10 × 0.08 510.35 triclinic P1h 7.1637(5) 10.014 12.3475(7) 70.188(10) 88.077(15) 80.202(13) 820.90(7) 2 2.065 2.668 516 6427 3713 [R(int) ) 0.0301] 253 1.056 0.0406, 0.1043 0.0568, 0.1140

C24H32Co3N2O24 173(2) purple 0.20 × 0.10 × 0.05 909.31 triclinic P1h 7.34710(10) 8.6909(2) 13.8638(7) 85.914(15) 75.119(12) 65.103(11) 775.36(4) 1 1.947 1.695 463 6054 3511 [R(int) ) 0.0261] 241 1.039 0.0443, 0.1012 0.0588, 0.1118

C48H60K2N4O48Zn7 173(2) colorless 0.10 × 0.10 × 0.05 1996.79 triclinic P h1 7.7389(9) 10.6022(13) 20.719(2) 96.054(6) 90.734(3) 103.936(6) 1639.5(3) 1 2.022 2.766 1008 12903 7396 [R(int) ) 0.0562] 493 1.073 0.0700, 0.1258 0.1185, 0.1507

of compound 1 were isolated by slow evaporation of solvents from the filtrate for several days. Yield 0.028 g, 54.9% (based on Cu). Without the addition of 4,4′-bpy in above procedure, only powder product was formed. We surmise that the 4,4′-bpy here may adjust the pH during the reaction process to help the formation of crystalline 1. IR (KBr pellet, cm-1): 3445 (b), 3003 (w), 2957 (w), 2926 (w), 1663 (w), 1615 (s), 1578 (vs), 1548 (s), 1457 (m), 1410 (s), 1382 (vs), 1293 (m), 975 (w), 898 (w). Anal. Calcd for C12H17Cu2NO13: C 28.24, H 3.36, N 2.74%. Found: C 28.14, H 3.56, N 2.62%. Synthesis of [Co3(Hadip)2(H2O)6]n‚2nH2O (2). A mixture of Co(NO3)2‚6H2O (0.073 g, 0.25 mmol) and H4adip (0.074 g, 0.25 mmol) was dissolved in CH3OH/H2O solution (1:1, 8 mL). With stirring, pyridine was slowly added to adjust its pH value to 5.0. The mixture was sealed in a 23-mL Teflon-lined stainless steel container and heated at 90 °C for 3 days. Purple crystals of 2 were obtained after the reactant was cooled to room temperature. Yield 0.045 g, 59.4% (based on Co). IR (KBr pellet, cm-1): 3411 (b), 3008 (w), 2921 (w), 1708 (s), 1605 (vs), 1447 (m), 1417 (vs), 1372 (m), 1282 (m), 1234 (s), 1198 (m), 944 (w). Anal. Calcd for C24H32Co3N2O24: H 3.55, C 31.70, N 3.08%. Found: C 31.65, H 3.66, N 2.98%. Synthesis of [Zn7(adip)4(H2O)10K2(H2O)2]n‚4nH2O (3). Zn(OAc)2 (0.11 g, 0.5 mmol), H4adip (0.148 g, 0.5 mmol), and KOH (0.5 mmol) were added to CH3CN/H2O solution (1:1, 10 mL) in a Teflon-lined stainless steel reactor. The mixture was heated at 90 °C for 3 days and then cooled to room temperature; colorless needlelike crystals of 3 were formed. Yield 0.076 g, 54% (based on Zn). Anal. Calcd for C48H60K2N4O48Zn7: C 32.18, H 3.15, N 3.13%. Found: C 32.16, H 3.30, N 3.12%. IR (KBr pellet, cm-1): 3440 (b), 3226 (s), 3118 (s), 2926 (w), 2849 (w), 1613 (vs), 1578 (vs), 1480 (m), 1464 (vs), 1113 (vs), 998 (m), 758 (s), 720 (m), 430 (m). X-ray Structure Analyses. X-ray intensity data of compounds 1-3 were collected on a Siemens Smart CCD diffractometer equipped with graphite monochromated Mo KR radiation (λ ) 0.710 73 Å) at 173 K. Empirical absorption corrections were applied to the data using the SADABS program. The structures were solved by the direct method and refined by the full-matrix least-squares on F2 using the SHELXTL97 program.8 All of the non-hydrogen atoms were refined anisotropically. The H atoms bonded to C atoms were positioned geometrically and refined using a riding model [C-H 0.93 Å and Uiso(H) ) 1.2Ueq(C)]. The H atoms bonded to O atoms were located from difference maps and refined isotropically [Uiso(H) ) 1.2Ueq(O)]. Crystallographic data and structure refinements for 1-3 are summarized in Table 1. Selected bond lengths and bond angles are listed in Table 2. The corresponding hydrogen bodings of 1 and 2 are listed in Table 3. Crystallographic data for the structures reported in this paper have been deposited in the Cambridge Crystallographic Data Center with CCDC reference numbers 278632, 278630, and 278629 for compounds 1-3.

Results and Discussion [Cu2(adip)(H2O)4]n‚nH2O (1). Compound 1 is a 1D tubelike polymer. The asymmetric unit consists of two crystallographically independent Cu(II) ions, one adip4- unit, four coordinated water molecules, and one guest water molecule (Figure 1). All carboxyl groups of H4adip are deprotonated, in agreement with the IR data in which no characteristic absorption bands of the -COOH group at 1700-1750 cm-1 are observed. The Cu(1) center is five-coordinate. The structural index τ, [β - R]/60 with R and β being two largest angles, is zero for an ideal square pyramid and becomes unity for an ideal trigonal bipyramid.9 In this compound, the value of structural index τ is 0.026 for Cu(1), indicating that it is in slightly distorted square pyramid geometry. The basal plane of Cu(1) is defined by O(1), O(3), and N(1) from an aminodiacetic group and O(9) from a coordinated water molecule. The apical position is occupied by O(6A) from one rigid carboxyl group of adip4-. In contrast, the Cu(2) center shows a Jahn-Teller elongated octahedral geometry,10 binding four oxygen atoms in the equatorial plane

Figure 1. Diagram of Cu(1)2(adip)2 basic building block and its linkage to four Cu(2) ions, showing the atom connectivity and coordination environments in 1 (30% thermal ellipsoids probability). Symmetry codes: A, 1 - x, 1 - y, -z; B, x, y - 1, z; C, 1 - x, -y, -z.

1170 Crystal Growth & Design, Vol. 6, No. 5, 2006

Xu et al.

Table 2. Selected Bond Lengths (Å) and Bond Angles (deg) of Compounds 1-3 Cu(1)-O(1) Cu(1)-O(3) Cu(1)-O(9) Cu(1)-N(1) Cu(1)-O(6A) Cu(2)-O(11) Cu(2)-O(5) Cu(2)-O(10) Cu(2)-O(7B) Cu(2)-O(12) O(7)-C(12) O(8)-C(12)

Compound 1a 1.926(3) O(1)-Cu(1)-O(3) 1.953(2) O(1)-Cu(1)-O(9) 1.985(3) O(1)-Cu(1)-N(1) 2.078(3) O(3)-Cu(1)-N(1) 2.246(3) N(1)-Cu(1)-O(6A) 1.939(3) O(9)-Cu(1)-O(6A) 1.950(2) O(1)-Cu(1)-O(6A) 1.960(3) O(11)-Cu(2)-O(5) 2.032(2) O(11)-Cu(2)-O(10) 2.290(3) O(5)-Cu(2)-O(12) 1.264(4) O(5)-Cu(2)-O(10) 1.272(4) O(5)-Cu(2)-O(7B)

Co(1)-O(7D) Co(1)-O(7F) Co(1)-O(2E) Co(1)-O(2) Co(1)-O(1E) Co(1)-O(1) Co(2)-O(5) Co(2)-O(6) Co(2)-O(3) Co(2)-O(9A) Co(2)-O(4) Co(2)-O(6) N(1)-Co(2) O(10)-C(12) O(11)-C(12)

2.091(2) 2.091(2) 2.097(2) 2.097(2) 2.141(3) 2.141(3) 2.040(3) 2.044(3) 2.057(2) 2.070(2) 2.240(3) 2.044(3) 2.353(3) 1.316(4) 1.209(4)

Zn(1)-O(17A) Zn(1)-O(21C) Zn(1)-O(1) Zn(1)-O(3) Zn(1)-N(1) Zn(2)-O(4) Zn(2)-O(6) Zn(2)-O(5B) Zn(3)-O(19A) Zn(3)-O(8) Zn(3)-O(20A) Zn(3)-O(9) Zn(3)-O(7) Zn(3)-N(2A) Zn(4)-O(14) Zn(4)-O(10) Zn(4)-O(2C) Zn(4)-O(12) Zn(4)-O(13) K(1)-O(22) K(1)-O(11) K(1)-O(12C) K(1)-O(16A)

1.943(5) 2.009(5) 2.017(5) 2.058(5) 2.331(6) 2.069(5) 2.084(6) 2.180(5) 2.029(5) 2.045(5) 2.044(5) 2.169(5) 2.203(5) 2.344(6) 1.944(5) 1.975(5) 2.005(5) 2.104(5) 2.323(6) 2.819(6) 2.822(6) 2.785(5) 2.687(6)

Compound 2b O(2)-Co(1)-O(1) O(7F)-Co(1)-O(2) O(7D)-Co(1)-O(2) O(2E)-Co(1)-O(2) O(2)-Co(1)-O(1E) O(7D)-Co(1)-O(7F) O(1E)-Co(1)-O(1) O(5)-Co(2)-N(1) O(6)-Co(2)-O(3) O(3)-Co(2)-O(9A) O(5)-Co(2)-O(4) O(6)-Co(2)-N(1) O(3)-Co(2)-N(1) O(9A)-Co(2)-N(1) Compound 3c O(1)-Zn(1)-O(3) O(1)-Zn(1)-N(1) O(3)-Zn(1)-N(1) O(21C)-Zn(1)-N(1) O(17A)-Zn(1)-O(21C) O(17A)-Zn(1)-N(1) O(4B)-Zn(2)-O(4) O(6B)-Zn(2)-O(6) O(5B)-Zn(2)-O(5) O(4)-Zn(2)-O(5) O(4)-Zn(2)-O(6) O(19A)-Zn(3)-O(8) O(9)-Zn(3)-O(7) O(8)-Zn(3)-N(2A) O(19A)-Zn(3)-O(20A) O(8)-Zn(3)-O(9) O(8)-Zn(3)-O(7) O(14)-Zn(4)-O(10) O(12)-Zn(4)-O(13) O(2C)-Zn(4)-O(13) O(10)-Zn(4)-O(2C) O(22)-K(1)-O(11) O(22D)-K(1)-O(22)

Table 3. Hydrogen Bond Geometry of Compounds 1 and 2 D-H‚‚‚A

165.80(12) 95.38(11) 85.18(11) 83.99(11) 105.80(10) 89.95(10) 87.69(11) 90.91(12) 171.66(12) 104.70(11) 94.91(12) 149.46(10) 88.43(10) 84.45(9) 95.55(9) 180 91.57(10) 180 180 155.95(11) 100.41(11) 152.76(10) 83.78(12) 75.33(9)

D-H (Å)

H‚‚‚A (Å)

D‚‚‚A (Å)

∠D-H‚‚‚A (deg)

O(9)-H(9D)‚‚‚O(4F) O(10)-H(10A)‚‚‚O(8A) O(11)-H(11B)‚‚‚O(8H) O(11)-H(11B)‚‚‚O(10G) O(10)-H(10B)‚‚‚O(4C) O(11)-H(11A)‚‚‚O(4I) O(13)-H(13B)‚‚‚O(12J) O(9)-H(9C)‚‚‚O(2D) O(13)-H(13A)‚‚‚O(3E) O(12)-H(12B)‚‚‚O(2H)

Compound 1a 0.72 2.25 0.90 1.76 0.80 1.88 0.80 2.94 0.93 1.93 0.87 1.87 0.90 2.04 0.79 1.89 0.93 2.20 0.68 2.24

2.918(4) 2.648(4) 2.677(4) 3.402(4) 2.847(4) 2.731(4) 2.865(5) 2.680(4) 2.973(4) 2.907(4)

153 171 174 119 174 174 152 175 140 168

O(1)-H(1A)‚‚‚O(12G) O(4)-H(4A)‚‚‚O(8A) O(10)-H(10A)‚‚‚O(8F) O(12)-H(12A)‚‚‚O(11H) O(5)-H(5B)‚‚‚O(5I) O(5)-H(5A)‚‚‚O(1J)

Compound 2b 0.83 1.84 0.87 1.76 0.78 1.91 0.95 1.98 0.92 1.89 0.88 1.97

2.643(5) 2.591(4) 2.633(4) 2.928(5) 2.776(6) 2.768(4)

164 158 153 171 163 150

a Symmetry codes: A, -x + 1, -y + 1, -z; C, -x + 1, -y, -z; D, -x + 1, -y + 2, -z - 1; E, x, y, z + 1; F, -x + 1, -y + 1, -z - 1; G, x + 1, y, z; H, -x + 2, -y + 1, -z; I, -x + 2, -y, -z; J, -x + 1, -y, -z + 1. b Symmetry codes: A, -x + 1, -y, -z; F, x - 1, y + 1, z; G, x - 1, y, z; H, x + 1, y, z; I, -x + 1, -y, -z + 1; J, -x, -y + 1, -z + 1.

Chart 1

77.96(9) 87.72(9) 151.8(2) 78.5(1) 78.2(2) 141.0(2) 110.8(2) 107.4(2) 180 180 180 90.9(2) 93.6(2) 97.3(2) 59.7 (1) 172.2(2) 101.2(2) 91.5(2) 101.8(2) 133.1(2) 174.3(2) 79.7(2) 119.3(2) 145.0(1) 71.7(2)

a Symmetry codes: A, -x + 1, -y + 1, -z; B, x, y - 1, z; C, 1 - x, -y, -z; D, -x + 1, -y + 2, -z - 1; E, x, y, z + 1; H, -x + 2, -y + 1, -z. b Symmetry codes: A, -x + 1, -y, -z; D, -x, -y, -z + 1; E, -x 1, -y + 1, -z + 1; F, x - 1, y + 1, z; G, x - 1, y, z; H, x + 1, y, z; J, -x, -y + 1, -z + 1. c Symmetry codes: A, -x + 1, -y + 1, -z + 1; B, -x, -y, -z; C, -x, -y, -z + 1; D, -x + 1, -y, -z + 1.

[Cu(2)-O(10)/O(5)/O(11)/O(7B) ranging from 1.939(3) to 2.032(2) Å] and two oxygen atoms in the apical positions [Cu(2)-O(8B)/O(12) ) 2.474(3) and 2.290(3) Å, respectively]. The bond lengths of Cu-O in 1 vary from 1.926(3) to 2.474(3) Å, and the bond length of Cu(1)-N(1) is 2.078(3) Å, which are comparable to those reported for O-Cu-N compounds.4a,11 The whole adip4- anion in this compound can be viewed as a µ4-connector, which is shown in Chart 1,part a. The two rigid carboxyl groups exhibit different coordinate modes. One adopts a bidentate chelating mode; the other adopts a bidentate bridging mode. Meanwhile, the flexible aminodiacetic group clamps one

Cu ion with tridentate binding sites, which leads to the formation of two five-member rings of CuNC2O with a dihedral angle of 157.25°. The basic building block of this structure is the dinuclear Cu(1)2(adip)2 entity, in which two adip4- ligands link two metal nodes into a 14-member ring in head-to-tail mode with the Cu(1)‚‚‚Cu(1A) distance being 8.376 Å (Figure 1). It is worth noting that the presence of the flexible acetic arms and the participation of amino nitrogen of adip4- are crucial for the formation of such a ring. As distinctively shown in Figure 1, such Cu(1)2(adip)2 units are connected by the Cu(2)(H2O)3 motif to give rise to an interesting 1D tube framework along the b axis with the cross dimension of the hexagon channel being 8.38 Å × 7.53 Å (Figure 2), which is comparable to other reported 1D nanotubular coordination polymers.4d One COOgroup in 1 functions as a spacer between Cu(1A) and Cu(2), and the distance is 4.977 Å. Such tubes are further connected together by strong hydrogen bonding interactions between the

New Series of Metal(II)-H4adip Coordination Polymers

Crystal Growth & Design, Vol. 6, No. 5, 2006 1171

Figure 2. Side (a) and top (b) views of tube-like structure in 1. The ellipse part shows the basic building block Cu(1)2(adip)2.

Figure 4. Diagram of 2D layer architecture in 2. The ellipse part shows the basic building block Co(2)2(Hadip)2.

Figure 3. Perspective view of Co(2)2(Hadip)2 basic building block and its linkage to four Co(1) ions, showing the atom connectivity and coordination environment in 2. Symmetry codes: A, 1 - x, -y, -z; B, 1 + x, y, z - 1; C, 1 + x, y - 1, z; D, -x, -y, 1 - z; E, -x - 1, 1 - y, 1 - z; F, x - 1, 1 + y, z.

coordinated water molecules and carboxylate oxygen atoms (O(8H)‚‚‚O(11), 2.677 Å, and O(2D) ‚‚‚O(9), 2.680 Å). Additionally, one uncoordinated water molecule found resides outside the tubes. It consolidates the tube network through an intramolecular hydrogen bonding interaction (O(3)‚‚‚O(13E), 2.973(4) Å). In summary, various inter- and intramolecular hydrogen bonds (Table 3) play important roles in the construction of the 3D supramolecular framework of 1 (Figure S1). [Co3(Hadip)2(H2O)6]n‚2nH2O (2). Compound 2 crystallizes in space group P1h, and features a 2D layered network. There are one and a half Co ions, one Hadip3- ligand, six coordinated water molecules, and two guest water molecules in the asymmetric unit (Figure 3). The Co(1) center resides at an inversion center and is coordinated in a regular octahedral geometry by six oxygen atoms, four from aminodiacetic groups to form the equatorial plane and two from water molecules to occupy the axial positions. The Co(2) center is six-coordinated in strongly distorted octahedral coordination, with the equatorial plane consisting of one amino nitrogen atom and three oxygen atoms (two from Hadip3- and one from a H2O molecule), with the other two oxygen atoms occupying the axial sites (one from the acetic group and the other from a H2O molecule respectively). The Co-O bond lengths are in the range of 2.040(3)2.240(3) Å and the Co-N bond length is 2.353(3) Å, which are comparable to those reported for O-Co-N compounds.11c,12 Chart 1, part b, gives the coordination mode of Hadip3- in 2. One rigid carboxyl group adopts the monodentate mode, while the other is not deprotonated and remains free, as confirmed by the strong absorption band at 1708 cm-1 in the IR spectrum for the presence of the -COOH group. The flexible aminodiacetic group adopts a bridging-chelating mode to connect three

Figure 5. The topological (3,4)-connected 2D nets in 2: (a) Co(1) node characterized by (4.62); (b) Co(2)(µ-O2C)2 node (426282). The pale colored parts present the environment of two different metal node types.

Co atoms forming two CoNC2O five-member rings with a dihedral angle of 149.0°. Like the analogous Cu(1)2(adip)2 in 1 (Figure 1), the metallocycle Co(2)2(Hadip)2 in 2 also acts as a basic building block (Figure 3), with the Co(2)‚‚‚Co(2A) distance being 8.792 Å. Such basic building blocks are connected by four Co(1)(H2O)2 moieties on the ac plane through carboxyl oxygen atoms, with the Co(1)‚‚‚Co(2) distance being 5.429-5.458 Å. Accordingly, the layered inorganic-organic hybrid coordination polymer 2 is assembled, involving an infinite metal-carboxyl double-stranded chain (Figure 4). Topological analysis shows that 2 is the novel 2D (3,4)connected net predicted previously by Wells13, as is comparable to [Cu2(ipO)(4,4′-bpy)]n.14a As shown in Figure 5, each Co(1) is characterized as a 4-connected node by a short vertex symbol (4.62), and each Co(2)(µ-O2CR)2 is characterized as a 3-connected node with symbol (426282). Such 2D nets with both fourand six-membered rings, as well as both 3- and 4-connections, are rarely observed, since the 4-connected nodes generally favor the formation of 3D nets.14 The packing structure of 2 gives an interesting 3D network with narrow channels, constructed from 2D layers via hydrogen bonding interactions (O(1J)‚‚‚O(5), 2.768 Å; Table 3, Figure S2). The guest water molecules fill the channels. It affords two types of hydrogen bonding to increase the stability of the crystal (O(1)‚‚‚O(12G), 2.643(5) Å; O(12)‚‚‚O(11H), 2.928(5) Å).

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Figure 7. Perspective view of tetranuclear basic building block Zn(3)2Zn(4)2(adip)4 in 3. Symmetry codes: A, 1 - x, 1 - y, 1 - z; C, -x, -y, 1 - z; E, 1 + x, 1 + y, z.

Figure 6. Perspective view (a) of the coordination environments of Zn and K atoms in 3 and diagram (b) of the coordination configuration of K atom in 3. Symmetry codes: A, 1 - x, 1 - y, 1 - z; B, -x, -y, -z; C, -x, -y, 1 - z; D, 1 - x, -y, 1 - z.

[Zn7(adip)4(H2O)10K2(H2O)2]n‚4nH2O (3). The singlecrystal X-ray analysis reveals that the structure of 3 shows a novel 3D layered network. The asymmetric unit is composed of three and one-half independent Zn ions with the Zn(2) ion at an inversion center, two adip4- units, five coordinated water molecules, two guest water molecules, and one coordinated K(H2O)+ cation that balances the negative charge of the complex (Figure 6a). Both Zn(2) and Zn(3) are eight-coordinate with octahedral geometry, and Zn(1) and Zn(4) are five-coordinate. The values of structural index τ are 0.18 for Zn(1) and 0.25 for Zn(4), which indicate that both Zn centers have slightly distorted square pyramid geometries. The bond lengths of Zn-O (1.943(5)-2.323(6) Å) and Zn-N (2.331(6)-2.344(6) Å) are comparable to those reported.15 In this compound, the geometry around K(1) is a distorted triangular prism (Figure 6b). O(22), O(12C), and O(16D) form the basal face of the triangular prism, and O(11), O(11C), and O(22A) form the other basal plane. The K ions are linked through the oxygen bridges of water O(22) and carboxyl O(11) [O(11C)-K(1)-O(11), 73.10(17)°; O(22)K(1)-O(22D), 71.7(2)°], forming a K-O chain (Figure 8b). All carboxyl groups of H4adip in 3 are deprotonated as in compound 1. There are two additional types of coordination modes for adip4-: (i) In Chart 1, part c, adip4- acts as µ5ligand to link four Zn2+ ions and one K+ ion. One of the rigid carboxyl groups is monodentate; the other in the bis(monodentate) pattern bridges both Zn2+ ion and K+ ion. The aminodiacetic group adopts a chelating-bridging mode, but only connects two Co ions because one acetic oxygen atom does not participate in coordination. (ii) In Chart 1, part d, adip4acts as µ6-ligand to link five Zn2+ ions and one K+ ion. The aminodiacetic group adopts a bridging-chelating mode to link three Zn ions, with one rigid carboxyl group chelating one Zn

ion and the other coordinating to both Zn and K ions in a bis(monodentate) bridging mode. The tetranuclear unit Zn(3)2Zn(4)2(adip)4 in 3 can be viewed as a basic building block connecting 10 metal centers (four Zn(1), two Zn(2), two K, and two Zn(4) in Figure 7). Both Zn(1) and K(1) ions function as metal nodes to link the basic building blocks to form a belt-like chain, and the Zn(2) centers function as nodes to link these belts, resulting in the formation of a 2D layer with thickness in the bc plane (Figure 8a). Furthermore, the 2D layers are bound into the K-O chains through O(22) bridging K and Zn ions (Figure 8b) to construct a novel 3D structure. The rectangular channels with the dimension of 20.719 Å × 4.512 Å (based on the distances of K ions) are found in this structure (Figure 8c). Thermogravimetric Analyses. To study their stabilities, thermogravimetric analyses (TGA) of free ligand and compounds 1-3 were performed (Figure S3). For 1, there are four separate weight loss steps. The first weight loss began at 55 °C and was completed at 100 °C. The observed weight loss of 7.10% corresponds to the loss of the guest water molecules and one coordinated water molecule (calcd 7.05%). The second and third weight losses of 19.1% occurred in the range of 100-200 °C, corresponding to the loss of three coordinated water molecules and one -COO- group (calcd 27.8%). The fourth step began at 292 °C, which can be attributed to the further decomposition of adip4- ligands as compared with the free H4adip. The TGA curve of 2 indicates that the framework remained unchanged in the temperature range of 113-214 °C right after the loss of the guest water molecules. Then, the loss of coordinated water molecules was accompanied by the decomposition of the adip4- ligand. As a result, it is difficult to give the exact weight loss percentage for each weight loss step in the TGA curve, which is somewhat similar to what happened to the [Zn(HCPIDA)]n‚nH2O compound.4a The TGA curve of compound 3 exhibits a continuous weight loss. Similar to that of 2, it is difficult to give the exact weight loss percentage for each weight loss step in the TGA curve. But it is still clear that the collapse of the whole framework occurred at 398 °C. Magnetic Properties. The measurements on temperature dependence of the magnetic susceptibility at 2-300 K in a field of 10 kOe were investigated on Quantum Design PPMS60000 for magnetic ions containing compounds 1 and 2. But, the experimental effort to obtain good quality data of 1 seems to fail due to the low susceptivity of our equipment. Hence we focused on the magnetic behavior analysis of 2. The 1/χm and µeff per Co(II) ion versus T plots are shown in Figure 9. At 300 K, the µeff value for 2 is 4.55 µB, larger than the expected 3.87 µB for magnetically isolated high-spin Co(II) ions (SCo ) 3/2, g

New Series of Metal(II)-H4adip Coordination Polymers

Crystal Growth & Design, Vol. 6, No. 5, 2006 1173

Figure 8. Diagram of 2D layers linked by K-O chains to form a novel 3D structure in 3.

Figure 9. Plots of experimental µeff vs T and 1/χm vs T of 2. The solid red line shows the Curie-Weiss fitting.

) 2.0). This larger value is the result of contributions to the susceptibility from orbital angular momentum at high temperature. Between 10 and 300 K, the magnetic susceptibility χm can be well fitted to the Curie-Weiss law, χm ) Cm/(T - θ) with Cm ) 2.713 cm3 mol-1 and θ ) -14.7 K. Further theoretical simulations for 2 were carried out but were not successful, since its magnetic action was so complicated in such a 2D Co(II) polymer. Even then, it is clear that both the decrease of the effective magnetic moment with temperature in the µeff vs T plot and the small negative θ value indicate the presence of antiferromagnetic interactions among adjacent Co(II) ions and to some extent of spin-orbit coupling effects.16a Comparable antiferromagnetic interactions between the cobalt ions were also reported in other cobalt compounds.16 Photoluminescent Property. The emission spectra of H4adip and compound 3 were investigated in the solid state at room temperature. H4adip exhibits a broad strong green fluorescent emission around 521 nm upon excitation at 410 nm (Figure 10a). In the case of the Zn-adip polymer 3, an intense blue-shifted emission with the main peak at 454 nm is observed (Figure 10b). The emission was determined to be photoluminescence based on its nanosecond-order decay lifetime (14.11 ns). This blue-fluorescent emission may derive from ligand-tometal charge transfer (LMCT), considering the presence of multiple charge transfers with close transition energies caused by the complicated structure of 3 5a,17.

Figure 10. The emission spectra in the solid state at room temperature: (a) free H4adip ligand (λex ) 410 nm); (b) compound 3 (λex ) 300 nm).

Conclusion A series of novel coordination polymers with various architectures were constructed from a new type of multicarboxylate ligands, adip4-, and the transition metal(II) ions. The strong coordinate abilities of rigid carboxylate groups and flexible acetic groups, as well as amino nitrogen, endow this bridging-chelating adip4- ligand with abundant coordination modes. It adapts the coordination of metal(II) ions to construct basic building blocks (M2(adip)2, M2(Hadip)2, M4(adip)4) and extend the infinite architectures with their free Oexo atoms. In addition, guest water molecules are founded inside channels of these compounds. Our research results indicate that, as a promising new type of multicarboxylate ligand, adip4- has a great potential in the field of coordination polymers, and further endeavors for exploration of adip4- containing compounds are underway in our workgroup. Acknowledgment. This work was supported by the grants of National Nature Science Foundation of China and Nature Science Foundation of Fujian Province. Supporting Information Available: Figures showing the packing of one-dimensional tubes in 1, the 3-D supramolecular structure of 2,

1174 Crystal Growth & Design, Vol. 6, No. 5, 2006 and TGA curves for 1-3 and free ligand and crystallographic information in CIF format for 1-3. This material is available free of charge via the Internet at http://pubs.acs.org.

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