Syntheses and Structures of Three Unprecedented Metal

Syntheses and Structures of Three Unprecedented Metal-Ciprofloxacin Complexes with Helical Character Dong-Rong Xiao, En-Bo Wang,* Hai-Yan An, Yang-Guang Li, and Lin Xu Key Laboratory of Polyoxometalate Science of Ministry of Education, Institute of Polyoxometalate Chemistry, Department of Chemistry, Northeast Normal UniVersity, Changchun, 130024, P. R. China

CRYSTAL GROWTH & DESIGN 2007 VOL. 7, NO. 3 506-512

ReceiVed July 26, 2006; ReVised Manuscript ReceiVed NoVember 27, 2006

ABSTRACT: Self-assemblies of the fluoroquinolone ciprofloxacin (cfH) and zinc salt in the presence of V-shaped polycarboxylate ligands yielded three unprecedented helical metal-cfH complexes, namely, [Zn(cfH)(Hbtc)]‚H2O (1), [Zn2(cfH)2(odpa)] (2), and [Zn2(cfH)2(bptc)]‚4H2O (3) (btc ) 1,3,5-benzenetricarboxylate, odpa ) 4,4′-oxydiphthalate, bptc ) 3,3′,4,4′-benzophenonetetracarboxylate). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, and thermogravimetric analyses. Compound 1 is a unique helical metal-cfH complex containing three types of helices. This case is still rare in metal-organic complexes. Compound 2 exhibits a novel two-dimensional (2D) chiral layer structure featuring two distinct helices, in which the hydrogen-bonded double-stranded helix is quite uncommon. The chiral layer structure of 3 is similar to that of 2. However, due to the existence of guest water molecules, the pitch of the helices in 3 is longer than those in 2, which indicates that the pitch of the helices in 2 and 3 could be tuned through the incorporation of guest molecules. To the best of our knowledge, compounds 1-3 represent the first examples of metal-quinolone complexes containing helical and chiral structures. Furthermore, the photoluminescent properties of compounds 1 and 3 were studied. Introduction The design and synthesis of metal-organic frameworks are of great current interest, not only because of their tremendous potential applications in gas storage, chemical separations, ion exchange, microelectronics, nonlinear optics, and heterogeneous catalysis, but also because of their intriguing variety of architectures and topologies.1-2 A particularly interesting and challenging area in this field is the synthesis of helical coordination polymers and exploration of their potential utilities in asymmetric catalysis and nonlinear optics.3-4 Compounds with helical structures have attracted a great deal of attention from chemists because living organisms utilize helices to store and transmit genetic information. More importantly, these helical compounds have broad applications (optical devices, sensory functions) and characteristic features.4-11 On the basis of the pioneering work of Lehn and co-workers,6 a variety of appealing helical coordination polymers have been constructed8-11 and well discussed in comprehensive reviews by Okamoto and Albrecht.4 In contrast, the occurrence of metal-drug complexes with helical character is particularly rare, although many organic drugs have the potential to act as ligands, and the resulting helical metal-drug complexes are particularly important both in coordination chemistry and biochemistry.12-16 Moreover, hydrogen bonding, which plays a fundamental role in the structures of DNA and proteins,6c,17 are known to exert important effects on the supramolecular assemblies in chemical and biological systems.18 However, to our knowledge, no metaldrug complexes containing hydrogen-bonded helices have been reported so far, implying a challenging issue in coordination chemistry. Ciprofloxacin [1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7(1-piperazinyl)-3-quinoline carboxylic acid (cfH)] (Scheme S1, Supporting Information), a fluoroquinolone antibacterial agent with a wide spectrum of activity, is extremely useful for the treatment of a variety of infections.13-15 The mechanisms of action of the quinolone antibacterial agents are either their * To whom correspondence should be addressed. [email protected]. Fax: +86-431-5098787.

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inhibition of DNA gyrase (topoisomerase II), an essential bacterial enzyme responsible for converting DNA into a negative superhelical form, or their interaction with the bacterial DNA molecule via a metal complex intermediate.12-15 The molecular details of the mechanisms of quinolone still remain unknown, but most models include metal ions, either as a cofactor for the gyrase activity or as a neutralizing agent of the negative phosphate groups of DNA.13-16 It is obvious that the metal ions may play a very important role in the mechanisms of the action of these drugs, whereas the structurally characterized metalquinolone complexes are still rare, as evidenced in a recent review by Iztok Turel.13 Furthermore, as mentioned above, the interaction of quinolones with helix (DNA) is essential for the mechanisms of action of the quinolone antibacterial drugs; however, to the best of our knowledge, no helical metal-cfH complexes, which may provide a structural model displaying the interaction between cfH and helix, have been reported to date. The possible reason is that the steric hindrance at the metal center will be increased when the bulky cfH ligand binds to the metal ion, which may restrain spatial extension of the skeleton and thus prevent the formation of a helical structure. Therefore, the exploration of feasible synthetic routes to construct helical metal-cfH complexes is still a great challenge for synthetic chemists, and further research is necessary to enrich and develop this field. Inspired by the aforementioned considerations, our current synthetic strategy is to acquire helical metal-cfH complexes via linking the discrete metal-cfH motif with V-shaped aromatic polycarboxylate ligands. V-shaped aromatic polycarboxylates are introduced for the following reasons: (i) Recent works have proved that a suitable choice of V-shaped bridging ligands could provide great possibilities for the formation of helices.3f,4c,4d,8a,8b,10a,11b (ii) The use of aromatic polycarboxylates as bridging ligands to construct high-dimensional structures is relatively mature. Therefore, the topologies of resulting structures can be predicted and designed.11 (iii) So far, the coordination polymers constructed from the mixed quinolones and aromatic polycarboxylate ligands are still very rare. This could be related to the fact that two carboxyl-containing ligands would

10.1021/cg060492c CCC: $37.00 © 2007 American Chemical Society Published on Web 01/31/2007

Metal-Ciprofloxacin Complexes with Helical Character

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Table 1. Crystal Data and Structure Refinement for Compounds 1-3

a

complex

1

2

3

formula fw T (K) λ (Å) crystal system space group a (Å) b (Å) c (Å) β (deg) V (Å3) Z Dc (g/cm3) µ (mm-1) R1a [I > 2σ(I)] wR2b [I > 2σ(I)] R1 (all data) wR2 (all data)

C26H24FN3O10Zn 622.85 293(2) 0.71073 monoclinic P21/n 12.4906(13) 12.3673(13) 16.6196(17) 100.954(2) 2520.5(5) 4 1.641 1.049 0.0306 0.0778 0.0433 0.0800

C50H42F2N6O15Zn2 1135.64 293(2) 0.71073 monoclinic C2/c 25.300(5) 10.910(2) 19.079(4) 120.79(3) 4524(2) 4 1.667 1.152 0.0513 0.0896 0.0852 0.1006

C51H50F2N6O19Zn2 1219.71 293(2) 0.71073 monoclinic C2/c 24.763(5) 12.380(3) 17.729(4) 113.20(3) 4996(2) 4 1.622 1.055 0.0431 0.1136 0.0590 0.1225

R1 ) ∑||F0| - |FC||/∑|F0|. b wR2 ) ∑[w(F02 - FC2)2]/∑[w(F02)2]1/2.

yield more negative charges and make the charge balance difficult. Because the mixing of metal salt and cfH solution usually results in a precipitation, making it difficult to grow crystals of complexes, we adopted a hydrothermal technique and successfully synthesized three novel helical metal-cfH complexes, namely, [Zn(cfH)(Hbtc)]‚H2O (1), [Zn2(cfH)2(odpa)] (2), and [Zn2(cfH)2(bptc)]‚4H2O (3) (btc ) 1,3,5-benzenetricarboxylate, odpa ) 4,4′-oxydiphthalate, bptc ) 3,3′,4,4′benzophenonetetracarboxylate), which represent the first examples of metal-quinolone complexes containing helical and chiral structures. Of particular interest are the three-dimensional (3D) supramolecular networks of 1-3 featuring multiform hydrogen-bonded helices. Experimental Section General Considerations. All chemicals were commercially purchased and used without further purification. Elemental analyses (C, H, and N) were performed on a Perkin-Elmer 2400 CHN Elemental analyzer. Zn was determined by a Leaman inductively coupled plasma (ICP) spectrometer. IR spectra (Figure S15, Supporting Information) were recorded in the range 400-4000 cm-1 on an Alpha Centaurt FT/ IR spectrophotometer using KBr pellets. TG analyses were performed on a Perkin-Elmer TGA7 instrument in flowing N2 with a heating rate of 10 °C‚min-1. Excitation and emission spectra were obtained on a SPEX FL-2T2 spectrofluorometer equipped with a 450 W xenon lamp as the excitation source. Synthesis of [Zn(cfH)(Hbtc)]‚H2O (1). A mixture of Zn(OAc)2‚ 2H2O (0.5 mmol), ciprofloxacin hydrochloride (0.5 mmol), H3btc (0.25 mmol), and water (8 mL) was stirred for 30 min in air, then transferred and sealed in an 18 mL Teflon-lined autoclave, which was heated at 125 °C for 96 h. After the sample was slow cooled to room temperature, colorless block crystals of 1 were filtered off, washed with distilled water, and dried at ambient temperature (yield: 78% based on H3btc). Anal. Calcd (%) for C26H24FN3O10Zn (622.85): C 50.14; H 3.88; N 6.75; Zn 10.50; found: C 50.48; H 3.67; N 6.56; Zn 10.32%. Synthesis of [Zn2(cfH)2(odpa)] (2). The preparation of 2 was similar to that of 1 except that H4odpa was used instead of H3btc. Colorless block crystals were obtained in 69% yield (based on Zn). Anal. Calcd (%) for C50H42F2N6O15Zn2 (1135.64): C 52.88; H 3.73; N 7.40; Zn 11.52; found: C 53.11; H 3.54; N 7.20; Zn 11.29%. Synthesis of [Zn2(cfH)2(bptc)]‚4H2O (3). The preparation of 3 was similar to that of 1 except that H4bptc was used instead of H3btc. Colorless block crystals were obtained in 75% yield (based on Zn). Anal. Calcd (%) for 3 C51H50F2N6O19Zn2 (1219.71): C 50.22; H 4.13; N 6.89; Zn 10.72; found: C 49.98; H 3.97; N 7.12; Zn 10.95%. X-ray Crystallography. Suitable single crystals with dimensions of 0.56 × 0.49 × 0.43 mm for 1, 0.48 × 0.41 × 0.35 mm for 2, and 0.53 × 0.47 × 0.38 mm for 3 were selected for single-crystal X-ray

Table 2. Selected Bond Lengths [Å] and Angles [°] for 1-3a 1 Zn(1)-O(2) Zn(1)-O(5) Zn(1)-O(6)#1 N1‚‚‚O6 O(2)-Zn(1)-O(5) O(2)-Zn(1)-O(6)#1 O(5)-Zn(1)-O(6)#1 O(2)-Zn(1)-O(3) O(5)-Zn(1)-O(3)

1.9423(13) 1.9774(12) 1.9933(14) 2.841(2) 112.91(5) 131.86(5) 107.04(5) 92.73(5) 114.73(5)

Zn(1)-O(2) Zn(1)-O(7)#1 Zn(1)-O(5) N1‚‚‚O7 O(2)-Zn(1)-O(7)#1 O(2)-Zn(1)-O(5) O(7)#1-Zn(1)-O(5) O(2)-Zn(1)-O(3) O(7)#1-Zn(1)-O(3)

1.920(3) 1.963(2) 2.003(3) 2.821(19) 119.99(12) 122.74(11) 108.49(11) 92.89(10) 104.93(10)

Zn(1)-O(7)#1 Zn(1)-O(3) Zn(1)-O(2) N1‚‚‚O7 O(7)#1-Zn(1)-O(3) O(7)#1-Zn(1)-O(2) O(3)-Zn(1)-O(2) O(7)#1-Zn(1)-O(4) O(3)-Zn(1)-O(4)

1.958(2) 1.967(2) 1.969(2) 2.99(1) 107.71(9) 116.27(10) 92.36(9) 108.02(11) 133.58(11)

Zn(1)-O(3) 1.9994(12) Zn(1)-O(4) 2.4356(13) N1‚‚‚O1 2.672(3) O9‚‚‚O7 2.698(2) O(6)#1-Zn(1)-O(3) 94.08(5) O(2)-Zn(1)-O(4) 87.78(5) O(5)-Zn(1)-O(4) 58.90(5) O(6)#1-Zn(1)-O(4) 90.72(5) O(3)-Zn(1)-O(4) 173.06(5) 2 Zn(1)-O(3) 2.028(2) Zn(1)-O(4) 2.352(3) N1‚‚‚O1 2.765(23) C12‚‚‚O6 3.094(50) O(5)-Zn(1)-O(3) 102.74(10) O(2)-Zn(1)-O(4) 89.40(11) O(7)#1-Zn(1)-O(4) 91.69(11) O(5)-Zn(1)-O(4) 59.30(10) O(3)-Zn(1)-O(4) 159.19(10) 3 Zn(1)-O(4) Zn(1)-O(5) N1‚‚‚O1 O(2)-Zn(1)-O(4) O(7)#1-Zn(1)-O(5) O(3)-Zn(1)-O(5) O(2)-Zn(1)-O(5) O(4)-Zn(1)-O(5)

1.998(2) 2.403(3) 2.737(21) 97.49(10) 93.56(11) 91.29(10) 147.08(10) 57.92(10)

a Symmetry transformations used to generate equivalent atoms: for 1: #1 -x + 3/2, y - 1/2, -z - 1/2; #2 -x + 3/2, y + 1/2, -z - 1/2; for 2: #1 -x + 1/2, y + 1/2, -z + 1/2; #2 -x + 1/2, y - 1/2, -z + 1/2; #3 -x + 1, y, -z + 1/2; for 3: #1 -x - 1/2, y - 1/2, -z - 1/2; #2 -x - 1/2, y + 1/2, -z - 1/2; #3 -x - 1, y, -z - 1/2.

diffraction analysis (diffractometer device type: Bruker Smart-Apex CCD for 1 and Rigaku R-AXIS RAPID IP for 2 and 3). Empirical absorption correction was applied. The structures of 1-3 were solved by the direct method and refined by the Full-matrix least-squares on F2 using the SHELXL-97 software.19 All of the non-hydrogen atoms were refined anisotropically. The organic hydrogen atoms were generated geometrically; the aqua hydrogen atoms were not located. Little crystallographic disorder can be observed for the C12 and C13 atoms of the cfH molecule in 3. The crystal data and structure refinement of compounds 1-3 are summarized in Table 1. Selected bond lengths and angles for 1-3 are listed in Table 2. CCDC reference numbers: 294181 for 1, 294182 for 2, and 294183 for 3.

508 Crystal Growth & Design, Vol. 7, No. 3, 2007

Figure 1. ORTEP drawing of 1 with thermal ellipsoids at 50% probability.

Xiao et al.

Figure 3. Perspective view of the 3D supramolecular network in 1. The hydrogen bonds are indicated by dotted lines.

Figure 2. Perspective views of the 1D helical structures of 1 (a), highlighting the covalent helices (b).

Results and Discussion

Figure 4. Perspective and space-filling views of the first type of hydrogen-bonded helices in 1. The hydrogen bonds are indicated by dotted lines.

Descriptions of Crystal Structures. Single-crystal X-ray diffraction analysis reveals that 1 is a unique helical coordination polymer containing three types of helices. As shown in Figure 1, the crystallographically independent Zn atom exhibits a distorted trigonal-bipyramidal geometry, being coordinated by two oxygen atoms of one cfH ligand and three oxygen atoms from two btc ligands. Three carboxylic groups of btc ligand exhibit three kinds of coordination modes, that is, the bidentate chelating, monodentate and noncoordinated mode (Scheme S2a, Supporting Information). On the basis of these connection modes, the Zn atoms are linked by V-shaped bridging btc ligands to form the left- and right-handed helical chains running along a crystallographic 21 axis in the b direction with a pitch of 12.3673 Å (Figure 2b). The cfH groups, grafted on helical chains, are just like lateral arms (with a length of ca. 9.9 Å) protruding from two sides of the chain (Figure 2a). In the packing arrangement of 1, the adjacent same-handed helical chains are interconnected by strong hydrogen-bonding interactions (N1‚‚‚O1 2.672 Å, N1‚‚‚O6 2.841 Å, and O9‚‚‚O7 2.698 Å) to generate a two-dimensional (2D) chiral layer parallel to ab plane (Figure S1, Supporting Information). In fact, we were unable to reach an efficient packing model of layer with heterochiral helices by using the structural parameters of 1, implying that a chiral molecular recognition between the homochiral helices occurs through strong hydrogen bonds.8c,18 Interestingly, the two types of chiral layers, one left-handed and the other right-handed, are further connected by means of

aromatic π-π stacking interactions of cfH groups (separation 3.3-3.5 Å) to form a racemic 3D supramolecular network (Figure 3). The most fascinating structural feature of 1 is that three distinct helical chains running along the crystallographic b-axis coexist in the 3D network. This case is rather rare even though a few elegant coordination networks containing two types of helices have previously been characterized.9,10 Besides the covalent helices, there are two types of hydrogen-bonded helices with a pitch of 12.3673 Å in 1. The first type of hydrogenbonded helix is formed by strong hydrogen bonds between the protonated carboxylic groups and the monodentate carboxylic groups of Hbtc ligands (O9‚‚‚O7 2.698 Å, Figure 4). As shown in Figure 5, the [Zn(cfH)O] units are interconnected by means of strong hydrogen bonds (N1‚‚‚O6 2.841 Å) to generate the second type of hydrogen-bonded helix, which is further entangled by the first type of hydrogen-bonded helix with the same helical orientation to produce the intertwined homo-axis hydrogen-bonded helices (Figure 6). So far, the examples that have interweaving of two kinds of helices with the same helix axis are still few.10 Obviously, these strong hydrogen bonds undoubtedly steer the rotation direction of the helix.5g,5h It is worth noting that the use of hydrogen bonds as a steering force is becoming a very important strategy in crystal engineering.17,18 As known by us, compound 1 represents the first example of metal-quinolone complexes containing hydrogen-bonded helices.



Figure 7. ORTEP drawing of 2 with thermal ellipsoids at 50% probability.

Figure 5. Perspective and space-filling views of the second type of hydrogen-bonded helices in 1. The hydrogen bonds are indicated by dotted lines.

Figure 8. Perspective views of the left-handed layers in 2 (a) and 3 (c), highlighting that the pitch of the covalent helix in 3 (d) is longer than that in 2 (b).

Figure 6. Viewing of the relationship between the first (blue) and second types of hydrogen-bonded helices. The hydrogen bonds are indicated by dotted lines.

To interlink the one-dimensional (1D) helical motifs through covalently bonded interactions into a homochiral array of higher dimensionality, a long V-shaped ligand odpa, whose coordination chemistry has not been previously investigated, was used instead of btc. As expected, compound 2 with a chiral layer structure was isolated. There is one unique Zn atom in the asymmetric unit of 2 (Figure 7). Each Zn atom is coordinated by two oxygen atoms from one cfH ligand and three oxygen atoms from two carboxylic groups of two odpa ligands, showing a distorted trigonal-bipyramidal geometry. The odpa ligand adopts a hexadentate chelating and bridging coordination mode; two carboxylic groups chelate with two ZnII ions bidentately, while the other two adopt a monodentate coordination mode and connect with two metal ions (Scheme S2c, Supporting

Information). On the basis of this connection mode, the ZnII atoms are bridged by V-shaped phthalic groups of odpa ligands to form the left- and right-handed helical chains running along a crystallographic 21 axis in the b direction with a pitch of 10.91 Å (Figures 8b and S2b, Supporting Information). Similar to compound 1, the helical chains are decorated with cfH ligands alternately at two sides. As shown in Figure 8a, adjacent samehanded helical chains are further interconnected through O(8) atoms to generate a 2D chiral layer of very large honeycomb windows (with dimensions of 9.72 × 17.99 Å, Figure S3, Supporting Information). To our knowledge, such a 2D chiral layer framework has not been reported in the system of metalquinolones. More interestingly, apart from the helices mentioned above, a hydrogen-bonded double-stranded helix displaying the opposite helical orientation to the covalent helix also exists in the chiral layers. The hydrogen-bonded double-stranded helix (Figure 9) is constructed by cfH ligands and N1 atoms bridged between the O1-C1-O2-Zn1-O7 units through the strong hydrogen bonds (N1‚‚‚O1 2.765 Å and N1‚‚‚O7 2.821 Å). The pitch of the hydrogen-bonded helix is 21.82 Å. As known by us, such intertwined hydrogen-bonded double-stranded helix is still quite uncommon within helical coordination polymers. In the packing mode of 2 (Figure 11), the two types of chiral layers, one left-handed and the other right-handed, crystallize in pairs


Figure 9. Perspective and space-filling views of the hydrogen-bonded double-stranded helices in 2. The hydrogen bonds are indicated by dotted lines.

Figure 10. Space-filling views hydrogen-bonded double-stranded helices in 2 (a) and 3 (b), showing the tunable hydrogen-bonded doublestranded helices in 2 and 3.

Figure 11. Perspective view of the 3D supramolecular network in 2. The hydrogen bonds are indicated by dotted lines.

in a space group C2/c with an inversion center, leading to a racemic solid-state compound. As expected, when bptc, an analogue of odpa, was used as a bridging ligand, a similar 2D chiral layer (Figure 8c) is formed in 3. The local structure of 3 (Figure S6, Supporting Information) is almost identical with that of 2. However, due to the existence of guest water molecules, the honeycomb window in 3 (with

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dimensions of 11.11 × 17.30 Å, Figure S10, Supporting Information) is larger than that in 2 (with dimensions of 9.72 × 17.99 Å), as indicated by the difference of the unit-cell volume (4524(2) Å3 in 2 and 4996(2) Å3 in 3). Furthermore, the b-axis length in 3 is also longer than that in 2.19 As a result, the pitch of the helices in 3 (Figures 8d and 10b) is longer than those in 2, although the shape and building units of the helices in 2 and 3 are very similar. The difference of the helices in 2 and 3 indicated that the pitch of the helices could be tuned through the incorporation of guest molecules (Figure S9, Supporting Information). As far as we know, such tunable molecular helices are still very rare in the system of metalorganic complex, although the tunable helices are important in the molecular recognition materials such as sensor, molecular switch, and chemical separator.3 Moreover, a careful examination shows that the packing arrangement of chiral layers in 2 and 3 is slightly different, which can be attributed to the sliding of the 2D nets (Figure S12, Supporting Information) triggered by the guest water molecules.20 The sliding distance is ca. 1.4 Å. In a comparison of the structures of 1-3, it was found that the steric geometry of the polycarboxylate ligands has a very significant effect on the formation and dimension of the resulting structure. Because of the steric hindrance of the bulky cfH ligands, the distance between the carboxylic groups and the length of polycarboxylate ligands are essential for the generation of a high-dimensional structure. From the regular trend observed for 1-3, we can see that the increase in length of polycarboxylate ligands induces the progressive increase in dimension of the ultimate structure (from 1D to 2D); in other words, the length of polycarboxylate ligands plays a crucial role in tuning the dimension of the metal-quinolone complex. Furthermore, by inspection of the structures of 1-3, it is believed that the V-shaped btc ligand, V-shaped phthalic group of odpa (or bptc) ligands, and V-shaped O‚‚‚H-N-H‚‚‚O hydrogen bonds are important for the formation of the helical structures. Thermal Stability Analysis. To examine the thermal stability of compounds 1-3, thermal gravimetric (TG) analyses were carried out for 1-3 (Figure S13, Supporting Information). The TG curve of 1 exhibits four steps of weight losses (Figure S13a, Supporting Information). The first weight loss is 3.03% in the temperature range of 45-160 °C, which corresponds to the loss of non-coordinated water molecules (calcd. 2.89%). The second weight loss is 5.33% at 160-340 °C; the third step is 47.03% from 340 to 500 °C, and the last step is 31.12% in the temperature range of 500-775 °C, all assigned to the decomposition of cfH and Hbtc ligands (calcd. 84.04%). The remaining weight (13.49%) indicated that the final product was ZnO (calcd. 13.07%). The TG curve of 2 exhibits two weight loss stages in the temperature ranges 295-845 (59.39%) and 845-1240 °C (26.15%) (Figure S13b, Supporting Information), corresponding to the release of cfH and odpa ligands. The residue is ZnO. The whole weight loss (85.54%) is in good agreement with the calculated value (85.67%). The TG curve of 3 is shown in Figure S13c, Supporting Information. It gives a total weight loss of 87.01% in the range of 45-760 °C, which agrees with the calculated value of 86.65%. The first weight loss is 5.75% in the temperature range of 45-95 °C, which corresponds to the loss of non-coordinated water molecules (calcd. 5.91%), and then the sample keeps relatively stable in the temperature range of 95-305 °C, probably suggesting the formation of a stable phase formulated



of metal-quinolones. The successful isolation of these solid materials not only provides the first examples of helical metalcfH complexes but also further confirms the aesthetic diversity of coordination chemistry. This work may open a new avenue in the exploration of metal-quinolone complexes with helical or chiral characters. Acknowledgment. The authors thank the National Natural Science Foundation of China (20371011) for financial support. Supporting Information Available: X-ray crystallographic files for compounds 1-3 in CIF format, and additional plots of the structures. This materials is available free of charge via the Internet at http:// pubs.acs.org.

References

Figure 12. Solid-state emission spectra of complexes at room temperature: (a) 1; (b) 3.

as [Zn2(cfH)2(bptc)]. The second weight loss is 40.66% from 305 to 495 °C, and the third step is 40.60% from 495 to 760 °C, both assigned to the decomposition of cfH and bptc ligands (calcd. 80.74%). The remaining weight (12.99%) corresponds to the percentage (13.35%) of Zn and O components in ZnO, indicating that this is the final product. Photoluminescence Properties. Taking into account the excellent luminescent properties of d10 metal complexes, the luminescence of 1 and 3 were investigated. It can be observed that intense emissions occur at 422 nm (Figure 12a, λex ) 320 nm) for 1, and 479 nm (Figure 12b, λex ) 421 nm) for 3. To understand the nature of the emission band, the photoluminescence properties of cfH and H4bptc ligand were analyzed. It was found that two weak emissions at 431 and 476 nm could be observed for free cfH and H4bptc ligands, respectively (Figure S14, Supporting Information). Therefore, the emissions of 1 and 3 may be assigned to the intraligand fluorescent emission. The enhancement of luminescence may be attributed to ligand chelation to the metal center, which effectively increases the rigidity and asymmetry of the ligand and reduces the loss of energy by radiationless decay. These observations indicate that compounds 1 and 3 may be excellent candidates for potential photoactive materials. Conclusions In summary, we have prepared three helical metal-cfH complexes by appropriately combining V-shaped polycarboxylate ligands and fluoroquinolone, which fill a gap in the realm

(1) (a) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M.; Kim, J. Nature 2003, 423, 705. (b) Kitagawa, S.; Kitaura, R.; Noro, S. I. Angew. Chem., Int. Ed. 2004, 43, 2334. (c) Ockwig, N. W.; Delgado-Friederichs, O.; O’Keeffee, M.; Yaghi, O. M. Acc. Chem. Res. 2005, 38, 176. (d) Wang, Z.; Kravtsov, V. C.; Zaworotko, M. J. Angew. Chem., Int. Ed. 2005, 44, 2877. (2) (a) Batten S. R.; Robson, R. Angew. Chem., Int. Ed. 1998, 37, 1460. (b) Batten, S. R. Cryst. Eng. Comm. 2001, 3, 67. (c) Carlucci, L.; Ciani, G.; Proserpio, D. M. Coord. Chem. ReV. 2003, 246, 247. (d) Carlucci, L.; Ciani, G.; Proserpio, D. M. Cryst. Eng. Comm. 2003, 5, 269. (e) Hill, R. J.; Long, D. L.; Champness, N. R.; Hubberstey, P.; Schro¨der, M. Acc. Chem. Res. 2005, 38, 337. (3) (a) Meistermann, I.; Moreno, V.; Prieto, M. J.; Moldrheim, E.; Sletten, E.; Khalid, S.; Rodger, P. M.; Peberdy, J. C.; Isaac, C. J.; Rodger, A.; Hannon, M. J. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 5069. (b) Hannon, M. J.; Moreno, V.; Prieto, M. J.; Moldrheim, E.; Sletten, E.; Meistermann, I.; Isaac, C. J.; Sanders, K. J.; Rodger A. Angew. Chem., Int. Ed. 2001, 40, 880. (c) Hannak, R. B.; Fa¨rber, G.; Kornat, R.; Kraütler, B. J. Am. Chem. Soc. 1997, 119, 2313. (d) Orr, G. W.; Barbour, L. J.; Atwood, J. L.; Science 1999, 285, 1049. (e) Klug, A. Angew. Chem., Int. Ed. Engl. 1983, 22, 565. (f) Jung, O.-S.; Kim, Y. J.; Lee, Y.-A.; Park, J. K.; Chae, H. K. J. Am. Chem. Soc. 2000, 122, 9921. (e) Jung, O.-S.; Pierpont, C. G. J. Am. Chem. Soc. 1994, 116, 2229. (4) (a) Nakano, T.; Okamoto, Y. Chem. ReV. 2001, 101, 4013. (b) Nakano, T.; Okamoto, Y. Chem. ReV. 1994, 94, 349. (c) Albrecht, M. Chem. ReV. 2001, 101, 3457. (d) Moulton, B.; Zaworotko, M. J. Chem. ReV. 2001, 101, 1629. (e) Soghomonian, V.; Chen, Q.; Haushalter, R. C.; Zubieta, J.; O’Connor, C. J. Science 1993, 259, 1596. (f) Shi, Z.; Feng, S. H.; Gao, S.; Zhang, L.; Yang, G.; Hua, J. Angew. Chem., Int. Ed. 2000, 39, 2325. (5) (a) Hill, D. J.; Mio, M. J.; Prince, R. B.; Hughes, T. S.; Moore, J. S. Chem. ReV. 2001, 101, 3893. (b) Cornelissen, J. J. L. M.; Rowan, A. E.; Nolte, R. J. M.; Sommerdijk, N. A. J. M. Chem. ReV. 2001, 101, 4039. (c) Brunsveld, L.; Folmer, B. J. B.; Meijer, E. W.; Sijbesma, R. P. Chem. ReV. 2001, 101, 4071. (d) Schmuck, C. Angew. Chem., Int. Ed. 2003, 42, 2448. (e) Desiraju, G. R. Angew. Chem., Int. Ed. Engl. 1995, 34, 2311. (f) Piguet, C.; Bernardinelli, G.; Hopfgartner, G. Chem. ReV. 1997, 97, 2005. (g) Boldog, I.; Rusanov, E. B.; Chernega, A. N.; Sieler, J.; Domasevitch, K. V. Angew. Chem., Int. Ed. 2001, 40, 3435. (h) Domasevitch, K. V.; Boldog, I.; Rusanov, E. B.; Hunger, J.; Blaurock, S.; Schro¨der, M.; Sieler, J. Z. Anorg. Allg. Chem. 2005, 631, 1095. (6) (a) Lehn, J.-M.; Rigault, A.; Siegel, J.; Harrowfield, J.; Chevrier, B.; Moras, D. Proc. Natl. Acad. Sci. U.S.A. 1987, 84, 2565. (b) Berl, V.; Huc, I.; Khoury, R. G.; Krische, M. J.; Lehn, J.-M. Nature 2000, 407, 720. (c) Lehn, J.-M. Chem. Eur. J. 2000, 6, 2097. (d) Lehn, J.-M.; Supramolecular Chemistry; VCH: Weinheim, 1995. (7) (a) Gier, T. E.; Bu, X.; Feng, P.; Stucky, G. D. Nature 1998, 395, 154. (b) Neeraj, S.; Natarajan, S.; Rao, C. N. R. Chem. Commun. 1999, 165. (c) Xiao, D. R.; Xu, Y.; Hou, Y.; Wang, E. B.; Wang, S. T.; Li, Y. G.; Xu, L.; Hu, C. W. Eur. J. Inorg. Chem. 2004, 1385. (d) Bu, X.-H.; Tong, M.-L.; Chang, H.-C.; Kitagawa, S.; Batten, S. R. Angew. Chem., Int. Ed. 2004, 43, 192. (8) (a) Chen, X.-M.; Liu, G.-F. Chem. Eur. J. 2002, 8, 4811. (b) Cui, Y.; Lee, S. J.; Lin, W. J. Am. Chem. Soc. 2003, 125, 6014. (c) Zhang, J.-P.; Lin, Y.-Y.; Huang, X.-C.; Chen, X.-M.; Chem. Commun. 2005, 1258. (d) Zhang, J.; Li, Z.-J.; Kang, Y.; Cheng, J.-K.; Yao, Y.-G. Inorg. Chem. 2004, 43, 8085. (e) Wu, C.-D.; Lu, C-Z.; Lin, X.; Wu,


(9)

(10)

(11) (12)

(13) (14)

D.-M.; Lu, S.-F.; Zhuang, H.-H.; Huang, J.-S. Chem. Commun. 2003, 1284. (f) Mamula, O.; Zelewsky, A. v.; Bark, T.; Bernardinelli, G. Angew. Chem., Int. Ed. 1999, 38, 2945. (g) Horn, C. J.; Blake, A. J.; Champness, N. R.; Lippolis, V.; Schro¨der, M. Chem. Commun. 2003, 1488. (a) Kondo, M.; Miyazawa, M.; Irie, Y.; Shinagawa, R.; Horiba, T.; Nakamura, A.; Naito, T.; Maeda, K.; Utsuno, S.; Uchida, F. Chem. Commun. 2002, 2156. (b) Sun, D. F.; Cao, R.; Sun, Y. Q.; Bi, W. H.; Li, X.; Hong, M. C.; Zhao, Y. J. Eur. J. Inorg. Chem. 2003, 38. (c) Azumaya, I.; Uchida, D.; Kato, T.; Yokoyama, A.; Tanatani, A.; Takayanagi, H.; Yokozawa, T. Angew. Chem., Int. Ed. 2004, 43, 1360. (a) Han, L.; Hong, M. C.; Wang, R. H.; Luo, J. H.; Lin, Z. Z.; Yuan. D. Q. Chem. Commun. 2003, 2580. (b) Xiao, D. R.; Wang, E. B.; An, H. Y.; Li, Y. G.; Su, Z. M.; Sun, C. Y. Chem. Eur. J. 2006, 12, 6528. (c) Zang, S.; Su, Y.; Li, Y.; Ni, Z.; Zhu, H.; Meng, Q. Inorg. Chem. 2006, 45, 3855. (d) Sun, Y.-Q.; Zhang, J.; Chen, Y.-M.; Yang, G.-Y. Angew. Chem., Int. Ed. 2005, 44, 5814. (a) Rao, C. N. R.; Natarajan, S.; Vaidhyanathan, R. Angew. Chem., Int. Ed. 2004, 43, 1466. (b) Ye, B. H.; Tong, M. L.; Chen, X. M. Coord. Chem. ReV. 2005, 249, 545. (a) Yuan, R. X.; Xiong, R. G.; Abrahams, B. F.; Lee, G. H.; Peng, S. M.; Che, C. M.; You, X. Z. J. Chem. Soc. Dalton Trans. 2001, 2071. (b) Chen, Z. F.; Xiong, R. G.; Zuo, J. L.; Guo, Z.; You, X. Z.; Fun, H. K. J. Chem. Soc. Dalton Trans. 2000, 4013. (c) Chen, Z. F.; Xiong, R. G.; Zhang, J.; Chen, X. T.; Xue, Z. L.; You, X. Z. Inorg. Chem. 2001, 40, 4075. (d) Yuan, R. X.; Xiong, R. G.; Chen, Z. F.; Zhang, P.; Ju, H. X.; Dai, Z.; Guo, Z. J.; Fun, H. K.; You, X. Z. J. Chem. Soc. Dalton Trans. 2001, 774. (e) Qu, Z.-R.; Zhao, H.; Xing, L.-X.; Wang, X.-S. Chen, Z. F.; Yu, Z.; Xiong, R. G.; You, X. Z. Eur. J. Inorg. Chem. 2003, 2920. (f) Chen, Z.-F.; Li, B. Q.; Yuan, Y. L.; Xiong, R. G.; You, X. Z.; Feng, X.-L. Inorg. Chem. Commun. 2001, 4, 346. (g) Li, Y.-H.; Tang, Y.-Z.; Huang, X.-F.; Xiong R.-G. Z. Anorg. Allg. Chem. 2005, 631, 639. (h) Chen, Z. F.; Zhou, H.-L.; Liang, H.; Li, Y.; Xiong, R. G.; You, X. Z. Appl. Organometal. Chem. 2003, 17, 883. Turel, I. Coord. Chem. ReV. 2002, 232, 27 and references therein. (a) Xiao, D. R.; Wang, E. B.; An, H. Y.; Su, Z. M.; Li, Y. G.; Gao, L.; Sun, C. Y.; Xu, L. Chem. Eur. J. 2005, 11, 6673. (b) JimeńezGarrido, N.; Perello´, L.; Ortiz, R.; Alzuet, G.; Gonza´lez-A Ä lvarez, M.; Cantoń, E.; Liu-Gonza´lez, M.; Garcıá-Granda, S.; Pe´rez-Priede, M. J. Inorg. Biochem. 2005, 99, 677. (c) Drevensˇek, P.; Zupancˇicˇ, T.; Pihlar, B.; Jerala, R.; Kolitsch, U.; Plaper, A.; Turel, I. J. Inorg. Biochem. 2005, 99, 432. (d) Lo´pez-Gresa, M. P.; Ortiz, R.; Perello´,

Xiao et al.

(15)

(16)

(17)

(18)

(19)

(20)

L.; Latorre, J.; Liu-Gonza´lez, M.; Garcıá-Granda, S.; Pe´rez-Priede, M.; Cantoń, E. J. Inorg. Biochem. 2002, 92, 65. (e) Ruı´z, M.; Perello´, L.; Server-Carrıó, J.; Ortiz, R.; Garcıá-Granda, S.; Dıáz, M. R.; Cantoń, E. J. Inorg. Biochem. 1998, 69, 231. (f) Ruı´z, M.; Perello´, L.; Ortiz, R.; Castin˜eiras, A.; Maichle-Mo¨ssmer, C.; Cantoń, E. J. Inorg. Biochem. 1995, 59, 801. (g) Cantoń, E.; Ramon, M. S.; Jimenez, M. T.; Martinez, J. P. Chemotherapy 1993, 39, 394. (h) Cantoń, E.; Peman, J.; Cabrera, E.; Velert, M.; Orero, A.; Pastor, A.; Gobernado, M. Chemotherapy 1999, 45, 268. (i) Drevensˇek, P.; Ulrih, N. P.; Majerle, A.; Turel, I. J. Inorg. Biochem. 2006, 100, 1705. (a) Shen, L. L.; Pernet, A. G. Proc. Natl. Acad. Sci. U.S.A. 1985, 82, 307. (b) Palu`, G.; Valisena, S.; Ciarrocchi, G.; Gatto, B.; Palumbo, M. Proc. Natl. Acad. Sci. U.S.A. 1992, 89, 9671. (c) Palumbo, M.; Gatto, B.; Zagotto, G.; Palu`, G.; Trends Microbiol. 1993, 1, 232. (a) Robles, J.; Martıń-Polo, J.; A Ä lvarez-Valtierra, L.; Hinojosa, L.; Mendoza-Dıáz, G. Metal-Based Drugs 2000, 7, 301. (b) Sissi, C.; Perdona, E.; Domenici, E.; Feriani, A.; Howells, A. J.; Maxwell, A.; Palumbo, M. J. Mol. Biol. 2001, 311, 195. (c) Sissi, C.; Andreolli, M.; Cecchetti, V.; Fravolini, A.; Gatto, B.; Palumbo, M. Bioorg. Med. Chem. 1998, 6, 1555. (d) Son, G.-S.; Yeo, J.-A.; Kim, J.-M.; Kim, S. K.; Moon, H. R.; Nam, W. Biophy. Chem. 1998, 74, 225. (a) Atwood, J. L.; Steed, J. W. Encyclopedia of Supramolecular Chemistry; Marcel Dekker: New York, 2004. (b) Steed, J. W.; Atwood, J. L. Supramolecular Chemistry; Wiley, Chichester, 2000. (c) Adachi, K.; Sugiyama, Y.; Yoneda, K.; Yamada, K.; Nozaki, K.; Fuyuhiro, A.; Kawata, S. Chem. Eur. J. 2005, 11, 6616. (d) Desiraju, G. R.; Steiner, T. R. The Weak Hydrogen Bond in Structural Chemistry and Biology; Oxford University Press, Oxford, 1999. (a) Fredericks, J. R.; Hamilton A. D. Hydrogen bonding control of molecular self-assembly: Recent advances in design, synthesis, and analysis, in ComprehensiVe Supramolecular Chemistry; Sauvage, J. P.; Hosseini, M.W., Eds.; Pergamon, Oxford, 1996; Vol. 9, Chapter 16. (b) Lehn, J. M. Science 2002, 295, 2400. (c) Wang, Y.; Yu, J.; Li, Y.; Shi, Z.; Xu, R. Chem. Eur. J. 2003, 9, 5048. (d) Song, Y.; Yu, J.; Li, Y.; Li, G.; Xu, R. Angew. Chem., Int. Ed. 2004, 43, 2399. (a) Sheldrick, G. M. SHELXS 97, Program for Crystal Structure Solution; University of Go¨ttingen: Germany, 1997. (b) Sheldrick, G. M. SHELXL 97, Program for Crystal Structure Refinement; University of Go¨ttingen: Germany, 1997. Biradha, K.; Hongo, Y.; Fujita, M. Angew. Chem., Int. Ed. 2002, 41, 3395.

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Syntheses and Structures of Three Unprecedented Metal

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