Syntheses, Structure, and Properties of the Metal Complexes with 3

Syntheses, Structure, and Properties of the Metal Complexes with 3-(2-Pyridyl)pyrazole-Based Ligands: Tuning the Complex Structures by Ligand Modifications Ru-Qiang Zou, Chun-Sen Liu, Zheng Huang, Tong-Liang Hu, and Xian-He Bu*

CRYSTAL GROWTH & DESIGN 2006 VOL. 6, NO. 1 99-108

Department of Chemistry and State Key Lab of Elemento-Organic Chemistry, Nankai UniVersity, Tianjin 300071, P. R. China ReceiVed May 11, 2005; ReVised Manuscript ReceiVed August 30, 2005

ABSTRACT: In our efforts to design metal complexes with tailored structures, four 3-(2-pyridyl)pyrazole-based ligands, 8-[3-(2pyridyl)pyrazolmethyl]quinoline (L1), 1,4-bis[3-(2-pyridyl)pyrazolyl]-trans-2-butene (L2), 2,3-bis[3-(2-pyridyl)pyrazolmethyl]quinoxaline (L3), and 1,3,5-tri[3-(2-pyridyl)pyrazolmethyl]-2,4,6-trimethylbenzene (L4), have been synthesized and characterized, and their metal complexes with CuII, NiII, CoII, and CdII ions have been prepared and structurally characterized by single-crystal X-ray diffraction. Using L1 to react with CuX2 (X ) Ac-, NO3-, or ClO4-) or Cd(ClO4)2‚6H2O, yielded four mononuclear complexes, [Cu(L1)2(OAc)](OAc)(H2O)6 (1) [triclinic, space group P1h, a ) 10.513(11) Å, b ) 13.875(14) Å, c ) 15.776(16) Å, R ) 70.98(2)°, β ) 83.57(2)°, γ ) 69.665(18)°, Z ) 2], [Cu(L1)2(NO3)](NO3)(H2O)5.5 (2) [monoclinic, space group C2/c, a ) 12.395(3) Å, b ) 26.267(6) Å, c ) 26.362(7) Å, β ) 92.635(5)°, Z ) 8], [Cu(L1)2(H2O)](ClO4)2(H2O)2 (3) [orthorhombic, space group Pbca, a ) 13.326(4) Å, b ) 21.715(6) Å, c ) 26.318(8) Å, Z ) 8], and [Cd(L1)3](ClO4)2(H2O)5/2 (4) [triclinic, space group P1h, a ) 12.485(5) Å, b ) 15.142(6) Å, c ) 15.190(6) Å, R ) 83.104(7)°, β ) 75.796(7)°, γ ) 79.584(7)°, Z ) 2]. The reaction of L2 with Cu(ClO4)2‚6H2O or Co(NO3)2‚6H2O yielded two double helical dinuclear complexes: [Cu2(L2)2(H2O)2](ClO4)4(H2O) (5) [triclinic, space group P1h, a ) 10.791(4) Å, b ) 13.923(7) Å, c ) 19.756(9) Å, R ) 72.297(12)°, β ) 78.201(14)°, γ ) 68.683(13)°, Z ) 2] and [Co(L2)(NO3)(H2O)]2(NO3)2 (6) [orthorhombic, space group Pbcn, a ) 18.170(7) Å, b ) 13.240(5) Å, c ) 19.064(7) Å, Z ) 4]. When L2 was replaced by L3 to react with Cu(ClO4)2‚6H2O or Ni(BF4)2‚6H2O, another mononuclear complex, [Cu(L3)(ClO4)](ClO4) (7) [triclinic, space group P1h, a ) 10.1298(6) Å, b ) 12.3163(6) Å, c ) 12.9485(7) Å, R ) 111.533(2)°, β ) 106.068(2)°, γ ) 99.921(2)°, Z ) 2], and a novel tetranuclear complex, [Ni2(L3)2(H2O)4]2(SO4)2(BF4)4(H2O)8(CH3OH)8 (8) [triclinic, space group P1h, a ) 13.818(8) Å, b ) 16.645(8) Å, c ) 20.937(11) Å, R ) 109.508(10)°, β ) 107.144(9)°, γ ) 90.923(9)°, Z ) 2], were obtained. L4 reacts with Cu(ClO4)2‚6H2O, to yield a novel trinuclear complex, [Cu3(L4)(H2O)9](ClO4)5(OH)(CH3CN)(H2O)4.5 (9) [monoclinic, space group C2/c, a ) 32.067(12) Å, b ) 25.610(9) Å, c ) 17.498(7) Å, β ) 115.187(6)°, Z ) 4]. These results show that the nuclearity of metal complexes may be tuned by ligand modifications, and the nature of ligands, metal ions, counteranions, and solvent molecules play important roles in the formation of such coordination architectures. The emission properties of complexes 7 and 8 have been further studied. Introduction The rational design and synthesis of discrete coordination architectures1 or polymeric coordination networks2 is a rapidly developing field in current coordination and supramolecular chemistry. In recent years, much attention has been focused on the synthetic approach and the structural control of coordination architectures, and great progress has been achieved, especially for those with multidimensional structures. However, the methodologies to use transition metal ions as connecting nodes to hold together organic ligands in predefined patterns within self-assembled oligomeric or polymeric aggregates still remain a great challenge.3 The ultimate aim of supramolecular chemistry is to control the structure of the target product with expected properties and functions. The design of suitable organic ligands favoring structure-specific self-assembly is one of the keys for the construction of discrete coordination architectures. Ward et al. have initially reported many elegant coordination architectures through the use of 3-(2-pyridyl)pyrazole and 3-(2pyridyl)pyrazole-based ligands.4 In our attempts to further design coordination architectures with tailored structures, we further designed four [3-(2-pyridyl)pyrazole]-based ligands by carefully tuning the number of the terminals (3-(2-pyridyl)pyrazole group) and the flexibility of the spacer groups, and a series of novel * Corresponding author. Tel: +86-22-23502809. Fax: +86-22-23502458. E-mail: [email protected].

metal complexes from mononuclear to tetranuclear with these ligands have been obtained. We report herein the synthesis and structures of nine discrete metal complexes with the four ligands, 8-[3-(2-pyridyl)pyrazolmethyl]quinoline (L1), 1,4-bis[3-(2-pyridyl)pyrazolyl]-trans-2-butene (L2), 2,3-bis[3-(2-pyridyl)pyrazolmethyl]quinoxaline (L3), and 1,3,5-tri[3-(2-pyridyl)pyrazolmethyl]-2,4,6-trimethylbenzene (L4) (see Scheme 1). The intermolecular interactions for all these complexes and the emission properties of complexes 7 and 8 have been further studied. Experimental Section Materials and General Methods. All the solvents and reagents for synthesis, including 8-bromomethylquinoline, trans-1,4-dibromobutene, 2,3-dibromomethylquinoxaline, and 1,3,5-tribromo-2,4,6-trimethylbenzene, were commercially available and used as received or prepared by reported procedures. 3-(2-Pyridyl)pyrazole (L) was synthesized by a literature method.5 Elemental analyses were performed on a PerkinElemer 240C analyzer, and IR spectra were measured on a 170SX (Nicolet) spectrometer with KBr pellets. 1H NMR spectra were recorded on a Bruker AC-P500 spectrometer (300 MHz) at 25 °C in CDCl3 with tetramethylsilane as the internal reference. Emission spectra were taken on a Cary Eclipse fluorescence spectrophotometer. Syntheses of Ligands. The four ligands, L1-L4, were prepared by modified literature procedures.4,6 The reactions of 3-(2-pyridyl)pyrazole with 8-bromomethylquinoline, 1,4-dibromobutene, 2,3-dibromoquinoxaline, or 1,3,5-tribromo-2,4,6-trimethylbenzene in benzene, in the

10.1021/cg050210t CCC: $33.50 © 2006 American Chemical Society Published on Web 11/22/2005

100 Crystal Growth & Design, Vol. 6, No. 1, 2006 Scheme 1

presence of NaOH and nBu4NOH, gave the four ligands in good yields, and the products were characterized by 1H NMR, IR, and elemental analysis. For L1, yield: 60%. 1H NMR (300 MHz, CDCl3): δ 6.17 (s, 2H), 6.92-8.98 (m, 12H). IR (KBr, cm-1): 2913w, 2870w, 1593s, 1566m, 1490s, 1459m, 1395m, 1355m, 1223Vs, 1150m,1049s, 876m, 796Vs, 769Vs, 739s. Anal. Calcd for C18H14N4: C, 75.51; H, 4.93; N, 19.57%. Found: C, 75.23; H, 4.78; N, 20.01%. For L2, yield: 60%. 1H NMR (300 MHz, CDCl3): δ 4.88 (d, 4H), 5.93 (t, 2H), 6.87-8.64 (m, 12H). IR (KBr, cm-1): 2970w, 2800w, 1592s, 1488s, 1458s, 1428m, 11403m, 1357m, 1273m, 1127s, 1049s, 970m, 778Vs. Anal. Calcd for C20H18N6: C, 70.16; H, 5.30; N, 24.54%. Found: C, 69.95; H, 5.24; N, 24.81%. For L3, yield: 65%. 1H NMR (300 MHz, CDCl3): δ 5.98 (s, 4H), 6.93-8.56 (m, 16H). IR (KBr, cm-1): 2901w, 2878w, 1591s, 1566m, 1489s, 1458s, 1401m, 1362m, 1231s, 1143w,1049s, 991m, 860m, 759Vs. Anal. Calcd for C26H20N8: C, 70.26; H, 4.54; N, 25.21%. Found: C, 70.08; H, 4.62; N, 25.01%. For L4, yield: 60%. 1H NMR (300 MHz, CDCl3): δ 2.53 (s, 9H), 5.74 (s, 6H), 7.26-8.78 (m, 18H). IR (KBr, cm-1): 2890w, 2790w, 1592s, 1566m, 1487s, 1458s, 1399m, 1277m, 1220Vs, 1049s, 991m, 800m, 759s, 620m. Anal. Calcd for C36H33N9: C, 73.07; H, 5.62; N, 21.30%. Found: C, 72.74; H, 5.54; N, 21.67%. [Cu(L1)2(OAc)](OAc)(H2O)6, 1. A solution of Cu(OAc)2‚2H2O (22 mg, 0.1 mmol) in H2O (2.5 mL) was added to a solution of L1 (58 mg, 0.2 mmol) in CH3OH (2.5 mL) to afford a blue precipitate, which was washed with acetone. Recrystallization of the precipitate from CH3CN/Et2O gave 1 as blue single crystals. Yield: 55%. Anal. Calcd for C40H46CuN8O10: C, 55.71; H, 5.38; N, 12.99%. Found: C, 55.23; H, 5.33; N, 13.45%. IR (KBr, cm-1): 3141w, 1613s, 1578Vs, 1500s, 1443w, 1364s, 1332s, 1244s, 824s, 786s. [Cu(L1)2(NO3)](NO3)(H2O)5.5, 2. The blue single crystals of 2 suitable for X-ray analysis were obtained by a similar method as that described for 1 using Cu(NO3)2‚3H2O to replace Cu(OAc)2‚2H2O. Yield: 48%. Anal. Calcd for C36H39CuN10O11.50: C, 50.32; H, 4.57; N, 16.30%. Found: C, 49.97; H, 4.64; N, 16.62%. IR (KBr pellet,

Zou et al. cm-1): 3139w, 3092w, 1612s, 1500s, 1474Vs, 1435m, 1383Vs, 1276Vs, 1245s, 1051s, 821m, 785Vs. [Cu(L1)2(H2O)](ClO4)2(H2O)2, 3. The same synthetic procedure as that for 2 was used except that Cu(NO3)2‚3H2O was replaced by Cu(ClO4)2‚6H2O, giving blue single crystals in 39% yield. Anal. Calcd for C36H34CuN8O11Cl2: C, 48.63; H, 3.85; N, 12.60%. Found: C, 48.22, H, 3.79; N, 13.01%. IR (KBr, cm-1): 3132w, 1613s, 1503s, 1441s, 1384Vs, 1327s, 1246s, 1099s, 824s, 782s, 623s. [Cd(L1)3](ClO4)2(H2O)5/2, 4. The same synthetic procedure as that for 3 was used except that Cu(ClO4)2‚6H2O was replaced by Cd(ClO4)2‚ 6H2O with a 1:3 metal-to-ligand molar ratio, giving colorless single crystals in 40% yield. Anal. Calcd for C54H47CdN12O10.5Cl2: C, 53.37; H, 3.90; N, 13.83%. Found: C, 53.01; H, 3.83; N, 14.24%. IR (KBr, cm-1): 3136w, 3122w, 2941w, 1609Vs, 1504s, 1438Vs, 1243Vs, 1089m, 824s, 780s, 625s. [Cu2(L2)2(H2O)2](ClO4)4(H2O), 5. The same synthetic procedure as that for 3 was used except that L1 was replaced by L2 with 1:1 metalto-ligand molar ratio, giving blue single crystals in 45% yield. Anal. Calcd for C40H42Cu2N12O19Cl4: C, 38.02; H, 3.35; N, 13.30%. Found: C, 38.42; H, 3.28; N, 13.72%. IR (KBr, cm-1): 3122w, 2426w, 1762w, 1611m, 1569m, 1506m, 1442m, 1384Vs, 1237m, 1161m, 1100m, 959m, 781s. [Co(L2)(NO3)(H2O)]2(NO3)2, 6. The same synthetic procedure as that for 5 was used except that Cu(ClO4)2‚6H2O was replaced by Co(NO3)2‚6H2O, giving pink single crystals in 36% yield. Anal. Calcd for C40H40Co2N16O14: C, 44.21; H, 3.71; N, 20.62%. Found: C, 43.85; H, 3.64; N, 21.01%. IR (KBr, cm-1): 3143w, 2993w, 2930w, 2426w, 1610s, 1456s, 1384Vs, 1237s, 1073m, 1019m, 960m, 778s. [Cu(L3)(ClO4)](ClO4), 7. The same synthetic procedure as that for 5 was used except that L2 was replaced by L3, giving blue single crystals in 34% yield. Anal. Calcd for CuC26H20Cl2N8O8: C, 44.17; H, 2.85; N, 15.85%. Found: C, 44.41; H, 2.72; N, 16.07%. IR (KBr, cm-1): 3074w, 1720s, 1613m, 1443s, 1343m, 1239s, 1095Vs, 775Vs, 622s. [Ni2(L3)2(H2O)4]2(SO4)2(BF4)4(H2O)8(CH3OH)8, 8. The same synthetic procedure as that for 7 was used except that Cu(ClO4)2‚6H2O was replaced by Ni(BF4)2‚6H2O (34 mg, 0.1 mmol) and Na2SO4, giving light-green single crystals in 24% yield. Anal. Calcd for C56H72B2F8N16Ni2O16S: C, 43.44; H, 4.69; N, 14.47%. Found: C, 43.85; H, 4.76; N, 14.81%. IR (KBr, cm-1): 3142w, 1612s, 1571m, 1509w, 1489w, 1442Vs, 1373s, 1296w, 1243m, 1060Vs, 767Vs. [Cu3(L4)(H2O)9](ClO4)5(OH)(CH3CN)(H2O)4.5, 9. The same synthetic procedure as that for 7 was used except that L3 was replaced by L4 with a 1:3 metal-to-ligand molar ratio and a suitable amount of CH3CN was added, giving blue single crystals in 47% yield. Anal. Calcd for C38H64Cu3N10O34.5Cl5: C, 28.87; H, 4.08; N, 8.86%. Found: C, 28.56; H, 3.89; N, 8.61%. IR (KBr, cm-1): 2984w, 2017w, 1646m, 1613m, 1442s, 1332m, 1223w, 1086Vs, 941m, 775s, 636s, 627s. CAUTION! Perchlorate complexes of metal ions in the presence of organic ligands are potentially explosive. These materials should be handled with extreme care in small amounts. X-ray Data Collection and Structure Determinations. X-ray single-crystal diffraction data for complexes 1-9 were collected on a Bruker Smart 1000 CCD diffractometer at 293(2) K with Mo KR radiation (λ ) 0.710 73 Å) by ω scan mode. The program SAINT7 was used for integration of the diffraction profiles. It is worth noting that the quality of the crystals of 2, 5, and 8 are not good enough (attempts for preparing these crystals with good quality were not successful), so the R values are a little high. There are also some atoms of the solvent molecules or counteranions in 2, 4, 5, 8, and 9 refined disorderedly. All the structures were solved by direct methods using the SHELXS program of the SHELXTL package and refined by fullmatrix least-squares methods with SHELXL (semiempirical absorption corrections were applied using SADABS program).8 Metal atoms in each complex were located from the E-maps, and other non-hydrogen atoms were located in successive difference Fourier syntheses and refined with anisotropic thermal parameters on F2. The hydrogen atoms of the ligand were generated theoretically onto the specific atoms and refined isotropically with fixed thermal factors. Further details for structural analysis are summarized in Table 1.

Results and Discussion Description of Crystal Structures. [Cu(L1)2(OAc)](OAc)(H2O)6, 1. The structure of 1 consists of mononuclear [Cu(L1)2-

Complexes with 3-(2-Pyridyl)pyrazole-Based Ligands

Crystal Growth & Design, Vol. 6, No. 1, 2006 101

Table 1. Crystallographic Data and Structure Refinement Summary for Complexes 1-9

chemical formula formula weight space group a, Å b, Å c, Å R, deg β, deg γ, deg V, Å3 Z D, g cm-3 µ, mm-1 T, K Ra/wRb

chemical formula formula weight space group a, Å b, Å c, Å R, deg β, deg γ, deg) V, Å3 Z D, g cm-3 µ, mm-1 T, K Ra/wRb a

1

2

3

4

5

C40H46CuN8O10

C36H39CuN10O11.50

C36H34Cl2CuN8O11

C54H47CdCl2N12O10.50

C40H42Cl4Cu2N12O19

862.39

860.32

889.15

1215.34

1263.74

P1h

c/2c

Pbca

P1h

P1h

10.513(11) 13.875(14) 15.776(16) 70.98(2) 83.57(2) 69.665(18) 2040(4) 2 1.404 0.603 293(2) 0.0801/0.1061

12.395(3) 26.267(6) 26.362(7) 90 92.635(5) 90 8574(4) 8 1.333 0.577 293(2) 0.1122/0.2531

13.326(4) 21.715(6) 26.318(8) 90 90 90 7616(4) 8 1.551 0.786 293(2) 0.0791/0.1541

12.485(5) 15.142(6) 15.190(6) 83.104(7) 75.796(7) 79.584(7) 2729.4(18) 2 1.479 0.569 293(2) 0.0674/0.1376

10.791(4) 13.923(7) 19.756(9) 72.297(12) 78.201(14) 68.683(13 2619(2) 2 1.602 1.100 293(2) 0.1352/0.3250

6

7

8

9

C40H40Co2N16O14

C26H20Cl2CuO8N8

C56H72B2F8N16Ni2O16S

C76H128Cl10Cu6N20O69

1086.74

706.94

1540.33

3165.76

Pbcn

P1h

P1h

C2/c

18.170(7) 13.240(5) 19.064(7) 90 90 90 4586(3) 4 1.574 0.809 293(2) 0.0494/0.0816

10.1298(6) 12.3163(6) 12.9485(7) 111.533(2) 106.068(2) 99.921(2) 1374.57(13) 2 1.708 1.057 293(2) 0.0702/0.1984

13.818(8) 16.645(8) 20.937(11) 109.508(10) 107.144(9) 90.923(9) 4302(4) 2 1.189 0.540 293(2) 0.1125/0.2745

32.067(12) 25.610(9) 17.498(7) 90 115.187(6) 90 13003(8) 4 1.639 1.298 293(2) 0.0875/0.2107

R ) ∑(||Fo| - |Fc||)/∑|Fo|. b wR ) [∑w(|Fo|2 - |Fc|2)2/∑w(Fo2)]1/2.

(OAc)]+ cations, OAc- anions, and H2O molecules. The view of 1 is shown in Figure 1a with uncoordinated OAc- ion and H2O molecules omitted for clarity. The coordination geometry of CuII could be described as a square pyramid with N(4)N(7)-N(8)-O(1) as the basal plane and N(3) atom of L1 on the apical site, and the CuII center deviates from the mean plane defined by N(4)-N(7)-N(8)-O(1) (mean deviation of 0.260 Å) toward N(3) by 0.248 Å. The bond length of Cu(1)-N(3) (2.221(5) Å) is longer than the remaining Cu-N (2.011-2.105 Å range) lengths but all are normal Cu-N coordination bonds (Table 2).9 As shown in Figure 1b, the quinoline group of the ligand can turn freely, to form a suitable space for intramolecular π-π stacking interactions with the pyridyl ring from adjacent L1. The centroid-centroid separations are 3.820 and 3.687 Å, respectively.12,13 Furthermore, the adjacent [Cu(L1)2(OAc)]+ units are arranged into a one-dimensional (1D) chain by a combination of intra- and intermolecular π-π stacking interactions. The quinoline groups are almost parallel to the pyridyl rings from an adjacent [Cu(L1)2(OAc)]+ unit with the centroidcentroid separations falling in the range of 3.411-3.905 Å, indicating the existence of strong intermolecular π-π stacking interactions. In addition, the adjacent 1D chains are further linked to form a three-dimensional network through intermolecular H-bonding interactions. Moreover, the uncoordinated nitrogen atoms of the quinoline groups serve as the O-H‚‚‚N H-bonding acceptors to the aqua molecules. [Cu(L1)2(NO3)](NO3)(H2O)5.5, 2. Similar to 1, the structure of 2 consists of mononuclear [Cu(L1)2(NO3)]+ cations, NO3-

Table 2. Selected Bond Distances (Å) and Angles (deg) for Complex 1 Cu(1)-N(8) Cu(1)-O(1) Cu(1)-N(3)

2.011(4) 2.033(4) 2.221(5)

Cu(1)-N(4) Cu(1)-N(7)

2.016(5) 2.101(5)

N(8)-Cu(1)-N(4) N(4)-Cu(1)-O(1) N(4)-Cu(1)-N(7) N(8)-Cu(1)-N(3) O(1)-Cu(1)-N(3)

177.9(2) 89.83(18) 101.91(19) 99.31(19) 102.17(19)

N(8)-Cu(1)-O(1) N(8)-Cu(1)-N(7) O(1)-Cu(1)-N(7) N(4)-Cu(1)-N(3) N(7)-Cu(1)-N(3)

90.16(19) 79.1(2) 150.47(17) 78.6(2) 106.64(19)

ions, and H2O molecules. As shown in Figure 2a, the coordination geometry around CuII could be described as a distorted octahedron with O(1)-O(2)-N(3)-N(7) as the equatorial plane and N(4) and N(8) atoms from two distinct L1 on the axial sites. The CuII center deviates from the mean plane defined by O(1)O(2)-N(3)-N(7) (mean deviation of 0.179 Å) of ca. 0.0109 Å. The bond lengths of Cu(1)-N(4) (1.997(6) Å) and Cu(1)N(8) (1.981(6) Å) are obviously shorter than those of the Cu(1)-N(3) (2.136(6) Å) and Cu(1)-N(7) (2.154(6) Å),9 which indicates that the octahedral configuration of CuII center is compressed (Table 3). In this complex, the centroid-centroid separations of the pyridyl rings with quinoline rings from adjacent L1 are fall into 3.739-3.894 Å, showing the existence of intramolecular weak π-π stacking interactions. The adjacent [Cu(L1)2(NO3)]+ units are linked together through intermolecular C-H‚‚‚O H-bonding interactions between the coordinated O atoms of NO3- and H-atoms of pyridyl or pyrazole rings (C(15)-H(15A)‚‚‚O(2)i, i ) -x, -y + 1, -z + 2, and (C(30)-H(30A)‚‚‚O(1)j, j ) -x

102 Crystal Growth & Design, Vol. 6, No. 1, 2006

Zou et al.

Figure 1. (a) View of 1 (H atoms, free OAc- ion, and H2O were omitted for clarity); (b) view of the 1D structure of 1 formed by intraor intermolecular π-π stacking.

- 0.5, -y + 0.5, -z + 2) (Figure 2b). The separations of C(15)‚ ‚‚O(2)i and C(30)‚‚‚O(1)j are 3.116 and 3.251 Å with the angles of C(15)-H(15A)‚‚‚O(2)i and C(30)-H(30A)‚‚‚O(1)j of 136.3° and 147.2°, respectively. The uncoordinated NO3- ions further link these discrete [Cu(L1)2(NO3)]+ units to form a 2D network with novel wheel-like ring unit (Figure 2b) through intermolecular H-bonding interactions (Figure 2c). The separations of C(24)‚‚‚O(4), C(29)‚‚‚O(4)k (k ) -x + 0.5, -y + 0.5, -z + 2) and C(28)‚‚‚O(6)k are 3.368, 3.258, and 3.306 Å with the angles of C(24)-H(24A)‚‚‚O(4), C(29)-H(29A)‚‚‚O(4)k, and C(28)-H(28A)‚‚‚O(6)k of 145.4°, 170.1°, and 157.5°, respectively. [Cu(L1)2(H2O)](ClO4)2(H2O)2, 3. Complex 3 is also a mononuclear structure, consisting of discrete [Cu(L1)2(H2O)]2+ ions, ClO4-, and H2O. Its structure is very similar to that of 1 (Figure 3a). The coordination geometry of CuII is a square pyramid with N(4)-N(7)-N(8)-O(1w) as the basal plane, N(3) atom of L1 on the apical site, and the CuII center is located in the square pyramid and deviates from the N(4)-N(7)-N(8)O(1w) mean plane (mean deviation of 0.216 Å) of 0.1818 Å. The bond length of Cu(1)-N(3) (2.250(5) Å) is longer than the remaining Cu-N (2.002(5)-2.064(5) Å region) lengths (Table 4).9 As shown in Figure 3b, the centroid-centroid separations of the pyridyl rings with quinoline rings from adjacent L1 are fall into 3.660-3.781 Å, which shows the existence of stronger intramolecular π-π stacking interactions than those in 1 and 2.12.13 The adjacent [Cu(L1)2(H2O)]2+ units are arranged into 1D chains through intermolecular O-H‚‚‚N H-bonding interactions between the coordinated H2O molecules and N atom of quinoline rings (O(1w)‚‚‚N(5)i, i ) x + 0.5, y, -z + 1.5) (Figure 4b). The separation of O(1w)‚‚‚N(5)i is 2.698 Å. [Cd(L1)3](ClO4)2(H2O)2.5, 4. The view of 4 is shown in Figure 4a, and the coordination geometry around the CdII center

Figure 2. (a) View of 2 (H atoms, uncoordinated NO3- ion, and H2O were omitted for clarity); (b) view of the wheel-like ring unit of 2 formed through intermolecular H-bonding interactions; (c) the 2D H-bonding network of 2.

could be described as a distorted octahedron with N(1)-N(9)N(5)-N(6) as the equatorial plane and N(2) and N(10) atoms of L1 on the axial sites, and the CdII center deviates from the mean plane (mean deviation of 0.108 Å) by 0.117 Å. The bond lengths of Cd-N fall into the normal range.10,11 Similar to 1, 2, and 3, the L1 ligand of 4 still adopts N,Nbidentate chelating coordination mode to form three chelating five-membered cycles. The Cd-N bond distances fall into the normal range for such coordination bonds (Table 5). The uncoordinated quinoline groups participate in the intramolecular



Figure 3. (a) View of 3 (H atoms, free ClO4- ion and H2O were omitted for clarity); (b) view of the 1D structure of 3 formed through intermolecular H-bonding interactions.

Figure 4. (a) View of 4 (H atoms, uncoordinated OAc- ion, and H2O omitted for clarity); (b) view of the quasi-3D network linked by π-π stacking.

Table 3. Selected Bond Distances (Å) and Angles (deg) for Complex 2


Cu(1)-N(8) Cu(1)-N(3) Cu(1)-O(2)

1.981(7) 2.136(7) 2.330(14)

Cu(1)-N(4) Cu(1)-N(7) Cu(1)-O(1)

1.997(8) 2.154(7) 2.386(17)

Cu(1)-N(8) Cu(1)-N(4) Cu(1)-N(3)

2.002(5) 2.005(5) 2.250(5)

Cu(1)-O(1W) Cu(1)-N(7)

2.005(4) 2.064(5)

N(8)-Cu(1)-N(4) N(4)-Cu(1)-N(3) N(4)-Cu(1)-N(7) N(8)-Cu(1)-O(2) N(3)-Cu(1)-O(2) N(8)-Cu(1)-O(1) N(3)-Cu(1)-O(1) O(2)-Cu(1)-O(1)

178.6(3) 79.1(3) 101.2(3) 86.5(4) 109.3(4) 90.2(4) 160.9(4) 55.3(3)

N(8)-Cu(1)-N(3) N(8)-Cu(1)-N(7) N(3)-Cu(1)-N(7) N(4)-Cu(1)-O(2) N(7)-Cu(1)-O(2) N(4)-Cu(1)-O(1) N(7)-Cu(1)-O(1)

100.7(3) 80.1(3) 111.7(2) 92.3(4) 138.5(4) 89.6(4) 85.4(4)

N(8)-Cu(1)-O(1W) O(1W)-Cu(1)-N(4) O(1W)-Cu(1)-N(7) N(8)-Cu(1)-N(3) N(4)-Cu(1)-N(3)

89.12(19) 90.56(18) 154.71(19) 99.7(2) 78.28(19)

N(8)-Cu(1)-N(4) N(8)-Cu(1)-N(7) N(4)-Cu(1)-N(7) O(1W)-Cu(1)-N(3) N(7)-Cu(1)-N(3)

177.9(2) 80.2(2) 100.9(2) 94.61(19) 109.7(2)

π-π stacking interactions with the pyridyl rings from the other ligand with the centroid-centroid separations of 3.726 and 3.821 Å, respectively. As shown in Figure 4b, intermolecular π-π stacking interactions between discrete mononuclear units link the molecules to form a quasi-three-dimensional (3D) network with the ClO4- anions and aqua molecules included in the cavities. The N atom of quinoline ring from L1 does not coordinate to metal ions and only acts as a H-bonding acceptor in 4. [Cu2(L2)2(H2O)2](ClO4)4(H2O), 5. The view of 5 with atom labeling is shown in Figure 5a with ClO4- and H2O omitted

for clarity. The uncoordinated water molecule could easily get away from the complex, so the crystal of 5 is sensitive to air and should be kept in the mother liquid. The coordination geometries around the two CuII centers could be described as triangular dipyramid with N(2)-N(11)-O(1W) and N(5)N(8)-O(2W) as the equatorial planes and the pyridyl N(1), N(12) atoms and N(6), N(7) atoms on the axial sites, respectively. The two CuII centers deviate from their corresponding equatorial planes by 0.0373 and 0.0539 Å, respectively. The Cu-N and Cu-O bond distances fall into the normal ranges of 1.981(10)-2.093(9) and 2.003(10)-2.009(10) Å, respectively (Table 6).9 The conformations of L2 are fine-tuned for the geometrical preference of the square pyramid coordination mode


Zou et al. Table 5. Selected Bond Distances (Å) and Angles (deg) for Complex 4 Cd(1)-N(5) Cd(1)-N(9) Cd(1)-N(6)

2.335(4) 2.347(4) 2.373(4)

Cd(1)-N(10) Cd(1)-N(2) Cd(1)-N(1)

2.347(4) 2.366(4) 2.411(4)

N(5)-Cd(1)-N(10) N(10)-Cd(1)-N(9) N(10)-Cd(1)-N(2) N(5)-Cd(1)-N(6) N(9)-Cd(1)-N(6) N(5)-Cd(1)-N(1) N(9)-Cd(1)-N(1) N(6)-Cd(1)-N(1)

101.10(14) 71.36(15) 150.15(15) 71.17(15) 100.35(15) 93.55(15) 95.30(16) 164.29(14)

N(5)-Cd(1)-N(9) N(5)-Cd(1)-N(2) N(9)-Cd(1)-N(2) N(10)-Cd(1)-N(6) N(2)-Cd(1)-N(6) N(10)-Cd(1)-N(1) N(2)-Cd(1)-N(1)

168.03(14) 99.32(14) 91.28(14) 99.06(14) 108.04(14) 87.16(15) 70.01(15)


Figure 5. (a) View of 5 (H atoms, ClO4- ions, and lattice water molecule were omitted for clarity); (b) space-filling diagram of 5; (c) view of H-bonding interactions between adjacent dimeric units.

of the metal ions. Two L2 ligands wrap around the metal-metal axis to give rise to a double-helical structure (Figure 5b). The butadiene group, which separates the metal-binding units, remains in trans configuration. The ligand-bridged Cu(1)‚‚‚Cu(2) nonbonding distance is 7.160 Å. In addition, the adjacent dimeric units are linked together to form a 1D zigzag chain structure through intermolecular H-bonding interactions between the oxygen atoms of ClO4- and the pyridyl rings or coordinated aqua molecules (Figure 5c). The bond angle of the C(18)-H(18A)‚‚‚O(11)i (i ) -x + 2, -y, z + 1) is 147.8° with the C(18)‚‚‚O(11)i distance of 3.386 Å, and the O(12)‚‚‚O(2w)j (j ) x + 1, y, z) separation is 2.894 Å. [Co(L2)(NO3)(H2O)]2(NO3)2, 6. Similar to 5, 6 is also a double-helical dimer. The asymmetric unit of 6 consists of discrete [Co(L2)(NO3)(H2O)]+ and NO3- ions. The view of 6 is shown in Figure 6a (uncoordinated NO3- ions and all H atoms were omitted for clarity), and the coordination geometries around

Cu(1)-N(1) Cu(1)-O(1) Cu(1)-N(11) Cu(2)-N(6) Cu(2)-N(8)

1.980(10) 2.009(10) 2.138(9) 1.993(9) 2.085(9)

Cu(1)-N(12) Cu(1)-N(2) Cu(2)-N(7) Cu(2)-O(2W) Cu(2)-N(5)

1.984(9) 2.091(10) 1.985(10) 2.000(10) 2.183(10)

N(1)-Cu(1)-N(12) N(12)-Cu(1)-O(1) N(12)-Cu(1)-N(2) N(1)-Cu(1)-N(11) O(1W)-Cu(1)-N(11) N(7)-Cu(2)-N(6) N(6)-Cu(2)-O(2W) N(6)-Cu(2)-N(8) N(7)-Cu(2)-N(5) O(2)-Cu(2)-N(5)

177.6(4) 90.4(4) 101.2(4) 101.2(4) 115.2(5) 176.5(4) 88.9(4) 102.6(4) 101.7(4) 112.2(5)

N(1)-Cu(1)-O(1) N(1)-Cu(1)-N(2) O(1W)-Cu(1)-N(2) N(12)-Cu(1)-N(11) N(2)-Cu(1)-N(11) N(7)-Cu(2)-O(2W) N(7)-Cu(2)-N(8) O(2)-Cu(2)-N(8) N(6)-Cu(2)-N(5) N(8)-Cu(2)-N(5)

87.2(4) 80.5(4) 129.9(5) 79.7(4) 114.8(4) 87.6(4) 80.2(4) 138.7(5) 79.5(4) 108.9(4)

the two CoII centers could be described as distorted octahedrons. The two CoII centers have different coordination environments, and they deviate from their corresponding mean planes (mean deviations of 0.181 and 0.186 Å, respectively) by 0.0511 and 0.0245 Å, respectively. The Co-N and Co-O bond distances fall into the normal ranges of 2.120(3)-2.157(3) and 2.078(2)-2.124(3) Å, respectively (Table 7).9 The conformation of L2 remains trans after coordination. Two L2 wrap around the metal-metal axis to form a double-helical structure (Figure 6b). The ligand-bridged Co(1)‚‚‚Co(2) nonbonding distance is 7.868 Å. The uncoordinated NO3- ion is disordered and refined with half occupation rate. The stacking pattern of 6 is shown in Figure 6c. The adjacent dimer units are further linked to form a 1D chain through intermolecular H-bonding interactions between the O atoms of coordinated nitrate ions and the coordinated H2O molecules from adjacent dimer unit. The O(7)‚‚‚O(1)i (i ) x, y - 1, z) distance is 2.772 Å with the O(7)-H(7A)‚‚‚O(1)i angle of 155.94°. Although 5 and 6 take similar double-helical binuclear structures, their stacking patterns in the crystals are different: 5 forms a linear H-bonding chain, while 6 is a zigzag H-bonding chain, probably due to the difference of the coordination geometries between CuII and CoII and the coordination abilities between NO3- and ClO4-. NO3- participates in the formation of 6 due to its stronger coordination ability, while ClO4- in 5 only acts as counterion. The O coordination in the two complexes may be easily replaced by other bridging ligands with stronger coordinating ability; therefore, they may serve as precursors for larger coordination architectures. [Cu(L3)(ClO4)](ClO4), 7. The view of 7 with atom labeling is shown in Figure 7a, and the coordination geometries around the CuII center could be described as distorted triangular bipyramid with N(3)-N(5)-O(3) as the equatorial plane, and N(2) and N(6) atoms on the axial sites, respectively. The CuII center deviate from the equatorial plane by 0.0142 Å. The Cu-N and Cu-O bond distances are normal for such coordination



Figure 6. (a) View of 6 (H atoms and uncoordinated NO3- ions were omitted for clarity); (b) space-filling diagram of 6; (c) the 1D H-bonding chain in 6. Table 7. Selected Bond Distances (Å) and Angles (deg) for Complex 6a Co(1)-N(2) Co(1)-O(1) Co(1)-N(1)#1 Co(2)-O(1W)#1 Co(2)-N(5)#1 Co(2)-N(6)#1

2.120(3) 2.124(3) 2.145(3) 2.078(2) 2.157(3) 2.138(3)

Co(1)-N(2)#1 Co(1)-O(1)#1 Co(1)-N(1) Co(2)-O(1W) Co(2)-N(5) Co(2)-N(6)

2.120(3) 2.124(3) 2.145(3) 2.078(2) 2.157(3) 2.138(3)

N(2)-Co(1)-N(2)#1 N(2)#1-Co(1)-O(1) N(2)#1-Co(1)-O(1)#1 N(2)-Co(1)-N(1)#1 O(1)-Co(1)-N(1)#1 N(2)-Co(1)-N(1) O(1)-Co(1)-N(1) N(1)#1-Co(1)-N(1) O(1W)#1-Co(2)-N(6)#1 O(1W)#1-Co(2)-N(6) N(6)#1-Co(2)-N(6) O(1W)-Co(2)-N(5)#1 N(6)-Co(2)-N(5)#1 O(1W)-Co(2)-N(5) N(6)-Co(2)-N(5)

93.00(15) 93.19(10) 168.77(11) 105.12(11) 85.42(10) 76.79(11) 92.55(11) 177.31(16) 90.77(11) 92.09(12) 176.10(17) 167.89(11) 100.14(12) 88.71(11) 77.27(12)

N(2)-Co(1)-O(1) N(2)-Co(1)-O(1)#1 O(1)-Co(1)-O(1)#1 N(2)#1-Co(1)-N(1)#1 O(1)#1-Co(1)-N(1)#1 N(2)#1-Co(1)-N(1) O(1)#1-Co(1)-N(1) O(1W)#1-Co(2)-O(1W) O(1W)-Co(2)-N(6)#1 O(1W)-Co(2)-N(6) O(1W)#1-Co(2)-N(5)#1 N(6)#1-Co(2)-N(5)#1 O(1W)#1-Co(2)-N(5) N(6)#1-Co(2)-N(5) N(5)#1-Co(2)-N(5)

168.77(11) 93.19(10) 82.32(14) 76.79(11) 92.55(11) 105.12(11) 85.42(10) 85.63(14) 92.09(12) 90.77(11) 88.71(11) 77.27(12) 167.89(11) 100.14(12) 98.75(16)

a

#1 -x, y, -z + 1/2.

bonds (Table 8).9 Considering the weak interaction between the O(6) atom from uncoordinated ClO4- and Cu(1) atom, the coordination geometry around the CuII center could also be described as distorted octahedron. Furthermore, the adjacent [CuL3(ClO4)]+ units are further linked through intermolecular hydrogen-bonding interactions between the C(11)-H(11A) atoms from the pyrazole ring and

Figure 7. (a) View of 7 (H atoms were omitted for clarity); (b) view of the dimer unit of 7 formed by intermolecular H-bonding and Cu‚‚‚O weak interactions. Table 8. Selected Bond Distances (Å) and Angles (deg) for Complex 7 Cu(1)-N(2) Cu(1)-N(5) Cu(1)-O(3)

1.949(6) 1.999(6) 2.384(5)

Cu(1)-N(6) Cu(1)-N(3)

1.989(6) 2.045(6)

N(2)-Cu(1)-N(6) N(6)-Cu(1)-N(5) N(6)-Cu(1)-N(3) N(2)-Cu(1)-O(3) N(5)-Cu(1)-O(3)

168.5(3) 81.3(2) 106.0(2) 87.1(2) 128.6(2)

N(2)-Cu(1)-N(5) N(2)-Cu(1)-N(3) N(5)-Cu(1)-N(3) N(6)-Cu(1)-O(3) N(3)-Cu(1)-O(3)

100.6(2) 80.1(2) 139.0(2) 83.0(2) 92.4(2)

O(5)i (i ) -x - 1, -y, -z) atom from uncoordinated ClO4ion with the C(11)‚‚‚O(5)i distance of 3.432 Å. As shown in Figure 7b, two adjacent [CuL3(ClO4)]+ units of 7 are bridged by two ClO4- ions to form a dimer through intermolecular Cu‚ ‚‚O and C-H‚‚‚O weak interactions. [Ni2(L3)2(H2O)4]2(SO4)2(BF4)4(H2O)8(CH3OH)8, 8. As shown in Figure 8a, the structure of 8 is a centrosymmetric tetranuclear motif, consisting of discrete [Ni2(L3)2(H2O)4]28+ cations, SO42and BF4- anions, H2O, and CH3OH molecules. The crystal structure of the cationic tetranuclear unit is depicted in Figure 8a with counteranions and solvent molecules omitted for clarity. There are two NiII centers [Ni(1) and Ni(2)] in the asymmetric unit. Each NiII ion is six-coordinated to four nitrogen atoms of two distinct L3 (Ni-N lengths in 2.085(7)-2.120(7) Å range) and two oxygen atoms from two aqua molecules (Ni-O lengths in 2.079(6)-2.084(6) Å range). The cis N/O-Ni-N/O angles


Zou et al. Table 9. Selected Bond Distances (Å) and Angles (deg) for Complex 8

Figure 8. (a) View of 8 (H atoms, anions, and solvent molecules were omitted for clarity); (b) space-filling diagram of 8; (c) view of the quasi2D structure linked by intermolecular π-π weak interactions.

are in the range of 77.5(3)°-97.2(3)°. The selected bond lengths and angles are listed in Table 9. In 8, the L3 ligands adopt tetradentate chelating coordination mode. Each ligand links two adjacent NiII ions to form the tetranuclear macrometallacycle with the dimension of 7.255 ×

Ni(1)-O(2) Ni(1)-N(1) Ni(1)-N(15) Ni(2)-O(3) Ni(2)-N(8) Ni(2)-N(10)

2.081(5) 2.094(7) 2.117(8) 2.079(6) 2.085(7) 2.108(8)

Ni(1)-O(1) Ni(1)-N(16) Ni(1)-N(2) Ni(2)-O(4) Ni(2)-N(9) Ni(2)-N(7)

2.083(6) 2.103(7) 2.120(7) 2.084(6) 2.099(7) 2.117(7)

O(2)-Ni(1)-O(1) O(1)-Ni(1)-N(1) O(1)-Ni(1)-N(16) O(2)-Ni(1)-N(15) N(1)-Ni(1)-N(15) O(2)-Ni(1)-N(2) N(1)-Ni(1)-N(2) N(15)-Ni(1)-N(2) O(3)-Ni(2)-N(8) O(3)-Ni(2)-N(9) N(8)-Ni(2)-N(9) O(4)-Ni(2)-N(10) N(9)-Ni(2)-N(10) O(4)-Ni(2)-N(7) N(9)-Ni(2)-N(7)

90.7(2) 91.1(2) 173.2(3) 88.8(3) 97.2(3) 94.8(3) 79.0(3) 172.8(3) 175.3(3) 92.6(3) 88.4(3) 96.0(3) 78.2(3) 89.8(2) 96.0(3)

O(2)-Ni(1)-N(1) O(2)-Ni(1)-N(16) N(1)-Ni(1)-N(16) O(1)-Ni(1)-N(15) N(16)-Ni(1)-N(15) O(1)-Ni(1)-N(2) N(16)-Ni(1)-N(2) O(3)-Ni(2)-O(4) O(4)-Ni(2)-N(8) O(4)-Ni(2)-N(9) O(3)-Ni(2)-N(10) N(8)-Ni(2)-N(10) O(3)-Ni(2)-N(7) N(8)-Ni(2)-N(7) N(10)-Ni(2)-N(7)

173.5(3) 90.6(3) 88.3(3) 95.8(3) 77.5(3) 90.4(3) 96.1(3) 87.8(2) 91.7(3) 174.2(3) 87.7(3) 97.0(3) 96.7(3) 78.6(3) 172.9(2)

8.931 Å2. Four L3 ligands in 8 take two different conformations. The adjacent ligands with different conformations arrange their terminal 3-(2-pyridyl)pyrazole groups in trans or cis positions, respectively, to meet the metal-ligand coordination requirement. The ligand-bridged Ni‚‚‚Ni nonbonding distances are 7.868 and 7.468 Å, respectively. Eight coordinated aqua molecules extend to the center of the macrometallacycle. The uncoordinated aqua and CH3OH molecules could easily get away from the complex, so the crystal of 8 is sensitive to air and should be kept in the mother liquid. The structures of most of the reported tetranuclear complexes are tetrahedral or quadruple helical motifs. However, in the case of complex 8, the four metal centers are located at the corners of a nearly square-planar rectangle. As shown in Figure 8c, the adjacent tetranuclear units are linked together to form a quasi-3D network through intermolecular π-π stacking and H-bonding interactions with open-channeled framework. The unique quasi-3D open-channeled topology of 8 may be applied in the inclusion of suitable guest molecules. Although complexes 7 and 8 share the same ligand (L3), they take totally different structures, which may be mainly due to the different coordination modes between CuII and NiII. [Cu3(L4)(H2O)9](ClO4)5(OH)(CH3CN)(H2O)4.5, 9. Complex 9 is a discrete trinuclear structure, which consists of [Cu3(L4)(H2O)9]6+ cations, ClO4- and OH- anions, H2O, and CH3CN molecules. The view of 9 with atom labeling is shown in Figure 9. The three CuII ions have similar coordination environments. The coordination geometry around each CuII center could be described as triangular dipyramid formed by two N atoms from L4 and two O atoms from aqua molecules on the equatorial plane and another aqua molecule and pyridyl N atom on the axial sites. The three CuII centers deviate from the equatorial planes toward the corresponding axial O atoms by 0.248, 0.123, and 0.201 Å, respectively. The Cu-N and Cu-O bond distances fall into the normal ranges of 1.960-1.978 and 1.960-1.978 Å, respectively (Table 10). Considering the weak interaction between the O atoms from uncoordinated ClO4- ions and CuII centers (Cu‚‚‚O distances 2.623, 2.551, and 2.653 Å for Cu(1), Cu(2), and Cu(3), respectively), the coordination geometries around the CuII centers could also be described as an octahedron. In this trinuclear complex, the three CuII centers are almost coplanar with the central benzene plane. The inner angles for the triangle composed of the metal centers are 58.23°, 49.76°, and 72.01°, respectively, and the ligand-bridged Cu‚‚‚Cu



Figure 9. View of 9 (H atoms, uncoordinated anions, and solvent molecules were omitted for clarity). Table 10. Selected Bond Distances (Å) and Angles (deg) for Complex 9 Cu(1)-O(1W) Cu(1)-N(9) Cu(1)-O(2W) Cu(2)-O(4W) Cu(2)-N(6) Cu(3)-O(9W) Cu(3)-N(3) Cu(3)-O(8W)

1.973(8) 1.991(9) 2.295(9) 1.978(6) 1.995(7) 1.989(6) 1.993(8) 2.257(7)

Cu(1)-O(3W) Cu(1)-N(8) Cu(2)-O(5W) Cu(2)-N(5) Cu(2)-O(6W) Cu(3)-O(7W) Cu(3)-N(2)

1.975(9) 1.991(7) 1.976(6) 1.988(7) 2.281(8) 1.989(6) 2.016(7)

O(1W)-Cu(1)-O(3W) O(3W)-Cu(1)-N(9) O(3W)-Cu(1)-N(8) O(1W)-Cu(1)-O(2W) N(9)-Cu(1)-O(2W) O(5W)-Cu(2)-O(4W) O(4W)-Cu(2)-N(5) O(4W)-Cu(2)-N(6) O(5W)-Cu(2)-O(6W) N(5)-Cu(2)-O(6W) O(9W)-Cu(3)-O(7W) O(7W)-Cu(3)-N(3) O(7W)-Cu(3)-N(2) O(9W)-Cu(3)-O(8W) N(3)-Cu(3)-O(8W)

89.0(4) 91.3(4) 164.8(4) 86.0(4) 94.7(3) 89.1(3) 96.8(3) 169.8(3) 93.8(3) 94.1(3) 86.5(3) 95.1(3) 170.9(3) 91.9(3) 90.7(3)

O(1W)-Cu(1)-N(9) O(1W)-Cu(1)-N(8) N(9)-Cu(1)-N(8) O(3W)-Cu(1)-O(2W) N(8)-Cu(1)-O(2W) O(5W)-Cu(2)-N(5) O(5W)-Cu(2)-N(6) N(5)-Cu(2)-N(6) O(4W)-Cu(2)-O(6W) N(6)-Cu(2)-O(6W) O(9W)-Cu(3)-N(3) O(9W)-Cu(3)-N(2) N(3)-Cu(3)-N(2) O(7W)-Cu(3)-O(8W) N(2)-Cu(3)-O(8W)

179.2(4) 98.2(3) 81.3(3) 96.0(5) 97.8(4) 170.0(3) 92.1(3) 80.7(3) 92.2(4) 97.8(3) 177.0(3) 97.5(3) 80.6(3) 88.8(3) 99.2(3)

nonbonding distances are 9.849, 10.979, and 12.272 Å, respectively. Complex 9 may serve as a precursor for larger coordination architectures when the coordinated H2O molecules are replaced by other bridging ligands.14-18 Emission Properties. The emission spectra of L3 (10-4 M) upon addition of CuII or NiII ions at room temperature in CH3CN solution (excited at 330 nm) are shown in Figure 10. With these metal ions, L3 displayed fluorescence quenching effects. From the fluorescent titration, the emission intensity of L3 decreased gradually to the completely quenched state upon addition of 0-1 equiv of CuII with respect to L3, while the fluorescent intensity of L3 titrated by NiII ions is not completely quenched upon addition of 0-3 equiv of NiII with respect to L3. This result shows that L3 may be a good sensor for detecting CuII ions.19 Further studies are under way in our lab. In conclusion, four 3-(2-pyridyl)pyrazole-based ligands (L1L4) were synthesized through changing the number of the terminals (3-(2-pyridyl)pyrazolyl group) and the flexibility of spacer groups, and nine discrete metal complexes of CuII, NiII, CoII, and CdII with these ligands have been prepared and characterized. In all these complexes including the reported ones,4 all these ligands adopt terminal N,N-bidentate chelating coordination mode. The monodentate N donor from the pendants (the quinolinyl N atom of L1) or spacer groups (the pyridyl N

Figure 10. Emission spectra of L3 in CH3CN (10-4 M) at room temperature (excited at 330 nm) in the presence of (a) 0-1 equiv of CuII and (b) 0-3 equiv of NiII.

atom of ref 4c) does not coordinate to metal centers. The number of terminals and the flexibility of spacer groups are excellent regulators of the nuclearity and topologies of their metal complexes. In general, the metal ions adjust the topologies of their complexes through coordination geometries. The coordination geometry of the CuII ion usually tends to take five-coordinated tetragonal pyramid or triangular dipyramid, while those of CoII, NiII, and CdII ions tend to six-coordinated octahedron. The structural differences of 5 and 6 and 7 and 8 fully exhibit the influences of the metal centers to their structures. The effect of anions can be explained from their differences in sizes and coordination ability.20,21 OAc- and NO3- participate in the formation of 1, 2, and 6 mainly due to their stronger coordination ability, while the weaker coordinating SO42-, ClO4-, and BF4- ions in 3, 4, 5, 8, and 9 only act as counteranions. It is worth noting that the ClO4- and BF4- ions


act as the template to form a series of multinuclear complexes,6 while the anions presented by us do not act in such roles, which probably are ascribed to the coordinated or lattice water molecules. So the solvent influence is also an important factor to tune the structural topologies and nuclearity of such complexes. It is different from the reported ones,4 especially for the six-coordinated metal complexes (CdII, CoII, and NiII), that the ratio of metal to ligands is 1:1 rather than 2:3, and the remaining coordination sites are occupied by water molecules. These coordinated waters act as H-bonding acceptors and link these discrete entities to form intriguing H-bonding chains or networks. All the complexes except for 3 may serve as precursor for larger coordination architectures when the coordinated water molecules or counteranions are replaced by other bridging ligands. Concluding Remarks In summary, this work illustrates some useful results of ligand design that could be applied in the synthesis of discrete coordination architectures with metal auxiliaries. These results indicate that the changes of the ligand spacers or pendant groups, metal ions, counteranions, and solvent molecules could adjust the framework formation of such complexes. Acknowledgment. This work was financially supported by the National Natural Science Funds for Distinguished Young Scholars of China (Grant No. 20225101) and the National Natural Science Foundation of China (Grant No. 20373028). Supporting Information Available: X-ray crystallographic files in CIF format for complexes 1-9. This material is available free of charge via the Internet at http://pubs.acs.org.

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CG050210T

Syntheses, Structure, and Properties of the Metal Complexes with 3

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