Polynuclear and tetranuclear cuprous iodide complexes derived from N-(2-thienylmethylidene)-2-pyridylamine derivatives

Polyhedron 25 (2006) 1791–1801 www.elsevier.com/locate/poly

Polynuclear and tetranuclear cuprous iodide complexes derived from N-(2-thienylmethylidene)-2-pyridylamine derivatives Chen-Shiang Lee, Chih-Yu Wu, Wen-Shu Hwang *, Joydev Dinda Department of Chemistry, National Dong Hwa University, 1, Section 2, Da-Hsueh Road, Shoufeng, Hualien, Taiwan 974, Taiwan, ROC Received 6 July 2005; accepted 18 November 2005 Available online 18 January 2006

Abstract The reaction of bidentate thienyl Schiff base derivatives, R–Th–C@N–Py (R = H, 3-Me, 5-Me, and 5-Br), with copper(I) iodide under mild conditions in acetonitrile yields (i) two one-dimensional coordination polymer chain complexes with alternating six-membered and four-membered metallocycles, [Cu2(C4H3SCHNC5H4N)(l2-I)(l3-I)]n, (1) and [Cu2(3-Me-C4H2SCHNC5H4N)(l2-I)(l3-I)]n (2), and (ii) two discrete chair-pyramidal shaped tetranuclear complexes, Cu4(5-Me-C4H2SCHNC5H4N)2(l2-I)2(l3-I)2 (3) and Cu4(5-Br– C4H2SCHNC5H4N)2(l2-I)2(l3-I)2 (4). These complexes are characterized spectrally. The molecular structures of 1, 2, 3 and 4 were established in detail by single-crystal X-ray diffraction analysis. The polymer chain structure of 2 is found to be extended into a twodimensional supramolecular network through hydrogen-bonded interactions.  2005 Elsevier Ltd. All rights reserved. Keywords: One-dimensional polymer complex; Two-dimensional polymer complex; Tetranuclear copper(I) complex; N-(2-Thienylmethylidene)-2pyridylamine derivatives

1. Introduction Considerable attention has recently been focused to the study of metal–organic networks due to their fascinating new topologies and intriguing structural features. On the other hand, the intense interest in metal–organic networks is driven to a large extent by their interesting properties and potential in various applications, such as magnetism, catalysis, electrical conductivity and optics, etc. [1]. Covalent bonds and weaker secondary bonding such as hydrogen bonds and p–p stacking interactions are the most widely used tools that assemble transition metal-complexes into metal–organic network. Copper is very suitable to the formation of some novel frameworks because of its readiness to coordinating with unsaturated bidentate nitrogen ligands as a result of the soft–soft bonding performance [2]. The copper(I) halide framework from mononuclear species through dinuclear *

Corresponding author. Tel.: +886 3 8632001; fax: +886 3 8632000. E-mail address: [email protected] (W.-S. Hwang).

0277-5387/$ - see front matter  2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2005.11.033

and tetranuclear discrete molecular moieties to polymeric structures considering monodentate N-donor ligands are previously observed [3]. The less sterically demanding the ligand, the greater the complexity of the copper(I) halide architectures. Complex formation between copper(I) halides and bidentate N-donor ligands that have a bite angle less than 90 has been studied extensively [4]. Recent research in the copper(I) halide coordination chemistry has extended to the role of divergent bridging bidentate ligands that enforce the coordination of more than one metal center. The bidentate bridging N-donor ligands are best classified according to the disposition of their lone pairs, which varies from linear through obtuse and acute to parallel. Apart from the discrete molecular units, rhomboid dimmers, cubane tetramers, and stepped cubane tetramers [4,5], the copper(I) halide frameworks with extended polymeric chains have also been observed [2,6]. In the current contribution, we report novel copper(I)iodide complexes of (i) two one-dimensional coordination polymers, [Cu2(C4H3SCHNC5H4N)(l2-I)(l3-I)]n (1) and [Cu2(3-Me-C4H2SCHNC5H4N)(l2-I)(l3-I)]n (2), and (ii)

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two chair-pyramidal shaped tetramers, Cu4(5-MeC4H2SCHNC5H4N)2(l2-I)2(l3-I)2 (3) and Cu4(5-Br– C4H2SCHNC5H4N)2(l2-I)2(l3-I)2 (4), consisting both l2-iodo and l3-iodo bridging and two nitrogen donors coordination of the bidentate Schiff bases, N-(2-thienylmethylidene)-2-pyridylamine derivatives. The choice of heterocyclic Schiff base stems from our interest in the formation and structures of new dinuclear metal complexes as well as their biological aspects [7]. The molecular structures of the aforementioned complexes have been determined by single-crystal X-ray diffraction. 2. Experimental 2.1. Physical measurements NMR spectra were recorded on a Bruker DX-300 NMR spectrometer (1H, 299.95 MHz; 13C, 75.43 MHz). Chemical shifts were referenced to Me4Si and deuterated acetonitrile (Janssen) was used as a solvent and as a secondary reference. IR spectra were recorded employing a Mattson Genesis FT-IR spectrophotometer. Mass spectra were obtained from a Micromass Platform II spectrometer. Elemental analyses were performed using a Perkin–Elmer 2400, 2400II elemental analyzer. Crystals suitable for X-ray diffraction were obtained from acetone. A single crystal was mounted on a glass fiber and the X-ray diffraction intensity data were measured on a Bruker Smart 1000 CCD XRD. TGA were recorded using METTLER TOLEDO TGA/ SDTA851e. 2.2. Materials 2-Aminopyridine, 2-thiophenecarboxaldehyde, 5-methyl2-thiophenecarboxaldehyde, 3-methyl-2-thiophenecarboxaldehyde (Acros), 5-bromo-2-thiophenecarboxaldehyde (Janssen) and p-toluenesulfonic acid monohydrate (Lancaster) were all distilled by Kugelrohr distillation apparatus under reduced pressure (0.1 mm Hg) prior to use. All other chemicals were of reagent grade and used without further purification. Solvents were dried (sodium/benzophenone, P4O10) and distilled under nitrogen prior to use. 2.3. Preparation of the ligands The syntheses of the Schiff bases have been employed by the usual way of condensation in benzene solution. Equimolar quantities of 2-thiophenecarboxaldehyde, 3methyl-2-thiophenecarboxaldehyde, 5-methyl-2-thiophenecarboxaldehyde or 5-bromo-2-thiophenecarboxaldehyde (10 mmol) and 2-aminopyridine (10 mmol) were refuxed in anhydrous benzene with catalytic amount of p-toluenesulfonic acid monohydrate for 24 h. The reaction mixture was then filtered and the solvent and unreacted starting material were removed in vacuo overnight to obtain pure products, N-(2-thienylmethylidene)-2-pyridylamine (L1) [8,9], N-(5-methyl-2-thienylmethylidene)-2-pyridylamine

N-(3-methyl-2-thienylmethylidene)-2-pyridylamine (L2), (L3) [9] and N-(5-bromo-2-thienylmethylidene)-2-pyridylamine (L4) [10], respectively. L1 (C10H8N2S): Yield 5.8 mmol (58%). 1H NMR (CD3CN) d 9.34 (s, 1H), 8.46 (d, J = 4.8 Hz, 1H), 7.81 (td, J = 7.5, 1.8 Hz, 1H), 7.70 (m, 2H), 7.27 (m, 3H) ppm. 13C NMR (CD3CN,) d 160.2, 155.3, 148.9, 142.5, 138.4, 134.8, 131.6, 128.4, 124.0, 122.1, 119.8 ppm. IR (KBr film) mC@N: 1650 cm1. MS (FAB) m/z 189 (M+H)+. UV (CH3CN) kmax/nm (e/dm3 mol1 cm1): 327 (1.65 · 104), 269 (9.6 · 103), 219 (8.2 · 103). Anal. Calc. for C10H8N2S: C, 63.80; H, 4.28; N, 14.88; S, 17.03%. Found: C, 63.90; H, 4.24; N, 15.03; S, 16.88%. L2 (C11H10N2S): Yield 6.4 mmol (64%). 1H NMR (CD3CN) d 9.38 (s, 1H), 8.45 (d, J = 4.8 Hz, 1H), 7.79 (td, J = 6.8, 1.9 Hz, 1H), 7.56 (d, J = 5.1 Hz, 1H), 7.22 (m, 2H), 6.49 (d, J = 8.2 Hz, 1H), 2.49 (s, 3H) ppm. 13C NMR (CD3CN) d 160.5, 153.9, 148.9, 144.9, 138.3, 136.1, 131.5, 130.8, 121.8, 119.7, 13.4 ppm. IR (KBr film) mC@N: 1603 cm1. MS (FAB) m/z 203 (M+H)+. UV (CH3CN) kmax/nm (e/dm3 mol1 cm1): 358 (9.88 · 104), 329 (1.70 · 105), 281 (1.01 · 105), 226 (7.10 · 104). Anal. Calc. for C11H10N2S: C, 65.32; H, 4.98; N, 13.85; S, 15.85%. Found: C, 65.19; H, 4.96; N, 13.92; S, 15.89%. L3 (C11H10N2S): Yield 6.7 mmol (67%). 1H NMR (CD3CN) d 9.20 (s, 1H), 8.33 (d, J = 5.4 Hz, 1H), 7.70 (td, J = 7.6, 1.8 Hz, 1H), 7.46 (d, J = 3.6 Hz, 1H), 7.12 (m, 2H), 6.83 (dd, J = 2.4, 1.2 Hz), 2.55 (s, 3H) ppm. 13C NMR (CD3CN) d 160.4, 155.2, 147.2, 140.4, 138.4, 135.4, 127.0, 121.8, 119.6, 15.0 ppm. IR (KBr film) mC@N: 1603 cm1. MS (FAB) m/z 203 (M+H)+. UV (CH3CN) kmax/nm (e/dm3 mol1 cm1): 335 (3.6 · 104), 269 (1.4 · 104), 222 (1.3 · 104). Anal. Calc. for C11H10N2S: C, 65.32; H, 4.98; N, 13.85; S, 15.85%. Found: C, 65.08; H, 4.98; N, 13.68; S, 15.91%. L4 (C10H7BrN2S): Yield 5.8 mmol (58%). 1H NMR (CD3CN) d 9.23 (s, 1H), 8.36 (d, J = 4.8 Hz, 1H), 7.75 (td, J = 7.6, 1.9 Hz, 1H), 7.51 (d, J = 3.9 Hz 2H), 7.18 (m, 3H) ppm. 13C NMR (CD3CN) d 159.7, 154.4, 149.0, 144.4, 138.5, 135.0, 131.8, 122.4, 119.9, 118.8 ppm. IR (KBr film) mC@N: 1602 cm1. MS (FAB) m/z 268 (M+H)+. UV (CH3CN) kmax/nm (e/dm3 mol1 cm1): 335 (2.6 · 104), 271 (8.0 · 103), 225 (1.0 · 103). Anal. Calc. for C10H7BrN2S: C, 44.96; H, 2.64; N, 10.49; S, 12.00%. Found: C, 44.96; H, 2.57; N, 10.52; S, 11.95%. 2.4. Preparation of complexes The complex [Cu2I2L1]n (1) was prepared by dissolving copper(I) iodide (1.0 mmol) and L1 (1.0 mmol) in 15 ml anhydrous acetonitrile. After simple filtration and washing with dichloromethane, a reddish orange powder was gained. By mixing with hot acetonitrile, followed by cooling down to 4 C, an oxblood red crystal of complex 1 was formed. Yield 0.39 mmol (78%). 1H NMR (CD3CN) d 9.22 (s, 1H), 8.46 (d, J = 4.8, 1H), 7.81 (td, J = 7.9, 1.7 Hz, 1H), 7.70 (m, 2H), 7.24 (m, 3H) ppm. IR (KBr film)

C.-S. Lee et al. / Polyhedron 25 (2006) 1791–1801

mC@N: 1585 cm1. UV (CH3CN) kmax/nm (e/dm3 mol1 cm1): 327 (2.55 · 104), 244 (4.27 · 104). Anal. Calc. for C10H8Cu2I2N2S: C, 21.10; H, 1.42; N, 4.92; S, 5.63%. Found: C, 21.13; H, 1.17; N, 5.12; S, 5.81%. Complexes [Cu2I2L2]n (2), Cu4I4(L3)2 (3), and Cu4I4(L4)2 (4) were prepared following the similar procedure described in 1 using L2, L3 and L4, respectively. [Cu2I2L2]n (2): Yield 0.41 mmol (82%). 1H NMR (CD3CN) d 9.36 (s, 1H), 8.46 (d, J = 4.8, 1H), 7.81 (t, J = 7.8, 1H), 7.58 (d, J = 5.1, 1H), 7.24 (m, 2H), 7.02 (d, J = 5.1, 1H), 2.50 (s, 3H) ppm. IR (KBr film) mC@N: 1582 cm1. UV (CH3CN) kmax/nm (e/dm3 mol1 cm1): 333 (1.0 · 105), 244 (1.6 · 105). Anal. Calc. for C11H10Cu2I2N2S: C, 22.65; H, 1.73; N, 4.80; S, 5.50%. Found: C, 22.62; H, 1.23; N, 4.72; S, 5.38%.

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Cu4I4(L3)2 (3): Yield 0.28 mmol (56%). 1H NMR (CD3CN) d 9.19 (s, 1H), 8.43 (d, J = 4.8, 1H), 7.88 (t, J = 7.8, 1H), 7.53 (d, J = 3.6, 1H), 7.30 (m, 2H), 6.92 (d, J = 3.6, 1H), 2.54 (s, 3H) ppm. IR (KBr) mC@N: 1579 cm1. UV (CH3CN) kmax/nm (e/dm3 mol1 cm1): 335 (4.1 · 104), 244 (5.6 · 104). Anal. Calc. for C22H20Cu4I4N4S2: C, 22.65; H, 1.73; N, 4.80; S, 5.50%. Found: C, 22.57; H, 1.63; N, 4.72; S, 5.23%. Cu4I4(L4)2 (4): Yield 0.30 mmol (60%). 1H NMR (CD3CN) d 9.23 (s, 1H), 8.46 (d, J = 4.8, 1H), 7.82 (t, J = 7.5, 1H), 7.49 (d, J = 3.9, 1H), 7.25 (m, 3H) ppm. IR (KBr) mC@N: 1581 cm1. UV (CH3CN) kmax/nm (e/ dm3 mol1 cm1): 335 (2.97 · 104), 269 (4.55 · 104). Anal. Calc. for C20H14BrCu4I4N4S2: C, 18.53; H, 1.09; N, 4.32; S, 4.95%. Found: C, 18.56; H, 1.09; N, 4.44; S, 4.95%.

Table 1 Crystal data and refinement parameters for complexes 1, 2, 3, and 4 Compound

1

2

3

4

Formula Formula weight Crystal system Space group ˚) a (A ˚) b (A ˚) c (A a () b () c () ˚ 3) V (A Z Dcalc (g cm3) Cystal size (mm) T (K) Measured data Unique data Number of reflection with [I > 2r(I)] Number of variable h Range () F(0 0 0) R wR

C10H8Cu2I2N2S 569.12 orthorhombic Pbca 8.1021(11) 18.363(2) 19.085(3) 90.00 90.00 90.00 2839.5(7) 8 2.663 0.23 · 0.08 · 0.05 295(2) 17 611 3469 2096 154 2.13–28.30 2096 0.0560 0.0625

C11H10Cu2I2N2S 583.15 orthorhombic Pca21 18.8033(12) 9.5770(6) 8.3063(5) 90.00 90.00 90.00 1495.79(16) 4 2.590 0.20 · 0.03 · 0.03 296(2) 10 717 3644 3242 163 2.13–28.30 1080 0.0280 0.0613

C22H20Cu4I4N4S2 1166.30 monoclinic P21/n 12.6310(4) 8.1980(2) 14.7950(5) 90.00 99.2200(13) 90.00 1512.21(8) 2 2.561 0.30 · 0.20 x 0.06 293(2) 9273 2598 2582 164 4.82–26.03 1080 0.0888 0.2449

C20H14Cu4Br2I4N4S2 1296.09 monoclinic P21/n 12.7233(16) 8.1743(11) 14.7409(19) 90.00 100.142(3) 90.00 1509.2(3) 2 2.676 0.10 · 0.03 · 0.03 296(2) 10 827 3727 2461 163 1.95–28.29 1114 0.0587 0.1936

R1 R2

R2

CuI N

S

N Cu

I

I

N

I

I

N

N

Cu

N Cu

CuI R2

S

S

R1

R1

Cu I

Cu I n

L1 : L2 : L3 : L4 :

R1 = R2 = H R1 = Me; R2 = H R1 = H; R2 = Me R1 = H; R2 = Br

Cu

N N

S R1

1 : R1 = R2 = H 2 : R1 = Me; R2 = H

3 : R1 = H; R2 = Me 4 : R1 = H; R2 = Br

Scheme 1.

R2

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2.5. X-ray data collection and structure refinement

structures were solved by direct methods using the computer program and refined by full-matrix least-square methods on F2 using SHELXL-97 [11]. The unit cell parameters, along with data collection and refinement details, are tabulated in Table 1.

SHELXS-97

An oxblood red crystal of 1 (0.23 · 0.08 · 0.05 mm3), a red crystal of 2 (0.15 · 0.04 · 0.03 mm3), a reddish orange crystal of 3 (0.10 · 0.03 · 0.03 mm3), and a red crystal of 4 (0.2 · 0.03 · 0.03 mm3) were selected for the structural analysis. The intensity data were collected at 295, 296, 292, and 296 K, respectively. All data were collected with x scan technique using graphite monochromatic Mo Ka ˚ ). All non-hydrogen atoms were radiation (k = 0.71073 A refined with anisotropic displacement parameters and hydrogen atoms were refined using a ‘maXus’ model. The

3. Results and discussion 3.1. Ligands and complexes formation and characterization The thienyl Schiff bases L1, L2, L3, and L4 were prepared by condensation of 2-aminopyridine with 2-thiophene-

Fig. 1. Crystal structure of 1 with view of the polymer chain and hydrogen bond illustrated (top) and the staggered arrangement along the crystallographic a-axis (bottom).

C.-S. Lee et al. / Polyhedron 25 (2006) 1791–1801

carboxaldehyde, 3-methyl-2-thiophenecarboxaldehyde, 5-methyl-2-thiophenecarboxaldehyde and 5-bromo-2-thiophenecarboxaldehyde, respectively, in anhydrous benzene. Reactions of ligands L1, L2, L3, and L4 with cuprous iodide in acetonitrile solution gave air-stable complexes 1, 2, 3, and 4, respectively (Scheme 1). Elemental analysis showed all four complexes to have a Cu:L ratio of 2:1. Each pyridyl and thienyl proton in each ligand or complex can be easily assigned from the 1H NMR spectrum according to its specific position, in the region of 6.5– 8.5 ppm, and the characteristic coupling constant(s). Each compound was further characterized by the presence of a singlet azomethine proton at d 9.2–9.4 ppm. The 1H NMR spectra of the four complexes in deuterated acetonitrile show the same pattern as that of their corresponding free ligands with a little upfield or downfield shift for couple resonances as shown in Section 2, suggesting that the coordinated ligands in complexes are well kept in similar geometry as that of the corresponding free ligands. In their IR spectra, all four complexes showed a C@N stretching absorption at 1580 cm1, which is 20 cm1 lower energy shifted relative to that of the free ligands (1600 cm1), and is attributed to the coordination of the azomethine moiety to the cuprous center. 3.1.1. Structure of [Cu2(C4H3SCHNC5H4N)(l2-I)(l3-I)]n (1) Oxblood red crystals of complex 1 suitable for X-ray analysis were obtained from acetonitrile solution. Fig. 1 shows a perspective view of 1 which is found to be an unprecedented polymeric chain that involves alternating zigzag six-membered and four-membered metallocycles. In complex 1, these Cu atoms share corners via l2-I and l3-I to form an extended one-dimensional chain along the a-axis. The relevant interatomic distances and angles

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Table 2 ˚ ) and angles () of complexes 1 and 2 Selected bond lengths (A Compound 1 I1–Cu1 I2–Cu1 Cu2–I1ii Cu2–N2 Cu1–Cu2

2.7120(10) 2.6208(10) 2.5652(10) 1.992(5) 2.8598(12)

N1–Cu1–I2 132.08(15) N1–Cu1–I1 106.12(16) I2–Cu1–I1 103.17(3) N2–Cu2–I2 127.04(15) I2–Cu2–I1ii 116.97(3) Cu2–I2–Cu1 67.16(3) Cu1–I2–Cu1ii 98.80(3) Cu2i–Cu1–Cu2 166.47(5) (i) x  1/2, y, 3/2  z; (ii) 1/2 + x, y, Compound 2 I1–Cu1 Cu2–I1ii I2–Cu1 Cu2–N2 Cu1–Cu2

2.5781(8) 2.6732(7) 2.5698(7) 2.036(4) 2.7956(9)

N1–Cu1–I1 117.05(12) I2–Cu1–I1 113.09(3) N2–Cu2–I2ii 108.60(14) I1ii–Cu2–I2ii 103.24(3) I2–Cu2–I2ii 100.67(2) Cu1–I2–Cu2i 66.62(2) Cu2–I2–Cu2i 102.54(2) Cu2–Cu1–Cu2i 94.37(2) (i) 1/2  x, y, 1/2 + z; (ii) 1/2  x, y,

Cu1–I2i Cu1–N1 I2–Cu2 N2–C6 Cu1–Cu2i N1–Cu1–I2i I1–Cu1–I2i I2–Cu1–I2i N2–Cu2–I1ii Cu2i–I1–Cu1 Cu2–I2–Cu1ii Cu1ii–Cu2–Cu1

2.7541(11) 2.032(5) 2.5482(10) 1.302(8) 2.7686(12) 109.39(15) 105.78(3) 97.83(3) 115.87(15) 63.21(3) 62.81(3) 92.97(3)

3/2  z

I2–Cu2 Cu2–I2ii Cu1–N1 N1–C5 Cu1–Cu2i N1–Cu1–I2 N2–Cu2–I1ii N2–Cu2–I2 I2–Cu2–I1ii Cu1–I1–Cu2i Cu1–I2–Cu2 Cu1–Cu2–Cu1ii

2.6052(8) 2.8046(9) 2.003(4) 1.301(6) 2.9580(10) 129.52(13) 105.59(11) 127.65(13) 108.66(3) 68.54(2) 65.39(2) 155.15(3)

z  1/2

are summarized in Table 2. In the asymmetric unit (Fig. 2), it is clearly shown that each Schiff base acts as a bidentate ligand and bridges two independent copper centers via its two N donor sites. The Cu1 atom in the distorted tetrahedral site is coordinated to one l2-bridging

Fig. 2. ORTEP diagram of 1 with labeling and displacement ellipsoids drawn at the 30% probability level.

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Table 3 Inter- and intramolecular hydrogen bonding in complexes 1 and 2 D–H  A 1a 2a 2a 2b c a b c

C5–H5  I(l2) C10–H10  I(l2) C5–H5  I(l2) C7–H7  I(l2) C–H  Br Intramolecular. Intermolecular. Ref. [19].

d(D–H) ˚) (A

d(H  A) ˚) (A

d(D  A) ˚) (A

\(DHA) ()

0.93

3.112 3.045 3.134 3.084 3.03

3.792(8) 3.699(6) 3.833(6) 3.921(6) 3.710

131.42(42) 128.78(35) 133.50(35) 150.53(35) 131.1

iodide (I1), two l3-bridging iodide (I2 and I2i), and one pyridyl nitrogen atom, N1, of the thienyl Schiff base. The distorted Td bond angles about the Cu center ranging from 97.84(3) to 132.09(16). They compare well with previously reported N–Cu–I and I–Cu–I bond angles [12]. The Cu2 atom with a trigonal planar geometry is coordinated to the azomethine nitrogen, N2, one l3-bridging iodide, and one l2-bridging iodide. The I2–Cu2–I1ii, N2–Cu2– I1ii, I2–Cu2–N2 bond angles are 116.97(3), 115.87(15) and 127.04(15), respectively. The Cu1–N1 and Cu2–N2 ˚ are typical for bond distances of 2.032(5) and 1.992(5) A

Fig. 3. Crystal structure of 2 with view of the polymer chain and hydrogen bonds illustrated (top) and the staggered arrangement along the crystallographic c-axis (bottom).

C.-S. Lee et al. / Polyhedron 25 (2006) 1791–1801

copper(I) complexes. In comparison with distances in similar complexes, these values are basically in agreement with ˚ in [(Ph3P)2Cu2(l-Cl)22.044(3), 1.993(8) and 1.97(2) A (l-pyz)]n, [Cu(l-Cl)(py)] and [Cu(TTA)(4,4 0 -bpy)]n [TTA = 4-(3-thienyl)-1,1,1-triflurobutane-2,4-dionate], respectively [13]. The I1 atom is non-equally shared to Cu1 and Cu2 ˚, centers at a distance of 2.7120(10) and 2.5652(10) A respectively. Again, the I2 atom is also found to be nonequally shared to Cu1, Cu2, and Cu1ii atoms at a distance ˚ , respectively. of 2.6208(10), 2.5482(10), and 2.7540(11) A All these Cu–I distances are comparable to the previously ˚ reported Cu–I distances of 2.6853(9) and 2.7540(10) A ˚ [14]. The Cu1  Cu2i distance of 2.7686(12) A is slightly shorter than the sum of the van der Walls radius of two ˚ ). It is known that Cu1  Cu1 interaction copper(I) (2.8 A is possible with such distance [15]. The Cu  Cu distance in complex 1 is significantly shorter than those in the ˚) reported polymers [(Ph3P)2Cu2(l-Cl)2(l-pyz)]n (3.095(1) A ˚ (pyz = pyrazine), [Cu2(l-Cl)2(l-phz)]n (3.258(1) A) (phz = ˚ ) but phenanzine), and [Cu2(l-Br)2(l-phz)]n (3.391(2) A ˚ ) and longer than that in [Cu2(l-I)2(l-phz)]n (2.525(1) A ˚ ), respectively [16]. The tor[Cu(l-I)(NCR)]n (2.54–2.66 A sion angle between the pyridine ring and Cu1, N1, C1 and N2 plane is 7.31 and that between the pyridine ring and the thienylmethylidene plane is 40.29. The thienyl ring system and the azomethine skeleton make a torsion angle of 6.4. The sulfur atom of the thienyl moiety is in the prox˚, imity of the copper ion center, the Cu–S distance, 2.960 A is at best comparable with previously reported complexes, ˚ for [(Cu{5-Me–Th– e.g., 2.895(2) and 2.985(2) A 2-CH@N-i-Pr}2)(O3SCF3)] [17], thus indicating weak interactions. Both l2- and l3-iodo bridging built a zigzag line structure. The repeating units employ a chemically identical moiety of the asymmetric copper unit which forms an infinite polymer after self-assembly (Fig. 1). The specific construction is rather than the well known nominal motifs, but generates a new type ‘spinning and weaving machinelike’ polymer. The molecule runs along the a-axis as a one-dimensional polymer in which the asymmetric unit is stacked together in a zigzag mode by weak metal–metal interactions. The structure is further stabilized by intramolecular hydrogen bonding between the l2-iodo atoms and the 6-pyridyl hydrogen atoms, shown in Fig. 2. The relevant data are tabulated in Table 3. 3.1.2. Structure of [Cu2(3-Me-C4H2SCHNC5H4N)(l2-I)(l3-I)]n (2) Red crystals of 2 suitable for X-ray analysis were obtained from acetonitrile solution. Fig. 3 shows a perspective view of 2 which is found to be a polymeric chain that involves alternating zigzag six-membered and four-membered metallocycles. X-ray diffraction study indicates that the structure and bonding feature of 2, as shown in Figs. 3 and 4 and Table 2, closely resembles that of 1, as demonstrated above. The distance between a l2-I atom and Cu in 2 is shorter and more reasonable in comparison with that in 1, shows stronger bridging-mode of l2-I. The thienyl Schiff

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Fig. 4. ORTEP diagram of 2 with labeling and displacement ellipsoids drawn at the 30% probability level.

base acts as a bridging ligand and bridges two Cu centers, makes a torsion angle of 18.05 in Cu2–N2–C6–N1 and a torsion angle of 151.99 in C5–N1–C6–N2. The thiophene ring system and the azomethine skeleton make a little torsion of 1.55, it is almost planar. The Cu–S distance ˚ ) is quite less in comparison with 1 (2.960 A ˚ ). (2.903 A The repeating units employ a chemically identical moiety of the asymmetric copper unit which forms a polymer chain after self-assembly (Fig. 3). The molecule runs along the c-axis as a one-dimensional chain, stacked together in a zigzag mode by weak metal–metal interactions to generate a new type of polymer as 1. Both intra- and intermolecular hydrogen bonding were found in 2, as shown in Fig. 5 and Table 3. The linear chains are composed of both intra- and intermolecular hydrogen bonding, formed between the l2iodo atoms with the pyridyl hydrogen and azomethine hydrogen atoms. In comparison with 1, the formation of the hydrogen-bonded interaction in 2 is quite different. While the 6-pyridyl hydrogen and the azomethine hydrogen atoms form weak interaction with the l2-I atoms of its own chain, the 3-pyridyl hydrogen atoms of one polymer chain link with the l2-iodo atoms of the neighboring chain, extending the one-dimensional polymer to a twodimensional supramolecular network. 3.1.3. Structure of Cu4(5-Me-C4H2SCHNC5H4N)2(l2-I)2(l3-I)2 (3) An ORTEP diagram of complex 3 is shown in Fig. 6. The relevant interatomic distances and bond angles are summarized in Table 4. In the asymmetric unit, a crystallographically imposed center of inversion lies between the four copper atoms. The isolated Cu4 rhombohedron is

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Fig. 5. 2-Dimensional network of 2 with hydrogen bonds illustrated.

Fig. 6. ORTEP diagram of 3 with labeling and displacement ellipsoids drawn at the 30% probability level.

planar with Cu  Cu separation distance of 2.690(2)– ˚ , which suggests that there is a weak metal–metal 2.779(4) A bonding character, comparable to the previous structures [16]. Each unit of thienyl derivative acts as a U-shaped component and coordinates, through the pyridyl nitrogen and azomethine nitrogen donors, to two copper centers and the whole molecule displays a chair-pyramidal shape.

Cu2 atom has an approximately tetrahedral geometry, being coordinated by a pyridyl nitrogen atom with a ˚ , two l3-bridging iodide Cu2–N2 distance of 2.032(11) A with Cu2–I2 and Cu2–I2i distances of 2.599(2) and ˚ , and one l2-bridging iodide with Cu2–I1i dis2.968(2) A ˚ . Cu1 atom is coordinated to one l2tance of 2.690(2) A ˚ , one l3-iodide iodide with Cu1–I1 distance of 2.5163(18) A

C.-S. Lee et al. / Polyhedron 25 (2006) 1791–1801 Table 4 ˚ ) and angles () of complexes 3 and 4 Selected bond lengths (A Compound 3 I1–Cu1 Cu1–N1 Cu2–I1i Cu2–N2 Cu1–Cu2 Cu2–Cu2i N1–Cu1–I1 I1i–Cu2–I2i N2–Cu2–I1i I2–Cu2–I1i I1–Cu1–I2 Cu1–I1–Cu2i Cu2–I2–Cu1 (i) x, 1  y, z Compound 4 I1–Cu1 Cu1–N1 Cu2–I2i Cu2–N2 Cu1–Cu2 Cu2–Cu2i N1–Cu1–I1 I1–Cu1–I2 N2–Cu2–I2 I2–Cu2–I1i I2–Cu2–I2i Cu2–I2–Cu1 Cu1–I2–Cu2i Cu2–Cu1–Cu2i (i) 1  x, 1  y,

2.5163(18) 1.969(10) 2.690(2) 2.032(11) 2.690(2) 2.779(4) 137.3(3) 96.63(6) 112.2(3) 106.07(7) 111.00(6) 62.59(6) 62.11(6)

2.507(1) 1.981(1) 2.944(2) 2.028(1) 2.682(2) 2.787(4) 137.7(3) 110.92(7) 123.7(3) 105.22(7) 120.07(7) 61.78(6) 57.64(5) 62.42(8) 1z

I2–Cu1 I2–Cu2 Cu2–I2i C5–N1 Cu1–Cu2i N1–Cu1–I2 N2–Cu2–I2 I2–Cu2–I2i Cu1–I2–Cu2i Cu2–I2–Cu2i Cu1–Cu2–Cu1i Cu1–Cu2–Cu2i

I2–Cu1 Cu2–I1i I2–Cu2 N1–C5 Cu1–Cu2i N1–Cu1–I2 N2–Cu2–I1i N2–Cu2–I2i I1i–Cu2–I2i Cu1–I1–Cu2i Cu2–I2–Cu2i Cu1–Cu2–Cu1i

2.6157(19) 2.599(2) 2.968(2) 1.303(16) 2.709(2) 111.4(3) 123.8(3) 120.56(7) 57.62(5) 59.44(7) 118.05(8) 59.35(7)

2.618(2) 2.681(1) 2.605(2) 1.308(17) 2.696(2) 110.9(3) 12.6(3) 95.2(3) 97.19(6) 62.51(6) 59.93(7) 117.58(8)

˚ , and the azomethine with Cu1–I2 distance of 2.6157(19) A N-atom of the same thienyl derivative with Cu1–N1 dis˚ , and has an approximately trigonal tance of 1.969(10) A

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planar geometry. Two l3-bridging iodide, I2 and I2i, lie below and above the Cu4 plane separately, triply bridged to three copper atoms on the two trigonal copper planes, (Cu1, Cu2, Cu2i) and (Cu2, Cu2i, Cu1i), respectively, to form two trigonal pyramids in opposite direction. 3.2. Structure of Cu4(5-Br–C4H2SCHNC5H4N)2(l2-I)2(l3-I)2 (4) An ORTEP diagram of complex 4 is shown in Fig. 7. The relevant interatomic distances and bond angles are summarized in Table 4. X-ray diffraction study indicates that the structure and bonding feature of 4 closely resembles that of 3. Cu  Cu separation distance of 2.682– ˚ suggests that there is a weak metal–metal bonding 2.787 A character closely related to 3. 3.3. Thermal analysis The thermo gravimetric analysis (10 C min1, 30– 600 C, 40 ml min1 flowing N2) has proved to be a very effective tool for confirming the stoichiometry of CuI–L (L = thienyl Schiff base derivative) complexes. The thermal analysis data for both 1 and 2 show a two-step weight loss corresponding to a loss of the thienyl derivative at first. For complex 1, this occurs at 233 C with a loss of 33.10% (calculated to 33.04%), followed by almost complete loss of the remaining mass with a broad decomposition around 565 C. For complex 2, the thienyl Schiff base loss was at 236 C (observed 34.34%; calculated 34.65%) with a broad decomposition at 560 C. The first step is consistent to the release of the thienyl derivative and the second step involves the loss of remaining metal halide [18]. The thermal analysis

Fig. 7. Crystal structure of 4 with labeling and displacement ellipsoids drawn at the 30% probability level.

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data for 3 and 4 show a one-step mass loss at 235 C for 3 and at 225 C for 4, attributing only to a loss of the thienyl Schiff base. 4. Conclusion The ligands chosen for this study are four thienyl Schiff base derivatives with different substituents on the 3- or 5position of the thienyl ring. Reaction of plain thienyl Schiff base N-(2-thienylmethylidene)-2-pyridylamine, L1, with copper(I) iodide gives complex 1, which contains an unprecedented polymeric chain. Reaction of 3-methyl-thienyl Schiff base L2 with copper(I) iodide gives complex 2, which also contains an unprecedented polymeric chain as 1. However, the crystal structure of 2 is found to be extended into a two-dimensional supramolecular network through hydrogen-bonded interactions. Reactions of 5methyl-thienyl Schiff base L3 and 5-bromo-thienyl Schiff base L3 with copper(I) iodide give complexes 3 and 4, respectively, which are found to be a discrete tetranuclear structure. Obviously, relative to the structure of 1, the methyl substituent on the b-position of the thienyl ring does not cause stereo problem to the self-assembly of the asymmetric copper unit. However, no matter with the electron donating methyl or electron withdrawing bromo substituent on the a 0 -position of the thienyl ring, the steric hindrance of the substituent might play an important role to limit the complex to a tetranuclear structure.

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