catena-Poly[[bis­(1H-benzimidazole-κN³)cobalt(II)]-μ-terephthalato-κ³O¹,O^1′:O⁴]

In the title compound, [Co(C₈H₄O₄)(C₇H₆N₂)₂]_n, the terephthalate dianions bridge Co^II ions through terminal carboxyl groups to form polymeric complex chains; one carboxyl group coordinates in a monodentate manner and the other chelates to the Co atom. Two benzimidazole ligands also coordinate to the Co atom to complete a distorted trigonal–bipyramidal coordination geometry. The crystal packing is stabilized by N—H...O hydrogen bonds and π–π stacking involving the benzimidazole ligands, with a face-to-face separation of 3.454 (11) Å.

Key indicators

• Single-crystal X-ray study
• T = 295 K
• Mean [sigma](C-C)= 0.006 Å
• R factor = 0.048
• wR factor = 0.131
• Data-to-parameter ratio = 12.6

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S1. Comment

π–π Stacking interactions between aromatic rings have attracted much attention because they are correlated with the electron transfer process in some biological systems (Deisenhofer & Michel, 1989). As part of our ongoing investigations of the nature of π–π stacking (Pan & Xu, 2004, 2005), the title polymeric Co^II complex, (I), incorporating terephthalate (tp) dianions and benzimidazole (bzim) ligands, has been prepared and its crystal structure is presented here.

A segment of the polymeric structure of (I) is illustrated in Fig. 1. The Co^II ion is coordinated by two tp dianions and two bzim molecules. Each terephthalate bridges two neighboring Co^II atoms to form a polymeric chain (Fig. 2).

The Co—O2 distance of 2.515 (3) Å is much longer than the Co–O1 and Co–O3 distances (Table 1), but is probably reasonable for a strained bidentate system. The Co—O1—C1 angle of 102.2 (2)° appears to be compressed to allow Co and O2 to approach each other. The other tp carboxylate group has a more typical Co—O3ⁱ—C8ⁱ angle of 110.4 (2)° and a much longer Co–O4ⁱ bond distance of 2.789 (3) Å, indicating that there is no bonding between Co and O4ⁱ [symmetry code: (i) 1/2 + x, 1/2 − y, 1/2 + z]. This is consistent with the situation found in related Mn^II (Liu et al., 2005) and Cu^II complexes (Li et al., 2005).

Thus in (I) the two tp carboxyl groups coordinate to the Co atom differently, one in a monodentate mode and the other in a chelating mode. The coordination geometry around the Co atom can be described as distorted trigonal–bipyramidal, with atoms O2 and O3 in the apical sites. The uncoordinated carboxyl O4 atom accepts an N—H···O hydrogen bond from a bzim ligand of a neighboring chain (Table 2).

A partially overlapped arrangement of bzim rings from neighboring polymeric chains is observed in (I) (Fig. 2). The face-to-face separation between neighboring parallel bzim rings, related by an inversion center at (1/2, 1, 1/2), is 3.454 (11) Å, strongly suggesting the existence of π–π stacking.

S2. Experimental

An aqueous solution (5 ml) containing CoCl₂·6H₂O (0.24 g, 1 mmol), NaOH (0.08 g, 2 mmol) and terephthalic acid (0.17 g, 1 mmol) was mixed with an ethanol solution (15 ml) of bzim (0.24 g, 2 mmol). The mixture was refluxed for 5 h. After cooling to room temperature, the solution was filtered. Red single crystals of (I) were obtained from the filtrate after two weeks.

S3. Refinement

H atoms were placed in calculated positions, with C—H = 0.93 Å and N—H = 0.86 Å, and were included in the final cycles of refinement as riding, with U_iso(H) = 1.2U_eq(carrier).

Computing details

Data collection: PROCESS-AUTO (Rigaku, 1998); cell refinement: PROCESS-AUTO; data reduction: CrystalStructure (Rigaku, 2002); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and XP (Siemens, 1994); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. The molecular structure of (I), shown with 30% probability displacement ellipsoids for the non-H atoms [symmetry code: (i) 1/2 + x, 1/2 − y, 1/2 + z].
	Fig. 2. Packing diagram for (I), showing the π–π stacking.

catena-Poly[[bis(1H-benzimidazole-κN³)cobalt(II)]- µ-terephthalato-κ³O¹,O^1':O⁴]

Crystal data

[Co(C8H4O4)(C7H6N2)2]	F(000) = 940
Mr = 459.32	Dx = 1.498 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 7787 reflections
a = 17.319 (2) Å	θ = 2.6–24.0°
b = 7.2711 (7) Å	µ = 0.88 mm^−1
c = 17.8495 (18) Å	T = 295 K
β = 115.002 (3)°	Plate, red
V = 2037.1 (4) Å^3	0.30 × 0.21 × 0.08 mm
Z = 4

Data collection

Rigaku R-AXIS RAPID diffractometer	3527 independent reflections
Radiation source: fine-focus sealed tube	2730 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.057
Detector resolution: 10.00 pixels mm^-1	θmax = 25.0°, θmin = 1.4°
ω scans	h = −20→20
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	k = −8→8
Tmin = 0.762, Tmax = 0.925	l = −21→21
10571 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.048	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.131	H-atom parameters constrained
S = 1.01	w = 1/[σ^2(Fo^2) + (0.0744P)^2 + 0.8857P] where P = (Fo^2 + 2Fc^2)/3
3527 reflections	(Δ/σ)max = 0.001
280 parameters	Δρmax = 0.45 e Å^−3
0 restraints	Δρmin = −0.48 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Co	0.38836 (3)	0.61572 (6)	0.63020 (3)	0.04267 (18)
N11	0.42478 (19)	1.1337 (4)	0.55315 (18)	0.0544 (8)
H11	0.4023	1.2336	0.5274	0.065*
N13	0.43354 (17)	0.8542 (4)	0.60434 (16)	0.0475 (7)
N21	0.22068 (19)	0.7160 (5)	0.7406 (2)	0.0635 (9)
H21	0.1700	0.7311	0.7370	0.076*
N23	0.32509 (18)	0.6723 (4)	0.70136 (17)	0.0497 (7)
O1	0.33212 (14)	0.4601 (3)	0.52735 (14)	0.0527 (6)
O2	0.24824 (16)	0.6933 (4)	0.51220 (16)	0.0621 (7)
O3	−0.00313 (14)	0.0102 (3)	0.20339 (13)	0.0478 (6)
O4	−0.09195 (14)	0.2193 (4)	0.21237 (14)	0.0552 (6)
C1	0.2618 (2)	0.5412 (5)	0.4894 (2)	0.0479 (8)
C2	0.1917 (2)	0.4450 (5)	0.41883 (19)	0.0449 (8)
C3	0.2028 (2)	0.2706 (5)	0.3934 (2)	0.0536 (9)
H3	0.2560	0.2145	0.4175	0.064*
C4	0.1353 (2)	0.1794 (5)	0.3325 (2)	0.0522 (9)
H4	0.1440	0.0634	0.3155	0.063*
C5	0.0556 (2)	0.2577 (5)	0.29686 (19)	0.0430 (8)
C6	0.0450 (2)	0.4338 (5)	0.3215 (2)	0.0554 (9)
H6	−0.0081	0.4902	0.2971	0.066*
C7	0.1121 (2)	0.5253 (5)	0.3817 (2)	0.0557 (9)
H7	0.1038	0.6428	0.3975	0.067*
C8	−0.0188 (2)	0.1566 (5)	0.23302 (19)	0.0444 (8)
C12	0.3833 (2)	0.9888 (5)	0.5628 (2)	0.0523 (9)
H12	0.3242	0.9833	0.5421	0.063*
C14	0.5954 (2)	0.8387 (6)	0.6702 (2)	0.0574 (10)
H14	0.6004	0.7213	0.6925	0.069*
C15	0.6662 (3)	0.9416 (7)	0.6814 (3)	0.0707 (12)
H15	0.7199	0.8923	0.7122	0.085*
C16	0.6599 (3)	1.1179 (6)	0.6478 (3)	0.0699 (12)
H16	0.7094	1.1823	0.6565	0.084*
C17	0.5821 (3)	1.1977 (6)	0.6022 (2)	0.0640 (10)
H17	0.5775	1.3145	0.5794	0.077*
C18	0.5105 (2)	1.0947 (5)	0.5920 (2)	0.0490 (9)
C19	0.5157 (2)	0.9182 (5)	0.6239 (2)	0.0467 (8)
C22	0.2424 (2)	0.6977 (6)	0.6778 (3)	0.0600 (10)
H22	0.2033	0.7023	0.6226	0.072*
C24	0.4436 (2)	0.6624 (5)	0.8463 (2)	0.0552 (9)
H24	0.4881	0.6435	0.8311	0.066*
C25	0.4576 (3)	0.6769 (7)	0.9278 (3)	0.0737 (12)
H25	0.5131	0.6677	0.9685	0.088*
C26	0.3917 (3)	0.7048 (7)	0.9515 (3)	0.0816 (13)
H26	0.4044	0.7134	1.0075	0.098*
C27	0.3087 (3)	0.7201 (6)	0.8949 (3)	0.0704 (11)
H27	0.2645	0.7387	0.9107	0.084*
C28	0.2943 (2)	0.7063 (5)	0.8123 (2)	0.0552 (9)
C29	0.3596 (2)	0.6774 (5)	0.7875 (2)	0.0482 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Co	0.0330 (3)	0.0472 (3)	0.0383 (3)	0.00341 (19)	0.00586 (19)	−0.0011 (2)
N11	0.0585 (19)	0.0447 (17)	0.0479 (16)	0.0058 (14)	0.0106 (15)	0.0026 (14)
N13	0.0410 (16)	0.0528 (18)	0.0397 (14)	0.0035 (13)	0.0081 (13)	0.0027 (13)
N21	0.0424 (17)	0.080 (2)	0.070 (2)	0.0061 (16)	0.0257 (16)	−0.0079 (18)
N23	0.0389 (15)	0.0602 (18)	0.0449 (15)	0.0052 (14)	0.0129 (13)	−0.0021 (14)
O1	0.0417 (13)	0.0549 (14)	0.0440 (13)	0.0014 (12)	0.0012 (11)	−0.0069 (11)
O2	0.0479 (14)	0.0600 (16)	0.0615 (16)	−0.0013 (13)	0.0068 (13)	−0.0175 (14)
O3	0.0385 (12)	0.0490 (14)	0.0440 (13)	−0.0029 (10)	0.0059 (10)	−0.0072 (11)
O4	0.0338 (12)	0.0720 (17)	0.0517 (13)	0.0021 (12)	0.0101 (11)	−0.0039 (13)
C1	0.046 (2)	0.047 (2)	0.0413 (18)	0.0005 (16)	0.0099 (16)	0.0003 (16)
C2	0.0402 (18)	0.0469 (19)	0.0390 (17)	0.0009 (15)	0.0085 (15)	0.0013 (15)
C3	0.0360 (18)	0.058 (2)	0.052 (2)	0.0102 (16)	0.0037 (16)	−0.0090 (17)
C4	0.0415 (19)	0.052 (2)	0.052 (2)	0.0055 (16)	0.0098 (16)	−0.0091 (17)
C5	0.0386 (17)	0.0478 (19)	0.0369 (16)	0.0005 (15)	0.0105 (14)	−0.0015 (14)
C6	0.0390 (18)	0.059 (2)	0.050 (2)	0.0110 (17)	0.0015 (16)	0.0003 (18)
C7	0.048 (2)	0.049 (2)	0.051 (2)	0.0099 (17)	0.0019 (17)	−0.0071 (17)
C8	0.0364 (18)	0.057 (2)	0.0355 (16)	−0.0011 (15)	0.0108 (14)	0.0036 (15)
C12	0.0444 (19)	0.049 (2)	0.050 (2)	0.0060 (17)	0.0075 (16)	0.0010 (17)
C14	0.044 (2)	0.071 (3)	0.054 (2)	0.0061 (18)	0.0163 (17)	0.0090 (19)
C15	0.049 (2)	0.094 (3)	0.065 (3)	0.002 (2)	0.020 (2)	0.002 (2)
C16	0.058 (3)	0.087 (3)	0.066 (3)	−0.021 (2)	0.027 (2)	−0.013 (2)
C17	0.076 (3)	0.059 (2)	0.061 (2)	−0.012 (2)	0.031 (2)	−0.009 (2)
C18	0.054 (2)	0.048 (2)	0.0422 (18)	0.0009 (17)	0.0177 (16)	−0.0062 (16)
C19	0.048 (2)	0.052 (2)	0.0390 (17)	−0.0024 (16)	0.0171 (15)	−0.0044 (15)
C22	0.043 (2)	0.073 (3)	0.060 (2)	0.0074 (19)	0.0179 (18)	−0.005 (2)
C24	0.051 (2)	0.058 (2)	0.051 (2)	−0.0015 (17)	0.0167 (17)	−0.0070 (17)
C25	0.066 (3)	0.091 (3)	0.054 (2)	0.003 (2)	0.015 (2)	−0.005 (2)
C26	0.089 (3)	0.104 (4)	0.052 (2)	0.009 (3)	0.030 (2)	−0.007 (2)
C27	0.074 (3)	0.079 (3)	0.070 (3)	0.010 (2)	0.043 (2)	−0.003 (2)
C28	0.054 (2)	0.053 (2)	0.059 (2)	0.0000 (18)	0.0239 (19)	−0.0057 (18)
C29	0.0470 (19)	0.0449 (19)	0.052 (2)	−0.0002 (15)	0.0200 (17)	−0.0042 (16)

Geometric parameters (Å, º)

Co—O1	2.022 (2)	C5—C6	1.392 (5)
Co—O2	2.515 (3)	C5—C8	1.503 (4)
Co—O3^i	2.000 (2)	C6—C7	1.375 (5)
Co—N13	2.034 (3)	C6—H6	0.9300
Co—N23	2.039 (3)	C7—H7	0.9300
N11—C12	1.327 (5)	C12—H12	0.9300
N11—C18	1.377 (5)	C14—C15	1.376 (6)
N11—H11	0.8600	C14—C19	1.399 (5)
N13—C12	1.312 (4)	C14—H14	0.9300
N13—C19	1.394 (4)	C15—C16	1.400 (6)
N21—C22	1.332 (5)	C15—H15	0.9300
N21—C28	1.374 (5)	C16—C17	1.373 (6)
N21—H21	0.8600	C16—H16	0.9300
N23—C22	1.323 (4)	C17—C18	1.393 (5)
N23—C29	1.395 (4)	C17—H17	0.9300
C1—O1	1.262 (4)	C18—C19	1.392 (5)
C1—O2	1.235 (4)	C22—H22	0.9300
C8—O3	1.268 (4)	C24—C25	1.375 (5)
C8—O4	1.246 (4)	C24—C29	1.392 (5)
O3—Co^ii	2.000 (2)	C24—H24	0.9300
C1—C2	1.502 (5)	C25—C26	1.389 (6)
C2—C7	1.381 (5)	C25—H25	0.9300
C2—C3	1.388 (5)	C26—C27	1.369 (6)
C3—C4	1.382 (5)	C26—H26	0.9300
C3—H3	0.9300	C27—C28	1.391 (5)
C4—C5	1.375 (5)	C27—H27	0.9300
C4—H4	0.9300	C28—C29	1.394 (5)
O1—Co—O2	56.01 (9)	O4—C8—O3	123.6 (3)
O1—Co—O3^i	107.21 (10)	O4—C8—C5	119.0 (3)
O1—Co—N13	110.78 (11)	O3—C8—C5	117.4 (3)
O1—Co—N23	119.93 (11)	N13—C12—N11	113.6 (3)
O2—Co—O3^i	163.22 (9)	N13—C12—H12	123.2
O2—Co—N13	86.92 (10)	N11—C12—H12	123.2
O2—Co—N23	83.92 (10)	C15—C14—C19	117.2 (4)
O3^i—Co—N13	101.13 (10)	C15—C14—H14	121.4
O3^i—Co—N23	106.82 (11)	C19—C14—H14	121.4
N13—Co—N23	109.21 (12)	C14—C15—C16	122.2 (4)
C12—N11—C18	107.4 (3)	C14—C15—H15	118.9
C12—N11—H11	126.3	C16—C15—H15	118.9
C18—N11—H11	126.3	C17—C16—C15	121.3 (4)
C12—N13—C19	104.8 (3)	C17—C16—H16	119.4
C12—N13—Co	122.5 (3)	C15—C16—H16	119.4
C19—N13—Co	132.7 (2)	C16—C17—C18	116.5 (4)
C22—N21—C28	107.3 (3)	C16—C17—H17	121.7
C22—N21—H21	126.3	C18—C17—H17	121.7
C28—N21—H21	126.3	N11—C18—C17	131.8 (4)
C22—N23—C29	104.4 (3)	N11—C18—C19	105.4 (3)
C22—N23—Co	128.6 (3)	C17—C18—C19	122.8 (4)
C29—N23—Co	126.8 (2)	C18—C19—N13	108.8 (3)
Co—O1—C1	102.2 (2)	C18—C19—C14	120.0 (3)
Co—O2—C1	79.9 (2)	N13—C19—C14	131.1 (3)
Co^ii—O3—C8	110.4 (2)	N23—C22—N21	113.5 (3)
O2—C1—O1	121.1 (3)	N23—C22—H22	123.2
O2—C1—C2	119.7 (3)	N21—C22—H22	123.2
O1—C1—C2	119.2 (3)	C25—C24—C29	116.9 (4)
C7—C2—C3	118.5 (3)	C25—C24—H24	121.5
C7—C2—C1	119.6 (3)	C29—C24—H24	121.5
C3—C2—C1	121.7 (3)	C24—C25—C26	122.2 (4)
C4—C3—C2	120.5 (3)	C24—C25—H25	118.9
C4—C3—H3	119.7	C26—C25—H25	118.9
C2—C3—H3	119.7	C27—C26—C25	121.9 (4)
C5—C4—C3	121.0 (3)	C27—C26—H26	119.0
C5—C4—H4	119.5	C25—C26—H26	119.0
C3—C4—H4	119.5	C26—C27—C28	116.0 (4)
C4—C5—C6	118.4 (3)	C26—C27—H27	122.0
C4—C5—C8	121.4 (3)	C28—C27—H27	122.0
C6—C5—C8	120.2 (3)	N21—C28—C27	131.6 (4)
C7—C6—C5	120.7 (3)	N21—C28—C29	105.7 (3)
C7—C6—H6	119.6	C27—C28—C29	122.8 (4)
C5—C6—H6	119.6	C24—C29—C28	120.1 (3)
C6—C7—C2	120.9 (3)	C24—C29—N23	130.8 (3)
C6—C7—H7	119.6	C28—C29—N23	109.1 (3)
C2—C7—H7	119.6

Symmetry codes: (i) x+1/2, −y+1/2, z+1/2; (ii) x−1/2, −y+1/2, z−1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N11—H11···O1^iii	0.86	2.05	2.792 (4)	145
N21—H21···O4^iv	0.86	1.95	2.735 (4)	151

Symmetry codes: (iii) x, y+1, z; (iv) −x, −y+1, −z+1.