Tetra­aqua­(1,10-phenanthroline-κ²N,N′)cobalt(II) dinitrate: a hydrogen-bonded supra­molecular network

The structure of the title compound, [Co(C₁₂H₈N₂)(H₂O)₄](NO₃)₂, consists of tetra­aqua­(1,10-phenanthroline)cobalt(II) cations and nitrate anions. The Co atom is located on a twofold rotation axis and is coordinated by the two N atoms of a 1,10-phenanthroline ligand and four O atoms of water mol­ecules. The cations and anions are linked by hydrogen-bond inter­actions into a three-dimensional supra­molecular network.

S1. Comment

Metal-organic supramolecular complexes with various fascinating topologies have been widely studied for their versatile chemical and physical properties and potential applications as functional materials (Janiak, 2003; Kitagawa et al., 2004; Yaghi et al., 2003). Self-assembly based on molecular building blocks has become an effective approach to construct these functional materials. In the development of supramolecular chemistry, hydrogen-bonding and π–π interactions acting as two main driving forces play an important role in self-assembling multidimensional metal–organic supramolecular frameworks or networks (Graham & Pike, 2000; Mitzi et al., 1995). We report here the structure of [Co(phen)(H₂O)₄](NO₃)₂, (I) (phen is 1,10-phenanthroline), in which hydrogen-bonding interactions lead to a three-dimensional supramolecular network.

Compound (I), as shown in Fig.1, consists of [Co(phen)(H₂O)₄]²⁺ cations and NO₃^- anions. The Co atom, lying on a twofold rotation axis, is six-coordinated by two N atoms of a chelating phen ligand and four O atoms of water molecules in a octahedral geometry. The twofold rotation axis passes through the phen ligand. Therefore, the asymmetric unit of (I) contains half of the Co atom and half of the phen ligand accompanied by two water molecules and one NO₃^- anion. In the complex cation, two water molecules and two N atoms are located in the equatorial plane, and the other two water molecules occupy the axial positions. Bond lengths and angles are in normal ranges (Wang et al., 2005; Yang et al., 2003). Each of the coordinated water molecules donates its two H atoms to two neighboring nitrate anions, while each nitrate ion accepts four hydrogen bonds from four neighboring coordinated water molecules (Table 1). The equatorial water molecule (O2) is hydrogen-bonded to atoms O5 of two centrosymmetrically related nitrates at (1/2 - x, y - 1/2, 1/2 - z) and (1/2 + x, 1/2 - y, 1/2 + z), so generating a centrosymmetric R₄²(8) motif (Bernstein et al., 1995). The axial water molecule acts as hydrogen-bond donor to atom O3 of the nitrate group at (x, y, z) and atom O4 of another nitrate group at (1/2 - x, y - 1/2, 1/2 - z). In this way, a C₄⁴(12) helical chain is formed along the 2₁ screw axis in the [010] direction (Fig. 2). As a result, each complex cation is hydrogen bonded to six nitrate anions, which in turn link the other eight cations (Fig. 3). The effect of the two hydrogen-bond motifs is to link the complex cations and nitrate anions into a three-dimensional network. The structure is further stabilized by weak π–π stacking interactions between two adjacent phen rings in an offset arrangement. The distance between centroids of the six-membered C1–C4/C6/N1 ring and its equivalent at (1 - x, 1 - y, -z) is 3.73 (1) Å and the average interplanar spacing is 3.431 Å.

The phen ligand has strong chelating ability. Co^II–phen complexes can be formed with a Co^II to phen ratio of 1:1, 1:2 or 1:3. We have previously reported the structure of a 1:2 complex, [Co(phen)₂(NO₃)]NO₃·4H₂O (Li et al., 2006), in which a layer-like structure was observed consisting of hydrogen-bonded water–nitrate anionic sheets and π–π-interaction-linked [Co(phen)₂(NO₃)]⁺ cationic sheets. Thus, the hydrogen-bonding interactions between water molecules and nitrates, and π–π-interactions between phen ligands, are crucial to the structural architecture. We intend to examine further how anions influence supramolecular structures in the Co^II–phen system by varying the ratio of Co^II to phen when the anions have different geometry and hydrogen-bonding ability.

Related literature

For related literature, see: Bernstein et al. (1995); Graham & Pike (2000); Janiak (2003); Kitagawa et al. (2004); Li et al. (2006); Mitzi et al. (1995); Wang et al. (2005); Yaghi et al. (2003); Yang et al. (2003).

S2. Experimental

An aqueous solution of Co(NO₃)₂·6H₂O (60 mg, 0.1 mmol) and an ethanol solution of phen (40 mg, 0.1 mmol) were mixed and stirred for 30 min. The resulting solution was then left for aerial evaporation at room temperature. Dark-red crystals of (I), suitable in size for single-crystal X-ray diffraction, appeared after three weeks (yield 38%).

S3. Refinement

H atoms of the phen ring sysytem were positioned geometrically and refined as riding, with C—H distances of 0.93 Å and U_iso(H) values of 1.2U_eq(C). H atoms of water molecules were located in a difference map and refined with restraints of O—H = 0.85 (2) Å and H···H 1.33 (2) Å, with U_iso(H) set at 1.5U_eq(O).

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2001); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The structure of the complex cation in (I), showing the atomic numbering scheme. The nitrate anions are not shown. Displacement ellipsoids are drawn at the 30% probability level. [Symmetry code: (v) -x + 1, y, -z + 1/2.]
	Fig. 2. Two types of hydrogen-bonding motifs in (I). [Symmetry codes: (i) -x + 1/2, y - 1/2, -z + 1/2; (ii) x + 1/2, -y + 1/2, z + 1/2; (iii) x, y - 1, z; (iv) -x + 1, -y, -z + 1.]
	Fig. 3. View of the three-dimensional supramolecular structure in (I).

Tetraaqua(1,10-phenanthroline-κ²N,N')cobalt(II) dinitrate:

Crystal data

[Co(C12H8N2)(H2O)4](NO3)2	F(000) = 892
Mr = 435.22	Dx = 1.635 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 2877 reflections
a = 13.9136 (16) Å	θ = 2.5–25.9°
b = 10.4852 (12) Å	µ = 1.03 mm^−1
c = 12.3991 (14) Å	T = 293 K
β = 102.165 (2)°	Block, dark red
V = 1768.2 (3) Å^3	0.30 × 0.25 × 0.12 mm
Z = 4

Data collection

Bruker SMART APEX CCD area-detector diffractometer	1752 independent reflections
Radiation source: fine-focus sealed tube	1618 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.015
ϕ and ω scans	θmax = 26.1°, θmin = 2.5°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→17
Tmin = 0.746, Tmax = 0.887	k = −12→12
4991 measured reflections	l = −15→14

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)] = 0.029	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.075	H atoms treated by a mixture of independent and constrained refinement
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0413P)^2 + 0.9246P] where P = (Fo^2 + 2Fc^2)/3
1752 reflections	(Δ/σ)max < 0.001
135 parameters	Δρmax = 0.27 e Å^−3
6 restraints	Δρmin = −0.30 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	0.5000	0.27515 (3)	0.2500	0.03887 (13)
N1	0.44785 (11)	0.43326 (13)	0.14626 (11)	0.0395 (3)
N2	0.17761 (12)	0.45284 (15)	0.12111 (14)	0.0503 (4)
O1	0.35265 (10)	0.25288 (14)	0.26938 (13)	0.0538 (4)
H1A	0.3061 (16)	0.291 (2)	0.228 (2)	0.081*
H1B	0.3319 (18)	0.1785 (15)	0.270 (2)	0.081*
O2	0.52925 (12)	0.14077 (16)	0.37456 (14)	0.0688 (5)
H2A	0.4836 (15)	0.105 (3)	0.396 (2)	0.103*
H2B	0.5809 (13)	0.123 (3)	0.414 (2)	0.103*
O3	0.19687 (12)	0.34428 (14)	0.09400 (16)	0.0748 (5)
O4	0.21561 (14)	0.49567 (17)	0.21250 (13)	0.0770 (5)
O5	0.12028 (12)	0.52086 (16)	0.05359 (13)	0.0701 (4)
C1	0.39318 (14)	0.43170 (19)	0.04427 (15)	0.0476 (4)
H1	0.3777	0.3533	0.0098	0.057*
C2	0.35809 (16)	0.5425 (2)	−0.01330 (17)	0.0576 (5)
H2	0.3192	0.5375	−0.0841	0.069*
C3	0.38140 (16)	0.6581 (2)	0.03535 (17)	0.0590 (5)
H3	0.3586	0.7325	−0.0023	0.071*
C4	0.43995 (15)	0.66483 (17)	0.14252 (16)	0.0493 (4)
C5	0.47112 (19)	0.78144 (18)	0.1990 (2)	0.0644 (6)
H5	0.4512	0.8587	0.1647	0.077*
C6	0.47060 (12)	0.54846 (16)	0.19459 (14)	0.0394 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Co	0.0427 (2)	0.03023 (19)	0.0396 (2)	0.000	−0.00060 (14)	0.000
N1	0.0425 (8)	0.0361 (7)	0.0389 (7)	−0.0007 (6)	0.0061 (6)	0.0021 (6)
N2	0.0446 (9)	0.0474 (9)	0.0553 (9)	0.0037 (7)	0.0020 (7)	−0.0059 (7)
O1	0.0450 (8)	0.0484 (7)	0.0645 (9)	0.0004 (6)	0.0038 (7)	0.0132 (7)
O2	0.0631 (9)	0.0619 (9)	0.0710 (10)	−0.0048 (8)	−0.0096 (8)	0.0298 (8)
O3	0.0681 (10)	0.0470 (9)	0.1079 (13)	0.0072 (7)	0.0150 (9)	−0.0215 (8)
O4	0.0844 (11)	0.0761 (11)	0.0566 (9)	0.0113 (9)	−0.0165 (8)	−0.0120 (8)
O5	0.0697 (10)	0.0692 (10)	0.0609 (9)	0.0196 (8)	−0.0098 (7)	−0.0005 (8)
C1	0.0477 (10)	0.0503 (10)	0.0424 (9)	−0.0020 (8)	0.0038 (8)	0.0019 (8)
C2	0.0557 (12)	0.0669 (13)	0.0468 (10)	0.0023 (10)	0.0029 (9)	0.0158 (9)
C3	0.0639 (13)	0.0534 (12)	0.0597 (12)	0.0108 (10)	0.0132 (10)	0.0226 (10)
C4	0.0564 (11)	0.0388 (10)	0.0559 (11)	0.0055 (8)	0.0192 (9)	0.0109 (8)
C5	0.0861 (17)	0.0327 (10)	0.0783 (15)	0.0058 (9)	0.0258 (13)	0.0096 (9)
C6	0.0424 (9)	0.0340 (8)	0.0435 (9)	0.0013 (7)	0.0128 (7)	0.0030 (7)

Geometric parameters (Å, º)

Co—O2	2.0667 (14)	O2—H2A	0.828 (16)
Co—O2^i	2.0668 (14)	O2—H2B	0.804 (16)
Co—O1	2.1268 (15)	C1—C2	1.397 (3)
Co—O1^i	2.1268 (15)	C1—H1	0.9300
Co—N1	2.1298 (14)	C2—C3	1.362 (3)
Co—N1^i	2.1298 (14)	C2—H2	0.9300
N1—C1	1.331 (2)	C3—C4	1.406 (3)
N1—C6	1.356 (2)	C3—H3	0.9300
N2—O4	1.230 (2)	C4—C6	1.404 (2)
N2—O3	1.232 (2)	C4—C5	1.430 (3)
N2—O5	1.251 (2)	C5—C5^i	1.348 (5)
O1—H1A	0.839 (16)	C5—H5	0.9300
O1—H1B	0.832 (16)	C6—C6^i	1.444 (3)
O2—Co—O2^i	94.04 (11)	H1A—O1—H1B	103 (2)
O2—Co—O1	83.30 (6)	Co—O2—H2A	120 (2)
O2^i—Co—O1	88.10 (7)	Co—O2—H2B	129 (2)
O2—Co—O1^i	88.10 (7)	H2A—O2—H2B	110 (2)
O2^i—Co—O1^i	83.31 (6)	N1—C1—C2	122.90 (18)
O1—Co—O1^i	167.39 (8)	N1—C1—H1	118.5
O2—Co—N1	166.02 (7)	C2—C1—H1	118.5
O2^i—Co—N1	95.22 (6)	C3—C2—C1	119.26 (18)
O1—Co—N1	86.56 (5)	C3—C2—H2	120.4
O1^i—Co—N1	103.36 (6)	C1—C2—H2	120.4
O2—Co—N1^i	95.22 (6)	C2—C3—C4	119.97 (18)
O2^i—Co—N1^i	166.02 (7)	C2—C3—H3	120.0
O1—Co—N1^i	103.36 (6)	C4—C3—H3	120.0
O1^i—Co—N1^i	86.55 (5)	C6—C4—C3	116.75 (18)
N1—Co—N1^i	77.77 (8)	C6—C4—C5	119.11 (18)
C1—N1—C6	117.66 (15)	C3—C4—C5	124.12 (18)
C1—N1—Co	128.15 (12)	C5^i—C5—C4	121.24 (12)
C6—N1—Co	114.11 (11)	C5^i—C5—H5	119.4
O4—N2—O3	120.84 (18)	C4—C5—H5	119.4
O4—N2—O5	119.88 (17)	N1—C6—C4	123.44 (15)
O3—N2—O5	119.26 (17)	N1—C6—C6^i	116.96 (9)
Co—O1—H1A	121.2 (18)	C4—C6—C6^i	119.60 (11)
Co—O1—H1B	116.7 (17)

Symmetry code: (i) −x+1, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1A···O3	0.84 (2)	2.08 (2)	2.891 (2)	163 (3)
O1—H1B···O4^ii	0.83 (2)	2.05 (2)	2.884 (2)	175 (2)
O2—H2A···O5^ii	0.83 (2)	1.91 (2)	2.736 (2)	179 (3)
O2—H2B···O5^iii	0.80 (2)	2.27 (3)	2.867 (2)	132 (2)

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