cis-Dichloridobis(1,10-phenanthroline-5,6-diol-κ²N,N′)manganese(II): a supra­molecular chain formed via O—H...Cl bonds and aromatic stacking

The title compound, [MnCl₂(C₁₂H₈N₂O₂)₂], displays a novel supra­molecular chain formed by inter­molecular O—H...Cl hydrogen bonds and aromatic stacking. The molecule has crystallographically imposed twofold symmetry with the Mn^II atom on the twofold axis. In the 1,10-phenanthroline-5,6-diol ligand, each H atom of the two hydr­oxy groups is oriented towards the other hydr­oxy O atom. Both hydr­oxy groups form inter­molecular O—H...Cl hydrogen bonds with a single Cl atom of an adjacent mol­ecule. These hydrogen bonds connect the mol­ecules via operation of the mol­ecular twofold axis and the centre of inversion of the crystal lattice, forming a doubly-bridged one-dimensional structure with Mn atoms as the nodes. Strong aromatic π-stacking between two anti­parallel neighbouring 1,10-phenanthroline-5,6-diol ligands also helps to stabilize the chain.

S1. Comment

In recent years there has been a rapidly increasing interest in the construction of various kinds of supramolecular systems for understanding molecular self-assembly principles and for designing molecular recognition devices. The term `supramolecular system' generally refers to an assembly of molecules which are not covalently connected but assembled by other weak intermolecular interactions, such as hydrogen bonds and aromatic π–π stacking (Grabowski, 2005; Lehn, 1995; Pak et al., 2005; Scheiner, 1997). Choosing appropriate ligands is essential in designing supramolecular systems. The rigid 1,10-phenanthroline-5,6-diol (phendiol) molecule is a versatile ligand from the structural point of view. The diimine group undoubtedly makes phendiol a strong chelating ligand. The diol groups can also easily function as another biting site upon deprotonation. Thus, phendiol can be either N,N',O,O'-tetradentate (Fox et al., 1991; Ghosh et al., 2005; Hill et al., 1997; Paw & Eisenberg, 1997; Paw et al., 1998; Shavaleev et al., 2003; Shukla & Das, 2000; Wu et al., 2002), N,N'-bidentate (Ghosh et al., 2005; Larsson & Ohrstrom, 2004; Murtaza et al., 2002; Shukla & Das, 2000) or O,O'-bidentate (Ghosh et al., 2005; Larsson & Ohrstrom, 2004; Murtaza et al., 2002; Parsons et al., 2006; Paw et al., 1998; Shukla & Das, 2000). On the other hand, the planar fused ring system makes it possible for phendiol to form π–π stacking interactions (Larsson & Ohrstrom, 2004). It is expected that the two hydroxy groups, if not deprotonated, may be able to act as intra/intermolecular hydrogen-bond donors or acceptors.

Although a number of phendiol-related complexes have been reported, until now there has been only one compound containing the neutral phendiol (undeprotonated [protonated?]) molecule whose crystal structure has been determined. This compound is [Co(phendione)(phendiol)₂]Br₃ (phendione is 1,10-phenanthroline-5,6-dione), in which phendiol was created by slow hydration from phendione in [Co(phendione)₃]Br₃ (Larsson & Ohrstrom, 2004). The bromide counter-anions bridge the phendiols via hydrogen bonds to form layers. The phendione fragment is not involved in hydrogen bonding, but is instead inserted in the cavity between two phendiol ligands. We report here the synthesis and characterization of cis-[MnCl₂(phendiol)₂], (I), in which an interesting helical structure is present through the intermolecular hydrogen-bond network between the phendiol hydroxy groups and chloride; there is also stacking of the phendiol groups.

The crystal structure indicates that the phendiol ligand was not deprotonated, despite the fact that the amount of MnCl₂ was more than twice that of phendiol, which might favour phendiol acting as a bridging ligand; the hydrothermal method also usually favours the formation of water-insoluble metal–organic frameworks. We speculate that the acidity of MnCl₂ and the O—H···Cl bonds helped to keep the hydroxy groups from deprotonation. The reaction of MnCl₂ and phendiol under ambient conditions also produced the title complex as confirmed by IR. The IR spectrum of the free phendiol shows a broad and strong O—H band at 2972 cm^-1, indicative of intermolecular hydrogen bonding between the hydroxy groups. For (I), the O—H band moves upwards to 3301 cm^-1 and is weaker, implying that the hydroxy groups of the phendiol ligand remain uncoordinated and the hydrogen bonding is weakened. This is consistent with the crystal structure analysis (see below), as the intermolecular O—H···Cl bonds replace the relatively stronger O—H···O interaction in the free ligand. The IR band at 411 cm^-1 for the complex but not the ligand is ascribed to the Mn—N coordination bond.

The neutral compound (I) crystallizes without disorder or any solvent. The molecule exhibits C₂ symmetry with Mn^II located on the twofold axis. As shown in Fig. 1 and Table 1, the Mn^II ion is hexacoordinated in a distorted octahedral geometry surrounded by four N atoms from two phendiol molecules and two Cl^- anions. The four ligands surround the central atom in a cis configuration. The geometric parameters of the coordinated phendiol are close to those in the only structurally characterized phendiol complex, [Co(phendione)(phendiol)₂]Br₃ (Larsson & Ohrstrom, 2004). It is also worth comparing the structural features of the title compound and cis-[Mn(phen)₂Cl₂] (phen is 1,10-phenanthroline), which has been studied by X-ray diffraction several times (Malinowski et al., 1996; McCann et al., 1998; Zhou et al., 1997). The Mn—N bond lengths in (I) exhibit two different values, reflecting the trans influence. Cl^- is a π-donor and 1,10-phenanthroline-like polypyridines are π-acceptors. Thus, the N atom trans to the phendiol N atom is a little closer to the Mn^II ion than that trans to Cl^-. These two Mn—N bonds are both shorter than the corresponding ones in cis-[Mn(phen)₂Cl₂], which are in the range 2.281–2.295 and 2.368–2.371 Å trans to the imine N atom and the Cl atom, respectively. The reasons might be that the donating hydroxy groups on the phendiol ligand strengthen the Mn—N bond through the fused ring system. Accordingly, the Mn—Cl bond length in (I) is greater than that in cis-[Mn(phen)₂Cl₂] (2.436–2.454 Å).

Both H atoms of the hydroxy groups in the phendiol ligand were located in a Fourier difference map. It is interesting that each of the two H atoms orients toward the adjacent hydroxy O atom, although their separation is quite short (1.95 Å). The two hydroxy groups in each phendiol ligand form intermolecular O—H···Cl hydrogen bonds with a single Cl atom of an adjacent molecule that is related by a centre of inversion (Table 2). The O—H···Cl hydrogen-bond data found here are comparable with those found in the literature (Fielden et al., 2006; George et al., 2006; Venegas-Yazigi et al., 2006; Wong et al., 2006). The four O—H···Cl bonds about each inversion centre form a ring containing two Mn^II atoms, two Cl atoms and two phendiol ligands (Fig. 2). Through operation of the twofold axes through the Mn^II atoms, these rings are linked and expanded to a knotted double-helical chain structure in the [001] direction, with the Mn atoms as the knots (Fig. 2). In pairs of inversion-related molecules, the two antiparallel phendiol ligands overlap in an offset face-to-face geometry. There is strong aromatic π-stacking between the two phendiol ligands. The ring planes are separated by 3.3456 (7) Å. The distance between the centroids of the central benzene rings of the two phendiol ligands is 3.4135 (10) Å. These parameters are typical of π–π interactions and are among the strongest of such interactions (Janiak, 2000; Russell et al., 2001). This aromatic π-stacking force is undoubtedly another important factor in the stablization of the double-helix structure. There is no remarkable interaction between the helical chains.

Related literature

For related literature, see: Fox et al. (1991); George et al. (2006); Ghosh et al. (2005); Grabowski (2005); Hill et al. (1997); Janiak (2000); Larsson & Ohrstrom (2004); Lehn (1995); Malinowski et al. (1996); McCann et al. (1998); Murtaza et al. (2002); Pak et al. (2005); Parsons et al. (2006); Paw & Eisenberg (1997); Paw et al. (1998); Russell et al. (2001); Scheiner (1997); Shavaleev et al. (2003); Shukla & Das (2000); Venegas-Yazigi, Cortés, Paredes-García, Pena, Ibanez, Baggio & Spodine (2006); Wong et al. (2006); Wu et al. (2002); Zhou et al. (1997).

S2. Experimental

1,10-Phenanthroline-5,6-diol (phendiol) was prepared from 1,10-phenanthroline-5,6-dione according to our previously reported method (Wu et al., 2002). Phendiol (0.0646 g, 0.3 mmol) and MnCl₂.4H₂O (0.1686 g, 0.85 mmol) were mixed with 10 ml of water and sealed in a 15 ml stainless steel bomb with Teflon liner and heated to 433 K for 50 h. After cooling to room temperature, brown block crystals were obtained, with a yield of 0.0725 g, 88%, based on the ligand. Analysis found: C 52.54, H 2.82, N 10.36%; C₂₄H₁₆N₄O₄Cl₂Mn requires: C 52.39, H 2.93, N 10.18%. IR (ν_max, cm^-1): 3301br/m, 1625 s, 1591m, 1429m, 1315m, 1123m, 1064 s, 1025 s, 818 s, 734 s, 411m.

S3. Refinement

All H atoms were located in difference maps and then treated as riding atoms in geometrically idealized positions with C—H distances of 0.93 Å and O—H distances of 0.82 Å, and with U_iso(H) = 1.2U_eq(C) or 1.52U_eq(O).

Computing details

Data collection: SMART or APEX2? (Bruker, 1998); cell refinement: SAINT or APEX2? (Bruker, 1999); data reduction: SAINT or APEX2? (Bruker, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. ORTEP drawing (25% ellipsoid probability) of (I) with atom numbering of the structurally unique non-H atoms and the hydroxy H atoms.
	Fig. 2. The packing of (I) viewed down the a axis. H atoms omitted for clarity, except those attached to O atoms. Dashed lines indicate intermolecular O—H···Cl hydrogen bonds.

cis-Dichloridobis(1,10-phenanthroline-5,6-diol- κ²N,N')manganese(II)

Crystal data

[MnCl2(C12H8N2O2)2]	F(000) = 1116
Mr = 550.25	Dx = 1.667 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 5172 reflections
a = 8.5272 (2) Å	θ = 2.8–27.9°
b = 14.4503 (4) Å	µ = 0.89 mm^−1
c = 18.1776 (5) Å	T = 293 K
β = 101.777 (2)°	Block, brown
V = 2192.70 (10) Å^3	0.23 × 0.21 × 0.20 mm
Z = 4

Data collection

Bruker APEXII area-detector diffractometer	2350 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.025
Graphite monochromator	θmax = 27.9°, θmin = 2.3°
ϕ and ω scans	h = −9→11
9077 measured reflections	k = −18→18
2600 independent reflections	l = −23→23

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)] = 0.031	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.082	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0359P)^2 + 2.8002P] where P = (Fo^2 + 2Fc^2)/3
2600 reflections	(Δ/σ)max = 0.001
161 parameters	Δρmax = 0.59 e Å^−3
0 restraints	Δρmin = −0.27 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
C1	0.6890 (2)	1.13728 (13)	0.32165 (10)	0.0347 (4)
H1	0.6637	1.1865	0.2884	0.042*
C2	0.5839 (2)	1.11507 (15)	0.36820 (12)	0.0423 (5)
H2	0.4903	1.1490	0.3660	0.051*
C3	0.6200 (2)	1.04256 (16)	0.41731 (11)	0.0411 (4)
H3	0.5508	1.0270	0.4489	0.049*
C4	0.7615 (2)	0.99162 (13)	0.42005 (9)	0.0312 (4)
C5	0.8075 (2)	0.91565 (13)	0.47055 (10)	0.0353 (4)
C6	0.9459 (2)	0.86860 (12)	0.47106 (10)	0.0355 (4)
C7	1.0486 (2)	0.89436 (12)	0.42133 (10)	0.0320 (4)
C8	1.1933 (3)	0.84805 (14)	0.41942 (11)	0.0424 (5)
H8	1.2249	0.7979	0.4510	0.051*
C9	1.2866 (3)	0.87670 (14)	0.37135 (13)	0.0459 (5)
H9	1.3815	0.8460	0.3694	0.055*
C10	1.2378 (2)	0.95273 (14)	0.32515 (11)	0.0383 (4)
H10	1.3026	0.9722	0.2927	0.046*
C11	1.0084 (2)	0.96950 (11)	0.37212 (9)	0.0272 (3)
C12	0.86085 (19)	1.01903 (11)	0.37113 (9)	0.0264 (3)
Cl1	1.16436 (5)	1.23062 (3)	0.34049 (2)	0.03758 (13)
Mn1	1.0000	1.12141 (2)	0.2500	0.02599 (11)
N1	0.82424 (16)	1.09106 (10)	0.32280 (8)	0.0276 (3)
N2	1.10312 (17)	0.99856 (10)	0.32532 (8)	0.0297 (3)
O2	0.9982 (2)	0.79494 (10)	0.51669 (9)	0.0524 (4)
H21	0.9381	0.7871	0.5461	0.079*
O1	0.70157 (19)	0.89526 (12)	0.51542 (9)	0.0529 (4)
H11	0.7374	0.8529	0.5440	0.079*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0317 (9)	0.0405 (10)	0.0322 (9)	0.0063 (7)	0.0071 (7)	0.0032 (7)
C2	0.0285 (9)	0.0607 (13)	0.0395 (10)	0.0086 (8)	0.0109 (8)	0.0034 (9)
C3	0.0307 (9)	0.0618 (13)	0.0338 (9)	−0.0035 (8)	0.0132 (7)	0.0032 (9)
C4	0.0305 (8)	0.0387 (9)	0.0242 (8)	−0.0067 (7)	0.0048 (6)	−0.0010 (7)
C5	0.0414 (10)	0.0393 (10)	0.0263 (8)	−0.0113 (8)	0.0092 (7)	0.0017 (7)
C6	0.0491 (11)	0.0291 (9)	0.0272 (8)	−0.0048 (7)	0.0054 (7)	0.0036 (6)
C7	0.0411 (10)	0.0273 (8)	0.0268 (8)	−0.0006 (7)	0.0051 (7)	−0.0002 (6)
C8	0.0539 (12)	0.0335 (9)	0.0392 (10)	0.0127 (8)	0.0082 (9)	0.0088 (8)
C9	0.0458 (11)	0.0450 (11)	0.0478 (12)	0.0194 (9)	0.0120 (9)	0.0077 (9)
C10	0.0349 (9)	0.0425 (10)	0.0395 (10)	0.0084 (8)	0.0123 (8)	0.0071 (8)
C11	0.0313 (8)	0.0251 (8)	0.0244 (7)	−0.0012 (6)	0.0041 (6)	−0.0008 (6)
C12	0.0275 (8)	0.0290 (8)	0.0223 (7)	−0.0035 (6)	0.0042 (6)	−0.0013 (6)
Cl1	0.0404 (3)	0.0379 (2)	0.0333 (2)	−0.00613 (17)	0.00493 (18)	−0.00481 (17)
Mn1	0.02674 (19)	0.02773 (19)	0.02457 (19)	0.000	0.00773 (13)	0.000
N1	0.0270 (7)	0.0308 (7)	0.0252 (7)	0.0016 (5)	0.0056 (5)	0.0006 (5)
N2	0.0294 (7)	0.0303 (7)	0.0303 (7)	0.0028 (5)	0.0079 (6)	0.0027 (6)
O1	0.0513 (9)	0.0680 (11)	0.0442 (8)	−0.0073 (7)	0.0211 (7)	0.0186 (7)
O2	0.0750 (11)	0.0417 (8)	0.0436 (8)	0.0078 (7)	0.0192 (8)	0.0186 (7)

Geometric parameters (Å, º)

C1—N1	1.329 (2)	C8—C9	1.361 (3)
C1—C2	1.390 (3)	C8—H8	0.9300
C1—H1	0.9300	C9—C10	1.394 (3)
C2—C3	1.370 (3)	C9—H9	0.9300
C2—H2	0.9300	C10—N2	1.326 (2)
C3—C4	1.406 (3)	C10—H10	0.9300
C3—H3	0.9300	C11—N2	1.354 (2)
C4—C12	1.404 (2)	C11—C12	1.444 (2)
C4—C5	1.433 (3)	C12—N1	1.357 (2)
C5—C6	1.360 (3)	Mn1—N1	2.2359 (14)
C5—O1	1.367 (2)	Mn1—N2	2.3039 (14)
C6—O2	1.367 (2)	Mn1—Cl1	2.4938 (5)
C6—C7	1.431 (3)	O2—H21	0.8200
C7—C11	1.404 (2)	O1—H11	0.8200
C7—C8	1.410 (3)
N1—C1—C2	122.66 (17)	N2—C10—C9	122.98 (18)
N1—C1—H1	118.7	N2—C10—H10	118.5
C2—C1—H1	118.7	C9—C10—H10	118.5
C3—C2—C1	119.08 (18)	N2—C11—C7	122.71 (16)
C3—C2—H2	120.5	N2—C11—C12	117.93 (14)
C1—C2—H2	120.5	C7—C11—C12	119.36 (15)
C2—C3—C4	120.04 (17)	N1—C12—C4	122.52 (15)
C2—C3—H3	120.0	N1—C12—C11	118.23 (14)
C4—C3—H3	120.0	C4—C12—C11	119.26 (15)
C12—C4—C3	117.02 (16)	N1^i—Mn1—N1	157.37 (8)
C12—C4—C5	120.01 (16)	N1—Mn1—N2^i	88.85 (5)
C3—C4—C5	122.96 (16)	N1—Mn1—N2	73.61 (5)
C6—C5—O1	124.47 (17)	N2^i—Mn1—N2	79.19 (7)
C6—C5—C4	120.70 (16)	N1—Mn1—Cl1	95.05 (4)
O1—C5—C4	114.83 (17)	N2^i—Mn1—Cl1	167.04 (4)
C5—C6—O2	124.66 (17)	N2—Mn1—Cl1	90.04 (4)
C5—C6—C7	120.53 (16)	N1—Mn1—Cl1^i	99.22 (4)
O2—C6—C7	114.81 (18)	N2—Mn1—Cl1^i	167.04 (4)
C11—C7—C8	116.92 (17)	Cl1—Mn1—Cl1^i	101.49 (3)
C11—C7—C6	120.14 (17)	C1—N1—C12	118.69 (15)
C8—C7—C6	122.94 (17)	C1—N1—Mn1	125.19 (12)
C9—C8—C7	120.04 (18)	C12—N1—Mn1	116.12 (10)
C9—C8—H8	120.0	C10—N2—C11	118.34 (15)
C7—C8—H8	120.0	C10—N2—Mn1	127.51 (12)
C8—C9—C10	118.99 (18)	C11—N2—Mn1	114.08 (11)
C8—C9—H9	120.5	C6—O2—H21	109.5
C10—C9—H9	120.5	C5—O1—H11	109.5
N1—C1—C2—C3	−0.2 (3)	C2—C1—N1—C12	0.3 (3)
C1—C2—C3—C4	−0.1 (3)	C2—C1—N1—Mn1	179.83 (15)
C2—C3—C4—C12	0.3 (3)	C4—C12—N1—C1	−0.1 (2)
C2—C3—C4—C5	179.32 (18)	C11—C12—N1—C1	−179.77 (15)
C12—C4—C5—C6	−0.9 (3)	C4—C12—N1—Mn1	−179.71 (12)
C3—C4—C5—C6	−179.92 (18)	C11—C12—N1—Mn1	0.66 (18)
C12—C4—C5—O1	180.00 (16)	N1^i—Mn1—N1—C1	−140.20 (15)
C3—C4—C5—O1	1.0 (3)	N2^i—Mn1—N1—C1	−101.64 (15)
O1—C5—C6—O2	−0.3 (3)	N2—Mn1—N1—C1	179.29 (15)
C4—C5—C6—O2	−179.36 (17)	Cl1—Mn1—N1—C1	90.74 (14)
O1—C5—C6—C7	179.28 (18)	Cl1^i—Mn1—N1—C1	−11.79 (15)
C4—C5—C6—C7	0.3 (3)	N1^i—Mn1—N1—C12	39.35 (11)
C5—C6—C7—C11	0.9 (3)	N2^i—Mn1—N1—C12	77.90 (12)
O2—C6—C7—C11	−179.48 (16)	N2—Mn1—N1—C12	−1.16 (11)
C5—C6—C7—C8	−179.96 (18)	Cl1—Mn1—N1—C12	−89.71 (11)
O2—C6—C7—C8	−0.3 (3)	Cl1^i—Mn1—N1—C12	167.76 (11)
C11—C7—C8—C9	0.0 (3)	C9—C10—N2—C11	−0.6 (3)
C6—C7—C8—C9	−179.2 (2)	C9—C10—N2—Mn1	−177.48 (15)
C7—C8—C9—C10	0.8 (3)	C7—C11—N2—C10	1.4 (3)
C8—C9—C10—N2	−0.5 (3)	C12—C11—N2—C10	−179.13 (16)
C8—C7—C11—N2	−1.1 (3)	C7—C11—N2—Mn1	178.69 (13)
C6—C7—C11—N2	178.16 (16)	C12—C11—N2—Mn1	−1.82 (19)
C8—C7—C11—C12	179.44 (16)	N1—Mn1—N2—C10	178.59 (17)
C6—C7—C11—C12	−1.3 (2)	N1^i—Mn1—N2—C10	13.07 (16)
C3—C4—C12—N1	−0.1 (3)	N2^i—Mn1—N2—C10	86.59 (16)
C5—C4—C12—N1	−179.22 (15)	Cl1—Mn1—N2—C10	−86.15 (16)
C3—C4—C12—C11	179.48 (16)	Cl1^i—Mn1—N2—C10	120.87 (19)
C5—C4—C12—C11	0.4 (2)	N1—Mn1—N2—C11	1.57 (11)
N2—C11—C12—N1	0.8 (2)	N1^i—Mn1—N2—C11	−163.95 (12)
C7—C11—C12—N1	−179.65 (15)	N2^i—Mn1—N2—C11	−90.43 (12)
N2—C11—C12—C4	−178.81 (15)	Cl1—Mn1—N2—C11	96.83 (11)
C7—C11—C12—C4	0.7 (2)	Cl1^i—Mn1—N2—C11	−56.2 (2)

Symmetry code: (i) −x+2, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H11···Cl1^ii	0.82	2.42	3.2020 (16)	161
O2—H21···Cl1^ii	0.82	2.41	3.2042 (16)	163

Symmetry code: (ii) −x+2, −y+2, −z+1.