Tetra­aqua(1,10-phenanthroline-κ²N,N′)­manganese(II) sulfate dihydrate

The title compound, [Mn(C₁₂H₈N₂)(H₂O)₄]SO₄·2H₂O, was obtained unexpectedly as a by-product from the reaction of sodium maleate, 1,10-phenanthroline (phen) and manganese sulfate tetrahydrate. The Mn atom is coordinated by the two N atoms of the phen ligand and four water O atoms in a highly distorted octahedral geometry, with Mn—O distances in the range 2.155 (2)–2.203 (2) Å and Mn—N distances of 2.254 (2) and 2.272 (3) Å. Extensive hydrogen-bonding interactions involving the water mol­ecules and sulfate anions, and stacking interactions involving the phen rings, are observed in the crystal structure.

S1. Comment

It has been well established that manganese is one of trace elements in biosystems and plays an important role in the active sites of various redox-based enzymes (Weighardt, 1989). In addition to the best known oxygen-evolving complex (OEC), which is believed to contain a tetranuclear manganese cluster catalysing the oxidation of water to yield dioxygen during the photosynthetic process (Debus, 1992), there are three manganese enzymes containing a mononuclear manganese site, viz. superoxide dismutase, peroxidase and dioxygenase, which participate in redox changes in biological systems (Law et al., 1999). Carboxylato-bridged complexes containing 1,10-phenanthroline (phen) or bipyridine (bpy) are often employed to mimic the function and structure of these active sites built on the knowledge that the Mn centers in these enzymes are predominately coordinated by N,O-donors from available amino acid side chains (Pecoraro et al., 1986). With the initial intention of preparing a maleate-bridged polymanganese complex, we obtained the title compound, (I), unexpectedly. Compound (I) represents a new example of mononuclear manganese, with only one phen ligand and with sulfate as counter-ion, though a similar complex, [Mn(C₁₂H₈N₂)(H₂O)₃]SO₄ has been reported (Zheng et al., 2000).

The title compound consists of a discrete non-centrosymmetric [Mn(phen)(H₂O)₄]²⁺ unit, a sulfate anion and two solvate water molecules. The Mn atom displays a distorted octahedral environment (Table 1). The two phen N atoms and two water O atoms (O1 and O3) define one octahedral equatorial plane, with a maximum deviation of 0.181 (4) Å for atom N1, with the Mn atom lying 0.015 (5) Å out of the plane. The O atoms of the remaining two water molecules complete the octahedron through coordination in the axial positions. The phen rings are nearly planar, with a mean atomic deviation of 0.022 (1) Å. A small dihedral angle of 9.40 (1)° was found between phen and the above-mentioned equatorial planes, indicating that the phen plane can be extended to involve atoms O1 and O3. The mean Mn—N bond length [2.263 (4) Å] is in agreement with that reported in other Mn–phen complexes, e.g. [Mn(phen)₂Cl(H₂O)]⁺ [2.270 (1) Å; Ma et al., 2001], but longer than that found in the nickel analogue [2.069 (2) Å; Cherni et al., 1999], due to the larger radius of the Mn^II ion. The angle that is most distorted from the ideal value of 180° is O3—Mn—N2 of 161.8 (1)°, and the phen N1—Mn—N2 chelate angle of 73.3 (1)° is expected for manganese complexes (Drew et al., 1989; McCann et al., 1997; Ramalakshmi et al., 1999; Wang et al., 2000; Deng et al., 2000). The bond distances and angles in the phen ligand are consistent with those in the free base (Nishigaki et al., 1978), and the S—O bond distances [1.464 (2)–1.478 (2) Å] and O—S—O angles [109.0 (1)–109.8 (1)°] approximate to the respective values of an ideal tetrahedral S-atom environment.

As shown in Fig. 2, extensive intermolecular hydrogen bonds link [Mn(phen)(H₂O)₄]²⁺ cations to uncoordinated water molecules and sulfate anions (Table 2), creating a three-dimensional suspended ladder-like framework. Additionally, there is a π–π-stacking interaction between phen ligands, which are arranged in an alternate head-tail mode, resulting in a ring separation of 3.561 (1) Å, which is close to the sum of the van der Waals radii of two C atoms (Bondi, 1964). The two types of interaction produce the special solid-state crystal structure seen in (I) and promote the stabilization of the structure.

S2. Experimental

To an aqueous ethanol solution (30 ml, v/v, ca 1:1) containing MnSO₄·4H₂O (2 mmol) and sodium maleate (2 mmol), 1,10-phenanthroline (4 mmol) was added slowly with continuous stirring. The resulting suspension was refluxed for 8 h and then filtered. The red filtrate was maintained at room temperature for 25 d, after which time colorless crystals of the title compound suitable for X-ray diffraction analysis were obtained.

S3. Refinement

H atoms bonded to C atoms were placed in calculated positions, with C—H distances of 0.93 Å, and treated as riding atoms. Water H atoms associated were located from difference maps and refined anisotropically (see Table 2 for O—H distances).

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1994); data reduction: XPREP in SHELXTL (Siemens, 1994); program(s) used to solve structure: SHELXTL; program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. Displacement-ellipsoid drawing of the title compound with the atomic labeling scheme and 30% probability displacement ellipsoids.
	Fig. 2. Packing diagram of the title compound, showing the complex hydrogen-bonding and π–π-stacking interactions. Hydrogen bonds are depicted by broken lines.

Tetraaqua(1,10-phenanthroline-κ²N,N')manganese(II) sulfate dihydrate

Crystal data

[Mn(C12H8N2)(H2O)4]SO4·2H2O	Dx = 1.608 Mg m^−3
Mr = 439.30	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbca	Cell parameters from 5079 reflections
a = 8.8713 (2) Å	θ = 1.8–25.1°
b = 18.5116 (1) Å	µ = 0.90 mm^−1
c = 22.1042 (5) Å	T = 293 K
V = 3630.00 (12) Å^3	Prism, colorless
Z = 8	0.57 × 0.44 × 0.37 mm
F(000) = 1816

Data collection

Siemens CCD area-detector diffractometer	3190 independent reflections
Radiation source: fine-focus sealed tube	2293 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.045
ϕ and ω scans	θmax = 25.1°, θmin = 1.8°
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996)	h = −10→10
Tmin = 0.526, Tmax = 0.718	k = −22→20
11327 measured reflections	l = −19→26

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.038	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.097	w = 1/[σ^2(Fo^2) + (0.0421P)^2 + 1.5395P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max < 0.001
3190 reflections	Δρmax = 0.26 e Å^−3
284 parameters	Δρmin = −0.30 e Å^−3
11 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0031 (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
Mn	0.36570 (5)	0.08805 (2)	0.41472 (2)	0.03364 (17)
S	−0.08896 (9)	0.15599 (4)	0.53212 (4)	0.0362 (2)
O1	0.2360 (3)	0.03679 (12)	0.48810 (11)	0.0446 (6)
H1B	0.169 (3)	0.0592 (16)	0.5080 (14)	0.049 (11)*
H1C	0.211 (4)	−0.010 (2)	0.4900 (16)	0.065 (12)*
O2	0.5138 (3)	−0.00549 (12)	0.42446 (11)	0.0434 (6)
H2B	0.580 (3)	−0.0148 (18)	0.4495 (12)	0.045 (11)*
H2C	0.488 (5)	−0.0445 (14)	0.4087 (17)	0.084 (15)*
O3	0.5251 (3)	0.14582 (12)	0.47018 (12)	0.0485 (6)
H3B	0.510 (4)	0.1880 (12)	0.4819 (16)	0.065 (12)*
H3C	0.617 (2)	0.1366 (18)	0.4763 (16)	0.053 (12)*
O4	0.2152 (3)	0.17896 (11)	0.42469 (11)	0.0418 (6)
H4A	0.255 (5)	0.2189 (14)	0.4215 (18)	0.083 (15)*
H4B	0.138 (3)	0.186 (2)	0.4457 (15)	0.064 (13)*
O5	−0.1870 (3)	0.10564 (11)	0.49917 (11)	0.0507 (6)
O6	−0.0406 (3)	0.21407 (10)	0.49052 (10)	0.0477 (6)
O7	0.0444 (2)	0.11723 (11)	0.55429 (11)	0.0489 (6)
O8	−0.1713 (3)	0.18740 (11)	0.58315 (10)	0.0462 (6)
O9	0.2042 (4)	−0.29638 (17)	0.59680 (14)	0.0622 (7)
H9B	0.181 (5)	−0.266 (2)	0.5709 (17)	0.098 (19)*
H9C	0.276 (4)	−0.322 (2)	0.585 (2)	0.11 (2)*
O10	0.4462 (3)	−0.13067 (13)	0.37012 (12)	0.0526 (7)
H10B	0.364 (3)	−0.1478 (18)	0.3807 (17)	0.058 (12)*
H10C	0.517 (3)	−0.1578 (17)	0.3807 (17)	0.064 (13)*
N1	0.4532 (3)	0.14220 (13)	0.32942 (12)	0.0395 (6)
N2	0.2607 (3)	0.02928 (13)	0.33596 (11)	0.0393 (6)
C1	0.5427 (4)	0.19903 (18)	0.32636 (17)	0.0527 (9)
H1A	0.5766	0.2192	0.3624	0.063*
C2	0.5894 (5)	0.2305 (2)	0.2722 (2)	0.0665 (11)
H2A	0.6524	0.2706	0.2723	0.080*
C3	0.5416 (5)	0.2017 (2)	0.21981 (19)	0.0653 (12)
H3A	0.5717	0.2222	0.1834	0.078*
C4	0.4469 (4)	0.1412 (2)	0.21946 (16)	0.0544 (10)
C5	0.3928 (5)	0.1063 (3)	0.16657 (18)	0.0749 (13)
H5A	0.4202	0.1243	0.1288	0.090*
C6	0.3043 (5)	0.0490 (3)	0.16963 (18)	0.0757 (13)
H6A	0.2728	0.0271	0.1339	0.091*
C7	0.2553 (4)	0.0194 (2)	0.22651 (17)	0.0560 (10)
C8	0.1618 (5)	−0.0402 (2)	0.2323 (2)	0.0747 (14)
H8A	0.1290	−0.0644	0.1978	0.090*
C9	0.1174 (5)	−0.0639 (2)	0.2878 (2)	0.0704 (13)
H9A	0.0542	−0.1037	0.2917	0.085*
C10	0.1696 (4)	−0.02653 (17)	0.33916 (17)	0.0529 (10)
H10A	0.1381	−0.0421	0.3771	0.063*
C11	0.3055 (4)	0.05242 (17)	0.28009 (14)	0.0412 (8)
C12	0.4046 (4)	0.11317 (17)	0.27664 (14)	0.0397 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Mn	0.0394 (3)	0.0282 (2)	0.0333 (3)	−0.0010 (2)	−0.0008 (2)	−0.00077 (19)
S	0.0338 (5)	0.0247 (4)	0.0502 (5)	0.0001 (3)	0.0057 (4)	−0.0004 (3)
O1	0.0486 (16)	0.0272 (12)	0.0579 (15)	0.0001 (11)	0.0168 (12)	−0.0019 (11)
O2	0.0438 (16)	0.0355 (13)	0.0507 (16)	0.0067 (11)	−0.0067 (12)	−0.0005 (11)
O3	0.0449 (16)	0.0363 (13)	0.0643 (16)	0.0044 (12)	−0.0165 (13)	−0.0145 (12)
O4	0.0381 (15)	0.0295 (12)	0.0578 (15)	−0.0012 (11)	0.0081 (12)	0.0005 (11)
O5	0.0485 (15)	0.0319 (11)	0.0716 (17)	−0.0051 (10)	−0.0082 (13)	−0.0050 (11)
O6	0.0542 (15)	0.0315 (11)	0.0574 (14)	−0.0043 (11)	0.0150 (12)	0.0018 (10)
O7	0.0370 (14)	0.0446 (12)	0.0651 (16)	0.0083 (11)	0.0001 (12)	−0.0003 (11)
O8	0.0491 (15)	0.0337 (11)	0.0558 (14)	0.0064 (10)	0.0200 (12)	−0.0001 (10)
O9	0.0520 (19)	0.0641 (18)	0.070 (2)	−0.0025 (15)	0.0018 (16)	0.0003 (16)
O10	0.0516 (19)	0.0411 (14)	0.0651 (17)	0.0010 (14)	0.0095 (15)	0.0047 (12)
N1	0.0389 (17)	0.0377 (14)	0.0419 (15)	0.0013 (12)	0.0030 (13)	0.0022 (12)
N2	0.0408 (17)	0.0333 (13)	0.0436 (16)	0.0029 (12)	−0.0068 (13)	−0.0017 (12)
C1	0.052 (2)	0.0440 (19)	0.062 (2)	−0.0037 (18)	0.0074 (19)	0.0029 (18)
C2	0.065 (3)	0.058 (2)	0.077 (3)	−0.002 (2)	0.019 (2)	0.019 (2)
C3	0.058 (3)	0.075 (3)	0.063 (3)	0.014 (2)	0.021 (2)	0.029 (2)
C4	0.048 (2)	0.073 (3)	0.042 (2)	0.019 (2)	0.0055 (18)	0.0073 (19)
C5	0.069 (3)	0.117 (4)	0.039 (2)	0.024 (3)	0.002 (2)	0.006 (2)
C6	0.076 (3)	0.113 (4)	0.039 (2)	0.023 (3)	−0.016 (2)	−0.014 (2)
C7	0.047 (2)	0.067 (2)	0.054 (2)	0.014 (2)	−0.0168 (19)	−0.013 (2)
C8	0.072 (3)	0.081 (3)	0.071 (3)	0.014 (3)	−0.031 (2)	−0.032 (2)
C9	0.064 (3)	0.050 (2)	0.098 (4)	−0.011 (2)	−0.029 (3)	−0.013 (2)
C10	0.054 (2)	0.0397 (18)	0.065 (3)	−0.0021 (18)	−0.0127 (19)	0.0000 (17)
C11	0.039 (2)	0.0482 (18)	0.0364 (18)	0.0144 (16)	−0.0076 (15)	−0.0089 (15)
C12	0.036 (2)	0.0463 (18)	0.0371 (18)	0.0121 (16)	0.0000 (15)	0.0022 (15)

Geometric parameters (Å, º)

Mn—O3	2.155 (2)	O10—O9^vi	2.757 (4)
Mn—O4	2.159 (2)	O10—O8^i	2.849 (3)
Mn—O2	2.184 (2)	O10—H10B	0.830 (18)
Mn—O1	2.203 (2)	O10—H10C	0.839 (18)
Mn—N2	2.254 (2)	N1—C1	1.320 (4)
Mn—N1	2.272 (3)	N1—C12	1.355 (4)
S—O8	1.464 (2)	N2—C10	1.313 (4)
S—O7	1.468 (2)	N2—C11	1.366 (4)
S—O5	1.468 (2)	C1—C2	1.394 (5)
S—O6	1.478 (2)	C1—H1A	0.9300
O1—O5^i	2.687 (3)	C2—C3	1.343 (6)
O1—S^i	3.826 (2)	C2—H2A	0.9300
O1—H1B	0.846 (18)	C3—C4	1.400 (5)
O1—H1C	0.89 (4)	C3—H3A	0.9300
O2—O1^ii	3.000 (4)	C4—C12	1.417 (5)
O2—H2B	0.825 (18)	C4—C5	1.419 (6)
O2—H2C	0.835 (19)	C5—C6	1.322 (6)
O3—O5^iii	2.736 (3)	C5—H5A	0.9300
O3—O6^iv	2.797 (3)	C6—C7	1.438 (6)
O3—H3B	0.832 (18)	C6—H6A	0.9300
O3—H3C	0.842 (18)	C7—C8	1.387 (6)
O4—O8^iv	2.676 (3)	C7—C11	1.405 (4)
O4—S^iv	3.642 (2)	C8—C9	1.362 (6)
O4—H4A	0.823 (19)	C8—H8A	0.9300
O4—H4B	0.835 (18)	C9—C10	1.407 (5)
O9—O6^i	2.855 (4)	C9—H9A	0.9300
O9—O7^v	2.900 (4)	C10—H10A	0.9300
O9—H9B	0.831 (19)	C11—C12	1.429 (5)
O9—H9C	0.831 (19)
O3—Mn—O4	87.74 (9)	H4A—O4—H4B	105 (4)
O3—Mn—O2	86.73 (10)	O6^i—O9—O7^v	117.77 (12)
O4—Mn—O2	168.42 (9)	O6^i—O9—H9B	17 (3)
O3—Mn—O1	97.90 (10)	O7^v—O9—H9B	110 (3)
O4—Mn—O1	86.43 (9)	O6^i—O9—H9C	119 (3)
O2—Mn—O1	84.26 (9)	O7^v—O9—H9C	1 (4)
O3—Mn—N2	161.76 (10)	H9B—O9—H9C	111 (5)
O4—Mn—N2	101.51 (9)	O9^vi—O10—O8^i	115.73 (12)
O2—Mn—N2	86.68 (9)	O9^vi—O10—H10B	118 (3)
O1—Mn—N2	98.33 (9)	O8^i—O10—H10B	5 (3)
O3—Mn—N1	91.67 (10)	O9^vi—O10—H10C	8 (3)
O4—Mn—N1	87.24 (9)	O8^i—O10—H10C	109 (3)
O2—Mn—N1	103.08 (9)	H10B—O10—H10C	111 (4)
O1—Mn—N1	168.30 (10)	C1—N1—C12	117.6 (3)
N2—Mn—N1	73.33 (10)	C1—N1—Mn	126.8 (2)
O8—S—O7	109.81 (14)	C12—N1—Mn	115.5 (2)
O8—S—O5	109.78 (14)	C10—N2—C11	118.3 (3)
O7—S—O5	109.45 (13)	C10—N2—Mn	126.3 (2)
O8—S—O6	109.57 (12)	C11—N2—Mn	115.2 (2)
O7—S—O6	109.24 (14)	N1—C1—C2	123.8 (4)
O5—S—O6	108.97 (14)	N1—C1—H1A	118.1
Mn—O1—O5^i	125.74 (11)	C2—C1—H1A	118.1
Mn—O1—S^i	119.59 (9)	C3—C2—C1	118.7 (4)
O5^i—O1—S^i	16.62 (6)	C3—C2—H2A	120.6
Mn—O1—H1B	123 (2)	C1—C2—H2A	120.6
O5^i—O1—H1B	108 (2)	C2—C3—C4	120.8 (3)
S^i—O1—H1B	106 (2)	C2—C3—H3A	119.6
Mn—O1—H1C	126 (2)	C4—C3—H3A	119.6
O5^i—O1—H1C	6 (2)	C3—C4—C12	116.6 (3)
S^i—O1—H1C	11 (2)	C3—C4—C5	124.9 (4)
H1B—O1—H1C	106 (3)	C12—C4—C5	118.6 (4)
Mn—O2—O1^ii	131.43 (11)	C6—C5—C4	121.6 (4)
Mn—O2—H2B	131 (2)	C6—C5—H5A	119.2
O1^ii—O2—H2B	2 (2)	C4—C5—H5A	119.2
Mn—O2—H2C	119 (3)	C5—C6—C7	122.0 (4)
O1^ii—O2—H2C	108 (3)	C5—C6—H6A	119.0
H2B—O2—H2C	107 (4)	C7—C6—H6A	119.0
Mn—O3—O5^iii	127.63 (11)	C8—C7—C11	117.3 (4)
Mn—O3—O6^iv	120.01 (12)	C8—C7—C6	124.3 (4)
O5^iii—O3—O6^iv	111.96 (10)	C11—C7—C6	118.4 (4)
Mn—O3—H3B	123 (3)	C9—C8—C7	120.8 (4)
O5^iii—O3—H3B	109 (3)	C9—C8—H8A	119.6
O6^iv—O3—H3B	3 (3)	C7—C8—H8A	119.6
Mn—O3—H3C	129 (2)	C8—C9—C10	118.3 (4)
O5^iii—O3—H3C	6 (2)	C8—C9—H9A	120.8
O6^iv—O3—H3C	110 (2)	C10—C9—H9A	120.8
H3B—O3—H3C	107 (4)	N2—C10—C9	123.1 (4)
Mn—O4—O8^iv	118.78 (11)	N2—C10—H10A	118.5
Mn—O4—S^iv	112.70 (9)	C9—C10—H10A	118.5
O8^iv—O4—S^iv	20.31 (5)	N2—C11—C7	122.2 (3)
Mn—O4—H4A	115 (3)	N2—C11—C12	118.3 (3)
O8^iv—O4—H4A	4 (3)	C7—C11—C12	119.5 (3)
S^iv—O4—H4A	21 (3)	N1—C12—C4	122.6 (3)
Mn—O4—H4B	133 (3)	N1—C12—C11	117.5 (3)
O8^iv—O4—H4B	101 (3)	C4—C12—C11	119.9 (3)
S^iv—O4—H4B	96 (3)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1B···O7	0.85 (3)	1.85 (3)	2.692 (3)	172 (3)
O2—H2C···O10	0.83 (3)	1.85 (3)	2.678 (3)	175 (3)
O4—H4B···O6	0.84 (3)	1.94 (3)	2.773 (4)	173 (3)
O1—H1C···O5^i	0.90 (4)	1.80 (4)	2.687 (3)	171 (4)
O2—H2B···O1^ii	0.82 (3)	2.18 (3)	3.000 (4)	177 (3)
O3—H3C···O5^iii	0.84 (2)	1.90 (2)	2.736 (4)	171 (2)
O3—H3B···O6^iv	0.83 (2)	1.96 (2)	2.797 (3)	176 (2)
O4—H4A···O8^iv	0.82 (3)	1.86 (3)	2.677 (3)	175 (3)
O9—H9B···O6^i	0.83 (4)	2.08 (4)	2.855 (4)	156 (4)
O9—H9C···O7^v	0.84 (4)	2.06 (4)	2.901 (4)	178 (4)
O10—H10B···O8^i	0.83 (3)	2.02 (3)	2.849 (4)	173 (3)
O10—H10C···O9^vi	0.84 (3)	1.93 (3)	2.756 (4)	169 (3)

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