catena-Poly[[(1,10-phenanthroline-[kappa]²N,N')manganese(II)]-di-[mu]-salicylato-[kappa]⁴O:O']

In the title polymeric complex, [Mn(C₇H₅O₃)₂(C₁₂H₈N₂)]_n, the Mn^II atom is located on a twofold axis and displays a distorted octa­hedral coordination geometry, formed by four salicylate anions and one 1,10-phenanthroline (phen) mol­ecule. The salicylate anions doubly bridge the Mn^II atoms to form one-dimensional polymeric chains. A comparison of Mn-O bond distances with the corresponding Mn-O-C angles suggests a significant electrostatic content in the Mn-O bonds. A face-to-face distance of 3.352 (7) Å between neighbouring parallel phen planes indicates [pi]-[pi] stacking inter­actions between polymeric chains.

S1. Comment

The structure and properties of multinuclear Mn complexes have attracted much scientific attention, due to their potentially useful electronic or magnetic properties and their presence in various biosystems (Yachandra et al., 1996), especially in the oxygen-evolving complex of photosystem II (PSII). The process of water splitting is generally believed to occur at an Mn cluster located in the reaction centre of PSII (Vincent & Christou, 1989). In order to mimic the Mn cluster, a series of Mn complexes have been synthesized and their crystal structures have been determined in our laboratory (Xu et al., 1997; Li et al., 2002; Su et al., 2004). Among these, the X-ray structures of several Mn^II complexes showed evidence for significant electrostatic content in the coordination bond between the Mn^II atom and the ligand (Nie et al., 2001; Liu et al., 2003), which may play an important role for oxygen release during photosynthesis. As part of our ongoing investigation, the title polymeric Mn^II complex, (I), has been prepared and its structure has been determined.

A segment of the polymeric structure of (I) is illustrated in Fig. 1. The Mn^II atom is located on a twofold axis and is coordinated by four salicylate anions and one phenanthroline (phen) molecule, with a distorted octahedral coordination geometry. The phen ligand lies on a twofold axis and chelates to the Mn^II with normal bond distances and angles. Crystallographically independent salicylate anions coordinate to the Mn^II atom with appreciably different Mn—O bond distances and Mn—O—C bond angles (Table 1). It is noteworthy that the shorter Mn—O1 bond corresponds to the larger Mn—O1—C1 bond angle, whereas the longer Mn—O2ⁱ bond corresponds to the smaller (normal) Mn—O2ⁱ—C1ⁱ bond angle [symmetry code: (i) 1 − x, 1 − y, 1 − z].

A similar situation is also observed in some reported Mn^II complexes incorporating non-chelating carboxylates. The Mn—O(carboxyl) bond distances and corresponding Mn—O—C bond angles found in those Mn^II complexes are summarized in Table 3. In these structures, the Mn—O—C bond angles range from 121.1 (2) to 170.10 (6)° and the Mn—O bond distances range from 2.050 (4) to 2.278 (2) Å. A comparison of the bond distances with the bond angles shows that the Mn—O bond distances are independent of the corresponding Mn—O—C bond angles. In some structures, even though the larger Mn—O—C bond angles imply poor overlap between the atomic orbitals of the Mn and the molecular orbitals of the ligand, the shorter Mn—O bond distances indicate a stronger interaction between them. This finding strongly suggests the existence of the significant electrostatic content in the Mn—O(carboxyl) bonds.

The salicylate anions play the role of bridging ligand in (I). Neighbouring Mn^II atoms are bridged by two salicylate anions to form zigzag polymeric chains along the c axis, as shown in Fig. 2. The polymeric chain has a repeat unit formed by two salicylate anions and two Mn^II atoms related by an inversion centre. The repeat unit of the eight-membered ring assumes a chair configuration, with the Mn atoms deviating from the basal plane formed by two carboxyl groups by 0.856 (3) Å. The Mn···Mn separation in the eight-membered ring is 4.8252 (5) Å.

A parallel arrangement of the phen ligands of neighbouring polymeric chains is illustrated in Fig. 2. The face-to-face distance of 3.352 (7) Å between parallel N11-phen and N11^iv-phen planes [symmetry code: (iv) 1 − x, 2 − y, 1 − z] and a partially overlapped arrangement (Fig. 3) suggest a π–π interaction. The shortest distance between the centroids of the aromatic rings of neighbouring phen ligands is 3.8384 (12) Å.

The hydroxyl group of the salicylate is free from coordination in (I), which differs from the situation found in [Cu(C₇H₅O₃)₂(C₇H₆N₂)₂]_n (Li et al., 2005). However, the hydroxyl group is involved in an intramolecular hydrogen bond with the carboxyl O atom (Table 2), which also forms weak C—H···O hydrogen bonds, both with the phen ligands (Fig. 2) and with salicylate anions of adjacent polymeric chains.

S2. Experimental

Each reagent was commercially available and of analytical grade. Mn(CH₃COO)₂·4H₂O (0.25 g, 1 mmol), salicylic acid (0.14 g, 1 mmol), 1,10-phenanthroline (0.20 g, 1 mmol) and Na₂CO₃ (0.05 g, 1 mmol) were dissolved in a water–ethanol solution (20 ml, 1:1). The solution was refluxed for 5 h, then cooled to room temperature and filtered. Pale-yellow single crystals of (I) were obtained from the filtrate after 3 d.

S3. Refinement

The hydroxyl H atom was located in a difference Fourier map and refined riding in its as-found position, with a fixed isotropic displacement parameter of 0.05 Ų. Aromatic H atoms were placed in calculated positions, with C—H = 0.93 Å, and were included in the final cycles of refinement in riding mode, with U_iso(H) = 1.2U_eq(C).

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); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. A segment of the polymeric structure of (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms have been omitted for clarity. [Symmetry codes: (i) 1 − x, 1 − y, 1 − z; (ii) 1 − x, y, 1/2 − z; (iii) x, 1 − y, z − 1/2.]
	Fig. 2. A unit-cell packing diagram for (I), showing the parallel arrangement of the phen rings and the interchain C—H···O hydrogen bonds (dashed lines).
	Fig. 3. The π–π stacking between the phen rings of (I). [Symmetry code: (iv) 1 − x, 2 − y, 1 − z.]

Poly[bis(µ-salicylato-κ²O:O')(1,10-phenanthroline-κ²N,N')manganese(II)]

Crystal data

[Mn(C7H5O3)2(C12H8N2)]	F(000) = 1044
Mr = 509.36	Dx = 1.540 Mg m^−3
Orthorhombic, Pbcn	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: -P 2n 2ab	Cell parameters from 10105 reflections
a = 23.5785 (5) Å	θ = 2.7–24.4°
b = 12.1715 (3) Å	µ = 0.65 mm^−1
c = 7.6545 (2) Å	T = 295 K
V = 2196.73 (9) Å^3	Platelet, pale yellow
Z = 4	0.20 × 0.18 × 0.03 mm

Data collection

Rigaku R-AXIS RAPID diffractometer	1965 independent reflections
Radiation source: fine-focus sealed tube	1544 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.043
Detector resolution: 10.0 pixels mm^-1	θmax = 25.2°, θmin = 1.7°
ω scans	h = −28→28
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	k = −14→14
Tmin = 0.875, Tmax = 0.976	l = −9→8
13706 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)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.081	H-atom parameters constrained
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0411P)^2 + 0.6755P] where P = (Fo^2 + 2Fc^2)/3
1965 reflections	(Δ/σ)max = 0.001
159 parameters	Δρmax = 0.21 e Å^−3
0 restraints	Δρmin = −0.24 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
Mn	0.5000	0.62071 (3)	0.2500	0.03329 (15)
O1	0.55843 (6)	0.52049 (12)	0.3759 (2)	0.0561 (5)
O2	0.55714 (6)	0.36152 (11)	0.5183 (2)	0.0417 (4)
O3	0.63914 (7)	0.22927 (12)	0.4902 (3)	0.0570 (5)
H3	0.6077	0.2608	0.5350	0.050*
N11	0.45111 (7)	0.77275 (13)	0.1565 (2)	0.0347 (4)
C1	0.57995 (9)	0.43099 (16)	0.4165 (3)	0.0362 (5)
C2	0.63737 (8)	0.40402 (16)	0.3457 (3)	0.0349 (5)
C3	0.66428 (9)	0.30514 (18)	0.3867 (3)	0.0412 (5)
C4	0.71836 (11)	0.2837 (2)	0.3206 (4)	0.0616 (8)
H4	0.7360	0.2172	0.3455	0.074*
C5	0.74537 (11)	0.3598 (3)	0.2197 (4)	0.0726 (9)
H5	0.7815	0.3451	0.1773	0.087*
C6	0.71973 (11)	0.4581 (3)	0.1799 (4)	0.0707 (9)
H6	0.7385	0.5096	0.1112	0.085*
C7	0.66629 (10)	0.4799 (2)	0.2422 (3)	0.0526 (6)
H7	0.6491	0.5465	0.2149	0.063*
C12	0.40254 (9)	0.77245 (17)	0.0693 (3)	0.0423 (6)
H12	0.3875	0.7053	0.0343	0.051*
C13	0.37291 (10)	0.86805 (19)	0.0274 (3)	0.0475 (6)
H13	0.3385	0.8641	−0.0318	0.057*
C14	0.39489 (10)	0.96747 (18)	0.0743 (3)	0.0453 (6)
H14	0.3754	1.0318	0.0480	0.054*
C15	0.44694 (9)	0.97203 (15)	0.1623 (3)	0.0363 (5)
C16	0.47493 (10)	1.07284 (16)	0.2089 (3)	0.0437 (6)
H16	0.4578	1.1395	0.1814	0.052*
C17	0.47352 (9)	0.87126 (15)	0.2032 (3)	0.0308 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Mn	0.0269 (2)	0.0251 (2)	0.0479 (3)	0.000	0.0033 (2)	0.000
O1	0.0443 (9)	0.0456 (9)	0.0783 (13)	0.0173 (8)	0.0091 (10)	0.0191 (9)
O2	0.0358 (8)	0.0374 (7)	0.0520 (10)	0.0035 (6)	0.0111 (8)	0.0067 (7)
O3	0.0481 (10)	0.0381 (8)	0.0849 (14)	0.0135 (7)	−0.0007 (9)	0.0049 (9)
N11	0.0313 (10)	0.0323 (9)	0.0406 (12)	−0.0020 (7)	0.0020 (8)	−0.0002 (8)
C1	0.0321 (12)	0.0355 (11)	0.0410 (14)	0.0056 (9)	−0.0005 (10)	−0.0004 (10)
C2	0.0275 (11)	0.0443 (12)	0.0330 (13)	0.0048 (9)	−0.0016 (10)	−0.0018 (9)
C3	0.0355 (12)	0.0468 (12)	0.0412 (15)	0.0085 (10)	−0.0047 (11)	−0.0077 (11)
C4	0.0420 (15)	0.0817 (19)	0.0610 (19)	0.0293 (14)	−0.0052 (14)	−0.0156 (16)
C5	0.0344 (14)	0.133 (3)	0.050 (2)	0.0184 (16)	0.0088 (13)	−0.0093 (19)
C6	0.0399 (15)	0.122 (3)	0.0496 (18)	−0.0031 (16)	0.0119 (13)	0.0162 (18)
C7	0.0405 (13)	0.0714 (16)	0.0458 (16)	0.0021 (12)	0.0030 (13)	0.0135 (13)
C12	0.0372 (13)	0.0409 (12)	0.0488 (16)	−0.0020 (10)	−0.0022 (11)	−0.0017 (10)
C13	0.0381 (13)	0.0544 (14)	0.0500 (16)	0.0049 (11)	−0.0051 (11)	0.0041 (12)
C14	0.0439 (14)	0.0450 (13)	0.0470 (15)	0.0132 (10)	0.0038 (11)	0.0076 (11)
C15	0.0440 (13)	0.0319 (11)	0.0332 (13)	0.0059 (9)	0.0058 (11)	0.0032 (9)
C16	0.0588 (14)	0.0292 (10)	0.0430 (15)	0.0068 (9)	0.0082 (12)	0.0025 (9)
C17	0.0351 (10)	0.0290 (9)	0.0282 (12)	0.0002 (8)	0.0080 (9)	0.0011 (8)

Geometric parameters (Å, º)

Mn—O1	2.0774 (15)	C4—H4	0.9300
Mn—O2^i	2.2375 (15)	C5—C6	1.374 (4)
Mn—N11	2.2946 (17)	C5—H5	0.9300
Mn—O2^ii	2.2375 (15)	C6—C7	1.373 (3)
Mn—O1^iii	2.0774 (15)	C6—H6	0.9300
Mn—N11^iii	2.2946 (17)	C7—H7	0.9300
O1—C1	1.241 (2)	C12—C13	1.395 (3)
O2—C1	1.270 (3)	C12—H12	0.9300
O2—Mn^i	2.2375 (15)	C13—C14	1.364 (3)
O3—C3	1.353 (3)	C13—H13	0.9300
O3—H3	0.9027	C14—C15	1.401 (3)
N11—C12	1.326 (3)	C14—H14	0.9300
N11—C17	1.358 (2)	C15—C17	1.413 (3)
C1—C2	1.495 (3)	C15—C16	1.438 (3)
C2—C7	1.395 (3)	C16—C16^iii	1.339 (5)
C2—C3	1.396 (3)	C16—H16	0.9300
C3—C4	1.397 (3)	C17—C17^iii	1.440 (4)
C4—C5	1.365 (4)
O1—Mn—O1^iii	108.08 (9)	C4—C5—C6	120.8 (2)
O1—Mn—O2^ii	91.44 (6)	C4—C5—H5	119.6
O1—Mn—O2^i	95.07 (6)	C6—C5—H5	119.6
O2^ii—Mn—O2^i	168.90 (7)	C7—C6—C5	119.7 (3)
O1—Mn—N11	162.07 (7)	C7—C6—H6	120.2
O1—Mn—N11^iii	89.76 (6)	C5—C6—H6	120.2
O2^ii—Mn—N11	88.71 (6)	C6—C7—C2	121.2 (2)
O2^i—Mn—N11	82.33 (6)	C6—C7—H7	119.4
N11—Mn—N11^iii	72.49 (8)	C2—C7—H7	119.4
Mn—O1—C1	154.50 (16)	N11—C12—C13	123.1 (2)
C1—O2—Mn^i	132.62 (13)	N11—C12—H12	118.4
C3—O3—H3	107.0	C13—C12—H12	118.4
C12—N11—C17	118.10 (18)	C14—C13—C12	119.3 (2)
C12—N11—Mn	126.07 (14)	C14—C13—H13	120.4
C17—N11—Mn	115.76 (14)	C12—C13—H13	120.4
O1—C1—O2	124.4 (2)	C13—C14—C15	119.6 (2)
O1—C1—C2	118.18 (19)	C13—C14—H14	120.2
O2—C1—C2	117.38 (17)	C15—C14—H14	120.2
C7—C2—C3	118.4 (2)	C14—C15—C17	117.44 (19)
C7—C2—C1	120.20 (19)	C14—C15—C16	123.73 (19)
C3—C2—C1	121.30 (19)	C17—C15—C16	118.8 (2)
O3—C3—C2	121.4 (2)	C16^iii—C16—C15	121.45 (13)
O3—C3—C4	119.0 (2)	C16^iii—C16—H16	119.3
C2—C3—C4	119.7 (2)	C15—C16—H16	119.3
C5—C4—C3	120.3 (3)	N11—C17—C15	122.4 (2)
C5—C4—H4	119.9	N11—C17—C17^iii	117.92 (11)
C3—C4—H4	119.9	C15—C17—C17^iii	119.68 (13)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3···O2	0.90	1.71	2.525 (2)	148
C5—H5···O3^iv	0.93	2.52	3.417 (3)	161
C14—H14···O3^v	0.93	2.45	3.323 (3)	157

Symmetry codes: (iv) −x+3/2, −y+1/2, z−1/2; (v) −x+1, y+1, −z+1/2.