A magnesium(II) complex of 1,10-phenanthroline-2,9-di­carboxyl­ate

The title compound, tri­aqua(1,10-phenanthroline-2,9-di­car­box­yl­ato)­magnesium(II) dihydrate, [Mg(PDA)(H₂O)₃]·2H₂O, (H₂PDA is 1,10-phenanthroline-2,9-di­carboxyl­ic acid, C₁₄H₈N₂O₄) has twofold crystallographic symmetry. The Mg atom is in a distorted pentagonal bipyramidal coordination environment with two N atoms and two O atoms from PDA and one O atom from a water mol­ecule forming the pentagonal plane, and two O atoms from two water mol­ecules occupying axial positions. The crystal structure comprises an infinite two-dimensional network of hydrogen-bonded mol­ecules.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.004 Å
• H-atom completeness 76%
• Disorder in solvent or counterion
• R factor = 0.055
• wR factor = 0.186
• Data-to-parameter ratio = 16.0

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



PLAT_302  Alert C Anion/Solvent Disorder .......................      50.00 Perc.

General Notes



FORMU_01  There is a discrepancy between the atom counts in the
          _chemical_formula_sum and the formula from the _atom_site* data.
          Atom count from _chemical_formula_sum:C14 H16 Mg1 N2 O9
          Atom count from the _atom_site data:  C14 H12 Mg1 N2 O9

CELLZ_01
         From the CIF: _cell_formula_units_Z   16
         From the CIF: _chemical_formula_sum  C14 H16 Mg N2 O9
         TEST: Compare cell contents of formula and atom_site data

         atom    Z*formula  cif sites diff
         C        224.00    224.00    0.00
         H        256.00    192.00   64.00
         Mg        16.00     16.00    0.00
         N         32.00     32.00    0.00
         O        144.00    144.00    0.00
          Difference between formula and atom_site contents detected.
          WARNING: H atoms missing from atom site list. Is this intentional?

CHEMW_03
         From the CIF: _cell_formula_units_Z                   16
         From the CIF: _chemical_formula_weight           380.60
         TEST: Calculate formula weight from _atom_site_*
         atom     mass    num     sum
         C        12.01   14.00  168.15
         H         1.01   12.00   12.10
         N        14.01    2.00   28.01
         O        16.00    9.00  143.99
         Mg       24.31    1.00   24.31
         Calculated formula weight              376.56
          The ratio of given/expected molecular weight as calculated
          from the _atom_site* data lies outside
          the range 0.99 <> 1.01


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

---

S1. Comment

1,10-Phenanthroline-2,9-dicarboxylic acid (H₂PDA) has been used as a simple sensitizing species of luminescent lanthanide ion chelates for analytical applications in aqueous solution (Sammes & Yahioglu, 1994; Mullins et al., 1996). However, investigations of H₂PDA complexes with metal ions, such as Fe^II and Eu^II, have been limited to spectroscopic characterizations in aqueous solution (König & Ritter, 1981; Templeton & Pollak, 1989; Sammes et al., 1992; Dyson et al., 1999). To our knowledge, no examples of Mg^II complexes of H₂PDA have been characterized in the solid state. We have prepared the Mg^II complex of H₂PDA, (I), and report its the crystal structure here.

The title compound (Fig. 1) is located on a twofold axis of symmetry which passes through the Mg and O3 atoms. The seven-coordinated Mg atom is in a distorted pentagonal bipyramidal geometry. Two N and two O atoms from PDA and one O atom from a water molecule define the pentagonal plane, and the two axial positions are occupied by O atoms derived from two water molecules.

Important bond distances and angles are presented in Table 1. The bond distances between Mg and the PDA donor atoms [Mg—O1 2.3080 (17) Å and Mg—N1 2.2994 (19) Å] are significantly longer than those to the coordinated water molecules [Mg—O3 2.055 (2) Å and Mg—O4 2.0777 (18) Å]. This is probably due to the high rigidity of PDA as well as the high affinity of the Mg^II ion to water molecules. The carboxylate groups of the PDA ligand are almost coplanar with the phenanthroline unit as indicated by the O1—C1—C2—N1 torsion angle of 1.9 (3)°.

The complexes are inter-connected by hydrogen bonds between the coordinated water molecules, O3 and O4, and the carboxylate O atoms of adjacent PDA with interaction distances of 2.774 (2) and 2.745 (3) Å (Table 2); the equatorial water molecule is hydrogen bonded with the coordinated carboxylate O atoms and the axial water molecules interact with the carbonyl O atoms.

As illustrated in Fig. 2, the complexes associate along the a axis and form columns in the crystal structure. Non-coordinated water molecules also participate in hydrogen bonds and serve to connect the complex units along the b axis. Stacking interactions between centrosymmetrically related phenanthroline units are observed with a plane-to-plane separation of 3.360 (4) Å.

S2. Experimental

H₂PDA was synthesized according to the literature (König et al., 1981). The title compound was crystallized by slow evaporation from the methanol solution prepared by the reaction of equimolar amounts of H₂PDA and MgSO₄.

S3. Refinement

The C—H atoms were added at their calculated positions [U_iso= 1.2U_eq(C)] and refined using a riding model. The H atoms of the coordinated water molecules were located from a difference map but were not refined. The non-coordinated water molecule, O5, is disordered over two sites with occupancies of 0.7 for O5 and 0.3 for O5'; H atoms were not included for this molecule.

Computing details

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

Figures

	Fig. 1. The structure of the title compound with the atom-numbering scheme. The displacement ellipsoids are drawn at the 50% probability level (Johnson, 1976). The non-coordinated water molecule has been omitted for clarity. [Symmetry code: (i) -x + 3/4, -y + 3/4, z].
	Fig. 2. Packing diagram of (I) viewed along [100]. Hydrogen bonds are indicated by dashed lines. Displacement ellipsoids are shown at the 30% probability level. All H atoms and the disordered water molecules with lower site occupancy have been omitted for clarity.

Triaqua(1,10-phenanthroline-2,9-dicarboxylato)magnesium(II) dihydrate

Crystal data

[Mg(C14H6N2O4)(H2O)3]·2H2O	F(000) = 3168
Mr = 380.60	Dx = 1.525 Mg m^−3
Orthorhombic, Fddd	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -F 2uv 2vw	Cell parameters from 10406 reflections
a = 7.4194 (12) Å	θ = 1.7–28.3°
b = 19.044 (3) Å	µ = 0.16 mm^−1
c = 46.943 (7) Å	T = 293 K
V = 6632.8 (18) Å^3	Plate, yellow
Z = 16	0.2 × 0.2 × 0.15 mm

Data collection

CCD area detector diffractometer	1385 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.066
Graphite monochromator	θmax = 28.3°, θmin = 1.7°
ϕ and ω scans	h = −9→9
10406 measured reflections	k = −25→25
2063 independent reflections	l = −62→42

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)] = 0.055	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.186	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	w = 1/[σ^2(Fo^2) + (0.1026P)^2 + 8.6902P] where P = (Fo^2 + 2Fc^2)/3
2063 reflections	(Δ/σ)max < 0.001
129 parameters	Δρmax = 0.32 e Å^−3
0 restraints	Δρmin = −0.31 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	Occ. (<1)
Mg	0.3750	0.3750	0.07737 (2)	0.0375 (3)
O1	0.6448 (2)	0.42950 (10)	0.08789 (3)	0.0469 (5)
O2	0.8903 (3)	0.48671 (12)	0.07265 (4)	0.0602 (6)
O3	0.3750	0.3750	0.12114 (5)	0.0519 (7)
O4	0.2576 (2)	0.47404 (10)	0.07751 (4)	0.0478 (5)
N1	0.5316 (2)	0.40521 (10)	0.03692 (4)	0.0373 (5)
C1	0.7482 (3)	0.45259 (13)	0.06867 (5)	0.0417 (6)
C2	0.6882 (3)	0.43836 (12)	0.03842 (5)	0.0394 (5)
C3	0.7830 (4)	0.45897 (14)	0.01391 (6)	0.0492 (6)
H3	0.8952	0.4837	0.0156	0.059*
C4	0.7149 (4)	0.44364 (14)	−0.01242 (5)	0.0522 (7)
H4	0.7805	0.4564	−0.0293	0.063*
C5	0.5475 (4)	0.40896 (13)	−0.01468 (5)	0.0453 (6)
C6	0.4568 (4)	0.39108 (14)	−0.04074 (5)	0.0567 (7)
H6	0.5132	0.4021	−0.0586	0.068*
C7	0.4614 (3)	0.39150 (12)	0.01097 (4)	0.0386 (5)
O5	0.4235 (18)	0.5506 (3)	0.12298 (12)	0.061 (2)	0.69 (4)
O5'	0.327 (9)	0.5534 (8)	0.1265 (4)	0.100 (10)	0.31 (4)
H3A	0.2856	0.3532	0.1341	0.050*
H4A	0.1426	0.4775	0.0769	0.050*
H4B	0.2937	0.4967	0.0939	0.050*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Mg	0.0400 (6)	0.0452 (6)	0.0273 (5)	0.0001 (5)	0.000	0.000
O1	0.0417 (10)	0.0646 (12)	0.0345 (9)	−0.0086 (8)	−0.0030 (7)	0.0076 (7)
O2	0.0427 (10)	0.0702 (13)	0.0677 (13)	−0.0095 (9)	−0.0055 (9)	0.0103 (10)
O3	0.0543 (15)	0.0739 (17)	0.0276 (11)	−0.0216 (13)	0.000	0.000
O4	0.0427 (9)	0.0532 (10)	0.0475 (10)	0.0020 (8)	0.0007 (7)	−0.0011 (8)
N1	0.0371 (10)	0.0446 (10)	0.0304 (9)	0.0039 (8)	0.0015 (7)	0.0030 (8)
C1	0.0314 (11)	0.0484 (13)	0.0454 (13)	0.0018 (10)	−0.0024 (9)	0.0080 (10)
C2	0.0381 (12)	0.0423 (12)	0.0376 (11)	0.0056 (9)	0.0044 (9)	0.0071 (9)
C3	0.0463 (14)	0.0521 (15)	0.0491 (15)	0.0012 (12)	0.0115 (11)	0.0105 (11)
C4	0.0635 (17)	0.0546 (15)	0.0385 (13)	0.0087 (13)	0.0172 (11)	0.0113 (11)
C5	0.0612 (16)	0.0431 (13)	0.0315 (11)	0.0127 (12)	0.0074 (10)	0.0060 (9)
C6	0.084 (2)	0.0564 (17)	0.0297 (11)	0.0152 (14)	0.0076 (11)	0.0045 (10)
C7	0.0470 (13)	0.0394 (12)	0.0294 (10)	0.0102 (9)	0.0030 (9)	0.0028 (8)
O5	0.070 (5)	0.0518 (19)	0.060 (2)	0.003 (2)	0.006 (2)	−0.0002 (17)
O5'	0.14 (3)	0.063 (6)	0.096 (8)	−0.017 (9)	0.001 (11)	−0.028 (6)

Geometric parameters (Å, º)

Mg—O3	2.055 (2)	N1—C7	1.350 (3)
Mg—O4^i	2.0777 (18)	C1—C2	1.513 (3)
Mg—O4	2.0777 (18)	C2—C3	1.405 (3)
Mg—N1	2.2994 (19)	C3—C4	1.367 (4)
Mg—N1^i	2.2994 (19)	C4—C5	1.411 (4)
Mg—O1^i	2.3080 (16)	C5—C7	1.403 (3)
Mg—O1	2.3080 (17)	C5—C6	1.437 (4)
O1—C1	1.263 (3)	C6—C6^i	1.360 (6)
O2—C1	1.252 (3)	C7—C7^i	1.428 (5)
N1—C2	1.324 (3)	O5—O5'	0.74 (5)
O3—Mg—O4^i	89.81 (5)	O1^i—Mg—O1	155.30 (9)
O3—Mg—O4	89.81 (5)	C1—O1—Mg	122.05 (15)
O4^i—Mg—O4	179.63 (11)	C2—N1—C7	118.61 (19)
O3—Mg—N1	145.68 (5)	C2—N1—Mg	121.23 (14)
O4^i—Mg—N1	91.03 (7)	C7—N1—Mg	120.12 (15)
O4—Mg—N1	89.28 (7)	O2—C1—O1	125.8 (2)
O3—Mg—N1^i	145.68 (5)	O2—C1—C2	118.7 (2)
O4^i—Mg—N1^i	89.28 (7)	O1—C1—C2	115.4 (2)
O4—Mg—N1^i	91.03 (7)	N1—C2—C3	121.9 (2)
N1—Mg—N1^i	68.64 (10)	N1—C2—C1	113.18 (18)
O3—Mg—O1^i	77.65 (5)	C3—C2—C1	124.9 (2)
O4^i—Mg—O1^i	87.41 (7)	C4—C3—C2	119.7 (3)
O4—Mg—O1^i	92.51 (7)	C3—C4—C5	119.6 (2)
N1—Mg—O1^i	136.66 (7)	C7—C5—C4	116.6 (2)
N1^i—Mg—O1^i	68.03 (6)	C7—C5—C6	117.5 (3)
O3—Mg—O1	77.65 (5)	C4—C5—C6	125.9 (2)
O4^i—Mg—O1	92.51 (7)	C6^i—C6—C5	121.63 (16)
O4—Mg—O1	87.41 (7)	N1—C7—C5	123.6 (2)
N1—Mg—O1	68.04 (6)	N1—C7—C7^i	115.56 (13)
N1^i—Mg—O1	136.66 (7)	C5—C7—C7^i	120.87 (15)
O1—C1—C2—N1	1.9 (3)	O2—C1—C2—C3	1.9 (4)

Symmetry code: (i) −x+3/4, −y+3/4, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3A···O1^ii	0.991 (1)	1.791 (2)	2.774 (2)	170.6 (1)
O4—H4A···O2^iii	0.856 (2)	1.891 (2)	2.745 (3)	175.8 (1)
O4—H4B···O5	0.922 (2)	1.960 (7)	2.863 (6)	165.7 (4)
O4—H4B···O5′	0.922 (2)	1.89 (1)	2.80 (1)	169 (2)
O5···O2^iv			2.866 (7)
O5′···O2^iv			2.71 (2)
O5···O5^v			2.84 (1)
O5′···O5′^v			2.73 (3)

Symmetry codes: (ii) x−1/2, −y+3/4, −z+1/4; (iii) x−1, y, z; (iv) −x+5/4, y, −z+1/4; (v) x, −y+5/4, −z+1/4.