In the title compound, [Sr(C
7H
5O
3)
2(C
12H
8N
2)
2(H
2O)
2], the Sr
II ion is located on a twofold rotation axis and assumes a distorted square-antiprism SrN
4O
4 coordination geometry, formed by two phenanthroline (phen) ligands, two 2-hydroxybenzoate anions and two water molecules. Within the mononuclear complex molecule, intramolecular π–π stacking is observed between nearly parallel coordinated phen ligands, while normal intermolecular π–π stacking occurs between parallel phen ligands of adjacent complex molecules. Classic O—H
O and weak C—H
O hydrogen bonding helps to stabilize the crystal structure.
Supporting information
CCDC reference: 672431
A water–ethanol solution (20 ml, 1:1 v/v) containing SrCO3
(0.15 g, 1 mmol), 2-hydroxybenzoic acid (0.27 g, 2 mmol) and Na2CO3 (0.05 g, 0.5 mmol) was refluxed for 0.5 h. Then phen (0.20 g, 1 mmol) was added to
the solution and the mixture was refluxed for a further 4 h. After cooling to
room temperature, the solution was filtered and the filtrate was kept at room
temperature. Single crystals of (I) were obtained from the filtrate after 3 d.
Water H atoms and hydroxy H atoms were located in a difference Fourier map and
refined as riding in their as-found relative positions, with Uiso(H)
= 1.5Ueq(O). Water atom H4B is disordered over two sites
(H4B1 and H4B2) and their occupancies were set at 0.5. Aromatic
H atoms were placed in calculated positions, with C—H = 0.93 Å, and
refined in riding mode, with Uiso(H) = 1.2Ueq(C).
Data collection: PROCESS-AUTO (Rigaku, 1998); cell refinement: PROCESS-AUTO (Rigaku, 1998); data reduction: CrystalStructure (Rigaku/MSC, 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).
diaquabis(2-hydroxybenzoato-
κO)bis(1,10-phenanthroline-
κ2N,
N')strontium(II)
top
Crystal data top
[Sr(C7H5O3)2(C12H8N2)2(H2O)2] | F(000) = 1552 |
Mr = 758.28 | Dx = 1.506 Mg m−3 |
Orthorhombic, Pbcn | Mo Kα radiation, λ = 0.71069 Å |
Hall symbol: -P 2n 2ab | Cell parameters from 16753 reflections |
a = 23.411 (4) Å | θ = 2.1–24.2° |
b = 10.409 (2) Å | µ = 1.67 mm−1 |
c = 13.722 (3) Å | T = 295 K |
V = 3343.8 (11) Å3 | Block, colourless |
Z = 4 | 0.35 × 0.29 × 0.27 mm |
Data collection top
Rigaku R-AXIS RAPID diffractometer | 3111 independent reflections |
Radiation source: fine-focus sealed tube | 2383 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.083 |
Detector resolution: 10.00 pixels mm-1 | θmax = 25.5°, θmin = 1.7° |
ω scans | h = −28→28 |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | k = −12→12 |
Tmin = 0.548, Tmax = 0.640 | l = −15→16 |
25451 measured reflections | |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.054 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.113 | H-atom parameters constrained |
S = 1.18 | w = 1/[σ2(Fo2) + (0.0331P)2 + 3.9974P] where P = (Fo2 + 2Fc2)/3 |
3111 reflections | (Δ/σ)max < 0.001 |
231 parameters | Δρmax = 0.30 e Å−3 |
0 restraints | Δρmin = −0.60 e Å−3 |
Crystal data top
[Sr(C7H5O3)2(C12H8N2)2(H2O)2] | V = 3343.8 (11) Å3 |
Mr = 758.28 | Z = 4 |
Orthorhombic, Pbcn | Mo Kα radiation |
a = 23.411 (4) Å | µ = 1.67 mm−1 |
b = 10.409 (2) Å | T = 295 K |
c = 13.722 (3) Å | 0.35 × 0.29 × 0.27 mm |
Data collection top
Rigaku R-AXIS RAPID diffractometer | 3111 independent reflections |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | 2383 reflections with I > 2σ(I) |
Tmin = 0.548, Tmax = 0.640 | Rint = 0.083 |
25451 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.054 | 0 restraints |
wR(F2) = 0.113 | H-atom parameters constrained |
S = 1.18 | Δρmax = 0.30 e Å−3 |
3111 reflections | Δρmin = −0.60 e Å−3 |
231 parameters | |
Special details top
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 (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Sr1 | 0.5000 | 0.32513 (4) | 0.7500 | 0.04858 (18) | |
N1 | 0.56638 (12) | 0.1605 (3) | 0.6259 (2) | 0.0408 (7) | |
N2 | 0.45108 (12) | 0.1306 (3) | 0.6475 (2) | 0.0404 (7) | |
O1 | 0.59582 (12) | 0.4250 (3) | 0.7793 (2) | 0.0595 (8) | |
O2 | 0.63015 (12) | 0.5102 (3) | 0.6429 (2) | 0.0619 (8) | |
O3 | 0.70757 (12) | 0.6744 (3) | 0.6475 (2) | 0.0635 (8) | |
H3 | 0.6739 | 0.6294 | 0.6234 | 0.095* | |
O4 | 0.47715 (12) | 0.4445 (3) | 0.9133 (2) | 0.0695 (9) | |
H4A | 0.4388 | 0.4614 | 0.9116 | 0.104* | |
H4B1 | 0.4980 | 0.4617 | 0.9582 | 0.104* | 0.50 |
H4B2 | 0.4804 | 0.3805 | 0.9570 | 0.104* | 0.50 |
C1 | 0.62949 (15) | 0.4969 (3) | 0.7347 (3) | 0.0455 (9) | |
C2 | 0.67216 (14) | 0.5724 (3) | 0.7920 (3) | 0.0392 (8) | |
C3 | 0.70825 (14) | 0.6612 (3) | 0.7462 (3) | 0.0471 (9) | |
C4 | 0.74526 (16) | 0.7365 (4) | 0.8010 (4) | 0.0600 (11) | |
H4 | 0.7686 | 0.7965 | 0.7703 | 0.072* | |
C5 | 0.74730 (18) | 0.7222 (4) | 0.8997 (4) | 0.0653 (12) | |
H5 | 0.7722 | 0.7730 | 0.9358 | 0.078* | |
C6 | 0.71325 (17) | 0.6340 (4) | 0.9470 (3) | 0.0598 (11) | |
H6 | 0.7155 | 0.6241 | 1.0142 | 0.072* | |
C7 | 0.67561 (15) | 0.5606 (4) | 0.8927 (3) | 0.0478 (9) | |
H7 | 0.6521 | 0.5019 | 0.9243 | 0.057* | |
C8 | 0.62195 (15) | 0.1738 (4) | 0.6138 (3) | 0.0478 (9) | |
H8 | 0.6372 | 0.2563 | 0.6158 | 0.057* | |
C9 | 0.65907 (16) | 0.0719 (4) | 0.5981 (3) | 0.0525 (10) | |
H9 | 0.6980 | 0.0865 | 0.5901 | 0.063* | |
C10 | 0.63777 (17) | −0.0490 (4) | 0.5945 (3) | 0.0530 (10) | |
H10 | 0.6621 | −0.1185 | 0.5847 | 0.064* | |
C11 | 0.57861 (16) | −0.0692 (3) | 0.6057 (3) | 0.0419 (8) | |
C12 | 0.55293 (19) | −0.1938 (4) | 0.6034 (3) | 0.0568 (11) | |
H12 | 0.5758 | −0.2659 | 0.5947 | 0.068* | |
C13 | 0.4960 (2) | −0.2084 (3) | 0.6138 (3) | 0.0571 (11) | |
H13 | 0.4803 | −0.2904 | 0.6122 | 0.069* | |
C14 | 0.45953 (16) | −0.1000 (3) | 0.6273 (3) | 0.0430 (9) | |
C15 | 0.39992 (18) | −0.1094 (4) | 0.6365 (3) | 0.0536 (11) | |
H15 | 0.3825 | −0.1897 | 0.6348 | 0.064* | |
C16 | 0.36765 (16) | −0.0022 (4) | 0.6479 (3) | 0.0532 (10) | |
H16 | 0.3281 | −0.0076 | 0.6515 | 0.064* | |
C17 | 0.39512 (15) | 0.1152 (4) | 0.6541 (3) | 0.0480 (10) | |
H17 | 0.3728 | 0.1881 | 0.6634 | 0.058* | |
C18 | 0.48331 (14) | 0.0243 (3) | 0.6326 (2) | 0.0348 (8) | |
C19 | 0.54446 (15) | 0.0399 (3) | 0.6210 (2) | 0.0346 (8) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Sr1 | 0.0414 (3) | 0.0261 (2) | 0.0783 (4) | 0.000 | −0.0193 (3) | 0.000 |
N1 | 0.0419 (16) | 0.0403 (17) | 0.0403 (17) | −0.0054 (14) | 0.0011 (13) | −0.0064 (14) |
N2 | 0.0383 (16) | 0.0435 (18) | 0.0394 (17) | −0.0017 (14) | −0.0046 (14) | −0.0064 (14) |
O1 | 0.0577 (16) | 0.0526 (17) | 0.068 (2) | −0.0187 (14) | −0.0128 (14) | 0.0050 (14) |
O2 | 0.0714 (19) | 0.0590 (18) | 0.0554 (18) | −0.0084 (15) | −0.0113 (15) | −0.0065 (15) |
O3 | 0.0546 (16) | 0.0676 (19) | 0.068 (2) | 0.0007 (15) | 0.0070 (15) | 0.0124 (17) |
O4 | 0.0631 (17) | 0.095 (2) | 0.0500 (17) | 0.0018 (17) | −0.0160 (14) | −0.0190 (17) |
C1 | 0.0460 (19) | 0.0344 (18) | 0.056 (3) | 0.0026 (16) | −0.0040 (19) | −0.0015 (19) |
C2 | 0.0324 (17) | 0.0325 (18) | 0.053 (2) | 0.0066 (15) | −0.0033 (16) | −0.0055 (17) |
C3 | 0.0364 (17) | 0.042 (2) | 0.063 (2) | 0.0061 (15) | 0.005 (2) | −0.001 (2) |
C4 | 0.034 (2) | 0.053 (3) | 0.093 (3) | −0.0101 (18) | 0.004 (2) | −0.007 (2) |
C5 | 0.046 (2) | 0.065 (3) | 0.085 (3) | −0.003 (2) | −0.012 (3) | −0.028 (3) |
C6 | 0.048 (2) | 0.073 (3) | 0.059 (3) | 0.010 (2) | −0.007 (2) | −0.015 (2) |
C7 | 0.0381 (19) | 0.048 (2) | 0.058 (2) | 0.0048 (17) | −0.0002 (18) | −0.004 (2) |
C8 | 0.043 (2) | 0.050 (2) | 0.050 (2) | −0.0053 (18) | 0.0010 (17) | −0.004 (2) |
C9 | 0.040 (2) | 0.066 (3) | 0.051 (2) | 0.001 (2) | 0.0006 (19) | −0.003 (2) |
C10 | 0.055 (2) | 0.056 (3) | 0.048 (2) | 0.017 (2) | 0.0023 (19) | −0.002 (2) |
C11 | 0.052 (2) | 0.041 (2) | 0.0328 (18) | 0.0069 (17) | −0.0004 (17) | 0.0006 (16) |
C12 | 0.071 (3) | 0.034 (2) | 0.065 (3) | 0.010 (2) | 0.000 (2) | 0.001 (2) |
C13 | 0.083 (3) | 0.0336 (19) | 0.055 (2) | −0.011 (2) | −0.006 (2) | 0.0012 (17) |
C14 | 0.057 (2) | 0.040 (2) | 0.0320 (19) | −0.0074 (18) | −0.0038 (17) | −0.0025 (16) |
C15 | 0.060 (2) | 0.054 (3) | 0.046 (2) | −0.026 (2) | −0.006 (2) | 0.001 (2) |
C16 | 0.040 (2) | 0.069 (3) | 0.050 (2) | −0.013 (2) | −0.0054 (18) | −0.005 (2) |
C17 | 0.040 (2) | 0.060 (3) | 0.044 (2) | −0.0028 (19) | −0.0078 (17) | −0.009 (2) |
C18 | 0.0420 (19) | 0.0364 (19) | 0.0261 (17) | −0.0018 (15) | −0.0062 (14) | −0.0033 (15) |
C19 | 0.0433 (18) | 0.0327 (18) | 0.0277 (17) | −0.0033 (16) | 0.0004 (15) | −0.0016 (15) |
Geometric parameters (Å, º) top
Sr1—O1 | 2.505 (3) | C5—C6 | 1.378 (6) |
Sr1—O1i | 2.505 (3) | C5—H5 | 0.9300 |
Sr1—O4 | 2.618 (3) | C6—C7 | 1.384 (5) |
Sr1—O4i | 2.618 (3) | C6—H6 | 0.9300 |
Sr1—N1i | 2.872 (3) | C7—H7 | 0.9300 |
Sr1—N1 | 2.872 (3) | C8—C9 | 1.388 (5) |
Sr1—N2 | 2.718 (3) | C8—H8 | 0.9300 |
Sr1—N2i | 2.718 (3) | C9—C10 | 1.355 (5) |
Sr1—H4B2 | 2.9341 | C9—H9 | 0.9300 |
N1—C8 | 1.319 (4) | C10—C11 | 1.409 (5) |
N1—C19 | 1.358 (4) | C10—H10 | 0.9300 |
N2—C17 | 1.323 (4) | C11—C19 | 1.404 (5) |
N2—C18 | 1.354 (4) | C11—C12 | 1.430 (5) |
O1—C1 | 1.247 (4) | C12—C13 | 1.348 (6) |
O2—C1 | 1.267 (5) | C12—H12 | 0.9300 |
O3—C3 | 1.362 (5) | C13—C14 | 1.428 (5) |
O3—H3 | 0.9735 | C13—H13 | 0.9300 |
O4—H4A | 0.9149 | C14—C15 | 1.405 (5) |
O4—H4B1 | 0.8069 | C14—C18 | 1.410 (5) |
O4—H4B2 | 0.8998 | C15—C16 | 1.357 (6) |
C1—C2 | 1.495 (5) | C15—H15 | 0.9300 |
C2—C7 | 1.389 (5) | C16—C17 | 1.384 (5) |
C2—C3 | 1.401 (5) | C16—H16 | 0.9300 |
C3—C4 | 1.388 (6) | C17—H17 | 0.9300 |
C4—C5 | 1.364 (6) | C18—C19 | 1.449 (5) |
C4—H4 | 0.9300 | | |
| | | |
O1—Sr1—O4 | 81.30 (9) | C7—C2—C1 | 121.0 (3) |
O1—Sr1—N1 | 81.84 (9) | C3—C2—C1 | 121.0 (4) |
O1—Sr1—N2 | 140.30 (9) | O3—C3—C4 | 119.2 (4) |
O1—Sr1—O1i | 130.96 (13) | O3—C3—C2 | 120.4 (3) |
O1—Sr1—O4i | 75.94 (9) | C4—C3—C2 | 120.4 (4) |
O1—Sr1—N1i | 129.58 (9) | C5—C4—C3 | 119.8 (4) |
O1—Sr1—N2i | 81.31 (9) | C5—C4—H4 | 120.1 |
O1i—Sr1—O4 | 75.94 (9) | C3—C4—H4 | 120.1 |
O1i—Sr1—O4i | 81.30 (9) | C4—C5—C6 | 121.4 (4) |
O1i—Sr1—N2 | 81.31 (9) | C4—C5—H5 | 119.3 |
O1i—Sr1—N2i | 140.30 (9) | C6—C5—H5 | 119.3 |
O1i—Sr1—N1i | 81.84 (9) | C5—C6—C7 | 118.8 (4) |
O1i—Sr1—N1 | 129.58 (9) | C5—C6—H6 | 120.6 |
O4—Sr1—N1 | 154.32 (9) | C7—C6—H6 | 120.6 |
O4—Sr1—N2 | 135.26 (9) | C6—C7—C2 | 121.6 (4) |
O4—Sr1—O4i | 123.31 (15) | C6—C7—H7 | 119.2 |
O4—Sr1—N1i | 70.45 (9) | C2—C7—H7 | 119.2 |
O4—Sr1—N2i | 89.83 (9) | N1—C8—C9 | 123.8 (4) |
O4i—Sr1—N1i | 154.32 (9) | N1—C8—H8 | 118.1 |
O4i—Sr1—N2 | 89.83 (9) | C9—C8—H8 | 118.1 |
O4i—Sr1—N2i | 135.26 (9) | C10—C9—C8 | 119.0 (4) |
O4i—Sr1—N1 | 70.45 (9) | C10—C9—H9 | 120.5 |
N1—Sr1—N2 | 58.46 (9) | C8—C9—H9 | 120.5 |
N1—Sr1—N1i | 106.74 (12) | C9—C10—C11 | 119.7 (4) |
N2—Sr1—N1i | 68.54 (9) | C9—C10—H10 | 120.1 |
N2—Sr1—N2i | 83.68 (13) | C11—C10—H10 | 120.1 |
N2i—Sr1—N1i | 58.46 (9) | C19—C11—C10 | 117.1 (3) |
N2i—Sr1—N1 | 68.54 (9) | C19—C11—C12 | 119.8 (3) |
O1—Sr1—H4B2 | 84.4 | C10—C11—C12 | 123.1 (4) |
O1i—Sr1—H4B2 | 86.2 | C13—C12—C11 | 121.0 (4) |
O4—Sr1—H4B2 | 17.5 | C13—C12—H12 | 119.5 |
O4i—Sr1—H4B2 | 140.1 | C11—C12—H12 | 119.5 |
N2—Sr1—H4B2 | 125.5 | C12—C13—C14 | 121.1 (3) |
N2i—Sr1—H4B2 | 73.2 | C12—C13—H13 | 119.5 |
N1i—Sr1—H4B2 | 57.2 | C14—C13—H13 | 119.5 |
N1—Sr1—H4B2 | 140.8 | C15—C14—C18 | 116.9 (4) |
C8—N1—C19 | 117.6 (3) | C15—C14—C13 | 123.4 (4) |
C8—N1—Sr1 | 123.1 (2) | C18—C14—C13 | 119.7 (3) |
C19—N1—Sr1 | 112.1 (2) | C16—C15—C14 | 120.4 (4) |
C17—N2—C18 | 117.6 (3) | C16—C15—H15 | 119.8 |
C17—N2—Sr1 | 118.2 (2) | C14—C15—H15 | 119.8 |
C18—N2—Sr1 | 116.9 (2) | C15—C16—C17 | 118.4 (3) |
C1—O1—Sr1 | 137.5 (3) | C15—C16—H16 | 120.8 |
C3—O3—H3 | 107.4 | C17—C16—H16 | 120.8 |
Sr1—O4—H4A | 105.6 | N2—C17—C16 | 124.2 (4) |
Sr1—O4—H4B1 | 129.5 | N2—C17—H17 | 117.9 |
H4A—O4—H4B1 | 124.9 | C16—C17—H17 | 117.9 |
Sr1—O4—H4B2 | 101.6 | N2—C18—C14 | 122.5 (3) |
H4A—O4—H4B2 | 104.1 | N2—C18—C19 | 118.4 (3) |
H4B1—O4—H4B2 | 66.6 | C14—C18—C19 | 119.1 (3) |
O1—C1—O2 | 124.1 (4) | N1—C19—C11 | 122.7 (3) |
O1—C1—C2 | 118.7 (4) | N1—C19—C18 | 118.1 (3) |
O2—C1—C2 | 117.2 (3) | C11—C19—C18 | 119.2 (3) |
C7—C2—C3 | 118.0 (4) | | |
Symmetry code: (i) −x+1, y, −z+3/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3···O2 | 0.97 | 1.63 | 2.492 (4) | 145 |
O4—H4A···O2i | 0.92 | 1.85 | 2.715 (4) | 157 |
O4—H4B1···O4ii | 0.81 | 2.10 | 2.853 (4) | 156 |
C9—H9···O3iii | 0.93 | 2.52 | 3.368 (5) | 152 |
C10—H10···O3iv | 0.93 | 2.55 | 3.389 (5) | 150 |
Symmetry codes: (i) −x+1, y, −z+3/2; (ii) −x+1, −y+1, −z+2; (iii) −x+3/2, y−1/2, z; (iv) x, y−1, z. |
Experimental details
Crystal data |
Chemical formula | [Sr(C7H5O3)2(C12H8N2)2(H2O)2] |
Mr | 758.28 |
Crystal system, space group | Orthorhombic, Pbcn |
Temperature (K) | 295 |
a, b, c (Å) | 23.411 (4), 10.409 (2), 13.722 (3) |
V (Å3) | 3343.8 (11) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 1.67 |
Crystal size (mm) | 0.35 × 0.29 × 0.27 |
|
Data collection |
Diffractometer | Rigaku R-AXIS RAPID diffractometer |
Absorption correction | Multi-scan (ABSCOR; Higashi, 1995) |
Tmin, Tmax | 0.548, 0.640 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 25451, 3111, 2383 |
Rint | 0.083 |
(sin θ/λ)max (Å−1) | 0.606 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.054, 0.113, 1.18 |
No. of reflections | 3111 |
No. of parameters | 231 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.30, −0.60 |
Selected bond lengths (Å) topSr1—O1 | 2.505 (3) | Sr1—N1 | 2.872 (3) |
Sr1—O4 | 2.618 (3) | Sr1—N2 | 2.718 (3) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3···O2 | 0.97 | 1.63 | 2.492 (4) | 145 |
O4—H4A···O2i | 0.92 | 1.85 | 2.715 (4) | 157 |
O4—H4B1···O4ii | 0.81 | 2.10 | 2.853 (4) | 156 |
C9—H9···O3iii | 0.93 | 2.52 | 3.368 (5) | 152 |
C10—H10···O3iv | 0.93 | 2.55 | 3.389 (5) | 150 |
Symmetry codes: (i) −x+1, y, −z+3/2; (ii) −x+1, −y+1, −z+2; (iii) −x+3/2, y−1/2, z; (iv) x, y−1, z. |
Comparison of the Sr—N bond distances (Å) and the atomic deviation(s) (Å)
of Sr from the phen plane(s) in (I) with those found in analogous complexes topComplex | Sr—Nmin | Sr—Nmax | Sr-phenmin | Sr-phenmax |
(I) | 2.718 (3) | 2.872 (3) | 1.374 (3) | |
(II) | 2.7754 | 2.8080 | 0.062 | |
(III) | 2.766 (7) | 2.772 (6) | 0.003 | |
(IV) | 2.709 (14) | 2.825 (17) | 0.442 (3) | 0.519 (3) |
(V) | 2.573 (3) | 2.810 (4) | 0.111 (1) | 0.456 (1) |
(VI) | 2.680 (9) | 2.847 (9) | 0.184 (1) | 0.244 (1) |
(VII) | 2.613 (3) | 2.714 (3) | 0.007 (1) | 0.396 (1) |
(VIII) | 2.710 (3) | 2.731 (3) | 0.224 (1) | |
Notes:
(II) Tetraaquabis(1,10-phenanthroline)strontium(II) diperchlorate
bis(1,10-phenanthroline) (no s.u.s are available; Smith et al.,
1977).
(III) Tetraaquabis(1,10-phenanthroline)strontium(II) diiodide
bis(1,10-phenanthroline) (Kepert et al., 1996).
(IV) Bis(dipivaloylmethanato)bis(1,10-phenanthrolinato)strontium
(Soboleva et al., 1995).
(V) catena-Poly[[hexakis[(µ2-cyano)aqua(1,10-phenanthroline)]diiron(III)-
tristrontium(II) 1,10-phenanthroline solvate hydrate] (Datta et al.,
2003).
(VI) catena-Poly[bis(µ2-cyano)bis(dimethylformamide)tricyanonitrosyl-
bis(1,10-phenanthroline)ironstrontium] (RoyChowdhury et al., 2004).
(VII) Bis(µ2-cyano)triaquatetracyano(nitrato-O,O')tetrakis(1,10-
phenanthroline)iron(III)distrontium hydrate (Datta et al.,
2002).
(VIII) Diaquabis(2,5-dihydroxybenzoato)bis(1,10-phenanthroline)
strontium(II) bis(1,10-phenanthroline) tetrahydrate (Xu et al.,
2007). |
As π–π stacking between aromatic rings plays an important role in electron-transfer processes in some biological systems (Deisenhofer & Michel, 1989), it has attracted our attention in recent years. Because π–π stacking is usually observed between adjacent molecules, it is considered as a type of intermolecular interaction. In order to understand the nature of π–π stacking, a series of metal complexes incorporating aromatic ligands such as phenanthroline (phen) (Nie et al., 2001), benzimidazole (Chen et al., 2003), bipyridine (Xu et al., 1996), diaminobithiazole (Luo et al., 2004) and substituted benzoate (Cheng et al., 2000) has been prepared and their crystal structures have been determined in our laboratory. As part of our ongoing investigation into the nature of π–π stacking, the title SrII complex, (I), has recently been prepared, and its X-ray crystal structure, which shows unusual intramolecular π–π stacking, is presented here.
The molecular structure of (I) is shown in Fig. 1. The SrII ion is located on a twofold rotation axis and coordinated by two phen ligands, two 2-hydroxybenzoate anions and two water molecules in a distorted square-antiprism coordination geometry. Coordinated bond distances and angles are listed in Table 1. In order to compare the coordination geometry, a search of the Cambridge Structure Database (Version ?, updated in November 2006; Allen, 2002) was performed. Table 2 summarizes the Sr—N bond distances in (I) and the maximum and minimum Sr—N bond distances in the SrII complexes with a phen ligand reported previously. The atomic deviations of the SrII ion from the chelating phen ligands are also listed in Table 2 in order to compare coplanarities. These values show that in all these SrII complexes the SrII ion is nearly coplanar with the phen mean plane. In (I), however, the SrII ion deviates from the phen mean planes by 1.374 (3) Å, the chelating phen ligand tilting with respect to the Sr1/N1/N2 plane by a larger dihedral angle of 33.49 (7)°. This clearly indicates the poor overlap between the atomic orbitals of the SrII ion and phen N atoms in the structure. However, the average Sr—N bond of 2.795 (3) Å is similar to those found in related SrII complexes (Table 2). These facts suggest a more electrostatic nature of Sr—N bonds in (I).
The two phen ligands, which are related by the twofold rotation axis, are nearly parallel to each other, the dihedral angle being 10.47 (2)°. The partially overlapped arrangement between these two nearly parallel phen ligands is shown in Fig. 2. Atoms C11i, C14i, C16i, C17i and C19i of the N1i-containing phen ligand [symmetry code: (i) 1 - x, y, 3/2 - z] are displaced from the N1-phen mean plane by 3.470 (4), 3.537 (4), 3.413 (5), 3.139 (5) and 3.250 (4) Å, respectively, with an average value of 3.362 (5) Å, appreciably shorter than the van der Waals thickness of an aromatic ring (3.70 Å; Cotton & Wilkinson, 1972). A PLATON calculation (Spek, 2003) shows a short Cg···Cg separation of 3.511 (2) Å between the two phen ligands, involving the N1-pyridine and the C12i-benzene rings. These facts suggest the existence of intramolecular π–π stacking between the coordinated phen ligands within the mononuclear complex. As expected, intermolecular π–π stacking is also observed between parallel phen ligands of adjacent molecules of the complex (Fig. 3). The face-to-face separation between parallel N1-phen and N1ii-phen is 3.422 (8) Å [symmetry code: (ii) 1 - x, -y, 1 - z].
This structure determination reveals that π–π stacking interactions can be not only intermolecular but also intramolecular in nature, somehow correlating to their hydrogen-bonding counterparts. Classic O—H···O and weak C—H···O hydrogen bonds also occur in the crystal structure of (I) (Table 3). Intramolecular O—H···O hydrogen bonds form internal loops (Fig. 1). Intermolecular O—H···O and weak C—H···O hydrogen bonding, in turn, helps to stabilize the crystal structure.