Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102022734/vj1183sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270102022734/vj1183Isup2.hkl |
CCDC reference: 205294
For the preparation of the title compound, gadolinium perchlorate and alanine were mixed in a 1:1 molar ratio in water. The mixed solution was neutralized with an NaOH solution to a pH of 7.0 with stirring. The gadolinium ions were partially hydrolyzed to form a precipitate which was filtered off. The remaining filtrate was evaporated slowly at room temperature, yielding colorless prismatic crystals.
The perchlorate groups and the methyl groups of the alanine ligands were found to be disordered. The occupancy factors for the disordered atoms, each in two positions, were estimated on the basis of electron densities. All non-H atoms were refined anisotropically, except for those with occupancy factors less than 1/2, which were refined isotropically. H-atom parameters were not defined.
Data collection: P4 Software (Siemens, 1995); cell refinement: P4 Software; data reduction: P4 Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: please provide; software used to prepare material for publication: SHELXL97.
[Gd2(C3H7NO2)4(H2O)8](ClO4)6 | Z = 1 |
Mr = 1411.71 | F(000) = 694 |
Triclinic, P1 | Dx = 2.053 Mg m−3 |
a = 11.057 (2) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 11.0584 (18) Å | Cell parameters from 23 reflections |
c = 11.339 (3) Å | θ = 4.7–8.2° |
α = 78.420 (18)° | µ = 3.35 mm−1 |
β = 64.689 (16)° | T = 293 K |
γ = 65.696 (16)° | Prismatic, colorless |
V = 1141.7 (4) Å3 | 0.52 × 0.40 × 0.32 mm |
Siemens P4 diffractometer | 3879 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.025 |
Graphite monochromator | θmax = 26.0°, θmin = 2.0° |
ω scans | h = −12→11 |
Absorption correction: ψ scan Sheldrick, 1983 | k = −13→1 |
Tmin = 0.640, Tmax = 0.947 | l = −13→13 |
5251 measured reflections | 3 standard reflections every 97 reflections |
4367 independent reflections | intensity decay: none |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.044 | H-atom parameters not refined |
wR(F2) = 0.119 | w = 1/[σ2(Fo2) + (0.075P)2 + 3.0801P] where P = (Fo2 + 2Fc2)/3 |
S = 1.01 | (Δ/σ)max = 0.042 |
4367 reflections | Δρmax = 1.32 e Å−3 |
312 parameters | Δρmin = −1.06 e Å−3 |
25 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0187 (13) |
[Gd2(C3H7NO2)4(H2O)8](ClO4)6 | γ = 65.696 (16)° |
Mr = 1411.71 | V = 1141.7 (4) Å3 |
Triclinic, P1 | Z = 1 |
a = 11.057 (2) Å | Mo Kα radiation |
b = 11.0584 (18) Å | µ = 3.35 mm−1 |
c = 11.339 (3) Å | T = 293 K |
α = 78.420 (18)° | 0.52 × 0.40 × 0.32 mm |
β = 64.689 (16)° |
Siemens P4 diffractometer | 3879 reflections with I > 2σ(I) |
Absorption correction: ψ scan Sheldrick, 1983 | Rint = 0.025 |
Tmin = 0.640, Tmax = 0.947 | 3 standard reflections every 97 reflections |
5251 measured reflections | intensity decay: none |
4367 independent reflections |
R[F2 > 2σ(F2)] = 0.044 | 25 restraints |
wR(F2) = 0.119 | H-atom parameters not refined |
S = 1.01 | Δρmax = 1.32 e Å−3 |
4367 reflections | Δρmin = −1.06 e Å−3 |
312 parameters |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Gd | 0.21839 (3) | 0.00526 (3) | −0.09624 (3) | 0.02820 (16) | |
Cl1 | 0.6534 (2) | −0.3720 (2) | −0.4737 (2) | 0.0519 (5) | |
Cl2 | 0.3376 (3) | 0.4286 (2) | −0.0248 (3) | 0.0636 (6) | |
Cl3 | 0.7092 (3) | 0.0711 (3) | −0.3867 (2) | 0.0640 (6) | |
OW1 | 0.2677 (10) | 0.2066 (8) | −0.1651 (7) | 0.077 (2) | |
OW2 | 0.3364 (7) | 0.0180 (7) | −0.3358 (5) | 0.0554 (15) | |
OW3 | 0.4585 (6) | −0.1646 (7) | −0.1659 (6) | 0.0602 (16) | |
OW4 | 0.3464 (7) | 0.0275 (7) | 0.0307 (6) | 0.0606 (17) | |
O1 | 0.1817 (6) | −0.1551 (5) | −0.1720 (6) | 0.0466 (13) | |
O2 | −0.0483 (6) | −0.1351 (6) | −0.0833 (6) | 0.0554 (15) | |
O3 | 0.2039 (7) | −0.1535 (6) | 0.0760 (5) | 0.0532 (15) | |
O4 | −0.0286 (7) | −0.1246 (6) | 0.1601 (7) | 0.0639 (18) | |
O5 | 0.7401 (16) | −0.3854 (17) | −0.4048 (15) | 0.110 (5) | 0.70 |
O6 | 0.7290 (18) | −0.3693 (13) | −0.6088 (10) | 0.116 (6) | 0.70 |
O7 | 0.5380 (14) | −0.2541 (12) | −0.4390 (16) | 0.105 (5) | 0.70 |
O8 | 0.6139 (14) | −0.4851 (11) | −0.4409 (10) | 0.079 (3) | 0.70 |
O5' | 0.784 (2) | −0.476 (3) | −0.483 (4) | 0.148 (16)* | 0.30 |
O6' | 0.669 (5) | −0.249 (3) | −0.501 (4) | 0.19 (2)* | 0.30 |
O7' | 0.552 (3) | −0.374 (4) | −0.341 (2) | 0.125 (12)* | 0.30 |
O8' | 0.597 (4) | −0.394 (4) | −0.555 (3) | 0.19 (2)* | 0.30 |
O9 | 0.441 (2) | 0.2989 (18) | −0.0495 (18) | 0.116 (6)* | 0.60 |
O10 | 0.397 (2) | 0.519 (2) | −0.119 (2) | 0.139 (7)* | 0.60 |
O11 | 0.216 (2) | 0.426 (2) | −0.034 (2) | 0.133 (7)* | 0.60 |
O12 | 0.303 (3) | 0.455 (2) | 0.099 (2) | 0.157 (9)* | 0.60 |
O9' | 0.442 (3) | 0.414 (3) | 0.031 (4) | 0.146 (11)* | 0.40 |
O10' | 0.392 (3) | 0.433 (3) | −0.163 (2) | 0.100 (7)* | 0.40 |
O11' | 0.269 (4) | 0.336 (3) | 0.034 (4) | 0.172 (15)* | 0.40 |
O12' | 0.217 (3) | 0.546 (3) | 0.019 (4) | 0.151 (12)* | 0.40 |
O13 | 0.7933 (14) | 0.0099 (12) | −0.3117 (13) | 0.128 (4)* | |
O14 | 0.586 (2) | 0.043 (2) | −0.346 (2) | 0.112 (6)* | 0.60 |
O15 | 0.666 (2) | 0.2207 (17) | −0.4059 (19) | 0.113 (5)* | 0.60 |
O16 | 0.807 (2) | 0.0222 (19) | −0.5196 (19) | 0.120 (6)* | 0.60 |
O14' | 0.639 (3) | −0.003 (2) | −0.408 (3) | 0.090 (6)* | 0.40 |
O15' | 0.583 (2) | 0.180 (3) | −0.295 (3) | 0.152 (12)* | 0.40 |
O16' | 0.774 (4) | 0.133 (4) | −0.503 (3) | 0.165 (13)* | 0.40 |
N1 | 0.2696 (8) | −0.3483 (7) | −0.3219 (7) | 0.0507 (17) | |
N2 | 0.2707 (8) | −0.3434 (7) | 0.2412 (7) | 0.0506 (17) | |
C1 | 0.0773 (8) | −0.1860 (7) | −0.1609 (7) | 0.0391 (16) | |
C2 | 0.1178 (10) | −0.2906 (13) | −0.2495 (11) | 0.081 (4) | |
C3 | 0.027 (3) | −0.361 (2) | −0.213 (3) | 0.084 (8) | 0.50 |
C3' | 0.009 (2) | −0.275 (2) | −0.294 (3) | 0.076 (7) | 0.50 |
C4 | 0.0943 (8) | −0.1777 (7) | 0.1600 (7) | 0.0386 (16) | |
C5 | 0.1166 (9) | −0.2736 (10) | 0.2689 (8) | 0.057 (2) | |
C6 | 0.012 (2) | −0.229 (3) | 0.4017 (16) | 0.078 (7) | 0.50 |
C6' | 0.027 (3) | −0.350 (3) | 0.310 (4) | 0.124 (14) | 0.50 |
U11 | U22 | U33 | U12 | U13 | U23 | |
Gd | 0.0251 (2) | 0.0342 (2) | 0.0242 (2) | −0.00999 (14) | −0.00894 (13) | −0.00196 (12) |
Cl1 | 0.0560 (12) | 0.0387 (10) | 0.0429 (10) | −0.0052 (9) | −0.0148 (9) | −0.0009 (8) |
Cl2 | 0.0727 (15) | 0.0560 (13) | 0.0674 (14) | −0.0142 (12) | −0.0375 (12) | −0.0093 (11) |
Cl3 | 0.0717 (15) | 0.0884 (18) | 0.0513 (12) | −0.0440 (14) | −0.0281 (11) | 0.0003 (11) |
OW1 | 0.129 (7) | 0.074 (5) | 0.060 (4) | −0.070 (5) | −0.042 (4) | 0.015 (3) |
OW2 | 0.057 (4) | 0.075 (4) | 0.030 (3) | −0.028 (3) | −0.010 (3) | 0.000 (3) |
OW3 | 0.042 (3) | 0.065 (4) | 0.048 (3) | 0.001 (3) | −0.014 (3) | −0.004 (3) |
OW4 | 0.048 (3) | 0.092 (5) | 0.052 (3) | −0.028 (3) | −0.024 (3) | −0.008 (3) |
O1 | 0.043 (3) | 0.044 (3) | 0.056 (3) | −0.016 (2) | −0.017 (3) | −0.013 (2) |
O2 | 0.047 (3) | 0.060 (4) | 0.046 (3) | −0.015 (3) | 0.001 (3) | −0.027 (3) |
O3 | 0.062 (4) | 0.050 (3) | 0.040 (3) | −0.019 (3) | −0.021 (3) | 0.015 (2) |
O4 | 0.053 (4) | 0.054 (4) | 0.086 (5) | 0.003 (3) | −0.049 (4) | −0.003 (3) |
O5 | 0.106 (10) | 0.156 (14) | 0.119 (11) | −0.075 (10) | −0.081 (9) | 0.034 (10) |
O6 | 0.143 (13) | 0.093 (9) | 0.039 (5) | −0.027 (9) | 0.005 (7) | 0.013 (6) |
O7 | 0.077 (8) | 0.054 (7) | 0.152 (13) | 0.021 (6) | −0.042 (8) | −0.047 (8) |
O8 | 0.114 (9) | 0.062 (6) | 0.063 (6) | −0.040 (6) | −0.035 (6) | 0.010 (5) |
N1 | 0.041 (4) | 0.049 (4) | 0.049 (4) | −0.004 (3) | −0.008 (3) | −0.022 (3) |
N2 | 0.042 (4) | 0.046 (4) | 0.058 (4) | −0.006 (3) | −0.029 (3) | 0.012 (3) |
C1 | 0.044 (4) | 0.042 (4) | 0.028 (3) | −0.013 (3) | −0.011 (3) | −0.010 (3) |
C2 | 0.041 (5) | 0.119 (10) | 0.081 (7) | −0.017 (6) | −0.003 (5) | −0.076 (7) |
C3 | 0.079 (16) | 0.068 (14) | 0.104 (19) | −0.048 (13) | −0.001 (14) | −0.036 (14) |
C3' | 0.069 (14) | 0.080 (15) | 0.102 (18) | −0.015 (12) | −0.057 (14) | −0.026 (14) |
C4 | 0.048 (4) | 0.034 (4) | 0.039 (4) | −0.012 (3) | −0.026 (3) | 0.001 (3) |
C5 | 0.032 (4) | 0.069 (6) | 0.045 (4) | −0.010 (4) | −0.009 (3) | 0.017 (4) |
C6 | 0.050 (11) | 0.112 (19) | 0.043 (10) | −0.029 (12) | 0.006 (9) | 0.004 (11) |
C6' | 0.069 (16) | 0.080 (18) | 0.20 (4) | −0.045 (15) | −0.04 (2) | 0.06 (2) |
Gd—O4i | 2.304 (6) | Cl3—O16' | 1.40 (3) |
Gd—O2i | 2.328 (5) | Cl3—O14 | 1.39 (2) |
Gd—O3 | 2.347 (5) | Cl3—O13 | 1.404 (13) |
Gd—O1 | 2.356 (5) | Cl3—O16 | 1.479 (19) |
Gd—OW1 | 2.408 (6) | Cl3—O14' | 1.45 (2) |
Gd—OW3 | 2.429 (6) | Cl3—O15 | 1.520 (18) |
Gd—OW2 | 2.463 (5) | Cl3—O15' | 1.538 (17) |
Gd—OW4 | 2.511 (6) | O1—C1 | 1.284 (9) |
Cl1—O5' | 1.404 (17) | O2—C1 | 1.238 (9) |
Cl1—O6' | 1.394 (17) | O2—Gdi | 2.328 (5) |
Cl1—O7 | 1.375 (10) | O3—C4 | 1.275 (10) |
Cl1—O6 | 1.398 (10) | O4—C4 | 1.238 (10) |
Cl1—O8' | 1.420 (17) | O4—Gdi | 2.304 (6) |
Cl1—O5 | 1.425 (12) | N1—C2 | 1.432 (11) |
Cl1—O8 | 1.420 (11) | N2—C5 | 1.469 (10) |
Cl1—O7' | 1.446 (17) | C1—C2 | 1.485 (10) |
Cl2—O12 | 1.35 (2) | C2—C3 | 1.394 (15) |
Cl2—O12' | 1.41 (3) | C2—C3' | 1.426 (15) |
Cl2—O11 | 1.41 (2) | C3—C3' | 1.20 (4) |
Cl2—O9 | 1.408 (18) | C4—C5 | 1.493 (11) |
Cl2—O10' | 1.42 (3) | C5—C6' | 1.430 (16) |
Cl2—O11' | 1.42 (3) | C5—C6 | 1.479 (15) |
Cl2—O10 | 1.45 (2) | C6—C6' | 1.76 (4) |
Cl2—O9' | 1.48 (3) | ||
O4i—Gd—O2i | 77.2 (2) | O12—Cl2—O11' | 84.5 (19) |
O4i—Gd—O3 | 122.4 (2) | O12'—Cl2—O11' | 98.9 (17) |
O2i—Gd—O3 | 77.8 (2) | O11—Cl2—O11' | 51.9 (15) |
O4i—Gd—O1 | 75.4 (2) | O9—Cl2—O11' | 70.6 (16) |
O2i—Gd—O1 | 123.6 (2) | O10'—Cl2—O11' | 114 (2) |
O3—Gd—O1 | 77.1 (2) | O12—Cl2—O10 | 112.9 (14) |
O4i—Gd—OW1 | 82.4 (3) | O12'—Cl2—O10 | 82.4 (16) |
O2i—Gd—OW1 | 80.1 (3) | O11—Cl2—O10 | 112.9 (13) |
O3—Gd—OW1 | 141.2 (2) | O9—Cl2—O10 | 108.7 (12) |
O1—Gd—OW1 | 141.5 (2) | O10'—Cl2—O10 | 48.9 (12) |
O4i—Gd—OW3 | 142.9 (2) | O11'—Cl2—O10 | 161.2 (19) |
O2i—Gd—OW3 | 139.9 (2) | O12—Cl2—O9' | 55.3 (15) |
O3—Gd—OW3 | 76.3 (2) | O12'—Cl2—O9' | 109.5 (17) |
O1—Gd—OW3 | 79.2 (2) | O11—Cl2—O9' | 160.1 (17) |
OW1—Gd—OW3 | 102.2 (3) | O9—Cl2—O9' | 72.6 (14) |
O4i—Gd—OW2 | 76.8 (2) | O10'—Cl2—O9' | 114.4 (18) |
O2i—Gd—OW2 | 142.1 (2) | O11'—Cl2—O9' | 111.3 (18) |
O3—Gd—OW2 | 139.9 (2) | O10—Cl2—O9' | 85.6 (16) |
O1—Gd—OW2 | 74.9 (2) | O16'—Cl3—O14 | 129.0 (19) |
OW1—Gd—OW2 | 69.6 (2) | O16'—Cl3—O13 | 114.7 (18) |
OW3—Gd—OW2 | 70.8 (2) | O14—Cl3—O13 | 115.4 (10) |
O4i—Gd—OW4 | 141.3 (2) | O16'—Cl3—O16 | 47.5 (16) |
O2i—Gd—OW4 | 71.5 (2) | O14—Cl3—O16 | 110.1 (12) |
O3—Gd—OW4 | 72.4 (2) | O13—Cl3—O16 | 104.2 (10) |
O1—Gd—OW4 | 141.7 (2) | O16'—Cl3—O14' | 110.8 (19) |
OW1—Gd—OW4 | 70.5 (2) | O14—Cl3—O14' | 32.8 (11) |
OW3—Gd—OW4 | 71.8 (2) | O13—Cl3—O14' | 118.0 (11) |
OW2—Gd—OW4 | 116.4 (2) | O16—Cl3—O14' | 78.3 (13) |
O5'—Cl1—O6' | 111.2 (16) | O16'—Cl3—O15 | 56.5 (16) |
O5'—Cl1—O7 | 160.7 (18) | O14—Cl3—O15 | 107.4 (11) |
O6'—Cl1—O7 | 57.5 (18) | O13—Cl3—O15 | 115.8 (9) |
O5'—Cl1—O6 | 80.4 (17) | O16—Cl3—O15 | 103.1 (9) |
O6'—Cl1—O6 | 75.4 (18) | O14'—Cl3—O15 | 123.8 (12) |
O7—Cl1—O6 | 108.8 (9) | O16'—Cl3—O15' | 107.6 (17) |
O5'—Cl1—O8' | 110.6 (16) | O14—Cl3—O15' | 71.4 (15) |
O6'—Cl1—O8' | 111.9 (16) | O13—Cl3—O15' | 101.0 (11) |
O7—Cl1—O8' | 88.6 (19) | O16—Cl3—O15' | 150.6 (13) |
O6—Cl1—O8' | 61.7 (18) | O14'—Cl3—O15' | 102.9 (16) |
O5'—Cl1—O5 | 53.3 (17) | O15—Cl3—O15' | 51.4 (13) |
O6'—Cl1—O5 | 78.4 (19) | C1—O1—Gd | 139.0 (5) |
O7—Cl1—O5 | 107.5 (10) | C1—O2—Gdi | 151.1 (5) |
O6—Cl1—O5 | 111.7 (10) | C4—O3—Gd | 129.4 (5) |
O8'—Cl1—O5 | 163.9 (18) | C4—O4—Gdi | 162.1 (6) |
O5'—Cl1—O8 | 77.9 (17) | O2—C1—O1 | 124.3 (7) |
O6'—Cl1—O8 | 170.9 (19) | O2—C1—C2 | 120.9 (7) |
O7—Cl1—O8 | 113.6 (9) | O1—C1—C2 | 114.8 (7) |
O6—Cl1—O8 | 107.7 (8) | C3—C2—C3' | 50.4 (16) |
O8'—Cl1—O8 | 63.9 (18) | C3—C2—N1 | 122.8 (14) |
O5—Cl1—O8 | 107.6 (8) | C3'—C2—N1 | 125.2 (12) |
O5'—Cl1—O7' | 107.5 (15) | C3—C2—C1 | 116.9 (11) |
O6'—Cl1—O7' | 108.8 (15) | C3'—C2—C1 | 114.5 (11) |
O7—Cl1—O7' | 66.6 (15) | N1—C2—C1 | 113.2 (7) |
O6—Cl1—O7' | 168.2 (15) | C3'—C3—C2 | 66.2 (12) |
O8'—Cl1—O7' | 106.7 (15) | C3—C3'—C2 | 63.4 (12) |
O5—Cl1—O7' | 80.1 (15) | O4—C4—O3 | 125.0 (7) |
O8—Cl1—O7' | 66.5 (15) | O4—C4—C5 | 118.2 (7) |
O12—Cl2—O12' | 67.0 (16) | O3—C4—C5 | 116.7 (7) |
O12—Cl2—O11 | 108.2 (14) | C6'—C5—C6 | 74.6 (19) |
O12'—Cl2—O11 | 67.9 (15) | C6'—C5—N2 | 118.6 (14) |
O12—Cl2—O9 | 107.6 (12) | C6—C5—N2 | 121.3 (12) |
O12'—Cl2—O9 | 168.9 (16) | C6'—C5—C4 | 111.8 (13) |
O11—Cl2—O9 | 106.2 (12) | C6—C5—C4 | 115.6 (12) |
O12—Cl2—O10' | 161.7 (15) | N2—C5—C4 | 110.6 (6) |
O12'—Cl2—O10' | 107.7 (18) | C6'—C6—C5 | 51.4 (10) |
O11—Cl2—O10' | 84.4 (14) | C5—C6'—C6 | 54.0 (12) |
O9—Cl2—O10' | 80.4 (13) |
Symmetry code: (i) −x, −y, −z. |
Experimental details
Crystal data | |
Chemical formula | [Gd2(C3H7NO2)4(H2O)8](ClO4)6 |
Mr | 1411.71 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 11.057 (2), 11.0584 (18), 11.339 (3) |
α, β, γ (°) | 78.420 (18), 64.689 (16), 65.696 (16) |
V (Å3) | 1141.7 (4) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 3.35 |
Crystal size (mm) | 0.52 × 0.40 × 0.32 |
Data collection | |
Diffractometer | Siemens P4 diffractometer |
Absorption correction | ψ scan Sheldrick, 1983 |
Tmin, Tmax | 0.640, 0.947 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5251, 4367, 3879 |
Rint | 0.025 |
(sin θ/λ)max (Å−1) | 0.617 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.044, 0.119, 1.01 |
No. of reflections | 4367 |
No. of parameters | 312 |
No. of restraints | 25 |
H-atom treatment | H-atom parameters not refined |
Δρmax, Δρmin (e Å−3) | 1.32, −1.06 |
Computer programs: P4 Software (Siemens, 1995), P4 Software, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), please provide, SHELXL97.
Gd—O4i | 2.304 (6) | Gd—OW1 | 2.408 (6) |
Gd—O2i | 2.328 (5) | Gd—OW3 | 2.429 (6) |
Gd—O3 | 2.347 (5) | Gd—OW2 | 2.463 (5) |
Gd—O1 | 2.356 (5) | Gd—OW4 | 2.511 (6) |
O4i—Gd—O2i | 77.2 (2) | OW1—Gd—OW3 | 102.2 (3) |
O4i—Gd—O3 | 122.4 (2) | O4i—Gd—OW2 | 76.8 (2) |
O2i—Gd—O3 | 77.8 (2) | O2i—Gd—OW2 | 142.1 (2) |
O4i—Gd—O1 | 75.4 (2) | O3—Gd—OW2 | 139.9 (2) |
O2i—Gd—O1 | 123.6 (2) | O1—Gd—OW2 | 74.9 (2) |
O3—Gd—O1 | 77.1 (2) | OW1—Gd—OW2 | 69.6 (2) |
O4i—Gd—OW1 | 82.4 (3) | OW3—Gd—OW2 | 70.8 (2) |
O2i—Gd—OW1 | 80.1 (3) | O4i—Gd—OW4 | 141.3 (2) |
O3—Gd—OW1 | 141.2 (2) | O2i—Gd—OW4 | 71.5 (2) |
O1—Gd—OW1 | 141.5 (2) | O3—Gd—OW4 | 72.4 (2) |
O4i—Gd—OW3 | 142.9 (2) | O1—Gd—OW4 | 141.7 (2) |
O2i—Gd—OW3 | 139.9 (2) | OW1—Gd—OW4 | 70.5 (2) |
O3—Gd—OW3 | 76.3 (2) | OW3—Gd—OW4 | 71.8 (2) |
O1—Gd—OW3 | 79.2 (2) | OW2—Gd—OW4 | 116.4 (2) |
Symmetry code: (i) −x, −y, −z. |
In recent years, the uses of rare earth elements have become widespread. More and more rare earth elements are entering the environment and the human body via the food chain, etc. Therefore, it is important to study the biological effects of these elements. The structural investigation of rare earth ion–amino acid complexes is of interest with respect to both the understanding of the biological effects of rare earth elements and the enrichment of rare-earth coordination chemistry. Some structures of such complexes have been reported; see, for example, Legendziewicz et al. (1984), Csoregh et al. (1989), Glowiak et al. (1991), Hu et al. (1995), Ma et al. (1995) and Wang et al. (1994). However, reports of the crystal structures of gadolinium–amino acid complexes are rare (Zheng et al., 1993; Gao et al., 2001), and there are no reports of the crystal structures of gadolinium–alanine complexes. In this paper, crystal structure of the title complex, (I), has been studied in order to study the crystal structure of a rare-earth complex with an amino acid and to predict the structural parameters of unknown complexes of rare earth elements with amino acids by artificial neural network.
The title compound crystallized in the triclinic system and the structure consists of centrosymmetric dimeric [Gd2(Ala)4(H2O)8]6+ complex cations (Ala is α-alanine) and ClO4− anions. Their configuration of the ions is illustrated in Fig. 1 and selected geometric parameters are listed in Table 1. The alanine molecules exist in the zwitterionic form, with the amine groups protonated and the carboxyl groups deprotonated. The two gadolinium ions in the dimeric [Gd2(Ala)4(H2O)8]6+ complex cation are connected by four bridging carboxylate groups; the Gd···Gd distance is 4.410(?)Å, indicating that there is no metal-metal bond in the complex. The average Gd—Ocarboxylate bond length is 2.333 Å. Each pair of carboxylate groups is coplanar with the two Gd3+ ions and the dihedral angle between the two planes is 89(?)°, showing the two planes to be almost perpendicular. The coordination polyhedron around the Gd3+ ion is a square antiprism, with four of the sites occupied by the carboxylate O atoms and the other four sites occupied by the O atoms of the four coordinated water molecules (mean Gd—Owater = 2.453 Å), completing an eightfold coordination. The arrangement of ions in the unit cell is shown in Fig 2. The perchlorate anions are disordered and reside in the cavities of the crystal. Two perchlorate O atoms form hydrogen bonds with the –NH3+ group and coordinated water molecules from two [Gd2(Ala)4(H2O)8]6+ cations. This hydrogen-bonded structure stabilizes the crystal packing.
The optic purity of L-alanine is 68.9%. Though the content of L-alanine is higher than that of D-alanine, the methyl groups are disordered over two positions corresponding to the D and L configurations of alanine in the complex. According to statistical results, the probability of methyl groups occupying two positions is equal. In addition, the two different orientations of the methyl groups can decrease their potential energy and enhance the symmetry of the crystal structure. Therefore, equal numbers of L– and D-alanine molecules were selected to form the dimeric cations with GdIII ions.
The structures of [Gd2(Pro)6(H2O)6](ClO4)6 (Pro os proline; Zheng et al., 1993) and [Gd(Gly)3(H2O)2]Cl3·H2O (Gly is glycine; Gao et al., 2001) have been reported. They both consist of one-dimensional chains in which two neighboring Gd3+ ions are connected by bridging carboxylate groups; the Gd···Gd distances are 4.722 and 4.765 Å, respectively. The mean Gd—Ocarboxylate bond lengths are 2.357 and 2.489 Å, respectively. By comparing the dimeric form with the chain structures, it is found that the Gd—Ocarboxylate bond lengths influence the distances between neighboring GdIII ions. The shorter mean Gd—Ocarboxylate length (2.333 Å) found in the dimeric structure leads to a Gd···Gd distance (4.410 Å) which is considerably shorter than corresponding distances found in the chain structures. In addition, this can make the dimeric complex more stable.