Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536801002276/om6000sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536801002276/om6000Isup2.hkl |
CCDC reference: 159862
Crystals Of (I) suitable for X-ray study were grown via the slow evaporation of an alcohol solution.
Data collection: P3 (Siemens, 1989); cell refinement: P3; data reduction: XDISK (Siemens, 1991); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1991); software used to prepare material for publication: SHELXL97.
Fig. 1. Numbering scheme and displacement ellipsoids for the title compound (50% probability level). |
C16H19ClN2O2 | Z = 2 |
Mr = 306.78 | F(000) = 324 |
Triclinic, P1 | Dx = 1.252 Mg m−3 |
a = 8.174 (2) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 8.760 (2) Å | Cell parameters from 34 reflections |
c = 11.793 (2) Å | θ = 13.0–15.0° |
α = 75.68 (2)° | µ = 0.24 mm−1 |
β = 85.77 (2)° | T = 290 K |
γ = 84.98 (2)° | Elongated prism, colourless |
V = 813.9 (3) Å3 | 0.45 × 0.40 × 0.25 mm |
Siemens P3/PC diffractometer | 2629 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.054 |
Graphite monochromator | θmax = 32.5°, θmin = 2.6° |
2θ/θ scans | h = −12→12 |
Absorption correction: integration (XPREP; Siemens, 1991) | k = −12→13 |
Tmin = 0.887, Tmax = 0.945 | l = 0→16 |
5630 measured reflections | 2 standard reflections every 98 reflections |
5401 independent reflections | intensity decay: 2% |
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)] = 0.038 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.072 | All H-atom parameters refined |
S = 0.91 | Calculated w = 1/[σ2(Fo2) + (0.0213P)2] where P Fo2 + 2Fc2)/3 |
5401 reflections | (Δ/σ)max = 0.004 |
266 parameters | Δρmax = 0.16 e Å−3 |
0 restraints | Δρmin = −0.12 e Å−3 |
C16H19ClN2O2 | γ = 84.98 (2)° |
Mr = 306.78 | V = 813.9 (3) Å3 |
Triclinic, P1 | Z = 2 |
a = 8.174 (2) Å | Mo Kα radiation |
b = 8.760 (2) Å | µ = 0.24 mm−1 |
c = 11.793 (2) Å | T = 290 K |
α = 75.68 (2)° | 0.45 × 0.40 × 0.25 mm |
β = 85.77 (2)° |
Siemens P3/PC diffractometer | 2629 reflections with I > 2σ(I) |
Absorption correction: integration (XPREP; Siemens, 1991) | Rint = 0.054 |
Tmin = 0.887, Tmax = 0.945 | 2 standard reflections every 98 reflections |
5630 measured reflections | intensity decay: 2% |
5401 independent reflections |
R[F2 > 2σ(F2)] = 0.038 | 0 restraints |
wR(F2) = 0.072 | All H-atom parameters refined |
S = 0.91 | Δρmax = 0.16 e Å−3 |
5401 reflections | Δρmin = −0.12 e Å−3 |
266 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
Cl | 0.20162 (4) | 0.98652 (4) | 0.24489 (3) | 0.07096 (12) | |
O1 | 0.20045 (9) | 1.33894 (9) | 0.00641 (6) | 0.05635 (19) | |
O2 | 0.27630 (9) | 1.10167 (9) | −0.03311 (7) | 0.0587 (2) | |
N1 | 0.47002 (12) | 1.06376 (11) | 0.31648 (9) | 0.0627 (3) | |
N2 | 0.62956 (12) | 1.34534 (11) | −0.01449 (8) | 0.0530 (2) | |
H2 | 0.7000 (15) | 1.4088 (14) | −0.0113 (10) | 0.061 (4)* | |
C2 | 0.38731 (13) | 1.08497 (12) | 0.22257 (10) | 0.0532 (3) | |
C3 | 0.42293 (12) | 1.18078 (11) | 0.10861 (9) | 0.0465 (2) | |
C4 | 0.57246 (12) | 1.25672 (11) | 0.09154 (9) | 0.0451 (2) | |
C5 | 0.82293 (14) | 1.30977 (14) | 0.18926 (11) | 0.0576 (3) | |
H5 | 0.8732 (18) | 1.3749 (16) | 0.1111 (13) | 0.092 (4)* | |
C6 | 0.90714 (17) | 1.29150 (16) | 0.28872 (12) | 0.0694 (4) | |
H6 | 1.0072 (17) | 1.3371 (15) | 0.2798 (11) | 0.080 (4)* | |
C7 | 0.84734 (18) | 1.19940 (17) | 0.39820 (12) | 0.0770 (4) | |
H7 | 0.9145 (18) | 1.1846 (16) | 0.4762 (13) | 0.093 (4)* | |
C8 | 0.70454 (17) | 1.12669 (17) | 0.40473 (12) | 0.0736 (4) | |
H8 | 0.6632 (16) | 1.0618 (16) | 0.4762 (12) | 0.081 (4)* | |
C9 | 0.67037 (12) | 1.23801 (12) | 0.19318 (9) | 0.0484 (2) | |
C10 | 0.61297 (14) | 1.14314 (13) | 0.30363 (9) | 0.0554 (3) | |
C11 | 0.29028 (13) | 1.21703 (12) | 0.02152 (9) | 0.0470 (2) | |
C12 | 0.14099 (17) | 1.12234 (18) | −0.11241 (12) | 0.0653 (3) | |
H12A | 0.0506 (15) | 1.1733 (13) | −0.0874 (10) | 0.054 (3)* | |
H12B | 0.1237 (16) | 1.0045 (16) | −0.1172 (11) | 0.078 (4)* | |
C13 | 0.1858 (2) | 1.2243 (2) | −0.23279 (13) | 0.0756 (4) | |
H13A | 0.1045 (18) | 1.2162 (16) | −0.2767 (12) | 0.077 (4)* | |
H13B | 0.2164 (17) | 1.3356 (18) | −0.2354 (11) | 0.085 (4)* | |
H13C | 0.286 (2) | 1.182 (2) | −0.2805 (15) | 0.121 (6)* | |
C14 | 0.56709 (14) | 1.35805 (14) | −0.12989 (9) | 0.0508 (3) | |
H14A | 0.4591 (13) | 1.4221 (12) | −0.1463 (9) | 0.046 (3)* | |
H14B | 0.5537 (14) | 1.2513 (14) | −0.1419 (9) | 0.060 (3)* | |
C15 | 0.68606 (15) | 1.44280 (16) | −0.22687 (9) | 0.0541 (3) | |
H15A | 0.8029 (16) | 1.3858 (14) | −0.2212 (10) | 0.065 (3)* | |
H15B | 0.7020 (14) | 1.5484 (14) | −0.2090 (10) | 0.065 (3)* | |
C16 | 0.62432 (18) | 1.4644 (2) | −0.34979 (11) | 0.0687 (4) | |
H16A | 0.5100 (18) | 1.5119 (16) | −0.3564 (11) | 0.085 (4)* | |
H16B | 0.6149 (17) | 1.3585 (17) | −0.3620 (12) | 0.084 (4)* | |
C17 | 0.7371 (3) | 1.5599 (3) | −0.44524 (14) | 0.1050 (7) | |
H17A | 0.702 (2) | 1.562 (2) | −0.5198 (16) | 0.111 (6)* | |
H17B | 0.734 (2) | 1.676 (2) | −0.4333 (16) | 0.135 (8)* | |
H17C | 0.839 (3) | 1.519 (3) | −0.4462 (18) | 0.150 (10)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cl | 0.05774 (18) | 0.0738 (2) | 0.0736 (2) | −0.02914 (15) | −0.00097 (15) | 0.00451 (15) |
O1 | 0.0517 (4) | 0.0541 (4) | 0.0622 (5) | −0.0045 (4) | −0.0050 (4) | −0.0112 (4) |
O2 | 0.0577 (5) | 0.0558 (5) | 0.0672 (5) | −0.0107 (4) | −0.0080 (4) | −0.0197 (4) |
N1 | 0.0593 (6) | 0.0682 (6) | 0.0530 (6) | −0.0196 (5) | −0.0014 (5) | 0.0044 (4) |
N2 | 0.0556 (5) | 0.0605 (6) | 0.0424 (5) | −0.0207 (5) | −0.0017 (4) | −0.0064 (4) |
C2 | 0.0498 (6) | 0.0449 (6) | 0.0604 (7) | −0.0139 (5) | 0.0015 (5) | −0.0016 (5) |
C3 | 0.0439 (5) | 0.0431 (5) | 0.0522 (6) | −0.0069 (4) | 0.0021 (5) | −0.0112 (4) |
C4 | 0.0449 (5) | 0.0439 (5) | 0.0458 (5) | −0.0074 (4) | 0.0026 (4) | −0.0095 (4) |
C5 | 0.0504 (6) | 0.0614 (7) | 0.0572 (7) | −0.0141 (5) | −0.0064 (5) | −0.0027 (5) |
C6 | 0.0592 (7) | 0.0781 (9) | 0.0691 (8) | −0.0209 (7) | −0.0131 (6) | −0.0063 (6) |
C7 | 0.0741 (9) | 0.0896 (10) | 0.0631 (8) | −0.0226 (7) | −0.0227 (7) | 0.0008 (7) |
C8 | 0.0723 (9) | 0.0863 (9) | 0.0532 (7) | −0.0200 (7) | −0.0097 (7) | 0.0070 (7) |
C9 | 0.0452 (5) | 0.0475 (6) | 0.0496 (6) | −0.0053 (4) | −0.0006 (5) | −0.0062 (5) |
C10 | 0.0548 (6) | 0.0590 (7) | 0.0476 (6) | −0.0125 (5) | −0.0018 (5) | −0.0013 (5) |
C11 | 0.0425 (5) | 0.0440 (6) | 0.0532 (6) | −0.0128 (5) | 0.0042 (5) | −0.0077 (5) |
C12 | 0.0585 (8) | 0.0732 (9) | 0.0689 (8) | −0.0187 (7) | −0.0060 (6) | −0.0206 (7) |
C13 | 0.0761 (10) | 0.0935 (11) | 0.0632 (9) | −0.0269 (8) | −0.0073 (8) | −0.0219 (8) |
C14 | 0.0479 (6) | 0.0570 (7) | 0.0478 (6) | −0.0138 (5) | 0.0041 (5) | −0.0118 (5) |
C15 | 0.0495 (6) | 0.0698 (8) | 0.0450 (6) | −0.0175 (6) | 0.0047 (5) | −0.0151 (5) |
C16 | 0.0642 (8) | 0.0930 (10) | 0.0503 (7) | −0.0269 (7) | 0.0040 (6) | −0.0148 (7) |
C17 | 0.1080 (16) | 0.164 (2) | 0.0427 (8) | −0.0602 (15) | 0.0041 (9) | −0.0089 (10) |
Cl—C2 | 1.7818 (11) | C8—H8 | 0.950 (14) |
O1—C11 | 1.2245 (13) | C9—C10 | 1.4318 (15) |
O2—C11 | 1.3425 (13) | C12—C13 | 1.517 (2) |
O2—C12 | 1.4712 (15) | C12—H12A | 0.898 (11) |
N1—C2 | 1.3057 (14) | C12—H12B | 1.070 (13) |
N1—C10 | 1.3914 (14) | C13—H13A | 0.889 (14) |
N2—C4 | 1.3715 (13) | C13—H13B | 1.020 (15) |
N2—C14 | 1.4638 (15) | C13—H13C | 1.054 (19) |
N2—H2 | 0.843 (12) | C14—C15 | 1.5321 (15) |
C2—C3 | 1.4222 (14) | C14—H14A | 1.008 (11) |
C3—C4 | 1.4202 (14) | C14—H14B | 0.996 (12) |
C3—C11 | 1.5080 (15) | C15—C16 | 1.5322 (17) |
C4—C9 | 1.4579 (15) | C15—H15A | 1.037 (13) |
C5—C6 | 1.3719 (18) | C15—H15B | 1.020 (12) |
C5—C9 | 1.4376 (15) | C16—C17 | 1.527 (2) |
C5—H5 | 1.034 (15) | C16—H16A | 0.990 (14) |
C6—C7 | 1.4203 (19) | C16—H16B | 0.984 (14) |
C6—H6 | 0.929 (13) | C17—H17A | 0.941 (18) |
C7—C8 | 1.3662 (18) | C17—H17B | 1.059 (19) |
C7—H7 | 1.080 (14) | C17—H17C | 0.88 (2) |
C8—C10 | 1.4250 (17) | ||
C11—O2—C12 | 117.34 (10) | O2—C12—H12A | 112.4 (7) |
C2—N1—C10 | 116.14 (9) | C13—C12—H12A | 104.4 (7) |
C4—N2—C14 | 127.57 (9) | O2—C12—H12B | 103.6 (7) |
C4—N2—H2 | 115.5 (8) | C13—C12—H12B | 110.8 (7) |
C14—N2—H2 | 116.4 (8) | H12A—C12—H12B | 114.2 (10) |
N1—C2—C3 | 128.43 (10) | C12—C13—H13A | 104.6 (9) |
N1—C2—Cl | 114.37 (8) | C12—C13—H13B | 116.1 (8) |
C3—C2—Cl | 117.13 (9) | H13A—C13—H13B | 116.9 (12) |
C4—C3—C2 | 116.56 (10) | C12—C13—H13C | 117.0 (10) |
C4—C3—C11 | 124.01 (9) | H13A—C13—H13C | 99.7 (12) |
C2—C3—C11 | 118.59 (9) | H13B—C13—H13C | 101.9 (12) |
N2—C4—C3 | 123.84 (10) | N2—C14—C15 | 110.43 (9) |
N2—C4—C9 | 118.58 (9) | N2—C14—H14A | 115.9 (6) |
C3—C4—C9 | 117.57 (9) | C15—C14—H14A | 103.6 (6) |
C6—C5—C9 | 120.92 (11) | N2—C14—H14B | 110.6 (6) |
C6—C5—H5 | 118.2 (8) | C15—C14—H14B | 108.6 (6) |
C9—C5—H5 | 120.9 (8) | H14A—C14—H14B | 107.3 (9) |
C5—C6—C7 | 120.99 (12) | C16—C15—C14 | 112.80 (9) |
C5—C6—H6 | 116.8 (8) | C16—C15—H15A | 110.6 (7) |
C7—C6—H6 | 122.1 (8) | C14—C15—H15A | 111.4 (6) |
C8—C7—C6 | 119.68 (13) | C16—C15—H15B | 111.8 (7) |
C8—C7—H7 | 119.5 (8) | C14—C15—H15B | 106.4 (6) |
C6—C7—H7 | 120.8 (8) | H15A—C15—H15B | 103.5 (9) |
C7—C8—C10 | 121.11 (12) | C17—C16—C15 | 112.46 (12) |
C7—C8—H8 | 121.6 (8) | C17—C16—H16A | 110.1 (8) |
C10—C8—H8 | 117.2 (8) | C15—C16—H16A | 112.5 (8) |
C10—C9—C5 | 117.51 (10) | C17—C16—H16B | 111.1 (8) |
C10—C9—C4 | 118.84 (9) | C15—C16—H16B | 107.4 (8) |
C5—C9—C4 | 123.65 (9) | H16A—C16—H16B | 102.9 (11) |
N1—C10—C8 | 117.95 (10) | C16—C17—H17A | 110.2 (10) |
N1—C10—C9 | 122.30 (10) | C16—C17—H17B | 108.4 (11) |
C8—C10—C9 | 119.75 (10) | H17A—C17—H17B | 110.5 (14) |
O1—C11—O2 | 123.84 (10) | C16—C17—H17C | 113.7 (15) |
O1—C11—C3 | 122.10 (10) | H17A—C17—H17C | 104.0 (17) |
O2—C11—C3 | 114.01 (9) | H17B—C17—H17C | 110.0 (18) |
O2—C12—C13 | 111.68 (11) | ||
C10—N1—C2—C3 | −0.99 (18) | C3—C4—C9—C5 | −179.12 (11) |
C10—N1—C2—Cl | −177.85 (9) | C2—N1—C10—C8 | 178.32 (12) |
N1—C2—C3—C4 | 4.10 (18) | C2—N1—C10—C9 | −2.31 (17) |
Cl—C2—C3—C4 | −179.10 (8) | C7—C8—C10—N1 | 179.04 (13) |
N1—C2—C3—C11 | −165.82 (11) | C7—C8—C10—C9 | −0.3 (2) |
Cl—C2—C3—C11 | 10.98 (14) | C5—C9—C10—N1 | −177.68 (11) |
C14—N2—C4—C3 | −10.77 (18) | C4—C9—C10—N1 | 2.29 (17) |
C14—N2—C4—C9 | 168.94 (10) | C5—C9—C10—C8 | 1.68 (17) |
C2—C3—C4—N2 | 175.99 (10) | C4—C9—C10—C8 | −178.35 (11) |
C11—C3—C4—N2 | −14.70 (17) | C12—O2—C11—O1 | −2.17 (14) |
C2—C3—C4—C9 | −3.73 (14) | C12—O2—C11—C3 | 175.19 (9) |
C11—C3—C4—C9 | 165.58 (10) | C4—C3—C11—O1 | −73.37 (14) |
C9—C5—C6—C7 | 0.9 (2) | C2—C3—C11—O1 | 95.74 (12) |
C5—C6—C7—C8 | 0.5 (2) | C4—C3—C11—O2 | 109.21 (11) |
C6—C7—C8—C10 | −0.8 (2) | C2—C3—C11—O2 | −81.67 (12) |
C6—C5—C9—C10 | −1.95 (18) | C11—O2—C12—C13 | 82.83 (15) |
C6—C5—C9—C4 | 178.08 (11) | C4—N2—C14—C15 | −168.83 (11) |
N2—C4—C9—C10 | −178.82 (10) | N2—C14—C15—C16 | −178.15 (12) |
C3—C4—C9—C10 | 0.92 (15) | C14—C15—C16—C17 | 175.63 (17) |
N2—C4—C9—C5 | 1.15 (16) |
Experimental details
Crystal data | |
Chemical formula | C16H19ClN2O2 |
Mr | 306.78 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 290 |
a, b, c (Å) | 8.174 (2), 8.760 (2), 11.793 (2) |
α, β, γ (°) | 75.68 (2), 85.77 (2), 84.98 (2) |
V (Å3) | 813.9 (3) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.24 |
Crystal size (mm) | 0.45 × 0.40 × 0.25 |
Data collection | |
Diffractometer | Siemens P3/PC diffractometer |
Absorption correction | Integration (XPREP; Siemens, 1991) |
Tmin, Tmax | 0.887, 0.945 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5630, 5401, 2629 |
Rint | 0.054 |
(sin θ/λ)max (Å−1) | 0.756 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.038, 0.072, 0.91 |
No. of reflections | 5401 |
No. of parameters | 266 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.16, −0.12 |
Computer programs: P3 (Siemens, 1989), P3, XDISK (Siemens, 1991), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), XP (Siemens, 1991), SHELXL97.
Cl—C2 | 1.7818 (11) | C4—C9 | 1.4579 (15) |
O1—C11 | 1.2245 (13) | C5—C6 | 1.3719 (18) |
O2—C11 | 1.3425 (13) | C5—C9 | 1.4376 (15) |
O2—C12 | 1.4712 (15) | C6—C7 | 1.4203 (19) |
N1—C2 | 1.3057 (14) | C7—C8 | 1.3662 (18) |
N1—C10 | 1.3914 (14) | C8—C10 | 1.4250 (17) |
N2—C4 | 1.3715 (13) | C9—C10 | 1.4318 (15) |
N2—C14 | 1.4638 (15) | C12—C13 | 1.517 (2) |
C2—C3 | 1.4222 (14) | C14—C15 | 1.5321 (15) |
C3—C4 | 1.4202 (14) | C15—C16 | 1.5322 (17) |
C3—C11 | 1.5080 (15) | C16—C17 | 1.527 (2) |
C11—O2—C12 | 117.34 (10) | C7—C8—C10 | 121.11 (12) |
C2—N1—C10 | 116.14 (9) | C10—C9—C5 | 117.51 (10) |
C4—N2—C14 | 127.57 (9) | C10—C9—C4 | 118.84 (9) |
N1—C2—C3 | 128.43 (10) | C5—C9—C4 | 123.65 (9) |
N1—C2—Cl | 114.37 (8) | N1—C10—C8 | 117.95 (10) |
C3—C2—Cl | 117.13 (9) | N1—C10—C9 | 122.30 (10) |
C4—C3—C2 | 116.56 (10) | C8—C10—C9 | 119.75 (10) |
C4—C3—C11 | 124.01 (9) | O1—C11—O2 | 123.84 (10) |
C2—C3—C11 | 118.59 (9) | O1—C11—C3 | 122.10 (10) |
N2—C4—C3 | 123.84 (10) | O2—C11—C3 | 114.01 (9) |
N2—C4—C9 | 118.58 (9) | O2—C12—C13 | 111.68 (11) |
C3—C4—C9 | 117.57 (9) | N2—C14—C15 | 110.43 (9) |
C6—C5—C9 | 120.92 (11) | C16—C15—C14 | 112.80 (9) |
C5—C6—C7 | 120.99 (12) | C17—C16—C15 | 112.46 (12) |
C8—C7—C6 | 119.68 (13) |
During investigation of the reaction of the ethyl 2,4-dichloroquinoline-3-carboxylate with nucleophilic reagents, it was found that this compound reacts with sodium acetate giving ethyl chloro-2-oxo-1,2-dihydroquinoline-3-carboxylate, as identified in previous work (Ukrainets et al., 1995). However, X-ray diffraction analysis has shown the product of this reaction to be ethyl 4-butylamino-2-chloroquinoline-3-carboxylate, (I), the structure of which is presented here.
The quinoline fragment of (I) (Fig. 1) is planar within 0.02 Å. The Cl atom lies in the plane of the quinoline bicycle. The carboxyl group is rotated by 79.08 (4)° with respect to the quinoline fragment [the C2—C3—C11—O1 and C2—C3—C11—O2 torsion angles are 95.7 (1) and -81.7 (1)°, respectively]. The non-H atoms of the butylamine fragment are coplanar within 0.03 Å and this plane is rotated by 9.1 (2)° with respect to the quinoline fragment. This rotation may be caused by sterical repulsion between the H5 and H2 atoms, [the distance is 2.05 (2) Å and the sum of the van der Waals radii is 2.32 Å].
A noticeable altering of the C—C (C—N) bonds is observed within the quinoline fragment, i.e. the N1—C2, C3—C4, C5—C6 and C7—C8 bonds are shorter and the remaining bonds are longer than the mean value for aromatic C—C bonds (1.387 Å; Bürgi & Dunitz, 1994). Such peculiarity is observed also for other quinoline-containing structures (Merlino, 1968; Blackburn et al., 1996; Chiang et al., 1991; Gdaniec et al., 1980; Gdaniec & Dziembowska, 1980; Ahmet et al., 1995).