Structure of the molecular complexes of 18-crown-6 with 1,2,5-oxadiazole derivatives

Article abstract of DOI:10.1023/A:1012425408024

This paper reports on an X-ray diffraction analysis of host-guest type molecular complexes of 18-crown-6 with 1,2,5-oxadiazole derivatives: ethyl 4-amino-1,2,5-oxadiazole-3-carboxylic ether (1:1) (complex I), 4-(2-chloroethylamino)-1,2,5-oxadiazole-3-carboxylic acid hydrazide (1:2) (complex II), and 4-amino-1,2,5-oxadiazole-3-carboxylic acid amide monohydrate (1:1:1) (complex III). Crystals I are monoclinic with cell parameters a = 8.960(2), b = 18.118(4), c = 14.405(3) A, β = 106.9(3)°, space group P2₁/n, R = 0.054 for 4082 reflections. The 18-crown-6 and guest molecules are linked by hydrogen bonds of NH...O(crown) and CH...O(crown) types based on the "head-to-tail" principle, alternating in infinite chains along the y axis in the crystal. Crystals II are triclinic with cell parameters a = 8.615(2), b = 9.249(2), c = 10.987(2) A, α = 106.86(3), β = 95.25(3), γ = 97.74(3)°, space group P1, R = 0.046 for 3006 reflections. The guest molecules are united into dimers by N-H...O=C hydrogen bonds. The 18-crown-6 molecules and the dimer associates of the guest form chains along [110] in the crystal. Crystals III are monoclinic with cell dimensions a = 13.238(3), b = 19.004(4), c = 8.485(2) A, β = 100.75(3)°, space group Cc, R = 0.051 for 2032 reflections. The crown ether molecule is disordered over two positions. The NH...O=C and NH...N type hydrogen bonds link the guest molecules into chains. The water molecules serve to bridge the chains with crown ether molecules, forming ribbons whose axis lies along the z direction in the crystal.

Full text of DOI:10.1023/A:1012425408024

Journal of Structural Chemistry, Vol. 42, No. 3, pp. 459-469, 2001
Original Russian Text Copyright © 2001 by M. S. Fonar, Yu. A. Simonov, V. H. Kravtsov, J. Lipkowski, A. A. Javolowski, and É. V. Ganin
STRUCTURE OF THE MOLECULAR
COMPLEXES OF 18-CROWN-6 WITH
1,2,5-OXADIAZOLE DERIVATIVES
UDC 548.737:547.898
M. S. Fonar, Yu. A. Simonov, V. H. Kravtsov,
J. Lipkowski, A. A. Javolowski, and É. V. Ganin
This paper reports on an X-ray diffraction analysis of host–guest type molecular complexes of 18-crown-6
with 1,2,5-oxadiazole derivatives: ethyl 4-amino-1,2,5-oxadiazole-3-carboxylic ether (1:1) (complex I),
4-(2-chloroethylamino)-1,2,5-oxadiazole-3-carboxylic acid hydrazide (1:2) (complex II), and 4-amino-
1,2,5-oxadiazole-3-carboxylic acid amide monohydrate (1:1:1) (complex III). Crystals I are monoclinic
with cell parameters a = 8.960(2), b = 18.118(4), c = 14.405(3) Å, β = 106.9(3)°, space group P2 /n,
1
R = 0.054 for 4082 reflections. The 18-crown-6 and guest molecules are linked by hydrogen bonds of
…
…
NH O(crown) and CH O(crown) types based on the ‘‘head-to-tail’’ principle, alternating in infinite
chains along the y axis in the crystal. Crystals II are triclinic with cell parameters a = 8.615(2), b =
_
9.249(2), c = 10.987(2) Å, α = 106.86(3), β = 95.25(3), γ = 97.74(3)°, space group P1, R = 0.046 for
…
3006 reflections. The guest molecules are united into dimers by N–H O=C hydrogen bonds. The
18-crown-6 molecules and the dimer associates of the guest form chains along [110] in the crystal.
Crystals III are monoclinic with cell dimensions a = 13.238(3), b = 19.004(4), c = 8.485(2) Å, β =
100.75(3)°, space group Cc, R = 0.051 for 2032 reflections. The crown ether molecule is disordered over
…
…
two positions. The NH O=C and NH N type hydrogen bonds link the guest molecules into chains. The
water molecules serve to bridge the chains with crown ether molecules, forming ribbons whose axis lies
along the z direction in the crystal.
There was extensive literature on crown ether complexes with metals and neutral organic molecules [1, 2]. It was
established [2] that a small neutral molecule can form adducts with crown ethers if it has a high dipole moment and proton
donors capable of hydrogen bonding with crown ether oxygens provided it leads to structure complementarity. Also, it is
known that crown ether complexes with neutral organic molecules exhibit some properties characteristic of biologically
controlled processes and enzyme catalysis [3]. Moreover, such complexes are models for understanding the role of weak
…
C–H O interactions in stabilization of supramolecular associates [4].
In this series, complexes of 18-crown-6 (H — host) and some of its analogs with five-membered heterocyclic
molecules (G — guest) — di-, tri-, and tetrazole derivatives — were studied [5-7]. In these complexes, interaction with
crown ether is mediated by the donor groups NH , NH, CH. The presence of two or more proton donor centers in the
2
guest ensures a chain structure with alternating 18-crown-6 and guest molecules. In the complex of 18-crown-6 with
3,4-diamino-1,2,5-oxadiazole [5], both amino groups are coordinated to different 18-crown-6 molecules (in one case, via
the bridging water molecule), linking the C and D 18-crown-ether molecules into a chain. In a complex with the cis-anti-cis
i
3d
isomer of dicyclohexano-18-crown-6, the guest molecule is bonded in the same way to two crown ether molecules, and
the polymer chain is of the form –H–G–H–. Also, dimerization of guests such as 1,2,4-1H-triazole and 5-amino-1H-tetrazole
…
…
via the hydrogen bonds CH N [6] or NH N [7] is possible and leads to a chain structure of –H–G–G–H– type. In the
Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland. Institute of Applied Physics,
Moldova Academy of Sciences, Kishinev. Institute of Environmetal and Human Protection, Ministry of Education and
National Academy of Sciences of Ukraine. Translated from Zhurnal Strukturnoi Khimii, Vol. 42, No. 3, pp. 550-562,
May-June, 2001. Original article submitted May 22, 2000.
©
0022-4766/01/4203-0459$25.00 2001 Plenum Publishing Corporation
459

crystal structure of the 18-crown-6 complex with 5-amino-1,2,4-triazole, the –H–G–H–G– and –G–G–G– chains differing
in composition are linked into a three-dimensional net via the guest molecules. In most cases, 18-crown-6 forms
centrosymmetric complexes with four or six oxygens participating in the interaction with the small molecule. In some cases,
however, only one side of the macrocycle is involved [8], or the sides are nonequivalent [9].
The aim of this publication is to study the crystal structures of three new complexes of 18-crown-6 with
1,2,5-oxadiazoles having substituents in the 3 or 4 position of the oxadiazole ring: amino and ester group (guest 1, complex I);
hydrazide and chloroethylamine group (guest 2, complex II); amino and amide groups (guest 3, complex III).
Guest molecules G1-G3 have the amino group, which, according to numerous structural data [10], is complementary
to the macrocycle of 18-crown-6 and its analogs and generally coordinates the oxygen atoms of the host molecule separated
by the oxyethylene fragment.
EXPERIMENTAL
Ethyl 4-amino-1,2,5-oxadiazole-3-carboxylic ether was prepared by the procedure described in [11].
Synthesis of 4-(2-chloroethylamino)-1,2,5-oxadiazole-3-carboxylic acid hydrazide. 4-(2-oxyethylamino)-1,2,5-
oxadiazole-3-carboxylic acid (1.73 g, 0.01 mol) [11] was dissolved in anhydrous tetrahydrofuran (100 ml) with a catalytic
amount of dimethylformamide. Thionyl chloride (2.8 ml) was added to the solution for 1 h, while the temperature of the
mixture was kept below 60°C. The solvents and excess thionyl chloride were distilled off. The residue was dissolved in
ethanol, and the mixture was filtered. To the filtrate was added 50 ml of 30% aqueous hydrazine. The precipitate was
filtered off, washed with water, and dried in air. Yield 1.74 g (85%).
Synthesis of 4-amino-1,2,5-oxadiazole-3-carboxylic acid amide. Gaseous ammonia was bubbled through a saturated
alcohol solution of ethyl 4-amino-1,2,5-oxadiazolo-3-carboxylic ether (1.57 g, 0.01 mol) until the solution was saturated.
The reaction mixture was stored at room temperature until a crystalline precipitate settled. The precipitate was filtered off
and recrystallized from alcohol. Yield 1.28 g (90%).
Syntheses of complexes I-III. Complexes I-III were prepared by analogous procedures. An appropriate guest
(0.1 mmol) and 18-crown-6 (26 mg, 0.1 mmol) were dissolved at 64°C in methanol (2 ml), then benzene (5 ml) was added,
and the mixture was allowed to stay until the solvents spontaneously evaporated. The crystals suitable for an X-ray analysis
were obtained by recrystallization of the resulting crystalline mass from a mixture of ethyl acetate (5 ml) and heptane
(3 ml). T is 81-82°C for I, 108-109°C for II, and 157-158°C for III.
m
Element analysis data:
Analysis
C
H
N
Cl
−
Found (%)
Calculated for C H N O (I)
48.42 7.50 10.04
48.45 7.41 9.97
−
17 31
3 9
Found (%)
39.23 6.05 20.70 10.56
Calculated for C H Cl N O (II) 39.12 5.97 20.73 10.50
22 40
2 10 10
Found (%)
Calculated for C H N O (III)
44.53 7.35 13.57
43.90 7.37 13.65
−
−
15 30
4 9
Crystal and refinement data and experimental conditions are listed in Table 1. The least-squares refinement used
31 reflections (2θ 13.74-37.79°) for I, 25 reflections (2θ 13.29-32.50°) for II, and 32 reflections (2θ 18.20-43.47°) for III
(KUMA KM-4 diffractometer, CuK radiation). The structures were solved by direct methods. The calculations used the
α
460

TABLE 1. Crystal Data, Data Collection Details, and Refinement Parameters for I-III
Complex II III
Molecular formula C H Cl N O C H N O
15 30 4 9
I
C H N O
17 31
3
9
22 40
2
10 10
M
421.45
Monoclinic
675.54
410.43
Monoclinic
Crystal system
Space group
Triclinic
_
P2 /n
P1
Cc
1
Lattice parameters
a, Å
b, Å
c, Å
α, deg
8.960(2)
18.118(4)
14.405(3)
90
106.90(3)
90
2237.5(3)
4
1.251
8.615(2)
9.249(2)
10.987(2)
106.86(3)
95.25(3)
97.74(3)
822.3(3)
1
13.238(3)
19.004(4)
8.485(2)
90
100.75(3)
90
2097.2(8)
4
1.300
β, deg
γ, deg
3
V, Å
Z
3
d
, g/cm
1.364
2.342
calc
−1
µ, mm
0.859
0.915
F (000)
904
356
880
Crystal size, mm
θ range from data collected, deg
Index ranges from data collected
0.25×0.80×1.50
4.03-70.15
−10 < h < 0,
−22 < k < 0,
−16 < l < 17
ω / 2θ
0.20×0.30×0.30
4.24-68.62
−10 < h < 10,
−10 < k < 11,
−13 < l < 0
ω / 2θ
0.25×0.35×2.30
4.12-69.13
−10 < h < 15,
0 < k < 23,
0 < l < 10
ω / 2θ
Scan mode
Reflections collected
4367
4082 [0.0116]
1.051
3177
3006 [0.0263]
0.921
2034
2032 [0.0660]
1.051
Unique reflections, [R ]
int
2
GooF S (on F )
Refinement method
2
Full-matrix on F
Final R indices from reflections
with [I > 2σ(I)]
R = 0.0540
R = 0.0463
R = 0.0505
1
1
1
wR = 0.1641
wR = 0.1096
wR = 0.1343
2
2
2
Final R indices (all data)
R = 0.0739
R = 0.1478
R = 0.0548
1
1
1
wR = 0.1799
wR = 0.1388
wR = 0.1396
2
2
2
2
2
2
2
2
w = I/[σ (Fo ) + (ap) + bp], p = (Max (Fo , 0) + 2F )/ 3
c
a = 0.1215
b = 0.1592
0.355, –0.218
a = 0.0659
b = 0
0.315, –0.237
a = 0.1155
b = 0.2934
0.222, –0.280
–3
Residual peaks ∆ρ , ∆ρ , eÅ
max
min
SHELXL-97 program [12]. All hydrogen atoms in the structure were localized on difference electron density maps. For
refinement, the methyl and methylene hydrogens were placed at the calculated ideal positions and refined as atoms tightly
bonded to the corresponding carbon atom. The NH and NH hydrogens localized on the difference maps were also refined
2
in a rigid group approximation. The positions refined individually were the positions of the hydrogen atoms of the terminal
amino group (complex II) and of the water hydrogens (complex III). The isotropic thermal parameters of the CH and
3
water hydrogen atoms were taken to be equal in magnitude: 1.5 U of the nonhydrogen atoms bonded to the H atoms and
eq
2
1.2 U for the rest of the hydrogen atoms, respectively. The full-matrix least-squares refinement on F used the weighting
eq
schemes given in Table 1. The final coordinates of the basic nonhydrogen atoms, anisotropic thermal parameters, and full
geometry of the complexes were deposited at the Cambridge Crystallographic Data Center as CCDC Ref. Nos. 143357-143359.
The geometrical parameters of the complexes are listed in Table 2; the hydrogen bond parameters are given in Table 3.
461

TABLE 2. Interatomic Distances d (Å) and Bond and Torsion Angles (deg) for I-III
Bond
I
II
III
Bond
I
II
III
O(1)–C(2)
C(2)–C(3)
C(3)–O(4)
O(4)–C(5)
C(5)–C(6)
C(6)–O(7)
O(7)–C(8)
C(8)–C(9)#1
O(1)–C(9)
C(8)–C(9)
1.416(3)
1.480(4)
1.417(3)
1.423(3)
1.482(4)
1.407(3)
1.409(3)
—
1.409(4)
1.492(6)
1.425(4)
1.408(4)
1.485(6)
1.421(4)
1.407(4)
1.483(6)
1.421(4)
—
1.379(14)
1.422(9)
1.477(17)
1.412(9)
1.418(9)
1.462(11)
1.389(10)
—
C(9)–O(10)
O(10)–C(11)
C(11)–C(12)
C(12)–O(13)
O(13)–C(14)
C(14)–C(15)
C(15)–O(16)
O(16)–C(17)
C(17)–C(18)
O(1)–C(18)
1.414(3)
1.414(3)
1.479(3)
1.419(3)
1.407(3)
1.486(4)
1.422(3)
1.413(3)
1.481(4)
1.410(3)
—
—
—
—
—
—
—
—
—
—
1.424(6)
1.448(9)
1.486(12)
1.407(7)
1.360(11)
1.517(13)
1.406(7)
1.408(12)
1.518(14)
1.422(9)
—
1.468(3)
—
1.499(11)
Angle
1
I
II
III
2
3
4
C(18)–O(1)–C(2)
O(1)–C(2)–C(3)
O(4)–C(3)–C(2)
C(3)–O(4)–C(5)
O(4)–C(5)–C(6)
O(7)–C(6)–C(5)
C(6)–O(7)–C(8)
O(7)–C(8)–C(9)#1
O(1)–C(9)–C(8)#1
C(2)–O(1)–C(9)
O(7)–C(8)–C(9)
O(10)–C(9)–C(8)
C(9)–O(10)–C(11)
O(10)–C(11)–C(12)
O(13)–C(12)–C(11)
C(14)–O(13)–C(12)
O(13)–C(14)–C(15)
O(16)–C(15)–C(14)
C(17)–O(16)–C(15)
O(16)–C(17)–C(18)
O(1)–C(18)–C(17)
C(18)–O(1)–C(2)–C(3)
C(9)–O(1)–C(2)–C(3)
O(1)–C(2)–C(3)–O(4)
C(2)–C(3)–O(4)–C(5)
C(3)–O(4)–C(5)–C(6)
O(4)–C(5)–C(6)–O(7)
C(5)–C(6)–O(7)–C(8)
C(6)–O(7)–C(8)–C(9)#1
113.3(2)
109.1(2)
109.8(2)
112.9(2)
109.9(2)
108.7(2)
112.9(2)
—
—
109.1(3)
108.8(3)
112.3(3)
109.3(3)
109.8(3)
113.6(3)
109.7(3)
109.2(3)
112.5(3)
—
113.6(8)
111.9(8)
112.8(7)
114.1(5)
109.5(5)
110.2(5)
112.3(6)
—
—
—
—
—
109.6(2)
110.1(2)
112.4(2)
109.5(2)
109.7(2)
112.7(2)
108.4(2)
109.3(2)
112.9(2)
110.0(2)
109.1(2)
–175.2(2)
—
71.4(3)
177.9(2)
–178.3(2)
–68.4(3)
176.6(2)
—
111.0(5)
109.0(5)
112.0(5)
109(5)
108.4(5)
112.6(7)
111.9(8)
108.3(6)
113.3(7)
108.4(7)
107.8(6)
–177.2(7)
—
–62.8(1)
169.1(7)
175.0(5)
63.0(6)
–173.8(5)
—
—
—
—
—
—
—
—
—
—
—
—
180.0(3)
–67.4(4)
178.3(3)
175.4(3)
63.5(2)
–178.4(3)
–173.7(3)
–69.5(5)
175.6(3)
—
O(7)–C(8)–C(9)#1–O(1)#1
C(8)–C(9)#1–O(1)#1–C(2)#1
C(6)–O(7)–C(8)–C(9)
O(7)–C(8)–C(9)–O(10)
C(8)–C(9)–O(10)–C(11)
C(9)–O(10)–C(11)–C(12)
—
—
–178.6(2)
69.6(2)
–176.4(2)
178.2(2)
—
—
–179.9(5)
–66.0(6)
–173.3(5)
–170.2(5)
—
—
—
462

TABLE 2 (Continued)
1
2
3
4
O(10)–C(11)–C(12)–O(13)
O(11)–C(12)–O(13)–C(14)
C(12)–O(13)–C(14)–C(15)
O(13)–C(14)–C(15)–O(16)
C(14)–C(15)–O(16)–C(17)
C(15)–O(16)–C(17)–C(18)
O(16)–C(17)–C(18)–O(1)
C(17)–C(18)–O(1)–C(2)
–68.6(2)
–174.3(2)
–178.7(2)
67.3(2)
177.4(2)
173.1(2)
–71.5(2)
178.3(2)
—
—
—
—
—
—
—
—
63.5(7)
169.3(6)
169.0(6)
–63.8(10)
–176.8(7)
180.0(6)
69.2(8)
–179.8(9)
Ethyl 4-amino-1,2,5-oxadiazole-3-carboxylic ether (G1)
Bond
d, Å
Angle
ω, deg
O(1g)–N(1g)
O(1g)–N(2g)
O(2g)–C(1g)
O(3g)–C(1g)
O(3g)–C(4g)
N(1g)–C(3g)
N(2g)–C(2g)
N(3g)–C(2g)
C(1g)–C(3g)
C(2g)–C(3g)
C(4g)–C(5g)
1.352(3)
1.412(3)
1.191(2)
1.314(2)
1.479(3)
1.293(3)
1.310(3)
1.334(2)
1.477(3)
1.433(3)
1.468(5)
N(1g)–O(1g)–N(2g)
C(1g)–O(3g)–C(4g)
C(3g)–N(1g)–O(1g)
C(2g)–N(2g)–O(1g)
O(2g)–C(1g)–O(3g)
O(2g)–C(1g)–C(3g)
O(3g)–C(1g)–C(3g)
N(2g)–C(2g)–N(3g)
N(2g)–C(2g)–C(3g)
N(3g)–C(2g)–C(3g)
N(1g)–C(3g)–C(2g)
N(1g)–C(3g)–C(1g)
C(2g)–C(3g)–C(1g)
C(5g)–C(4g)–O(3g)
111.9(2)
116.7(2)
105.4(2)
104.4(2)
125.9(2)
122.1(2)
112.0(2)
123.5(2)
108.0(2)
128.4(2)
110.4(2)
122.0(2)
127.6(2)
108.8(2)
4-(2-chloroethylamino)-1,2,5-oxadiazole-3-carboxylic acid hydrazide (G2)
1
2
3
4
Cl(1g)–C(5g)
O(1g)–N(1g)
O(1g)–N(2g)
O(2g)–C(1g)
N(1g)–C(3g)
N(2g)–C(2g)
N(3g)–C(2g)
N(3g)–C(4g)
N(4g)–C(1g)
N(4g)–N(5g)
C(1g)–C(3g)
C(2g)–C(3g)
C(4g)–C(5g)
1.782(4)
1.375(3)
1.403(4)
1.225(4)
1.296(4)
1.313(4)
1.347(4)
1.440(4)
1.310(4)
1.421(4)
1.493(4)
1.422(4)
1.504(5)
N(1g)–O(1g)–N(2g)
C(3g)–N(1g)–O(1g)
C(2g)–N(2g)–O(1g)
C(2g)–N(3g)–C(4g)
C(1g)–N(4g)–N(5g)
O(2g)–C(1g)–N(4g)
O(2g)–C(1g)–C(3g)
N(4g)–C(1g)–C(3g)
N(2g)–C(2g)–N(3g)
N(2g)–C(2g)–C(3g)
N(3g)–C(2g)–C(3g)
N(1g)–C(3g)–C(2g)
N(1g)–C(3g)–C(1g)
C(2g)–C(3g)–C(1g)
N(3g)–C(4g)–C(5g)
C(4g)–C(5g)–Cl(1g)
110.7(2)
106.1(3)
104.6(3)
123.4(3)
119.8(3)
126.7(3)
117.6(3)
115.7(3)
124.7(3)
109.2(3)
126.1(3)
109.4(3)
124.0(3)
126.5(3)
113.6(3)
111.3(2)
4-(2-chloroethylamino)-1,2,5-oxadiazole-3-carboxylic acid amine (G3)
O(1g)–N(1g)
O(1g)–N(2g)
O(2g)–C(1g)
1.379(4)
1.394(4)
1.235(4)
N(1g)–O(1g)–N(2g)
C(3g)–N(1g)–O(1g)
C(2g)–N(2g)–O(1g)
110.3(3)
106.5(3)
104.9(3)
463

TABLE 2 (Continued)
1
2
3
4
N(1g)–C(3g)
N(2g)–C(2g)
N(3g)–C(2g)
N(4g)–C(1g)
C(1g)–C(3g)
C(2g)–C(3g)
1.287(4)
1.311(5)
1.352(5)
1.225(4)
1.509(4)
1.425(4)
N(4g)–C(1g)–O(2g)
N(4g)–C(1g)–C(3g)
O(2g)–C(1g)–C(3g)
N(2g)–C(2g)–N(3g)
N(2g)–C(2g)–C(3g)
N(3g)–C(2g)–C(3g)
N(1g)–C(3g)–C(2g)
N(1g)–C(3g)–C(1g)
C(2g)–C(3g)–C(1g)
127.0(3)
118.5(3)
114.5(3)
124.1(3)
109.2(3)
126.5(3)
109.1(3)
122.1(3)
128.8(3)
Note. Symmetry operation: #1 −x+2, −y+1, −z.
TABLE 3. Geometrical Parameters of Hydrogen Bonds in I-III
…
d(D–H), Å
…
…
DHA, deg
Donor–H Acceptor
d(H A), Å
d(D A), Å
Complex I
N(3g)–H(1N3)...O(4)
N(3g)–H(2N3)...O(16)
N(3g)–N(2N3)...O(2g)
C(4g)–H(4g1)...O(1)#1
C(5g)–H(5g2)...O(7)#1
C(6)–H(6a)...N(2g)
0.90
0.93
0.93
0.97
0.96
0.97
0.97
2.23
2.46
2.48
2.43
2.58
2.61
2.46
3.087(2)
3.202(2)
3.022(2)
3.311(3)
3.537(3)
3.417(3)
3.311(3)
158
137
118
150
175
141
147
C(14)–H(14b)...O(2g)
Complex II
N(4g)–H(4g)...O(4)#2
N(3g)–H(3g)...O(2g)#3
N(3g)–H(3g)...O(2g)
N(5g)–H(1g5)...O(1)
N(5g)–H(2g5)...O(7)
0.86
0.86
0.86
0.95(1)
0.95(1)
2.07
2.16
2.41
2.20(2)
2.18(2)
2.905(4)
2.873(4)
2.967(4)
3.110(4)
3.092(4)
164
140
123
161(3)
161(3)
Complex III
N(3g)–H(1N3)...O(2g)#4
N(3g)–H(2N3)...O(2g)
N(3g)–H(2N3)...N(2g)#5
N(4g)–H(4g2)...O(1w)
O(1w)–H(1w)...O(10)
O(1w)–H(1w)...O(10a)
O(1w)–H(2w)...O(16)
O(1w)–H(2w)...O(16a)
0.86
0.86
0.86
2.01
2.38
2.59
2.854(5)
2.928(5)
3.077(5)
2.783(4)
2.842(4)
2.93(2)
166
122
117
0.86
1.94
166
1.12(5)
1.12(5)
1.08(6)
1.08(6)
1.76(5)
1.97(6)
1.89(6)
2.00(6)
161(4)
142(4)
173(5)
146(4)
2.959(5)
2.957(18)
Note. Symmetry operations: #1 −x+1/ 2, y+1/ 2, −z+3/ 2, #2 −x+2, −y+1, −z, #3 −x+1, −y, −z, #4 x, −y+2, z−1/ 2, #5 x,
−y+2, z+1/ 2.
Complex I. Figure 1 presents the structure of molecular complex I. The stoichiometry of the complex is 1:1. The
…
…
amino group of the guest forms two hydrogen bonds NH O with 18-crown-6 oxygens; the distances N(3g) O(4) =
…
3.087(2), N(3g) O(16) = 3.202(2) Å. The amino nitrogen of the guest is 1.797(2) Å away from the mean plane through
the heteroatoms of the macrocycle. The ethyl group of the guest interacts with the neighboring 18-crown-6 molecule related
…
to the basic molecule by the twofold screw axis. The short contacts are CH O(crown) with one hydrogen atom of the
464

Fig. 1. Structure of complex I with an atomic numbering scheme.
…
methyl group and one hydrogen atom of the methylene group; C(4g) O(1) (−x+1 / 2, y+1 / 2, −z+3 / 2) = 3.311(3),
…
C(5g) O(7) (−x+1 / 2, y+1 / 2, −z+3 / 2) = 3.537(3) Å. In related complexes, the crown ether–methyl group contacts are
…
C
O = 3.264(7)-3.801(7) Å in the complex with bis-methyl-10-camphorsulfonate [13a] and 3.287(3)-3.598(3) Å in the
…
complex with dimethylsulfoxide [13b]. All of the above-mentioned CH O distances do not exceed the upper limit adopted
in [4]. Thus host–guest interactions involve four of six oxygens of the 18-crown-6 molecule; in each pair [O(4) and O(16),
O(1) and O(7)], the oxygen atoms are separated by the oxyethylene fragment.
This arrangement of the complex with the sides of the crown ether molecule coordinating the guest molecule in
different ways is a rare occurrence in 18-crown-6 complexes, which was noted, e.g., in a 18-crown-6 complex with
6-chloro-7-sulfamido-3,4-dihydro-1,2,4-benzothiadiazine-1,1-dioxide [11]. The crown ether is most often centrosymmetric
in host–guest complexes, with two guest molecules coordinated to the two sides of the macrocycle in the same way [10].
Figure 2 shows a fragment of the –H–G1–H–G1– type polymer chain directed along the y axis in a crystal. Two
…
…
mild interactions, C(6) N(2g) = 3.417(3) and C(14) O(2g) = 3.311(3) Å, stabilize the chain along with the above
interactions. The dihedral angle between the planes through the oxygen atoms of the crown ether and the atoms forming
the five-membered heterocycle of the guest equals 57.35(8)°.
Complex II. Figure 3 presents the structure of the molecular complex II. Its stoichiometry is 1:2; the crown ether
molecule occupies a position around the inversion center at the point (1, 0.5, 0). The two guest molecules flanking the
cycle interact with the crown ether molecule in the same way. All hydrogen atoms of the hydrazine group participate in
…
these contacts. The primary amino group forms two hydrogen bonds NH O with the O(1) and O(7) atoms separated by
…
…
…
one oxyethylene fragment. The N O(crown) distances are N(5g) O(1) 3.110(4) and N(5g) O(7) 3.092(4) Å. The
…
…
secondary amino group forms an NH O hydrogen bond with the O(4) atom of the macrocycle; the distance N(4g) O(4)
(−x+2, −y+1, −z) = 2.905(4) Å. The same coordination of the hydrazide group was noted for the 18-crown-6 complex with
2,4-dinitrophenylhydrazine [14]. In both cases, the –G–H–G– arrangement is due to the participation of the neighboring
nitrogen molecules of the guest molecule in coordination to crown ether. Thus in II, all crown ether oxygens are involved
in the complex-forming hydrogen bonds. The amino nitrogen atom of the guest is 1.906(3) Å away from the plane through
465

Fug. 2. Fragment of a polymer chain in I.
Fig. 3. Structure of complex II with an atomic numbering scheme.
all crown ether oxygens. The dihedral angle between this plane and the plane through the atoms of the five-membered ring
of the guest is 46.99(9)°.
Figure 4 presents a fragment of the polymer chain –H–G2–G2–H– formed in the structure of II. The guest molecules
…
…
are linked into a centrosymmetric dimer by two N–H O=C hydrogen bonds with the distance N(3g) O(2g)
(−x+1, −y, −z) = 2.873(4) Å. The chain is of “head-to-head” type and develops along the [110] direction in the crystal.
Complex III. The structure of the molecular complex III is shown in Fig. 5. The crown ether:guest:water ratio in
the complex is 1:1:1. All molecules in the complex lie in the general positions. The crown ether molecule is disordered
over two positions with an occupancy of 83 and 17%, respectively. The two positions are related to each other by rotation
through an angle of 18.6° in the mean plane of the macrocycle. Further discussion concerns only the image of the major
component of the crown ether, since an analogous picture of interaction is also preserved for the image with minor occupation.
In contrast to I and II, this compound is a monohydrate, in which the water molecule interacts with two crown ether
…
…
…
oxygens; O(1w) O(10) 2.842(4) and O(1w) O(16) 2.959(5) Å. For the second position of the crown ether, O(1w) O(10a)
…
2.92(2) and O(1w) O(16a) 2.957(18) Å. The oxygen atom of the water molecule is 1.014(3) Å away from the plane
466

Fig. 4. Fragment of a polymer chain in II.
Fig. 5. Structure of complex III with an atomic numbering scheme.
…
through the heteroatoms of the macrocycle. Thus only two OH O hydrogen bonds stabilize the 18-crown-6–H O fragment.
2
…
The water molecule bridges the crown ether and the guest with which it interacts by means of the NH O(1w) hydrogen
…
bond, donating a lone electron pair for this purpose; the distance N(4g) O(1w) 2.783(4) Å. The bridging function of the
water molecule is also observed in some other complexes. e.g., in [18-crown-6 SiF 2H O] [15], [18-crown-6 (BF
4
2
3
2H O) 2H O] [16]. The arrangement of the 18-crown-6–water molecule associate is analogous to the arrangement found
2
2
2
in the 18-crown-6 H O complex with 3,4-diamino-1,2,5-oxadiazole [5], in which the water molecule also forms two
2
…
OH O(crown) hydrogen bonds with distances 2.924(4) and 2.878(4) Å, and the electron pair forms a hydrogen bond with
…
the amino group of the guest; the distance N O(w) = 2.905(9) Å.
A fragment of the structure of III is presented in Fig. 6. The middle of the ribbon is occupied by a chain of guest
…
molecules built according to the ‘‘dendritic parquet’’ motif. The guest molecules in the chain are linked by N–H O=C
…
…
and N–H N type hydrogen bonds; the parameters of these interactions are N(3g) O(2g) (x, −y+2, z−1 / 2) = 2.854(5) and
…
N(3g) N(2g) (x, −y+2, z+1 / 2) = 3.077(5) Å. A similar guest chain was previously fixed for the 18-crown-6 complex with
…
5-amino-1,2,4-triazole [7], where the guest molecules are connected by NH N hydrogen bonds.
Molecular geometries in complexes I, II, and III. In all the complexes, the 18-crown-6 molecule has approximately
D
symmetry. The gosh-torsion angles at the C–C bonds are 62.8(12)-71.5(2)°, and the trans-torsion angles at the C–O
3d
467

Fig. 6. Fragment of a ribbon in III.
…
bonds take the values 169.0(6)-179.9(5)°. The O O transannular distances are from 5.536(5) to 5.716(5) Å. The interatomic
distances and the bond angles in the 18-crown-6 molecule in the complexes have values typical in crown ethers.
In the planar five-membered heterocyclic ring of the guest molecules, the nonhydrogen atoms are coplanar to an
accuracy of 0.005 (G1), 0.001 (G2), 0.004 Å (G3). In all the three cases, the molecule has an intramolecular hydrogen
…
…
bond of NH O=C type (Figs. 1, 3, and 5); the N(3g) O(2g) distance is 3.022(2) (I), 2.967(4) (II), and 2.928(5) Å (III).
…
This is a bifurcate bond, since its hydrogen atom is simultaneously involved in an NH O type hydrogen bond with the
crown ether oxygen in I and III, whereas in II it is responsible for the formation of the dimer associate of the guest. The
…
intramolecular hydrogen bond closes the six-membered ring including the atoms
H(3N3)–N(3g)–C(2g)–C(3g)–C(1)–
…
O(2g) . This ring is also virtually planar, with deviations of its atoms from the mean plane 0.076 (I), 0.145 (II), 0.101 Å
(III). Therefore one can say that the heterocyclic framework of the guest involves the five- and six-membered rings fused
at the C(2g)–C(3g) bond to form a nearly planar system. The dihedral angle between the planes of the ring atoms is 3.37(2),
10.09(2), 6.61(3)° in G1-G3 molecules, respectively.
In compounds I-III, the small molecules are coordinated in different ways. The bilateral equivalent coordination
mode, often reported in the literature, is met in complex I; in III and II, we have one- and many-sided coordination,
respectively. In III, there are no direct host–guest contacts, although the guest has an easily coordinating amino group. The
interaction is mediated by the bridging water molecule, and the hydrogen bonds are formed by only two oxygen atoms of
the macrocycle. Examples I-III prove that host–guest complexes have diverse topologies depending on changes in the
geometry and the nature of the donor groups of the guest.
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