2,7-Dioxa-15,19-di­aza­tri­cyclo­[19,4,0,0^8,13]­pentacosa-8,10,12,21,23,25(1)-hexaene

The title mol­ecule, C₂₁H₂₄N₂O₂, is a macrocyclic multidentate Schiff base ligand containing two imine N and two ether O atoms which has a crystallographic twofold axis. The macro­cyclic inner-hole size, estimated as twice the mean distance of the donor atoms from their centroid, is approximately 2.08 Å.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.036
• wR factor = 0.106
• Data-to-parameter ratio = 14.3

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

Over the last two decades, macrocyclic multidentate Schiff base N_xO_y (where x = 2,3 and y = 2,3) donor-type ligands have been investigated as potential metal-ion-selective ionophores (Lindoy et al., 1993; Esteban et al., 2000). In particular, macrocycles have been widely studied as complexation agents for alkaline, alkaline-earth and transition-metal ion (especially lanthanides) recognition with particular metal-ion binding applications (e.g. selective extraction of heavy and precious metals) are of great interest in environmental, inorganic and coordination chemistry (Lindoy, 1997; Hayvalı et al., 1999; Vicente et al., 2000). Some Schiff base complexes have also been used in catalytic reduction reactions (Tafesh & Weiguny, 1996). In addition, a series of investigations have also involved the synthetic, thermodynamic and structural properties of selective complex formation of a number of transition metal ions (Fenton et al., 1987; Adam et al., 1994a). In literature, there are only a very limited number of reports about the structures of the free macrocyclic multidentate N₂O₂ and N₂O₃ donor-type ligands (Chia et al., 1991; Hökelek et al., 1999a,b; Hökelek, Akduran, Kaya & Kılıç, 2000). In 1994, Adam and co-workers synthesized the reduction product (the multidentate diamine, N₂O₂) from the reaction of 1,4-bis(salicyloxy)butane, 1,3-diaminopropane and sodium borohydride, without isolating the title compound (Adam et al., 1994b). The title compound, (I), may be a potential metal-ion selective reagent for lanthanides, alkaline and alkaline-earth metal ions. The structure determination of (I) was carried out in order to estimate the relative macrocyclic ring hole size and to understand the effects of the macrocyclic ring on the C═N imine bond and C—N═C bond angle.

As shown in Fig. 1, molecule (I) has a crystallographic twofold axis. The intramolecular C1···C11 [7.219 (3) Å], N1···N1ⁱ [3.978 (2) Å], O1···O1ⁱ [3.894 (3) Å] and N1···O1ⁱ [5.580 (3) Å] distances may indicate the hole size of the ligand cavity [symmetry code: (i) -x, y, 1/2 - z]. The C1···C11 distance is larger than the N···N distance in the potassium complex of substituted diaza-18-crown-6 (6.253 Å; Gandour et al., 1986). The relative macrocyclic inner hole size, estimated as twice the mean distance of the donor atoms from their centroid is approximately 2.08 Å, using the `modified covalent radii' of the Nsp² (0.66 Å) and Osp³ (0.76 Å) atoms as in the literature method (Goodwin et al., 1982; Adam et al., 1983; Drummond et al., 1982). The inner hole size of (I) (2.08 Å), which is a 17-membered macro-ring, can be compared with the 16- (1.57 Å) and 19-membered (2.53 Å) multidentate ligand hole sizes (Hökelek, Akduran, Kaya & Kılıç, 2000).

The C═N imine bond length [1.2607 (14) Å] and C—N═C imine bond angle [117.71 (10)°] are smaller than the corresponding values in salicylaldimine and naphthaldimine Schiff base ligands (Yıldız et al., 1998; Hökelek et al., 2001). In naphthaldimine and salicylaldimine Schiff bases, intramolecular hydrogen bonding is observed, which causes a lengthening of the C═N imine bond and an increase in the C—N═C bond angle (Yıldız et al., 1998; Hökelek, Kılıç, Işıklan & Toy, 2000). C═N imine bond lengthening is also observed in the Schiff base complexes (Fernández-G et al., 1986; Calligaris et al., 1972).

S2. Experimental

1,4-Bis(salicyloxy)butane (m.p. 374 K) was prepared from the reaction of salicylaldehyde (12.2 g, 100 mmol), sodium hydroxide (6.0 g, 150 mmol) and 1,4-dibromobutane (15.3 g, 71 mmol) in boiling ethanol (150 ml). Compound (I) was obtained from the reaction of 1,4-bis(salicyloxy)butane (0.50 g, 1.67 mmol) in ethanol (100 ml) and 1,3-diaminopropane (0.21 ml, 2.45 mmol) in ethanol (50 ml) with argon passing over the reaction mixture and it was refluxed for 5 h. The solvent was evaporated and the residue was crystallized from ethyl acetate [yield 0.31 g (62%), m.p. 440 K].

S3. Refinement

The H atoms were positioned geometrically with C—H distances of 0.96 and 0.93 Å for CH₃ and CH, respectively, and a riding model was used during the refinement.

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: CAD-4 Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976).

Figures

Fig. 1. An ORTEPII (Johnson, 1976) drawing of the title molecule with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.

(I)

Crystal data

C21H24N2O2	F(000) = 724
Mr = 336.43	Dx = 1.255 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 14.231 (8) Å	Cell parameters from 25 reflections
b = 15.6630 (14) Å	θ = 10–18°
c = 8.206 (4) Å	µ = 0.08 mm^−1
β = 103.044 (8)°	T = 293 K
V = 1781.9 (13) Å^3	Block-like, colourless
Z = 4	0.30 × 0.25 × 0.20 mm

Data collection

Enraf-Nonius CAD-4 diffractometer	1468 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.034
Graphite monochromator	θmax = 26.3°, θmin = 2.6°
ω/2θ scans	h = −17→17
Absorption correction: ψ scans (MolEN; Fair, 1990)	k = −19→19
Tmin = 0.975, Tmax = 0.984	l = −10→0
3554 measured reflections	3 standard reflections every 120 min
1816 independent reflections	intensity decay: 1%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.036	Only H-atom displacement parameters refined
wR(F^2) = 0.106	w = 1/[σ^2(Fo^2) + (0.0488P)^2 + 0.3494P] where P = (Fo^2 + 2Fc^2)/3
S = 1.06	(Δ/σ)max < 0.001
1816 reflections	Δρmax = 0.14 e Å^−3
127 parameters	Δρmin = −0.15 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.063 (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
O1	0.13740 (5)	0.49049 (5)	0.25488 (12)	0.0515 (3)
N1	0.14349 (6)	0.23658 (6)	0.30725 (12)	0.0448 (3)
C9	0.21554 (7)	0.45222 (7)	0.21602 (14)	0.0417 (3)
C4	0.21878 (7)	0.36282 (7)	0.23047 (13)	0.0392 (3)
C3	0.14552 (7)	0.31686 (7)	0.29760 (13)	0.0396 (3)
H31	0.0989	0.3483	0.3344	0.054 (4)*
C7	0.36222 (9)	0.45047 (8)	0.11910 (17)	0.0551 (3)
H71	0.4107	0.4797	0.0830	0.069 (4)*
C10	0.13676 (8)	0.58169 (7)	0.27145 (15)	0.0448 (3)
H101	0.1388	0.6089	0.1661	0.053 (4)*
H102	0.1920	0.6006	0.3559	0.048 (3)*
C5	0.29414 (8)	0.31938 (8)	0.18443 (15)	0.0458 (3)
H51	0.2966	0.2601	0.1916	0.054 (4)*
C2	0.06875 (8)	0.19826 (7)	0.37952 (14)	0.0441 (3)
H21	0.0331	0.2429	0.4210	0.048 (3)*
H22	0.0985	0.1622	0.4732	0.049 (3)*
C6	0.36528 (9)	0.36251 (8)	0.12842 (16)	0.0540 (3)
H61	0.4149	0.3326	0.0972	0.070 (4)*
C11	0.04434 (8)	0.60372 (7)	0.32230 (15)	0.0461 (3)
H111	0.0510	0.6598	0.3738	0.056 (4)*
H112	0.0343	0.5630	0.4058	0.055 (4)*
C1	0.0000	0.14535 (9)	0.2500	0.0410 (4)
H11	−0.0374	0.1088	0.3069	0.045 (3)*
C8	0.28829 (8)	0.49578 (8)	0.16253 (16)	0.0509 (3)
H81	0.2872	0.5551	0.1561	0.055 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0404 (5)	0.0348 (4)	0.0850 (6)	−0.0048 (3)	0.0262 (4)	−0.0088 (4)
N1	0.0400 (5)	0.0412 (5)	0.0545 (6)	−0.0019 (4)	0.0135 (4)	−0.0035 (4)
C9	0.0349 (5)	0.0429 (6)	0.0481 (6)	−0.0053 (4)	0.0109 (4)	−0.0107 (4)
C4	0.0339 (5)	0.0423 (6)	0.0405 (5)	−0.0039 (4)	0.0066 (4)	−0.0076 (4)
C3	0.0357 (5)	0.0418 (6)	0.0410 (6)	−0.0008 (4)	0.0080 (4)	−0.0072 (4)
C7	0.0430 (6)	0.0617 (8)	0.0663 (8)	−0.0136 (6)	0.0242 (6)	−0.0126 (6)
C10	0.0433 (6)	0.0344 (6)	0.0572 (7)	−0.0046 (5)	0.0127 (5)	−0.0034 (5)
C5	0.0424 (6)	0.0448 (6)	0.0510 (7)	0.0015 (5)	0.0119 (5)	−0.0069 (5)
C2	0.0457 (6)	0.0434 (6)	0.0448 (6)	0.0000 (5)	0.0139 (5)	0.0021 (5)
C6	0.0417 (6)	0.0614 (8)	0.0630 (7)	0.0008 (5)	0.0207 (5)	−0.0139 (6)
C11	0.0474 (7)	0.0390 (6)	0.0529 (7)	−0.0001 (5)	0.0135 (5)	−0.0068 (5)
C1	0.0439 (8)	0.0316 (7)	0.0511 (9)	0.000	0.0180 (7)	0.000
C8	0.0450 (7)	0.0456 (7)	0.0650 (8)	−0.0124 (5)	0.0184 (6)	−0.0109 (5)

Geometric parameters (Å, º)

O1—C9	1.3629 (14)	C10—H102	0.9700
O1—C10	1.4350 (13)	C5—C6	1.3793 (17)
N1—C3	1.2607 (14)	C5—H51	0.9300
N1—C2	1.4587 (15)	C2—C1	1.5181 (14)
C9—C8	1.3912 (16)	C2—H21	0.9700
C9—C4	1.4052 (16)	C2—H22	0.9700
C4—C5	1.3924 (16)	C6—H61	0.9300
C4—C3	1.4724 (16)	C11—C11^i	1.525 (2)
C3—H31	0.9300	C11—H111	0.9700
C7—C6	1.3799 (19)	C11—H112	0.9700
C7—C8	1.3808 (17)	C1—C2^i	1.5181 (14)
C7—H71	0.9300	C1—H11	0.9700
C10—C11	1.5069 (18)	C8—H81	0.9300
C10—H101	0.9700
C9—O1—C10	118.88 (8)	C4—C5—H51	119.4
C3—N1—C2	117.71 (10)	N1—C2—C1	110.72 (9)
O1—C9—C8	124.24 (11)	N1—C2—H21	109.5
O1—C9—C4	115.57 (9)	C1—C2—H21	109.5
C8—C9—C4	120.18 (10)	N1—C2—H22	109.5
C5—C4—C9	118.47 (10)	C1—C2—H22	109.5
C5—C4—C3	121.09 (10)	H21—C2—H22	108.1
C9—C4—C3	120.41 (9)	C5—C6—C7	119.42 (11)
N1—C3—C4	122.64 (10)	C5—C6—H61	120.3
N1—C3—H31	118.7	C7—C6—H61	120.3
C4—C3—H31	118.7	C10—C11—C11^i	113.92 (12)
C6—C7—C8	121.01 (11)	C10—C11—H111	108.8
C6—C7—H71	119.5	C11^i—C11—H111	108.8
C8—C7—H71	119.5	C10—C11—H112	108.8
O1—C10—C11	106.19 (9)	C11^i—C11—H112	108.8
O1—C10—H101	110.5	H111—C11—H112	107.7
C11—C10—H101	110.5	C2—C1—C2^i	113.81 (13)
O1—C10—H102	110.5	C2—C1—H11	108.8
C11—C10—H102	110.5	C2^i—C1—H11	108.8
H101—C10—H102	108.7	C7—C8—C9	119.61 (12)
C6—C5—C4	121.28 (11)	C7—C8—H81	120.2
C6—C5—H51	119.4	C9—C8—H81	120.2
C10—O1—C9—C8	−11.67 (16)	C3—C4—C5—C6	−177.12 (10)
C10—O1—C9—C4	169.33 (10)	C3—N1—C2—C1	115.50 (11)
O1—C9—C4—C5	176.77 (10)	C4—C5—C6—C7	0.55 (18)
C8—C9—C4—C5	−2.28 (15)	C8—C7—C6—C5	−1.0 (2)
O1—C9—C4—C3	−5.03 (14)	O1—C10—C11—C11^i	−79.17 (9)
C8—C9—C4—C3	175.92 (10)	N1—C2—C1—C2^i	−73.83 (8)
C2—N1—C3—C4	178.64 (9)	C6—C7—C8—C9	−0.21 (19)
C5—C4—C3—N1	−4.47 (16)	O1—C9—C8—C7	−177.09 (11)
C9—C4—C3—N1	177.37 (10)	C4—C9—C8—C7	1.87 (17)
C9—O1—C10—C11	−177.35 (9)	C10—C11—C11^i—C10^i	151.00 (10)
C9—C4—C5—C6	1.07 (16)

Symmetry code: (i) −x, y, −z+1/2.