9-(Tri­chloro­acetyl­imino)­acridine monohydrate

The title compound, alternatively called N-acridin-9(10H)-yl­idene-2,2,2-tri­chloro­acet­amide mono­hydrate, C₁₅H₉Cl₃N₂O·H₂O, crystallizes in space group P2₁/c with Z = 4. The acridine moieties are arranged in layers, tilted at an angle of 15.20 (4)° relative to the ac plane, while adjacent mol­ecules pack in a head-to-tail manner. Acridine and water mol­ecules form columns along the b axis held in place by a network of hydrogen bonds, which is the major factor stabilizing the lattice. The acridine mol­ecule exhibits structural features of both the amino and imino forms, which could be due to the presence of the strong electronegative tri­chloro­acetyl substituent at the exocyclic N atom.

S1. Comment

Numerous experimental investigations and theoretical studies indicate that 9-aminoacridine can occur in two tautomeric forms, viz. amino or imino, in gaseous or liquid phases (Rak et al., 1997), although only the amino tautomer is present in the crystalline phase (Chaudhuri, 1983). Theory also predicts the co-existence of tautomeric forms in 9-aminoacridines monosubstituted at the exocyclic N atom (Rak et al., 1998). The structures of only two such derivatives have been determined, namely 9-(tert-butylamino)acridine (Meszko et al., 2002) and 9-(phenylamino)acridine (Leardini et al., 1998). It was found that crystals of these compounds are composed of molecules of the amino tautomer. The question thus arises as to which substituents at the exocyclic N atom could force the existence of 9-iminoacridines, particularly in the crystalline phase. The prospects of finding an N_exo-substituted 9-aminoacridine whose imino form is more stable than its amino form were indicated by Gurevich & Sheinker (1962), and are reinforced by the fact that we synthesized and determined the structure of 9-(methylimino)-10-methylacridine, i.e. a blocked derivative of 9-iminoacridine (Rak et al., 1998). 9-Aminoacridines, with a well recognized biological relevance, exhibit the ability to interact specifically with molecules in their nearest neighbourhood. The properties of these compounds are undoubtedly dependent on the form in which they occur (Barbe et al., 1996; Rak et al., 1997), and this was the reason for undertaking this study.

Crystals of the title compound, (I), contain molecules of the imino form (Fig. 1) and four of these occupy the unit cell (Fig. 2). The acridine moiety in (I) is nearly planar in the crystalline phase (Table 1), with atoms C9, N10 and H10 arranged almost linearly, and the C9—N16 bond deflected from the mean plane of the acridine nucleus by an angle of 7.8 (5)°. The dihedral angle between the mean plane of the acridine nucleus and the plane formed by atoms C9, N15 and C16, which can be regarded as a measure of the arrangement of the exocyclic imino substituent relative to the acridine moiety, is 61.5 (5)°. The N10—H10 bond is relatively short, which may be an attribute of 9-iminoacridines. The properties of the crystalline phase of (I) result from the network of hydrogen bonds (Fig. 2 and Table 2). Thus, the H atom attached to the endocyclic N atom is involved in a hydrogen bond with the O atom of a neighbouring water molecule, viz. N10—H10···O22. Furthermore, one of the H atoms of the water molecule participates in a hydrogen bond with the O atom of the trichloroacetyl group of an adjacent 9-iminoacridine molecule, i.e. O22—H22A···O17ⁱ [symmetry code: (i) 2 - x, 1 - y, 1 - z], and the second H atom interacts with one of three Cl atoms of another neighbouring 9-iminoacridine molecule, viz. O22—H22B···Cl21ⁱⁱ [symmetry code: (ii) 2 - x, -y, 1 - z].

The acridine moieties are arranged in layers tilted at an angle of 15.20 (4)° relative to the (010) plane, while neighbouring molecules pack in a head-to-tail manner. It can also be seen (Fig. 3) that the above-mentioned acridine fragments and water molecules form columns along the [010] direction, held in place by the network of multidirectional hydrogen bonds that are the principal factor stabilizing the lattice.

The title compound is the first known derivative of 9-aminoacridine substituted at the exocyclic N atom that contains molecules of the imino tautomeric form in the crystalline phase. It is thus interesting to compare its structural properties with those of other 9-amino- or 9-iminoacridines. Table 3 shows selected structural parameters for (I) and five other compounds, the structures of which were determined by X-ray analysis. The lengths of the C9—C11 and C9—N15 bonds in (I) are between those of four 9-aminoacridines and 9-(methylimino)-10-methylacridine. The angle N10···C9—N15 in (I) is typical of imino tautomers, i.e. it is similar to that in 9-(methylimino)-10-methylacridine. Finally, the acridine nucleus in (I) is almost planar, which is typical of amino but atypical of imino tautomers, e.g. in 9-(methylimino)-10-methylacridine, the central ring is substantially folded along the N10···C9 axis. The above analysis indicates that (I) exhibits structural features of both the amino and imino tautomers and that this may be caused by the presence of the strong electronegative trichloroacetyl substituent at the exocyclic N atom.

S2. Experimental

9-(Trichloroacetylimino)acridine, (I), was synthesized by adding an equimolar mixture of 9-aminoacridine and trimethylamine in dimethylformamide dropwise to a mixture of trichloroacetic acid in the same solvent (Gurevich & Sheinker, 1962). The product was purified chromatographically and yellow crystals of the monohydrate of the compound suitable for X-ray investigations were grown from ethanol.

S3. Refinement

The H10 atom (bonded to N10) and the H atoms belonging to the water molecule were refined isotropically. All H atoms attached to C atoms were placed geometrically and refined using a riding model, with U_iso(H) = 1.2U_eq(C) and with C—H distancs fixed at 0.96 Å.

Computing details

Data collection: KM-4 Software (Kuma, 1989); cell refinement: KM-4 Software; data reduction: KM-4 Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular structure of (I) showing the atom-labeling scheme and 50% probability displacement ellipsoids. H atoms are drown as small spheres of arbitrary radii. The N10—H10···O22 hydrogen bond is represented by a dashed line.
	Fig. 2. The arrangement of molecules of (I) in the unit cell, viewed along the c axis. Hydrogen bonds are represented by dashed lines.
	Fig. 3. A stereoview of the packing diagram of (I), viewed along the b axis. Hydrogen bonds (Table 2) are represented by dashed lines.

9-(Trichloroacetylimino)acridine monohydrate

Crystal data

C15H9Cl3N2O·H2O	F(000) = 728
Mr = 357.61	Dx = 1.598 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 50 reflections
a = 11.780 (2) Å	θ = 1.5–30°
b = 6.906 (1) Å	µ = 0.62 mm^−1
c = 18.823 (4) Å	T = 293 K
β = 103.88 (3)°	Prism, yellow
V = 1486.6 (5) Å^3	0.5 × 0.3 × 0.2 mm
Z = 4

Data collection

Kuma KM-4 diffractometer	Rint = 0.050
Radiation source: fine-focus sealed tube	θmax = 30.1°, θmin = 1.8°
Graphite monochromator	h = −16→16
θ/2θ scans	k = 0→9
4500 measured reflections	l = −26→0
4369 independent reflections	3 standard reflections every 200 reflections
1671 reflections with I > 2σ(I)	intensity decay: 3.9%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.051	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.194	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0854P)^2] where P = (Fo^2 + 2Fc^2)/3
4369 reflections	(Δ/σ)max < 0.001
210 parameters	Δρmax = 0.43 e Å^−3
0 restraints	Δρmin = −0.51 e Å^−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 > 2σ(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
C1	0.9963 (4)	0.1134 (8)	0.6936 (3)	0.0410 (11)
H1	0.9334	0.0935	0.7172	0.049*
C2	1.1099 (4)	0.0919 (8)	0.7328 (3)	0.0485 (12)
H2	1.1260	0.0590	0.7838	0.058*
C3	1.2007 (4)	0.1141 (8)	0.6974 (3)	0.0494 (13)
H3	1.2801	0.0965	0.7246	0.059*
C4	1.1797 (4)	0.1600 (7)	0.6257 (3)	0.0400 (11)
H4	1.2443	0.1789	0.6035	0.048*
C5	0.9163 (4)	0.3258 (6)	0.3984 (2)	0.0387 (11)
H5	0.9834	0.3394	0.3782	0.046*
C6	0.8092 (4)	0.3625 (7)	0.3570 (3)	0.0442 (11)
H6	0.7997	0.3978	0.3066	0.053*
C7	0.7109 (4)	0.3480 (8)	0.3867 (3)	0.0465 (12)
H7	0.6342	0.3732	0.3566	0.056*
C8	0.7234 (4)	0.2924 (7)	0.4580 (2)	0.0377 (10)
H8	0.6562	0.2837	0.4784	0.045*
C9	0.8536 (3)	0.1992 (6)	0.5775 (2)	0.0279 (8)
N10	1.0425 (3)	0.2382 (5)	0.5132 (2)	0.0330 (8)
C11	0.9703 (3)	0.1664 (6)	0.6190 (2)	0.0316 (9)
C12	1.0642 (3)	0.1883 (6)	0.5847 (2)	0.0329 (9)
C13	0.8357 (3)	0.2570 (6)	0.5033 (2)	0.0309 (9)
C14	0.9334 (3)	0.2743 (6)	0.4719 (2)	0.0291 (8)
N15	0.7642 (3)	0.1530 (6)	0.6080 (2)	0.0348 (8)
C16	0.6839 (3)	0.2736 (6)	0.6171 (2)	0.0289 (8)
O17	0.6810 (3)	0.4516 (5)	0.6152 (2)	0.0490 (9)
C18	0.5741 (3)	0.1755 (6)	0.6333 (2)	0.0307 (9)
Cl19	0.53508 (10)	0.2900 (2)	0.70786 (6)	0.0480 (3)
Cl20	0.45841 (9)	0.2077 (2)	0.55447 (6)	0.0522 (4)
Cl21	0.59035 (12)	−0.07416 (19)	0.65156 (8)	0.0555 (4)
O22	1.2115 (3)	0.2560 (6)	0.4373 (2)	0.0517 (10)
H22A	1.243 (5)	0.340 (9)	0.417 (3)	0.062*
H22B	1.227 (5)	0.153 (10)	0.419 (3)	0.062*
H10	1.092 (5)	0.252 (9)	0.496 (3)	0.062*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.039 (2)	0.047 (3)	0.040 (2)	0.003 (2)	0.0147 (19)	0.003 (2)
C2	0.048 (3)	0.054 (3)	0.042 (3)	0.005 (3)	0.007 (2)	−0.002 (2)
C3	0.034 (2)	0.045 (3)	0.064 (3)	0.001 (2)	−0.001 (2)	−0.005 (3)
C4	0.0288 (19)	0.032 (3)	0.061 (3)	−0.0009 (19)	0.016 (2)	−0.003 (2)
C5	0.056 (3)	0.026 (2)	0.041 (2)	−0.004 (2)	0.027 (2)	−0.0001 (19)
C6	0.063 (3)	0.037 (3)	0.033 (2)	0.000 (2)	0.013 (2)	0.002 (2)
C7	0.045 (2)	0.051 (3)	0.042 (2)	0.006 (2)	0.005 (2)	0.001 (2)
C8	0.035 (2)	0.044 (3)	0.035 (2)	−0.001 (2)	0.0097 (17)	0.000 (2)
C9	0.0286 (18)	0.0211 (19)	0.036 (2)	−0.0015 (16)	0.0114 (16)	−0.0001 (18)
N10	0.0341 (17)	0.0247 (18)	0.048 (2)	−0.0033 (15)	0.0254 (16)	0.0002 (16)
C11	0.0299 (19)	0.028 (2)	0.040 (2)	−0.0007 (17)	0.0140 (17)	−0.0026 (19)
C12	0.0303 (18)	0.025 (2)	0.047 (2)	−0.0051 (17)	0.0176 (17)	−0.007 (2)
C13	0.0318 (18)	0.025 (2)	0.041 (2)	−0.0008 (17)	0.0178 (16)	−0.0008 (18)
C14	0.035 (2)	0.0192 (19)	0.038 (2)	−0.0012 (17)	0.0172 (17)	−0.0020 (18)
N15	0.0287 (16)	0.035 (2)	0.045 (2)	0.0008 (15)	0.0177 (15)	0.0060 (17)
C16	0.0268 (17)	0.032 (2)	0.0300 (19)	−0.0029 (17)	0.0106 (14)	−0.0011 (18)
O17	0.063 (2)	0.0289 (17)	0.065 (2)	−0.0045 (16)	0.0343 (19)	0.0010 (17)
C18	0.0295 (18)	0.037 (2)	0.0277 (18)	0.0005 (18)	0.0112 (15)	0.0014 (18)
Cl19	0.0487 (6)	0.0630 (8)	0.0387 (6)	0.0009 (6)	0.0232 (5)	−0.0076 (6)
Cl20	0.0346 (5)	0.0785 (10)	0.0415 (6)	−0.0029 (6)	0.0052 (4)	−0.0031 (7)
Cl21	0.0559 (7)	0.0395 (7)	0.0837 (10)	−0.0028 (6)	0.0414 (7)	0.0132 (7)
O22	0.056 (2)	0.0358 (19)	0.079 (3)	−0.0086 (17)	0.0476 (19)	−0.0051 (19)

Geometric parameters (Å, º)

C1—C2	1.373 (7)	N10—C12	1.352 (6)
C1—C11	1.413 (6)	N10—C14	1.357 (5)
C2—C3	1.398 (7)	N10—H10	0.74 (6)
C3—C4	1.350 (7)	C11—C12	1.416 (5)
C4—C12	1.407 (6)	C13—C14	1.420 (5)
C5—C6	1.339 (7)	N15—C16	1.301 (5)
C5—C14	1.395 (6)	C16—O17	1.230 (5)
C6—C7	1.405 (7)	C16—C18	1.554 (5)
C7—C8	1.370 (6)	C18—Cl21	1.759 (5)
C8—C13	1.412 (6)	C18—Cl19	1.765 (4)
C9—C11	1.427 (5)	C18—Cl20	1.772 (4)
C9—C13	1.419 (6)	O22—H22A	0.82 (6)
C9—N15	1.354 (5)	O22—H22B	0.82 (5)
C2—C1—C11	120.9 (4)	N10—C14—C5	120.5 (4)
C1—C2—C3	119.4 (5)	N10—C14—C13	119.8 (4)
C4—C3—C2	121.7 (4)	C5—C14—C13	119.7 (4)
C3—C4—C12	120.1 (4)	C9—N15—C16	124.6 (4)
C6—C5—C14	121.1 (4)	O17—C16—N15	130.7 (4)
C5—C6—C7	120.5 (4)	C11—C9—C13	118.7 (3)
C8—C7—C6	120.3 (4)	C11—C9—N15	118.4 (4)
C7—C8—C13	120.3 (4)	C12—N10—H10	119 (4)
N15—C9—C13	122.5 (4)	C12—N10—C14	123.0 (3)
C1—C11—C12	118.3 (4)	O17—C16—C18	115.0 (3)
C1—C11—C9	122.4 (4)	N15—C16—C18	114.3 (4)
C12—C11—C9	119.3 (4)	C16—C18—Cl21	114.1 (3)
N10—C12—C4	120.5 (4)	C16—C18—Cl19	110.4 (3)
N10—C12—C11	119.9 (4)	Cl21—C18—Cl19	108.7 (2)
C4—C12—C11	119.6 (4)	C16—C18—Cl20	106.9 (3)
C8—C13—C9	122.6 (4)	Cl21—C18—Cl20	108.2 (2)
C8—C13—C14	118.1 (4)	Cl19—C18—Cl20	108.3 (2)
C9—C13—C14	119.3 (4)
C9—N15—C16—O17	−16.1 (8)	C9—C11—C12—N10	−0.5 (6)
C11—C9—C13—C14	2.1 (6)	C1—C11—C12—C4	−1.0 (6)
C11—C9—N15—C16	123.0 (5)	C9—C11—C12—C4	178.7 (4)
C11—C12—N10—H10	178 (5)	C7—C8—C13—C9	180.0 (5)
C12—N10—C14—C13	−1.1 (6)	C7—C8—C13—C14	−2.2 (7)
C11—C1—C2—C3	−3.0 (8)	N15—C9—C13—C8	7.5 (7)
C9—N15—C16—C18	164.2 (4)	C11—C9—C13—C8	179.9 (4)
C1—C2—C3—C4	1.3 (8)	N15—C9—C13—C14	−170.3 (4)
C2—C3—C4—C12	0.5 (8)	C12—N10—C14—C5	179.8 (4)
C14—C5—C6—C7	−0.6 (7)	C6—C5—C14—N10	−179.8 (4)
C5—C6—C7—C8	−1.3 (8)	C6—C5—C14—C13	1.1 (7)
C6—C7—C8—C13	2.7 (8)	C8—C13—C14—N10	−178.9 (4)
C2—C1—C11—C12	2.8 (7)	C9—C13—C14—N10	−0.9 (6)
C2—C1—C11—C9	−176.9 (5)	C8—C13—C14—C5	0.2 (6)
N15—C9—C11—C1	−8.9 (6)	C9—C13—C14—C5	178.2 (4)
C13—C9—C11—C1	178.3 (4)	C13—C9—N15—C16	−64.6 (6)
N15—C9—C11—C12	171.4 (4)	O17—C16—C18—Cl21	−169.4 (3)
C13—C9—C11—C12	−1.4 (6)	N15—C16—C18—Cl21	10.3 (5)
C14—N10—C12—C4	−177.5 (4)	O17—C16—C18—Cl19	−46.6 (5)
C14—N10—C12—C11	1.8 (6)	N15—C16—C18—Cl19	133.1 (3)
C3—C4—C12—N10	178.6 (4)	O17—C16—C18—Cl20	71.0 (4)
C3—C4—C12—C11	−0.6 (7)	N15—C16—C18—Cl20	−109.3 (4)
C1—C11—C12—N10	179.8 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N10—H10···O22	0.74 (6)	1.99 (5)	2.717 (5)	170 (7)
O22—H22A···O17^i	0.82 (6)	1.87 (6)	2.694 (5)	170.8 (6)
O22—H22B···Cl21^ii	0.82 (5)	2.84 (5)	3.420 (4)	128.4 (7)

Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) −x+2, −y, −z+1.