Isomorphism in 1-(2-halidobenzyl)-4-[(E)-2-(3-hydroxy­phenyl)­ethenyl]­pyridin­ium halide hemihydrates (halide = Cl, Br)

The crystal structures of two (E)-stilbazolium salts, namely 1-(2-chloro­benzyl)-4-[(E)-2-(3-hydroxy­phenyl)­ethenyl]pyridinium chloride hemihydrate, C₂₀H₁₇ClNO⁺·Cl^-·0.5H₂O, (I), and 1-(2-bromo­benzyl)-4-[(E)-2-(3-hydroxy­phenyl)­ethen­yl]­pyridinium bromide hemihydrate, C₂₀H₁₇BrNO⁺·Br^-·0.5H₂O, (II), are isomorphous; the isostructurality index is 99.3%. In both salts, the aza­styryl fragments are almost planar, while the rings of the benzyl groups are almost perpendicular to the aza­styryl planes. The building blocks of the structures are twofold symmetric hydrogen-bonded systems of two cations, two halide anions and one water mol­ecule, which lies on a twofold axis. In the crystal structure, these blocks are connected by means of weaker inter­actions, viz. van der Waals, weak hydrogen bonding and stacking. This study illustrates the robustness of certain supramolecular motifs created by a spectrum of intermolecular interactions in generating these isomorphous crystal structures.

S1. Comment

The salts of the derivatives of (E)-stilbazolium have been found to be useful for nonlinear optics [for instance, trans-4'-(dimethylamino)-N-methyl-4-stilbazolium p-toluenesulfonate, DAST (Marder et al., 1989, 1994)] or for the preparation of polymers (e.g. Bloch & Wright, 1989). Due to an almost planar conformation, similar to (E)-stilbene, and the conjugated double-bond system, some stilbazolium derivatives exhibit interesting photochemical properties (e.g. Usami et al., 1990). The maximum in the UV absorption spectrum, shifted to long wavelength due to the conjugated double-bond system, can be used in the testing of chromatographic stationary phases (Prukała et al., 2008). N-alkyl- or N-benzyl-substituted (E)-stilbazole derivatives show a broad spectrum of antimicrobial activity (e.g. Wyrzykiewicz et al., 1990; Prukała & Kędzia, 1999) and some of them have already been patented (e.g. MacDonald et al., 2007; Klein et al., 2007).

We decided to undertake a detailed structural study of the family of N-benzyl-stilbazole derivatives. Here, we report the crystal structures of two compounds, 1-(2-chlorobenzyl)-4-[(E)-2-(3-hydroxyphenyl)ethenyl]pyridinium chloride hemihydrate, (I), and 1-(2-bromobenzyl)-4-[(E)-2-(3-hydroxyphenyl)ethenyl]pyridinium bromide hemihydrate, (II).

Compounds (I) and (II) are isomorphous; they crystallize in the same space group, and the unit-cell dimensions and packing modes are similar (Fig. 1a and b). In order to gain some insight into the degree of isomorphism, we have used the descriptors introduced by Kálmán et al. (1991). The unit-cell similarity index, Π, defined as the difference between unity and the ratio of the sums of the orthogonalized unit-cell parameters, is almost ideal, at 0.01. The isostructurality index, which shows how close the positions of the atoms in the unit cells are, is defined by the sum of the differences between the positions of analogous atoms. In the case of (I) and (II), the value of this index is also close to the ideal value at 99.3%. Kubicki & Szafrański (1998) proposed a modification of this latter parameter, which takes the point group symmetry into account and gives a more absolute measure of the degree of isostructurality; it should be 1 for ideally isomorphous compounds and 0 for randomly distributed atoms. The value of this modified index for (I) and (II) is 0.96. The structures of the two molecules are so similar (Figs. 2, 3) that even normal probability plots (International Tables for X-ray Crystallography, 1974; Abrahams & Keve, 1971) for bond lengths (without C—X bonds) and all bond angles show no differences of a systematic nature. The correlation factors R² are 0.982 and 0.975 for the bond lengths and angles, respectively.

The conformation of each molecule can be described using the dihedral angles between the planar fragments, namely the three rings (chlorophenyl A, pyridine B and hydroxyphenyl C) and the C11—C14═C15—C16 bridge (D). The dihedral angles within the whole azastyryl fragments are small, while those between rings B and C are as low as 2.75 (12)° in (I) and 2.66 (17)° in (II). The plane of the ethenyl bridge is significantly more twisted with respect to the ring planes (the angles are around 6°). It might be noted that these twists have the same sense, so the rings are almost coplanar. The perfectly planar benzyl groups are almost perpendicular to the azastyryl moieties; the dihedral angles between rings A and B are as high as 76.57 (6)° for (I) and 75.84 (9)° for (II). These are close to typical values: in the Cambridge Structural Database (Version 5.29 of November 2007; Allen, 2002) there are 778 similar fragments (both pyridyl- and phenyl-benzyl) and the values of the dihedral angles between the rings are in the range 53–90° with a mean value of 77.7 (3)°.

The building blocks of the structures are symmetrical hydrogen-bonded fragments built of two cations, two halide anions and a water molecule which occupies a special position on a twofold axis (Table 1, Fig. 4). All strong hydrogen-bond donors are involved in the creation of these structures, so the further construction of the crystal structures utilizes weaker interactions. The blocks are connected into a three-dimensional structure by means of relatively strong C—H···O and C—H···X hydrogen bonds (see Table 1 and Fig. 1). Additionally, an interesting network of weak interactions involving π-electron systems is created (Fig. 5). The distances between the centroids of rings B and C from molecules related by the centre of symmetry (1 - x,1 - y,1 - z) are 3.540 (2) Å in (I) and 3.676 (2) Å in (II). The planes of the rings are almost parallel (dihedral angles of ca 2.8°); taking the offset into account the distances between the planes are ca 3.38 Å in both cases. These centrosymmetric dimers are connected to neighbouring ones, related by another centre of symmetry, by means of weak but directional C—H···π interactions with the C14═C15 double bond (Table 1).

S2. Experimental

The general procedure for the synthesis of (I) and (II) is as follows. (E)-Azastilbenol-2' (5 mmol) was dissolved in boiling nitromethane (50 ml). Upon dissolution, the corresponding benzyl halide (25 mmol) was added. The reaction mixture was refluxed for 5 h and the precipitated solid was filtered off. Then, half the volume of nitromethane was removed from the filtrate using a rotary evaporator. The residue was cooled for 24 h and the precipitated solid was filtered off, washed with CH₃NO₂ and dried. The desired products were obtained by combining both fractions of solids and recrystallizing them from methanol. For (I), m.p. 470–473 K; for (II), m.p. 498–501 K. Spectroscopic data are in the archived CIF.

S3. Refinement

The choice of the non-standard space group I2/a (instead of C2/c) was as a result of the large values of the β angle [131.44° for (I) and 130.70° for (II)] in the latter case. The positions of the hydroxyl H atom in (I) and the unique water H atom in (II) were refined with a restrained O—H distance of 0.84 (1) Å. The positions and U_iso(H) of all other H atoms in (I) were refined freely, while in (II) they were placed in idealized positions and refined using a riding model, with C—H = 0.93–0.97 Å [Please check added text]. All H atoms in (II) were assigned U_iso(H) = 1.2U_eq(C).

Computing details

For both compounds, data collection: CrysAlis CCD (Oxford Diffraction, 2007); cell refinement: CrysAlis RED (Oxford Diffraction, 2007); data reduction: CrysAlis RED (Oxford Diffraction, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP (Siemens, 1989); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The crystal packing of (a) (I) and (b) (II), viewed along the a direction.
	Fig. 2. The molecule of (I), with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Hydrogen bonds are drawn as dashed lines.
	Fig. 3. The molecule of (II), with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Hydrogen bonds are drawn as dashed lines.
	Fig. 4. The building block of the crystal structures, shown for (I). Hydrogen bonds are drawn as dashed lines. [Symmetry codes: (i) -1/2 + x, 1/2 + y, 1/2 + z; (ii) 1/2 - x, y,2 - z.]
	Fig. 5. The molecules of (I), connected by weak interactions that involve π electrons (see text for details). The interactions and hydrogen bonds are drawn as dashed lines. [Symmetry codes: (i) x, y, z; (ii) 1 - x, 1 - y, 1 - z; (iii) 3/2 - x, 3/2 - y, 1/2 - z; (iv) -1/2 + x, -1/2 + y, 1/2 + z.]

(I) 1-(2-chlorobenzyl)-4-[(E)-2-(3-hydroxyphenyl)ethenyl]pyridinium chloride hemihydrate

Crystal data

C20H17ClNO^+·Cl^−·0.5H2O	F(000) = 1528
Mr = 367.25	Dx = 1.366 Mg m^−3
Monoclinic, I2/a	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -I 2ya	Cell parameters from 4084 reflections
a = 15.6100 (12) Å	θ = 3–24°
b = 13.2847 (10) Å	µ = 0.37 mm^−1
c = 17.2233 (13) Å	T = 295 K
β = 91.358 (6)°	Block, colourless
V = 3570.7 (5) Å^3	0.3 × 0.2 × 0.2 mm
Z = 8

Data collection

Kuma KM4 CCD area-detector diffractometer	3288 independent reflections
Radiation source: fine-focus sealed tube	2229 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.017
ω scans	θmax = 25.5°, θmin = 2.4°
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2007)	h = −18→18
Tmin = 0.903, Tmax = 0.928	k = −16→16
10549 measured reflections	l = −20→17

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)] = 0.036	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.104	H atoms treated by a mixture of independent and constrained refinement
S = 1.21	w = 1/[σ^2(Fo^2) + (0.05P)^2] where P = (Fo^2 + 2Fc^2)/3
3288 reflections	(Δ/σ)max = 0.001
294 parameters	Δρmax = 0.22 e Å^−3
1 restraint	Δρmin = −0.27 e Å^−3

Special details

Experimental. Spectroscopic data: (I) IR (KBr, cm^-1): 3030.0, 2990.5, 2940.4, 1620.8, 1575.1, 1510.5, 1460.6, 1265.7, 1160.5, 1055.2,990.0, 935.9, 870.1, 748.6. ¹H NMR (DMSO-d₆): δ = 9.81 (s, 1H, -OH), 9.06 (d, J = 6.8 Hz, 2H, o-H in –⁺NC₅H₄), 8.34 (d, J = 6.8 Hz, 2H, m-H in –⁺NC₅H₄), 8.03 (d, J = 16.2 Hz, 1H, –⁺NC₅H₄-CH═), 7.69–7.22 (m, 7H), 7.21 (s, 1H, o-H in phenyl ring), 6.95 (d, J = 7.5 Hz, 1H, p-H in phenyl ring), 5.99 (s, 2H, -CH₂-N⁺). ¹³C NMR (DMSO-d₆): δ = 157.8, 153.5, 144.5, 141.7, 136.1, 132.9, 131.7, 131.1, 129.9, 129.7, 128.0, 123.9,122.9, 119.0, 117.8, 114.6, 60.0. m.p. 470–473 K.

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
O1W	0.7500	0.3423 (2)	0.5000	0.0880 (8)
H1WA	0.716 (2)	0.300 (3)	0.531 (2)	0.160 (14)*
C1	0.78397 (12)	0.62420 (14)	0.10035 (10)	0.0491 (5)
Cl1	0.71821 (4)	0.72679 (4)	0.11712 (4)	0.0811 (2)
C2	0.86727 (13)	0.64177 (17)	0.07922 (11)	0.0561 (5)
H2	0.8844 (12)	0.7080 (16)	0.0739 (11)	0.055 (5)*
C3	0.92080 (15)	0.56250 (18)	0.06680 (12)	0.0615 (6)
H3	0.9804 (13)	0.5769 (15)	0.0515 (11)	0.061 (6)*
C4	0.89226 (15)	0.46597 (19)	0.07464 (13)	0.0657 (6)
H4	0.9292 (13)	0.4077 (16)	0.0669 (12)	0.070 (6)*
C5	0.80819 (14)	0.44776 (16)	0.09495 (12)	0.0564 (5)
H5	0.7890 (13)	0.3781 (16)	0.1002 (11)	0.069 (6)*
C6	0.75284 (12)	0.52680 (14)	0.10841 (10)	0.0459 (5)
C7	0.66198 (14)	0.50636 (18)	0.13054 (12)	0.0543 (5)
H7A	0.6465 (12)	0.4365 (16)	0.1201 (11)	0.061 (6)*
H7B	0.6220 (13)	0.5541 (16)	0.1070 (11)	0.059 (6)*
N8	0.64949 (9)	0.51866 (12)	0.21565 (8)	0.0471 (4)
C9	0.59245 (13)	0.58583 (16)	0.24177 (13)	0.0558 (5)
H9	0.5610 (14)	0.6265 (16)	0.2018 (13)	0.072 (6)*
C10	0.57958 (14)	0.59714 (16)	0.31935 (12)	0.0570 (5)
H10	0.5376 (12)	0.6412 (15)	0.3363 (11)	0.057 (6)*
C11	0.62580 (12)	0.54012 (14)	0.37345 (11)	0.0480 (5)
C12	0.68355 (13)	0.47080 (17)	0.34404 (12)	0.0529 (5)
H12	0.7124 (12)	0.4296 (14)	0.3758 (11)	0.045 (5)*
C13	0.69390 (13)	0.46087 (16)	0.26622 (12)	0.0510 (5)
H13	0.7319 (13)	0.4147 (17)	0.2441 (11)	0.068 (6)*
C14	0.61720 (13)	0.55005 (16)	0.45695 (12)	0.0533 (5)
H14	0.6555 (13)	0.5085 (15)	0.4908 (12)	0.067 (6)*
C15	0.55798 (13)	0.60570 (15)	0.49147 (11)	0.0494 (5)
H15	0.5157 (12)	0.6448 (15)	0.4591 (11)	0.062 (6)*
C16	0.54635 (11)	0.61733 (13)	0.57538 (11)	0.0452 (5)
C17	0.48510 (13)	0.68467 (14)	0.60095 (11)	0.0496 (5)
H17	0.4497 (12)	0.7204 (14)	0.5625 (11)	0.052 (5)*
C18	0.47185 (12)	0.69927 (14)	0.67949 (12)	0.0507 (5)
O18	0.41092 (11)	0.76638 (12)	0.70035 (10)	0.0728 (5)
H18	0.4022 (15)	0.7635 (17)	0.7475 (6)	0.073 (8)*
C19	0.52022 (13)	0.64576 (16)	0.73299 (12)	0.0562 (5)
H19	0.5119 (11)	0.6536 (14)	0.7852 (12)	0.053 (5)*
C20	0.58050 (14)	0.57837 (19)	0.70838 (13)	0.0638 (6)
H20	0.6134 (15)	0.5416 (17)	0.7443 (13)	0.078 (7)*
C21	0.59357 (13)	0.56333 (18)	0.63016 (12)	0.0556 (5)
H21	0.6331 (12)	0.5156 (15)	0.6163 (10)	0.056 (6)*
Cl2	0.38041 (4)	0.75662 (5)	0.87690 (4)	0.0856 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1W	0.107 (2)	0.0766 (17)	0.0819 (17)	0.000	0.0285 (15)	0.000
C1	0.0563 (12)	0.0455 (11)	0.0456 (11)	0.0052 (9)	0.0027 (9)	−0.0003 (9)
Cl1	0.0802 (4)	0.0513 (3)	0.1126 (5)	0.0128 (3)	0.0217 (4)	−0.0001 (3)
C2	0.0639 (14)	0.0511 (12)	0.0535 (12)	−0.0068 (11)	0.0075 (10)	0.0036 (11)
C3	0.0552 (13)	0.0774 (16)	0.0522 (12)	0.0004 (12)	0.0107 (11)	0.0031 (12)
C4	0.0687 (15)	0.0697 (15)	0.0595 (14)	0.0204 (12)	0.0179 (11)	0.0048 (12)
C5	0.0707 (14)	0.0472 (12)	0.0517 (12)	0.0032 (11)	0.0102 (10)	0.0006 (10)
C6	0.0514 (11)	0.0491 (11)	0.0372 (9)	−0.0027 (9)	0.0018 (8)	−0.0025 (9)
C7	0.0546 (13)	0.0592 (14)	0.0491 (12)	−0.0075 (11)	0.0012 (10)	−0.0037 (11)
N8	0.0448 (9)	0.0486 (9)	0.0483 (9)	−0.0056 (7)	0.0059 (7)	0.0008 (8)
C9	0.0569 (13)	0.0585 (13)	0.0520 (12)	0.0051 (10)	0.0032 (10)	0.0012 (11)
C10	0.0602 (13)	0.0542 (12)	0.0570 (13)	0.0092 (10)	0.0071 (11)	−0.0023 (11)
C11	0.0481 (11)	0.0465 (11)	0.0494 (11)	−0.0091 (9)	0.0039 (9)	0.0015 (9)
C12	0.0477 (12)	0.0561 (12)	0.0551 (12)	−0.0014 (9)	0.0035 (10)	0.0126 (11)
C13	0.0465 (11)	0.0498 (12)	0.0572 (12)	−0.0001 (9)	0.0116 (10)	0.0069 (10)
C14	0.0533 (12)	0.0557 (12)	0.0513 (12)	−0.0061 (10)	0.0064 (10)	0.0017 (10)
C15	0.0531 (12)	0.0468 (11)	0.0482 (11)	−0.0104 (9)	0.0011 (10)	0.0031 (10)
C16	0.0476 (11)	0.0404 (10)	0.0477 (11)	−0.0108 (8)	0.0002 (9)	0.0009 (9)
C17	0.0565 (12)	0.0416 (10)	0.0506 (12)	−0.0058 (9)	−0.0036 (10)	0.0065 (10)
C18	0.0517 (12)	0.0430 (10)	0.0575 (12)	−0.0055 (9)	0.0025 (10)	−0.0034 (10)
O18	0.0873 (12)	0.0669 (10)	0.0647 (11)	0.0217 (8)	0.0107 (9)	−0.0025 (9)
C19	0.0592 (13)	0.0678 (14)	0.0418 (12)	−0.0035 (11)	0.0042 (10)	−0.0027 (11)
C20	0.0550 (13)	0.0836 (16)	0.0525 (13)	0.0070 (12)	−0.0041 (11)	0.0055 (12)
C21	0.0489 (12)	0.0643 (14)	0.0537 (13)	0.0047 (10)	0.0051 (10)	0.0011 (11)
Cl2	0.0931 (5)	0.0774 (4)	0.0883 (5)	−0.0237 (3)	0.0430 (4)	−0.0245 (3)

Geometric parameters (Å, º)

O1W—H1WA	0.95 (3)	C11—C12	1.392 (3)
C1—C2	1.378 (3)	C11—C14	1.454 (3)
C1—C6	1.390 (2)	C12—C13	1.360 (3)
C1—Cl1	1.7346 (19)	C12—H12	0.888 (19)
C2—C3	1.364 (3)	C13—H13	0.94 (2)
C2—H2	0.93 (2)	C14—C15	1.334 (3)
C3—C4	1.365 (3)	C14—H14	0.99 (2)
C3—H3	0.99 (2)	C15—C16	1.469 (3)
C4—C5	1.387 (3)	C15—H15	1.00 (2)
C4—H4	0.98 (2)	C16—C21	1.384 (3)
C5—C6	1.383 (3)	C16—C17	1.389 (3)
C5—H5	0.98 (2)	C17—C18	1.387 (3)
C6—C7	1.502 (3)	C17—H17	0.976 (19)
C7—N8	1.492 (2)	C18—O18	1.358 (2)
C7—H7A	0.97 (2)	C18—C19	1.375 (3)
C7—H7B	0.97 (2)	O18—H18	0.827 (10)
N8—C13	1.342 (2)	C19—C20	1.373 (3)
N8—C9	1.346 (2)	C19—H19	0.918 (19)
C9—C10	1.364 (3)	C20—C21	1.382 (3)
C9—H9	0.99 (2)	C20—H20	0.93 (2)
C10—C11	1.389 (3)	C21—H21	0.920 (19)
C10—H10	0.93 (2)
C2—C1—C6	121.20 (18)	C10—C11—C14	123.74 (19)
C2—C1—Cl1	118.47 (16)	C12—C11—C14	119.72 (19)
C6—C1—Cl1	120.34 (15)	C13—C12—C11	121.0 (2)
C3—C2—C1	119.7 (2)	C13—C12—H12	118.5 (12)
C3—C2—H2	122.7 (12)	C11—C12—H12	120.4 (12)
C1—C2—H2	117.6 (12)	N8—C13—C12	120.8 (2)
C2—C3—C4	120.5 (2)	N8—C13—H13	115.6 (12)
C2—C3—H3	118.4 (12)	C12—C13—H13	123.6 (12)
C4—C3—H3	121.2 (12)	C15—C14—C11	124.9 (2)
C3—C4—C5	120.1 (2)	C15—C14—H14	117.4 (12)
C3—C4—H4	122.4 (12)	C11—C14—H14	117.5 (12)
C5—C4—H4	117.5 (12)	C14—C15—C16	126.8 (2)
C6—C5—C4	120.6 (2)	C14—C15—H15	119.7 (11)
C6—C5—H5	120.6 (12)	C16—C15—H15	113.5 (11)
C4—C5—H5	118.8 (12)	C21—C16—C17	118.51 (18)
C5—C6—C1	117.95 (18)	C21—C16—C15	122.68 (18)
C5—C6—C7	120.18 (18)	C17—C16—C15	118.80 (18)
C1—C6—C7	121.86 (18)	C18—C17—C16	121.28 (19)
N8—C7—C6	112.06 (16)	C18—C17—H17	120.0 (11)
N8—C7—H7A	104.4 (11)	C16—C17—H17	118.7 (11)
C6—C7—H7A	110.9 (11)	O18—C18—C19	122.59 (18)
N8—C7—H7B	103.9 (12)	O18—C18—C17	118.13 (19)
C6—C7—H7B	112.2 (12)	C19—C18—C17	119.28 (19)
H7A—C7—H7B	113.0 (17)	C18—O18—H18	111.2 (17)
C13—N8—C9	119.88 (17)	C20—C19—C18	119.96 (19)
C13—N8—C7	119.83 (17)	C20—C19—H19	119.3 (12)
C9—N8—C7	120.27 (17)	C18—C19—H19	120.7 (12)
N8—C9—C10	121.0 (2)	C19—C20—C21	120.9 (2)
N8—C9—H9	116.6 (12)	C19—C20—H20	120.5 (14)
C10—C9—H9	122.4 (12)	C21—C20—H20	118.6 (14)
C9—C10—C11	120.7 (2)	C20—C21—C16	120.1 (2)
C9—C10—H10	119.8 (12)	C20—C21—H21	117.8 (12)
C11—C10—H10	119.4 (12)	C16—C21—H21	122.0 (12)
C10—C11—C12	116.54 (18)
C6—C1—C2—C3	−0.8 (3)	C10—C11—C12—C13	0.5 (3)
Cl1—C1—C2—C3	179.02 (16)	C14—C11—C12—C13	−179.03 (18)
C1—C2—C3—C4	0.4 (3)	C9—N8—C13—C12	−1.5 (3)
C2—C3—C4—C5	0.4 (3)	C7—N8—C13—C12	179.99 (17)
C3—C4—C5—C6	−0.8 (3)	C11—C12—C13—N8	0.9 (3)
C4—C5—C6—C1	0.5 (3)	C10—C11—C14—C15	8.0 (3)
C4—C5—C6—C7	−179.87 (19)	C12—C11—C14—C15	−172.49 (19)
C2—C1—C6—C5	0.3 (3)	C11—C14—C15—C16	179.44 (17)
Cl1—C1—C6—C5	−179.49 (14)	C14—C15—C16—C21	−5.3 (3)
C2—C1—C6—C7	−179.31 (18)	C14—C15—C16—C17	175.16 (19)
Cl1—C1—C6—C7	0.9 (3)	C21—C16—C17—C18	1.0 (3)
C5—C6—C7—N8	101.2 (2)	C15—C16—C17—C18	−179.48 (17)
C1—C6—C7—N8	−79.2 (2)	C16—C17—C18—O18	179.94 (17)
C6—C7—N8—C13	−60.6 (2)	C16—C17—C18—C19	−0.2 (3)
C6—C7—N8—C9	121.0 (2)	O18—C18—C19—C20	179.5 (2)
C13—N8—C9—C10	0.8 (3)	C17—C18—C19—C20	−0.3 (3)
C7—N8—C9—C10	179.23 (19)	C18—C19—C20—C21	0.1 (3)
N8—C9—C10—C11	0.7 (3)	C19—C20—C21—C16	0.8 (3)
C9—C10—C11—C12	−1.2 (3)	C17—C16—C21—C20	−1.3 (3)
C9—C10—C11—C14	178.26 (19)	C15—C16—C21—C20	179.22 (18)

(II) 1-(2-bromobenzyl)-4-[(E)-2-(3-hydroxyphenyl)ethenyl]pyridinium bromide hemihydrate

Crystal data

C20H17BrNO^+·Br^−·0.5H2O	F(000) = 1816
Mr = 456.17	Dx = 1.653 Mg m^−3
Monoclinic, I2/a	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -I 2ya	Cell parameters from 6672 reflections
a = 15.6975 (8) Å	θ = 3–25°
b = 13.5505 (7) Å	µ = 4.43 mm^−1
c = 17.2562 (10) Å	T = 294 K
β = 92.879 (4)°	Block, colourless
V = 3665.9 (3) Å^3	0.4 × 0.2 × 0.2 mm
Z = 8

Data collection

Kuma KM4 CCD area-detector diffractometer	3406 independent reflections
Radiation source: fine-focus sealed tube	2132 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.026
ω scans	θmax = 25.5°, θmin = 2.6°
Absorption correction: multi-scan CrysAlis RED; Oxford Diffraction, 2007)	h = −19→18
Tmin = 0.186, Tmax = 0.412	k = −16→16
16057 measured reflections	l = −20→20

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)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.074	H atoms treated by a mixture of independent and constrained refinement
S = 1.07	w = 1/[σ^2(Fo^2) + (0.035P)^2] where P = (Fo^2 + 2Fc^2)/3
3406 reflections	(Δ/σ)max = 0.001
225 parameters	Δρmax = 0.34 e Å^−3
1 restraint	Δρmin = −0.49 e Å^−3

Special details

Experimental. Spectroscopic data: (II) IR (KBr, cm^-1): 3160.1, 2980.7, 2930.9, 1595.3, 1545.0, 1440.6, 1251.8, 1150.1, 990.1, 952.7,870.0, 745.8, 682.6, 511.9. ¹H NMR (DMSO-d₆): δ = 9.75 (s, 1H,-OH), 8.98 (d, J = 6.7 Hz, 2H, o-H in –⁺NC₅H₄),8.33 (d, J = 6.8 Hz, 2H, m-H in –⁺NC₅H₄), 8.01 (d, J = 16.2 Hz, 1H, –⁺NC₅H₄-CH═), 7.72 (d, J = 7.8 Hz, 1H, m-H in BrC₆H₄CH₂-), 7.53–7.21 (m, 5H), 7.35 (d, J = 16.2 Hz, 1H, HOC₆H₄-CH═), 7.16 (s, 1H, o-H in phenyl ring), 6.90 (d, J = 7.6 Hz, 1H, p-H in phenyl ring), 5.91 (s, 2H, -CH₂-N⁺). ¹³C NMR (DMSO-d₆): δ = 157.6, 153.5, 144.6, 141.7, 136.2, 133.2, 131.2, 130.9, 129.9, 128.5, 124.0, 123.1,122.9, 119.2, 117.7, 114.5, 62.2. m.p. 498–501 K.

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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
O1W	0.7500	0.3473 (3)	0.5000	0.0862 (11)
H1WA	0.716 (2)	0.314 (2)	0.527 (2)	0.103*
C1	0.78943 (18)	0.62299 (19)	0.10153 (15)	0.0398 (7)
Br1	0.72086 (2)	0.73495 (2)	0.11863 (2)	0.06630 (14)
C2	0.87273 (19)	0.6386 (2)	0.08250 (16)	0.0496 (8)
H2	0.8936	0.7025	0.0780	0.059*
C3	0.92471 (19)	0.5589 (2)	0.07024 (17)	0.0537 (8)
H3	0.9809	0.5688	0.0574	0.064*
C4	0.8938 (2)	0.4651 (2)	0.07685 (17)	0.0550 (9)
H4	0.9292	0.4114	0.0686	0.066*
C5	0.81087 (19)	0.4497 (2)	0.09559 (16)	0.0479 (8)
H5	0.7905	0.3856	0.0998	0.058*
C6	0.75707 (17)	0.52886 (19)	0.10828 (15)	0.0383 (7)
C7	0.66525 (17)	0.5093 (2)	0.12722 (15)	0.0449 (7)
H7A	0.6283	0.5553	0.0985	0.054*
H7B	0.6495	0.4431	0.1107	0.054*
N8	0.65187 (14)	0.51971 (15)	0.21181 (13)	0.0393 (6)
C9	0.59476 (19)	0.5856 (2)	0.23682 (18)	0.0478 (8)
H9	0.5640	0.6245	0.2010	0.057*
C10	0.58173 (18)	0.5957 (2)	0.31365 (17)	0.0480 (8)
H10	0.5421	0.6414	0.3296	0.058*
C11	0.62700 (17)	0.53840 (19)	0.36921 (17)	0.0392 (7)
C12	0.68337 (18)	0.4692 (2)	0.34086 (17)	0.0438 (7)
H12	0.7138	0.4280	0.3753	0.053*
C13	0.69427 (17)	0.4614 (2)	0.26331 (17)	0.0453 (8)
H13	0.7320	0.4145	0.2457	0.054*
C14	0.61770 (18)	0.5473 (2)	0.45234 (17)	0.0455 (7)
H14	0.6550	0.5111	0.4849	0.055*
C15	0.56028 (17)	0.60282 (19)	0.48545 (16)	0.0425 (7)
H15	0.5231	0.6382	0.4522	0.051*
C16	0.54906 (17)	0.61448 (18)	0.56835 (16)	0.0386 (7)
C17	0.48876 (18)	0.68242 (19)	0.59130 (16)	0.0442 (7)
H17	0.4571	0.7182	0.5539	0.053*
C18	0.47529 (18)	0.6973 (2)	0.66915 (17)	0.0449 (7)
O18	0.41565 (15)	0.76524 (13)	0.68744 (13)	0.0649 (6)
H18	0.4067	0.7611	0.7337	0.078*
C19	0.52132 (19)	0.6443 (2)	0.72476 (17)	0.0488 (8)
H19	0.5127	0.6546	0.7771	0.059*
C20	0.58073 (19)	0.5755 (2)	0.70249 (18)	0.0545 (8)
H20	0.6116	0.5392	0.7401	0.065*
C21	0.59442 (17)	0.5604 (2)	0.62496 (18)	0.0475 (8)
H21	0.6342	0.5138	0.6106	0.057*
Br2	0.37663 (3)	0.75723 (2)	0.86960 (2)	0.06969 (15)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1W	0.106 (3)	0.080 (3)	0.075 (3)	0.000	0.030 (2)	0.000
C1	0.0460 (18)	0.0371 (15)	0.0363 (17)	0.0054 (13)	0.0023 (14)	0.0008 (13)
Br1	0.0643 (2)	0.04165 (19)	0.0946 (3)	0.00760 (15)	0.0197 (2)	−0.00045 (17)
C2	0.052 (2)	0.0497 (18)	0.047 (2)	−0.0071 (15)	0.0077 (16)	0.0035 (15)
C3	0.0426 (19)	0.075 (2)	0.045 (2)	0.0048 (17)	0.0106 (15)	0.0051 (17)
C4	0.058 (2)	0.055 (2)	0.053 (2)	0.0173 (17)	0.0129 (17)	0.0046 (16)
C5	0.058 (2)	0.0416 (17)	0.0453 (19)	0.0048 (14)	0.0123 (16)	0.0036 (14)
C6	0.0411 (17)	0.0444 (17)	0.0294 (16)	0.0004 (14)	0.0028 (13)	0.0002 (13)
C7	0.050 (2)	0.0460 (17)	0.0392 (18)	−0.0074 (14)	0.0020 (14)	−0.0049 (14)
N8	0.0386 (14)	0.0395 (13)	0.0403 (15)	−0.0049 (11)	0.0048 (12)	0.0003 (11)
C9	0.0479 (19)	0.0449 (17)	0.050 (2)	0.0073 (14)	0.0023 (15)	0.0065 (15)
C10	0.049 (2)	0.0469 (17)	0.049 (2)	0.0059 (14)	0.0090 (16)	−0.0049 (15)
C11	0.0368 (17)	0.0389 (15)	0.0422 (18)	−0.0082 (13)	0.0052 (14)	−0.0007 (14)
C12	0.0426 (18)	0.0461 (17)	0.0427 (19)	−0.0013 (14)	0.0013 (15)	0.0072 (14)
C13	0.0409 (18)	0.0413 (16)	0.054 (2)	0.0011 (13)	0.0076 (16)	0.0022 (15)
C14	0.0431 (18)	0.0485 (17)	0.0452 (19)	−0.0033 (14)	0.0047 (15)	−0.0004 (15)
C15	0.0446 (18)	0.0374 (15)	0.0452 (19)	−0.0090 (13)	−0.0001 (14)	0.0010 (14)
C16	0.0409 (18)	0.0350 (15)	0.0401 (18)	−0.0117 (13)	0.0034 (14)	−0.0036 (13)
C17	0.0534 (19)	0.0386 (16)	0.0407 (19)	−0.0032 (14)	0.0015 (15)	0.0011 (13)
C18	0.0516 (19)	0.0349 (15)	0.048 (2)	−0.0037 (14)	0.0036 (16)	0.0003 (14)
O18	0.0840 (17)	0.0552 (13)	0.0565 (14)	0.0243 (12)	0.0146 (13)	0.0015 (11)
C19	0.057 (2)	0.0520 (19)	0.0379 (19)	−0.0036 (15)	0.0032 (16)	−0.0001 (15)
C20	0.054 (2)	0.064 (2)	0.045 (2)	0.0059 (16)	−0.0072 (16)	0.0063 (16)
C21	0.0403 (19)	0.0485 (18)	0.053 (2)	0.0050 (14)	−0.0001 (16)	−0.0023 (15)
Br2	0.0758 (3)	0.0649 (2)	0.0709 (3)	−0.01741 (18)	0.0295 (2)	−0.01868 (18)

Geometric parameters (Å, º)

O1W—H1WA	0.855 (10)	C11—C12	1.395 (4)
C1—C6	1.380 (3)	C11—C14	1.454 (4)
C1—C2	1.380 (4)	C12—C13	1.362 (4)
C1—Br1	1.892 (3)	C12—H12	0.9300
C2—C3	1.377 (4)	C13—H13	0.9300
C2—H2	0.9300	C14—C15	1.326 (3)
C3—C4	1.367 (4)	C14—H14	0.9300
C3—H3	0.9300	C15—C16	1.459 (4)
C4—C5	1.373 (4)	C15—H15	0.9300
C4—H4	0.9300	C16—C21	1.389 (4)
C5—C6	1.389 (4)	C16—C17	1.392 (4)
C5—H5	0.9300	C17—C18	1.385 (4)
C6—C7	1.517 (3)	C17—H17	0.9300
C7—N8	1.492 (3)	C18—O18	1.361 (3)
C7—H7A	0.9700	C18—C19	1.374 (4)
C7—H7B	0.9700	O18—H18	0.8200
N8—C13	1.341 (3)	C19—C20	1.387 (4)
N8—C9	1.351 (3)	C19—H19	0.9300
C9—C10	1.359 (4)	C20—C21	1.381 (4)
C9—H9	0.9300	C20—H20	0.9300
C10—C11	1.399 (4)	C21—H21	0.9300
C10—H10	0.9300
C6—C1—C2	121.3 (2)	C12—C11—C14	119.9 (3)
C6—C1—Br1	120.9 (2)	C10—C11—C14	123.9 (3)
C2—C1—Br1	117.9 (2)	C13—C12—C11	120.7 (3)
C3—C2—C1	119.5 (3)	C13—C12—H12	119.7
C3—C2—H2	120.3	C11—C12—H12	119.7
C1—C2—H2	120.3	N8—C13—C12	121.5 (3)
C4—C3—C2	120.1 (3)	N8—C13—H13	119.2
C4—C3—H3	120.0	C12—C13—H13	119.2
C2—C3—H3	120.0	C15—C14—C11	125.2 (3)
C3—C4—C5	120.3 (3)	C15—C14—H14	117.4
C3—C4—H4	119.8	C11—C14—H14	117.4
C5—C4—H4	119.8	C14—C15—C16	127.0 (3)
C4—C5—C6	120.7 (3)	C14—C15—H15	116.5
C4—C5—H5	119.6	C16—C15—H15	116.5
C6—C5—H5	119.6	C21—C16—C17	118.7 (3)
C1—C6—C5	118.1 (2)	C21—C16—C15	123.3 (3)
C1—C6—C7	122.5 (2)	C17—C16—C15	117.9 (3)
C5—C6—C7	119.4 (2)	C18—C17—C16	120.8 (3)
N8—C7—C6	112.1 (2)	C18—C17—H17	119.6
N8—C7—H7A	109.2	C16—C17—H17	119.6
C6—C7—H7A	109.2	O18—C18—C19	122.3 (3)
N8—C7—H7B	109.2	O18—C18—C17	117.6 (3)
C6—C7—H7B	109.2	C19—C18—C17	120.0 (3)
H7A—C7—H7B	107.9	C18—O18—H18	109.5
C13—N8—C9	119.5 (2)	C18—C19—C20	119.7 (3)
C13—N8—C7	120.2 (2)	C18—C19—H19	120.2
C9—N8—C7	120.2 (2)	C20—C19—H19	120.2
N8—C9—C10	120.9 (3)	C21—C20—C19	120.5 (3)
N8—C9—H9	119.6	C21—C20—H20	119.7
C10—C9—H9	119.6	C19—C20—H20	119.7
C9—C10—C11	121.1 (3)	C20—C21—C16	120.2 (3)
C9—C10—H10	119.4	C20—C21—H21	119.9
C11—C10—H10	119.4	C16—C21—H21	119.9
C12—C11—C10	116.2 (3)
C6—C1—C2—C3	−0.2 (4)	C10—C11—C12—C13	1.8 (4)
Br1—C1—C2—C3	179.5 (2)	C14—C11—C12—C13	−178.5 (2)
C1—C2—C3—C4	0.0 (5)	C9—N8—C13—C12	−2.3 (4)
C2—C3—C4—C5	0.1 (5)	C7—N8—C13—C12	180.0 (2)
C3—C4—C5—C6	−0.1 (5)	C11—C12—C13—N8	0.3 (4)
C2—C1—C6—C5	0.2 (4)	C12—C11—C14—C15	−172.8 (3)
Br1—C1—C6—C5	−179.5 (2)	C10—C11—C14—C15	6.8 (4)
C2—C1—C6—C7	−178.5 (3)	C11—C14—C15—C16	−179.5 (2)
Br1—C1—C6—C7	1.8 (4)	C14—C15—C16—C21	−5.7 (4)
C4—C5—C6—C1	0.0 (4)	C14—C15—C16—C17	175.3 (3)
C4—C5—C6—C7	178.7 (3)	C21—C16—C17—C18	1.3 (4)
C1—C6—C7—N8	−80.0 (3)	C15—C16—C17—C18	−179.7 (2)
C5—C6—C7—N8	101.4 (3)	C16—C17—C18—O18	179.7 (2)
C6—C7—N8—C13	−60.9 (3)	C16—C17—C18—C19	−0.4 (4)
C6—C7—N8—C9	121.4 (3)	O18—C18—C19—C20	179.4 (3)
C13—N8—C9—C10	2.1 (4)	C17—C18—C19—C20	−0.5 (4)
C7—N8—C9—C10	179.8 (2)	C18—C19—C20—C21	0.5 (4)
N8—C9—C10—C11	0.1 (4)	C19—C20—C21—C16	0.4 (4)
C9—C10—C11—C12	−2.0 (4)	C17—C16—C21—C20	−1.2 (4)
C9—C10—C11—C14	178.4 (3)	C15—C16—C21—C20	179.8 (3)