Three 2,5-dialkoxy-1,4-diethynyl­benzene derivatives

2,5-Dieth­oxy-1,4-bis­[(trimethyl­silyl)ethyn­yl]benzene, C₂₀H₃₀O₂Si₂, (I), constitutes one of the first structurally characterized examples of a family of compounds, viz. the 2,5-dialk­oxy-1,4-bis­[(trimethyl­silyl)ethyn­yl]benzene derivatives, used in the preparation of oligo(phenyl­ene­ethynylene)s via Pd/Cu-catalysed cross-coupling. 2,5-Dieth­oxy-1,4-diethynylbenzene, C₁₄H₁₄O₂, (II), results from protodesilylation of (I). 1,4-Diethynyl-2,5-bis­(hept­yloxy)benzene, C₂₄H₃₄O₂, (III), is a long alk­yloxy chain analogue of (II). The molecules of compounds (I)-(III) are located on sites with crystallographic inversion symmetry. The large substituents either in the alkynyl group or in the benzene ring have a marked effect on the packing and inter­molecular inter­actions of adjacent mol­ecules. All the compounds exhibit weak inter­molecular inter­actions that are only slightly shorter than the sum of the van der Waals radii of the inter­acting atoms. Compound (I) displays C-H...[pi] inter­actions between the methyl­ene H atoms and the acetyl­enic C atom. Compound (II) shows [pi]-[pi] inter­actions between the acetyl­enic C atoms, complemented by C-H...[pi] inter­actions between the methyl H atoms and the acetyl­enic C atoms. Unlike (I) or (II), compound (III) has weak nonclassical hydrogen-bond-type inter­actions between the acetyl­enic H atoms and the ether O atoms.

S1. Comment

Among the variety of highly conjugated polymers, those composed of alternating aryl and ethynyl units, such as the oligo(phenyleneethynylene)s (OPEs), a type of monodisperse and shaped-persistent oligomer, have been the object of increasing interest in academic and industrial research laboratories owing to their potential applications as molecular wires (Kushmerick et al., 2002; Tour, 2000; Reinerth et al., 1998; Cygan et al., 1998; Bumm et al.,1996), rectifiers (Dhirani et al., 1997), data storage systems (Reed et al., 2001; Feringa et al., 1993), photoluminescent and electroluminescent devices (Yamaguchi et al., 2005), and nonlinear optical materials (Koynov et al., 2005; Meier et al., 2001). Modification of OPEs is needed in order to improve both processability and long-term stability. One of the methods for improving their stability and solubility is the attachment of long linear alkoxy side chains to the main backbone. Additionally, alkoxy side chains can also lead to highly ordered supramolecular architectures and reduce the HOMO–LUMO gap and the band gap in the solid state (Wackerly & Moore, 2006; Jiang et al., 2004; Zhou et al., 2004; Zhou, Liu et al., 2003; Zhou, Zhao et al., 2003; Meier et al., 2001; Perahia et al., 2001; Müllen & Rabe, 1998). A possible way to synthesize OPEs with alkoxy side chains is by using a two-step Sonogashira–Hagihara reaction; a palladium-catalyzed cross-coupling condensation between 2,5-bis(alkoxy)benzene halides and terminal trimethylsilylacetylenes or 2-methylbut-3-yn-2-ol as the protecting group precursors in the presence of CuI, followed by a base-promoted deprotection of the capped acetylides (Tykwinski, 2003; Sonogashira, 2002; Takahashi et al. 1980; Zhao et al.,2007). The structure of trimethylsilylated 1,4-diethynylbenzene (Weiss et al., 1997; Ahmed et al.,1972) and 2,5-bis(alkoxy) ring-substituted derivatives, 1,4-bis(ethynyl)-2,5-bis(methoxy)benzene and 1,4-bis(ethynyl)-2,5-bis(octyloxy)benzene (Khan et al. 2003) are known. The X-ray structures of 1,4-bis(trimethylsilylethynyl)naphthalene and 9,10-bis(trimethylsilylethynyl)anthracene were reported by Khan et al. (2004).

Compound (I) is symmetrical and shows the expected planar overall structure (Fig. 1). The bond distances and angles do not show any abnormal values. The prevailing intermolecular interactions (defined to be shorter than the sum of the van der Waals radii of the interacting atoms) in compound (I) is the C–H···π interaction between the methylene H atoms of the ethoxy group and the terminal acetylenic C atom (C6—H6B···C1), with an interaction distance of 2.86 Å and angle 153°, the C···C distance being 3.772 (4) Å (Fig. 2, only the stronger interactions shown). One molecule of (I) has these interactions to four separate molecules [(1 - x, -1/2 + y, 1/2 - z), (x, -1/2 - y, 1/2 + z); (1 - x, 1/2 + y, -1/2 - z) and (x, 1/2 - y, 1/2 + z)]. Another but weaker intermolecular interaction is also present between the H atoms of the adjacent trimethylsilyl groups, [H8A···H9B(1 - x, 1/2 - y, 1/2 + z)] with a contact distance of 2.39 Å.

Compound (II) does not have the bulky trimethylsilyl groups and thus shows different packing behaviour. Like (I), compound (II) is symmetrical and planar with no abnormal bond distances and angles (Fig. 3). The absence of the bulky trimethylsilyl group allows the molecules a closer approach and completely different packing results with interactions to eight separate molecules [(-x, 1 - y, -z), (-x,-1 - y, -z), (x,-1/2 - y, -1/2 + z), (-x, -1/2 + y, 1/2 - z), (x, 1/2 - y, -1/2 + z) and (-1 + x, y, -1 + z)]. The molecules of (II) are arranged in planes with π–π interactions between the acetylenic C1 atoms of adjacent molecules, the C1···C1 distance being 3.224 (2) Å. In addition to the π–π interactions, in-plane C—H···π interaction between the acetylenic atom C1 and the methyl atom H7B exist, the contact distance C1··· H7B(x, -1 + y, z) being 2.88 Å (Fig. 4). These planes stack on top of each other with a twist angle of 36.7° between the planes. The C–H···π interactions between the planes are mediated through methylene H atoms (H6A) and the phenyl π system(C4) of adjacent molecules, the contact distance H6A···C4(x, -1/2 - y, -1/2 + z) being 2.85 Å.

The long heptyloxy chain has an opposite effect on the packing when compared with compound (II). Compound (III) is symmetrical and planar, like the other two compounds, and the bond distances and angles within the molecule are normal (Fig. 5). Unlike (I) and (II), compound (III) exhibits, as the only sufficiently short intermolecular interaction, a nonclassical hydrogen bond between the molecules (Fig. 6). The contact distance between atoms H1 and O1(-1/2 + x, 3/2 - y, z) is 2.54 Å, with an angle of 161° and C···O distance of 3.449 (2) Å. Similar contact distances are frequently found in nonclassical hydrogen bonds. As in (I), each molecule of (III) interacts with four other molecules [(-1/2 - x, -1/2 + y, -z), (-1/2 + x, 3/2 - y, -z), (-1/2 - x, -1/2 + y, -z) and (1/2 + x, 3/2 - y, z)]. Even though the bond lengths in all three compounds do not show abnormal values, there is a significant variation in the bond lengths of the central benzene ring typical for this type of symmetrical tetrasubstituted benzenes. The bond length of the unsubstituted atom C4 and the alkoxy-substituted atom C5 is on avarage 0.034 Å [for (I)], 0.015 Å [for (II)] and 0.010 Å [for (III)] shorter than the other bond lengths in the benzene ring.

Related literature

For related literature, see: Ahmed et al. (1972); Bumm et al. (1996); Cygan et al. (1998); Dhirani et al. (1997); Feringa et al. (1993); Jiang et al. (2004); Khan et al. (2003, 2004); Koynov et al. (2005); Kushmerick et al. (2002); Müllen & Rabe (1998); Meier et al. (2001); Perahia et al. (2001); Reed et al. (2001); Reinerth et al. (1998); Sonogashira (2002); Takahashi et al. (1980); Tour (2000); Tykwinski (2003); Wackerly & Moore (2006); Weder & Wrighton (1996); Weiss et al. (1997); Yamaguchi et al. (2005); Zhao et al. (2007); Zhou, Liu et al. (2003); Zhou, Zhao et al. (2003); Zhou et al. (2004).

S2. Experimental

Compound (I) was obtained by Sonogashira cross-coupling (Weder & Wrighton, 1996) of 1,4-diethoxy-2,5-diiodobenzene (1.50 g, 3.59 mmol) with TMSA [give name in full] (1.5 ml, 10.54 mmol) in dried tetrahydrofuran (20 ml) and DIEA [in full] (25 ml). The reaction was catalysed by PdCl₂(PPh₃)₂ (0.293 g, 0.42 mmol) and CuI (0.06 g, 0.32 mmol). After 16 h of stirring at 318 K under nitrogen atmosphere, the dark-brown mixture was filtered and evaporated under vacuum. Purification over column chromatography (silica gel S60, CH₂Cl₂/cyclohexane 1:3) gave a dark-yellow solid that was further purified by sublimation. The resulting solid was dissolved in CH₂Cl₂, forming a light-yellow solution which was slowly evaporated in air at room temperature, affording yellow crystals in 35% yield (m.p. 305–309 K). ¹H NMR (500 MHz, CDCl₃): δ 6.89 (2H, s, Ar), 4.02 (4H, q, CH₂, J_HH = 14 Hz), 1.40 (4H, t, Me, J_HH = 14 Hz), 0.29 (18H, s, Me); ¹³C NMR (126 MHz, CDCl₃): 153.97, 117.75, 101.06, 100.24, 65.30, 14.79, 0.058; IR (KBr): 2969 (s), 2151 (s), 1499 (s), 1394 (s), 1213 (sh),1043 (s), 840 (br), 760 (s).

Compound (II) was obtained by adding K₂CO₃ (1.61 g, 11.6 mmol) to (I) (1.91 g, 5.3 mmol) in a purged Schlenk tube. Degassed CH₂Cl₂ (7 ml) and MeOH (3 ml) were then added to the solids, forming a yellow solution, and stirring was begun. After 4 h at room temperature, the now fuzzy [cloudy?] yellow mixture was filtrated and evaporated under vacuum, yielding a light-yellow solid. Yellow crystals suitable for X-ray diffraction were obtained as previously described for compound (I) (yield 73.8%, m.p 347–348 K). ¹H NMR (500 MHz, CDCl₃): δ 6.89 (2H, s, Ar), 4.07 (4H, q, CH₂, J_HH = 14 Hz), 3.40 (2H, s, H—CC), 1.43 (6H, t, CH₃, J_HH = 14 Hz); ¹³C NMR (126 MHz, CDCl₃): 153.83, 117.92, 113.36, 82.42, 79.79, 65.20, 14.75; IR (KBr): 3288 (s), 2984 (s), 2932 (s), 2883 (s), 2107 (s), 1932 (s), 1496 (m), 1218 (m), 1040 (s), 674 (m). MS (ESI): 158 [M⁺– (C₂H₅)₂ + H₂], 214 (M⁺) m/z.

Compound (III) was prepared by refluxing 4,4'-[2,5-bis(heptyloxy)-1,4-phenylene]bis(2-methylbut-3-yn-2-ol) in toluene with high excess of NaOH for 4 h. After this, the still hot solution was filtered and concentrated under vacuum. Good quality single crystals were obtained by allowing the yellow solution to cool to room temperature (yield 99%, m.p. 346–347 K). ¹H NMR (250 MHz, CDCl₃): δ 6.95 (2H, s, Ar), 3.97 (4H, t, CH₂, J_HH = 27 Hz), 3.32 (2H, s, H—CC), 1.76 (4H, Q, CH₂, J_HH = 27 Hz), 1.469–1.257 [16H, (CH₂)₄], 0.89 (3H, d, CH₃, J_HH = 9); ¹³C NMR (65 MHz, CDCl₃): 153.86, 117.64, 113.15, 82.23, 79.65, 69.54, 31.62, 28.99, 28.85, 25.72, 22.44, 13.93; IR (KBr): 3265 (s), 2927 (s), 2932 (s), 2866 (s), 2105 (w), 1497 (s), 1275 (m). MS (ESI): 158 [M⁺– (C₂H₅)₂ + H₂], 354 (M⁺) m/z.

S3. Refinement

All non-H atoms were refined anisotropically. The H atoms were visible in electron density maps, but were placed in idealized positions and allowed to ride on their parent atoms at distances of 0.95 Å (aromatic and acetylinic), 0.98 Å (methyl) and 0.99 Å (methylene) with U_iso(H) of 1.2 times U_eq(C).

Computing details

For all compounds, data collection: Collect (Hooft, 1998); cell refinement: HKL SCALEPACK (Otwinowski & Minor, 1997); data reduction: HKL DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. An ORTEP-3 plot (Farrugia, 1997) of (I) (50% probability displacement ellipsoids).
	Fig. 2. The packing (Macrae et al., 2006) of (I)·For clarity, only the C—H···π interactions are shown.
	Fig. 3. An ORTEP-3 plot (Farrugia, 1997) of (II)(50% probability displacement ellipsoids).
	Fig. 4. The packing (Macrae et al., 2006) of (II),showing the in-plane interactions.
	Fig. 5. An ORTEP-3 plot (Farrugia, 1997) of (III) (50% probability displacement ellipsoids).
	Fig. 6. The packing (Macrae et al., 2006) of (III), showing the C—H···O interactions.

(I) 2,5-Diethoxy-1,4-bis[(trimethylsilyl)ethynyl]benzene

Crystal data

C20H30O2Si2	Z = 2
Mr = 358.62	F(000) = 388
Monoclinic, P21/c	Dx = 1.024 Mg m^−3
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 10.132 (1) Å	µ = 0.16 mm^−1
b = 9.887 (2) Å	T = 173 K
c = 12.169 (4) Å	Prism, colourless
β = 107.46 (2)°	0.25 × 0.2 × 0.15 mm
V = 1162.9 (5) Å^3

Data collection

Nonius KappaCCD diffractometer	Rint = 0.039
CCD rotation images, thick slices scans	θmax = 25.0°, θmin = 3.7°
9367 measured reflections	h = −12→12
2032 independent reflections	k = −11→11
1568 reflections with I > 2σ(I)	l = −14→12

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.048	w = 1/[σ^2(Fo^2) + (0.1372P)^2 + 1.7989P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.175	(Δ/σ)max < 0.001
S = 0.76	Δρmax = 0.21 e Å^−3
2032 reflections	Δρmin = −0.52 e Å^−3
113 parameters

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Si1	0.09344 (8)	0.40623 (7)	−0.25610 (6)	0.0386 (3)
O1	0.3962 (2)	−0.0057 (2)	−0.24102 (16)	0.0480 (6)
C1	0.2172 (3)	0.2749 (3)	−0.1776 (2)	0.0397 (6)
C2	0.3001 (3)	0.1920 (3)	−0.1246 (2)	0.0388 (6)
C3	0.4012 (3)	0.0942 (2)	−0.0618 (2)	0.0369 (6)
C4	0.5473 (3)	−0.1011 (3)	−0.0606 (2)	0.0388 (6)
H4	0.5797	−0.1701	−0.1004	0.047*
C5	0.4500 (3)	−0.0083 (3)	−0.1227 (2)	0.0378 (6)
C6	0.4329 (3)	−0.1148 (3)	−0.3058 (2)	0.0503 (8)
H6A	0.4041	−0.2027	−0.2815	0.06*
H6B	0.5342	−0.1167	−0.2921	0.06*
C7	0.3585 (4)	−0.0899 (4)	−0.4333 (3)	0.0644 (10)
H7A	0.2582	−0.0912	−0.4463	0.097*
H7B	0.3836	−0.161	−0.4795	0.097*
H7C	0.3859	−0.0017	−0.456	0.097*
C8	−0.0214 (4)	0.4469 (3)	−0.1647 (3)	0.0560 (8)
H8A	−0.0692	0.3646	−0.1526	0.084*
H8B	−0.0898	0.5149	−0.2038	0.084*
H8C	0.0348	0.4823	−0.0902	0.084*
C9	0.1951 (3)	0.5596 (3)	−0.2748 (3)	0.0500 (8)
H9A	0.2528	0.5907	−0.1992	0.075*
H9B	0.1311	0.6318	−0.3123	0.075*
H9C	0.2542	0.5359	−0.3226	0.075*
C10	−0.0067 (4)	0.3383 (4)	−0.4007 (3)	0.0705 (11)
H10A	0.0573	0.3136	−0.4438	0.106*
H10B	−0.0711	0.4075	−0.4433	0.106*
H10C	−0.0588	0.2581	−0.3906	0.106*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Si1	0.0506 (5)	0.0277 (4)	0.0322 (4)	0.0066 (3)	0.0048 (3)	0.0040 (3)
O1	0.0575 (13)	0.0509 (12)	0.0336 (10)	0.0183 (10)	0.0107 (9)	0.0026 (8)
C1	0.0505 (16)	0.0324 (13)	0.0347 (13)	0.0043 (12)	0.0103 (12)	0.0037 (11)
C2	0.0492 (16)	0.0315 (13)	0.0364 (14)	0.0035 (12)	0.0138 (12)	0.0032 (11)
C3	0.0443 (14)	0.0291 (13)	0.0376 (14)	0.0045 (11)	0.0127 (12)	0.0082 (10)
C4	0.0464 (15)	0.0334 (14)	0.0378 (14)	0.0060 (11)	0.0147 (12)	0.0030 (11)
C5	0.0452 (15)	0.0337 (14)	0.0347 (13)	0.0044 (11)	0.0125 (11)	0.0059 (11)
C6	0.0544 (18)	0.0551 (18)	0.0386 (16)	0.0086 (14)	0.0099 (13)	−0.0075 (13)
C7	0.066 (2)	0.086 (3)	0.0393 (17)	0.0170 (19)	0.0137 (16)	−0.0046 (16)
C8	0.0604 (19)	0.0397 (16)	0.072 (2)	0.0078 (15)	0.0252 (17)	0.0059 (15)
C9	0.066 (2)	0.0383 (15)	0.0457 (17)	0.0014 (14)	0.0174 (15)	0.0063 (13)
C10	0.098 (3)	0.0478 (19)	0.0456 (18)	−0.0036 (19)	−0.0087 (18)	0.0024 (15)

Geometric parameters (Å, º)

Si1—C1	1.858 (3)	C6—H6A	0.99
Si1—C10	1.872 (3)	C6—H6B	0.99
Si1—C8	1.878 (3)	C7—H7A	0.98
Si1—C9	1.885 (3)	C7—H7B	0.98
O1—C5	1.379 (3)	C7—H7C	0.98
O1—C6	1.449 (3)	C8—H8A	0.98
C1—C2	1.212 (4)	C8—H8B	0.98
C2—C3	1.449 (4)	C8—H8C	0.98
C3—C4^i	1.424 (4)	C9—H9A	0.98
C3—C5	1.428 (4)	C9—H9B	0.98
C4—C5	1.392 (4)	C9—H9C	0.98
C4—C3^i	1.424 (4)	C10—H10A	0.98
C4—H4	0.95	C10—H10B	0.98
C6—C7	1.528 (4)	C10—H10C	0.98
C1—Si1—C10	108.91 (15)	C6—C7—H7A	109.5
C1—Si1—C8	106.71 (14)	C6—C7—H7B	109.5
C10—Si1—C8	112.06 (19)	H7A—C7—H7B	109.5
C1—Si1—C9	108.38 (14)	C6—C7—H7C	109.5
C10—Si1—C9	109.69 (16)	H7A—C7—H7C	109.5
C8—Si1—C9	110.95 (15)	H7B—C7—H7C	109.5
C5—O1—C6	118.0 (2)	Si1—C8—H8A	109.5
C2—C1—Si1	178.2 (3)	Si1—C8—H8B	109.5
C1—C2—C3	178.9 (3)	H8A—C8—H8B	109.5
C4^i—C3—C5	120.1 (2)	Si1—C8—H8C	109.5
C4^i—C3—C2	119.9 (2)	H8A—C8—H8C	109.5
C5—C3—C2	120.0 (2)	H8B—C8—H8C	109.5
C5—C4—C3^i	120.9 (2)	Si1—C9—H9A	109.5
C5—C4—H4	119.6	Si1—C9—H9B	109.5
C3^i—C4—H4	119.6	H9A—C9—H9B	109.5
O1—C5—C4	124.9 (2)	Si1—C9—H9C	109.5
O1—C5—C3	116.1 (2)	H9A—C9—H9C	109.5
C4—C5—C3	119.0 (2)	H9B—C9—H9C	109.5
O1—C6—C7	107.7 (2)	Si1—C10—H10A	109.5
O1—C6—H6A	110.2	Si1—C10—H10B	109.5
C7—C6—H6A	110.2	H10A—C10—H10B	109.5
O1—C6—H6B	110.2	Si1—C10—H10C	109.5
C7—C6—H6B	110.2	H10A—C10—H10C	109.5
H6A—C6—H6B	108.5	H10B—C10—H10C	109.5
C6—O1—C5—C4	6.2 (4)	C2—C3—C5—O1	0.6 (4)
C6—O1—C5—C3	−174.4 (2)	C4^i—C3—C5—C4	0.5 (4)
C3^i—C4—C5—O1	178.8 (2)	C2—C3—C5—C4	180.0 (2)
C3^i—C4—C5—C3	−0.5 (4)	C5—O1—C6—C7	178.9 (3)
C4^i—C3—C5—O1	−178.9 (2)

Symmetry code: (i) −x+1, −y, −z.

(II) 2,5-Diethoxy-1,4-diethynylbenzene

Crystal data

C14H14O2	Z = 2
Mr = 214.25	F(000) = 228
Monoclinic, P21/c	Dx = 1.177 Mg m^−3
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 9.748 (2) Å	µ = 0.08 mm^−1
b = 8.890 (2) Å	T = 173 K
c = 7.566 (2) Å	Block, colourless
β = 112.74 (3)°	0.3 × 0.2 × 0.2 mm
V = 604.7 (3) Å^3

Data collection

Nonius KappaCCD diffractometer	Rint = 0.024
CCD rotation images, thick slices scans	θmax = 25.0°, θmin = 3.7°
4943 measured reflections	h = −11→10
1045 independent reflections	k = −9→10
910 reflections with I > 2σ(I)	l = −7→8

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.038	w = 1/[σ^2(Fo^2) + (0.0343P)^2 + 0.258P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.095	(Δ/σ)max < 0.001
S = 1.07	Δρmax = 0.14 e Å^−3
1045 reflections	Δρmin = −0.19 e Å^−3
74 parameters

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.21490 (11)	0.20584 (11)	0.21994 (14)	0.0314 (3)
C1	0.38489 (18)	−0.13769 (18)	0.4200 (2)	0.0430 (4)
H1	0.4739	−0.1709	0.5195	0.052*
C2	0.27296 (16)	−0.09599 (16)	0.2948 (2)	0.0321 (4)
C3	0.13512 (15)	−0.04637 (16)	0.14445 (19)	0.0265 (3)
C4	0.02968 (15)	−0.15371 (16)	0.03503 (19)	0.0279 (4)
H4	0.0505	−0.2578	0.0589	0.033*
C5	0.10497 (15)	0.10871 (16)	0.10794 (19)	0.0259 (3)
C6	0.19286 (16)	0.36579 (15)	0.1785 (2)	0.0297 (4)
H6A	0.102	0.4011	0.1945	0.036*
H6B	0.1822	0.3863	0.0452	0.036*
C7	0.32904 (17)	0.44534 (18)	0.3193 (2)	0.0375 (4)
H7A	0.3411	0.4199	0.4505	0.056*
H7B	0.3165	0.5543	0.3007	0.056*
H7C	0.4174	0.4132	0.2976	0.056*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0307 (6)	0.0224 (5)	0.0325 (6)	−0.0064 (4)	0.0029 (4)	−0.0030 (4)
C1	0.0368 (9)	0.0312 (9)	0.0441 (10)	0.0007 (7)	−0.0030 (8)	−0.0029 (7)
C2	0.0323 (8)	0.0234 (7)	0.0358 (8)	−0.0040 (6)	0.0079 (7)	−0.0044 (6)
C3	0.0254 (7)	0.0259 (8)	0.0262 (7)	−0.0030 (6)	0.0078 (6)	−0.0018 (6)
C4	0.0297 (8)	0.0216 (7)	0.0296 (8)	−0.0021 (6)	0.0085 (6)	−0.0011 (6)
C5	0.0261 (7)	0.0249 (7)	0.0254 (7)	−0.0071 (5)	0.0085 (6)	−0.0049 (5)
C6	0.0322 (8)	0.0228 (8)	0.0315 (8)	−0.0041 (6)	0.0095 (6)	−0.0023 (6)
C7	0.0358 (8)	0.0273 (8)	0.0437 (9)	−0.0083 (6)	0.0092 (7)	−0.0064 (6)

Geometric parameters (Å, º)

O1—C5	1.3820 (16)	C4—H4	0.95
O1—C6	1.4541 (17)	C5—C4^i	1.398 (2)
C1—C2	1.194 (2)	C6—C7	1.518 (2)
C1—H1	0.95	C6—H6A	0.99
C2—C3	1.454 (2)	C6—H6B	0.99
C3—C4	1.412 (2)	C7—H7A	0.98
C3—C5	1.414 (2)	C7—H7B	0.98
C4—C5^i	1.398 (2)	C7—H7C	0.98
C5—O1—C6	117.64 (11)	O1—C6—C7	106.75 (12)
C2—C1—H1	180	O1—C6—H6A	110.4
C1—C2—C3	178.93 (17)	C7—C6—H6A	110.4
C4—C3—C5	119.67 (12)	O1—C6—H6B	110.4
C4—C3—C2	119.80 (13)	C7—C6—H6B	110.4
C5—C3—C2	120.54 (12)	H6A—C6—H6B	108.6
C5^i—C4—C3	120.86 (13)	C6—C7—H7A	109.5
C5^i—C4—H4	119.6	C6—C7—H7B	109.5
C3—C4—H4	119.6	H7A—C7—H7B	109.5
O1—C5—C4^i	124.68 (13)	C6—C7—H7C	109.5
O1—C5—C3	115.84 (12)	H7A—C7—H7C	109.5
C4^i—C5—C3	119.47 (12)	H7B—C7—H7C	109.5
C5—C3—C4—C5^i	−0.6 (2)	C2—C3—C5—O1	1.41 (19)
C2—C3—C4—C5^i	178.77 (13)	C4—C3—C5—C4^i	0.6 (2)
C6—O1—C5—C4^i	−3.9 (2)	C2—C3—C5—C4^i	−178.77 (13)
C6—O1—C5—C3	175.96 (12)	C5—O1—C6—C7	−179.40 (12)
C4—C3—C5—O1	−179.22 (12)

Symmetry code: (i) −x, −y, −z.

(III) 1,4-Diethynyl-2,5-bis(heptyloxy)benzene

Crystal data

C24H34O2	F(000) = 388
Mr = 354.51	Dx = 1.075 Mg m^−3
Monoclinic, P21/a	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yab	Cell parameters from 8991 reflections
a = 6.7246 (2) Å	θ = 2.9–27.9°
b = 16.7456 (5) Å	µ = 0.07 mm^−1
c = 9.8026 (3) Å	T = 173 K
β = 97.320 (2)°	Prism, colourless
V = 1094.85 (6) Å^3	0.6 × 0.5 × 0.4 mm
Z = 2

Data collection

Nonius KappaCCD diffractometer	Rint = 0.026
CCD rotation images, thick slices scans	θmax = 25.0°, θmin = 3.2°
3729 measured reflections	h = −7→7
1920 independent reflections	k = −19→19
1458 reflections with I > 2σ(I)	l = −11→11

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.044	w = 1/[σ^2(Fo^2) + (0.0396P)^2 + 0.355P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.107	(Δ/σ)max < 0.001
S = 0.99	Δρmax = 0.10 e Å^−3
1920 reflections	Δρmin = −0.18 e Å^−3
119 parameters

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.22444 (16)	0.59123 (6)	0.19897 (12)	0.0447 (3)
C1	−0.2060 (3)	0.71184 (10)	0.11340 (19)	0.0489 (4)
H1	−0.258	0.762	0.137	0.059*
C2	−0.1414 (2)	0.64950 (9)	0.08414 (17)	0.0400 (4)
C3	−0.0684 (2)	0.57332 (9)	0.04310 (16)	0.0378 (4)
C4	−0.1849 (2)	0.52880 (9)	−0.05744 (16)	0.0396 (4)
H4	−0.3116	0.5488	−0.0966	0.047*
C5	0.1185 (2)	0.54417 (9)	0.10110 (16)	0.0378 (4)
C6	0.4182 (2)	0.56259 (10)	0.25708 (17)	0.0440 (4)
H6A	0.5073	0.5584	0.1844	0.053*
H6B	0.4053	0.5089	0.2972	0.053*
C7	0.5066 (2)	0.61981 (10)	0.36713 (18)	0.0450 (4)
H7A	0.4149	0.6249	0.438	0.054*
H7B	0.5213	0.6732	0.3261	0.054*
C8	0.7103 (2)	0.59062 (10)	0.43384 (17)	0.0451 (4)
H8A	0.695	0.5363	0.471	0.054*
H8B	0.8017	0.5868	0.3625	0.054*
C9	0.8053 (3)	0.64423 (10)	0.54912 (18)	0.0462 (4)
H9A	0.8224	0.6983	0.5116	0.055*
H9B	0.7129	0.6487	0.6197	0.055*
C10	1.0073 (2)	0.61477 (10)	0.61750 (17)	0.0449 (4)
H10A	0.9906	0.5603	0.6535	0.054*
H10B	1.1003	0.6112	0.5471	0.054*
C11	1.1015 (3)	0.66726 (10)	0.73425 (18)	0.0474 (4)
H11A	1.0086	0.6712	0.8046	0.057*
H11B	1.1201	0.7217	0.6984	0.057*
C12	1.3033 (3)	0.63598 (12)	0.80199 (19)	0.0564 (5)
H12A	1.2857	0.5825	0.8394	0.085*
H12B	1.3565	0.672	0.8766	0.085*
H12C	1.3973	0.6333	0.7335	0.085*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0424 (7)	0.0353 (6)	0.0564 (7)	0.0031 (5)	0.0065 (5)	−0.0027 (5)
C1	0.0466 (10)	0.0371 (9)	0.0642 (12)	0.0030 (8)	0.0123 (8)	−0.0027 (8)
C2	0.0370 (9)	0.0364 (9)	0.0488 (10)	−0.0005 (7)	0.0134 (7)	0.0042 (7)
C3	0.0413 (9)	0.0290 (8)	0.0459 (9)	0.0007 (7)	0.0161 (7)	0.0058 (7)
C4	0.0395 (9)	0.0324 (8)	0.0487 (10)	0.0027 (7)	0.0129 (7)	0.0074 (7)
C5	0.0386 (9)	0.0312 (8)	0.0457 (9)	−0.0015 (7)	0.0140 (7)	0.0048 (7)
C6	0.0412 (9)	0.0399 (9)	0.0526 (10)	0.0045 (7)	0.0120 (8)	0.0033 (8)
C7	0.0449 (10)	0.0401 (9)	0.0520 (10)	0.0023 (8)	0.0135 (8)	0.0002 (8)
C8	0.0480 (10)	0.0417 (9)	0.0471 (10)	0.0045 (8)	0.0123 (8)	0.0015 (8)
C9	0.0492 (10)	0.0390 (9)	0.0525 (11)	0.0023 (8)	0.0150 (8)	−0.0001 (8)
C10	0.0463 (10)	0.0431 (9)	0.0473 (10)	0.0028 (8)	0.0136 (8)	0.0022 (8)
C11	0.0564 (11)	0.0378 (9)	0.0498 (10)	−0.0031 (8)	0.0133 (8)	0.0052 (8)
C12	0.0564 (12)	0.0599 (12)	0.0531 (11)	−0.0043 (9)	0.0079 (9)	0.0040 (9)

Geometric parameters (Å, º)

O1—C5	1.369 (2)	C8—C9	1.519 (2)
O1—C6	1.436 (2)	C8—H8A	0.99
C1—C2	1.180 (2)	C8—H8B	0.99
C1—H1	0.95	C9—C10	1.519 (2)
C2—C3	1.442 (2)	C9—H9A	0.99
C3—C4	1.394 (2)	C9—H9B	0.99
C3—C5	1.399 (2)	C10—C11	1.516 (2)
C4—C5^i	1.387 (2)	C10—H10A	0.99
C4—H4	0.95	C10—H10B	0.99
C5—C4^i	1.387 (2)	C11—C12	1.525 (2)
C6—C7	1.507 (2)	C11—H11A	0.99
C6—H6A	0.99	C11—H11B	0.99
C6—H6B	0.99	C12—H12A	0.98
C7—C8	1.522 (2)	C12—H12B	0.98
C7—H7A	0.99	C12—H12C	0.98
C7—H7B	0.99
C5—O1—C6	116.78 (12)	C9—C8—H8B	108.8
C2—C1—H1	180	C7—C8—H8B	108.8
C1—C2—C3	177.56 (19)	H8A—C8—H8B	107.7
C4—C3—C5	119.69 (14)	C10—C9—C8	113.85 (14)
C4—C3—C2	119.30 (14)	C10—C9—H9A	108.8
C5—C3—C2	121.00 (15)	C8—C9—H9A	108.8
C5^i—C4—C3	121.01 (15)	C10—C9—H9B	108.8
C5^i—C4—H4	119.5	C8—C9—H9B	108.8
C3—C4—H4	119.5	H9A—C9—H9B	107.7
O1—C5—C4^i	124.33 (15)	C11—C10—C9	114.15 (14)
O1—C5—C3	116.36 (13)	C11—C10—H10A	108.7
C4^i—C5—C3	119.31 (15)	C9—C10—H10A	108.7
O1—C6—C7	109.07 (13)	C11—C10—H10B	108.7
O1—C6—H6A	109.9	C9—C10—H10B	108.7
C7—C6—H6A	109.9	H10A—C10—H10B	107.6
O1—C6—H6B	109.9	C10—C11—C12	113.10 (15)
C7—C6—H6B	109.9	C10—C11—H11A	109
H6A—C6—H6B	108.3	C12—C11—H11A	109
C6—C7—C8	110.78 (13)	C10—C11—H11B	109
C6—C7—H7A	109.5	C12—C11—H11B	109
C8—C7—H7A	109.5	H11A—C11—H11B	107.8
C6—C7—H7B	109.5	C11—C12—H12A	109.5
C8—C7—H7B	109.5	C11—C12—H12B	109.5
H7A—C7—H7B	108.1	H12A—C12—H12B	109.5
C9—C8—C7	113.59 (14)	C11—C12—H12C	109.5
C9—C8—H8A	108.8	H12A—C12—H12C	109.5
C7—C8—H8A	108.8	H12B—C12—H12C	109.5
C5—C3—C4—C5^i	0.0 (2)	C2—C3—C5—C4^i	−179.02 (14)
C2—C3—C4—C5^i	179.04 (14)	C5—O1—C6—C7	−177.11 (13)
C6—O1—C5—C4^i	1.1 (2)	O1—C6—C7—C8	178.67 (13)
C6—O1—C5—C3	−178.76 (13)	C6—C7—C8—C9	−178.17 (14)
C4—C3—C5—O1	179.89 (13)	C7—C8—C9—C10	179.16 (14)
C2—C3—C5—O1	0.9 (2)	C8—C9—C10—C11	−179.03 (14)
C4—C3—C5—C4^i	0.0 (2)	C9—C10—C11—C12	179.48 (14)

Symmetry code: (i) −x, −y+1, −z.