An irreversible phase transition in 1-n-butyl­indeno­[2,1-c]pyran-3,9-dione

At ambient temperature, the title compound, C₁₆H₁₄O₃, is triclinic, with the n-butyl side chain disordered in an out-of-plane orientation. On cooling below 240 K, it converts into a different triclinic phase with an ordered planar conformation and denser packing, which is retained on warming to room temperature. The transition (occasionally) proceeds from single crystal to single crystal.

S1. Comment

In recent decades, crystal-to-crystal transformations, both physical and chemical, of organic and organometallic compounds have moved from being a crystallographic curiosity (Morawetz et al., 1963) to a focus of intense theoretical and applied interest (Dunitz, 1995; Gavezzotti & Filippini, 1995; Braga & Grepioni, 2005; Garcia-Garibay, 2007). Important aspects of the mechanism are still in dispute (Mnyukh, 2001; Herbstein, 2006; Merz et al., 2009), hence the significance of closely investigating new examples of these transformations. The titl compound, (I), which was obtained during our studies of palladium(II)-catalysed electrophilic cyclization of electron-deficient enynes (Wu et al., 2012), presents such an example.

Crystals of the α-polymorph of (I) were grown at room temperature by diffusion of n-hexane into an Et₂O solution of (I). The structure is triclinic. The indeno[2,1-c]pyran-3,9-dione (ipd) system is planar and the n-butyl side-chain is disordered between two alternative conformations, viz. all-trans (A) and trans–gauche (B), with occupancies of 0.720 (4) and 0.280 (4), respectively. For the major conformation, atoms C12, C13, C14A, C15A and C16A are practically coplanar; their mean plane is inclined to the ipd plane by 60.7° (Fig. 1). For the minor conformation, the mean plane formed by atoms C12, C13, C14B and C15B is practically perpendicular to the ipd plane (interplanar angle = 89.0°), while the plane formed by atoms C14B, C15B and C16B is inclined to the latter by 31.6°. However, the mean vector of the C12–C16 chain has a similar direction in both cases, which differ by 6.6° and are inclined to the ipd plane by 26.3° for the major conformation and by 22.7° for the minor conformation.

The phase transition occurs on cooling below ca 240 K. It usually results in fracturing of the crystal, and always in its violent swinging on the mount, even when glued apparently rigidly with epoxy resin. On one occasion, after slow cooling (at a rate of 10 K h^-1 near the transition) with periodic annealing, a fragment of a fractured crystal which remained on the mount was found to be a single crystal of X-ray quality of the new β-polymorph, also triclinic. This crystal was cooled to 120 K and a full data set was collected. The same crystal was then warmed to room temperature without any further phase transformation being observed, and a second data set was collected at 293 K. The structures of β-(I) determined at 120 and 293 K are essentially identical. The side-chain is ordered in an all-trans conformation, in this case practically coplanar with the ipd system (Fig. 1). At room temperature, β-(I) has a packing coefficient [calculated according to Gavezzotti (1983)] of 0.645, compared with a value of 0.615 for polymorph α-(I), and a correspondingly higher density (1.337 versus 1.276 Mg m^-3). The thermal expansion coefficient of β-(I), 1.05 (3) × 10^-4, is of the usual order of magnitude (Hofmann, 2002).

The crystal packing of polymorphs α-(I) and β-(I) is compared in Figs. 2 and 3. In both structures, molecules related via the a–b translation are practically coplanar, entirely for β-(I) or just as far as the ipd system is concerned in α-(I). In β-(I), the resulting planar ribbons form a slightly puckered layer (Fig. 3), whereas in α-(I) two adjacent ribbons are coplanar, but the next pair is shifted relative to them along the stacking direction. In both polymorphs, aromatic and aliphatic systems are segregated, which gives some leeway for the conformational realignment of the side-chains. However, the phase transition cannot be interpreted purely in terms of side-chains moving between stationary aromatic stacks, as there is also a very substantial shear between the aromatic systems. In fact, the layered appearance of the structures is somewhat deceptive. Although the mean interlayer separations are rather short [3.32 Å in α-(I) and 3.30 Å in β-(I) at 120 K], in neither structure is it possible to distinguish any meaningful stacks; only some fringe overlap between the aromatic systems of neighbouring layers is observed.

The absence of any rational relation between the unit cells of the two polymorphs, as well as the large intermolecular shifts required, suggest that the phase transition may be reconstructive (Mnyukh, 2001) rather than topotactic (Morawetz et al., 1963) and proceed through the usual process of nucleation and growth (Herbstein, 2006).

The crystal data of polymorph β-(I) at 120 K are reported without comment by Wu et al. (2012) [deposited in the Cambridge Structural Database (Allen, 2002) as deposition number CCDC-852796].

Related literature

For related literature, see: Allen (2002); Braga & Grepioni (2005); Dunitz (1995); Garcia-Garibay (2007); Gavezzotti (1983); Gavezzotti & Filippini (1995); Herbstein (2006); Hofmann (2002); Merz et al. (2009); Mnyukh (2001); Morawetz et al. (1963); Wu et al. (2012).

S2. Experimental

The synthesis of (I) is described by Wu et al. (2012). o-EtO₂CC═CC₆H₄C(═O)C≡CBu-n (0.15 mmol) was added to a solution of Pd(OAc)₂ (10 mol%) and LiCl (4 equivalents) in acetic acid (3 ml). The mixture was stirred at 333 K in air until all the enyne was consumed (as monitored by gas chromatographic mass spectroscopy, GC–MS), then cooled and the solvent removed in vacuo. The residue was purified by flash chromatography to give (I). X-ray quality crystals of polymorph α-(I) were grown by solvent diffusion: a diethyl ether solution of (I) was placed in an open 10 ml vial within a closed 50 ml vial containing n-hexane.

S3. Refinement

Methyl groups were refined as rigid bodies rotating around the C—C bonds, with C—H = 0.98 Å. All other H atoms were treated as riding in idealized positions, with Csp²—H = 0.93 and Csp³—H = 0.97 Å at 293 K, and 0.95 and 0.99 Å, respectively, at 120 K. The U_iso(H) values for the methyl H atoms in β-(I) were refined, while in α-(I) they were constrained to 1.5U_eq(C), or 1.2U_eq(C) for non-methyl H atoms.

Computing details

Data collection: SMART (Bruker, 2001) for aI, bI; SMART (Bruker, 2003) for bIRT. For all compounds, cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

Figures

	Fig. 1. The molecular structure of (I) in (a) the α-polymorph at 293 K (dashed outlines indicate the minor disordered component?) and (b) the β-polymorph at 120 K. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. The molecular layers in (a) α-(I) (disorder omitted) and (b) β-(I).
	Fig. 3. The crystal packing of (a) α-(I) and (b) β-(I), viewed along the direction of the a–b translation [Revised text OK?] (indicated by the arrows in Fig. 2). Dashed boxes enclose the layers shown in Fig. 2.

(aI) 1-n-Butylindeno[2,1-c]pyran-3,9-dione

Crystal data

C16H14O3	F(000) = 268
Mr = 254.27	Dx = 1.276 Mg m^−3
Triclinic, P1	Melting point: 373.7(5) K
a = 4.6539 (6) Å	Mo Kα radiation, λ = 0.71073 Å
b = 10.1800 (12) Å	Cell parameters from 1209 reflections
c = 14.3718 (17) Å	θ = 2.4–21.9°
α = 82.481 (5)°	µ = 0.09 mm^−1
β = 88.127 (7)°	T = 293 K
γ = 78.604 (6)°	Plate, colourless
V = 661.71 (14) Å^3	0.22 × 0.18 × 0.06 mm
Z = 2

Data collection

Bruker SMART CCD 6000 area-detector diffractometer	1137 reflections with I > 2σ(I)
Radiation source: sealed X-ray tube	Rint = 0.063
Graphite monochromator	θmax = 25.0°, θmin = 1.4°
Detector resolution: 5.6 pixels mm^-1	h = −5→5
ω scans	k = −12→12
5329 measured reflections	l = −16→17
2336 independent reflections

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)] = 0.041	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.110	H-atom parameters constrained
S = 0.84	w = 1/[σ^2(Fo^2) + (0.0525P)^2] where P = (Fo^2 + 2Fc^2)/3
2336 reflections	(Δ/σ)max < 0.001
185 parameters	Δρmax = 0.10 e Å^−3
15 restraints	Δρmin = −0.14 e Å^−3

Special details

Experimental. The data collection nominally covered a full sphere of reciprocal space by a combination of 3 sets of ω scans each set at different φ angles and each scan (20 s exposure) covering -0.3° in ω. The crystal-to-detector distance was 4.83 cm. Phase transition occurs on cooling below 240 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. Methyl groups were refined as rigid bodies rotating around C—C bonds. Other H atoms: riding in idealized positions. The C14H₂C15H₂C16H₃ chain is disordered between two conformations, A and B, with occupancies refined to 0.719 (4) and 0.281 (4), respectively.

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
O1	0.3523 (3)	0.63740 (14)	0.18082 (11)	0.0659 (4)
O2	0.0149 (4)	0.66916 (15)	0.07167 (11)	0.0808 (5)
O3	1.0635 (4)	0.33233 (18)	0.32844 (13)	0.0944 (6)
C1	0.2122 (5)	0.5888 (2)	0.11157 (16)	0.0613 (6)
C2	0.3168 (4)	0.4515 (2)	0.09622 (15)	0.0605 (6)
H2	0.2333	0.4150	0.0502	0.073*
C3	0.5361 (4)	0.3755 (2)	0.14912 (15)	0.0553 (6)
C4	0.6816 (5)	0.2336 (2)	0.15088 (16)	0.0614 (6)
C5	0.6375 (6)	0.1373 (2)	0.09593 (19)	0.0799 (7)
H5	0.4982	0.1580	0.0485	0.096*
C6	0.8076 (7)	0.0090 (3)	0.1137 (2)	0.0988 (9)
H6	0.7813	−0.0574	0.0779	0.119*
C7	1.0139 (7)	−0.0220 (3)	0.1830 (3)	0.1012 (10)
H7	1.1254	−0.1090	0.1930	0.121*
C8	1.0608 (6)	0.0730 (3)	0.2379 (2)	0.0909 (8)
H8	1.2000	0.0510	0.2853	0.109*
C9	0.8918 (5)	0.2016 (2)	0.22028 (17)	0.0677 (6)
C10	0.8990 (5)	0.3235 (2)	0.26654 (18)	0.0681 (6)
C11	0.6686 (4)	0.4301 (2)	0.21968 (15)	0.0552 (6)
C12	0.5754 (4)	0.5593 (2)	0.23414 (16)	0.0598 (6)
C13	0.6839 (5)	0.6342 (2)	0.30300 (17)	0.0765 (7)
H133	0.6784	0.7272	0.2762	0.092*	0.281 (4)
H134	0.8847	0.5931	0.3200	0.092*	0.281 (4)
H131	0.7652	0.7070	0.2684	0.092*	0.719 (4)
H132	0.8433	0.5735	0.3376	0.092*	0.719 (4)
C14A	0.4626 (7)	0.6900 (4)	0.3742 (2)	0.0757 (12)	0.719 (4)
H141	0.3919	0.6172	0.4127	0.091*	0.719 (4)
H142	0.2963	0.7466	0.3405	0.091*	0.719 (4)
C15A	0.5944 (8)	0.7680 (6)	0.4391 (3)	0.0920 (15)	0.719 (4)
H151	0.7571	0.7075	0.4721	0.110*	0.719 (4)
H152	0.6705	0.8404	0.4020	0.110*	0.719 (4)
C16A	0.3720 (10)	0.8233 (5)	0.5098 (3)	0.1216 (19)	0.719 (4)
H161	0.2142	0.8916	0.4823	0.182*	0.719 (4)
H162	0.4632	0.8585	0.5576	0.182*	0.719 (4)
H163	0.2961	0.7459	0.5375	0.182*	0.719 (4)
C14B	0.501 (2)	0.6185 (11)	0.3917 (4)	0.0757 (12)	0.281 (4)
H143	0.4911	0.5248	0.4124	0.091*	0.281 (4)
H144	0.3045	0.6656	0.3736	0.091*	0.281 (4)
C15B	0.570 (3)	0.6772 (10)	0.4781 (7)	0.0920 (15)	0.281 (4)
H153	0.4297	0.6567	0.5265	0.110*	0.281 (4)
H154	0.7645	0.6354	0.5013	0.110*	0.281 (4)
C16B	0.537 (4)	0.8293 (11)	0.4678 (15)	0.147 (7)*	0.281 (4)
H164	0.6907	0.8560	0.4279	0.220*	0.281 (4)
H165	0.5503	0.8576	0.5285	0.220*	0.281 (4)
H166	0.3505	0.8708	0.4407	0.220*	0.281 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0630 (9)	0.0575 (9)	0.0773 (11)	−0.0027 (8)	−0.0093 (8)	−0.0207 (8)
O2	0.0874 (11)	0.0648 (11)	0.0820 (12)	0.0083 (9)	−0.0221 (10)	−0.0095 (9)
O3	0.0820 (12)	0.1039 (13)	0.0927 (14)	−0.0030 (10)	−0.0290 (11)	−0.0117 (11)
C1	0.0664 (15)	0.0596 (15)	0.0572 (15)	−0.0072 (13)	−0.0026 (12)	−0.0116 (12)
C2	0.0702 (14)	0.0562 (14)	0.0561 (14)	−0.0095 (12)	−0.0045 (12)	−0.0138 (12)
C3	0.0576 (13)	0.0526 (13)	0.0555 (14)	−0.0098 (11)	0.0046 (12)	−0.0085 (11)
C4	0.0665 (15)	0.0519 (14)	0.0650 (16)	−0.0088 (12)	0.0083 (13)	−0.0106 (12)
C5	0.0925 (18)	0.0610 (16)	0.0875 (19)	−0.0121 (14)	0.0057 (15)	−0.0202 (14)
C6	0.111 (2)	0.0602 (18)	0.125 (3)	−0.0116 (17)	0.022 (2)	−0.0265 (17)
C7	0.102 (2)	0.0570 (18)	0.134 (3)	0.0024 (16)	0.017 (2)	−0.0070 (19)
C8	0.0825 (18)	0.0688 (18)	0.108 (2)	0.0075 (15)	−0.0015 (16)	0.0048 (16)
C9	0.0661 (14)	0.0552 (15)	0.0766 (17)	−0.0044 (12)	0.0069 (13)	−0.0029 (13)
C10	0.0596 (15)	0.0760 (16)	0.0660 (17)	−0.0092 (13)	−0.0048 (13)	−0.0039 (14)
C11	0.0526 (12)	0.0551 (14)	0.0573 (14)	−0.0069 (11)	−0.0002 (11)	−0.0111 (11)
C12	0.0497 (12)	0.0667 (15)	0.0656 (16)	−0.0122 (12)	−0.0019 (12)	−0.0162 (13)
C13	0.0616 (14)	0.0807 (16)	0.0917 (19)	−0.0108 (13)	−0.0077 (14)	−0.0307 (15)
C14A	0.0694 (19)	0.081 (3)	0.077 (2)	0.001 (2)	−0.0139 (17)	−0.035 (2)
C15A	0.081 (2)	0.126 (4)	0.082 (3)	−0.030 (3)	−0.005 (2)	−0.042 (3)
C16A	0.109 (3)	0.180 (5)	0.097 (3)	−0.047 (3)	0.015 (3)	−0.070 (3)
C14B	0.0694 (19)	0.081 (3)	0.077 (2)	0.001 (2)	−0.0139 (17)	−0.035 (2)
C15B	0.081 (2)	0.126 (4)	0.082 (3)	−0.030 (3)	−0.005 (2)	−0.042 (3)

Geometric parameters (Å, º)

O1—C12	1.365 (2)	C13—C14B	1.518 (4)
O1—C1	1.400 (2)	C13—H133	0.9699
O2—C1	1.206 (2)	C13—H134	0.9703
O3—C10	1.216 (3)	C13—H131	0.9699
C1—C2	1.430 (3)	C13—H132	0.9703
C2—C3	1.343 (3)	C14A—C15A	1.517 (3)
C2—H2	0.9301	C14A—H141	0.9700
C3—C11	1.429 (3)	C14A—H142	0.9701
C3—C4	1.467 (3)	C15A—C16A	1.508 (4)
C4—C9	1.382 (3)	C15A—H151	0.9702
C4—C5	1.386 (3)	C15A—H152	0.9700
C5—C6	1.383 (3)	C16A—H161	0.9613
C5—H5	0.9302	C16A—H162	0.9612
C6—C7	1.369 (4)	C16A—H163	0.9608
C6—H6	0.9300	C14B—C15B	1.517 (4)
C7—C8	1.379 (4)	C14B—H143	0.9701
C7—H7	0.9301	C14B—H144	0.9701
C8—C9	1.384 (3)	C15B—C16B	1.514 (4)
C8—H8	0.9302	C15B—H153	0.9702
C9—C10	1.489 (3)	C15B—H154	0.9701
C10—C11	1.475 (3)	C16B—H164	0.9600
C11—C12	1.342 (3)	C16B—H165	0.9600
C12—C13	1.483 (3)	C16B—H166	0.9600
C13—C14A	1.510 (3)
C12—O1—C1	123.03 (17)	C12—C13—H134	110.2
O2—C1—O1	115.3 (2)	C14A—C13—H134	122.0
O2—C1—C2	127.6 (2)	C14B—C13—H134	106.6
O1—C1—C2	117.1 (2)	H133—C13—H134	108.5
C3—C2—C1	119.4 (2)	C12—C13—H131	108.1
C3—C2—H2	120.3	C14A—C13—H131	109.7
C1—C2—H2	120.3	C12—C13—H132	108.1
C2—C3—C11	121.07 (19)	C14A—C13—H132	107.3
C2—C3—C4	131.5 (2)	H131—C13—H132	107.3
C11—C3—C4	107.45 (19)	C13—C14A—C15A	111.6 (3)
C9—C4—C5	120.5 (2)	C13—C14A—H141	110.4
C9—C4—C3	109.2 (2)	C15A—C14A—H141	107.7
C5—C4—C3	130.3 (2)	C13—C14A—H142	108.2
C6—C5—C4	117.8 (3)	C15A—C14A—H142	111.2
C6—C5—H5	120.9	H141—C14A—H142	107.7
C4—C5—H5	121.2	C13—C14A—H144	114.7
C7—C6—C5	121.3 (3)	C16A—C15A—C14A	111.3 (3)
C7—C6—H6	119.4	C16A—C15A—H151	109.0
C5—C6—H6	119.4	C14A—C15A—H151	108.6
C6—C7—C8	121.5 (3)	C16A—C15A—H152	110.6
C6—C7—H7	119.2	C14A—C15A—H152	109.3
C8—C7—H7	119.3	H151—C15A—H152	108.0
C7—C8—C9	117.5 (3)	C15B—C14B—C13	120.1 (8)
C7—C8—H8	121.1	C15B—C14B—H143	106.2
C9—C8—H8	121.4	C13—C14B—H143	112.3
C4—C9—C8	121.4 (2)	C15B—C14B—H144	105.3
C4—C9—C10	109.5 (2)	C13—C14B—H144	104.7
C8—C9—C10	129.1 (2)	H143—C14B—H144	107.5
O3—C10—C11	128.1 (2)	C16B—C15B—C14B	116.0 (12)
O3—C10—C9	126.9 (2)	C16B—C15B—H153	104.8
C11—C10—C9	105.0 (2)	C14B—C15B—H153	107.4
C12—C11—C3	120.3 (2)	C16B—C15B—H154	109.4
C12—C11—C10	130.9 (2)	C14B—C15B—H154	111.0
C3—C11—C10	108.85 (19)	H153—C15B—H154	107.7
C11—C12—O1	119.1 (2)	C15B—C16B—H161	108.5
C11—C12—C13	128.4 (2)	C15B—C16B—H164	109.5
O1—C12—C13	112.44 (19)	C15B—C16B—H165	109.5
C12—C13—C14A	116.1 (2)	H164—C16B—H165	109.5
C12—C13—C14B	107.2 (4)	C15B—C16B—H166	109.5
C12—C13—H133	110.1	H164—C16B—H166	109.5
C14A—C13—H133	86.7	H165—C16B—H166	109.5
C14B—C13—H133	114.2
C11—C12—C13—C14A	−119.6 (3)	C11—C12—C13—C14B	−91.3 (5)
C12—C13—C14A—C15A	−178.3 (3)	C12—C13—C14B—C15B	176.4 (8)
C13—C14A—C15A—C16A	180.0 (5)	C13—C14B—C15B—C16B	63.1 (17)

(bI) 1-n-Butylindeno[2,1-c]pyran-3,9-dione

Crystal data

C16H14O3	F(000) = 268
Mr = 254.27	Dx = 1.387 Mg m^−3
Triclinic, P1	Melting point: 373.7(5) K
a = 5.3708 (2) Å	Mo Kα radiation, λ = 0.71073 Å
b = 7.2029 (3) Å	Cell parameters from 1676 reflections
c = 16.9507 (8) Å	θ = 2.4–29.8°
α = 96.461 (2)°	µ = 0.10 mm^−1
β = 93.246 (2)°	T = 120 K
γ = 110.029 (2)°	Irregular, colourless
V = 608.98 (4) Å^3	0.30 × 0.12 × 0.10 mm
Z = 2

Data collection

Bruker SMART CCD 6000 area-detector diffractometer	1491 reflections with I > 2σ(I)
Radiation source: sealed X-ray tube	Rint = 0.047
Graphite monochromator	θmax = 25.0°, θmin = 1.2°
Detector resolution: 5.6 pixels mm^-1	h = −6→6
ω scans	k = −8→8
5759 measured reflections	l = −20→20
2151 independent reflections

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)] = 0.037	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.091	H-atom parameters constrained
S = 0.96	w = 1/[σ^2(Fo^2) + (0.0452P)^2] where P = (Fo^2 + 2Fc^2)/3
2151 reflections	(Δ/σ)max < 0.001
174 parameters	Δρmax = 0.18 e Å^−3
0 restraints	Δρmin = −0.21 e Å^−3

Special details

Experimental. The data collection nominally covered a full sphere of reciprocal space by a combination of 4 sets of ω scans each set at different φ and/or 2θ angles and each scan (20 s exposure) covering -0.3° in ω. The crystal to detector distance was 4.84 cm.

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.

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

	x	y	z	Uiso*/Ueq
O1	0.3331 (2)	0.67093 (18)	0.29843 (7)	0.0236 (3)
O2	0.5366 (2)	0.71270 (19)	0.42052 (7)	0.0289 (3)
O3	−0.2151 (2)	0.86789 (19)	0.14982 (7)	0.0275 (3)
C1	0.3900 (4)	0.7650 (3)	0.37911 (10)	0.0231 (4)
C2	0.2712 (3)	0.9115 (3)	0.40094 (10)	0.0231 (4)
H2	0.3046	0.9803	0.4538	0.028*
C3	0.1122 (3)	0.9510 (3)	0.34607 (10)	0.0206 (4)
C4	−0.0241 (3)	1.0975 (3)	0.35064 (10)	0.0208 (4)
C5	−0.0283 (4)	1.2378 (3)	0.41299 (11)	0.0252 (4)
H5	0.0681	1.2520	0.4634	0.030*
C6	−0.1772 (4)	1.3568 (3)	0.39975 (11)	0.0270 (5)
H6	−0.1855	1.4520	0.4422	0.032*
C7	−0.3154 (4)	1.3399 (3)	0.32539 (11)	0.0257 (5)
H7	−0.4145	1.4244	0.3178	0.031*
C8	−0.3092 (4)	1.2009 (3)	0.26266 (11)	0.0237 (4)
H8	−0.4023	1.1890	0.2119	0.028*
C9	−0.1631 (3)	1.0795 (3)	0.27606 (10)	0.0202 (4)
C10	−0.1218 (3)	0.9212 (3)	0.21951 (10)	0.0212 (4)
C11	0.0560 (3)	0.8461 (3)	0.26607 (10)	0.0203 (4)
C12	0.1700 (3)	0.7116 (3)	0.24340 (10)	0.0212 (4)
C13	0.1431 (4)	0.6016 (3)	0.16156 (10)	0.0271 (5)
H131	0.2245	0.7004	0.1258	0.032*
H132	−0.0491	0.5401	0.1430	0.032*
C14	0.2644 (4)	0.4394 (3)	0.15111 (10)	0.0238 (4)
H141	0.4586	0.4989	0.1669	0.029*
H142	0.1864	0.3390	0.1866	0.029*
C15	0.2150 (4)	0.3371 (3)	0.06527 (11)	0.0308 (5)
H151	0.2864	0.4391	0.0298	0.037*
H152	0.0205	0.2744	0.0504	0.037*
C16	0.3418 (4)	0.1780 (3)	0.05116 (11)	0.0312 (5)
H161	0.3027	0.1179	−0.0050	0.041 (3)*
H162	0.2692	0.0745	0.0851	0.041 (3)*
H163	0.5351	0.2393	0.0644	0.041 (3)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0266 (7)	0.0250 (7)	0.0218 (7)	0.0141 (6)	−0.0015 (5)	−0.0002 (6)
O2	0.0320 (8)	0.0337 (8)	0.0265 (7)	0.0200 (7)	−0.0032 (6)	0.0030 (6)
O3	0.0341 (8)	0.0309 (8)	0.0196 (7)	0.0159 (6)	−0.0022 (6)	−0.0005 (6)
C1	0.0240 (10)	0.0232 (10)	0.0209 (10)	0.0074 (9)	0.0008 (8)	0.0009 (9)
C2	0.0248 (10)	0.0241 (10)	0.0208 (10)	0.0107 (9)	0.0004 (8)	−0.0009 (8)
C3	0.0205 (10)	0.0192 (10)	0.0214 (10)	0.0061 (8)	0.0029 (7)	0.0018 (8)
C4	0.0214 (10)	0.0190 (10)	0.0224 (10)	0.0074 (8)	0.0029 (8)	0.0028 (8)
C5	0.0284 (11)	0.0245 (11)	0.0231 (10)	0.0113 (9)	0.0003 (8)	0.0001 (9)
C6	0.0322 (11)	0.0206 (11)	0.0284 (11)	0.0122 (9)	0.0014 (9)	−0.0044 (9)
C7	0.0266 (11)	0.0223 (10)	0.0323 (11)	0.0134 (9)	0.0042 (8)	0.0046 (9)
C8	0.0247 (10)	0.0230 (10)	0.0244 (10)	0.0090 (9)	0.0011 (8)	0.0054 (9)
C9	0.0209 (10)	0.0191 (10)	0.0211 (10)	0.0075 (8)	0.0022 (7)	0.0032 (8)
C10	0.0210 (10)	0.0216 (10)	0.0205 (10)	0.0066 (8)	0.0028 (8)	0.0035 (8)
C11	0.0205 (10)	0.0209 (10)	0.0192 (9)	0.0073 (8)	0.0010 (7)	0.0021 (8)
C12	0.0197 (10)	0.0219 (10)	0.0226 (10)	0.0082 (8)	0.0019 (7)	0.0030 (8)
C13	0.0314 (11)	0.0302 (11)	0.0221 (10)	0.0164 (9)	0.0000 (8)	−0.0026 (9)
C14	0.0260 (10)	0.0223 (10)	0.0238 (10)	0.0098 (8)	0.0029 (8)	0.0020 (8)
C15	0.0349 (12)	0.0352 (12)	0.0254 (11)	0.0194 (10)	−0.0013 (8)	−0.0031 (9)
C16	0.0413 (12)	0.0342 (12)	0.0221 (10)	0.0211 (10)	0.0016 (9)	−0.0037 (9)

Geometric parameters (Å, º)

O1—C12	1.367 (2)	C8—H8	0.9500
O1—C1	1.423 (2)	C9—C10	1.490 (2)
O2—C1	1.206 (2)	C10—C11	1.481 (2)
O3—C10	1.222 (2)	C11—C12	1.345 (2)
C1—C2	1.435 (2)	C12—C13	1.492 (2)
C2—C3	1.346 (2)	C13—C14	1.519 (2)
C2—H2	0.9499	C13—H131	0.9900
C3—C11	1.438 (2)	C13—H132	0.9900
C3—C4	1.473 (2)	C14—C15	1.520 (2)
C4—C5	1.385 (2)	C14—H141	0.9900
C4—C9	1.401 (2)	C14—H142	0.9900
C5—C6	1.384 (2)	C15—C16	1.525 (2)
C5—H5	0.9500	C15—H151	0.9901
C6—C7	1.397 (3)	C15—H152	0.9900
C6—H6	0.9500	C16—H161	0.9800
C7—C8	1.386 (3)	C16—H162	0.9800
C7—H7	0.9499	C16—H163	0.9800
C8—C9	1.388 (2)
C12—O1—C1	123.11 (13)	C12—C11—C3	120.68 (15)
O2—C1—O1	115.30 (15)	C12—C11—C10	130.43 (16)
O2—C1—C2	128.03 (17)	C3—C11—C10	108.81 (14)
O1—C1—C2	116.66 (15)	C11—C12—O1	118.92 (16)
C3—C2—C1	119.63 (17)	C11—C12—C13	126.38 (16)
C3—C2—H2	120.2	O1—C12—C13	114.68 (15)
C1—C2—H2	120.2	C12—C13—C14	117.56 (15)
C2—C3—C11	120.94 (16)	C12—C13—H131	107.9
C2—C3—C4	131.19 (17)	C14—C13—H131	107.9
C11—C3—C4	107.85 (14)	C12—C13—H132	107.9
C5—C4—C9	120.68 (17)	C14—C13—H132	107.9
C5—C4—C3	130.91 (16)	H131—C13—H132	107.2
C9—C4—C3	108.40 (15)	C13—C14—C15	111.58 (15)
C6—C5—C4	118.08 (17)	C13—C14—H141	109.3
C6—C5—H5	121.0	C15—C14—H141	109.3
C4—C5—H5	121.0	C13—C14—H142	109.3
C5—C6—C7	121.45 (17)	C15—C14—H142	109.3
C5—C6—H6	119.3	H141—C14—H142	108.0
C7—C6—H6	119.3	C14—C15—C16	113.51 (15)
C8—C7—C6	120.55 (17)	C14—C15—H151	108.9
C8—C7—H7	119.7	C16—C15—H151	108.9
C6—C7—H7	119.7	C14—C15—H152	108.9
C7—C8—C9	118.13 (16)	C16—C15—H152	108.9
C7—C8—H8	120.9	H151—C15—H152	107.7
C9—C8—H8	120.9	C15—C16—H161	109.5
C8—C9—C4	121.10 (17)	C15—C16—H162	109.5
C8—C9—C10	128.99 (15)	H161—C16—H162	109.5
C4—C9—C10	109.90 (15)	C15—C16—H163	109.5
O3—C10—C11	128.33 (16)	H161—C16—H163	109.5
O3—C10—C9	126.65 (16)	H162—C16—H163	109.5
C11—C10—C9	105.02 (14)
O1—C12—C13—C14	8.3 (2)	C13—C14—C15—C16	177.91 (17)
C12—C13—C14—C15	178.49 (16)

(bIRT) 1-n-Butylindeno[2,1-c]pyran-3,9-dione

Crystal data

C16H14O3	Z = 2
Mr = 254.27	F(000) = 268
Triclinic, P1	Dx = 1.337 Mg m^−3
a = 5.4330 (3) Å	Mo Kα radiation, λ = 0.71073 Å
b = 7.2863 (4) Å	Cell parameters from 1474 reflections
c = 17.0874 (9) Å	θ = 2.4–22.8°
α = 97.426 (2)°	µ = 0.09 mm^−1
β = 92.884 (2)°	T = 293 K
γ = 108.874 (2)°	Irregular, colourless
V = 631.62 (6) Å^3	0.30 × 0.12 × 0.10 mm

Data collection

Bruker SMART CCD 6000 area-detector diffractometer	1138 reflections with I > 2σ(I)
Radiation source: sealed X-ray tube	Rint = 0.039
Graphite monochromator	θmax = 25.0°, θmin = 1.2°
Detector resolution: 5.6 pixels mm^-1	h = −6→6
ω scans	k = −8→8
6510 measured reflections	l = −20→20
2222 independent reflections

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)] = 0.039	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.096	H-atom parameters constrained
S = 0.84	w = 1/[σ^2(Fo^2) + (0.0473P)^2] where P = (Fo^2 + 2Fc^2)/3
2222 reflections	(Δ/σ)max < 0.001
174 parameters	Δρmax = 0.20 e Å^−3
0 restraints	Δρmin = −0.11 e Å^−3

Special details

Experimental. The data collection nominally covered a full sphere of reciprocal space by a combination of 4 sets of ω scans each set at different φ and/or 2θ angles and each scan (20 s exposure) covering -0.3° in ω. The crystal to detector distance was 4.85 cm.

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	0.3367 (3)	0.6718 (2)	0.29864 (8)	0.0580 (4)
O2	0.5369 (3)	0.7157 (2)	0.41943 (9)	0.0731 (5)
O3	−0.2037 (3)	0.8665 (2)	0.15197 (9)	0.0702 (5)
C1	0.3923 (4)	0.7667 (3)	0.37858 (13)	0.0566 (6)
C2	0.2737 (4)	0.9127 (3)	0.40021 (12)	0.0549 (6)
H2	0.3047	0.9805	0.4517	0.066*
C3	0.1170 (4)	0.9515 (3)	0.34585 (11)	0.0481 (5)
C4	−0.0197 (4)	1.0962 (3)	0.35063 (12)	0.0482 (5)
C5	−0.0275 (4)	1.2364 (3)	0.41260 (13)	0.0627 (6)
H5	0.0650	1.2510	0.4616	0.075*
C6	−0.1753 (4)	1.3538 (3)	0.39990 (14)	0.0678 (7)
H6	−0.1847	1.4472	0.4412	0.081*
C7	−0.3105 (4)	1.3354 (3)	0.32665 (14)	0.0649 (7)
H7	−0.4077	1.4171	0.3193	0.078*
C8	−0.3019 (4)	1.1967 (3)	0.26453 (13)	0.0606 (6)
H8	−0.3926	1.1839	0.2154	0.073*
C9	−0.1559 (4)	1.0775 (3)	0.27695 (12)	0.0486 (5)
C10	−0.1122 (4)	0.9202 (3)	0.22093 (12)	0.0512 (6)
C11	0.0628 (4)	0.8464 (3)	0.26681 (11)	0.0475 (5)
C12	0.1738 (4)	0.7110 (3)	0.24442 (12)	0.0513 (6)
C13	0.1471 (5)	0.5983 (3)	0.16367 (13)	0.0699 (7)
H131	0.2205	0.6917	0.1283	0.084*
H132	−0.0381	0.5390	0.1466	0.084*
C14	0.2673 (4)	0.4402 (3)	0.15115 (12)	0.0619 (6)
H141	0.1971	0.3452	0.1862	0.074*
H142	0.4543	0.4975	0.1655	0.074*
C15	0.2188 (5)	0.3354 (4)	0.06698 (14)	0.0784 (8)
H151	0.0317	0.2741	0.0536	0.094*
H152	0.2815	0.4318	0.0320	0.094*
C16	0.3462 (5)	0.1808 (4)	0.05112 (14)	0.0859 (8)
H161	0.3030	0.1199	−0.0033	0.125 (6)*
H162	0.2844	0.0834	0.0849	0.125 (6)*
H163	0.5323	0.2405	0.0617	0.125 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0651 (10)	0.0619 (10)	0.0530 (9)	0.0349 (8)	−0.0056 (7)	−0.0013 (8)
O2	0.0826 (12)	0.0840 (12)	0.0650 (11)	0.0503 (10)	−0.0147 (9)	0.0052 (9)
O3	0.0859 (12)	0.0811 (12)	0.0475 (10)	0.0406 (10)	−0.0115 (8)	−0.0028 (9)
C1	0.0613 (15)	0.0589 (15)	0.0498 (14)	0.0251 (13)	−0.0046 (11)	−0.0007 (12)
C2	0.0605 (14)	0.0598 (15)	0.0460 (13)	0.0268 (12)	−0.0030 (11)	−0.0007 (11)
C3	0.0500 (13)	0.0465 (13)	0.0476 (13)	0.0180 (11)	0.0001 (10)	0.0033 (11)
C4	0.0512 (13)	0.0447 (13)	0.0501 (13)	0.0199 (11)	0.0014 (10)	0.0026 (11)
C5	0.0720 (16)	0.0576 (15)	0.0603 (15)	0.0304 (13)	−0.0037 (12)	−0.0041 (13)
C6	0.0782 (17)	0.0567 (15)	0.0717 (17)	0.0340 (14)	0.0011 (14)	−0.0061 (13)
C7	0.0711 (17)	0.0539 (15)	0.0791 (17)	0.0352 (13)	0.0027 (13)	0.0080 (14)
C8	0.0648 (15)	0.0602 (15)	0.0620 (15)	0.0282 (13)	−0.0006 (12)	0.0119 (13)
C9	0.0527 (13)	0.0461 (13)	0.0503 (13)	0.0224 (11)	0.0001 (10)	0.0051 (11)
C10	0.0536 (14)	0.0539 (14)	0.0462 (14)	0.0195 (11)	0.0002 (11)	0.0059 (11)
C11	0.0519 (14)	0.0486 (13)	0.0436 (13)	0.0212 (12)	0.0004 (10)	0.0030 (11)
C12	0.0501 (13)	0.0544 (14)	0.0486 (13)	0.0198 (12)	−0.0003 (10)	0.0011 (11)
C13	0.0828 (18)	0.0798 (17)	0.0540 (14)	0.0462 (15)	−0.0055 (12)	−0.0104 (13)
C14	0.0697 (16)	0.0581 (15)	0.0589 (15)	0.0273 (13)	0.0066 (11)	−0.0027 (12)
C15	0.0901 (19)	0.0877 (19)	0.0627 (16)	0.0481 (16)	−0.0019 (13)	−0.0147 (14)
C16	0.111 (2)	0.094 (2)	0.0629 (16)	0.0582 (19)	0.0006 (14)	−0.0138 (15)

Geometric parameters (Å, º)

O1—C12	1.369 (2)	C8—H8	0.9299
O1—C1	1.419 (2)	C9—C10	1.484 (3)
O2—C1	1.201 (2)	C10—C11	1.474 (3)
O3—C10	1.218 (2)	C11—C12	1.339 (3)
C1—C2	1.432 (3)	C12—C13	1.486 (3)
C2—C3	1.346 (3)	C13—C14	1.495 (3)
C2—H2	0.9301	C13—H131	0.9700
C3—C11	1.429 (3)	C13—H132	0.9700
C3—C4	1.470 (3)	C14—C15	1.506 (3)
C4—C5	1.385 (3)	C14—H141	0.9700
C4—C9	1.396 (3)	C14—H142	0.9700
C5—C6	1.378 (3)	C15—C16	1.505 (3)
C5—H5	0.9299	C15—H151	0.9700
C6—C7	1.387 (3)	C15—H152	0.9699
C6—H6	0.9299	C16—H161	0.9599
C7—C8	1.381 (3)	C16—H162	0.9600
C7—H7	0.9300	C16—H163	0.9600
C8—C9	1.380 (3)
C12—O1—C1	123.01 (16)	C12—C11—C3	120.61 (18)
O2—C1—O1	115.49 (19)	C12—C11—C10	130.41 (18)
O2—C1—C2	128.1 (2)	C3—C11—C10	108.92 (17)
O1—C1—C2	116.39 (18)	C11—C12—O1	119.13 (18)
C3—C2—C1	119.80 (19)	C11—C12—C13	126.63 (18)
C3—C2—H2	120.1	O1—C12—C13	114.21 (17)
C1—C2—H2	120.1	C12—C13—C14	119.14 (18)
C2—C3—C11	121.01 (18)	C12—C13—H131	107.5
C2—C3—C4	131.27 (19)	C14—C13—H131	107.5
C11—C3—C4	107.71 (16)	C12—C13—H132	107.5
C5—C4—C9	120.35 (19)	C14—C13—H132	107.5
C5—C4—C3	131.12 (19)	H131—C13—H132	107.0
C9—C4—C3	108.52 (17)	C13—C14—C15	113.21 (19)
C6—C5—C4	118.4 (2)	C13—C14—H141	108.9
C6—C5—H5	120.8	C15—C14—H141	108.9
C4—C5—H5	120.8	C13—C14—H142	108.9
C5—C6—C7	121.2 (2)	C15—C14—H142	108.9
C5—C6—H6	119.4	H141—C14—H142	107.7
C7—C6—H6	119.4	C16—C15—C14	114.9 (2)
C8—C7—C6	120.6 (2)	C16—C15—H151	108.6
C8—C7—H7	119.7	C14—C15—H151	108.6
C6—C7—H7	119.7	C16—C15—H152	108.6
C9—C8—C7	118.6 (2)	C14—C15—H152	108.5
C9—C8—H8	120.7	H151—C15—H152	107.5
C7—C8—H8	120.7	C15—C16—H161	109.5
C8—C9—C4	120.87 (19)	C15—C16—H162	109.5
C8—C9—C10	129.45 (19)	H161—C16—H162	109.5
C4—C9—C10	109.68 (17)	C15—C16—H163	109.5
O3—C10—C11	128.54 (19)	H161—C16—H163	109.5
O3—C10—C9	126.31 (18)	H162—C16—H163	109.5
C11—C10—C9	105.16 (17)
C11—C12—C13—C14	−174.8 (2)	C13—C14—C15—C16	177.5 (2)
C12—C13—C14—C15	178.5 (2)