trans-4-[2-(1,3-Benzoxazol-2-yl)ethen­yl]benzaldehyde

The title mol­ecule, C₁₆H₁₁NO₂, is planar with an r.m.s. deviation of 0.0362 (4) Å. The benzene ring and benzoxazole ring system adopt a trans configuration with respect to the central double bond.

Key indicators

• Single-crystal X-ray study
• T = 294 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.066
• wR factor = 0.193
• Data-to-parameter ratio = 12.5

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT230_ALERT_2_B Hirshfeld Test Diff for    O2     -   C16     ..      10.05 su

Alert level C
DIFMX01_ALERT_2_C  The maximum difference density is > 0.1*ZMAX*0.75
            _refine_diff_density_max given =      0.692
            Test value =      0.600
DIFMX02_ALERT_1_C  The maximum difference density is > 0.1*ZMAX*0.75
            The relevant atom site should be identified.
PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical .          ?
PLAT094_ALERT_2_C Ratio of Maximum / Minimum Residual Density ....       2.96
PLAT097_ALERT_2_C Maximum (Positive) Residual Density ............       0.69 e/A   
PLAT241_ALERT_2_C Check High      Ueq as Compared to Neighbors for         C2
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        C13
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       2.19
PLAT340_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...          5

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
   9 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   7 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

---

S1. Comment

Recently, a number of organic two-photon induced fluorescent (TPIF) materials have beeen widely investigated because of their various applications, especially in TPIF microscopy (Denk et al., 1990; Helmchen et al., 2002; Zhang et al., 2002). Among the design strategies for TPIF materials, it is reported that introducing a heteroatom into a molecular structure is an efficient way to obtain excellent TPIF molecules because π-deficient and π-excesive heterocycles may act as efficent acceptor and donor moieties, respectively. The title compound, namely tran-2-(p-formylstyryl)benzexazole, consists of atypical A-π-A' structure, where the heterocyclic, styryl and formyl groups are employed as A, π-conjugated and A' moieties, repectively. Here, we present the crystal structure of the title compound, (I).

The molecule of (I) contains a benzexazole ring and a benzene ring which they bounded through a C═C double bond to each other. The terminal benzene ring and benzexazole ring adopt a trans configuration with respect to the central double bond. The whole molecule assumes a planar structure, with an r.m.s deviation of 0.0362 (4) Å. As atom C6 is a bridged atom in benzexazole ring, it has a distorted trigonal geometry, with the C1—C6—N1 [108.9 (3) °] and C5—C6—N1 [131.3 (3) °] angles deviating significantly from ideal sp² value of 120°. The similar result is also observed for the other bridged C1 atom. As a result of the π-π conjugation, the C7—C8 [1.442 (4) Å] and C9—C10 [1.461 (4) Å] bonds are significantly shorter than the ideal single bonds.

Related literature

For related literature, see: Denk et al. (1990); Helmchen & Denk (2002); Huang et al. (2003); Zhang et al. (2002).

S2. Experimental

The title compound was prepared according to the literature's report (Huang et al., 2003). Single crystals suitable for X-ray analysis were obtained by slow evaporation at 298 K of a mixture solution of dichloromethane and ethyl acetate in volume of 1:5.

S3. Refinement

All H atoms were positioned geometrically and refined using a riding model. Constrained distances: 0.93Å for Csp²—H. U_iso(H) values were fixed at 1.2U_eq(C).

Computing details

Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1997); software used to prepare material for publication: SHELXTL.

Figures

Fig. 1. View of the molecule of (I) showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 35% probability level.

trans-4-[2-(1,3-Benzoxazol-2-yl)ethenyl]benzaldehyde

Crystal data

C16H11NO2	Z = 2
Mr = 249.26	F(000) = 260
Triclinic, P1	Dx = 1.346 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.509 (2) Å	Cell parameters from 943 reflections
b = 7.404 (3) Å	θ = 3.0–26.0°
c = 14.005 (5) Å	µ = 0.09 mm^−1
α = 79.885 (6)°	T = 294 K
β = 80.766 (6)°	Plate, colourless
γ = 68.565 (7)°	0.22 × 0.20 × 0.08 mm
V = 615.1 (4) Å^3

Data collection

Bruker SMART CCD area-detector diffractometer	2147 independent reflections
Radiation source: fine-focus sealed tube	1248 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.020
φ and ω scans	θmax = 25.0°, θmin = 3.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −7→7
Tmin = 0.981, Tmax = 0.993	k = −8→7
3147 measured reflections	l = −16→16

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)] = 0.066	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.193	H-atom parameters constrained
S = 1.18	w = 1/[σ^2(Fo^2) + (0.0705P)^2 + 0.2468P] where P = (Fo^2 + 2Fc^2)/3
2147 reflections	(Δ/σ)max = 0.001
172 parameters	Δρmax = 0.69 e Å^−3
0 restraints	Δρmin = −0.23 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 > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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

	x	y	z	Uiso*/Ueq
O1	0.0390 (4)	0.7576 (4)	0.18636 (16)	0.0614 (7)
O2	−0.5701 (6)	0.8461 (5)	−0.3828 (2)	0.1154 (12)
N1	0.4016 (5)	0.6624 (4)	0.13459 (19)	0.0626 (8)
C1	0.1516 (5)	0.7422 (5)	0.2649 (2)	0.0531 (9)
C2	0.0685 (7)	0.7789 (7)	0.3581 (3)	0.0821 (13)
H2	−0.0829	0.8178	0.3780	0.098*
C3	0.2213 (7)	0.7550 (6)	0.4211 (3)	0.0776 (12)
H3	0.1714	0.7775	0.4855	0.093*
C4	0.4451 (7)	0.6987 (6)	0.3918 (3)	0.0671 (11)
H4	0.5434	0.6837	0.4365	0.080*
C5	0.5254 (6)	0.6646 (6)	0.2974 (3)	0.0656 (10)
H5	0.6765	0.6277	0.2771	0.079*
C6	0.3727 (5)	0.6870 (5)	0.2331 (2)	0.0503 (8)
C7	0.2032 (6)	0.7049 (5)	0.1118 (2)	0.0515 (8)
C8	0.1403 (6)	0.7046 (5)	0.0177 (2)	0.0570 (9)
H8	0.2536	0.6616	−0.0316	0.068*
C9	−0.0657 (6)	0.7607 (5)	−0.0037 (2)	0.0542 (9)
H9	−0.1763	0.7984	0.0474	0.065*
C10	−0.1412 (5)	0.7706 (4)	−0.0978 (2)	0.0463 (8)
C11	0.0027 (6)	0.7232 (6)	−0.1820 (2)	0.0635 (10)
H11	0.1551	0.6820	−0.1794	0.076*
C12	−0.0774 (6)	0.7366 (6)	−0.2684 (2)	0.0683 (11)
H12	0.0220	0.7048	−0.3237	0.082*
C13	−0.3023 (6)	0.7960 (5)	−0.2757 (2)	0.0527 (9)
C14	−0.4468 (6)	0.8462 (6)	−0.1935 (2)	0.0677 (11)
H14	−0.5991	0.8896	−0.1969	0.081*
C15	−0.3668 (6)	0.8325 (6)	−0.1066 (2)	0.0657 (10)
H15	−0.4671	0.8657	−0.0517	0.079*
C16	−0.3789 (7)	0.8041 (6)	−0.3703 (3)	0.0742 (12)
H16	−0.2727	0.7748	−0.4237	0.089*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0536 (14)	0.0881 (18)	0.0465 (14)	−0.0250 (12)	−0.0114 (11)	−0.0122 (12)
O2	0.107 (3)	0.162 (3)	0.088 (2)	−0.043 (2)	−0.032 (2)	−0.031 (2)
N1	0.0557 (19)	0.088 (2)	0.0449 (18)	−0.0203 (15)	−0.0109 (13)	−0.0166 (15)
C1	0.052 (2)	0.069 (2)	0.0400 (18)	−0.0195 (17)	−0.0139 (15)	−0.0052 (16)
C2	0.065 (3)	0.134 (4)	0.050 (2)	−0.037 (2)	0.0000 (19)	−0.019 (2)
C3	0.090 (3)	0.111 (3)	0.036 (2)	−0.039 (3)	−0.0101 (19)	−0.010 (2)
C4	0.076 (3)	0.079 (3)	0.051 (2)	−0.027 (2)	−0.0269 (19)	−0.0050 (19)
C5	0.055 (2)	0.085 (3)	0.056 (2)	−0.0169 (19)	−0.0191 (17)	−0.0127 (19)
C6	0.060 (2)	0.057 (2)	0.0340 (17)	−0.0181 (16)	−0.0107 (15)	−0.0060 (14)
C7	0.060 (2)	0.059 (2)	0.0375 (18)	−0.0216 (17)	−0.0071 (16)	−0.0062 (15)
C8	0.066 (2)	0.069 (2)	0.0406 (19)	−0.0252 (18)	−0.0082 (16)	−0.0112 (16)
C9	0.061 (2)	0.062 (2)	0.0416 (19)	−0.0204 (17)	−0.0119 (16)	−0.0080 (15)
C10	0.052 (2)	0.050 (2)	0.0389 (18)	−0.0187 (15)	−0.0114 (14)	−0.0033 (14)
C11	0.050 (2)	0.091 (3)	0.048 (2)	−0.0175 (18)	−0.0104 (16)	−0.0151 (18)
C12	0.063 (2)	0.103 (3)	0.0386 (19)	−0.022 (2)	−0.0054 (16)	−0.0207 (19)
C13	0.060 (2)	0.065 (2)	0.0383 (18)	−0.0244 (17)	−0.0130 (15)	−0.0088 (15)
C14	0.053 (2)	0.104 (3)	0.052 (2)	−0.031 (2)	−0.0103 (17)	−0.012 (2)
C15	0.058 (2)	0.099 (3)	0.043 (2)	−0.029 (2)	−0.0031 (16)	−0.0176 (19)
C16	0.063 (3)	0.096 (3)	0.069 (3)	−0.025 (2)	−0.026 (2)	−0.016 (2)

Geometric parameters (Å, º)

O1—C7	1.365 (4)	C8—C9	1.318 (5)
O1—C1	1.383 (4)	C8—H8	0.9300
O2—C16	1.202 (4)	C9—C10	1.461 (4)
N1—C7	1.292 (4)	C9—H9	0.9300
N1—C6	1.397 (4)	C10—C15	1.389 (5)
C1—C2	1.365 (5)	C10—C11	1.393 (4)
C1—C6	1.365 (4)	C11—C12	1.367 (5)
C2—C3	1.377 (5)	C11—H11	0.9300
C2—H2	0.9300	C12—C13	1.381 (5)
C3—C4	1.375 (5)	C12—H12	0.9300
C3—H3	0.9300	C13—C14	1.377 (5)
C4—C5	1.372 (5)	C13—C16	1.473 (5)
C4—H4	0.9300	C14—C15	1.373 (5)
C5—C6	1.393 (4)	C14—H14	0.9300
C5—H5	0.9300	C15—H15	0.9300
C7—C8	1.442 (4)	C16—H16	0.9300
C7—O1—C1	104.0 (2)	C7—C8—H8	117.5
C7—N1—C6	104.7 (3)	C8—C9—C10	127.8 (3)
C2—C1—C6	123.2 (3)	C8—C9—H9	116.1
C2—C1—O1	129.0 (3)	C10—C9—H9	116.1
C6—C1—O1	107.7 (3)	C15—C10—C11	116.9 (3)
C1—C2—C3	116.3 (4)	C15—C10—C9	119.8 (3)
C1—C2—H2	121.8	C11—C10—C9	123.3 (3)
C3—C2—H2	121.8	C12—C11—C10	120.8 (3)
C4—C3—C2	122.0 (3)	C12—C11—H11	119.6
C4—C3—H3	119.0	C10—C11—H11	119.6
C2—C3—H3	119.0	C11—C12—C13	121.7 (3)
C5—C4—C3	120.8 (3)	C11—C12—H12	119.2
C5—C4—H4	119.6	C13—C12—H12	119.2
C3—C4—H4	119.6	C14—C13—C12	118.3 (3)
C4—C5—C6	117.8 (3)	C14—C13—C16	122.5 (3)
C4—C5—H5	121.1	C12—C13—C16	119.3 (3)
C6—C5—H5	121.1	C15—C14—C13	120.2 (3)
C1—C6—C5	119.8 (3)	C15—C14—H14	119.9
C1—C6—N1	108.9 (3)	C13—C14—H14	119.9
C5—C6—N1	131.3 (3)	C14—C15—C10	122.2 (3)
N1—C7—O1	114.7 (3)	C14—C15—H15	118.9
N1—C7—C8	127.1 (3)	C10—C15—H15	118.9
O1—C7—C8	118.2 (3)	O2—C16—C13	124.1 (4)
C9—C8—C7	124.9 (3)	O2—C16—H16	118.0
C9—C8—H8	117.5	C13—C16—H16	118.0
C7—O1—C1—C2	179.6 (4)	C1—O1—C7—C8	179.7 (3)
C7—O1—C1—C6	1.5 (3)	N1—C7—C8—C9	−175.6 (3)
C6—C1—C2—C3	−0.8 (6)	O1—C7—C8—C9	3.5 (5)
O1—C1—C2—C3	−178.6 (4)	C7—C8—C9—C10	177.7 (3)
C1—C2—C3—C4	0.5 (6)	C8—C9—C10—C15	179.5 (3)
C2—C3—C4—C5	0.2 (6)	C8—C9—C10—C11	−1.4 (5)
C3—C4—C5—C6	−0.6 (6)	C15—C10—C11—C12	−0.4 (5)
C2—C1—C6—C5	0.4 (6)	C9—C10—C11—C12	−179.5 (3)
O1—C1—C6—C5	178.6 (3)	C10—C11—C12—C13	−0.4 (6)
C2—C1—C6—N1	−179.7 (4)	C11—C12—C13—C14	1.3 (6)
O1—C1—C6—N1	−1.5 (4)	C11—C12—C13—C16	−178.9 (4)
C4—C5—C6—C1	0.3 (5)	C12—C13—C14—C15	−1.5 (6)
C4—C5—C6—N1	−179.6 (3)	C16—C13—C14—C15	178.7 (4)
C7—N1—C6—C1	0.8 (4)	C13—C14—C15—C10	0.7 (6)
C7—N1—C6—C5	−179.3 (4)	C11—C10—C15—C14	0.3 (5)
C6—N1—C7—O1	0.2 (4)	C9—C10—C15—C14	179.4 (3)
C6—N1—C7—C8	179.3 (3)	C14—C13—C16—O2	−3.4 (7)
C1—O1—C7—N1	−1.1 (4)	C12—C13—C16—O2	176.8 (4)