(E)-4-Methyl-2-[3-(trifluoro­meth­yl)­phenyl­imino­meth­yl]phenol

The mol­ecule of the title compound, C₁₅H₁₂F₃NO, is not planar and the dihedral angle between the planes of the two aromatic rings is 33.82 (11)°. The mol­ecule exists in the phenol–imine tautomeric form, with a strong intra­molecular O—H...N hydrogen bond [N...O = 2.609 (3) Å].

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.049
• wR factor = 0.144
• Data-to-parameter ratio = 15.3

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT242_ALERT_2_B Check Low       Ueq as Compared to Neighbors for        C14

Alert level C
PLAT026_ALERT_3_C Ratio Observed / Unique Reflections too Low ....         41 Perc.
PLAT063_ALERT_3_C Crystal Probably too Large for Beam Size .......       0.80 mm
PLAT230_ALERT_2_C Hirshfeld Test Diff for    C12    -   C14     ..       5.47 su
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
   4 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 ALERT type 2 Indicator that the structure model may be wrong or deficient
   3 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

Schiff bases have been extensively used as ligands in the field of coordination chemistry (Calligaris et al., 1972). There are two characteristic properties of Schiff bases, viz. photochromism and thermochromism (Cohen et al., 1964). These properties result from proton transfer from the hydroxyl O atom to the imine N atom (Hadjoudis et al., 1987). Schiff bases display two possible tautomeric forms, namely the phenol-imine and keto-amine forms. In the solid state, the keto-amine tautomer has been found in naphthaldimine (Hökelek et al., 2000). However, in the solid state, it has been established that there is keto-amine tautomerism in naphthaldimine, while the phenol-imine form exists in salicylaldimine Schiff bases (Dey et al., 2001).

Our investigations show that compound (I) adopts the phenol-imine tautomeric form. An ORTEP-3 (Farrugia, 1997) plot of the molecule of (I) is shown in Fig.1. The C8—N1 and C1—C7 bond lengths are 1.426 (3) and 1.450 (3) Å, respectively (Table 1), and agree with the corresponding distances in (E)-2-methoxy-6-[(2-trifluoromethylphenylimino)methyl]phenol [1.418 (5) and 1.454 (5) Å;Şahin et al., 2005]. The N1═C7 bond length of 1.270 (3) Å is typical of a double bond, similar to the corresponding bond length in N-[3,5-bis(trifluoromethyl)phenyl]salicylaldimine [1.276 (4) Å; Karadayı et al., 2003]. The O1—C6 distance of 1.352 (3) Å is close to the value of 1.349 (6) Å in 3-tert-butyl-2-hydroxy-5-methoxyazobenzene (Işik et al., 1998). The dihedral angle between the C1—C6 and C8—C13 benzene rings is 33.82 (11)°.

There is a strong intramolecular hydrogen bond, O1—H1···N1, which forms an S(6) motif (Bernstein et al., 1995). The O1···N1 distance of 2.609 (3) Å is comparable to those observed for analogous hydrogen bonds in N-[3,5-bis(trifluoromethyl)phenyl]salicylaldimine [2.604 (4) Å; Karadayı et al., 2003] and 2,2-salicylaldimine [2.611 (6) Å; Xu et al., 1994].

The crystal packing is stabilized by van der Waals interactions.

Related literature

Schiff base compounds can be classified by their photochromic and thermochromic characteristics (Cohen et al., 1964; Hadjoudis et al., 1987). For related literature, see: Bernstein et al. (1995); Calligaris et al. (1972); Dey et al. (2001); Hökelek et al. (2000); Işik et al. (1998); Karadayı et al. (2003); Şahin et al. (2005); Xu et al. (1994).

S2. Experimental

The title compound was prepared by refluxing a mixture of a solution containing 5-methylsalicylaldehyde (0.1116 g, 0.82 mmol) in ethanol (20 ml) and a solution containing 3-trifluoromethylaniline (0.1 ml, 0.82 mmol) in ethanol (20 ml). The reaction mixture was stirred for 1 h under reflux. Crystals of (I) suitable for X-ray analysis were obtained from ethylalcohol by slow evaporation (yield 98%; m.p. 342–344 K).

S3. Refinement

The hydroxyl H atom was located in a difference map and refined isotropically. All other H atoms were placed in calculated positions and constrained to ride on their parents atoms, with C—H = 0.93 or 0.96 Å and U_iso(H) = 1.2U_eq(C) or 1.5U_eq(methyl C).

Computing details

Data collection: X-AREA (Stoe & Cie, 2002); cell refinement: X-AREA; data reduction: X-RED32 (Stoe & Cie, 2002); 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. The molecular structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 40% probability level. The dashed line indicates a hydrogen bond.

(E)-4-Methyl-2-[3-(trifluoromethyl)phenyliminomethyl]phenol

Crystal data

C15H12F3NO	F(000) = 576
Mr = 279.26	Dx = 1.419 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 9332 reflections
a = 16.617 (2) Å	θ = 1.6–29.4°
b = 4.7788 (4) Å	µ = 0.12 mm^−1
c = 21.169 (3) Å	T = 296 K
β = 128.964 (9)°	Prism, yellow
V = 1307.0 (3) Å^3	0.80 × 0.24 × 0.14 mm
Z = 4

Data collection

Stoe IPDSII diffractometer	2847 independent reflections
Radiation source: fine-focus sealed tube	1178 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.086
Detector resolution: 6.67 pixels mm^-1	θmax = 27.0°, θmin = 1.6°
ω scans	h = −21→21
Absorption correction: integration (X-RED32; Stoe & Cie, 2002)	k = −6→5
Tmin = 0.933, Tmax = 0.986	l = −26→26
11701 measured 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)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.144	H atoms treated by a mixture of independent and constrained refinement
S = 0.83	w = 1/[σ^2(Fo^2) + (0.0723P)^2] where P = (Fo^2 + 2Fc^2)/3
2847 reflections	(Δ/σ)max = 0.002
186 parameters	Δρmax = 0.27 e Å^−3
0 restraints	Δρmin = −0.16 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
C1	0.21905 (19)	1.2208 (5)	0.24517 (15)	0.0656 (6)
C2	0.2946 (2)	1.4021 (5)	0.30512 (16)	0.0729 (7)
H2	0.3560	1.4202	0.3129	0.087*
C3	0.2820 (2)	1.5566 (5)	0.35362 (15)	0.0745 (7)
C4	0.1880 (2)	1.5241 (6)	0.33849 (17)	0.0845 (8)
H4	0.1763	1.6269	0.3694	0.101*
C5	0.1121 (2)	1.3478 (7)	0.28030 (19)	0.0860 (8)
H5	0.0510	1.3293	0.2730	0.103*
C6	0.1262 (2)	1.1969 (6)	0.23220 (16)	0.0717 (7)
C7	0.2370 (2)	1.0634 (5)	0.19651 (16)	0.0692 (6)
H7	0.3005	1.0811	0.2075	0.083*
C8	0.19094 (19)	0.7413 (5)	0.09500 (14)	0.0657 (6)
C9	0.1082 (2)	0.6765 (6)	0.01500 (16)	0.0818 (8)
H9	0.0424	0.7425	−0.0078	0.098*
C10	0.1231 (2)	0.5146 (6)	−0.03081 (16)	0.0915 (9)
H10	0.0675	0.4745	−0.0846	0.110*
C11	0.2191 (2)	0.4130 (6)	0.00244 (16)	0.0832 (8)
H11	0.2286	0.3012	−0.0283	0.100*
C12	0.30132 (19)	0.4762 (5)	0.08130 (14)	0.0672 (6)
C13	0.28763 (19)	0.6390 (5)	0.12808 (14)	0.0656 (6)
H13	0.3437	0.6791	0.1818	0.079*
C14	0.4051 (2)	0.3679 (6)	0.11797 (17)	0.0799 (7)
C15	0.3651 (3)	1.7462 (6)	0.41932 (17)	0.0982 (9)
H15A	0.4137	1.7859	0.4102	0.147*
H15B	0.4002	1.6565	0.4711	0.147*
H15C	0.3346	1.9178	0.4187	0.147*
F1	0.47297 (14)	0.5629 (4)	0.13755 (14)	0.1293 (7)
F2	0.44860 (14)	0.2318 (4)	0.18725 (12)	0.1262 (7)
F3	0.40792 (15)	0.1895 (5)	0.07209 (13)	0.1483 (9)
N1	0.16910 (16)	0.9023 (4)	0.13934 (13)	0.0714 (6)
O1	0.04908 (16)	1.0249 (5)	0.17525 (14)	0.0905 (6)
H1	0.070 (3)	0.954 (7)	0.155 (2)	0.113 (14)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0778 (16)	0.0658 (16)	0.0710 (15)	0.0124 (13)	0.0554 (14)	0.0147 (13)
C2	0.0826 (17)	0.0692 (16)	0.0824 (17)	0.0096 (14)	0.0593 (15)	0.0115 (14)
C3	0.102 (2)	0.0659 (15)	0.0740 (16)	0.0138 (15)	0.0639 (16)	0.0131 (13)
C4	0.114 (2)	0.084 (2)	0.0850 (18)	0.0252 (18)	0.0764 (18)	0.0172 (16)
C5	0.0942 (19)	0.099 (2)	0.0937 (19)	0.0155 (17)	0.0730 (18)	0.0133 (17)
C6	0.0779 (17)	0.0795 (18)	0.0718 (16)	0.0111 (15)	0.0538 (15)	0.0143 (14)
C7	0.0779 (16)	0.0710 (16)	0.0796 (17)	0.0051 (14)	0.0595 (15)	0.0097 (14)
C8	0.0737 (16)	0.0692 (15)	0.0634 (14)	−0.0013 (13)	0.0476 (13)	0.0042 (12)
C9	0.0714 (16)	0.097 (2)	0.0720 (17)	−0.0002 (14)	0.0424 (14)	0.0054 (15)
C10	0.089 (2)	0.112 (2)	0.0629 (16)	−0.0087 (18)	0.0425 (15)	−0.0117 (16)
C11	0.099 (2)	0.0899 (19)	0.0716 (17)	−0.0038 (17)	0.0593 (17)	−0.0080 (15)
C12	0.0777 (16)	0.0696 (16)	0.0649 (15)	0.0007 (13)	0.0499 (14)	0.0008 (12)
C13	0.0704 (15)	0.0716 (15)	0.0559 (13)	−0.0003 (12)	0.0402 (12)	0.0003 (12)
C14	0.092 (2)	0.0848 (19)	0.0755 (18)	−0.0003 (17)	0.0588 (16)	−0.0059 (16)
C15	0.130 (2)	0.090 (2)	0.0868 (19)	0.0026 (19)	0.0744 (19)	0.0024 (17)
F1	0.0990 (12)	0.1148 (14)	0.191 (2)	−0.0009 (11)	0.0992 (14)	0.0015 (14)
F2	0.1061 (13)	0.1614 (17)	0.1163 (14)	0.0445 (12)	0.0724 (11)	0.0485 (13)
F3	0.1314 (16)	0.176 (2)	0.1316 (16)	0.0307 (13)	0.0798 (14)	−0.0485 (15)
N1	0.0772 (13)	0.0758 (14)	0.0733 (13)	0.0040 (12)	0.0532 (12)	0.0067 (12)
O1	0.0824 (13)	0.1164 (17)	0.0894 (13)	0.0037 (12)	0.0621 (12)	0.0019 (12)

Geometric parameters (Å, º)

C1—C2	1.390 (3)	C9—C10	1.379 (4)
C1—C6	1.392 (3)	C9—H9	0.93
C1—C7	1.450 (3)	C10—C11	1.365 (4)
C2—C3	1.383 (3)	C10—H10	0.93
C2—H2	0.93	C11—C12	1.370 (3)
C3—C4	1.393 (4)	C11—H11	0.93
C3—C15	1.499 (4)	C12—C13	1.386 (3)
C4—C5	1.365 (4)	C12—C14	1.470 (4)
C4—H4	0.93	C13—H13	0.93
C5—C6	1.383 (4)	C14—F1	1.313 (3)
C5—H5	0.93	C14—F3	1.315 (3)
C6—O1	1.352 (3)	C14—F2	1.328 (3)
C7—N1	1.270 (3)	C15—H15A	0.96
C7—H7	0.93	C15—H15B	0.96
C8—C13	1.377 (3)	C15—H15C	0.96
C8—C9	1.388 (3)	O1—H1	0.78 (3)
C8—N1	1.426 (3)
C2—C1—C6	118.9 (2)	C11—C10—C9	120.3 (3)
C2—C1—C7	120.1 (2)	C11—C10—H10	119.8
C6—C1—C7	121.0 (2)	C9—C10—H10	119.8
C3—C2—C1	122.6 (2)	C10—C11—C12	119.8 (3)
C3—C2—H2	118.7	C10—C11—H11	120.1
C1—C2—H2	118.7	C12—C11—H11	120.1
C2—C3—C4	116.2 (3)	C11—C12—C13	120.5 (2)
C2—C3—C15	122.0 (3)	C11—C12—C14	120.4 (2)
C4—C3—C15	121.8 (3)	C13—C12—C14	119.0 (2)
C5—C4—C3	122.9 (3)	C8—C13—C12	119.9 (2)
C5—C4—H4	118.6	C8—C13—H13	120.0
C3—C4—H4	118.6	C12—C13—H13	120.0
C4—C5—C6	119.9 (3)	F1—C14—F3	105.7 (2)
C4—C5—H5	120.1	F1—C14—F2	103.6 (2)
C6—C5—H5	120.1	F3—C14—F2	104.5 (2)
O1—C6—C5	118.0 (3)	F1—C14—C12	114.0 (2)
O1—C6—C1	122.5 (2)	F3—C14—C12	114.4 (2)
C5—C6—C1	119.5 (3)	F2—C14—C12	113.5 (2)
N1—C7—C1	122.4 (2)	C3—C15—H15A	109.5
N1—C7—H7	118.8	C3—C15—H15B	109.5
C1—C7—H7	118.8	H15A—C15—H15B	109.5
C13—C8—C9	119.0 (2)	C3—C15—H15C	109.5
C13—C8—N1	123.7 (2)	H15A—C15—H15C	109.5
C9—C8—N1	117.2 (2)	H15B—C15—H15C	109.5
C10—C9—C8	120.3 (3)	C7—N1—C8	120.9 (2)
C10—C9—H9	119.8	C6—O1—H1	105 (3)
C8—C9—H9	119.8
C6—C1—C2—C3	1.2 (3)	C8—C9—C10—C11	1.0 (4)
C7—C1—C2—C3	−179.7 (2)	C9—C10—C11—C12	−1.1 (4)
C1—C2—C3—C4	−0.8 (3)	C10—C11—C12—C13	1.0 (4)
C1—C2—C3—C15	178.5 (2)	C10—C11—C12—C14	179.9 (3)
C2—C3—C4—C5	1.0 (4)	C9—C8—C13—C12	0.7 (3)
C15—C3—C4—C5	−178.4 (3)	N1—C8—C13—C12	177.8 (2)
C3—C4—C5—C6	−1.4 (4)	C11—C12—C13—C8	−0.8 (4)
C4—C5—C6—O1	−180.0 (2)	C14—C12—C13—C8	−179.7 (2)
C4—C5—C6—C1	1.7 (4)	C11—C12—C14—F1	115.3 (3)
C2—C1—C6—O1	−179.8 (2)	C13—C12—C14—F1	−65.9 (3)
C7—C1—C6—O1	1.1 (4)	C11—C12—C14—F3	−6.5 (4)
C2—C1—C6—C5	−1.6 (3)	C13—C12—C14—F3	172.3 (2)
C7—C1—C6—C5	179.3 (2)	C11—C12—C14—F2	−126.4 (3)
C2—C1—C7—N1	−177.7 (2)	C13—C12—C14—F2	52.5 (3)
C6—C1—C7—N1	1.4 (4)	C1—C7—N1—C8	−177.3 (2)
C13—C8—C9—C10	−0.8 (4)	C13—C8—N1—C7	31.7 (3)
N1—C8—C9—C10	−178.1 (2)	C9—C8—N1—C7	−151.1 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N1	0.78 (3)	1.89 (4)	2.609 (3)	153 (3)