research communications
Z)-6-[(2-hydroxy-4-methylanilino)methylidene]-4-methylcyclohexa-2,4-dien-1-one
and Hirshfeld surface analysis of (aOndokuz Mayıs University, Faculty of Arts and Sciences, Department of Physics, 55139, Kurupelit, Samsun, Turkey, bOndokuz Mayıs University, Faculty of Arts and Sciences, Department of Physics, 55139, Samsun, Turkey, cOndokuz Mayıs University, Faculty of Arts and Sciences, Department of Chemistry, 55139, Samsun, Turkey, and dTaras Shevchenko National University of Kyiv, Department of Chemistry, 64, Vladimirska Str., Kiev 01601, Ukraine
*Correspondence e-mail: sevgi.kansiz85@gmail.com, ifritsky@univ.kiev.ua
The title compound, C15H15NO2, is a Schiff base that exists in the keto–enamine tautomeric form and adopts a Z configuration. The molecule is almost planar, with the two phenyl rings twisted relative to each other by 9.60 (18)°. There is an intramolecular N—H⋯O hydrogen bond present forming an S(6) ring motif. In the crystal, pairs of O—H⋯O hydrogen bonds link adjacent molecules into inversion dimers with an R22(18) ring motif. The dimers are linked by very weak π–π interactions, forming layers parallel to (01). Hirshfeld surface analysis, two-dimensional fingerprint plots and the molecular electrostatic potential surfaces were used to analyse the intermolecular interactions, indicating that the most important contributions for the crystal packing are from H⋯H (55.2%), C⋯H/H⋯C (22.3%) and O⋯H/H⋯O (13.6%) interactions.
CCDC reference: 1902148
1. Chemical context
RCH=N–R′) and are prepared by condensation reactions between and active (Schiff, 1864). In the majority of cases, the synthesis involves an aromatic amine and an aldehyde (Schiff et al., 1881). are very important for production of chemical specialties such as pharmaceuticals including antibiotics, and of antiallergic, antitumor, antifungal, antibacterial, antimalarial or antiviral drugs. are also employed as catalyst carriers (Grigoras et al., 2001), thermo-stable materials (Vančo et al., 2004), metal–cation complexing agents or in biological systems (Taggi et al., 2002). containing phenol indicate two possible tautomeric forms, viz. phenol–imine and keto–enamine.
contain the azomethine moiety (–In the current study, a new Schiff base, (Z)-6-{[(2-hydroxy-4-methylphenyl)amino]methylidene}-4-methylcyclohexa-2,4-dien-1-one, was obtained in crystalline form from the reaction of 2-amino-5-methylphenol with 2-hydroxy-5-methylbenzaldehyde. We report here its synthesis conditions and the molecular and crystal structures, supplemented by Hirshfeld surface analysis.
2. Structural commentary
The molecular structure of the title compound is illustrated in Fig. 1. The comprises one molecule that adopts the keto–enamine tautomeric form, i.e. the H atom is located at the amine functionality (N1). The molecule is almost planar, with an r.m.s. deviation of 0.1061 Å for the complete molecule except the H atoms [largest deviation 0.176 (3) Å for C8]. The two phenyl rings (C1–C6 and C9–C14) are inclined by 9.60 (18)°. The C1—O1 bond length [1.356 (3) Å] to the hydroxy group is in the normal range, while the C14=O2 bond length is comparatively elongated [1.302 (4) Å] due to the involvement of the carbonyl O atom in an intramolecular N—H⋯O hydrogen bond, forming an S(6) ring motif. The C6—N1 and C8=N1 bond lengths are 1.404 (4) and 1.310 (4) Å, respectively. Overall, the bond lengths in the title structure compare well with those of other keto–enamine tautomers known from the literature (see: Database Survey).
3. Supramolecular features
The molecules are linked by mutual O—H⋯O hydrogen bonds forming pairs of inversion dimers with an (18) ring motif (Table 1, Figs. 2 and 3). The dimers are linked by very weak π-stacking interactions [Cg1⋯Cg2 = 4.721 (2) Å; Cg1 and Cg2 are the centroids of the C1–C6 and C9–C14 rings, respectively], forming layers parallel to (01).
4. Database survey
A search of the Cambridge Structural Database (CSD, version 5.40, update November 2018; Groom et al., 2016) for the (E)-2-[(2-hydroxyphenyliminio)methyl]phenolate fragment revealed 25 hits where this fragment adopts the keto–enamine tautomeric form. Nearly all bond lengths in the title structure are the same within standard uncertainties as the corresponding bond lengths in the structures of 2,4-dichloro-6-{[(2-methoxyphenyl)iminio]methyl}phenolate hydrate (VUYFEC; Tsuchimoto et al., 2016), 2-{(E)-[(2-hydroxyphenyl)iminio]methyl}-4-methylphenolate (XULSOO; Shalini et al., 2015), (E)-4-hydroxy-2-[(2-hydroxyphenyl)iminiomethyl]phenolate (QUYGOH; Eltayeb et al., 2010) or 2-{(E)-[(2-hydroxy-5-methylphenyl)iminio]methyl}-4-(trifluoromethoxy)phenolate (QAJYUX; Karadağ et al., 2011). For example, in the structures of these typical keto–enamine tautomers, the corresponding C14=O2 and C8—C9 bond lengths are in the ranges 1.279–1.316 Å and 1.410–1.427 Å, respectively. It is likely that the intermolecular O—H⋯O hydrogen bond, where the keto O atom acts as an hydrogen-bond acceptor, is an important prerequisite for the tautomeric shift toward the keto–enamine form. In fact, in all 25 structures of the keto–enamine tautomers, hydrogen bonds of this type are observed.
5. Hirshfeld surface analysis
A Hirshfeld surface analysis (Spackman & Jayatilaka, 2009) and the associated two-dimensional fingerprint plots (McKinnon et al., 2007) were performed with CrystalExplorer17 (Turner et al., 2017) for specifying the intermolecular interactions in the title compound. Fig. 4a illustrates the Hirshfeld surface mapped over dnorm. The red spots highlight the interatomic contacts included in O—H⋯O hydrogen bonding. The three-dimensional dnorm surfaces were plotted with a colour scale of −0.7370 to 1.3366 Å with a standard (high) surface resolution. Fig. 4b shows the molecular electrostatic potential plotted over the three-dimensional Hirshfeld surface using the STO-3G basis set in the range −0.0975 to 0.2197 a.u. within the Hartree–Fock level of theory. The O—H⋯O hydrogen-bond donors and acceptors are shown as blue and red areas around the atoms related with positive (hydrogen-bond donors) and negative (hydrogen-bond acceptors) electrostatic potentials, respectively.
Fig. 5a shows the two-dimensional fingerprint of the sum of all contacts contributing to the Hirshfeld surface indicated in normal mode. Fig. 5b illustrates the two-dimensional fingerprint of (di, de) points related to H⋯H contacts that represent a 55.2% contribution in the title structure. In Fig. 5c, two symmetrical wings on the left and right sides indicate C⋯H/H⋯C interactions with a contribution of 22.3%. Furthermore, there are O⋯H/H⋯O (13.6%; Fig. 5d), C⋯C (4.9%) and C⋯N/N⋯C (2.6%) contacts.
Fig. 6 shows the molecular electrostatic potential surface generated using the STO-3G basis set in the range −0.050 to 0.050 a.u. within the Hartree–Fock level of theory. The blue and red regions are associated with positive and negative molecular electrostatic potentials and represent the donor and acceptor groups, respectively, in hydrogen bonding.
6. Synthesis and crystallization
The title compound was prepared by refluxing a mixture of 2-hydroxy-5-methylbenzaldehyde (34.0 mg, 0.25 mmol) in ethanol (15 ml) and 2-amino-5-methylphenol (30.8 mg, 0.25 mmol) in ethanol (15 ml) for 5 h. Single crystals of the title compound for X-ray analysis were obtained by slow evaporation of an ethanol solution (yield 65%, m.p. 446–448 K).
7. Refinement
Crystal data, data collection and structure . The O- and N-bound H atoms were located in a difference-Fourier map and refined with O—H = 0.82 Å and N—H = 0.85 Å, and with Uiso(H) = 1.5Ueq(N,O). The C-bound H atoms were positioned geometrically and refined using a riding model with C—H = 0.93 and Uiso(H) = 1.2Ueq(C) for aromatic H atoms, and with C—H = 0.96 Å and Uiso(H) = 1.5Ueq(C) for methyl H atoms.
details are summarized in Table 2Supporting information
CCDC reference: 1902148
https://doi.org/10.1107/S2056989019006583/wm5504sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989019006583/wm5504Isup2.hkl
Data collection: X-AREA (Stoe & Cie, 2002); cell
X-AREA (Stoe & Cie, 2002); data reduction: X-RED (Stoe & Cie, 2002); program(s) used to solve structure: SHELXT2017 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: WinGX (Farrugia, 2012), SHELXL2018 (Sheldrick, 2015b), PLATON (Spek, 2009) and publCIF (Westrip, 2010).C15H15NO2 | F(000) = 512 |
Mr = 241.28 | Dx = 1.292 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 11.3954 (19) Å | Cell parameters from 15101 reflections |
b = 11.746 (2) Å | θ = 2.8–30.9° |
c = 10.3067 (17) Å | µ = 0.09 mm−1 |
β = 115.940 (12)° | T = 296 K |
V = 1240.6 (4) Å3 | Prism, red |
Z = 4 | 0.57 × 0.50 × 0.44 mm |
Stoe IPDS 2 diffractometer | 2417 independent reflections |
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus | 1261 reflections with I > 2σ(I) |
Detector resolution: 6.67 pixels mm-1 | Rint = 0.061 |
rotation method scans | θmax = 26.0°, θmin = 2.8° |
Absorption correction: integration (X-RED32; Stoe & Cie, 2002) | h = −14→13 |
Tmin = 0.962, Tmax = 0.975 | k = −14→11 |
6997 measured reflections | l = −12→12 |
Refinement on F2 | Hydrogen site location: mixed |
Least-squares matrix: full | H atoms treated by a mixture of independent and constrained refinement |
R[F2 > 2σ(F2)] = 0.064 | w = 1/[σ2(Fo2) + (0.0717P)2] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.156 | (Δ/σ)max < 0.001 |
S = 0.99 | Δρmax = 0.16 e Å−3 |
2417 reflections | Δρmin = −0.14 e Å−3 |
171 parameters | Extinction correction: SHELXL2017 (Sheldrick, 2015b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.007 (2) |
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. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.3892 (2) | 0.58075 (18) | 0.4721 (3) | 0.0775 (7) | |
H1 | 0.379271 | 0.539357 | 0.530605 | 0.116* | |
O2 | 0.6238 (2) | 0.57505 (18) | 0.3518 (2) | 0.0735 (7) | |
N1 | 0.4922 (3) | 0.7437 (3) | 0.3822 (3) | 0.0581 (7) | |
C9 | 0.6549 (3) | 0.7665 (2) | 0.2975 (3) | 0.0544 (7) | |
C1 | 0.3454 (3) | 0.6868 (3) | 0.4791 (3) | 0.0563 (7) | |
C8 | 0.5565 (3) | 0.8082 (3) | 0.3317 (3) | 0.0599 (8) | |
H8 | 0.536018 | 0.885293 | 0.317983 | 0.072* | |
C6 | 0.3978 (3) | 0.7746 (2) | 0.4288 (3) | 0.0546 (7) | |
C2 | 0.2544 (3) | 0.7113 (3) | 0.5301 (3) | 0.0613 (8) | |
H2A | 0.219587 | 0.652120 | 0.562261 | 0.074* | |
C3 | 0.2140 (3) | 0.8211 (3) | 0.5343 (3) | 0.0592 (8) | |
C11 | 0.8287 (3) | 0.8104 (3) | 0.2270 (3) | 0.0603 (8) | |
C14 | 0.6898 (3) | 0.6484 (3) | 0.3155 (3) | 0.0599 (8) | |
C10 | 0.7254 (3) | 0.8436 (3) | 0.2515 (3) | 0.0628 (8) | |
H10 | 0.700067 | 0.919577 | 0.237683 | 0.075* | |
C5 | 0.3571 (3) | 0.8851 (3) | 0.4324 (3) | 0.0642 (8) | |
H5 | 0.390952 | 0.944514 | 0.399559 | 0.077* | |
C4 | 0.2668 (3) | 0.9080 (3) | 0.4843 (3) | 0.0670 (8) | |
H4 | 0.240644 | 0.982737 | 0.485967 | 0.080* | |
C12 | 0.8638 (3) | 0.6949 (3) | 0.2488 (3) | 0.0681 (9) | |
H12 | 0.934719 | 0.670249 | 0.234291 | 0.082* | |
C13 | 0.7972 (3) | 0.6170 (3) | 0.2906 (3) | 0.0688 (9) | |
H13 | 0.823971 | 0.541368 | 0.302935 | 0.083* | |
C7 | 0.1151 (3) | 0.8461 (3) | 0.5909 (3) | 0.0762 (10) | |
H7A | 0.031563 | 0.816866 | 0.524800 | 0.114* | |
H7B | 0.109049 | 0.926922 | 0.600598 | 0.114* | |
H7C | 0.141812 | 0.810509 | 0.683322 | 0.114* | |
C15 | 0.9064 (3) | 0.8936 (3) | 0.1829 (4) | 0.0769 (10) | |
H15A | 0.861304 | 0.965184 | 0.157474 | 0.115* | |
H15B | 0.916047 | 0.863810 | 0.101333 | 0.115* | |
H15C | 0.990962 | 0.904493 | 0.261813 | 0.115* | |
H1A | 0.516 (4) | 0.673 (4) | 0.387 (4) | 0.088 (12)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.1026 (18) | 0.0475 (13) | 0.1056 (17) | 0.0073 (13) | 0.0671 (15) | 0.0093 (11) |
O2 | 0.0894 (16) | 0.0526 (13) | 0.0949 (14) | −0.0002 (12) | 0.0555 (13) | 0.0079 (11) |
N1 | 0.0611 (17) | 0.0488 (17) | 0.0674 (15) | 0.0035 (14) | 0.0308 (13) | 0.0064 (12) |
C9 | 0.0583 (18) | 0.0501 (18) | 0.0558 (16) | 0.0016 (15) | 0.0259 (15) | 0.0034 (13) |
C1 | 0.0612 (19) | 0.0484 (18) | 0.0586 (16) | 0.0013 (16) | 0.0254 (15) | 0.0019 (13) |
C8 | 0.0620 (19) | 0.0505 (18) | 0.0669 (17) | −0.0019 (16) | 0.0281 (15) | 0.0050 (14) |
C6 | 0.0550 (18) | 0.0498 (18) | 0.0602 (16) | 0.0033 (15) | 0.0262 (14) | 0.0031 (13) |
C2 | 0.068 (2) | 0.056 (2) | 0.0655 (17) | −0.0049 (16) | 0.0342 (16) | 0.0039 (14) |
C3 | 0.0591 (19) | 0.063 (2) | 0.0557 (16) | 0.0044 (17) | 0.0251 (14) | 0.0027 (14) |
C11 | 0.063 (2) | 0.063 (2) | 0.0601 (16) | −0.0045 (17) | 0.0318 (15) | −0.0012 (14) |
C14 | 0.065 (2) | 0.0535 (19) | 0.0620 (16) | −0.0024 (16) | 0.0288 (15) | −0.0002 (14) |
C10 | 0.067 (2) | 0.0563 (19) | 0.0648 (17) | −0.0033 (17) | 0.0283 (16) | 0.0005 (14) |
C5 | 0.0658 (19) | 0.0512 (19) | 0.0800 (19) | −0.0004 (17) | 0.0359 (17) | 0.0060 (15) |
C4 | 0.072 (2) | 0.0526 (19) | 0.084 (2) | 0.0078 (17) | 0.0406 (18) | 0.0011 (16) |
C12 | 0.071 (2) | 0.069 (2) | 0.0735 (19) | 0.0016 (18) | 0.0400 (17) | −0.0055 (16) |
C13 | 0.082 (2) | 0.0532 (19) | 0.081 (2) | 0.0030 (18) | 0.0450 (19) | −0.0030 (16) |
C7 | 0.073 (2) | 0.085 (3) | 0.078 (2) | 0.0082 (19) | 0.0403 (18) | 0.0022 (17) |
C15 | 0.078 (2) | 0.081 (3) | 0.084 (2) | −0.011 (2) | 0.0477 (19) | −0.0013 (18) |
O1—C1 | 1.356 (3) | C11—C10 | 1.365 (4) |
O1—H1 | 0.8200 | C11—C12 | 1.405 (4) |
O2—C14 | 1.302 (4) | C11—C15 | 1.516 (4) |
N1—C8 | 1.310 (4) | C14—C13 | 1.404 (4) |
N1—C6 | 1.404 (4) | C10—H10 | 0.9300 |
N1—H1A | 0.87 (4) | C5—C4 | 1.377 (4) |
C9—C8 | 1.403 (4) | C5—H5 | 0.9300 |
C9—C10 | 1.422 (4) | C4—H4 | 0.9300 |
C9—C14 | 1.433 (4) | C12—C13 | 1.373 (4) |
C1—C2 | 1.383 (4) | C12—H12 | 0.9300 |
C1—C6 | 1.400 (4) | C13—H13 | 0.9300 |
C8—H8 | 0.9300 | C7—H7A | 0.9600 |
C6—C5 | 1.385 (4) | C7—H7B | 0.9600 |
C2—C3 | 1.377 (4) | C7—H7C | 0.9600 |
C2—H2A | 0.9300 | C15—H15A | 0.9600 |
C3—C4 | 1.393 (4) | C15—H15B | 0.9600 |
C3—C7 | 1.506 (4) | C15—H15C | 0.9600 |
C1—O1—H1 | 109.5 | C11—C10—C9 | 122.6 (3) |
C8—N1—C6 | 129.1 (3) | C11—C10—H10 | 118.7 |
C8—N1—H1A | 111 (2) | C9—C10—H10 | 118.7 |
C6—N1—H1A | 120 (2) | C4—C5—C6 | 120.6 (3) |
C8—C9—C10 | 119.4 (3) | C4—C5—H5 | 119.7 |
C8—C9—C14 | 120.9 (2) | C6—C5—H5 | 119.7 |
C10—C9—C14 | 119.6 (3) | C5—C4—C3 | 121.2 (3) |
O1—C1—C2 | 124.5 (3) | C5—C4—H4 | 119.4 |
O1—C1—C6 | 115.5 (2) | C3—C4—H4 | 119.4 |
C2—C1—C6 | 120.0 (3) | C13—C12—C11 | 122.4 (3) |
N1—C8—C9 | 123.0 (3) | C13—C12—H12 | 118.8 |
N1—C8—H8 | 118.5 | C11—C12—H12 | 118.8 |
C9—C8—H8 | 118.5 | C12—C13—C14 | 121.9 (3) |
C5—C6—C1 | 118.5 (3) | C12—C13—H13 | 119.1 |
C5—C6—N1 | 124.6 (3) | C14—C13—H13 | 119.1 |
C1—C6—N1 | 116.8 (3) | C3—C7—H7A | 109.5 |
C3—C2—C1 | 121.6 (3) | C3—C7—H7B | 109.5 |
C3—C2—H2A | 119.2 | H7A—C7—H7B | 109.5 |
C1—C2—H2A | 119.2 | C3—C7—H7C | 109.5 |
C2—C3—C4 | 118.0 (3) | H7A—C7—H7C | 109.5 |
C2—C3—C7 | 120.8 (3) | H7B—C7—H7C | 109.5 |
C4—C3—C7 | 121.2 (3) | C11—C15—H15A | 109.5 |
C10—C11—C12 | 117.0 (3) | C11—C15—H15B | 109.5 |
C10—C11—C15 | 122.4 (3) | H15A—C15—H15B | 109.5 |
C12—C11—C15 | 120.5 (3) | C11—C15—H15C | 109.5 |
O2—C14—C13 | 122.6 (3) | H15A—C15—H15C | 109.5 |
O2—C14—C9 | 121.0 (3) | H15B—C15—H15C | 109.5 |
C13—C14—C9 | 116.4 (3) | ||
C6—N1—C8—C9 | 175.8 (3) | C10—C9—C14—C13 | 2.3 (4) |
C10—C9—C8—N1 | −176.2 (3) | C12—C11—C10—C9 | 0.1 (4) |
C14—C9—C8—N1 | 0.5 (4) | C15—C11—C10—C9 | −177.9 (3) |
O1—C1—C6—C5 | 179.8 (3) | C8—C9—C10—C11 | 174.9 (3) |
C2—C1—C6—C5 | 0.4 (4) | C14—C9—C10—C11 | −1.8 (4) |
O1—C1—C6—N1 | −2.2 (4) | C1—C6—C5—C4 | −0.1 (4) |
C2—C1—C6—N1 | 178.4 (3) | N1—C6—C5—C4 | −177.9 (3) |
C8—N1—C6—C5 | −1.7 (5) | C6—C5—C4—C3 | 0.0 (5) |
C8—N1—C6—C1 | −179.5 (3) | C2—C3—C4—C5 | −0.2 (4) |
O1—C1—C2—C3 | 180.0 (3) | C7—C3—C4—C5 | −179.9 (3) |
C6—C1—C2—C3 | −0.7 (4) | C10—C11—C12—C13 | 1.0 (5) |
C1—C2—C3—C4 | 0.6 (4) | C15—C11—C12—C13 | 179.1 (3) |
C1—C2—C3—C7 | −179.7 (3) | C11—C12—C13—C14 | −0.5 (5) |
C8—C9—C14—O2 | 6.1 (4) | O2—C14—C13—C12 | 178.3 (3) |
C10—C9—C14—O2 | −177.2 (3) | C9—C14—C13—C12 | −1.2 (4) |
C8—C9—C14—C13 | −174.4 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O2i | 0.82 | 1.82 | 2.627 (3) | 168 |
N1—H1A···O2 | 0.87 (4) | 1.83 (4) | 2.585 (4) | 144 (3) |
Symmetry code: (i) −x+1, −y+1, −z+1. |
Funding information
This study was supported by Ondokuz Mayıs University under Project No. PYO·FEN.1906.19.001.
References
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