Crystal structure and DFT study of the zwitterionic form of 3-{(E)-1-[(4-ethoxyphenyl)iminiumyl]ethyl}-6-methyl-2-oxo-2H-pyran-4-olate

Djedouani, A.; Anak, B.; Tabti, S.; Cleymand, F.; François, M.; Fleutot, S.

doi:10.1107/S2056989018000919

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ISSN: 2056-9890

Volume 74| Part 2| February 2018| Pages 172-175

https://doi.org/10.1107/S2056989018000919

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Crystal structure and DFT study of the zwitterionic form of 3-{(E)-1-[(4-ethoxyphenyl)iminiumyl]ethyl}-6-methyl-2-oxo-2H-pyran-4-olate

Amel Djedouani,^a,^b ^* Barkahem Anak,^c,^b Salima Tabti,^d Franck Cleymand,^e Michel François ^e and Solenne Fleutot ^e

^aLaboratoire de Physicochimie Analytique et Cristallochimie de Matériaux Organométalliques et Biomoléculaires, Université de Constantine 1, 25000 Constantine, Algeria, ^bEcole Normale Supérieure de Constantine Assia Djebbar, Ville Universitaire Ali Mendjeli, Constantine 25000, Algeria, ^cLaboratoire de Chimie des Matériaux, Université de Constantine 1, 25000 Constantine, Algeria, ^dUniversité Bachire El Ibrahimi de Bordj Bou Arraridj, Algeria, and ^eInstitut Jean Lamour UMR 7198, Parc de Saurupt, CS 14234 F 54042 Nancy, France
^*Correspondence e-mail: djedouani_amel@yahoo.fr

Edited by J. Ellena, Universidade de Sâo Paulo, Brazil (Received 18 December 2017; accepted 15 January 2018; online 16 January 2018)

The title Schiff base compound, C₁₆H₁₇NO₄, crystallizes as a zwitterion, with the phenolic H atom having been transferred to the imino group. The resulting iminium and hydroxy groups are linked by an intramolecular N—H⋯O hydrogen bond, enclosing an S(6) ring motif. The conformation about the C=N bond is E and the dihedral angle between the benzene and pyran rings is 70.49 (6)°. In the crystal, molecules are linked by C—H⋯O hydrogen bonds, forming a three-dimensional supramolecular structure. There are also C—H⋯π interactions and offset π–π interactions, involving the pyran rings [intercentroid distance = 3.4156 (8) Å], which consolidate the three-dimensional structure. Quantum chemical calculations of the molecule are in good agreement with the solid state keto–amine (NH) form of the title compound.

Keywords: crystal structure; Schiff base; zwitterion; hydrogen bonding; C—H⋯π interactions; π–π interactions.

CCDC reference: 1816916

1. Chemical context

Hydroxy Schiff bases have been studied extensively for their biological, photochromic and thermochromic properties (Garnovskii et al., 1993 ; Hadjoudis et al., 2004 ). They can be used as potential materials for optical memory and switch devices (Zhao et al., 2007 ). Proton transfer in these compounds forms the basis for an explanation of the mechanisms of various biological processes where proton transfer is the rate-determining step (Lussier et al., 1987 ). In general, O-hydroxy Schiff bases exhibit two possible tautomeric forms, the phenol–imine (or benzenoid) and keto–amine (or quinoid) forms. Depending on the tautomers, two types of intramolecular hydrogen bonds are possible: O—H⋯N in benzenoid and N—H⋯O in quinoid tautomers. O-hydroxy Schiff bases have been observed in the keto form, in the enol form or in an enol/keto mixture (Nazır et al., 2000 ; Antonov et al., 2000 ) due to the H-atom transfer. Another form of the Schiff base compounds is their zwitterionic form (Ogawa & Harada, 2003 ). Zwitterions of Schiff bases have an ionic intramolecular hydrogen bond (N⁺—H⋯O⁻) and their N⁺—H bond lengths are longer than the normal bond length observed for neutral N—H bonds (0.87 Å). The molecular structure of the title compound is similar to that of (E)-4-hydroxy-3-[N-(4-hydroxyphenyl)ethanimidoyl]-6-methyl-2H-pyran-2-one (Djedouani et al., 2015 ), which also crystallizes as a zwitterion.

2. Structural commentary

The molecular structure of title compound is shown in Fig. 1. It crystallizes in the zwitterionic form, with the phenolic H atom having been transferred to the imino group. The H atom, H1N, was located in a difference-Fourier map and freely refined (N—H = 0.90 (2) Å). The resulting iminium and hydroxy groups are linked by an intramolecular N—H⋯O hydrogen bond forming an S(6) loop (Fig. 1 and Table 1). The dihedral angle between the benzene (C9–C14) and pyran (O3/C2–C6) rings is 70.49 (6)°. The carbon–nitrogen bond N1=C7 is 1.318 (2) Å, which agrees with values observed in related compounds (Girija & Begum, 2004 ; Girija et al., 2004 ). It is slightly longer than a typical C=N bond [1.283 (4) Å; Bai & Jing, 2007 ], but much shorter than a C—N bond. The N1—C9 bond length is 1.436 (2) Å because of resonance. The carbon–carbon bond connecting the enol and imine groups exhibits intermediate distances between those of single and double bond, but being closer to the latter; C5—C7 = 1.427 (2) and C5—C6 = 1.443 (2) Å, reflecting the zwitterionic character of the title compound (Wojciechowski et al., 2003 ). The C4—O1 bond length [1.259 (2) Å] is intermediate between single and double carbon-to-oxygen bond lengths (1.362 and 1.222 Å, respectively), whereas C6—O2 is 1.215 (2) Å.

Table 1
Hydrogen-bond geometry (Å, °)

Cg1 is the centroid of the C9–C14 benzene ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1N⋯O1	0.90 (2)	1.74 (2)	2.5411 (15)	147 (2)
C1—H1B⋯O3ⁱ	0.98	2.57	3.4461 (18)	149
C8—H8B⋯O2ⁱⁱ	0.98	2.62	3.3478 (17)	132
C10—H10⋯O1ⁱⁱⁱ	0.95	2.56	3.2035 (16)	125
C13—H13⋯O2^iv	0.95	2.46	3.3950 (17)	170
C15—H15A⋯Cg1^v	0.99	2.74	3.618 (2)	149
Symmetry codes: (i) -x+1, -y, -z; (ii) $[-x+1, y, -z+{\script{1\over 2}}]$ ; (iii) $[-x+{\script{1\over 2}}, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (iv) $[x, -y+1, z+{\script{1\over 2}}]$ ; (v) $[-x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z+1]$ .

Figure 1
A view of the molecular structure of the title compound with the atom labelling. Displacement ellipsoids are drawn at the 50% probability level, and the intramolecular N—H⋯O hydrogen bond (see Table 1

) is shown as a dashed line.

The aromatic ring and dehydroacetic acid ring are in a trans position with respect to the C7=N1 bond, the dihedral angle between the two rings is 70.46 (9)° and the molecular conformation is determined by the presence of the intramolecular N⁺—H⋯O⁻ hydrogen bond (Fig. 1 and Table 1), which generates an S(6) ring motif. Similar intramolecular hydrogen bonds have been reported in other zwitterionic phenolates (Huang et al., 2006 ; Temel et al., 2006 ).

3. Supramolecular features

In the crystal, molecules are linked by C—H⋯O hydrogen bonds, forming a three-dimensional supramolecular structure (Fig. 2 and Table 1), which is consolidated by C—H⋯π interactions (Table 1) and offset π–π interactions. The latter involve symmetry-related pyran rings with a Cg⋯Cgⁱ distance of 3.416 (1) Å [Cg is the centroid of ring O3/C2–C6, interplanar distance = 3.319 (1) Å, offset = 0.81 Å, symmetry code (i): −x + 1, y, −z + $[{1\over 2}]$ ].

Figure 2
A view along the b axis of the crystal packing of the title compound. The hydrogen bonds are shown as dashed lines (see Table 1

), and only the H atoms involved in hydrogen bonding have been included.

4. Database survey

A search of the Cambridge Structural Database (Version 5.38, update May 2017; Groom et al., 2016 ) for similar structures revealed the presence of three zwitterionic compounds of interest, namely (E)-6- methyl-2-oxo-3-[1-(p-tolyliminio)ethyl]-2H-pyran-4-olate (REZMAL; Djedouani et al., 2007 ) and 6-methyl-2-oxo-3-[1-(ureidoiminio)ethyl]-2H-pyran-4-olate monohydrate (HOFPOI; Djedouani et al., 2008 ) and (E)-4-hydroxy-3-[N-(4-hydroxyphenyl)ethanimidoyl]-6-methyl-2H-pyran-2-one (CUGPAX; Djedouani et al., 2015). The molecular conformations of all three compounds are also determined by the presence of an intramolecular charge-assisted N⁺—H⋯O⁻ hydrogen bond (see Fig. 1 and Table 1 for the title compound), which generates an S(6) ring motif. Two of these compounds, REZMAL and CUGPAX, have a benzene ring inclined to the pyran ring by 42.25 (10) and 53.31 (11)°, respectively. This is significantly different from the equivalent dihedral angle of 70.46 (9)° in the title compound, which has five hydrogen bonds, two from the ethoxy group in the para position of the benzene and another from the benzene ring, which has increased the dihedral angle between the two rings. On the other hand, CUGPAX has three hydrogen bonds and only one single bond of the hydroxy group in the para position of benzene ring, and the dihedral angle between the two rings is 53.31 (11)°. REZMAL shows only two hydrogen bonds, neither of which involve benzene ring, and the dihedral angle is 42.25 (10)°.

5. Density functional study – geometry optimization and molecular orbital calculations

Geometry optimization and molecular orbital calculations were carried out with the Guassian09 software package (Frisch et al., 2009 ) and the Gaussview visualization program (Dennington et al., 2007 ; Rassolov et al., 1998 ), using the three-parameter hybrid function of Becke based on the correlation function (B3LYP) of Lee et al. (1998 ) and Miehlich et al. (1989 ), with the 6-311G, 6-311G(+) and 6-311G(++) basis sets. The bond lengths, bond angles corresponding to the optimized geometry obtained using the DFT/B3LY P method are given in Table 2. The calculated C4—C5 bond distance is 1.447 Å correlates nicely with experimental value. The calculated bond lengths with B3LYP/6-311G(++) level are slightly shorter than the experimental values within 0.004–0.035 Å. The calculated bond angles C5—C4—O4 and C4—C5—C7 are close to 120° since atoms C4 and C5 have sp² hybridization. In general, the calculated values are in good agreement with the experimental data.

Table 2
DFT and X-ray geometric parameters (Å, °) for the title compound

	B3LYP/6–311g(++)	X-ray data
N1—C7	1.334	1.318 (2)
C5—C7	1.423	1.427 (2)
C5—C4	1.447	1.447 (2)
C4—O1	1.253	1.259 (2)
C7—C8	1.460	1.495 (2)

H1N—N1—C7	112.29	112.0 (11)
N1—C7—C5	118.07	118.27 (13)
C4—C5—C7	120.75	120.58 (12)
C5—C4—O4	123.27	123.19 (13)

The highest occupied molecular orbitals (HOMO) and lowest unoccupied orbitals (LUMO) are named frontier orbitals (FMOs). The calculated values at the B3LYP/6-311G(++) level are presented in Table 3, and the nature of the frontier molecular orbitals for the two possible tautomeric forms, the keto–amine (NH) and the phenol–imine (OH) forms of zwitterionic forms of Schiff bases, are plotted in Fig. 3. The band-gap energy values calculated for keto–amine (NH) forms were found to be 4.297 eV, which is a large HOMO–LUMO energy gap, implying a higher molecular stability than for the phenol–imine (OH) form, which has a smaller energy gap with the difference between the HOMO and LUMO being 3.791 eV. The HOMO–LUMO energy gap is very important for the chemical activity and explains the eventual charge-transfer interaction within the molecule. Clearly, the larger HOMO–LUMO gap calculated for the keto–amine (NH) form is in agreement with the stability of the molecule in the solid state.

Table 3
Frontier molecular orbital energies (eV): HOMO–LUMO gap of the keto–amine (NH) and phenol–imine (OH) forms of the title compound

Energy	keto–amine (NH) form	phenol–imine (OH) form
E_HOMO	6.167	5.491
E_LUMO	1.870	1.700
E_gap	4.297	3.791

Figure 3
The frontier molecular orbitals for the two possible tautomeric forms, the keto–amine (NH) and the phenol–imine (OH) forms, of the title Schiff base compound.

6. Synthesis and crystallization

The title compound was prepared according to a literature method (Djedouani et al., 2007). Colourless plate-like crystals were obtained by slow evaporation of a solution in ethanol.

7. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 4. The NH H atom was located in a difference-Fourier map and freely refined. The C-bound H atoms were included in calculated positions and treated as riding: C—H = 0.95–0.99 Å, with U_iso(H) = 1.5U_eq(C-methyl) and 1.2U_eq(C) for other H atoms.

Table 4
Experimental details

Crystal data
Chemical formula	C₁₆H₁₇NO₄
M_r	287.30
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	100
a, b, c (Å)	21.0983 (13), 7.7792 (5), 17.7036 (11)
β (°)	105.564 (2)
V (Å³)	2799.1 (3)
Z	8
Radiation type	Mo Kα
μ (mm⁻¹)	0.10
Crystal size (mm)	0.18 × 0.08 × 0.03

Data collection
Diffractometer	Bruker APEXII QUAZAR CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2004 )
T_min, T_max	0.596, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	17108, 2750, 2315
R_int	0.037
(sin θ/λ)_max (Å⁻¹)	0.617

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.035, 0.094, 1.07
No. of reflections	2750
No. of parameters	197
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.23, −0.21
Computer programs: APEX2 and SAINT (Bruker, 2004), SHELXS2016/6 (Sheldrick, 2008 ), SHELXL2016/6 (Sheldrick, 2015 ), Mercury (Macrae et al., 2008 ), PLATON (Spek, 2009 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 1816916

Crystal structure: contains datablocks I, _Global. DOI: https://doi.org/10.1107/S2056989018000919/ex2003sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989018000919/ex2003Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989018000919/ex2003Isup3.cml

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS2016/6 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2016/6 (Sheldrick, 2015); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL2016/6 (Sheldrick, 2015), PLATON (Spek, 2009) and publCIF (Westrip, 2010).

3-{(E)-1-[(4-Ethoxyphenyl)iminiumyl]ethyl}-6-methyl-2-oxo-2H-pyran-4-olate top

Crystal data top

C₁₆H₁₇NO₄	F(000) = 1216
M_r = 287.30	D_x = 1.364 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 21.0983 (13) Å	Cell parameters from 18962 reflections
b = 7.7792 (5) Å	θ = 2.0–27.5°
c = 17.7036 (11) Å	µ = 0.10 mm⁻¹
β = 105.564 (2)°	T = 100 K
V = 2799.1 (3) Å³	Plate, colorless
Z = 8	0.18 × 0.08 × 0.03 mm

Data collection top

Bruker APEXII QUAZAR CCD diffractometer	2750 independent reflections
Radiation source: ImuS	2315 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.037
f\ and ω scans	θ_max = 26.0°, θ_min = 2.0°
Absorption correction: multi-scan (SADABS; Bruker, 2004)	h = −16→26
T_min = 0.596, T_max = 0.746	k = −9→9
17108 measured reflections	l = −21→21

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.035	Hydrogen site location: mixed
wR(F²) = 0.094	H atoms treated by a mixture of independent and constrained refinement
S = 1.07	w = 1/[σ²(F_o²) + (0.0419P)² + 2.3424P] where P = (F_o² + 2F_c²)/3
2750 reflections	(Δ/σ)_max < 0.001
197 parameters	Δρ_max = 0.23 e Å⁻³
0 restraints	Δρ_min = −0.21 e Å⁻³

Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
O1	0.37595 (5)	−0.09851 (12)	0.25430 (5)	0.0178 (2)
O2	0.46409 (5)	0.36094 (13)	0.13692 (6)	0.0223 (2)
O3	0.48126 (5)	0.09177 (13)	0.11188 (5)	0.0203 (2)
O4	0.28470 (5)	0.53164 (13)	0.53959 (6)	0.0195 (2)
N1	0.35473 (6)	0.20560 (15)	0.29392 (7)	0.0167 (3)
H1N	0.3533 (9)	0.090 (2)	0.2929 (10)	0.033 (5)*
C1	0.51239 (8)	−0.1830 (2)	0.07643 (9)	0.0261 (4)
H1A	0.558974	−0.151115	0.094154	0.039*
H1B	0.495675	−0.158824	0.020257	0.039*
H1C	0.507565	−0.305845	0.085797	0.039*
C2	0.47443 (7)	−0.08168 (19)	0.12051 (8)	0.0186 (3)
C3	0.43857 (7)	−0.14438 (18)	0.16567 (8)	0.0179 (3)
H3	0.433601	−0.265332	0.168807	0.021*
C4	0.40712 (6)	−0.03355 (17)	0.20989 (8)	0.0154 (3)
C5	0.41363 (6)	0.14995 (17)	0.20071 (7)	0.0153 (3)
C6	0.45203 (6)	0.21302 (18)	0.15026 (8)	0.0169 (3)
C7	0.38639 (6)	0.26807 (18)	0.24515 (8)	0.0162 (3)
C8	0.39081 (7)	0.45891 (18)	0.23821 (8)	0.0203 (3)
H8C	0.374124	0.492541	0.183088	0.031*
H8B	0.436806	0.495022	0.257827	0.031*
H8A	0.364402	0.514294	0.269172	0.031*
C9	0.33460 (7)	0.29881 (17)	0.35356 (8)	0.0164 (3)
C10	0.26863 (7)	0.30913 (17)	0.35148 (8)	0.0171 (3)
H10	0.236228	0.263353	0.308090	0.020*
C11	0.24977 (7)	0.38655 (17)	0.41296 (8)	0.0173 (3)
H11	0.204561	0.393367	0.411788	0.021*
C12	0.29738 (7)	0.45369 (17)	0.47593 (8)	0.0166 (3)
C13	0.36385 (7)	0.44554 (18)	0.47719 (8)	0.0193 (3)
H13	0.396300	0.493437	0.519946	0.023*
C14	0.38224 (7)	0.36797 (18)	0.41637 (8)	0.0186 (3)
H14	0.427417	0.361699	0.417316	0.022*
C15	0.21698 (7)	0.56107 (18)	0.53868 (8)	0.0193 (3)
H15A	0.192613	0.451001	0.533117	0.023*
H15B	0.195276	0.637069	0.494438	0.023*
C16	0.21851 (7)	0.64530 (19)	0.61584 (9)	0.0224 (3)
H16A	0.245376	0.749760	0.622067	0.034*
H16B	0.237520	0.565599	0.658818	0.034*
H16C	0.173613	0.675273	0.616796	0.034*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0187 (5)	0.0183 (5)	0.0179 (5)	−0.0034 (4)	0.0075 (4)	0.0023 (4)
O2	0.0232 (5)	0.0233 (5)	0.0203 (5)	−0.0055 (4)	0.0056 (4)	0.0058 (4)
O3	0.0226 (5)	0.0243 (5)	0.0155 (5)	−0.0066 (4)	0.0077 (4)	−0.0002 (4)
O4	0.0167 (5)	0.0222 (5)	0.0200 (5)	0.0015 (4)	0.0058 (4)	−0.0013 (4)
N1	0.0170 (6)	0.0156 (6)	0.0179 (6)	−0.0009 (5)	0.0052 (5)	0.0022 (5)
C1	0.0239 (8)	0.0343 (9)	0.0214 (8)	−0.0039 (7)	0.0083 (6)	−0.0058 (6)
C2	0.0168 (7)	0.0232 (7)	0.0133 (7)	−0.0027 (6)	−0.0003 (6)	−0.0006 (6)
C3	0.0180 (7)	0.0186 (7)	0.0155 (7)	−0.0022 (6)	0.0017 (6)	0.0012 (5)
C4	0.0116 (6)	0.0202 (7)	0.0121 (6)	−0.0029 (5)	−0.0008 (5)	0.0018 (5)
C5	0.0125 (6)	0.0188 (7)	0.0122 (6)	−0.0023 (5)	−0.0008 (5)	0.0024 (5)
C6	0.0139 (7)	0.0232 (7)	0.0108 (6)	−0.0028 (6)	−0.0016 (5)	0.0022 (5)
C7	0.0118 (6)	0.0199 (7)	0.0135 (7)	−0.0020 (5)	−0.0022 (5)	0.0035 (5)
C8	0.0221 (7)	0.0183 (7)	0.0197 (7)	−0.0007 (6)	0.0040 (6)	0.0036 (5)
C9	0.0183 (7)	0.0137 (6)	0.0175 (7)	0.0006 (5)	0.0056 (6)	0.0039 (5)
C10	0.0170 (7)	0.0148 (6)	0.0175 (7)	−0.0012 (5)	0.0012 (6)	0.0031 (5)
C11	0.0146 (7)	0.0164 (7)	0.0209 (7)	0.0020 (5)	0.0045 (6)	0.0038 (5)
C12	0.0199 (7)	0.0141 (6)	0.0166 (7)	0.0022 (5)	0.0063 (6)	0.0026 (5)
C13	0.0170 (7)	0.0197 (7)	0.0198 (7)	−0.0002 (6)	0.0024 (6)	−0.0001 (6)
C14	0.0137 (7)	0.0213 (7)	0.0210 (7)	0.0010 (6)	0.0048 (6)	0.0030 (6)
C15	0.0165 (7)	0.0189 (7)	0.0238 (8)	0.0021 (5)	0.0079 (6)	0.0037 (6)
C16	0.0221 (7)	0.0211 (7)	0.0266 (8)	0.0021 (6)	0.0112 (6)	0.0024 (6)

Geometric parameters (Å, º) top

O1—C4	1.2585 (16)	C8—H8C	0.9800
O2—C6	1.2154 (17)	C8—H8B	0.9800
O3—C2	1.3698 (17)	C8—H8A	0.9800
O3—C6	1.3988 (18)	C9—C10	1.385 (2)
O4—C12	1.3680 (16)	C9—C14	1.392 (2)
O4—C15	1.4427 (16)	C10—C11	1.392 (2)
N1—C7	1.3182 (18)	C10—H10	0.9500
N1—C9	1.4358 (18)	C11—C12	1.387 (2)
N1—H1N	0.902 (19)	C11—H11	0.9500
C1—C2	1.486 (2)	C12—C13	1.398 (2)
C1—H1A	0.9800	C13—C14	1.378 (2)
C1—H1B	0.9800	C13—H13	0.9500
C1—H1C	0.9800	C14—H14	0.9500
C2—C3	1.332 (2)	C15—C16	1.508 (2)
C3—C4	1.440 (2)	C15—H15A	0.9900
C3—H3	0.9500	C15—H15B	0.9900
C4—C5	1.4474 (19)	C16—H16A	0.9800
C5—C7	1.427 (2)	C16—H16B	0.9800
C5—C6	1.4431 (19)	C16—H16C	0.9800
C7—C8	1.4946 (19)

C2—O3—C6	122.46 (11)	H8C—C8—H8A	109.5
C12—O4—C15	118.24 (11)	H8B—C8—H8A	109.5
C7—N1—C9	126.68 (12)	C10—C9—C14	120.28 (13)
C7—N1—H1N	112.0 (11)	C10—C9—N1	120.22 (12)
C9—N1—H1N	120.3 (11)	C14—C9—N1	119.34 (12)
C2—C1—H1A	109.5	C9—C10—C11	120.03 (13)
C2—C1—H1B	109.5	C9—C10—H10	120.0
H1A—C1—H1B	109.5	C11—C10—H10	120.0
C2—C1—H1C	109.5	C12—C11—C10	119.60 (13)
H1A—C1—H1C	109.5	C12—C11—H11	120.2
H1B—C1—H1C	109.5	C10—C11—H11	120.2
C3—C2—O3	121.42 (13)	O4—C12—C11	124.71 (13)
C3—C2—C1	126.45 (14)	O4—C12—C13	115.09 (12)
O3—C2—C1	112.10 (12)	C11—C12—C13	120.19 (13)
C2—C3—C4	121.71 (13)	C14—C13—C12	119.94 (13)
C2—C3—H3	119.1	C14—C13—H13	120.0
C4—C3—H3	119.1	C12—C13—H13	120.0
O1—C4—C3	119.56 (12)	C13—C14—C9	119.95 (13)
O1—C4—C5	123.19 (13)	C13—C14—H14	120.0
C3—C4—C5	117.25 (12)	C9—C14—H14	120.0
C7—C5—C6	119.89 (12)	O4—C15—C16	106.17 (11)
C7—C5—C4	120.58 (12)	O4—C15—H15A	110.5
C6—C5—C4	119.38 (13)	C16—C15—H15A	110.5
O2—C6—O3	113.66 (12)	O4—C15—H15B	110.5
O2—C6—C5	128.60 (14)	C16—C15—H15B	110.5
O3—C6—C5	117.73 (12)	H15A—C15—H15B	108.7
N1—C7—C5	118.27 (13)	C15—C16—H16A	109.5
N1—C7—C8	118.28 (13)	C15—C16—H16B	109.5
C5—C7—C8	123.44 (12)	H16A—C16—H16B	109.5
C7—C8—H8C	109.5	C15—C16—H16C	109.5
C7—C8—H8B	109.5	H16A—C16—H16C	109.5
H8C—C8—H8B	109.5	H16B—C16—H16C	109.5
C7—C8—H8A	109.5

C6—O3—C2—C3	0.80 (19)	C4—C5—C7—N1	−0.68 (18)
C6—O3—C2—C1	−177.59 (11)	C6—C5—C7—C8	4.91 (19)
O3—C2—C3—C4	−2.3 (2)	C4—C5—C7—C8	−179.52 (12)
C1—C2—C3—C4	175.89 (13)	C7—N1—C9—C10	119.67 (15)
C2—C3—C4—O1	−177.10 (12)	C7—N1—C9—C14	−64.93 (18)
C2—C3—C4—C5	2.62 (19)	C14—C9—C10—C11	−1.0 (2)
O1—C4—C5—C7	2.5 (2)	N1—C9—C10—C11	174.36 (12)
C3—C4—C5—C7	−177.19 (12)	C9—C10—C11—C12	0.3 (2)
O1—C4—C5—C6	178.11 (12)	C15—O4—C12—C11	−5.99 (19)
C3—C4—C5—C6	−1.60 (18)	C15—O4—C12—C13	173.59 (12)
C2—O3—C6—O2	178.87 (11)	C10—C11—C12—O4	−179.66 (12)
C2—O3—C6—C5	0.19 (18)	C10—C11—C12—C13	0.8 (2)
C7—C5—C6—O2	−2.5 (2)	O4—C12—C13—C14	179.28 (12)
C4—C5—C6—O2	−178.17 (13)	C11—C12—C13—C14	−1.1 (2)
C7—C5—C6—O3	175.91 (11)	C12—C13—C14—C9	0.4 (2)
C4—C5—C6—O3	0.28 (18)	C10—C9—C14—C13	0.7 (2)
C9—N1—C7—C5	167.68 (12)	N1—C9—C14—C13	−174.74 (12)
C9—N1—C7—C8	−13.4 (2)	C12—O4—C15—C16	179.27 (11)
C6—C5—C7—N1	−176.26 (12)

Hydrogen-bond geometry (Å, º) top

Cg1 is the centroid of the C9–C14 benzene ring.

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N···O1	0.90 (2)	1.74 (2)	2.5411 (15)	147 (2)
C1—H1B···O3ⁱ	0.98	2.57	3.4461 (18)	149
C8—H8B···O2ⁱⁱ	0.98	2.62	3.3478 (17)	132
C10—H10···O1ⁱⁱⁱ	0.95	2.56	3.2035 (16)	125
C13—H13···O2^iv	0.95	2.46	3.3950 (17)	170
C15—H15A···Cg1^v	0.99	2.74	3.618 (2)	149

Symmetry codes: (i) −x+1, −y, −z; (ii) −x+1, y, −z+1/2; (iii) −x+1/2, y+1/2, −z+1/2; (iv) x, −y+1, z+1/2; (v) −x+1/2, −y+1/2, −z+1.

DFT and X-ray geometric parameters (Å, °) for the title compound top

	B3LYP/6-311g(++)	X-ray data
N1—C7	1.334	1.318 (2)
C5—C7	1.423	1.427 (2)
C5—C4	1.447	1.447 (2)
C4—O1	1.253	1.259 (2)
C7—C8	1.460	1.495 (2)

H1N—N1—C7	112.29	112.0 (11)
N1—C7—C5	118.07	118.27 (13)
C4—C5—C7	120.75	120.58 (12)
C5—C4—O4	123.27	123.19 (13)

Frontier molecular orbital energies (eV): HOMO–LUMO gap of the keto–amine (NH) and phenol–imine (OH) forms of the title compound top

Energy	keto–amine (NH) form	phenol–imine (OH) form
E_HOMO	6.167	5.491
E_LUMO	1.870	1.700
E_gap	4.297	3.791

Acknowledgements

The authors acknowledge the Algerian Ministry of Higher Education and Scientific Research, and the Algerian Directorate General for Scientific Research and Technological Development for support of this work.

Funding information

We are grateful to the Algerien Ministère de l'Enseignement Supérieur de la Recherche Scientifique and the Algerian Direction Générale de la Recherche Scientifique et du Développement Technologique, for financial support.

References

Antonov, L., Fabian, W. M. F., Nedeltcheva, D. & Kamounah, F. S. (2000). J. Chem. Soc. Perkin Trans. 2, pp. 1173–1179. CrossRef Google Scholar
Bai, Z.-C. & Jing, Z.-L. (2007). Acta Cryst. E63, o3822. Web of Science CSD CrossRef IUCr Journals Google Scholar
Bruker (2004). SMART, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Dennington, R., Keith, T. & Millam, J. (2007). Gaussview4.1. Semichem Inc., Shawnee Mission, KS, USA. Google Scholar
Djedouani, A., Bendaas, A., Boufas, S., Allain, M., Bouet, G. & Khan, M. (2007). Acta Cryst. E63, o1271–o1273. Web of Science CSD CrossRef IUCr Journals Google Scholar
Djedouani, A., Boufas, S., Allain, M., Bouet, G. & Khan, M. (2008). Acta Cryst. E64, o1785. Web of Science CSD CrossRef IUCr Journals Google Scholar
Djedouani, A., Boufas, S., Cleymand, F., François, M. & Fleutot, S. (2015). Acta Cryst. E71, o564–o565. Web of Science CSD CrossRef IUCr Journals Google Scholar
Frisch, M. J., et al. (2009). GAUSSIAN09. Gaussian Inc., Wallingford, CT, USA. Google Scholar
Garnovskii, A. D., Nivorozhkin, A. L. & Minkin, V. I. (1993). Coord. Chem. Rev. 126, 1–69. CrossRef CAS Web of Science Google Scholar
Girija, C. R. & Begum, N. S. (2004). Acta Cryst. E60, o535–o536. Web of Science CSD CrossRef IUCr Journals Google Scholar
Girija, C. R., Begum, N. S., Sridhar, M. A., Lokanath, N. K. & Prasad, J. S. (2004). Acta Cryst. E60, o586–o588. Web of Science CSD CrossRef IUCr Journals Google Scholar
Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171–179. Web of Science CSD CrossRef IUCr Journals Google Scholar
Hadjoudis, E., Rontoyianni, A., Ambroziak, K., Dziembowska, T. & Mavridis, I. M. (2004). J. Photochem. Photobiol. Chem. 162, 521–530. Web of Science CSD CrossRef CAS Google Scholar
Huang, L., Chen, D.-B., Qiu, D. & Zhao, B. (2006). Acta Cryst. E62, o5239–o5240. Web of Science CSD CrossRef IUCr Journals Google Scholar
Lee, C., Yang, W. & Parr, R. G. (1998). Phys. Rev. 37, 785–789. CrossRef Web of Science Google Scholar
Lussier, L. S., Sandorfy, C., Le Thanh Hoa & Vocelle, D. (1987). J. Phys. Chem. 91, 2282–2287. Google Scholar
Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466–470. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Miehlich, B., Savin, A., Stoll, H. & Preuss, H. (1989). Chem. Phys. Lett. 157, 200–206. CrossRef CAS Web of Science Google Scholar
Nazır, H., Yıldız, M., Yılmaz, H., Tahir, M. N. & Ülkü, D. (2000). J. Mol. Struct. 524, 241–250. Web of Science CSD CrossRef CAS Google Scholar
Ogawa, K. & Harada, J. (2003). J. Mol. Struct. 647, 211–216. Web of Science CrossRef CAS Google Scholar
Rassolov, V. A., Pople, J. A., Ratner, M. A. & Windus, T. L. (1998). J. Chem. Phys. 109, 1223–1229. Web of Science CrossRef CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Temel, E., Albayrak, Ç., Büyükgüngör, O. & Odabaşoğlu, M. (2006). Acta Cryst. E62, o4484–o4486. Web of Science CSD CrossRef IUCr Journals Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar
Wojciechowski, G., Ratajczak-Sitarz, M., Katrusiak, A., Schilf, W., Przybylski, P. & Brzezinski, B. (2003). J. Mol. Struct. 650, 191–199. Web of Science CSD CrossRef CAS Google Scholar
Zhao, L., Hou, Q., Sui, D., Wang, Y. & Jiang, S. (2007). Spectrochim. Acta A, 67, 1120–1125. Web of Science CrossRef Google Scholar

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Volume 74| Part 2| February 2018| Pages 172-175

https://doi.org/10.1107/S2056989018000919

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research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Crystal structure and DFT study of the zwitterionic form of 3-{(E)-1-[(4-ethoxyphenyl)iminiumyl]ethyl}-6-methyl-2-oxo-2H-pyran-4-olate

1. Chemical context

2. Structural commentary

3. Supra­molecular features

4. Database survey

5. Density functional study – geometry optimization and mol­ecular orbital calculations

6. Synthesis and crystallization

7. Refinement

Supporting information

Acknowledgements

Funding information

References

research communications

3. Supramolecular features

5. Density functional study – geometry optimization and molecular orbital calculations