(E)-2-{[1-Carb-oxy-2-(1H-indol-3-yl)ethyl-iminio]meth-yl}-6-hy-droxy-phenolate.

In the zwitterionic title compound, C(18)H(16)N(2)O(4), the dihedral angle between the planes of the benzene and indole rings is 26.38 (10)°. An intra-molecular N-H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, mol-ecules are linked through N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds into infinite chains propagating in [010].

Related literature

For a related structure and background to Schiff bases, see: Ba-Salamah et al. (2011 ▶). For other related structures, see: Eltayeb et al. (2010a ▶,b ▶,c ▶). For reference bond lengths, see: Allen et al. (1987 ▶). For graph-set theory, see: Bernstein et al. (1995 ▶).

Experimental

Crystal data

C18H16N2O4

M = 324.33

Monoclinic,

a = 8.4351 (2) Å

b = 9.3038 (3) Å

c = 9.5023 (3) Å

β = 98.683 (2)°

V = 737.18 (4) Å3

Z = 2

Mo Kα radiation

μ = 0.11 mm−1

T = 100 K

0.32 × 0.22 × 0.20 mm

Data collection

Bruker SMART APEXII CCD diffractometer

Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T min = 0.598, T max = 0.746

7473 measured reflections

1949 independent reflections

1781 reflections with I > 2σ(I)

R int = 0.046

Refinement

R[F 2 > 2σ(F 2)] = 0.038

wR(F 2) = 0.093

S = 1.14

1949 reflections

233 parameters

1 restraint

H atoms treated by a mixture of independent and constrained refinement

Δρmax = 0.27 e Å−3

Δρmin = −0.23 e Å−3

Data collection: APEX2 (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ▶).

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811031709/hb6347sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811031709/hb6347Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

C18H16N2O4	F(000) = 340
Mr = 324.33	Dx = 1.461 Mg m−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2yb	Cell parameters from 1920 reflections
a = 8.4351 (2) Å	θ = 3.0–27.7°
b = 9.3038 (3) Å	µ = 0.11 mm−1
c = 9.5023 (3) Å	T = 100 K
β = 98.683 (2)°	Block, orange
V = 737.18 (4) Å3	0.32 × 0.22 × 0.20 mm
Z = 2

Bruker SMART APEXII CCD diffractometer	1949 independent reflections
Radiation source: fine-focus sealed tube	1781 reflections with I > 2σ(I)
graphite	Rint = 0.046
φ and ω scans	θmax = 28.4°, θmin = 2.2°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −11→11
Tmin = 0.598, Tmax = 0.746	k = −12→12
7473 measured reflections	l = −12→12

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)] = 0.038	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.093	H atoms treated by a mixture of independent and constrained refinement
S = 1.14	w = 1/[σ2(Fo2) + (0.0454P)2 + 0.0637P] where P = (Fo2 + 2Fc2)/3
1949 reflections	(Δ/σ)max < 0.001
233 parameters	Δρmax = 0.27 e Å−3
1 restraint	Δρmin = −0.23 e Å−3

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.

	x	y	z	Uiso*/Ueq
O1	−0.07419 (19)	−0.1334 (2)	0.34014 (17)	0.0232 (4)
O2	−0.0062 (2)	−0.1221 (2)	0.12218 (17)	0.0211 (4)
O3	0.21206 (18)	0.18228 (18)	−0.05777 (17)	0.0182 (3)
O4	0.3782 (2)	0.2819 (2)	−0.27523 (17)	0.0208 (4)
N1	0.2349 (2)	0.0546 (2)	0.1933 (2)	0.0153 (4)
N2	−0.1227 (2)	0.4135 (2)	0.2298 (2)	0.0195 (4)
C1	0.4611 (3)	0.1047 (2)	0.0751 (2)	0.0155 (4)
C2	0.3695 (3)	0.1726 (2)	−0.0437 (2)	0.0170 (5)
C3	0.4555 (3)	0.2223 (3)	−0.1530 (2)	0.0171 (5)
C4	0.6201 (3)	0.2052 (3)	−0.1389 (3)	0.0197 (5)
H4	0.6748	0.2395	−0.2126	0.024*
C5	0.7084 (3)	0.1396 (3)	−0.0203 (3)	0.0201 (5)
H5	0.8216	0.1306	−0.0129	0.024*
C6	0.6296 (3)	0.0881 (3)	0.0856 (3)	0.0189 (5)
H6	0.6881	0.0413	0.1659	0.023*
C7	0.3873 (3)	0.0479 (3)	0.1886 (2)	0.0159 (4)
H7	0.4539	0.0024	0.2653	0.019*
C8	0.1609 (3)	−0.0021 (3)	0.3116 (2)	0.0155 (4)
H8	0.2412	−0.0673	0.3675	0.019*
C9	0.0139 (3)	−0.0931 (3)	0.2577 (2)	0.0163 (5)
C10	0.1237 (3)	0.1170 (3)	0.4127 (2)	0.0170 (4)
H10A	0.0851	0.0722	0.4957	0.020*
H10B	0.2245	0.1686	0.4482	0.020*
C11	0.0013 (3)	0.2246 (3)	0.3481 (2)	0.0172 (5)
C12	−0.1594 (3)	0.2345 (3)	0.3819 (2)	0.0158 (4)
C13	−0.2460 (3)	0.1543 (3)	0.4697 (2)	0.0182 (5)
H13	−0.1991	0.0732	0.5208	0.022*
C14	−0.4016 (3)	0.1962 (3)	0.4803 (3)	0.0200 (5)
H14	−0.4619	0.1427	0.5389	0.024*
C15	−0.4712 (3)	0.3162 (3)	0.4059 (3)	0.0227 (5)
H15	−0.5772	0.3437	0.4167	0.027*
C16	−0.3889 (3)	0.3954 (3)	0.3172 (3)	0.0205 (5)
H16	−0.4373	0.4754	0.2654	0.025*
C17	−0.2323 (3)	0.3536 (3)	0.3065 (2)	0.0176 (5)
C18	0.0167 (3)	0.3350 (3)	0.2562 (2)	0.0189 (5)
H18	0.1109	0.3548	0.2160	0.023*
H1N1	0.171 (3)	0.093 (4)	0.108 (3)	0.034 (8)*
H1N2	−0.141 (3)	0.490 (4)	0.171 (3)	0.024 (7)*
H1O2	−0.084 (4)	−0.187 (4)	0.102 (3)	0.033 (8)*
H1O4	0.273 (4)	0.292 (4)	−0.278 (3)	0.046 (10)*

	U11	U22	U33	U12	U13	U23
O1	0.0195 (8)	0.0321 (10)	0.0189 (8)	−0.0065 (7)	0.0056 (6)	0.0020 (8)
O2	0.0196 (8)	0.0255 (10)	0.0191 (8)	−0.0075 (7)	0.0058 (6)	−0.0043 (7)
O3	0.0124 (7)	0.0216 (8)	0.0210 (8)	0.0019 (6)	0.0043 (6)	0.0020 (7)
O4	0.0162 (8)	0.0266 (9)	0.0208 (8)	0.0010 (7)	0.0069 (7)	0.0035 (7)
N1	0.0142 (9)	0.0166 (9)	0.0157 (9)	0.0013 (7)	0.0039 (7)	0.0001 (8)
N2	0.0194 (10)	0.0179 (10)	0.0228 (10)	0.0010 (8)	0.0087 (8)	0.0028 (9)
C1	0.0137 (10)	0.0168 (11)	0.0166 (10)	−0.0014 (8)	0.0039 (8)	−0.0031 (9)
C2	0.0143 (10)	0.0162 (11)	0.0208 (11)	0.0007 (8)	0.0041 (8)	−0.0019 (9)
C3	0.0169 (10)	0.0152 (11)	0.0197 (11)	−0.0008 (9)	0.0047 (8)	−0.0017 (9)
C4	0.0170 (11)	0.0221 (13)	0.0218 (11)	−0.0026 (9)	0.0086 (9)	−0.0004 (10)
C5	0.0121 (10)	0.0234 (12)	0.0250 (11)	−0.0021 (9)	0.0037 (9)	−0.0021 (10)
C6	0.0146 (10)	0.0225 (12)	0.0191 (11)	−0.0006 (9)	0.0012 (8)	0.0003 (10)
C7	0.0159 (10)	0.0144 (10)	0.0169 (10)	−0.0006 (8)	0.0006 (8)	−0.0024 (9)
C8	0.0136 (10)	0.0182 (11)	0.0149 (10)	0.0002 (9)	0.0028 (8)	0.0010 (9)
C9	0.0122 (10)	0.0162 (11)	0.0203 (11)	0.0004 (8)	0.0022 (8)	0.0021 (9)
C10	0.0150 (10)	0.0200 (12)	0.0165 (10)	0.0012 (9)	0.0040 (8)	−0.0001 (9)
C11	0.0166 (10)	0.0182 (11)	0.0170 (10)	−0.0010 (9)	0.0032 (8)	−0.0026 (9)
C12	0.0150 (10)	0.0177 (11)	0.0152 (10)	−0.0004 (9)	0.0043 (8)	−0.0036 (9)
C13	0.0195 (11)	0.0182 (12)	0.0171 (10)	0.0007 (9)	0.0038 (8)	−0.0011 (9)
C14	0.0181 (11)	0.0202 (12)	0.0230 (11)	−0.0031 (9)	0.0080 (9)	−0.0011 (10)
C15	0.0166 (11)	0.0228 (13)	0.0300 (13)	−0.0003 (9)	0.0074 (9)	−0.0049 (11)
C16	0.0188 (11)	0.0161 (11)	0.0272 (12)	0.0033 (8)	0.0054 (9)	−0.0002 (10)
C17	0.0182 (11)	0.0168 (11)	0.0189 (11)	−0.0017 (9)	0.0065 (8)	−0.0021 (9)
C18	0.0166 (11)	0.0207 (12)	0.0200 (11)	−0.0007 (9)	0.0048 (9)	−0.0036 (10)

O1—C9	1.218 (3)	C6—H6	0.9500
O2—C9	1.301 (3)	C7—H7	0.9500
O2—H1O2	0.89 (3)	C8—C9	1.525 (3)
O3—C2	1.318 (3)	C8—C10	1.530 (3)
O4—C3	1.361 (3)	C8—H8	1.0000
O4—H1O4	0.89 (3)	C10—C11	1.501 (3)
N1—C7	1.295 (3)	C10—H10A	0.9900
N1—C8	1.465 (3)	C10—H10B	0.9900
N1—H1N1	0.97 (3)	C11—C18	1.367 (4)
N2—C18	1.375 (3)	C11—C12	1.442 (3)
N2—C17	1.378 (3)	C12—C13	1.405 (3)
N2—H1N2	0.90 (3)	C12—C17	1.409 (3)
C1—C2	1.417 (3)	C13—C14	1.387 (3)
C1—C6	1.419 (3)	C13—H13	0.9500
C1—C7	1.426 (3)	C14—C15	1.403 (4)
C2—C3	1.429 (3)	C14—H14	0.9500
C3—C4	1.384 (3)	C15—C16	1.382 (4)
C4—C5	1.395 (3)	C15—H15	0.9500
C4—H4	0.9500	C16—C17	1.396 (3)
C5—C6	1.373 (3)	C16—H16	0.9500
C5—H5	0.9500	C18—H18	0.9500
C9—O2—H1O2	110 (2)	C10—C8—H8	107.0
C3—O4—H1O4	115 (2)	O1—C9—O2	124.9 (2)
C7—N1—C8	123.31 (19)	O1—C9—C8	119.9 (2)
C7—N1—H1N1	115.0 (18)	O2—C9—C8	115.22 (19)
C8—N1—H1N1	121.5 (18)	C11—C10—C8	114.84 (18)
C18—N2—C17	108.2 (2)	C11—C10—H10A	108.6
C18—N2—H1N2	126.3 (17)	C8—C10—H10A	108.6
C17—N2—H1N2	125.5 (17)	C11—C10—H10B	108.6
C2—C1—C6	121.6 (2)	C8—C10—H10B	108.6
C2—C1—C7	121.40 (19)	H10A—C10—H10B	107.5
C6—C1—C7	117.0 (2)	C18—C11—C12	106.1 (2)
O3—C2—C1	122.1 (2)	C18—C11—C10	129.5 (2)
O3—C2—C3	121.2 (2)	C12—C11—C10	124.3 (2)
C1—C2—C3	116.62 (19)	C13—C12—C17	119.6 (2)
O4—C3—C4	118.2 (2)	C13—C12—C11	133.6 (2)
O4—C3—C2	121.44 (19)	C17—C12—C11	106.9 (2)
C4—C3—C2	120.3 (2)	C14—C13—C12	118.5 (2)
C3—C4—C5	122.3 (2)	C14—C13—H13	120.8
C3—C4—H4	118.9	C12—C13—H13	120.8
C5—C4—H4	118.9	C13—C14—C15	121.1 (2)
C6—C5—C4	119.1 (2)	C13—C14—H14	119.5
C6—C5—H5	120.4	C15—C14—H14	119.5
C4—C5—H5	120.4	C16—C15—C14	121.4 (2)
C5—C6—C1	120.1 (2)	C16—C15—H15	119.3
C5—C6—H6	119.9	C14—C15—H15	119.3
C1—C6—H6	119.9	C15—C16—C17	117.7 (2)
N1—C7—C1	123.8 (2)	C15—C16—H16	121.2
N1—C7—H7	118.1	C17—C16—H16	121.2
C1—C7—H7	118.1	N2—C17—C16	130.1 (2)
N1—C8—C9	111.15 (18)	N2—C17—C12	108.1 (2)
N1—C8—C10	111.87 (19)	C16—C17—C12	121.8 (2)
C9—C8—C10	112.33 (18)	C11—C18—N2	110.8 (2)
N1—C8—H8	107.0	C11—C18—H18	124.6
C9—C8—H8	107.0	N2—C18—H18	124.6
C6—C1—C2—O3	176.6 (2)	C9—C8—C10—C11	−61.5 (3)
C7—C1—C2—O3	−2.4 (3)	C8—C10—C11—C18	−75.8 (3)
C6—C1—C2—C3	0.5 (3)	C8—C10—C11—C12	108.5 (3)
C7—C1—C2—C3	−178.4 (2)	C18—C11—C12—C13	−179.4 (2)
O3—C2—C3—O4	0.3 (3)	C10—C11—C12—C13	−2.8 (4)
C1—C2—C3—O4	176.4 (2)	C18—C11—C12—C17	−0.2 (2)
O3—C2—C3—C4	−177.1 (2)	C10—C11—C12—C17	176.4 (2)
C1—C2—C3—C4	−1.0 (3)	C17—C12—C13—C14	−0.5 (3)
O4—C3—C4—C5	−177.2 (2)	C11—C12—C13—C14	178.6 (2)
C2—C3—C4—C5	0.3 (4)	C12—C13—C14—C15	−0.3 (3)
C3—C4—C5—C6	0.9 (4)	C13—C14—C15—C16	1.3 (4)
C4—C5—C6—C1	−1.3 (4)	C14—C15—C16—C17	−1.3 (4)
C2—C1—C6—C5	0.6 (4)	C18—N2—C17—C16	178.8 (2)
C7—C1—C6—C5	179.6 (2)	C18—N2—C17—C12	−0.3 (3)
C8—N1—C7—C1	−179.0 (2)	C15—C16—C17—N2	−178.5 (2)
C2—C1—C7—N1	−0.7 (4)	C15—C16—C17—C12	0.5 (4)
C6—C1—C7—N1	−179.7 (2)	C13—C12—C17—N2	179.6 (2)
C7—N1—C8—C9	−132.3 (2)	C11—C12—C17—N2	0.3 (2)
C7—N1—C8—C10	101.2 (2)	C13—C12—C17—C16	0.4 (3)
N1—C8—C9—O1	−170.5 (2)	C11—C12—C17—C16	−178.9 (2)
C10—C8—C9—O1	−44.3 (3)	C12—C11—C18—N2	0.0 (3)
N1—C8—C9—O2	9.7 (3)	C10—C11—C18—N2	−176.3 (2)
C10—C8—C9—O2	135.9 (2)	C17—N2—C18—C11	0.2 (3)
N1—C8—C10—C11	64.4 (2)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N1···O3	0.97 (3)	1.86 (3)	2.646 (2)	136 (2)
N2—H1N2···O3i	0.90 (3)	2.13 (3)	3.020 (2)	170 (2)
O2—H1O2···O3ii	0.89 (3)	1.64 (4)	2.526 (2)	174 (4)
O4—H1O4···O3	0.89 (3)	2.45 (3)	2.823 (2)	106 (2)
O4—H1O4···O1i	0.89 (3)	1.83 (3)	2.665 (2)	156 (3)
C7—H7···O4iii	0.95	2.49	3.197 (3)	132

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1N1⋯O3	0.97 (3)	1.86 (3)	2.646 (2)	136 (2)
N2—H1N2⋯O3i	0.90 (3)	2.13 (3)	3.020 (2)	170 (2)
O2—H1O2⋯O3ii	0.89 (3)	1.64 (4)	2.526 (2)	174 (4)
O4—H1O4⋯O3	0.89 (3)	2.45 (3)	2.823 (2)	106 (2)
O4—H1O4⋯O1i	0.89 (3)	1.83 (3)	2.665 (2)	156 (3)
C7—H7⋯O4iii	0.95	2.49	3.197 (3)	132

Symmetry codes: (i) ; (ii) ; (iii) .