Quinoxalinium 2,6-dihydroxy­benzoate

In the title salt, C₈H₇N₂⁺·C₇H₅O₄⁻, one of the quinoxaline N atoms is protonated. The cation and anion are nearly coplanar and are connected into a cyclic R₂²(7) motif generated by N—H...O and C—H...O hydrogen bonds. The hydrogen-bonded ionic pairs are arranged into double stacks, in which quinoxalinium and 2,6-dihydroxy­benzoate ions alternate.

Key indicators

• Single-crystal X-ray study
• T = 294 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.041
• wR factor = 0.127
• Data-to-parameter ratio = 13.3

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       2.03
PLAT353_ALERT_3_C Long    N-H Bond (0.87A)   N1     -   H1N    ...       1.07 Ang.
PLAT355_ALERT_3_C Long    O-H Bond (0.82A)   O3A    -   H3OA   ...       1.02 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H6     ..  N4      ..       2.67 Ang.
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          2

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   5 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
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: Stereochemical Workstation Operation Manual (Siemens, 1989) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97.

quinoxalinium 2,6-dihydroxybenzoate

Crystal data

C8H7N2^+·C7H5O4^−	F(000) = 1184
Mr = 284.27	Dx = 1.428 Mg m^−3
Monoclinic, C2/c	Melting point: 393 K
Hall symbol: -C 2yc	Mo Kα radiation, λ = 0.71073 Å
a = 12.0557 (5) Å	Cell parameters from 7496 reflections
b = 9.0755 (4) Å	θ = 2.5–29.5°
c = 24.7931 (10) Å	µ = 0.11 mm^−1
β = 102.872 (3)°	T = 294 K
V = 2644.48 (19) Å^3	Plate, light-brown
Z = 8	0.6 × 0.6 × 0.2 mm

Data collection

Kuma KM-4-CCD κ geometry diffractometer	1935 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.020
Graphite monochromator	θmax = 26.4°, θmin = 4.1°
ω scans	h = −15→13
14871 measured reflections	k = −11→11
2701 independent reflections	l = −30→30

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.041	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.127	w = 1/[σ^2(Fo^2) + (0.0514P)^2 + 1.2986P] where P = (Fo^2 + 2Fc^2)/3
S = 1.09	(Δ/σ)max < 0.001
2701 reflections	Δρmax = 0.15 e Å^−3
203 parameters	Δρmin = −0.15 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0019 (5)

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

	x	y	z	Uiso*/Ueq
N1	0.71111 (12)	0.07788 (17)	0.42705 (5)	0.0571 (4)
H1N	0.6643 (19)	0.120 (2)	0.4556 (10)	0.103 (7)*
C2	0.77627 (16)	−0.0371 (2)	0.43929 (7)	0.0678 (5)
H2	0.7844	−0.0821	0.4737	0.081*
C3	0.83458 (17)	−0.0936 (2)	0.40046 (8)	0.0718 (5)
H3	0.8818	−0.1748	0.4103	0.086*
N4	0.82508 (13)	−0.03669 (18)	0.35128 (6)	0.0680 (4)
C5	0.73804 (19)	0.1463 (2)	0.28515 (8)	0.0745 (6)
H5	0.7744	0.1071	0.2590	0.089*
C6	0.6691 (2)	0.2637 (3)	0.27217 (8)	0.0862 (7)
H6	0.6572	0.3038	0.2368	0.103*
C7	0.6150 (2)	0.3265 (2)	0.31119 (8)	0.0810 (6)
H7	0.5697	0.4095	0.3017	0.097*
C8	0.62814 (17)	0.2674 (2)	0.36280 (7)	0.0660 (5)
H8	0.5913	0.3085	0.3884	0.079*
C9	0.69763 (13)	0.14428 (19)	0.37646 (6)	0.0523 (4)
C10	0.75528 (14)	0.0825 (2)	0.33807 (6)	0.0570 (4)
C1A	0.55856 (12)	0.14053 (18)	0.58511 (6)	0.0484 (4)
C2A	0.48711 (14)	0.2638 (2)	0.57994 (6)	0.0565 (4)
C3A	0.43115 (15)	0.2989 (2)	0.62148 (8)	0.0674 (5)
H3A	0.3826	0.3797	0.6177	0.081*
C4A	0.44808 (16)	0.2131 (2)	0.66825 (7)	0.0695 (5)
H4A	0.4105	0.2371	0.6960	0.083*
C5A	0.51872 (17)	0.0936 (2)	0.67513 (7)	0.0685 (5)
H5A	0.5294	0.0375	0.7073	0.082*
C6A	0.57425 (15)	0.05657 (19)	0.63378 (7)	0.0573 (4)
C7A	0.61814 (14)	0.0978 (2)	0.54123 (6)	0.0570 (4)
O1A	0.60323 (11)	0.17983 (16)	0.49778 (5)	0.0729 (4)
O2A	0.68085 (12)	−0.01277 (16)	0.54706 (5)	0.0790 (4)
O3A	0.47071 (13)	0.35293 (18)	0.53483 (6)	0.0859 (5)
H3OA	0.519 (2)	0.306 (3)	0.5106 (12)	0.130 (9)*
O4A	0.64385 (14)	−0.06200 (16)	0.64183 (6)	0.0878 (5)
H4OA	0.665 (2)	−0.068 (3)	0.6071 (11)	0.110 (8)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0566 (8)	0.0770 (10)	0.0416 (7)	0.0018 (7)	0.0194 (6)	−0.0083 (6)
C2	0.0699 (11)	0.0873 (13)	0.0488 (9)	0.0108 (10)	0.0187 (8)	−0.0011 (9)
C3	0.0724 (12)	0.0804 (13)	0.0669 (11)	0.0101 (10)	0.0244 (9)	−0.0095 (10)
N4	0.0715 (10)	0.0795 (11)	0.0611 (9)	−0.0059 (8)	0.0320 (7)	−0.0196 (8)
C5	0.0953 (14)	0.0864 (14)	0.0523 (10)	−0.0207 (12)	0.0387 (10)	−0.0115 (9)
C6	0.1216 (19)	0.0879 (15)	0.0545 (11)	−0.0133 (14)	0.0308 (11)	0.0078 (10)
C7	0.1029 (16)	0.0754 (13)	0.0664 (12)	0.0025 (12)	0.0226 (11)	0.0048 (10)
C8	0.0744 (12)	0.0722 (12)	0.0548 (10)	0.0002 (9)	0.0216 (8)	−0.0071 (8)
C9	0.0546 (9)	0.0645 (10)	0.0414 (8)	−0.0100 (8)	0.0180 (6)	−0.0102 (7)
C10	0.0613 (10)	0.0677 (11)	0.0476 (8)	−0.0150 (8)	0.0241 (7)	−0.0153 (7)
C1A	0.0449 (8)	0.0617 (9)	0.0415 (7)	−0.0032 (7)	0.0156 (6)	−0.0096 (7)
C2A	0.0503 (9)	0.0730 (11)	0.0477 (8)	0.0036 (8)	0.0142 (7)	−0.0035 (8)
C3A	0.0606 (11)	0.0783 (12)	0.0686 (11)	0.0090 (9)	0.0255 (9)	−0.0125 (9)
C4A	0.0699 (12)	0.0891 (14)	0.0596 (10)	−0.0075 (10)	0.0364 (9)	−0.0195 (9)
C5A	0.0845 (13)	0.0776 (12)	0.0526 (9)	−0.0052 (10)	0.0345 (9)	−0.0015 (8)
C6A	0.0641 (10)	0.0591 (10)	0.0536 (9)	−0.0018 (8)	0.0239 (8)	−0.0040 (7)
C7A	0.0537 (9)	0.0753 (11)	0.0453 (8)	0.0008 (8)	0.0182 (7)	−0.0088 (8)
O1A	0.0793 (9)	0.0999 (10)	0.0468 (6)	0.0164 (8)	0.0295 (6)	0.0029 (6)
O2A	0.0892 (9)	0.0921 (10)	0.0655 (8)	0.0278 (8)	0.0383 (7)	−0.0028 (7)
O3A	0.0899 (10)	0.1070 (12)	0.0650 (8)	0.0384 (9)	0.0265 (7)	0.0197 (8)
O4A	0.1202 (12)	0.0783 (10)	0.0767 (9)	0.0294 (9)	0.0472 (9)	0.0170 (7)

Geometric parameters (Å, º)

N1—C2	1.301 (2)	C9—C10	1.414 (2)
N1—C9	1.368 (2)	C1A—C2A	1.400 (2)
N1—H1N	1.07 (2)	C1A—C6A	1.404 (2)
C2—C3	1.409 (2)	C1A—C7A	1.483 (2)
C2—H2	0.9300	C2A—O3A	1.359 (2)
C3—N4	1.305 (2)	C2A—C3A	1.388 (2)
C3—H3	0.9300	C3A—C4A	1.374 (3)
N4—C10	1.364 (2)	C3A—H3A	0.9300
C5—C6	1.346 (3)	C4A—C5A	1.366 (3)
C5—C10	1.407 (2)	C4A—H4A	0.9300
C5—H5	0.9300	C5A—C6A	1.385 (2)
C6—C7	1.402 (3)	C5A—H5A	0.9300
C6—H6	0.9300	C6A—O4A	1.352 (2)
C7—C8	1.364 (3)	C7A—O2A	1.245 (2)
C7—H7	0.9300	C7A—O1A	1.289 (2)
C8—C9	1.392 (2)	O3A—H3OA	1.02 (3)
C8—H8	0.9300	O4A—H4OA	0.95 (3)
C2—N1—C9	120.62 (14)	N4—C10—C9	121.49 (15)
C2—N1—H1N	120.9 (12)	C5—C10—C9	118.16 (18)
C9—N1—H1N	118.5 (12)	C2A—C1A—C6A	118.34 (13)
N1—C2—C3	119.99 (17)	C2A—C1A—C7A	122.04 (15)
N1—C2—H2	120.0	C6A—C1A—C7A	119.62 (15)
C3—C2—H2	120.0	O3A—C2A—C3A	117.91 (16)
N4—C3—C2	122.75 (19)	O3A—C2A—C1A	121.66 (14)
N4—C3—H3	118.6	C3A—C2A—C1A	120.43 (16)
C2—C3—H3	118.6	C4A—C3A—C2A	119.39 (17)
C3—N4—C10	117.30 (14)	C4A—C3A—H3A	120.3
C6—C5—C10	120.27 (17)	C2A—C3A—H3A	120.3
C6—C5—H5	119.9	C5A—C4A—C3A	121.78 (15)
C10—C5—H5	119.9	C5A—C4A—H4A	119.1
C5—C6—C7	120.94 (19)	C3A—C4A—H4A	119.1
C5—C6—H6	119.5	C4A—C5A—C6A	119.39 (17)
C7—C6—H6	119.5	C4A—C5A—H5A	120.3
C8—C7—C6	120.9 (2)	C6A—C5A—H5A	120.3
C8—C7—H7	119.6	O4A—C6A—C5A	118.05 (16)
C6—C7—H7	119.6	O4A—C6A—C1A	121.30 (14)
C7—C8—C9	118.79 (17)	C5A—C6A—C1A	120.66 (16)
C7—C8—H8	120.6	O2A—C7A—O1A	122.04 (14)
C9—C8—H8	120.6	O2A—C7A—C1A	120.43 (15)
N1—C9—C8	121.24 (14)	O1A—C7A—C1A	117.53 (16)
N1—C9—C10	117.82 (16)	C2A—O3A—H3OA	103.8 (16)
C8—C9—C10	120.94 (15)	C6A—O4A—H4OA	101.1 (15)
N4—C10—C5	120.34 (15)
C2A—C1A—C7A—O2A	−179.77 (16)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O4A—H4OA···O2A	0.95 (3)	1.62 (3)	2.5273 (18)	157 (2)
O3A—H3OA···O1A	1.02 (3)	1.61 (3)	2.5531 (18)	152 (3)
N1—H1N···O1A	1.07 (2)	1.51 (2)	2.5765 (17)	177 (2)
N1—H1N···O2A	1.07 (2)	2.54 (2)	3.1852 (18)	118.3 (15)
C6—H6···N4^i	0.93	2.67	3.571 (2)	164
C2—H2···O2A	0.93	2.51	3.143 (2)	126
C2—H2···O3A^ii	0.93	2.49	3.103 (2)	124

Symmetry codes: (i) −x+3/2, y+1/2, −z+1/2; (ii) x+1/2, y−1/2, z.