(E,E)-4-Hydr­oxy-3-methoxy­benzaldehyde azine

The title compound, C₁₆H₁₆N₂O₄, contains two vanillin aromatic rings, which are bridged by a C=N—N=C unit. There are two half-mol­ecules in the asymmetric unit; the mid-points of the N—N bonds lie on centres of symmetry. The mol­ecular structure is stabilized by two intra­molecular O—H...O and inter­molecular O—H...O and O—H...N hydrogen bonds.

Key indicators

• Single-crystal X-ray study
• T = 292 K
• Mean [sigma](C-C)= 0.002 Å
• R factor = 0.042
• wR factor = 0.117
• Data-to-parameter ratio = 14.3

checkCIF/PLATON results

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Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997a); molecular graphics: SHELXTL (Sheldrick, 1997b); software used to prepare material for publication: SHELXTL.

(E,E)-4-Hydroxy-3-methoxybenzaldehyde azine

Crystal data

C16H16N2O4	F(000) = 632
Mr = 300.31	Dx = 1.351 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3000 reflections
a = 11.6941 (8) Å	θ = 2.0–28.4°
b = 7.5492 (5) Å	µ = 0.10 mm^−1
c = 16.7683 (12) Å	T = 292 K
β = 94.169 (1)°	Block, yellow
V = 1476.41 (18) Å^3	0.36 × 0.33 × 0.30 mm
Z = 4

Data collection

Bruker SMART CCD area-detector diffractometer	2905 independent reflections
Radiation source: fine-focus sealed tube	2573 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.047
φ and ω scans	θmax = 26.0°, θmin = 1.8°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −14→14
Tmin = 0.971, Tmax = 0.971	k = −8→9
12220 measured reflections	l = −20→20

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)] = 0.042	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.117	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0725P)^2 + 0.1651P] where P = (Fo^2 + 2Fc^2)/3
2905 reflections	(Δ/σ)max < 0.001
203 parameters	Δρmax = 0.18 e Å^−3
0 restraints	Δρmin = −0.22 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	0.66795 (19)	0.4278 (3)	0.49558 (14)	0.0873 (7)
C2	1.01028 (13)	0.83209 (19)	0.43616 (9)	0.0538 (4)
C3	0.83179 (11)	0.41874 (18)	0.42008 (8)	0.0439 (3)
C4	0.87042 (12)	0.58421 (18)	0.44377 (8)	0.0462 (3)
C5	0.96476 (12)	0.65944 (18)	0.40990 (8)	0.0473 (3)
C6	1.01723 (12)	0.5664 (2)	0.35152 (9)	0.0552 (4)
C7	0.97863 (12)	0.3992 (2)	0.32810 (9)	0.0551 (4)
C8	0.88803 (11)	0.32391 (18)	0.36279 (8)	0.0443 (3)
C9	0.65566 (12)	0.2693 (2)	0.20614 (10)	0.0582 (4)
C10	0.40458 (10)	0.10424 (15)	0.43595 (6)	0.0343 (3)
C11	0.45800 (10)	0.26816 (15)	0.23087 (7)	0.0331 (3)
C12	0.47801 (10)	0.20697 (15)	0.30823 (7)	0.0352 (3)
C13	0.38654 (10)	0.18237 (15)	0.35657 (6)	0.0339 (3)
C14	0.27598 (11)	0.22508 (17)	0.32687 (7)	0.0386 (3)
C15	0.25633 (10)	0.29107 (18)	0.24966 (7)	0.0399 (3)
C16	0.34615 (10)	0.31513 (15)	0.20202 (6)	0.0336 (3)
N1	0.96999 (11)	0.91975 (16)	0.49266 (8)	0.0580 (3)
N2	0.50030 (8)	0.03368 (13)	0.46082 (5)	0.0325 (2)
O1	0.74100 (9)	0.33069 (14)	0.44868 (7)	0.0609 (3)
O2	0.85337 (9)	0.15802 (13)	0.33983 (6)	0.0547 (3)
O3	0.53890 (7)	0.29012 (13)	0.17738 (5)	0.0438 (3)
O4	0.32559 (7)	0.38795 (13)	0.12836 (5)	0.0428 (2)
H1A	0.7097	0.4649	0.5441	0.131*
H1B	0.6046	0.3547	0.5082	0.131*
H1C	0.6397	0.5301	0.4663	0.131*
H2	1.0711	0.8798	0.4105	0.065*
H4	0.8336	0.6461	0.4824	0.055*
H6	1.0790	0.6165	0.3277	0.066*
H7	1.0144	0.3381	0.2887	0.066*
H9A	0.6722	0.3457	0.2513	0.087*
H9B	0.7044	0.2996	0.1646	0.087*
H9C	0.6692	0.1485	0.2220	0.087*
H10	0.3448	0.1056	0.4696	0.041*
H12	0.5525	0.1820	0.3283	0.042*
H14	0.2149	0.2095	0.3587	0.046*
H15	0.1821	0.3191	0.2301	0.048*
H2A	0.8045	0.1231	0.3688	0.082*
H4A	0.3867	0.4125	0.1099	0.064*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0878 (13)	0.0708 (12)	0.1098 (15)	−0.0253 (10)	0.0523 (12)	−0.0298 (11)
C2	0.0531 (8)	0.0446 (8)	0.0615 (9)	−0.0081 (6)	−0.0107 (7)	0.0093 (7)
C3	0.0424 (7)	0.0409 (7)	0.0478 (7)	−0.0009 (5)	−0.0012 (5)	0.0008 (5)
C4	0.0495 (7)	0.0404 (7)	0.0480 (7)	0.0011 (6)	−0.0016 (6)	−0.0013 (5)
C5	0.0455 (7)	0.0431 (7)	0.0513 (7)	−0.0022 (6)	−0.0109 (6)	0.0067 (6)
C6	0.0435 (7)	0.0626 (9)	0.0590 (8)	−0.0080 (7)	0.0011 (6)	0.0040 (7)
C7	0.0455 (7)	0.0632 (10)	0.0568 (8)	0.0008 (7)	0.0048 (6)	−0.0095 (7)
C8	0.0406 (7)	0.0438 (7)	0.0469 (7)	0.0021 (5)	−0.0076 (5)	−0.0046 (5)
C9	0.0384 (7)	0.0679 (10)	0.0699 (9)	0.0125 (6)	0.0145 (6)	0.0301 (8)
C10	0.0412 (6)	0.0356 (6)	0.0264 (5)	0.0017 (5)	0.0045 (4)	−0.0004 (4)
C11	0.0369 (6)	0.0313 (6)	0.0314 (6)	0.0003 (4)	0.0048 (4)	0.0032 (4)
C12	0.0354 (6)	0.0361 (6)	0.0336 (6)	0.0032 (5)	−0.0008 (4)	0.0058 (5)
C13	0.0420 (6)	0.0326 (6)	0.0268 (5)	0.0019 (5)	0.0016 (4)	0.0017 (4)
C14	0.0376 (6)	0.0448 (7)	0.0339 (6)	0.0018 (5)	0.0070 (5)	0.0053 (5)
C15	0.0329 (6)	0.0491 (7)	0.0372 (6)	0.0014 (5)	−0.0009 (5)	0.0078 (5)
C16	0.0392 (6)	0.0336 (6)	0.0273 (5)	−0.0019 (5)	−0.0014 (4)	0.0026 (4)
N1	0.0654 (8)	0.0400 (7)	0.0660 (8)	−0.0120 (6)	−0.0128 (6)	0.0057 (6)
N2	0.0418 (5)	0.0339 (5)	0.0219 (4)	−0.0005 (4)	0.0022 (4)	0.0016 (4)
O1	0.0619 (7)	0.0456 (6)	0.0776 (7)	−0.0115 (5)	0.0215 (5)	−0.0125 (5)
O2	0.0545 (6)	0.0477 (6)	0.0615 (6)	−0.0030 (5)	0.0016 (5)	−0.0143 (5)
O3	0.0390 (5)	0.0543 (6)	0.0389 (5)	0.0064 (4)	0.0094 (4)	0.0160 (4)
O4	0.0389 (4)	0.0588 (6)	0.0301 (4)	−0.0043 (4)	−0.0022 (3)	0.0128 (4)

Geometric parameters (Å, º)

C1—O1	1.408 (2)	C9—H9B	0.9600
C1—H1A	0.9600	C9—H9C	0.9600
C1—H1B	0.9600	C10—N2	1.2817 (16)
C1—H1C	0.9600	C10—C13	1.4572 (15)
C2—N1	1.274 (2)	C10—H10	0.9300
C2—C5	1.463 (2)	C11—O3	1.3602 (14)
C2—H2	0.9300	C11—C12	1.3808 (16)
C3—O1	1.3686 (16)	C11—C16	1.4066 (17)
C3—C4	1.3771 (19)	C12—C13	1.4006 (16)
C3—C8	1.3999 (19)	C12—H12	0.9300
C4—C5	1.398 (2)	C13—C14	1.3892 (17)
C4—H4	0.9300	C14—C15	1.3906 (17)
C5—C6	1.384 (2)	C14—H14	0.9300
C6—C7	1.388 (2)	C15—C16	1.3771 (17)
C6—H6	0.9300	C15—H15	0.9300
C7—C8	1.369 (2)	C16—O4	1.3573 (13)
C7—H7	0.9300	N1—N1^i	1.413 (2)
C8—O2	1.3631 (16)	N2—N2^ii	1.4094 (17)
C9—O3	1.4233 (16)	O2—H2A	0.8200
C9—H9A	0.9600	O4—H4A	0.8200
O1—C1—H1A	109.5	O3—C9—H9C	109.5
O1—C1—H1B	109.5	H9A—C9—H9C	109.5
H1A—C1—H1B	109.5	H9B—C9—H9C	109.5
O1—C1—H1C	109.5	N2—C10—C13	122.03 (10)
H1A—C1—H1C	109.5	N2—C10—H10	119.0
H1B—C1—H1C	109.5	C13—C10—H10	119.0
N1—C2—C5	122.71 (14)	O3—C11—C12	125.57 (11)
N1—C2—H2	118.6	O3—C11—C16	114.60 (10)
C5—C2—H2	118.6	C12—C11—C16	119.82 (11)
O1—C3—C4	125.88 (13)	C11—C12—C13	120.24 (11)
O1—C3—C8	114.03 (12)	C11—C12—H12	119.9
C4—C3—C8	120.08 (13)	C13—C12—H12	119.9
C3—C4—C5	120.23 (13)	C14—C13—C12	119.46 (10)
C3—C4—H4	119.9	C14—C13—C10	119.38 (10)
C5—C4—H4	119.9	C12—C13—C10	121.09 (10)
C6—C5—C4	119.02 (13)	C13—C14—C15	120.22 (11)
C6—C5—C2	119.63 (14)	C13—C14—H14	119.9
C4—C5—C2	121.34 (14)	C15—C14—H14	119.9
C5—C6—C7	120.65 (14)	C16—C15—C14	120.40 (11)
C5—C6—H6	119.7	C16—C15—H15	119.8
C7—C6—H6	119.7	C14—C15—H15	119.8
C8—C7—C6	120.24 (14)	O4—C16—C15	119.28 (10)
C8—C7—H7	119.9	O4—C16—C11	120.93 (10)
C6—C7—H7	119.9	C15—C16—C11	119.77 (10)
O2—C8—C7	119.01 (12)	C2—N1—N1^i	111.66 (17)
O2—C8—C3	121.26 (12)	C10—N2—N2^ii	112.95 (11)
C7—C8—C3	119.73 (13)	C3—O1—C1	117.41 (12)
O3—C9—H9A	109.5	C8—O2—H2A	109.5
O3—C9—H9B	109.5	C11—O3—C9	117.33 (10)
H9A—C9—H9B	109.5	C16—O4—H4A	109.5
O1—C3—C4—C5	179.79 (13)	C11—C12—C13—C10	174.88 (11)
C8—C3—C4—C5	1.0 (2)	N2—C10—C13—C14	167.39 (11)
C3—C4—C5—C6	1.0 (2)	N2—C10—C13—C12	−9.42 (18)
C3—C4—C5—C2	−177.64 (12)	C12—C13—C14—C15	0.24 (19)
N1—C2—C5—C6	−175.98 (14)	C10—C13—C14—C15	−176.62 (11)
N1—C2—C5—C4	2.7 (2)	C13—C14—C15—C16	−0.2 (2)
C4—C5—C6—C7	−1.5 (2)	C14—C15—C16—O4	−176.74 (12)
C2—C5—C6—C7	177.24 (13)	C14—C15—C16—C11	1.73 (19)
C5—C6—C7—C8	−0.2 (2)	O3—C11—C16—O4	−4.44 (17)
C6—C7—C8—O2	−178.67 (13)	C12—C11—C16—O4	175.05 (11)
C6—C7—C8—C3	2.2 (2)	O3—C11—C16—C15	177.12 (11)
O1—C3—C8—O2	−0.65 (18)	C12—C11—C16—C15	−3.40 (18)
C4—C3—C8—O2	178.27 (12)	C5—C2—N1—N1^i	178.95 (13)
O1—C3—C8—C7	178.43 (12)	C13—C10—N2—N2^ii	179.90 (11)
C4—C3—C8—C7	−2.6 (2)	C4—C3—O1—C1	12.0 (2)
O3—C11—C12—C13	−177.08 (11)	C8—C3—O1—C1	−169.13 (16)
C16—C11—C12—C13	3.49 (18)	C12—C11—O3—C9	−8.17 (19)
C11—C12—C13—C14	−1.93 (18)	C16—C11—O3—C9	171.28 (12)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2A···O1	0.82	2.22	2.6658 (14)	114
O4—H4A···O3	0.82	2.24	2.6731 (12)	114
O2—H2A···O4^iii	0.82	2.34	2.9973 (14)	138
O4—H4A···N2^iv	0.82	2.05	2.8346 (12)	159

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