A second tricilinc polymorph of 6,6'-dieth-oxy-2,2'-[propane-1,2-diylbis(nitrilo-methyl-idyne)]diphenol.

The title Schiff base compound, C(21)H(26)N(2)O(4), is a second triclinic polymorph of a previously reported room-temperature structure [Jia (2009 ▶). Acta Cryst. E65, o646]. Strong intra-molecular O-H⋯N hydrogen bonds generate S(6) ring motifs. Inter-molecular C-H⋯O inter-actions link neighbouring mol-ecules into dimers with an R(2) (2)(16) ring motif. The mean planes of the two benzene rings are almost perpendicular to each other, making a dihedral angle of 88.24 (5)°. An inter-esting feature of the crystal structure is the intermolecular short C⋯O [3.1878 (13) Å] contact which is shorter than the sum of the van der Waals radii of the relevant atoms. The crystal structure is further stabilized by inter-molecular C-H⋯π and π-π inter-actions [centroid-centroid distance = 3.7414 (6) Å]. The structure has a stereogenic centre but the space group is centrosymmetric, so the mol-ecule exists as a racemate.

Related literature

For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶). For information on Schiff base ligands, complexes and their applications, see: Calligaris & Randaccio (1987 ▶). For the other polymorph, see: Jia, (2009 ▶). For related structures, see: Li et al. (2005 ▶); Bomfim et al. (2005 ▶); Glidewell et al. (2005, 2006 ▶); Sun et al. (2004 ▶); Fun et al. (2008 ▶). For bond-length data, see: Allen et al. (1987 ▶). For stability of the temperature controller used for data collection, see: Cosier & Glazer (1986 ▶).

Experimental

Crystal data

C21H26N2O4

M = 370.44

Triclinic,

a = 8.9729 (2) Å

b = 10.7008 (4) Å

c = 11.3633 (2) Å

α = 107.432 (1)°

β = 108.487 (1)°

γ = 95.979 (1)°

V = 963.03 (5) Å3

Z = 2

Mo Kα radiation

μ = 0.09 mm−1

T = 100 K

0.56 × 0.27 × 0.25 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer

Absorption correction: multi-scan (; Bruker, 2005 ▶) T min = 0.952, T max = 0.978

19581 measured reflections

5527 independent reflections

4721 reflections with I > 2σ(I)

R int = 0.026

Refinement

R[F 2 > 2σ(F 2)] = 0.045

wR(F 2) = 0.136

S = 1.05

5527 reflections

249 parameters

H-atom parameters constrained

Δρmax = 0.53 e Å−3

Δρmin = −0.23 e Å−3

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: SAINT (Bruker, 2005 ▶); 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 datablocks global, I. DOI: 10.1107/S1600536809008137/at2736sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809008137/at2736Isup2.hkl

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

C21H26N2O4	Z = 2
Mr = 370.44	F(000) = 396
Triclinic, P1	Dx = 1.277 Mg m−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 8.9729 (2) Å	Cell parameters from 9912 reflections
b = 10.7008 (4) Å	θ = 2.5–33.9°
c = 11.3633 (2) Å	µ = 0.09 mm−1
α = 107.432 (1)°	T = 100 K
β = 108.487 (1)°	Block, yellow
γ = 95.979 (1)°	0.56 × 0.27 × 0.25 mm
V = 963.03 (5) Å3

Bruker SMART APEXII CCD area-detector diffractometer	5527 independent reflections
Radiation source: fine-focus sealed tube	4721 reflections with I > 2σ(I)
graphite	Rint = 0.026
φ and ω scans	θmax = 30.0°, θmin = 2.0°
Absorption correction: multi-scan (SADABS; Bruker, 2005)	h = −12→12
Tmin = 0.952, Tmax = 0.978	k = −15→15
19581 measured reflections	l = −15→15

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)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.136	H-atom parameters constrained
S = 1.05	w = 1/[σ2(Fo2) + (0.0795P)2 + 0.2658P] where P = (Fo2 + 2Fc2)/3
5527 reflections	(Δ/σ)max = 0.001
249 parameters	Δρmax = 0.53 e Å−3
0 restraints	Δρmin = −0.23 e Å−3

Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1)K.

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.

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 > 2sigma(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	0.45973 (9)	0.68396 (7)	1.04387 (8)	0.02067 (16)
H1	0.3996	0.6074	0.9989	0.031*
O2	0.23678 (10)	0.61221 (7)	0.56112 (7)	0.02165 (17)
H2	0.2199	0.5617	0.6018	0.032*
O3	0.60593 (9)	0.93704 (7)	1.19014 (7)	0.02040 (16)
O4	0.30071 (10)	0.74269 (7)	0.41348 (7)	0.02157 (17)
N1	0.20357 (10)	0.51029 (9)	0.87252 (9)	0.01932 (18)
N2	0.22170 (11)	0.39204 (9)	0.61688 (9)	0.01981 (18)
C1	0.37342 (12)	0.77863 (10)	1.03131 (9)	0.01695 (19)
C2	0.45003 (12)	0.91483 (10)	1.10727 (10)	0.01745 (19)
C3	0.36454 (13)	1.01381 (10)	1.09335 (10)	0.0202 (2)
H3A	0.4165	1.1055	1.1421	0.024*
C4	0.20267 (13)	0.98033 (11)	1.00838 (11)	0.0230 (2)
H4A	0.1456	1.0492	1.0003	0.028*
C5	0.12610 (12)	0.84751 (11)	0.93638 (11)	0.0218 (2)
H5A	0.0158	0.8249	0.8801	0.026*
C6	0.21104 (12)	0.74568 (10)	0.94623 (10)	0.01782 (19)
C7	0.13033 (12)	0.60568 (10)	0.86605 (10)	0.0193 (2)
H7A	0.0211	0.5852	0.8079	0.023*
C8	0.11726 (12)	0.37212 (10)	0.78846 (10)	0.0197 (2)
H8A	0.0055	0.3712	0.7325	0.024*
C9	0.20882 (13)	0.31383 (10)	0.70025 (10)	0.0209 (2)
H9A	0.3182	0.3127	0.7564	0.025*
H9B	0.1525	0.2200	0.6432	0.025*
C10	0.25539 (12)	0.33633 (10)	0.51501 (10)	0.0195 (2)
H10A	0.2624	0.2448	0.4936	0.023*
C11	0.28343 (12)	0.40753 (10)	0.43059 (10)	0.01798 (19)
C12	0.32606 (13)	0.34087 (11)	0.32285 (10)	0.0224 (2)
H12A	0.3319	0.2492	0.3041	0.027*
C13	0.35938 (13)	0.40746 (11)	0.24449 (10)	0.0236 (2)
H13A	0.3881	0.3617	0.1721	0.028*
C14	0.35108 (12)	0.54260 (11)	0.27131 (10)	0.0211 (2)
H14A	0.3732	0.5880	0.2165	0.025*
C15	0.31054 (12)	0.61053 (10)	0.37785 (10)	0.01799 (19)
C16	0.27562 (11)	0.54322 (10)	0.45865 (9)	0.01716 (19)
C17	0.11095 (14)	0.29050 (11)	0.87711 (11)	0.0251 (2)
H17A	0.0583	0.3321	0.9376	0.038*
H17B	0.2207	0.2884	0.9286	0.038*
H17C	0.0497	0.1987	0.8220	0.038*
C18	0.68435 (13)	1.07531 (10)	1.27022 (10)	0.0207 (2)
H18A	0.6284	1.1129	1.3306	0.025*
H18B	0.6818	1.1295	1.2129	0.025*
C19	0.85652 (13)	1.07880 (11)	1.34933 (11)	0.0250 (2)
H19A	0.9117	1.1714	1.4071	0.038*
H19B	0.9119	1.0446	1.2887	0.038*
H19C	0.8576	1.0226	1.4036	0.038*
C20	0.32265 (13)	0.81235 (11)	0.32824 (11)	0.0228 (2)
H20A	0.2482	0.7626	0.2357	0.027*
H20B	0.4345	0.8213	0.3305	0.027*
C21	0.28754 (16)	0.94927 (12)	0.37877 (13)	0.0284 (2)
H21A	0.3039	1.0011	0.3242	0.043*
H21B	0.3602	0.9965	0.4710	0.043*
H21C	0.1757	0.9390	0.3739	0.043*

	U11	U22	U33	U12	U13	U23
O1	0.0213 (3)	0.0161 (3)	0.0204 (4)	0.0042 (3)	0.0039 (3)	0.0045 (3)
O2	0.0338 (4)	0.0181 (3)	0.0173 (3)	0.0072 (3)	0.0154 (3)	0.0053 (3)
O3	0.0215 (3)	0.0164 (3)	0.0181 (3)	0.0023 (3)	0.0042 (3)	0.0027 (3)
O4	0.0309 (4)	0.0184 (3)	0.0173 (3)	0.0041 (3)	0.0113 (3)	0.0066 (3)
N1	0.0206 (4)	0.0199 (4)	0.0153 (4)	0.0007 (3)	0.0065 (3)	0.0044 (3)
N2	0.0234 (4)	0.0187 (4)	0.0165 (4)	0.0036 (3)	0.0070 (3)	0.0059 (3)
C1	0.0202 (4)	0.0180 (4)	0.0139 (4)	0.0042 (3)	0.0082 (3)	0.0053 (3)
C2	0.0204 (4)	0.0183 (4)	0.0145 (4)	0.0037 (3)	0.0085 (3)	0.0049 (3)
C3	0.0257 (5)	0.0191 (4)	0.0187 (5)	0.0064 (4)	0.0124 (4)	0.0055 (4)
C4	0.0251 (5)	0.0247 (5)	0.0240 (5)	0.0110 (4)	0.0132 (4)	0.0090 (4)
C5	0.0199 (4)	0.0271 (5)	0.0209 (5)	0.0080 (4)	0.0096 (4)	0.0087 (4)
C6	0.0191 (4)	0.0202 (4)	0.0153 (4)	0.0039 (3)	0.0084 (3)	0.0057 (3)
C7	0.0190 (4)	0.0231 (5)	0.0150 (4)	0.0018 (3)	0.0070 (3)	0.0058 (4)
C8	0.0195 (4)	0.0194 (4)	0.0169 (4)	0.0010 (3)	0.0047 (3)	0.0050 (4)
C9	0.0264 (5)	0.0188 (4)	0.0178 (4)	0.0055 (4)	0.0078 (4)	0.0070 (4)
C10	0.0226 (4)	0.0166 (4)	0.0164 (4)	0.0043 (3)	0.0055 (4)	0.0038 (3)
C11	0.0194 (4)	0.0181 (4)	0.0140 (4)	0.0041 (3)	0.0052 (3)	0.0033 (3)
C12	0.0276 (5)	0.0212 (5)	0.0169 (4)	0.0079 (4)	0.0088 (4)	0.0033 (4)
C13	0.0272 (5)	0.0277 (5)	0.0155 (4)	0.0083 (4)	0.0103 (4)	0.0037 (4)
C14	0.0218 (5)	0.0262 (5)	0.0152 (4)	0.0041 (4)	0.0075 (4)	0.0066 (4)
C15	0.0184 (4)	0.0188 (4)	0.0146 (4)	0.0026 (3)	0.0052 (3)	0.0043 (3)
C16	0.0185 (4)	0.0185 (4)	0.0125 (4)	0.0036 (3)	0.0059 (3)	0.0029 (3)
C17	0.0282 (5)	0.0245 (5)	0.0222 (5)	0.0000 (4)	0.0093 (4)	0.0096 (4)
C18	0.0247 (5)	0.0160 (4)	0.0181 (4)	0.0019 (3)	0.0081 (4)	0.0021 (3)
C19	0.0253 (5)	0.0213 (5)	0.0222 (5)	0.0020 (4)	0.0049 (4)	0.0042 (4)
C20	0.0276 (5)	0.0240 (5)	0.0205 (5)	0.0041 (4)	0.0116 (4)	0.0105 (4)
C21	0.0377 (6)	0.0249 (5)	0.0295 (6)	0.0082 (4)	0.0168 (5)	0.0140 (4)

O1—C1	1.3514 (12)	C9—H9B	0.9900
O1—H1	0.8400	C10—C11	1.4542 (15)
O2—C16	1.3484 (11)	C10—H10A	0.9500
O2—H2	0.8400	C11—C16	1.4046 (13)
O3—C2	1.3643 (12)	C11—C12	1.4087 (14)
O3—C18	1.4432 (12)	C12—C13	1.3765 (16)
O4—C15	1.3701 (12)	C12—H12A	0.9500
O4—C20	1.4338 (13)	C13—C14	1.4008 (15)
N1—C7	1.2780 (14)	C13—H13A	0.9500
N1—C8	1.4644 (13)	C14—C15	1.3905 (14)
N2—C10	1.2777 (13)	C14—H14A	0.9500
N2—C9	1.4614 (14)	C15—C16	1.4112 (14)
C1—C6	1.4062 (13)	C17—H17A	0.9800
C1—C2	1.4153 (13)	C17—H17B	0.9800
C2—C3	1.3885 (14)	C17—H17C	0.9800
C3—C4	1.4018 (15)	C18—C19	1.5110 (15)
C3—H3A	0.9500	C18—H18A	0.9900
C4—C5	1.3802 (15)	C18—H18B	0.9900
C4—H4A	0.9500	C19—H19A	0.9800
C5—C6	1.4046 (14)	C19—H19B	0.9800
C5—H5A	0.9500	C19—H19C	0.9800
C6—C7	1.4617 (14)	C20—C21	1.5107 (16)
C7—H7A	0.9500	C20—H20A	0.9900
C8—C9	1.5242 (15)	C20—H20B	0.9900
C8—C17	1.5277 (15)	C21—H21A	0.9800
C8—H8A	1.0000	C21—H21B	0.9800
C9—H9A	0.9900	C21—H21C	0.9800
C1—O1—H1	109.5	C13—C12—C11	120.54 (9)
C16—O2—H2	109.5	C13—C12—H12A	119.7
C2—O3—C18	116.03 (8)	C11—C12—H12A	119.7
C15—O4—C20	116.95 (8)	C12—C13—C14	120.13 (9)
C7—N1—C8	118.97 (9)	C12—C13—H13A	119.9
C10—N2—C9	117.69 (9)	C14—C13—H13A	119.9
O1—C1—C6	122.09 (9)	C15—C14—C13	120.23 (10)
O1—C1—C2	118.39 (8)	C15—C14—H14A	119.9
C6—C1—C2	119.52 (9)	C13—C14—H14A	119.9
O3—C2—C3	125.27 (9)	O4—C15—C14	124.90 (9)
O3—C2—C1	115.48 (9)	O4—C15—C16	114.95 (8)
C3—C2—C1	119.25 (9)	C14—C15—C16	120.15 (9)
C2—C3—C4	120.94 (9)	O2—C16—C11	122.22 (9)
C2—C3—H3A	119.5	O2—C16—C15	118.56 (9)
C4—C3—H3A	119.5	C11—C16—C15	119.22 (9)
C5—C4—C3	120.10 (10)	C8—C17—H17A	109.5
C5—C4—H4A	119.9	C8—C17—H17B	109.5
C3—C4—H4A	119.9	H17A—C17—H17B	109.5
C4—C5—C6	120.06 (10)	C8—C17—H17C	109.5
C4—C5—H5A	120.0	H17A—C17—H17C	109.5
C6—C5—H5A	120.0	H17B—C17—H17C	109.5
C5—C6—C1	120.10 (9)	O3—C18—C19	107.74 (8)
C5—C6—C7	119.59 (9)	O3—C18—H18A	110.2
C1—C6—C7	120.30 (9)	C19—C18—H18A	110.2
N1—C7—C6	121.39 (9)	O3—C18—H18B	110.2
N1—C7—H7A	119.3	C19—C18—H18B	110.2
C6—C7—H7A	119.3	H18A—C18—H18B	108.5
N1—C8—C9	108.28 (8)	C18—C19—H19A	109.5
N1—C8—C17	108.78 (8)	C18—C19—H19B	109.5
C9—C8—C17	109.96 (9)	H19A—C19—H19B	109.5
N1—C8—H8A	109.9	C18—C19—H19C	109.5
C9—C8—H8A	109.9	H19A—C19—H19C	109.5
C17—C8—H8A	109.9	H19B—C19—H19C	109.5
N2—C9—C8	111.50 (8)	O4—C20—C21	106.98 (9)
N2—C9—H9A	109.3	O4—C20—H20A	110.3
C8—C9—H9A	109.3	C21—C20—H20A	110.3
N2—C9—H9B	109.3	O4—C20—H20B	110.3
C8—C9—H9B	109.3	C21—C20—H20B	110.3
H9A—C9—H9B	108.0	H20A—C20—H20B	108.6
N2—C10—C11	122.60 (9)	C20—C21—H21A	109.5
N2—C10—H10A	118.7	C20—C21—H21B	109.5
C11—C10—H10A	118.7	H21A—C21—H21B	109.5
C16—C11—C12	119.72 (10)	C20—C21—H21C	109.5
C16—C11—C10	120.87 (9)	H21A—C21—H21C	109.5
C12—C11—C10	119.35 (9)	H21B—C21—H21C	109.5
C18—O3—C2—C3	1.11 (15)	C17—C8—C9—N2	−178.20 (8)
C18—O3—C2—C1	−178.73 (8)	C9—N2—C10—C11	−175.17 (9)
O1—C1—C2—O3	−1.69 (13)	N2—C10—C11—C16	0.46 (15)
C6—C1—C2—O3	177.98 (9)	N2—C10—C11—C12	177.59 (10)
O1—C1—C2—C3	178.45 (9)	C16—C11—C12—C13	−0.30 (15)
C6—C1—C2—C3	−1.88 (15)	C10—C11—C12—C13	−177.47 (9)
O3—C2—C3—C4	−177.92 (10)	C11—C12—C13—C14	−0.02 (16)
C1—C2—C3—C4	1.92 (15)	C12—C13—C14—C15	0.56 (16)
C2—C3—C4—C5	−0.39 (17)	C20—O4—C15—C14	4.75 (14)
C3—C4—C5—C6	−1.17 (16)	C20—O4—C15—C16	−175.21 (8)
C4—C5—C6—C1	1.18 (16)	C13—C14—C15—O4	179.28 (9)
C4—C5—C6—C7	−177.88 (9)	C13—C14—C15—C16	−0.76 (15)
O1—C1—C6—C5	−179.99 (9)	C12—C11—C16—O2	−179.44 (9)
C2—C1—C6—C5	0.35 (15)	C10—C11—C16—O2	−2.33 (15)
O1—C1—C6—C7	−0.94 (15)	C12—C11—C16—C15	0.10 (14)
C2—C1—C6—C7	179.41 (9)	C10—C11—C16—C15	177.22 (9)
C8—N1—C7—C6	−179.15 (9)	O4—C15—C16—O2	−0.05 (13)
C5—C6—C7—N1	−179.86 (10)	C14—C15—C16—O2	179.99 (9)
C1—C6—C7—N1	1.08 (15)	O4—C15—C16—C11	−179.61 (8)
C7—N1—C8—C9	121.02 (10)	C14—C15—C16—C11	0.43 (14)
C7—N1—C8—C17	−119.50 (10)	C2—O3—C18—C19	−177.40 (9)
C10—N2—C9—C8	−161.52 (9)	C15—O4—C20—C21	173.58 (9)
N1—C8—C9—N2	−59.47 (11)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N1	0.84	1.83	2.5752 (13)	146
O2—H2···N2	0.84	1.88	2.6178 (13)	147
C9—H9A···O1i	0.99	2.49	3.4293 (14)	159
C18—H18b···Cg1ii	0.9900	2.9800	3.8340 (12)	142.00
C7—H7A···Cg2iii	0.96	2.72	3.5554 (12)	176

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯N1	0.84	1.83	2.5752 (13)	146
O2—H2⋯N2	0.84	1.88	2.6178 (13)	147
C9—H9A⋯O1i	0.99	2.49	3.4293 (14)	159
C18—H18b⋯Cg1ii	0.99	2.98	3.8340 (12)	142
C7—H7A⋯Cg2iii	0.96	2.72	3.5554 (12)	176

Symmetry codes: (i) ; (ii) ; (iii) . Cg1 and Cg2 are the centroids of the C1–C6 and C11–C16 benzene rings, respectively.