Crystal structure of diethyl 3,3′-{2,2′-(1E)-[1,4-phenyl­enebis(azan-1-yl-1-yl­idene)]bis­(methan-1-yl-1-yl­idene)bis­(1H-pyrrole-2,1-di­yl)}di­propano­ate

The complete mol­ecule of the title compound, C₂₆H₃₀N₄O₄, is generated by crystallographic inversion symmetry. The dihedral angle between the planes of the benzene and pyrrole rings is 45.20 (11)°; the N atom bonded to the the benzene ring and the pyrrole N atom are in a syn conformation. The side chain adopts an extended conformation [N—C—C—C = 169.07 (17)° and C—O—C—C = −176.54 (17)°]. No directional inter­actions could be identified in the crystal packing.

Key indicators

• Single-crystal X-ray study
• T = 150 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.055
• wR factor = 0.138
• Data-to-parameter ratio = 18.7

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Alert level C
PLAT906_ALERT_3_C Large K value in the Analysis of Variance ......      5.322 Check
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600          4 Report

Alert level G
PLAT910_ALERT_3_G Missing # of FCF Reflection(s) Below Th(Min) ...          2 Report
PLAT912_ALERT_4_G Missing # of FCF Reflections Above STh/L=  0.600        472 Note

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   2 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   2 ALERT level G = General information/check it is not something unexpected

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   3 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
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              Please specify the role of each of the co-authors
              for your paper.

Author Response: Jasim Alshawi is the PhD student; Prof. Muoayed Yousif is the PhD student supervisor in IRAQ; Grigore Timco and Inigo J. Vitorica Yrezabal have solved the crystal structure; Prof. Richard Winpenny is the PhD student supervisor in UK; Prof. Mohamed J. Al-Jeboori is the PhD student supervisor in IRAQ.

   1 ALERT level A = Data missing that is essential or data in wrong format
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S1. Comment

The Schiff base diethyl 3,3'-(2,2'-(1E)-(1,4-phenylenebis(azan-1-yl-1-ylidene))bis (methan-1-yl-1-ylidene)bis(1H-pyrrole-2,1-diyl))dipropanoate was prepared in two steps. The reaction of 1H-pyrrole-2-carbaldehyde with ethyl bromopropanoate resulted in the formation of (2-formyl-1H-pyrrole-1-yl)-propanoate (Koriatopoulou et al. (2008) and Singh & Pal (2010)). The reaction of two moles of the pyrrole ester with p-phenylenediamine gave the title of Schiff-base compound (Yang et al., 2004; Ourari et al., 2013). The compound with molar mass 462.54 g mol-1, crystallizes in monoclinic crystal structure with a space group c12 /c1 and had a calculated density 1.259 g cm-3. The asymetric unit consists of half the molecule, the molecule is completed by inversion symmetry. Infrared spectra indidicates typical absorbance bands of the

functional -C=N and carbonyl -C=O at 1595 and 1680 cm-1, respectively. The positive ES mass spectrum of the bis Schiff base showed a parent ion peak at m/z = 463.7 (M+H)+, corresponding to C26H30N4O4, for which the required value=462.3. The values distance (1.270Å) observed for (N7-C6) is shorter than (N7-C8) (1.458Å), indicating a double bond order. The distance observed at (1.384Å) for (N1-C5), revealed a resonance is occurred in the pyrrole system between lon pair electron of the nitrogen atom and the pyrrole ring. Other bond lengths and bond angles are within reported values.

Related literature

For the synthesis of dipyrrole Schiff base ligands, see: Meghdadi et al.(2010); Munro et al. (2004). For the synthesis of pyrrole ester precursors, see: Koriatopoulou et al. (2008); Singh & Pal (2010). For the preparation of the title compound, see: Yang et al. (2004); Ourari et al. (2013).

S2. Experimental

FT-IR data were recorded on Agilent 8400s FT-IR while NMR data were collected on Bruker 500 MHz spectrometer in CDCl3 solutions. The assignment of the chemical shifts for the NMR data were made following numbering shown in structure. The title compound was prepared in two steps and as follows: Preparation of ethyl(2-formyl-1H-pyrrole-1-yl)-propanoate(L): It was prepared by literature procedures (Koriatopoulou et al., (2008); Singh & Pal (2010), as follows: To a mixture of 1H-pyrrole-2-carbaldehyde(1.00g,10.51mmol), K₂CO₃ (2.90g, 21.02mmol) and (2.64g, 10.51mmol) of 18-crown-6 in dry 1,4-dioxane (20ml), was added a solution of ethyl bromopropanoate (2.17g, 12mmol) in dry 1,4-dioxane (20ml)dropwise over a period of 30 min.The reaction mixture was allowed to reflux under nitrogen atmosphere for 6h, and then the solvent was removed under reduced pressure. Water (50ml) was added to the residue, and the mixture was extracted with ethyl acetate (3 × 15ml). The combined organic layers were washed with brine (15ml), and then dried over Na₂SO₄.The solvent was removed under reduced pressure, and the oily residue was purified by flash chromatography with an eluent mixture (33% ethyl acetate / hexane), yield 0.70 g (70%) of the title compound as a yellow oil product.IR (ATR cm^-1): 1660 ν(C=O) aldehyde moiety. 172 0 ν (C=O) ester group. NMR data (p.p.m),δH (500 MHz, CDCl₃): 1.10 (3H, t, C13-H), 2.70 (2H, t, C9-H), 4.01 (2H, Q, C12-H), 4.47 (2H, t, C8-H), 6.09 (1H, t, C3-H),6.83 (1H, d, C4-H), 6.94 (1H, d, C2-H) and 9.43 (1H, s, C6-H); δC (125.75 MHz, CDCl3):14.06 C13, 35.68 C9, 44.71 C8, 60.62 C12,109.53 C3, 125.17 C 4, 131.02 C5 and 132.23 C2, and C=O of the carboxylate moiety at 171.17 (C10) and 179.15 for C6. The positive ES mass spectrum at m/z =196.4 (M+H)⁺ (80 %) for C10H13NO3, requires =195.1. The other peaks which detected at m/z =167.4 (100 %), 123.3 (50 %), 95.2 (5 %) and 67 (6 %) correspond to [M-CH2CH3]⁺, [M-(CH2CH3+CO2)]⁺, [M-(CH2CH3+CO2+CH2+CH2)]⁺ and [M-(CH2CH3+CO2+CH2CH2+CO)]⁺, respectively.Synthesis of the title Schiff-base:achieved using standard method as follows: To a mixture of L (1.95g, 10mmol) in ethanol (20ml)with 3 drops of glacial acetic acid, a solution of p-phenylendiamine (0.5g, 5mmol) in ethanol (20ml) was added dropwise over a period of 20 min. The reaction mixture was allowed to reflux for 3h, and then cooled to room temperature. A white precipitate was collected by filtration and recrystallised from ethanol, yield 1.07g (55%). Crystals were obtained from evaporation of a mixture of methanol/acetone at room temperature. IR (ATR,cm^-1): at line % / 1595 (C=N),1680 (C=O). ¹H NMR dH (500 MHz, CDCl₃, p.p.m) δH: 1.16 (6H, t, C16, 16–H), 2.85 (4H, t, C12, 12–H), 4.05 (4H, q, C15, 15–H), 4.67 (4H, t, C11,11–H), 6.11 (2H, t, C3, 3–H), 6.58 (2H, d, C4,4–H), 6.83 (2H, d, C2, 2–H), 7.11 (4H, s, C9, 9, C10, 10–H) and 8.25 (2H, s, C6, 6–H): ¹³C NMR (125.75 MHz, CDCl₃, p.p.m) δC: 14.29 (C16, 16-), 36.14 (C12, 12-), 44.98 (C11, 11-), 60.62 (C15,15-), 108.85 (C 3, 3-), 119.88 (C2, 2-), 121.57 (C9,8-) and C10,10-), 129.16 and 129.17 to (C4, 4- and C5, 5-), 149.38 (C6, 6-) and 150.02 (C 8, 8-). C=O at 171.12 (C13,13-). ). The positive ES mass spectrum at m/z = 463.7 (M+H)⁺ (42%) for C26H30N4O4, requires =462.3. The other peaks detected at m/z =405.2 (3%), 361.6 (12%), 317.2 (3%) and 261.4 (3%) correspond to [M-2(CH2CH3)]⁺, [M-(2(CH2CH3)+CO2)]⁺, [M-(2CH2CH3+2CO2)]⁺ and [M-(2CH2CH3+2CO2+2CH2CH2)]⁺, espectively.

S3. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1.

The refinement was H atom attached to N1 was located in the difference Fourier map and refined isotropically. All other H atoms were placed in calculated positions with d(C—H) = 0.95 Å for aromatic, 0.99 for CH2 and 0.98 Å for CH3 atoms. The Uiso values were constrained to be 1.5Ueq of the carrier atom for methyl H atoms and 1.2Ueq for the remaining H atoms. A rotating group model was used for the methyl groups.

Computing details

Data collection: CrysAlis PRO (Agilent, 2013); cell refinement: CrysAlis PRO (Agilent, 2013); data reduction: CrysAlis PRO (Agilent, 2013); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

Figures

Fig. 1. A view of the molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level.

Diethyl 3,3'-{2,2'-(1E)-[1,4-phenylenebis(azan-1-yl-1-ylidene)]bis(methan-1-yl-1-ylidene)bis(1H-pyrrole-2,1-diyl)}dipropanoate

Crystal data

C26H30N4O4	F(000) = 984
Mr = 462.54	Dx = 1.259 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 21.6153 (10) Å	Cell parameters from 1750 reflections
b = 8.1227 (4) Å	θ = 3.8–27.5°
c = 13.9404 (8) Å	µ = 0.09 mm^−1
β = 94.395 (5)°	T = 150 K
V = 2440.4 (2) Å^3	Block, clear light colourless
Z = 4	0.4 × 0.3 × 0.3 mm

Data collection

Agilent SuperNova (Single source at offset, Atlas) diffractometer	2900 independent reflections
Radiation source: SuperNova (Mo) X-ray Source	1697 reflections with I > 2σ(I)
Mirror monochromator	Rint = 0.063
Detector resolution: 10.3705 pixels mm^-1	θmax = 29.5°, θmin = 2.9°
ω scans	h = −18→29
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2013)	k = −10→7
Tmin = 0.613, Tmax = 1.000	l = −19→18
6592 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.055	H-atom parameters constrained
wR(F^2) = 0.138	w = 1/[σ^2(Fo^2) + (0.0338P)^2 + 0.0686P] where P = (Fo^2 + 2Fc^2)/3
S = 1.10	(Δ/σ)max < 0.001
2900 reflections	Δρmax = 0.22 e Å^−3
155 parameters	Δρmin = −0.26 e Å^−3
0 restraints

Special details

Experimental. CrysAlisPro, Agilent Technologies, Version 1.171.36.28 (release 01-02-2013 CrysAlis171 .NET) (compiled Feb 1 2013,16:14:44) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.

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.

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

	x	y	z	Uiso*/Ueq
O14	0.34059 (6)	0.02364 (17)	0.24674 (10)	0.0286 (4)
N1	0.45878 (7)	0.29578 (19)	0.01458 (12)	0.0225 (4)
O17	0.41066 (7)	0.2126 (2)	0.29870 (11)	0.0385 (4)
N7	0.34834 (7)	0.5212 (2)	0.01854 (13)	0.0231 (4)
C13	0.38269 (9)	0.1407 (2)	0.23355 (16)	0.0240 (5)
C6	0.37626 (9)	0.4878 (2)	−0.05699 (16)	0.0233 (5)
H6	0.3615	0.5387	−0.1140	0.028*
C5	0.42829 (9)	0.3787 (2)	−0.06151 (16)	0.0227 (5)
C8	0.29823 (9)	0.6351 (2)	0.00733 (15)	0.0213 (5)
C9	0.29548 (9)	0.7593 (2)	0.07499 (16)	0.0242 (5)
H9	0.3258	0.7654	0.1260	0.029*
C2	0.50726 (9)	0.2115 (3)	−0.01898 (17)	0.0285 (5)
H2	0.5353	0.1466	0.0181	0.034*
C11	0.44300 (9)	0.2904 (3)	0.11490 (15)	0.0248 (5)
H11A	0.4308	0.3996	0.1345	0.030*
H11B	0.4794	0.2581	0.1556	0.030*
C12	0.39047 (9)	0.1701 (3)	0.12900 (15)	0.0247 (5)
H12A	0.3521	0.2135	0.0983	0.030*
H12B	0.3991	0.0663	0.0983	0.030*
C15	0.33162 (10)	−0.0179 (3)	0.34693 (16)	0.0307 (6)
H15A	0.3205	0.0796	0.3820	0.037*
H15B	0.3694	−0.0636	0.3782	0.037*
C10	0.25193 (9)	0.6253 (2)	−0.06747 (16)	0.0244 (5)
H10	0.2528	0.5411	−0.1126	0.029*
C4	0.45880 (9)	0.3440 (3)	−0.14264 (17)	0.0283 (5)
H4	0.4484	0.3843	−0.2042	0.034*
C3	0.50810 (10)	0.2377 (3)	−0.11602 (17)	0.0318 (6)
H3	0.5361	0.1933	−0.1564	0.038*
C16	0.28000 (11)	−0.1429 (3)	0.34458 (18)	0.0412 (6)
H16A	0.2913	−0.2375	0.3085	0.062*
H16B	0.2427	−0.0953	0.3147	0.062*
H16C	0.2731	−0.1756	0.4091	0.062*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O14	0.0361 (8)	0.0298 (9)	0.0205 (9)	−0.0087 (7)	0.0052 (7)	−0.0004 (7)
N1	0.0217 (9)	0.0226 (10)	0.0236 (10)	0.0014 (7)	0.0051 (8)	0.0034 (8)
O17	0.0397 (9)	0.0498 (11)	0.0266 (10)	−0.0165 (8)	0.0054 (8)	−0.0087 (8)
N7	0.0234 (9)	0.0209 (9)	0.0255 (10)	0.0023 (7)	0.0057 (8)	−0.0010 (8)
C13	0.0213 (11)	0.0228 (11)	0.0283 (13)	−0.0002 (9)	0.0032 (10)	−0.0042 (10)
C6	0.0258 (11)	0.0184 (11)	0.0260 (12)	−0.0029 (8)	0.0042 (10)	0.0040 (10)
C5	0.0241 (10)	0.0189 (11)	0.0257 (12)	0.0002 (8)	0.0064 (9)	0.0021 (10)
C8	0.0212 (10)	0.0192 (11)	0.0242 (12)	0.0008 (8)	0.0071 (9)	0.0028 (10)
C9	0.0209 (10)	0.0260 (12)	0.0255 (12)	−0.0006 (9)	0.0005 (9)	−0.0031 (10)
C2	0.0236 (11)	0.0255 (12)	0.0375 (14)	0.0074 (9)	0.0106 (10)	0.0027 (11)
C11	0.0236 (10)	0.0270 (12)	0.0239 (12)	0.0000 (9)	0.0019 (9)	0.0010 (10)
C12	0.0262 (11)	0.0254 (12)	0.0226 (12)	0.0010 (9)	0.0023 (9)	−0.0028 (10)
C15	0.0414 (13)	0.0290 (13)	0.0230 (13)	−0.0002 (10)	0.0102 (11)	0.0002 (11)
C10	0.0260 (11)	0.0219 (11)	0.0257 (13)	0.0001 (9)	0.0040 (10)	−0.0070 (10)
C4	0.0323 (12)	0.0261 (12)	0.0275 (13)	0.0012 (9)	0.0099 (10)	0.0063 (11)
C3	0.0330 (12)	0.0293 (13)	0.0351 (15)	0.0075 (10)	0.0153 (11)	0.0018 (11)
C16	0.0551 (16)	0.0357 (14)	0.0347 (15)	−0.0100 (11)	0.0152 (13)	0.0024 (12)

Geometric parameters (Å, º)

O14—C13	1.338 (2)	C2—C3	1.371 (3)
O14—C15	1.464 (2)	C11—H11A	0.9700
N1—C5	1.381 (3)	C11—H11B	0.9700
N1—C2	1.364 (2)	C11—C12	1.522 (3)
N1—C11	1.465 (3)	C12—H12A	0.9700
O17—C13	1.203 (2)	C12—H12B	0.9700
N7—C6	1.282 (2)	C15—H15A	0.9700
N7—C8	1.424 (2)	C15—H15B	0.9700
C13—C12	1.499 (3)	C15—C16	1.507 (3)
C6—H6	0.9300	C10—C9^i	1.387 (3)
C6—C5	1.437 (3)	C10—H10	0.9300
C5—C4	1.381 (3)	C4—H4	0.9300
C8—C9	1.386 (3)	C4—C3	1.399 (3)
C8—C10	1.391 (3)	C3—H3	0.9300
C9—H9	0.9300	C16—H16A	0.9600
C9—C10^i	1.387 (3)	C16—H16B	0.9600
C2—H2	0.9300	C16—H16C	0.9600
C13—O14—C15	115.83 (16)	C12—C11—H11B	109.2
C5—N1—C11	127.98 (16)	C13—C12—C11	111.61 (17)
C2—N1—C5	108.38 (18)	C13—C12—H12A	109.3
C2—N1—C11	123.62 (18)	C13—C12—H12B	109.3
C6—N7—C8	116.70 (18)	C11—C12—H12A	109.3
O14—C13—C12	112.02 (18)	C11—C12—H12B	109.3
O17—C13—O14	123.3 (2)	H12A—C12—H12B	108.0
O17—C13—C12	124.69 (18)	O14—C15—H15A	110.4
N7—C6—H6	117.1	O14—C15—H15B	110.4
N7—C6—C5	125.9 (2)	O14—C15—C16	106.64 (18)
C5—C6—H6	117.1	H15A—C15—H15B	108.6
N1—C5—C6	126.61 (19)	C16—C15—H15A	110.4
N1—C5—C4	107.45 (17)	C16—C15—H15B	110.4
C4—C5—C6	125.9 (2)	C8—C10—H10	119.9
C9—C8—N7	118.06 (19)	C9^i—C10—C8	120.20 (18)
C9—C8—C10	119.07 (18)	C9^i—C10—H10	119.9
C10—C8—N7	122.86 (18)	C5—C4—H4	126.0
C8—C9—H9	119.6	C5—C4—C3	108.1 (2)
C8—C9—C10^i	120.71 (19)	C3—C4—H4	126.0
C10^i—C9—H9	119.6	C2—C3—C4	106.86 (18)
N1—C2—H2	125.4	C2—C3—H3	126.6
N1—C2—C3	109.23 (19)	C4—C3—H3	126.6
C3—C2—H2	125.4	C15—C16—H16A	109.5
N1—C11—H11A	109.2	C15—C16—H16B	109.5
N1—C11—H11B	109.2	C15—C16—H16C	109.5
N1—C11—C12	111.88 (17)	H16A—C16—H16B	109.5
H11A—C11—H11B	107.9	H16A—C16—H16C	109.5
C12—C11—H11A	109.2	H16B—C16—H16C	109.5
O14—C13—C12—C11	−174.17 (16)	C5—N1—C11—C12	79.5 (2)
N1—C5—C4—C3	0.5 (2)	C5—C4—C3—C2	−0.8 (2)
N1—C2—C3—C4	0.9 (2)	C8—N7—C6—C5	179.01 (17)
N1—C11—C12—C13	169.07 (17)	C9—C8—C10—C9^i	1.3 (3)
O17—C13—C12—C11	5.8 (3)	C2—N1—C5—C6	−177.15 (19)
N7—C6—C5—N1	−2.6 (3)	C2—N1—C5—C4	0.0 (2)
N7—C6—C5—C4	−179.3 (2)	C2—N1—C11—C12	−98.6 (2)
N7—C8—C9—C10^i	179.47 (17)	C11—N1—C5—C6	4.5 (3)
N7—C8—C10—C9^i	−179.52 (18)	C11—N1—C5—C4	−178.28 (18)
C13—O14—C15—C16	176.56 (17)	C11—N1—C2—C3	177.83 (18)
C6—N7—C8—C9	−134.2 (2)	C15—O14—C13—O17	−2.2 (3)
C6—N7—C8—C10	46.7 (3)	C15—O14—C13—C12	177.75 (16)
C6—C5—C4—C3	177.72 (19)	C10—C8—C9—C10^i	−1.4 (3)
C5—N1—C2—C3	−0.6 (2)

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