Nitroxide radicals appended to phthalo­nitriles: synthesis, structural characterization and photophysical properties

The syntheses of 4-[4-(4,4,5,5-tetra­methyl-2-imidazoline-3-oxide-1-oxyl-2-yl)phen­oxy]phthalo­nitrile (3, C₂₁H₁₉N₄O₃) and 4-[4-(4,4,5,5-tetra­methyl-2-imidazoline-1-oxyl-2-yl)phen­oxy]phthalo­nitrile (4) were carried out by microwave-assisted nucleophilic aromatic substitution of 4-nitro­phthalo­nitrile (2) by the pre-formed 2-(4-hy­droxy­phen­yl)-4,4,5,5-tetra­methyl-2-imidazoline-3-oxide-1-oxyl (1). Com­pounds 3 and 4 were characterized unambiguously by a rich array of analyses, such as melting point, FT–IR, MALDI–TOF MS, elemental analysis, UV–Vis, CV, EPR, magnetic measurements and single-crystal X-ray diffraction. Structural studies demonstrate that the C—H...X and C—X...π (X = O and N) inter­actions in the radical nitronyl nitroxide groups play an important role in the assembly of the crystal structures. Moreover, cyclic voltammetry analyses show that the phthalo­nitrile substituent retains the redox properties of the Ullman radicals.

Computing details

Data collection: APEX2 (Bruker, 2014); cell refinement: APEX2 (Bruker, 2014); data reduction: SAINT (Bruker, 2013); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009), PLATON (Spek, 2009, 2015) and Mercury (Macrae et al., 2020).

4-[4-(4,4,5,5-Tetramethyl-2-imidazoline-3-oxide-1-oxyl-2-yl)phenoxy]benzene-1,2-dicarbonitrile

Crystal data

C21H19N4O3	F(000) = 788
Mr = 375.40	Dx = 1.365 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 10.575 (3) Å	Cell parameters from 1457 reflections
b = 17.149 (5) Å	θ = 2.3–21.9°
c = 10.615 (3) Å	µ = 0.09 mm^−1
β = 108.434 (14)°	T = 173 K
V = 1826.3 (9) Å^3	Plate, blue
Z = 4	0.24 × 0.15 × 0.08 mm

Data collection

Bruker APEXII CCD diffractometer	3237 independent reflections
Multilayer QUAZAR mirrors monochromator	1988 reflections with I > 2σ(I)
Detector resolution: 8.3333 pixels mm^-1	Rint = 0.084
φ and ω scans	θmax = 25.1°, θmin = 2.0°
Absorption correction: multi-scan (SADABS; Bruker, 2014)	h = −12→12
Tmin = 0.983, Tmax = 0.992	k = −20→20
12874 measured reflections	l = −12→12

Refinement

Refinement on F^2	Primary atom site location: dual
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.063	H-atom parameters constrained
wR(F^2) = 0.177	w = 1/[σ^2(Fo^2) + (0.0704P)^2 + 1.145P] where P = (Fo^2 + 2Fc^2)/3
S = 1.06	(Δ/σ)max < 0.001
3237 reflections	Δρmax = 0.30 e Å^−3
257 parameters	Δρmin = −0.26 e Å^−3
0 restraints

Special details

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. The data were obtained with Bruker APEX II QUAZAR three-circle diffractometer. Indexing was performed using APEX2 (Bruker, 2014). Data integration and reduction were carried out with SAINT (Bruker, 2013). Absorption correction was performed by multi-scan method implemented in SADABS (Bruker, 2014). The structure was solved using SHELXT (Sheldrick, 2015) and then refined by full-matrix least-squares refinements on F² using the SHELXL (Sheldrick, 2015) in OLEX2 (Dolomanov et al., 2009). All non-hydrogen atoms were refined anisotropically using all reflections with I > 2σ(I).

Crystal structure validations and geometrical calculations were performed using Platon software and Mercury was used for visualization of the cif file (Spek, 2009; Spek 2015; Macrae et al., 2006). Additional crystallographic data with CCDC reference number 1913919 have been deposited within the Cambridge Crystallographic Data Center via www.ccdc.cam.ac.uk/deposit

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

	x	y	z	Uiso*/Ueq
O1	0.8584 (2)	0.07900 (15)	0.5861 (2)	0.0351 (7)
O2	0.2906 (2)	0.04040 (15)	0.6936 (2)	0.0383 (7)
O3	0.5691 (2)	0.21512 (15)	0.9834 (2)	0.0383 (7)
N5	1.2488 (4)	0.0964 (2)	0.3142 (3)	0.0484 (9)
N6	0.9779 (3)	0.2050 (2)	0.0376 (3)	0.0414 (9)
N7	0.3399 (3)	0.08735 (17)	0.7906 (3)	0.0268 (7)
N8	0.4735 (3)	0.16700 (17)	0.9304 (3)	0.0277 (7)
C101	1.1465 (4)	0.1049 (2)	0.3271 (3)	0.0331 (9)
C102	0.9488 (3)	0.1865 (2)	0.1284 (3)	0.0319 (9)
C103	1.0181 (3)	0.1195 (2)	0.3424 (3)	0.0247 (8)
C104	0.9210 (3)	0.1618 (2)	0.2464 (3)	0.0273 (8)
C105	0.8008 (3)	0.1790 (2)	0.2667 (3)	0.0294 (9)
H105	0.735443	0.208496	0.202293	0.035*
C106	0.7755 (3)	0.1538 (2)	0.3796 (3)	0.0312 (9)
H106	0.693805	0.166436	0.394219	0.037*
C107	0.8706 (3)	0.1098 (2)	0.4712 (3)	0.0272 (8)
C108	0.9933 (3)	0.0932 (2)	0.4550 (3)	0.0278 (8)
H108	1.058814	0.064359	0.520326	0.033*
C109	0.7512 (3)	0.0952 (2)	0.6318 (3)	0.0285 (8)
C110	0.6201 (3)	0.0815 (2)	0.5589 (3)	0.0306 (9)
H110	0.596564	0.065001	0.469015	0.037*
C111	0.5228 (3)	0.0925 (2)	0.6203 (3)	0.0288 (8)
H111	0.431814	0.083932	0.571168	0.035*
C112	0.5568 (3)	0.1159 (2)	0.7518 (3)	0.0243 (8)
C113	0.6913 (3)	0.1287 (2)	0.8226 (3)	0.0324 (9)
H113	0.716074	0.144591	0.912874	0.039*
C114	0.7877 (3)	0.1184 (2)	0.7625 (3)	0.0310 (9)
H114	0.878847	0.127216	0.810801	0.037*
C115	0.4587 (3)	0.1242 (2)	0.8200 (3)	0.0242 (8)
C116	0.3731 (3)	0.1465 (2)	0.9981 (3)	0.0273 (8)
C117	0.2598 (3)	0.1142 (2)	0.8778 (3)	0.0285 (8)
C118	0.4389 (4)	0.0853 (2)	1.1017 (3)	0.0407 (10)
H11A	0.520580	0.106914	1.164184	0.061*
H11B	0.461049	0.039459	1.057753	0.061*
H11C	0.377570	0.070227	1.149917	0.061*
C119	0.3367 (4)	0.2178 (2)	1.0622 (4)	0.0373 (9)
H11D	0.311834	0.260221	0.997127	0.056*
H11E	0.413254	0.233953	1.137429	0.056*
H11F	0.261308	0.205667	1.093820	0.056*
C120	0.1838 (4)	0.0463 (2)	0.9080 (4)	0.0402 (10)
H12A	0.245343	0.003152	0.944094	0.060*
H12B	0.115673	0.029329	0.826294	0.060*
H12C	0.140785	0.062212	0.973286	0.060*
C121	0.1667 (3)	0.1770 (2)	0.8016 (3)	0.0365 (9)
H12D	0.106826	0.155151	0.718881	0.055*
H12E	0.218831	0.219520	0.780791	0.055*
H12F	0.114003	0.197222	0.855542	0.055*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0269 (14)	0.0525 (18)	0.0307 (14)	0.0069 (11)	0.0158 (11)	0.0075 (12)
O2	0.0316 (14)	0.0453 (18)	0.0381 (15)	−0.0086 (12)	0.0112 (12)	−0.0186 (13)
O3	0.0308 (14)	0.0474 (18)	0.0365 (14)	−0.0128 (12)	0.0103 (11)	−0.0152 (13)
N5	0.043 (2)	0.058 (3)	0.053 (2)	0.0108 (17)	0.0270 (18)	0.0105 (18)
N6	0.0362 (19)	0.058 (2)	0.0287 (18)	−0.0032 (16)	0.0080 (14)	0.0016 (16)
N7	0.0245 (16)	0.0310 (18)	0.0253 (16)	−0.0012 (13)	0.0084 (12)	−0.0044 (13)
N8	0.0225 (15)	0.0348 (19)	0.0269 (16)	−0.0019 (13)	0.0092 (12)	−0.0014 (14)
C101	0.038 (2)	0.035 (2)	0.029 (2)	0.0018 (17)	0.0139 (17)	0.0036 (17)
C102	0.029 (2)	0.039 (2)	0.025 (2)	−0.0032 (16)	0.0055 (16)	−0.0012 (17)
C103	0.0274 (19)	0.027 (2)	0.0225 (18)	−0.0019 (15)	0.0112 (14)	−0.0040 (15)
C104	0.027 (2)	0.034 (2)	0.0204 (18)	−0.0034 (15)	0.0065 (14)	−0.0061 (16)
C105	0.027 (2)	0.032 (2)	0.0254 (19)	−0.0019 (15)	0.0042 (15)	−0.0013 (16)
C106	0.0210 (19)	0.041 (2)	0.030 (2)	−0.0022 (16)	0.0069 (15)	−0.0059 (17)
C107	0.028 (2)	0.033 (2)	0.0226 (18)	−0.0017 (16)	0.0108 (15)	−0.0024 (16)
C108	0.0236 (19)	0.032 (2)	0.0271 (19)	0.0006 (15)	0.0068 (15)	−0.0017 (16)
C109	0.027 (2)	0.035 (2)	0.0282 (19)	0.0039 (15)	0.0158 (15)	0.0034 (16)
C110	0.030 (2)	0.039 (2)	0.0243 (18)	−0.0021 (16)	0.0115 (15)	−0.0006 (16)
C111	0.0225 (19)	0.038 (2)	0.0244 (19)	−0.0005 (15)	0.0046 (15)	0.0001 (16)
C112	0.0240 (19)	0.026 (2)	0.0228 (18)	0.0032 (14)	0.0074 (14)	0.0019 (15)
C113	0.027 (2)	0.045 (2)	0.0236 (19)	−0.0022 (16)	0.0054 (15)	0.0018 (17)
C114	0.0236 (19)	0.041 (2)	0.029 (2)	0.0000 (16)	0.0092 (15)	0.0017 (17)
C115	0.0227 (19)	0.028 (2)	0.0208 (18)	0.0002 (15)	0.0053 (14)	0.0000 (15)
C116	0.0229 (19)	0.036 (2)	0.0243 (18)	0.0004 (15)	0.0099 (14)	−0.0019 (16)
C117	0.026 (2)	0.034 (2)	0.0281 (19)	0.0021 (15)	0.0127 (15)	−0.0002 (16)
C118	0.040 (2)	0.057 (3)	0.027 (2)	0.0090 (19)	0.0138 (17)	0.0057 (19)
C119	0.035 (2)	0.043 (3)	0.038 (2)	−0.0020 (18)	0.0181 (17)	−0.0100 (19)
C120	0.038 (2)	0.043 (3)	0.045 (2)	−0.0122 (18)	0.0224 (19)	−0.0040 (19)
C121	0.027 (2)	0.046 (3)	0.037 (2)	0.0072 (17)	0.0100 (16)	0.0035 (18)

Geometric parameters (Å, º)

O1—C107	1.372 (4)	C111—H111	0.9500
O1—C109	1.394 (4)	C111—C112	1.386 (4)
O2—N7	1.281 (3)	C112—C113	1.400 (5)
O3—N8	1.289 (3)	C112—C115	1.447 (4)
N5—C101	1.142 (4)	C113—H113	0.9500
N6—C102	1.146 (4)	C113—C114	1.375 (5)
N7—C115	1.352 (4)	C114—H114	0.9500
N7—C117	1.510 (4)	C116—C117	1.551 (5)
N8—C115	1.350 (4)	C116—C118	1.519 (5)
N8—C116	1.499 (4)	C116—C119	1.508 (5)
C101—C103	1.440 (5)	C117—C120	1.506 (5)
C102—C104	1.438 (5)	C117—C121	1.511 (5)
C103—C104	1.399 (5)	C118—H11A	0.9800
C103—C108	1.377 (4)	C118—H11B	0.9800
C104—C105	1.387 (5)	C118—H11C	0.9800
C105—H105	0.9500	C119—H11D	0.9800
C105—C106	1.378 (5)	C119—H11E	0.9800
C106—H106	0.9500	C119—H11F	0.9800
C106—C107	1.381 (5)	C120—H12A	0.9800
C107—C108	1.391 (5)	C120—H12B	0.9800
C108—H108	0.9500	C120—H12C	0.9800
C109—C110	1.377 (5)	C121—H12D	0.9800
C109—C114	1.376 (5)	C121—H12E	0.9800
C110—H110	0.9500	C121—H12F	0.9800
C110—C111	1.393 (5)
C107—O1—C109	123.2 (3)	C109—C114—H114	120.3
O2—N7—C115	126.2 (3)	C113—C114—C109	119.5 (3)
O2—N7—C117	121.3 (3)	C113—C114—H114	120.3
C115—N7—C117	112.2 (3)	N7—C115—C112	126.8 (3)
O3—N8—C115	125.9 (3)	N8—C115—N7	107.3 (3)
O3—N8—C116	121.2 (3)	N8—C115—C112	125.7 (3)
C115—N8—C116	112.5 (3)	N8—C116—C117	99.7 (2)
N5—C101—C103	177.3 (4)	N8—C116—C118	106.1 (3)
N6—C102—C104	176.3 (4)	N8—C116—C119	110.3 (3)
C104—C103—C101	120.6 (3)	C118—C116—C117	114.0 (3)
C108—C103—C101	119.1 (3)	C119—C116—C117	114.8 (3)
C108—C103—C104	120.3 (3)	C119—C116—C118	110.9 (3)
C103—C104—C102	118.9 (3)	N7—C117—C116	100.1 (2)
C105—C104—C102	121.5 (3)	C120—C117—N7	109.6 (3)
C105—C104—C103	119.7 (3)	C120—C117—C116	115.2 (3)
C104—C105—H105	119.7	C120—C117—C121	111.4 (3)
C106—C105—C104	120.5 (3)	C121—C117—N7	106.6 (3)
C106—C105—H105	119.7	C121—C117—C116	112.9 (3)
C105—C106—H106	120.5	C116—C118—H11A	109.5
C105—C106—C107	119.0 (3)	C116—C118—H11B	109.5
C107—C106—H106	120.5	C116—C118—H11C	109.5
O1—C107—C106	125.7 (3)	H11A—C118—H11B	109.5
O1—C107—C108	112.7 (3)	H11A—C118—H11C	109.5
C106—C107—C108	121.6 (3)	H11B—C118—H11C	109.5
C103—C108—C107	118.8 (3)	C116—C119—H11D	109.5
C103—C108—H108	120.6	C116—C119—H11E	109.5
C107—C108—H108	120.6	C116—C119—H11F	109.5
C110—C109—O1	123.7 (3)	H11D—C119—H11E	109.5
C114—C109—O1	114.1 (3)	H11D—C119—H11F	109.5
C114—C109—C110	121.8 (3)	H11E—C119—H11F	109.5
C109—C110—H110	120.8	C117—C120—H12A	109.5
C109—C110—C111	118.4 (3)	C117—C120—H12B	109.5
C111—C110—H110	120.8	C117—C120—H12C	109.5
C110—C111—H111	119.5	H12A—C120—H12B	109.5
C112—C111—C110	121.0 (3)	H12A—C120—H12C	109.5
C112—C111—H111	119.5	H12B—C120—H12C	109.5
C111—C112—C113	118.8 (3)	C117—C121—H12D	109.5
C111—C112—C115	122.3 (3)	C117—C121—H12E	109.5
C113—C112—C115	118.9 (3)	C117—C121—H12F	109.5
C112—C113—H113	119.8	H12D—C121—H12E	109.5
C114—C113—C112	120.5 (3)	H12D—C121—H12F	109.5
C114—C113—H113	119.8	H12E—C121—H12F	109.5
O1—C107—C108—C103	178.9 (3)	C109—O1—C107—C106	−6.6 (5)
O1—C109—C110—C111	173.5 (3)	C109—O1—C107—C108	172.4 (3)
O1—C109—C114—C113	−173.7 (3)	C109—C110—C111—C112	−0.7 (5)
O2—N7—C115—N8	−179.0 (3)	C110—C109—C114—C113	−0.3 (6)
O2—N7—C115—C112	−2.7 (5)	C110—C111—C112—C113	0.3 (5)
O2—N7—C117—C116	163.6 (3)	C110—C111—C112—C115	−177.0 (3)
O2—N7—C117—C120	42.0 (4)	C111—C112—C113—C114	0.1 (5)
O2—N7—C117—C121	−78.7 (4)	C111—C112—C115—N7	25.1 (5)
O3—N8—C115—N7	−174.2 (3)	C111—C112—C115—N8	−159.3 (3)
O3—N8—C115—C112	9.5 (5)	C112—C113—C114—C109	−0.1 (5)
O3—N8—C116—C117	160.8 (3)	C113—C112—C115—N7	−152.2 (3)
O3—N8—C116—C118	−80.6 (4)	C113—C112—C115—N8	23.5 (5)
O3—N8—C116—C119	39.6 (4)	C114—C109—C110—C111	0.6 (5)
N8—C116—C117—N7	26.2 (3)	C115—N7—C117—C116	−22.4 (3)
N8—C116—C117—C120	143.6 (3)	C115—N7—C117—C120	−144.0 (3)
N8—C116—C117—C121	−86.8 (3)	C115—N7—C117—C121	95.4 (3)
C101—C103—C104—C102	3.6 (5)	C115—N8—C116—C117	−25.6 (3)
C101—C103—C104—C105	−176.3 (3)	C115—N8—C116—C118	93.1 (3)
C101—C103—C108—C107	177.9 (3)	C115—N8—C116—C119	−146.8 (3)
C102—C104—C105—C106	179.1 (3)	C115—C112—C113—C114	177.5 (3)
C103—C104—C105—C106	−1.1 (5)	C116—N8—C115—N7	12.5 (4)
C104—C103—C108—C107	−0.2 (5)	C116—N8—C115—C112	−163.9 (3)
C104—C105—C106—C107	−1.2 (5)	C117—N7—C115—N8	7.3 (4)
C105—C106—C107—O1	−178.3 (3)	C117—N7—C115—C112	−176.4 (3)
C105—C106—C107—C108	2.8 (5)	C118—C116—C117—N7	−86.5 (3)
C106—C107—C108—C103	−2.1 (5)	C118—C116—C117—C120	31.0 (4)
C107—O1—C109—C110	57.1 (5)	C118—C116—C117—C121	160.6 (3)
C107—O1—C109—C114	−129.5 (3)	C119—C116—C117—N7	144.0 (3)
C108—C103—C104—C102	−178.4 (3)	C119—C116—C117—C120	−98.6 (4)
C108—C103—C104—C105	1.8 (5)	C119—C116—C117—C121	31.0 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C118—H11C···N5^i	0.98	2.57	3.469 (6)	153
C105—H105···O3^ii	0.95	2.43	3.282 (4)	149
C108—H108···O2^iii	0.95	2.59	3.476 (4)	155
C111—H111···O2	0.95	2.39	2.940 (4)	117
C113—H113···O3	0.95	2.27	2.859 (4)	119

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