Literature DB >> 29850059

Crystal structure of N,N'-bis-(2,4-di-fluoro-benzo-yloxy)benzene-1,2:4,5-tetra-carboximide.

Sandra Fusco1, Angela Tuzi1, Roberto Centore1, Antonio Carella1.   

Abstract

Mol-ecules of the title compound, C24H8F4N2O8, have Ci point-group symmetry in the crystal, as they lie on crystallographic inversion centres (Z' = 1/2). The di-fluoro-phenyl ring is disordered over two orientations; the final refined occupancy factors of the two components of disorder are 0.947 (4) and 0.053 (4). In the crystal, some Car-H⋯F inter-actions are present, which involve the most acidic H atom of the mol-ecule.

Entities:  

Keywords:  crystal structure; fluorine; imide; weak hydrogen bond

Year:  2018        PMID: 29850059      PMCID: PMC5956342          DOI: 10.1107/S2056989018001226

Source DB:  PubMed          Journal:  Acta Crystallogr E Crystallogr Commun


Chemical context

Heterocycles are key compounds in synthetic chemistry. In addition to their applications in drugs, bioactive and tautomeric compounds (D’Errico et al., 2012 ▸; Piccialli et al., 2007 ▸; Centore et al., 2013 ▸), aromatic heterocycles play an important role in modern materials chemistry, because they are used as building blocks of active mol­ecules in many emerging fields of advanced materials, for example, conducting polymers (Heeger, 2010 ▸), organic field-effect transistors (Miao, 2014 ▸), organic solar cells (Nielsen et al., 2015 ▸), liquid crystals (Centore et al., 1996 ▸) and nonlinear optically active compounds (Carella et al., 2007 ▸; Centore et al., 1999 ▸). Aromatic di­imides, in particular, are a class of heterocyclic compounds well known for their outstanding properties as n-type organic semiconductors. Very high electron mobilities have been measured for perylenedi­imides (Schmidt et al., 2007 ▸) and naphthalenedi­imides (Yan et al., 2009 ▸). The research on n-type organic semiconductors has also shown that electron mobilities and device performances can be improved by extensive replacement of H atoms by fluorine (Facchetti et al., 2003 ▸). Following these issues, we report here the structural investigation of the title compound, N,N′-bis­(2,4-di­fluoro­benzo­yloxy)benzene-1,2:4,5-tetra­carboximide, which is a fluorinated derivative of the simplest aromatic bis­(imide).

Structural commentary

Mol­ecules of the title compound in the crystal lie on crystallographic inversion centres and have C i point-group symmetry. Thus, the asymmetric unit is formed by half a mol­ecule, as shown in Fig. 1 ▸. The di­fluoro­phenyl ring is disordered over two orientations that differ by a rotation of 180° around the C6—C7 bond. The atomic positions for the two orientations of the di­fluoro­phenyl ring are completely superimposed for all atoms, except for the ortho-F atom, for which split positions were observed. The final refined occupancy factors of the two components of disorder are 0.947 (4) and 0.053 (4). Mol­ecules adopt a nonplanar conformation, mainly because of a torsion around the O3—N1 bond. In particular, the pentaa­tomic ring (atoms C2/C3/C4/N1/C5) is planar within 0.0164 (14) Å, while the phenyl ring (C7/C8a/C9/C10/C11/C12a) is planar within 0.002 (2) Å. The dihedral angle between the mean planes of the two rings is 86.14 (8)°.
Figure 1

The mol­ecular structure of the title compound, with displacement ellipsoids drawn at the 30% probability level. Only the most populated orientation of the disordered di­fluoro­phenyl ring is shown. [Symmetry code: (i) −x + 1, −y, −z + 1.]

The C6—O3 bond length [1.402 (3) Å] is significantly longer than the mean value for esters of aromatic acids (1.337 Å; Allen et al., 1987 ▸). This suggests a reduced contribution of the minor resonance form of the ester group, in which one of the lone pairs of the alk­oxy oxygen forms a double bond with the carbonyl C atom that breaks its double bond with the other O atom, thereby giving it a negative charge. This, in turn, can be due to the presence of the electronegative N atom bonded to O3.

Supra­molecular features

There are weak hydrogen-bond donors (Car—H) and strong hydrogen-bond acceptors (carbonyl O atoms) in the title compound. Moreover, F atoms are present as well, whose low hydrogen-bonding-acceptor capability, if any, has been the subject of a long debate in the literature (Dunitz & Taylor, 1997 ▸; Dunitz, 2004 ▸). Actually, it is now established that the C—H⋯F inter­action is generally weak and does not play a significant structural role in crystal packing when stronger and more polarizable acceptors than the C—F group are present. On the other hand, when the carbon acidity is suitably enhanced, and in the absence of competing acceptors, the (weak) hydrogen-bonding nature of the C—H⋯F inter­action is revealed (Thalladi et al., 1998 ▸). The most acidic Car—H group in the title compound is C9—H, because it has two ortho C—F-group neighbours. It is involved in weak hydrogen-bonding inter­actions with fluorine, as shown in Fig. 2 ▸ and Table 1 ▸. In particular, C9—H acts as bifurcated donor to the F1A and F2 atoms. In the first case, (8) ring motifs are formed across inversion centres. In the second case, chain patterns running parallel to a − b + c/2 are formed. These patterns are quite similar to the supra­molecular synthons II and IV reported in the Scheme 2 of Thalladi et al. (1998 ▸). It is quite remarkable that significant C—H⋯F inter­actions are only given by C9—H, which is the most acidic H atom of the mol­ecule.
Figure 2

Partial crystal packing of the title compound, showing the C—H⋯F and C—H⋯O inter­actions as dashed lines. Only the most populated orientation of the disordered di­fluoro­phenyl ring is shown.

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A D—HH⋯A DA D—H⋯A
C1—H1⋯O2i 0.952.373.271 (3)158
C9—H9⋯F1A ii 0.952.513.287 (3)139
C9—H9⋯F2iii 0.952.633.307 (3)129
C11—H11⋯O1iv 0.952.393.200 (3)143

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) .

Other acidic H atoms are C11—H, because it has one ortho C—F group, and C1—H. They are involved in weak hydrogen-bonding inter­actions with the O1 and O2 carbonyl acceptors, respectively, see Table 1 ▸ and Fig. 2 ▸.

Database survey

A search of the Cambridge Structural Database (CSD, Version 5.38, last update May 2017; Groom et al., 2016 ▸) gave no match for the title compound. We have searched for N-oxycarbonyl­imides using two filters (three-dimensional coordinates determined and not disordered). 47 hits were found. Within this set, 40 hits are N-oxycarbonyl derivatives of succinimide and 6 hits are derivatives of phthalimide. Here follows the full list of refcodes for the CSD search: ADEFUL, AFUXEE, ALOPAU, AWUXOF, BANTOA, CILBUV, COZFOM, DOFTEZ, EABXIO, EABXIO01, FUPPEM, GULRAI, GUVCAB, ICEWIY, LOZFAH, MAMDOU, MILFOE, MIPHUP, MIZJEM, MOZYOQ, NANWUU, OQUPOG, PIGKIZ, SEZWIE, SOSDEK, SUDJIM, SUDWUL, SUDXAS, SUDXAS01, TEQDEY, TUJRIB, UJAFER, UJUBOS, UJUBUY, VALSUZ, WALPEH, WIDKEB, YAFMEY, YAFPOL, YAGBEP, YUJZIN, YUJZOT, ZEPSES, ZEPSIW, ZOQQOL, ZOQQUR, ZALKUV. The hits found are crystal structures determined at temperatures in the range 90–298 K. In the 47 hits, the N1—O3 distance (DIST1) ranges between 1.375 and 1.408 Å, with an average value of 1.388 (6) Å. On the other hand, the distance O3—C6 (DIST2) is between 1.350 and 1.423 Å, with an average value of 1.393 (15) Å. The histogram of the distribution of DIST1 over the 47 hits found is shown in Fig. 3 ▸. The values of DIST1 and DIST2 found in the title compound [N1—O3 = 1.381 (2) Å and O3—C6 = 1.402 (3) Å] are fully consistent with the average values determined from the 47 hits.
Figure 3

Histogram of the N—O bond lengths (DIST1) in the 47 N-oxycarbonyl­imide hits found in the CSD search.

Synthesis and crystallization

N,N′-Di­hydroxy­benzene-1,2:4,5-tetra­carboximide (Centore & Carella, 2013 ▸) (1.000 g, 4.030 mmol) was suspended in 20 ml of dry pyridine and the system was kept under stirring at room tem­perature. 2,4-Di­fluoro­benzoyl­chloride (1.991 g, 11.28 mmol) was added dropwise and the previous suspension turned into a dark solution. The solution was warmed and boiled gently for 45 min. Absolute ethanol (2 ml) and, after 2 min, distilled water (0.2 ml) were then added and the system cooled slowly to room temperature and filtered. The white crystals were washed on the filter with absolute ethanol. From the recovered material it was possible to isolate several single crystals suitable for X-ray analysis. The yield was 55% (m.p. 604 K).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. The H atoms were generated stereochemically and were refined by the riding model. For all H atoms, U iso(H) = 1.2U eq(carrier). The di­fluoro­phenyl ring is disordered over two orientations, which differ by a rotation of 180° around the phenyl to carbonyl bond. Split positions were only observed for the ortho-F atom. The two split positions were refined by applying SADI restraints on bond lengths. The final refined occupancy factors of the two components of disorder are 0.947 (4) and 0.053 (4).
Table 2

Experimental details

Crystal data
Chemical formulaC24H8F4N2O8
M r 528.32
Crystal system, space groupMonoclinic, P21/c
Temperature (K)173
a, b, c (Å)17.100 (6), 4.744 (2), 13.662 (4)
β (°)106.83 (2)
V3)1060.8 (7)
Z 2
Radiation typeMo Kα
μ (mm−1)0.15
Crystal size (mm)0.40 × 0.15 × 0.01
 
Data collection
DiffractometerBruker–Nonius KappaCCD
Absorption correctionMulti-scan (SADABS; Bruker, 2001)
T min, T max 0.931, 0.986
No. of measured, independent and observed [I > 2σ(I)] reflections7948, 2396, 1440
R int 0.061
(sin θ/λ)max−1)0.650
 
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S 0.048, 0.120, 1.05
No. of reflections2396
No. of parameters176
No. of restraints1
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å−3)0.26, −0.32

Computer programs: COLLECT (Nonius, 1999 ▸), DIRAX/LSQ (Duisenberg et al., 2000 ▸), EVALCCD (Duisenberg et al., 2003 ▸), SIR97 (Altomare et al., 1999 ▸), SHELXL2016 (Sheldrick, 2015 ▸), ORTEP-3 for Windows and WinGX (Farrugia, 2012 ▸) and Mercury (Macrae et al., 2008 ▸).

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S2056989018001226/fy2124sup1.cif Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989018001226/fy2124Isup2.hkl CCDC reference: 1818213 Additional supporting information: crystallographic information; 3D view; checkCIF report
C24H8F4N2O8F(000) = 532
Mr = 528.32Dx = 1.654 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 17.100 (6) ÅCell parameters from 85 reflections
b = 4.744 (2) Åθ = 5.1–21.4°
c = 13.662 (4) ŵ = 0.15 mm1
β = 106.83 (2)°T = 173 K
V = 1060.8 (7) Å3Plate, colourless
Z = 20.40 × 0.15 × 0.01 mm
Bruker–Nonius KappaCCD diffractometer2396 independent reflections
Radiation source: normal-focus sealed tube1440 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.061
Detector resolution: 9 pixels mm-1θmax = 27.5°, θmin = 3.4°
CCD rotation images, thick slices scansh = −22→21
Absorption correction: multi-scan (SADABS; Bruker, 2001)k = −6→6
Tmin = 0.931, Tmax = 0.986l = −15→17
7948 measured reflections
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.048Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.120H-atom parameters constrained
S = 1.05w = 1/[σ2(Fo2) + (0.045P)2 + 0.4397P] where P = (Fo2 + 2Fc2)/3
2396 reflections(Δ/σ)max < 0.001
176 parametersΔρmax = 0.26 e Å3
1 restraintΔρmin = −0.32 e Å3
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 difluorophenyl ring is disordered over two orientations. The two split positions were refined by applying SADI restraints on bond lengths.
xyzUiso*/UeqOcc. (<1)
C10.53428 (13)−0.2108 (5)0.44840 (16)0.0196 (5)
H10.557147−0.3494970.4146680.024*
C20.47095 (12)−0.0358 (5)0.39704 (15)0.0177 (5)
C30.43844 (12)0.1672 (5)0.44705 (16)0.0191 (5)
C40.37402 (13)0.3243 (5)0.36996 (17)0.0226 (5)
C50.42706 (13)−0.0236 (5)0.28530 (16)0.0208 (5)
C60.24590 (14)0.1960 (6)0.15987 (18)0.0306 (6)
C70.19802 (14)0.3233 (6)0.06271 (17)0.0260 (5)
C90.07036 (16)0.3516 (7)−0.0723 (2)0.0406 (7)
H90.0153900.292807−0.1012320.049*
C100.10527 (16)0.5453 (7)−0.11934 (18)0.0354 (7)
C110.18428 (15)0.6341 (6)−0.08085 (19)0.0333 (6)
H110.2068360.769181−0.1163130.040*
C8A0.11781 (16)0.2431 (6)0.0194 (2)0.0369 (7)0.947 (4)
F1A0.08458 (11)0.0511 (5)0.06620 (15)0.0714 (8)0.947 (4)
C12A0.23029 (14)0.5223 (6)0.01072 (18)0.0289 (6)0.947 (4)
H12A0.2852050.5825530.0388930.035*0.947 (4)
C8B0.11781 (16)0.2431 (6)0.0194 (2)0.0369 (7)0.053 (4)
H8B0.0944360.1080790.0539330.044*0.053 (4)
C12B0.23029 (14)0.5223 (6)0.01072 (18)0.0289 (6)0.053 (4)
F1B0.3060 (9)0.615 (6)0.037 (2)0.043*0.053 (4)
F20.05967 (10)0.6562 (4)−0.20823 (12)0.0554 (6)
N10.37352 (12)0.1997 (5)0.27779 (14)0.0256 (5)
O10.33327 (10)0.5199 (4)0.38057 (13)0.0315 (4)
O20.43410 (10)−0.1664 (4)0.21582 (12)0.0258 (4)
O30.32607 (9)0.2995 (4)0.18452 (11)0.0268 (4)
O40.22619 (12)0.0326 (6)0.21309 (16)0.0623 (8)
U11U22U33U12U13U23
C10.0185 (10)0.0213 (12)0.0195 (10)0.0013 (10)0.0062 (8)0.0007 (10)
C20.0187 (10)0.0186 (12)0.0162 (9)−0.0022 (9)0.0056 (8)0.0006 (9)
C30.0162 (10)0.0209 (12)0.0195 (10)−0.0013 (9)0.0040 (8)0.0037 (10)
C40.0197 (10)0.0247 (13)0.0220 (11)0.0006 (10)0.0038 (8)0.0030 (11)
C50.0214 (10)0.0206 (12)0.0189 (10)−0.0006 (10)0.0037 (8)0.0034 (10)
C60.0236 (12)0.0388 (16)0.0262 (12)−0.0060 (12)0.0023 (10)0.0058 (12)
C70.0241 (11)0.0309 (14)0.0197 (11)−0.0020 (11)0.0012 (9)0.0036 (11)
C90.0254 (12)0.055 (2)0.0326 (14)−0.0102 (13)−0.0051 (10)0.0056 (14)
C100.0307 (13)0.0479 (18)0.0209 (11)0.0052 (13)−0.0034 (10)0.0070 (13)
C110.0286 (12)0.0401 (17)0.0294 (13)−0.0004 (12)0.0055 (10)0.0120 (12)
C8A0.0308 (13)0.0423 (17)0.0331 (14)−0.0113 (13)0.0021 (11)0.0098 (13)
F1A0.0388 (10)0.0959 (19)0.0636 (13)−0.0361 (11)−0.0101 (9)0.0451 (13)
C12A0.0209 (11)0.0368 (16)0.0262 (11)−0.0034 (11)0.0021 (9)0.0042 (12)
C8B0.0308 (13)0.0423 (17)0.0331 (14)−0.0113 (13)0.0021 (11)0.0098 (13)
C12B0.0209 (11)0.0368 (16)0.0262 (11)−0.0034 (11)0.0021 (9)0.0042 (12)
F20.0409 (9)0.0744 (14)0.0363 (9)−0.0026 (9)−0.0119 (7)0.0227 (9)
N10.0271 (10)0.0289 (12)0.0162 (9)0.0073 (9)−0.0010 (7)0.0046 (9)
O10.0284 (9)0.0306 (10)0.0324 (9)0.0103 (8)0.0037 (7)0.0007 (8)
O20.0313 (9)0.0267 (10)0.0194 (8)0.0009 (7)0.0074 (7)−0.0017 (8)
O30.0214 (8)0.0352 (10)0.0180 (7)0.0013 (8)−0.0035 (6)0.0083 (8)
O40.0424 (12)0.0860 (19)0.0466 (12)−0.0228 (12)−0.0057 (9)0.0414 (13)
C1—C21.384 (3)C7—C12A1.388 (4)
C1—C3i1.384 (3)C9—C101.355 (4)
C1—H10.9500C9—C8B1.379 (4)
C2—C31.387 (3)C9—C8A1.379 (4)
C2—C51.494 (3)C9—H90.9500
C3—C41.485 (3)C10—F21.346 (3)
C4—O11.194 (3)C10—C111.367 (4)
C4—N11.389 (3)C11—C12B1.377 (3)
C5—O21.200 (3)C11—C12A1.377 (3)
C5—N11.384 (3)C11—H110.9500
C6—O41.177 (3)C8A—F1A1.331 (3)
C6—O31.402 (3)C12A—H12A0.9500
C6—C71.472 (3)C8B—H8B0.9500
C7—C8B1.381 (3)C12B—F1B1.315 (10)
C7—C8A1.381 (3)N1—O31.381 (2)
C7—C12B1.388 (4)
C2—C1—C3i114.5 (2)C10—C9—H9121.3
C2—C1—H1122.8C8A—C9—H9121.3
C3i—C1—H1122.8F2—C10—C9118.3 (2)
C1—C2—C3122.23 (19)F2—C10—C11118.5 (3)
C1—C2—C5129.0 (2)C9—C10—C11123.3 (2)
C3—C2—C5108.78 (19)C10—C11—C12B118.2 (2)
C1i—C3—C2123.3 (2)C10—C11—C12A118.2 (2)
C1i—C3—C4128.0 (2)C10—C11—H11120.9
C2—C3—C4108.65 (19)C12A—C11—H11120.9
O1—C4—N1126.2 (2)F1A—C8A—C9118.1 (2)
O1—C4—C3130.0 (2)F1A—C8A—C7119.4 (2)
N1—C4—C3103.76 (19)C9—C8A—C7122.5 (2)
O2—C5—N1126.1 (2)C11—C12A—C7121.3 (2)
O2—C5—C2130.6 (2)C11—C12A—H12A119.3
N1—C5—C2103.36 (19)C7—C12A—H12A119.3
O4—C6—O3121.1 (2)C9—C8B—C7122.5 (2)
O4—C6—C7130.0 (2)C9—C8B—H8B118.8
O3—C6—C7108.8 (2)C7—C8B—H8B118.8
C8B—C7—C12B117.4 (2)F1B—C12B—C11112.2 (13)
C8A—C7—C12A117.4 (2)F1B—C12B—C7126.4 (13)
C8B—C7—C6119.9 (2)C11—C12B—C7121.3 (2)
C8A—C7—C6119.9 (2)O3—N1—C5122.00 (19)
C12B—C7—C6122.7 (2)O3—N1—C4122.6 (2)
C12A—C7—C6122.7 (2)C5—N1—C4115.35 (19)
C10—C9—C8B117.4 (2)N1—O3—C6111.96 (18)
C10—C9—C8A117.4 (2)
C3i—C1—C2—C30.5 (4)C10—C9—C8A—F1A−179.5 (3)
C3i—C1—C2—C5179.9 (2)C10—C9—C8A—C7−0.5 (5)
C1—C2—C3—C1i−0.5 (4)C12A—C7—C8A—F1A179.5 (3)
C5—C2—C3—C1i180.0 (2)C6—C7—C8A—F1A0.1 (4)
C1—C2—C3—C4178.0 (2)C12A—C7—C8A—C90.4 (4)
C5—C2—C3—C4−1.6 (3)C6—C7—C8A—C9−179.0 (3)
C1i—C3—C4—O11.0 (4)C10—C11—C12A—C70.5 (4)
C2—C3—C4—O1−177.4 (3)C8A—C7—C12A—C11−0.4 (4)
C1i—C3—C4—N1178.1 (2)C6—C7—C12A—C11179.0 (3)
C2—C3—C4—N1−0.2 (2)C10—C9—C8B—C7−0.5 (5)
C1—C2—C5—O23.1 (4)C12B—C7—C8B—C90.4 (4)
C3—C2—C5—O2−177.4 (2)C6—C7—C8B—C9−179.0 (3)
C1—C2—C5—N1−176.8 (2)C10—C11—C12B—F1B177.2 (15)
C3—C2—C5—N12.7 (2)C10—C11—C12B—C70.5 (4)
O4—C6—C7—C8B−2.9 (5)C8B—C7—C12B—F1B−176.7 (17)
O3—C6—C7—C8B176.6 (3)C6—C7—C12B—F1B2.7 (18)
O4—C6—C7—C8A−2.9 (5)C8B—C7—C12B—C11−0.4 (4)
O3—C6—C7—C8A176.6 (3)C6—C7—C12B—C11179.0 (3)
O4—C6—C7—C12B177.8 (3)O2—C5—N1—O3−6.0 (4)
O3—C6—C7—C12B−2.7 (4)C2—C5—N1—O3173.86 (19)
O4—C6—C7—C12A177.8 (3)O2—C5—N1—C4177.1 (2)
O3—C6—C7—C12A−2.7 (4)C2—C5—N1—C4−3.0 (3)
C8B—C9—C10—F2−179.2 (3)O1—C4—N1—O32.6 (4)
C8A—C9—C10—F2−179.2 (3)C3—C4—N1—O3−174.73 (19)
C8B—C9—C10—C110.6 (5)O1—C4—N1—C5179.4 (2)
C8A—C9—C10—C110.6 (5)C3—C4—N1—C52.1 (3)
F2—C10—C11—C12B179.2 (3)C5—N1—O3—C699.6 (3)
C9—C10—C11—C12B−0.5 (5)C4—N1—O3—C6−83.7 (3)
F2—C10—C11—C12A179.2 (3)O4—C6—O3—N1−3.5 (4)
C9—C10—C11—C12A−0.5 (5)C7—C6—O3—N1176.9 (2)
D—H···AD—HH···AD···AD—H···A
C1—H1···O2ii0.952.373.271 (3)158
C9—H9···F1Aiii0.952.513.287 (3)139
C9—H9···F2iv0.952.633.307 (3)129
C11—H11···O1v0.952.393.200 (3)143
  9 in total

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Authors:  Qian Miao
Journal:  Adv Mater       Date:  2014-03-02       Impact factor: 30.849

3.  Semiconducting polymers: the Third Generation.

Authors:  Alan J Heeger
Journal:  Chem Soc Rev       Date:  2010-01-21       Impact factor: 54.564

4.  A high-mobility electron-transporting polymer for printed transistors.

Authors:  He Yan; Zhihua Chen; Yan Zheng; Christopher Newman; Jordan R Quinn; Florian Dötz; Marcel Kastler; Antonio Facchetti
Journal:  Nature       Date:  2009-01-21       Impact factor: 49.962

5.  Crystal structure refinement with SHELXL.

Authors:  George M Sheldrick
Journal:  Acta Crystallogr C Struct Chem       Date:  2015-01-01       Impact factor: 1.172

6.  A facile synthesis of 5'-fluoro-5'-deoxyacadesine (5'-F-AICAR): a novel non-phosphorylable AICAR analogue.

Authors:  Stefano D'Errico; Giorgia Oliviero; Nicola Borbone; Jussara Amato; Daniele D'Alonzo; Vincenzo Piccialli; Luciano Mayol; Gennaro Piccialli
Journal:  Molecules       Date:  2012-11-02       Impact factor: 4.411

7.  N,N'-Di-hydroxy-benzene-1,2:4,5-tetra-carboximide dihydrate.

Authors:  Roberto Centore; Antonio Carella
Journal:  Acta Crystallogr Sect E Struct Rep Online       Date:  2013-06-26

8.  The Cambridge Structural Database.

Authors:  Colin R Groom; Ian J Bruno; Matthew P Lightfoot; Suzanna C Ward
Journal:  Acta Crystallogr B Struct Sci Cryst Eng Mater       Date:  2016-04-01

9.  Non-fullerene electron acceptors for use in organic solar cells.

Authors:  Christian B Nielsen; Sarah Holliday; Hung-Yang Chen; Samuel J Cryer; Iain McCulloch
Journal:  Acc Chem Res       Date:  2015-10-27       Impact factor: 22.384

  9 in total

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