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Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 80| Part 8| August 2024| Pages 867-872
https://doi.org/10.1107/S2056989024006819

Synthesis, mol­ecular and crystal structures of 4-amino-3,5-di­fluoro­benzo­nitrile, ethyl 4-amino-3,5-di­fluoro­benzoate, and di­ethyl 4,4′-(diazene-1,2-di­yl)bis­­(3,5-di­fluoro­benzoate)

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Egor M. Novikov,a* Jesus Guillen Campos,b Javier Read de Alaniz,b Marina S. Fonaric and Tatiana V. Timofeevaa

aDepartment of Chemistry, New Mexico Highlands University, Las Vegas, New Mexico, 87701, USA, bDepartment of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, CA 93106, USA, and cInstitute of Applied Physics, Academy Str., 5 MD2028, Chisinau, Moldova
*Correspondence e-mail: enovikov@live.nmhu.edu

Edited by V. Jancik, Universidad Nacional Autónoma de México, México (Received 21 February 2024; accepted 11 July 2024; online 19 July 2024)

The crystal structures of two inter­mediates, 4-amino-3,5-di­fluoro­benzo­nitrile, C7H4F2N2 (I), and ethyl 4-amino-3,5-di­fluoro­benzoate, C9H9F2NO2 (II), along with a visible-light-responsive azo­benzene derivative, diethyl 4,4′-(diazene-1,2-di­yl)bis­(3,5-di­fluoro­benzoate), C18H14F4N2O4 (III), obtained by four-step synthetic procedure, were studied using single-crystal X-ray diffraction. The mol­ecules of I and II demonstrate the quinoid character of phenyl rings accompanied by the distortion of bond angles related to the presence of fluorine substituents in the 3 and 5 (ortho) positions. In the crystals of I and II, the mol­ecules are connected by N—H⋯N, N—H⋯F and N—H⋯O hydrogen bonds, C—H⋯F short contacts, and π-stacking inter­actions. In crystal of III, only stacking inter­actions between the mol­ecules are found.

CCDC references: 2370064; 2370063; 2370062

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1. Chemical context

Azo­benzene and its derivatives have different absorbance depending on the mol­ecular conformation (trans or cis) around the central N=N bond (Mostad & Rømming, 1971[Mostad, A. & Rømming, C. (1971). Acta Chem. Scand. 25, 3561-3568.]; Harada et al., 1997[Harada, J., Ogawa, K. & Tomoda, S. (1997). Acta Cryst. B53, 662-672.]) and mol­ecular architecture. Recently, derivatives of azo­benzene, known as pharmacophores, whose activity can be altered via the application of excitation sources with different wavelengths, started being used as mol­ecular tools for controlling biological processes (Aggarwal et al., 2020[Aggarwal, K., Kuka, T. P., Banik, M., Medellin, B. P., Ngo, C. Q., Xie, D., Fernandes, Y., Dangerfield, T. L., Ye, E., Bouley, B., Johnson, K. A., Zhang, Y. J., Eberhart, J. K. & Que, E. L. (2020). J. Am. Chem. Soc. 142, 14522-14531.]; Gutzeit et al., 2021[Gutzeit, V. A., Acosta-Ruiz, A., Munguba, H., Häfner, S., Landra-Willm, A., Mathes, B., Mony, J., Yarotski, D., Börjesson, K., Liston, C., Sandoz, G., Levitz, J. & Broichhagen, J. (2021). Cell. Chem. Biol. 28, 1648-1663.e16.]). The development of new pharmacophores can be achieved via alteration of the mol­ecular properties by changing the chemical structure, shape, polarity, and other mol­ecular characteristics.

It was indicated (Bléger et al., 2012[Bléger, D., Schwarz, J., Brouwer, A. M. & Hecht, S. (2012). J. Am. Chem. Soc. 134, 20597-20600.]; Knie et al., 2014[Knie, C., Utecht, M., Zhao, F., Kulla, H., Kovalenko, S., Brouwer, A. M., Saalfrank, P., Hecht, S. & Bléger, D. (2014). Chem. Eur. J. 20, 16492-16501.]) that fluorination of benzene rings in azo­benzene in ortho positions to the N=N group along with the introduction of electron-withdrawing groups in a para position can help to achieve higher isomer conversion to the cis form when compared to other azo­benzene derivatives. In addition, it was observed that the thermal stability of the cis isomers of ortho fluorinated azo­benzenes compared to non-fluorinated materials was significantly increased from 5 h to 700 days (Bléger et al., 2012[Bléger, D., Schwarz, J., Brouwer, A. M. & Hecht, S. (2012). J. Am. Chem. Soc. 134, 20597-20600.]).

Another inter­esting application of azo­benzene-based organic materials was presented by Peng and co-workers (Peng et al., 2022[Peng, H., Qi, H.-J., Song, X.-J., Xiong, R.-G. & Liao, W.-Q. (2022). Chem. Sci. 13, 4936-4943.]), who demonstrated that the non-centrosymmetric 2-amino-2′,4,4′,6,6′-penta­fluoro­azo­benzene was a single-component ferroelectric. In that publication, it was stated that the above-mentioned material was the first single-component organic ferroelectric that opened the way to the design and exploration of azo­benzene-based ferroelectrics with promising applications in biofriendly ferroelectric devices.

[Scheme 1]

Herein, the synthetic protocols for two inter­mediates, 4-amino-3,5-di­fluoro­benzo­nitrile (I), ethyl 4-amino-3,5-di­fluoro­benzoate (II), and an azo­benzene derivative with the fluorine atoms in ortho-positions and ester group in a para- position, namely, diethyl-4,4′-(2,2′,6,6′-tetra­fluoro)­azo­benzene di­carboxyl­ate (III) obtained in four-step synthesis using a modified synthetic procedure (Appiah et al., 2017[Appiah, C., Woltersdorf, G. & Binder, W. H. (2017). Polym. Chem. 8, 2752-2763.]) are reported along with the comprehensive X-ray structural study of these materials in the solid state. The synthesized azo­benzene derivative might be used as a precursor for further development and application in photopharmacological studies. It has been shown that fluorinated azo­benzenes can be used also for the synthesis of photoresponsive main-chain oligomers with azo­benzene moieties incorporated in linear unsaturated or saturated polyolefins on a gram scale (Appiah et al., 2017[Appiah, C., Woltersdorf, G. & Binder, W. H. (2017). Polym. Chem. 8, 2752-2763.]).

2. Structural commentary

The geometric parameters of mol­ecule I (Table 1[link], Fig. 1[link]) are very similar to those found in related structures lacking fluorine substituents. For example, a comparison of the geometrical parameters of I with those of 4-amino­benzo­nitrile (Merlino & Sartori, 1982[Merlino, S. & Sartori, F. (1982). Acta Cryst. B38, 1476-1480.]; Heine et al., 1994[Heine, A., Herbst-Irmer, R., Stalke, D., Kühnle, W. & Zachariasse, K. A. (1994). Acta Cryst. B50, 363-373.]; Islor et al., 2013[Islor, A. M., Chandrakantha, B., Gerber, T., Hosten, E. & Betz, R. (2013). Z. Kristallogr. 228, 217-218.]; Alimi et al., 2018[Alimi, L. O., van Heerden, D. P., Lama, P., Smith, V. J. & Barbour, L. J. (2018). Chem. Commun. 54, 6208-6211.]) in which there are no fluorine substituents, shows their similarity. However, while in 4-amino­benzo­nitrile (Alimi et al., 2018[Alimi, L. O., van Heerden, D. P., Lama, P., Smith, V. J. & Barbour, L. J. (2018). Chem. Commun. 54, 6208-6211.]), the angles in the phenyl ring are almost the same (from 118.5 to 120.8°), in I, the C6—C5—C4 angle with the value 114.5 (1)° is more acute than the C7—C6—C5 [124.4 (1)°] and C5—C4—C3 [124.2 (1)°] angles, mainly due to the influence of highly electronegative fluorine substituents. It also can be noted, that the cyano group bond length C1≡N1 [1.146 (2) Å] is slightly longer than the literature value (1.136 Å; Allen et al., 1987[Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1-S19.]). Increased conjugation can lead to a slight reduction in bond order, potentially lengthening and somewhat weakening the triple bond compared to a non-conjugated nitrile (Allen et al., 1987[Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1-S19.]).

Table 1
Selected bond lengths (Å) in mol­ecules of I–III

Bond/Compound I II III
1 1.373 (2) 1.372 (4) 1.373 (3)
2 1.377 (2) 1.365 (4) 1.373 (3)
3 1.360 (1) 1.360 (3) 1.345 (2)
4 1.360 (1) 1.368 (3) 1.341 (2)
5 – – 1.252 (3)
[Figure 1]
Figure 1
Mol­ecular structures of I, II, III with the atomic numbering schemes. Displacement ellipsoids are drawn at the 50% probability level. Symmetry code: (′) 1 − x, 1 − y, 2 − z for III.

Likewise, the bond lengths and angles in II (Table 1[link], Fig. 1[link]) are very similar to those reported previously for related structures, for instance, for the mol­ecule of ethyl-4-amino­benzoate (similar to mol­ecule II, without fluorine substit­uents) that was reported in several publications (Lynch & McClenaghan, 2002[Lynch, D. E. & McClenaghan, I. (2002). Acta Cryst. E58, o708-o709.]; Chan & Welberry, 2010[Chan, E. J. & Welberry, T. R. (2010). Acta Cryst. B66, 260-270.]; Patyk-Kaźmierczak & Kaźmierczak, 2020[Patyk-Kaźmierczak, E. & Kaźmierczak, M. (2020). Acta Cryst. B76, 56-64.]). The mol­ecular structure in the most recent paper (Patyk-Kaźmierczak & Kaźmierczak, 2020[Patyk-Kaźmierczak, E. & Kaźmierczak, M. (2020). Acta Cryst. B76, 56-64.]) demonstrated equal distances of 1.390 Å between the carbon atoms in the phenyl ring.

The geometric parameters of mol­ecule III (Table 1[link], Fig. 1[link]) are very similar to those found in related structures. There are few structures reported in the literature (Kerckhoffs et al., 2022[Kerckhoffs, A., Christensen, K. E. & Langton, M. J. (2022). Chem. Sci. 13, 11551-11559.]; Hermann et al., 2017[Hermann, D., Schwartz, H. A. & Ruschewitz, U. (2017). ChemistrySelect, 2, 11846-11852.]; Bushuyev et al., 2016[Bushuyev, O. S., Tomberg, A., Vinden, J. R., Moitessier, N., Barrett, C. J. & Friščić, T. (2016). Chem. Commun. 52, 2103-2106.]; Saccone et al., 2014[Saccone, M., Terraneo, G., Pilati, T., Cavallo, G., Priimagi, A., Metrangolo, P. & Resnati, G. (2014). Acta Cryst. B70, 149-156.], and Aggarwal et al., 2020[Aggarwal, K., Kuka, T. P., Banik, M., Medellin, B. P., Ngo, C. Q., Xie, D., Fernandes, Y., Dangerfield, T. L., Ye, E., Bouley, B., Johnson, K. A., Zhang, Y. J., Eberhart, J. K. & Que, E. L. (2020). J. Am. Chem. Soc. 142, 14522-14531.]) featuring trans-azo­benzene with halogen substituents at the 2- and 6-positions. However, there are two structures that have been found to incorporate the diethyl-4,4′-azo­benzene di­carboxyl­ate moiety (Niu et al., 2011[Niu, Y., Huang, J., Zhao, C., Gao, P. & Yu, Y. (2011). Acta Cryst. E67, o2671.]; Gajda et al., 2014[Gajda, K., Zarychta, B., Daszkiewicz, Z., Domański, A. A. & Ejsmont, K. (2014). Acta Cryst. C70, 575-579.]). In both those structures, the mol­ecules are planar. The title structure III is centrosymmetric, the phenyl rings are planar. The N1=N1′ distance [1.252 (3) Å] is very close to the distances presented in the literature. In the mol­ecule of II, the C7=O1 distance is 1.212 (4) Å, and in the mol­ecule of III the distance C7=O1 is equal to 1.211 (2) Å. Those values are close to the statistical mean value of 1.221 Å (Allen et al., 1987[Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1-S19.]).

For a convenient comparison of the mol­ecular geometries of I–III, some bond lengths and their notations are presented in Scheme 1 and Table 1[link]. From Table 1[link], it is clear that in all mol­ecules the C—F bonds are characterized by very similar bond lengths. As a result of the para position of the donor and acceptor substituents of the phenyl rings, it is expected that this ring should have quinoid character (Zyss, 1994[Zyss, J. (1994). Editor. Molecular Nonlinear Optics, 1st ed. New York: Academic Press.]). Indeed, bond lengths 1 and 2 (see Scheme 1 and Table 1[link]) are reduced if compared with the other bond lengths in the phenyl rings (see supporting information).

The length of the double N=N bond in mol­ecule III corresponds to a standard value for this series of compounds. Using CSD Version 5.45 (update of June 2024; Groom et al., 2016[Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171-179.]), a statistical analysis of the N=N bonds in 2261 Ph—N=N—Ph fragments from 1733 crystal structures was carried out. A histogram of the bond-length distribution with a mean bond value of 1.246 Å, median 1.253 Å and su 0.034 Å is presented in Fig. 2[link]. It clearly demonstrates that the central bond length in mol­ecule III corresponds to the median value of such bonds.

[Figure 2]
Figure 2
Histogram of N=N bond-length distribution in azo­benzene derivatives.

The mol­ecule of III, in contrast to the previously studied mol­ecule of diethyl 4,4′-(diazenedi­yl)dibenzoate (DDB; Niu et al., 2011[Niu, Y., Huang, J., Zhao, C., Gao, P. & Yu, Y. (2011). Acta Cryst. E67, o2671.]) without F substituents, is not planar. The torsion angle that characterizes the position of the phenyl rings relative to the central C—N=N—C fragment is equal to 17.2 (3) ° in III and 0.2 (2) ° in DDB. It can be explained by the intra­molecular steric inter­actions between F and N atoms in III, N1⋯F1 = 2.644 (2) Å and N1⋯F2 = 2.945 (2) Å, which are slightly shorter than sum of van der Waals radii (Batsanov, 2001[Batsanov, S. S. (2001). Inorg. Mater. 37, 871-885.]). An overlay of mol­ecules III and DDB demonstrates the mol­ecular similarity with the exception of the orientation of the terminal Me groups (See Fig. 3[link]).

[Figure 3]
Figure 3
Overlay of mol­ecules III (red) and DDB (green) with r.m.s. 0.121.

3. Supra­molecular features

The packing in the crystal of I is defined by weak N–H⋯N and N–H⋯F H-bonds (Fig. 4[link] and Table 2[link]), and π-stacking inter­actions with inter­planar distances between the overlapping phenyl rings equal to 3.3573 (8) Å and distances between the ring centroids equal to 3.7283 (4) Å. The parameters of the short contacts correspond to the average D⋯A distances for specific inter­actions [N—H⋯N = 2.9–3.0 Å (Prasad & Govil, 1980[Prasad, N. & Govil, G. (1980). Proc. - Indian Acad. Sci. Chem. Sci. 89, 253-262.]) and N—H⋯F = 2.427 Å (Taylor, 2017[Taylor, R. (2017). Acta Cryst. B73, 474-488.])]. Inter­planar distances for stacking inter­actions are slightly shorter than the inter­planar distance in graphite (3.42 Å), indicating the significant role of stacking inter­actions in this crystal. As a result of the hydrogen bonding, mol­ecules of I form chains along the (101) direction.

Table 2
Hydrogen-bond geometry (Å, °) for I[link]

D—H⋯A D—H H⋯A D⋯A D—H⋯A
N2—H2A⋯N1i 0.82 (2) 2.28 (2) 3.0297 (17) 153 (2)
N2—H2B⋯F2ii 0.88 (2) 2.38 (2) 3.2526 (15) 173.9 (19)
Symmetry codes: (i) [x+{\script{1\over 2}}, -y+{\script{3\over 2}}, z-{\script{1\over 2}}]; (ii) [-x+{\script{3\over 2}}, y-{\script{1\over 2}}, -z+{\script{1\over 2}}].
[Figure 4]
Figure 4
The packing in the crystal of I. Hydrogen bonds are shown as dotted lines. Hydrogen atoms not participating in hydrogen bonding are omitted for clarity.

In the crystal of II, N—H⋯O hydrogen bonds and C—H⋯F short contacts are found (Fig. 5[link], Table 3[link]) as well as π–π-stacking inter­actions with inter­planar distances between phenyl rings equal to 3.325 (3) Å and distances between ring centroids of 3.490 (3) Å. The parameters of the short contacts correspond to the average D⋯A distances for specific inter­actions (N—H⋯O = 2.7–3.3 Å (Bakker et al., 2023[Bakker, R., Bairagi, A., Rodríguez, M., Tripodi, L. G., Pereverzev, Y. A. & Roithová, J. (2023). Inorg. Chem. 62, 1728-1734.]) and N—H⋯F = 2.427 (6) Å (Taylor, 2017[Taylor, R. (2017). Acta Cryst. B73, 474-488.])]. As a result of hydrogen bonding, mol­ecules of II form chains along the b-axis direction. In the structures of both I and II, short intra­molecular contacts of the type N–H⋯F are observed.

Table 3
Hydrogen-bond geometry (Å, °) for II[link]

D—H⋯A D—H H⋯A D⋯A D—H⋯A
N1—H1A⋯O1i 0.85 (3) 2.15 (4) 2.942 (3) 155 (3)
C8—H8B⋯F1ii 0.99 2.46 3.015 (3) 115
Symmetry codes: (i) [x, y-1, z]; (ii) [x, y+1, z].
[Figure 5]
Figure 5
The packing in the crystal of II. Hydrogen bonds are shown as dashed lines. Hydrogen atoms not participating in hydrogen bonding are omitted for clarity.

The relative orientations of the mol­ecular cores in structure III (Fig. 6[link]) and in the analogous crystal structure of trans-1,2-bis­(4-bromo-2,6-di­fluoro­phen­yl)diazene (Broichhagen et al., 2015[Broichhagen, J., Woodmansee, D. H., Trauner, D. & Mayer, P. (2015). Acta Cryst. E71, o459-o460.]) are similar. In the crystal of III, the inter­planar distance between the mol­ecular core containing the phenyl rings and the N=N bond is 3.324 (13) Å and inter­centroid distance is 4.6106 (17) Å. The nearest distance of the azo group N atom to the carbon atom in the phenyl ring N1⋯C6 is 3.184 (3) Å, and the distance to the ring centroid is 3.465 (19) Å. The distance between carbonyl atom O1 and the nearest C atom in the phenyl ring is 3.316 (2) Å and to the ring centroid is 3.351 (18) Å. As a result of π–π stacking, the mol­ecules of III form chains along the [01[\overline{1}]] direction.

[Figure 6]
Figure 6
The packing in the crystal of III. Stacking short contacts are shown as dashed lines. Hydrogen atoms are omitted for clarity. N1⋯C6(−x, 1 − y, 2 − z) = 3.184 (3) Å.

4. Database survey

A search of the Cambridge Structural Database (CSD version 5.45, update of June 2024; Groom et al., 2016[Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171-179.]) for 4-amino-3,5-di­fluoro­benzo­nitrile (I) revealed that the structure had not previously been published. However, a similar structure without fluorine substituents in the ring, 4-amino-benzo­nitrile, had been described and demonstrated the possibility of different polymorphs [Alimi et al., 2018[Alimi, L. O., van Heerden, D. P., Lama, P., Smith, V. J. & Barbour, L. J. (2018). Chem. Commun. 54, 6208-6211.] (BERTOH03); Merlino & Sartori, 1982[Merlino, S. & Sartori, F. (1982). Acta Cryst. B38, 1476-1480.] (BERTOH); Heine et al., 1994[Heine, A., Herbst-Irmer, R., Stalke, D., Kühnle, W. & Zachariasse, K. A. (1994). Acta Cryst. B50, 363-373.] (BERTOH01); Islor et al., 2013[Islor, A. M., Chandrakantha, B., Gerber, T., Hosten, E. & Betz, R. (2013). Z. Kristallogr. 228, 217-218.] (BERTOH02)] all of which crystallize in centrosymmetric space groups, except for BERTOH01 (Heine et al., 1994[Heine, A., Herbst-Irmer, R., Stalke, D., Kühnle, W. & Zachariasse, K. A. (1994). Acta Cryst. B50, 363-373.]) which crystallizes in the non-centrosymmetric P212121 space group.

The novelty of 4-amino-3,5-di­fluoro­benzoate (II) was also confirmed by the lack of this structure in the CSD. The closest analogue without fluorine substituents in the phenyl ring is ethyl 4-amino-benzoate (benzocaine), an anesthetic applied in medicine and the pharmaceutical industry and described as 19 database entries. Eight of the structures were reported by Patyk-Kaźmierczak & Kaźmierczak (2020[Patyk-Kaźmierczak, E. & Kaźmierczak, M. (2020). Acta Cryst. B76, 56-64.]) (QQQAXG11–18), which represent several polymorphs in the same P21/c space group but with different cell parameters. Other structures were reported by Patel et al. (2017[Patel, M. A., AbouGhaly, M. H. H. & Chadwick, K. (2017). Int. J. Pharm. 532, 166-176.]) (QQQAXG09–10) where two polymorphs of benzocaine were described in space groups P212121 and P21/c. Earlier, these structures were mentioned by Chan & Welberry (2010[Chan, E. J. & Welberry, T. R. (2010). Acta Cryst. B66, 260-270.]) and Lynch & McClenaghan (2002[Lynch, D. E. & McClenaghan, I. (2002). Acta Cryst. E58, o708-o709.]).

The structure of diethyl-4,4′-(2,2′,6,6′-tetra­fluoro)­azo­benzene di­carboxyl­ate (III) had also not been deposited in the CSD. However, similar tetra-halogenated mol­ecules with the halogens in ortho positions have been described (Kerckhoffs et al., 2022[Kerckhoffs, A., Christensen, K. E. & Langton, M. J. (2022). Chem. Sci. 13, 11551-11559.]; TETROD). It should be mentioned that mol­ecules of cis and trans (Z and E) isomers were structurally characterized when it was possible to separate them and when the cis isomers had a long half-life to facilitate their isolation. The authors showed that it was possible to modify the stability of the cis isomers by introducing larger halogen atoms in the ortho positions and a heavier element substituent in the para position. If the azo-benzene mol­ecules with small substituents (H, F) in the ortho positions are planar, with larger halogens (I)[link] they are non-planar, and their cis isomers are more stable. It is important to mention that the ortho-tetra­fluoro­azo­benzenes (DIQBOX; Hermann et al., 2017[Hermann, D., Schwartz, H. A. & Ruschewitz, U. (2017). ChemistrySelect, 2, 11846-11852.]) resulting from isomerization of the mol­ecule, resulted in significant shape changes, with the trans isomer exhibiting elongation and the cis isomer adopting a more spherical shape. In addition, diethyl-4,4′-azo­benzene di­carboxyl­ate, which represents the non-halogenated analogue of compound III [Niu et al., 2011[Niu, Y., Huang, J., Zhao, C., Gao, P. & Yu, Y. (2011). Acta Cryst. E67, o2671.] (AZUKAI); Gajda et al., 2014[Gajda, K., Zarychta, B., Daszkiewicz, Z., Domański, A. A. & Ejsmont, K. (2014). Acta Cryst. C70, 575-579.] (AZUKAI01)], has a planar arrangement in the trans isomers. However, if the ortho positions are occupied by bulky iodine substituents, such as in diethyl 4,4′-diazenediylbis(3,5-di­iodo­benzoate), the mol­ecule is non-planar in the trans form (TETROD; Kerckhoffs et al., 2022[Kerckhoffs, A., Christensen, K. E. & Langton, M. J. (2022). Chem. Sci. 13, 11551-11559.]). In addition, some non-halogenated and halogenated azo­benzenes, both cis and trans isomers, have been studied [Hampson & Robertson,1941[Hampson, G. C. & Robertson, J. M. (1941). J. Chem. Soc. pp. 409-413.] (AZBENC); Mostad et al., 1971[Mostad, A. & Rømming, C. (1971). Acta Chem. Scand. 25, 3561-3568.] (AZBENC01); De Lange et al., 1939[De Lange, J. J., Robertson, J. M. & Woodward, I. (1939). Proc. Roy. Soc. A171, 398-410.] (AZOBEN); Chinnakali et al., 1993[Chinnakali, K., Fun, H.-K., Shawkataly, O. B. & Teoh, S.-G. (1993). Acta Cryst. C49, 615-616.] (WACHAJ); Harada et al., 1997[Harada, J., Ogawa, K. & Tomoda, S. (1997). Acta Cryst. B53, 662-672.] (AZOBEN04–06; Bushuyev et al., 2016[Bushuyev, O. S., Tomberg, A., Vinden, J. R., Moitessier, N., Barrett, C. J. & Friščić, T. (2016). Chem. Commun. 52, 2103-2106.] (SUWKIG); Saccone et al., 2014[Saccone, M., Terraneo, G., Pilati, T., Cavallo, G., Priimagi, A., Metrangolo, P. & Resnati, G. (2014). Acta Cryst. B70, 149-156.] (PINLUV); Aggarwal et al., 2020[Aggarwal, K., Kuka, T. P., Banik, M., Medellin, B. P., Ngo, C. Q., Xie, D., Fernandes, Y., Dangerfield, T. L., Ye, E., Bouley, B., Johnson, K. A., Zhang, Y. J., Eberhart, J. K. & Que, E. L. (2020). J. Am. Chem. Soc. 142, 14522-14531.] (TUXNEI and TUXNAE)].

5. Synthesis and crystallization

The synthesis of mol­ecules I–III is shown in the reaction scheme, and follows a slight modification of the procedure described previously (Appiah et al., 2017[Appiah, C., Woltersdorf, G. & Binder, W. H. (2017). Polym. Chem. 8, 2752-2763.]). Starting materials were purchased from Ambeed Inc. and Sigma-Aldrich and used without further purification. To obtain 4-amino-3,5-di­fluoro­benzo­nitrile (I), 4-bromo-2,6-di­fluoro­aniline (50.0 g, 240 mmol, 1 eq.) and CuCN (64.5 g, 720 mmol, 3 eq.) were suspended in di­methyl­formamide (DMF, 500 mL) and refluxed for 24 h. The mixture was cooled to room temperature and NH4OH (2 L, 18%) was added, and the resulting solution was filtered. The mixture (filtrate) was extracted with EtOAc (4 × 750 mL) and the organic phase was washed with NH4OH 18%, de-ionized water, brine, dried with Na2SO4, and filtered. The residue was purified through a silica gel plug with CH2Cl2/n-hexane 2:1, to yield a dark-brown solid (15.7 g, 102 mmol, 42% yield).

[Scheme 2]

The synthesis of 4-amino-3,5-di­fluoro­benzoic acid was conducted by treating 4-amino-3,5-di­fluoro­benzo­nitrile (14.91 g, 96.7 mmol, 1 eq.) with sodium hydroxide (NaOH 1 M, 480 mL). The resulting solution was heated to reflux for 24 h. The reaction was then cooled to room temperature and HCl conc. (60 mL) was added to the reaction mixture dropwise until the reaction turned acidic pH ∼1; the product precipitated as a hydro­chloride salt. The salt was then dissolved in ethyl acetate, dried over MgSO4, filtered, and concentrated under vacuum to obtain 4-amino-3,5-di­fluoro­benzoic acid (14.9 g, 81.4 mmol, 84.2%).

To obtain 4-amino-3,5-di­fluoro­benzoate (II), 4-amino-3,5-di­fluoro­benzoic acid (14.9 g, 96.7 mmol) was dissolved in ethanol (300 mL) and H2SO4 (6 mL) and refluxed for 10 h. The reaction was neutralized using a saturated solution of sodium bicarbonate, followed by extraction with di­chloro­methane (DCM, 4 × 300 mL). The organic phase was dried using sodium sulfate (Na2SO4), filtered, and concentrated under reduced pressure, yielding the inter­mediate product (14.99 g, 75 mmol, 77% yield).

To obtain diethyl-4,4′-(2,2′,6,6′-tetra­fluoro)­azo­benzene di­carboxyl­ate (III), 4-amino-3,5-di­fluoro­benzoate (12.0 g, 60 mmol, 1 eq.) and sodium iodide (NaI) (18.4 g, 120 mmol, 2 eq.) in Et2O (400 mL) were added into a 1 L flask. To the reaction mixture, tert-butyl hypochlorite (t-BuOCl, 14 mL, 4 eq.) was added and the resulting mixture was stirred for 12 h at rt. Thereafter, a freshly prepared solution of 1 M Na2SO3 (1200 mL) was added, and the mixture was mixed thoroughly. The resulting mixture was washed by DCM (1 × 600 mL) and the organic layer was collected and washed with RO water (3 × 1L) and brine (3 x 750 mL), dried with Na2SO4 (anhydrous), filtered, purified through a silica gel plug and evaporated under reduced pressure. The crude product was rinsed with a small amount of EtOAc to yield a reddish precipitate (4.9 g, 12.4 mmol, 21% yield).

Crystallization of all compounds for diffraction studies was performed using the slow evaporation method. All solutions were prepared by dissolving compounds I–III in DCM (2 mL) and sonicating them for 10 min. Then they were capped with cotton plugs and left in the hood for 4 days. Thereafter transparent plate-like crystals of I and II, and dark-red needle-like crystals of III were obtained.

6. Refinement

Crystal data, data collection and structure refinement details for compounds I, II, and III are summarized in Table 4[link]. The acidic N–H protons in I and II were localized from the residual electron-density map and refined freely. All other H atoms were positioned geometrically (C—H = 0.95–0.99 Å) and refined as riding with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(C-meth­yl).

Table 4
Experimental details

  I II III
Crystal data
Chemical formula C7H4F2N2 C9H9F2NO2 C18H14F4N2O4
Mr 154.12 201.17 398.31
Crystal system, space group Monoclinic, P21/n Orthorhombic, Pbcn Triclinic, P[\overline{1}]
Temperature (K) 100 100 100
a, b, c (Å) 3.7283 (4), 10.5275 (12), 16.9073 (19) 14.877 (3), 8.9995 (18), 13.635 (3) 4.6106 (17), 8.839 (3), 10.969 (4)
α, β, γ (°) 90, 94.604 (2), 90 90, 90, 90 99.330 (8), 99.431 (8), 96.442 (7)
V (Å3) 661.46 (13) 1825.6 (6) 430.7 (3)
Z 4 8 1
Radiation type Mo Kα Mo Kα Mo Kα
μ (mm−1) 0.14 0.13 0.14
Crystal size (mm) 0.36 × 0.22 × 0.12 0.21 × 0.13 × 0.11 0.57 × 0.13 × 0.1
 
Data collection
Diffractometer Bruker APEXII CCD Bruker APEXII CCD Bruker SMART APEXII
Absorption correction Multi-scan (SADABS; Krause et al., 2015[Krause, L., Herbst-Irmer, R., Sheldrick, G. M. & Stalke, D. (2015). J. Appl. Cryst. 48, 3-10.]) Multi-scan (SADABS; Krause et al., 2015[Krause, L., Herbst-Irmer, R., Sheldrick, G. M. & Stalke, D. (2015). J. Appl. Cryst. 48, 3-10.]) Multi-scan (SADABS; Krause et al., 2015[Krause, L., Herbst-Irmer, R., Sheldrick, G. M. & Stalke, D. (2015). J. Appl. Cryst. 48, 3-10.])
Tmin, Tmax 0.661, 0.746 0.973, 0.986 0.926, 0.986
No. of measured, independent and observed [I > 2σ(I)] reflections 11242, 2140, 1775 29363, 1665, 1265 3269, 1913, 1414
Rint 0.029 0.114 0.023
(sin θ/λ)max (Å−1) 0.738 0.600 0.649
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.047, 0.130, 1.09 0.060, 0.131, 1.21 0.047, 0.150, 1.01
No. of reflections 2140 1665 1913
No. of parameters 108 136 132
H-atom treatment H atoms treated by a mixture of independent and constrained refinement H atoms treated by a mixture of independent and constrained refinement H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3) 0.46, −0.23 0.20, −0.27 0.28, −0.29
Computer programs: APEX2 and SAINT-Plus (Bruker, 2019[Bruker (2019). APEX2 and SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXT (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXS (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), SHELXL (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]) and OLEX2 (Dolomanov et al., 2009[Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339-341.]).

Supporting information

CCDC references: 2370064; 2370063; 2370062

Crystal structure: contains datablocks I, II, III. DOI: https://doi.org/10.1107/S2056989024006819/jq2034sup1.cif

Structure factors: contains datablock III. DOI: https://doi.org/10.1107/S2056989024006819/jq2034IIIsup2.hkl

Structure factors: contains datablock II. DOI: https://doi.org/10.1107/S2056989024006819/jq2034IIsup3.hkl

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989024006819/jq2034Isup4.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989024006819/jq2034Isup5.cml

Supporting information file. DOI: https://doi.org/10.1107/S2056989024006819/jq2034IIsup6.cml

Supporting information file. DOI: https://doi.org/10.1107/S2056989024006819/jq2034IIIsup7.cml

checkCIF report


Computing details top

4-Amino-3,5-difluorobenzonitrile (I) top
Crystal data top
C7H4F2N2F(000) = 312
Mr = 154.12Dx = 1.548 Mg m−3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 3.7283 (4) ÅCell parameters from 4913 reflections
b = 10.5275 (12) Åθ = 2.3–31.2°
c = 16.9073 (19) ŵ = 0.14 mm−1
β = 94.604 (2)°T = 100 K
V = 661.46 (13) Å3Block, clear colourless
Z = 40.36 × 0.22 × 0.12 mm
Data collection top
Bruker APEXII CCD
diffractometer		2140 independent reflections
Radiation source: sealed X-ray tube, EIGENMANN GmbH1775 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.029
Detector resolution: 7.9 pixels mm-1θmax = 31.7°, θmin = 2.3°
φ and ω scansh = −5→5
Absorption correction: multi-scan
(SADABS; Krause et al., 2015)		k = −14→15
Tmin = 0.661, Tmax = 0.746l = −23→24
11242 measured reflections
Refinement top
Refinement on F2Primary atom site location: dual
Least-squares matrix: fullHydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.047H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.130 w = 1/[σ2(Fo2) + (0.0659P)2 + 0.2291P]
where P = (Fo2 + 2Fc2)/3
S = 1.09(Δ/σ)max < 0.001
2140 reflectionsΔρmax = 0.46 e Å−3
108 parametersΔρmin = −0.23 e Å−3
0 restraints
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
F10.8337 (2)0.47654 (7)0.39927 (5)0.0311 (2)
F20.3651 (2)0.80481 (8)0.23493 (4)0.0314 (2)
N20.6762 (3)0.56770 (11)0.24999 (7)0.0276 (3)
N10.2518 (4)0.89360 (14)0.57454 (7)0.0379 (3)
C60.4379 (3)0.75726 (11)0.30925 (7)0.0206 (2)
C40.6741 (3)0.59252 (11)0.39189 (7)0.0207 (2)
C50.6003 (3)0.63732 (11)0.31445 (6)0.0194 (2)
C20.4317 (3)0.77685 (12)0.44923 (7)0.0217 (2)
C70.3518 (3)0.82791 (11)0.37357 (7)0.0215 (2)
H70.2414460.9089310.3667270.026*
C30.5960 (3)0.65780 (12)0.45866 (7)0.0224 (2)
H30.6521630.6229770.5099990.027*
C10.3337 (4)0.84385 (13)0.51849 (8)0.0267 (3)
H2A0.671 (6)0.602 (2)0.2066 (14)0.047 (6)*
H2B0.814 (5)0.500 (2)0.2560 (12)0.036 (5)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
F10.0404 (5)0.0221 (4)0.0309 (4)0.0075 (3)0.0035 (3)0.0050 (3)
F20.0466 (5)0.0272 (4)0.0199 (4)0.0021 (3)−0.0008 (3)0.0057 (3)
N20.0384 (6)0.0244 (5)0.0208 (5)0.0015 (5)0.0065 (4)−0.0020 (4)
N10.0425 (7)0.0426 (7)0.0299 (6)−0.0056 (6)0.0099 (5)−0.0095 (5)
C60.0227 (5)0.0204 (5)0.0185 (5)−0.0036 (4)0.0008 (4)0.0032 (4)
C40.0214 (5)0.0173 (5)0.0236 (5)−0.0008 (4)0.0025 (4)0.0022 (4)
C50.0190 (5)0.0192 (5)0.0202 (5)−0.0045 (4)0.0034 (4)−0.0001 (4)
C20.0201 (5)0.0240 (6)0.0213 (5)−0.0049 (4)0.0040 (4)−0.0031 (4)
C70.0208 (5)0.0185 (5)0.0252 (5)−0.0011 (4)0.0023 (4)−0.0008 (4)
C30.0231 (5)0.0256 (6)0.0187 (5)−0.0037 (4)0.0017 (4)0.0029 (4)
C10.0267 (6)0.0286 (6)0.0253 (6)−0.0056 (5)0.0046 (4)−0.0034 (5)
Geometric parameters (Å, º) top
F1—C41.3596 (14)C4—C51.3982 (16)
F2—C61.3596 (13)C4—C31.3726 (16)
N2—C51.3617 (15)C2—C71.3975 (17)
N2—H2A0.82 (2)C2—C31.3984 (17)
N2—H2B0.88 (2)C2—C11.4390 (17)
N1—C11.1455 (18)C7—H70.9500
C6—C51.4000 (16)C3—H30.9500
C6—C71.3765 (16)
C5—N2—H2A119.3 (15)C4—C5—C6114.49 (10)
C5—N2—H2B120.1 (13)C7—C2—C3120.55 (11)
H2A—N2—H2B115.7 (19)C7—C2—C1120.46 (11)
F2—C6—C5116.31 (10)C3—C2—C1118.95 (11)
F2—C6—C7119.29 (11)C6—C7—C2117.98 (11)
C7—C6—C5124.39 (11)C6—C7—H7121.0
F1—C4—C5116.14 (10)C2—C7—H7121.0
F1—C4—C3119.63 (10)C4—C3—C2118.35 (10)
C3—C4—C5124.23 (11)C4—C3—H3120.8
N2—C5—C6123.49 (11)C2—C3—H3120.8
N2—C5—C4122.01 (11)N1—C1—C2177.81 (15)
F1—C4—C5—N21.45 (17)C7—C6—C5—N2178.51 (12)
F1—C4—C5—C6−179.65 (10)C7—C6—C5—C4−0.36 (17)
F1—C4—C3—C2−179.98 (10)C7—C2—C3—C4−0.41 (17)
F2—C6—C5—N2−1.79 (17)C3—C4—C5—N2−178.59 (12)
F2—C6—C5—C4179.34 (10)C3—C4—C5—C60.31 (17)
F2—C6—C7—C2−179.65 (10)C3—C2—C7—C60.36 (17)
C5—C6—C7—C20.04 (18)C1—C2—C7—C6−177.28 (11)
C5—C4—C3—C20.06 (18)C1—C2—C3—C4177.26 (11)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2A···N1i0.82 (2)2.28 (2)3.0297 (17)153 (2)
N2—H2B···F2ii0.88 (2)2.38 (2)3.2526 (15)173.9 (19)
Symmetry codes: (i) x+1/2, −y+3/2, z−1/2; (ii) −x+3/2, y−1/2, −z+1/2.
Ethyl 4-amino-3,5-difluorobenzoate (II) top
Crystal data top
C9H9F2NO2Dx = 1.464 Mg m−3
Mr = 201.17Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, PbcnCell parameters from 3255 reflections
a = 14.877 (3) Åθ = 2.7–23.4°
b = 8.9995 (18) ŵ = 0.13 mm−1
c = 13.635 (3) ÅT = 100 K
V = 1825.6 (6) Å3Block, clear colourless
Z = 80.21 × 0.13 × 0.11 mm
F(000) = 832
Data collection top
Bruker APEXII CCD
diffractometer		1665 independent reflections
Radiation source: sealed X-ray tube, EIGENMANN GmbH1265 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.114
Detector resolution: 7.9 pixels mm-1θmax = 25.3°, θmin = 2.7°
ω and φ scansh = −17→17
Absorption correction: multi-scan
(SADABS; Krause et al., 2015)		k = −10→10
Tmin = 0.973, Tmax = 0.986l = −16→16
29363 measured reflections
Refinement top
Refinement on F20 restraints
Least-squares matrix: fullHydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.060H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.131 w = 1/[σ2(Fo2) + 3.0535P]
where P = (Fo2 + 2Fc2)/3
S = 1.21(Δ/σ)max < 0.001
1665 reflectionsΔρmax = 0.20 e Å−3
136 parametersΔρmin = −0.26 e Å−3
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
F10.54938 (12)0.31169 (18)0.35054 (15)0.0396 (5)
F20.26856 (12)0.4861 (2)0.45376 (15)0.0403 (5)
O20.58679 (14)0.8516 (2)0.34897 (17)0.0327 (6)
O10.45423 (15)0.9500 (2)0.39457 (17)0.0365 (6)
N10.3767 (2)0.2502 (3)0.4064 (2)0.0374 (8)
C60.35426 (19)0.5153 (3)0.4228 (2)0.0284 (7)
C10.4077 (2)0.3925 (3)0.4014 (2)0.0275 (7)
C40.4707 (2)0.6876 (3)0.3866 (2)0.0253 (7)
C20.4942 (2)0.4276 (3)0.3721 (2)0.0274 (7)
C70.5012 (2)0.8429 (3)0.3781 (2)0.0278 (7)
C30.5275 (2)0.5693 (3)0.3645 (2)0.0279 (7)
H30.5877970.5863260.3447060.033*
C50.3829 (2)0.6589 (3)0.4160 (2)0.0279 (7)
H50.3433510.7384840.4312790.034*
C80.6241 (2)1.0007 (3)0.3392 (3)0.0350 (8)
H8A0.6252031.0513560.4036140.042*
H8B0.5874711.0605640.2932610.042*
C90.7174 (2)0.9825 (4)0.3006 (3)0.0468 (10)
H9A0.7154600.9289300.2380050.070*
H9B0.7534480.9260450.3477970.070*
H9C0.7445411.0805390.2904980.070*
H1A0.414 (2)0.179 (4)0.399 (3)0.043 (11)*
H1B0.326 (3)0.237 (4)0.435 (3)0.045 (12)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
F10.0434 (11)0.0199 (9)0.0556 (13)0.0081 (8)0.0050 (10)−0.0026 (9)
F20.0312 (10)0.0295 (10)0.0603 (13)−0.0029 (8)0.0050 (9)0.0013 (9)
O20.0363 (13)0.0176 (10)0.0442 (14)−0.0032 (9)0.0032 (10)0.0027 (10)
O10.0390 (13)0.0195 (11)0.0512 (16)0.0044 (10)−0.0015 (11)−0.0011 (10)
N10.0405 (19)0.0169 (14)0.055 (2)−0.0022 (14)0.0048 (16)0.0004 (13)
C60.0250 (16)0.0267 (17)0.0335 (18)−0.0001 (13)−0.0012 (14)0.0017 (14)
C10.0352 (18)0.0190 (15)0.0284 (18)−0.0012 (13)−0.0053 (14)0.0001 (13)
C40.0285 (17)0.0198 (15)0.0276 (17)−0.0003 (12)−0.0048 (13)0.0021 (12)
C20.0293 (17)0.0194 (15)0.0336 (18)0.0084 (13)−0.0008 (14)−0.0018 (13)
C70.0329 (18)0.0240 (16)0.0264 (17)0.0015 (14)−0.0049 (14)−0.0017 (14)
C30.0302 (18)0.0236 (16)0.0299 (18)0.0021 (13)0.0002 (13)−0.0011 (13)
C50.0326 (18)0.0191 (15)0.0321 (18)0.0082 (13)−0.0054 (14)−0.0014 (13)
C80.044 (2)0.0182 (15)0.043 (2)−0.0047 (15)−0.0021 (16)0.0007 (14)
C90.045 (2)0.035 (2)0.060 (3)−0.0108 (17)0.0055 (19)0.0014 (18)
Geometric parameters (Å, º) top
F1—C21.360 (3)C4—C31.392 (4)
F2—C61.368 (3)C4—C51.390 (4)
O2—C71.336 (4)C2—C31.372 (4)
O2—C81.458 (4)C3—H30.9500
O1—C71.212 (4)C5—H50.9500
N1—C11.363 (4)C8—H8A0.9900
N1—H1A0.86 (4)C8—H8B0.9900
N1—H1B0.86 (4)C8—C91.493 (5)
C6—C11.392 (4)C9—H9A0.9800
C6—C51.365 (4)C9—H9B0.9800
C1—C21.385 (4)C9—H9C0.9800
C4—C71.474 (4)
C7—O2—C8116.4 (2)C4—C3—H3120.8
C1—N1—H1A118 (2)C2—C3—C4118.4 (3)
C1—N1—H1B117 (2)C2—C3—H3120.8
H1A—N1—H1B122 (3)C6—C5—C4119.3 (3)
F2—C6—C1116.4 (3)C6—C5—H5120.4
C5—C6—F2119.6 (3)C4—C5—H5120.4
C5—C6—C1124.0 (3)O2—C8—H8A110.4
N1—C1—C6122.9 (3)O2—C8—H8B110.4
N1—C1—C2122.9 (3)O2—C8—C9106.6 (3)
C2—C1—C6114.2 (3)H8A—C8—H8B108.6
C3—C4—C7121.4 (3)C9—C8—H8A110.4
C5—C4—C7119.2 (3)C9—C8—H8B110.4
C5—C4—C3119.4 (3)C8—C9—H9A109.5
F1—C2—C1116.7 (3)C8—C9—H9B109.5
F1—C2—C3118.7 (3)C8—C9—H9C109.5
C3—C2—C1124.7 (3)H9A—C9—H9B109.5
O2—C7—C4111.9 (3)H9A—C9—H9C109.5
O1—C7—O2123.9 (3)H9B—C9—H9C109.5
O1—C7—C4124.2 (3)
F1—C2—C3—C4179.9 (3)C7—C4—C5—C6179.2 (3)
F2—C6—C1—N12.6 (5)C3—C4—C7—O2−0.8 (4)
F2—C6—C1—C2−178.9 (3)C3—C4—C7—O1178.6 (3)
F2—C6—C5—C4178.6 (3)C3—C4—C5—C60.1 (5)
N1—C1—C2—F1−1.7 (5)C5—C6—C1—N1−178.3 (3)
N1—C1—C2—C3178.9 (3)C5—C6—C1—C20.2 (5)
C6—C1—C2—F1179.8 (3)C5—C4—C7—O2−179.9 (3)
C6—C1—C2—C30.4 (5)C5—C4—C7—O1−0.5 (5)
C1—C6—C5—C4−0.4 (5)C5—C4—C3—C20.4 (5)
C1—C2—C3—C4−0.7 (5)C8—O2—C7—O11.3 (4)
C7—O2—C8—C9−176.7 (3)C8—O2—C7—C4−179.3 (3)
C7—C4—C3—C2−178.7 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···O1i0.85 (3)2.15 (4)2.942 (3)155 (3)
C8—H8B···F1ii0.992.463.015 (3)115
Symmetry codes: (i) x, y−1, z; (ii) x, y+1, z.
Diethyl 4,4'-(diazene-1,2-diyl)bis(3,5-difluorobenzoate) (III) top
Crystal data top
C18H14F4N2O4Z = 1
Mr = 398.31F(000) = 204
Triclinic, P1Dx = 1.536 Mg m−3
a = 4.6106 (17) ÅMo Kα radiation, λ = 0.71073 Å
b = 8.839 (3) ÅCell parameters from 1029 reflections
c = 10.969 (4) Åθ = 2.4–27.2°
α = 99.330 (8)°µ = 0.14 mm−1
β = 99.431 (8)°T = 100 K
γ = 96.442 (7)°Needle, dark brown
V = 430.7 (3) Å30.57 × 0.13 × 0.1 mm
Data collection top
Bruker SMART APEXII
diffractometer		1913 independent reflections
Radiation source: sealed X-ray tube, EIGENMANN GmbH1414 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.023
Detector resolution: 7.9 pixels mm-1θmax = 27.5°, θmin = 1.9°
ω and φ scansh = −5→5
Absorption correction: multi-scan
(SADABS; Krause et al., 2015)		k = −11→11
Tmin = 0.926, Tmax = 0.986l = −12→14
3269 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullHydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.047H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.150 w = 1/[σ2(Fo2) + (0.0945P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.01(Δ/σ)max < 0.001
1913 reflectionsΔρmax = 0.28 e Å−3
132 parametersΔρmin = −0.29 e Å−3
0 restraints
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
F10.3292 (3)0.83917 (13)0.96263 (11)0.0332 (3)
F20.2359 (3)0.43669 (13)1.19462 (11)0.0352 (3)
O1−0.2904 (3)0.84303 (16)1.39751 (13)0.0308 (4)
O2−0.1813 (3)1.04412 (15)1.30209 (12)0.0261 (3)
N10.4466 (3)0.55792 (18)0.98505 (15)0.0256 (4)
C10.2996 (4)0.6346 (2)1.07526 (16)0.0206 (4)
C20.2364 (4)0.7829 (2)1.05820 (17)0.0235 (4)
C30.0879 (4)0.8714 (2)1.13506 (17)0.0229 (4)
C4−0.0091 (4)0.8109 (2)1.23300 (17)0.0212 (4)
C50.0423 (4)0.6636 (2)1.25239 (17)0.0232 (4)
H5−0.0280300.6216981.3183220.028*
C60.1961 (4)0.5799 (2)1.17490 (17)0.0223 (4)
C7−0.1761 (4)0.8990 (2)1.32022 (17)0.0223 (4)
C8−0.3390 (4)1.1407 (2)1.38246 (19)0.0277 (4)
H8A−0.2961231.1217911.4696980.033*
H8B−0.5560111.1162991.3512340.033*
C9−0.2333 (5)1.3059 (2)1.3787 (2)0.0347 (5)
H9A−0.2745441.3227541.2918240.052*
H9B−0.0189881.3290461.4111530.052*
H9C−0.3370131.3740391.4307820.052*
H30.060 (4)0.969 (2)1.117 (2)0.027 (5)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
F10.0480 (7)0.0331 (6)0.0279 (7)0.0169 (5)0.0208 (5)0.0111 (5)
F20.0462 (7)0.0308 (6)0.0397 (7)0.0187 (5)0.0220 (6)0.0152 (5)
O10.0320 (7)0.0348 (8)0.0301 (8)0.0085 (6)0.0151 (6)0.0072 (6)
O20.0271 (7)0.0277 (7)0.0256 (7)0.0089 (5)0.0108 (5)0.0016 (6)
N10.0250 (8)0.0295 (8)0.0239 (8)0.0092 (6)0.0078 (6)0.0028 (7)
C10.0174 (8)0.0253 (9)0.0183 (9)0.0055 (6)0.0029 (7)0.0005 (7)
C20.0243 (9)0.0293 (10)0.0180 (9)0.0056 (7)0.0050 (7)0.0056 (7)
C30.0246 (9)0.0241 (9)0.0210 (9)0.0075 (7)0.0039 (7)0.0047 (7)
C40.0155 (8)0.0270 (9)0.0190 (9)0.0031 (6)0.0016 (7)−0.0005 (7)
C50.0198 (8)0.0297 (10)0.0201 (9)0.0036 (7)0.0038 (7)0.0042 (7)
C60.0214 (8)0.0224 (9)0.0233 (10)0.0061 (7)0.0018 (7)0.0050 (7)
C70.0186 (8)0.0279 (9)0.0185 (9)0.0036 (7)0.0010 (7)0.0010 (7)
C80.0258 (9)0.0299 (10)0.0283 (10)0.0093 (7)0.0117 (8)−0.0026 (8)
C90.0398 (11)0.0325 (11)0.0329 (11)0.0114 (9)0.0109 (9)0.0009 (9)
Geometric parameters (Å, º) top
F1—C21.341 (2)C3—H30.94 (2)
F2—C61.345 (2)C4—C51.392 (3)
O1—C71.211 (2)C4—C71.500 (2)
O2—C71.332 (2)C5—H50.9500
O2—C81.463 (2)C5—C61.373 (3)
N1—N1i1.252 (3)C8—H8A0.9900
N1—C11.415 (2)C8—H8B0.9900
C1—C21.409 (3)C8—C91.496 (3)
C1—C61.395 (3)C9—H9A0.9800
C2—C31.373 (3)C9—H9B0.9800
C3—C41.389 (3)C9—H9C0.9800
C7—O2—C8116.47 (14)F2—C6—C5117.43 (16)
N1i—N1—C1114.4 (2)C5—C6—C1122.86 (17)
C2—C1—N1115.52 (16)O1—C7—O2124.89 (17)
C6—C1—N1128.64 (16)O1—C7—C4123.19 (18)
C6—C1—C2115.76 (16)O2—C7—C4111.91 (16)
F1—C2—C1117.69 (16)O2—C8—H8A110.3
F1—C2—C3119.19 (16)O2—C8—H8B110.3
C3—C2—C1123.11 (17)O2—C8—C9107.28 (15)
C2—C3—C4118.52 (17)H8A—C8—H8B108.5
C2—C3—H3116.6 (13)C9—C8—H8A110.3
C4—C3—H3124.9 (13)C9—C8—H8B110.3
C3—C4—C5120.65 (17)C8—C9—H9A109.5
C3—C4—C7121.92 (17)C8—C9—H9B109.5
C5—C4—C7117.42 (17)C8—C9—H9C109.5
C4—C5—H5120.5H9A—C9—H9B109.5
C6—C5—C4119.07 (17)H9A—C9—H9C109.5
C6—C5—H5120.5H9B—C9—H9C109.5
F2—C6—C1119.66 (16)
F1—C2—C3—C4179.45 (15)C3—C4—C7—O1171.84 (16)
N1i—N1—C1—C2166.37 (19)C3—C4—C7—O2−8.3 (2)
N1i—N1—C1—C6−17.2 (3)C4—C5—C6—F2−178.54 (14)
N1—C1—C2—F1−2.4 (2)C4—C5—C6—C1−1.2 (3)
N1—C1—C2—C3178.22 (15)C5—C4—C7—O1−7.2 (3)
N1—C1—C6—F20.7 (3)C5—C4—C7—O2172.65 (14)
N1—C1—C6—C5−176.52 (16)C6—C1—C2—F1−179.32 (14)
C1—C2—C3—C4−1.1 (3)C6—C1—C2—C31.3 (3)
C2—C1—C6—F2177.21 (15)C7—O2—C8—C9161.06 (16)
C2—C1—C6—C5−0.1 (3)C7—C4—C5—C6−179.59 (14)
C2—C3—C4—C5−0.2 (3)C8—O2—C7—O1−0.2 (3)
C2—C3—C4—C7−179.22 (14)C8—O2—C7—C4179.99 (13)
C3—C4—C5—C61.4 (3)
Symmetry code: (i) −x+1, −y+1, −z+2.
Selected bond lengths (Å) in molecules of I–III top
Bond/CompoundIIIIII
11.373 (2)1.372 (4)1.373 (3)
21.377 (2)1.365 (4)1.373 (3)
31.360 (1)1.360 (3)1.345 (2)
41.360 (1)1.368 (3)1.341 (2)
5––1.252 (3)
 

Acknowledgements

The authors are grateful to Dr Averkiev for help with the creation of the histogram.

Funding information

Funding for this research was provided by: NSF (PREM) (grant No. DMR-2122108) and BioPACIFIC Materials Innovation Platform of the National Science Foundation under award No. DMR-1933487.

References

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ISSN: 2056-9890
Volume 80| Part 8| August 2024| Pages 867-872
https://doi.org/10.1107/S2056989024006819
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