A Paddle-Wheel Motif versus an Extended Network: Two Crystalline Forms of 2,4-Bis(Phenylamino)Nitrobenzene

Abstract

2,4-Difluoronitrobenzene is reacted with either one or two amines selected from aniline, ammonia, butylamine and benzylamine. All products are characterised spectroscopically and by single-crystal structure determinations. When formed as a minor component alongside 4-dimethylamino-2-(phenylamino)nitrobenzene, 2,4-bis(phenylamino)nitrobenzene crystallises as a hydrogen-bonded hexamer, or paddle-wheel motif, encompassing one-dimensional channels, but as a dense framework when pure. 2,4-Bis(butylamino)nitrobenzene crystallises with the same hexamer motif but with offset sheets.

An Organic Zeolite With 10 Å Diameter Pores Assembles From a Soluble and Flexible Building Block by Non‐Covalent Interactions

“…The N4À H4 moiety forms an asymmetric, bifurcated hydrogen bond to O1 (H···O = 2.18 Å) and O2 (H···O = 2.52 Å) in an adjacent molecule to generate a hexameric ring ( Figure 6) with an R 6 6 (78) graph-set motif. This resembles the hydrogen-bonded hexamer in 2,4-bis(butylamino) nitrobenzene 2 [1] shown in Figure 1 above with the important difference that the ortho N-butyl chain in compound 11 is oriented towards the centre of the hexamer rather than pointing away from it. The symmetry of the hexameric assembly is � 3 about the point (1, 0, 1 = 2 ) for the asymmetric molecule and its five clones.…”

“…UV spectra were recorded using a Perkin-Elmer Lambda 25 UV-VIS spectrometer with EtOH as the solvent. 1 H and 13 C NMR spectra were recorded at 600 MHz and 150 MHz, respectively, using a Varian 400 spectrometer. Chemical shifts, δ are given in ppm relative to the residual solvent and coupling constants, J are given in Hz.…”

“…Dichloromethane elutes by-products then the title compound (115 mg, 14 %) as a yellow solid, m.p. 176-178°C (from ether/light petroleum ether 40-60); 1…”

“…Recently we reported the crystal structures of cyclic hexameric motifs formed from 2,4-bis(phenylamino) nitrobenzene 1 or 2,4bis(butylamino)nitrobenzene 2 in which adjacent molecules are linked by NÀ HÀ O hydrogen bonds ( Figure 1). [1][2] The hexamers formed from 2,4-bis(phenylamino)nitrobenzene 1 are stacked on top of each other so that large channels arise but the hexamers formed from 2,4-bis(butylamino)nitrobenzene 2 have a staggered stacking arrangement so that channels do not occur in the crystal. The open framework formed from compound 1 is an example of a nanoporous material comprised of discrete organic molecules between which there are only weak non-covalent interactions.…”

The Consistent Hexameric Paddle-Wheel Crystallisation Motif of a Family of 2,4-Bis(n-Alkylamino)Nitrobenzenes: Alkyl = Pentyl, Hexyl, Heptyl and Octyl

“…2). 6 The hexamers formed from 2,4-bis(butylamino)nitrobenzene have a staggered stacking arrangement so that channels do not occur in the crystal but the hexamers formed from 2,4-bis(phenylamino) nitrobenzene are stacked on top of each other so that large channels arise. This work might be related to solution studies by Whitesides and Reinhoudt on melamine-cyanuric/ barbituric acid hexamers, although the building blocks here are different and there are fewer hydrogen bonds to support…”