A library of dimeric and trimeric phthalonitriles linked by a single aromatic ring: comparative structural and DFT investigations

Abstract

A library of five phthalonitriles, dimeric or trimeric, all connected by an aromatic spacer (catechol, resorcinol, hydroquinone, phloroglucinol and catechol with two tert-butyl moieties), was selected to be comparatively studied from a structural point of view. Hirshfeld surface analysis and DFT calculations were performed as well.

Bisphthalonitrile with a Disulfide-Based Linker and its Dimethylene Analogue: Comparative Structural Insights

“…The interplanar distances between two phthalonitrile aromatic rings are 3.35 Å (pink colored in Figure 5c) and 3.30 Å (blue colored in Figure 5c). The C"N bond distances of the bisphthalonitrile range from 1.137(5) to 1.138(6) Å, and these values are in good agreement with those reported in the literature [19][20][21][22][23][24][25][26][27][28] except C1-N1 bond distance is 1.129(50) Å shorter than expected. In addition, the data are similar to those observed for unsubstituted phthalonitrile [29], evidencing that the molecular intrinsic structure of the phthalonitrile ring is not affected by the presence of the substituents.…”

“…Slipped aromatic π-π interactions are observed in the crystal structure of 1 as the main stacking interactions that lead to parallel-displaced configurations in the crystals. This predominant behaviour is common for bisphthalonitriles previously reported and linked by different aliphatic spacers in which only the grafting atom varies (O/S/SO2) [26], but unlike bisphthalonitriles with aromatic spacers (catechol, resorcinol, hydroquinone, phloroglucinol) [21]. From all of these reports, the flexibility of the spacer appears to be more decisive than its length or the nature of the grafting atoms.…”

“…The intermolecular stacking of bisphthalonitrile 1 is promoted by the π-π interactions between phthalonitrile aromatic rings, the centroid-centroid distance being (dc-c) 5.305(3) Å between two phthalonitrile aromatic units, a value longer than for related bisphthalonitriles [21][22][23][24][25][26]. In particular, compared to bisphthalonitriles with spacer having oxygen grafting atom, it appears that this unusually long centroid-centroid distance is more due to the bended geometry of the disulfite function that to the number of atoms in the spacer or to its aliphatic or aromatic character.…”

“…Strong attractive interactions between π systems are one of the principal non-covalent forces controlling such varied phenomena, which stabilize the packing of aromatic molecules in crystal. The parallel-displaced configuration is the one of most well-known favourable configurations [21][22][23][24][25]. Slipped aromatic π-π interactions are observed in the crystal structure of 1 as the main stacking interactions that lead to parallel-displaced configurations in the crystals.…”