, Volume 41, Issue 11, pp 1649-1662
Date: 25 Jun 2011

Structural Systematics of the Anhydrous 1:1 Proton-Transfer Compounds of 3,5-Dinitrosalicylic Acid with Aniline and Monosubstituted Anilines

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Abstract

The crystal structures of the proton-transfer compounds of 3,5-dinitrosalicylic acid (DNSA) with a series of aniline-type Lewis bases (aniline, 2-hydroxyaniline, 2-methoxyaniline, 3-methoxyaniline, 4-fluoroaniline, 4-chloroaniline and 2-aminoaniline) have been determined and their hydrogen-bonding systems analysed. All are anhydrous 1:1 salts: [(C6H8N)+(C7H3N2O7)] (1), [(C6H8NO)+(C7H3N2O7)] (2), [(C7H10NO)+(C7H3N2O7)] (3), [(C7H10NO)+(C7H3N2O7)] (4), [(C6H7FN)+(C7H3N2O7)] (5), [(C6H7ClN)+(C7H3N2O7)] (6), and [(C6H9N2)+(C7H3N2O7)] (7), respectively. Crystals of 1 and 6 are triclinic, space group P-1 while the remainder are monoclinic with space group either P21/n (2, 4, 5 and 7) or P21 (3). Unit cell dimensions and contents are: for 1, a = 7.2027(17), b = 7.5699(17), c = 12.9615(16) Å, α = 84.464(14), β = 86.387(15), γ = 75.580(14)°, Z = 2; for 2, a = 7.407(3), b = 6.987(3), c = 27.653(11) Å, β = 94.906(7)°, Z = 4; for 3, a = 8.2816(18), b = 23.151(6), c = 3.9338(10) Å, β = 95.255(19)°, Z = 2; for 4, a = 11.209(2), b = 8.7858(19), c = 15.171(3) Å, β = 93.717(4)°, Z = 4; for 5, a = 26.377(3), b = 10.1602(12), c = 5.1384(10) Å, β = 91.996(13)°, Z = 4; for 6, a = 11.217(3), b = 14.156(5), c = 4.860(3) Å, α = 99.10(4), β = 96.99(4), γ = 76.35(2)°, Z = 2; for 7, a = 12.830(4), b = 8.145(3), c = 14.302(4) Å, β = 102.631(6)°, Z = 4. In all compounds at least one primary linear intermolecular N+–H⋯O(carboxyl) hydrogen-bonding interaction is present which, together with secondary hydrogen bonding results in the formation of mostly two-dimensional network structures, exceptions being with compounds 4 and 5 (one-dimensional) and compound 6 (three-dimensional). In only two cases (compounds 1 and 4), are weak cation–anion or cation–cation π–π interactions found while weak aromatic C–H⋯O interactions are insignificant. The study shows that all compounds fit the previously formulated classification scheme for primary and secondary interactive modes for proton-transfer compounds of 3,5-dinitrosalicylic acid but there are some unusual variants.

Graphical Abstract

The crystal structure determinations of the anhydrous 1:1 proton-transfer compounds of 3,5-dinitrosalicylic acid with aniline and a set of six monosubstituted anilines (2-hydroxy-, 2-methoxy-, 3-methoxy-, 4-fluoro-, 4-chloro- and 2-aminoaniline) have allowed the hydrogen-bonding systematics to be examined.