Supramolecular structures in N-isonicotinoyl arylaldehydehydrazones: multiple hydrogen-bonding modes in series of geometric isomers

Abstract

Sixteen N-isonicotinoyl arylaldehydehydrazones, NC(5)H(4)CONHN=CHC(6)H(4)R, have been studied and the structures of 14 of them have been determined, including the unsubstituted parent compound with R = H, and the complete sets of 2-, 3- and 4-substituted geometric isomers for R = F, Br and OMe, and two of the three isomers for R = Cl and OEt. The 2-chloro and 3-chloro derivatives are isostructural with the corresponding bromo isomers, and all compounds contain trans amide groups apart from the isostructural pair where R = 2-Cl and 2-Br, which contain cis amide groups. The structures exhibit a wide range of direction-specific intermolecular interactions, including eight types of hydrogen bonds, N-H...N, N-H...O, O-H...O, O-H...N, C-H...N, C-H...O, C-H...pi(arene) and C-H...pi(pyridyl), as well as pi...pi stacking interactions. The structures exhibit a very broad range of combinations of these interactions: the resulting hydrogen-bonded supramolecular structures range from one-dimensional when R = 2-F, 2-OMe or 2-OEt, via two-dimensional when R = 4-F, 3-Cl, 3-Br, 4-OMe or 3-OEt, to three-dimensional when R = H, 3-F, 2-Cl, 2-Br, 4-Br or 3-OMe. Minor changes in either the identity of the substituent or its location can lead to substantial changes in the pattern of supramolecular aggregation, posing significant problems of predictability. The new structures are compared with the recently published structures of the isomeric series having R = NO(2), with several monosubstituted analogues containing 2-pyridyl or 3-pyridyl units rather than 4-pyridyl, and with a number of examples having two or three substituents in the aryl ring: some 30 structures in all are discussed.

(Pyrazinecarbonyl)hydrazone halobenzaldehydes: supramolecular arrays generated by face to face stacking of ribbons, formed from C–H–O interactions

“…This was well illustrated in the recent reports on the supramolecular structures of various N-isonicotinoyl arylaldehyde hydrazones [6], and N-arylpyrazi-necarboxamides [1]. We are also interested in the interplay between intra-and intermolecular forces and the interplay of hard and soft hydrogen bonds [8].…”

“…The situations in the N-isonicotinoyl arylaldehyde hydrazone series, 6, are somewhat different in that derivatives (6: ¼ o-Cl and o-F) have cis-amido arrangements with the o-halo substituents on the same edge of the molecule as the N--H bond. In (6: X ¼ m-Cl and m-Br), both trans amides, the meta halogens are on the edge opposite the NH bond [6]. A more complex situation pertains with (6: X ¼ m-F) arising from its two independent molecules, with one exhibiting conformational disorder [6].…”

“…In (6: X ¼ m-Cl and m-Br), both trans amides, the meta halogens are on the edge opposite the NH bond [6]. A more complex situation pertains with (6: X ¼ m-F) arising from its two independent molecules, with one exhibiting conformational disorder [6].…”

“…Following on from the study of N-arylpyrazinecarboxamides [1], and of pyrazine-2-carbohydrazide [13] we now wish to report on the crystal structures of acylhydrazones, derived from pyrazinoylhydrazine and monohalobenzaldehydes (7: N 2 C 4 H 3 CONHN¼CHC 6 …”

“…We have been very much interested in crystal structures of series of nitrogen containing compounds, including aromatic amido compounds (1-3) [1][2][3] and hydrazones derived from reactions of hydrazines with arenealdehydes, (4) [4], and arylketones (5) [5], acylhydrazones derived from are-nealdehydes and acylhydrazines (6) [6,7], see Fig. 1.…”