Competing intermolecular interactions in some 'bridge-flipped' isomeric phenylhydrazones.

To examine the roles of competing intermolecular interactions in differentiating the molecular packing arrangements of some isomeric phenylhydrazones from each other, the crystal structures of five nitrile-halogen substituted phenylhydrazones and two nitro-halogen substituted phenylhydrazones have been determined and are described here: (E)-4-cyanobenzaldehyde 4-chlorophenylhydrazone, C(14)H(10)ClN(3), (Ia); (E)-4-cyanobenzaldehyde 4-bromophenylhydrazone, C(14)H(10)BrN(3), (Ib); (E)-4-cyanobenzaldehyde 4-iodophenylhydrazone, C(14)H(10)IN(3), (Ic); (E)-4-bromobenzaldehyde 4-cyanophenylhydrazone, C(14)H(10)BrN(3), (IIb); (E)-4-iodobenzaldehyde 4-cyanophenylhydrazone, C(14)H(10)IN(3), (IIc); (E)-4-chlorobenzaldehyde 4-nitrophenylhydrazone, C(13)H(10)ClN(3)O(2), (III); and (E)-4-nitrobenzaldehyde 4-chlorophenylhydrazone, C(13)H(10)ClN(3)O(2), (IV). Both (Ia) and (Ib) are disordered (less than 7% of the molecules have the minor orientation in each structure). Pairs (Ia)/(Ib) and (IIb)/(IIc), related by a halogen exchange, are isomorphous, but none of the 'bridge-flipped' isomeric pairs, viz.

Intermolecular C-F...H-C contacts in the molecular packing of three isostructural N-(fluorophenyl)mannopyranosylamines.

Among the three compounds reported here, namely N-(4-fluorophenyl)-β-D-mannopyranosylamine, (I), N-(3-fluorophenyl)-β-D-mannopyranosylamine, (II), and N-(2-fluorophenyl)-β-D-mannopyranosylamine, (III), all with chemical formula C(12)H(16)FNO(5), (I) and (II) are isostructural, whereas (III) assumes the same packing arrangement as the unfluorinated analogue N-phenyl-β-D-mannopyranosylamine, (IV), which has been reported previously. Similarities with respect to the intermolecular hydrogen-bonding patterns exist across the series (I)-(III). A packing motif that distinguishes the shared packing arrangement of (I) and (II) from that of (III) is a C-F.

4-(4-Chlorobenzylidenehydrazonomethyl)benzonitrile and the bromo and iodo analogs.

4-Cyano-4'-chlorobenzalazine [systematic name: 4-(4-chlorobenzylidenehydrazonomethyl)benzonitrile], C(15)H(10)ClN(3), occurs in two polymorphs. Polymorph A is isostructural with the corresponding dichloro compound. Polymorph B is isostructural with the bromo and iodo analogs, viz.

Isostructuralism among bridge-flipped' isomeric benzylideneanilines and phenylhydrazones.

Bridge-flipped' isomers may be defined as pairs of molecules related by a reversal of a bridge of atoms connecting two major parts of the individual molecules. This kind of isomerism is commonly found among benzylideneanilines and phenylhydrazones. Isostructural pairs might be suitable for co-crystallization and are thus useful in the preparation of new solid materials.

Isomeric Schiff bases related by dual imino-group reversals.

Two isomeric pairs of Schiff bases, N,N'-bis(2-methoxybenzylidene)-p-phenylenediamine, C(22)H(20)N(2)O(2), (I), and 2,2'-dimethoxy-N,N-(p-phenylenedimethylene)dianiline, C(22)H(20)N(2)O(2), (II), and (E,E)-1,4-bis(3-iodophenyl)-2,3-diazabuta-1,3-diene (alternative name: 3-iodobenzaldehyde azine), C(14)H(10)I(2)N(2), (III), and N,N'-bis(3-iodophenyl)ethylenediimine, C(14)H(10)I(2)N(2) [JAYFEV; Cho, Moore & Wilson (2005). Acta Cryst. E61, o3773-o3774], differ pairwise only in the orientation of their imino linkages and in all four individual cases occupy inversion centers in the crystal, yet all four compounds are found to assume unique packing arrangements.