Formation of isostructural solid solutions in 2,6-disubstituted N-phenylformamides and N-phenylthioamides.
In order to investigate possible isostructural solid solutions of disubstituted N-phenylformamides and thioamides, we have studied the re-crystallization of pairs of compounds selected from 2,6-difluoro-N-phenylformamide (I), 2,6-dichloro-N-phenylformamide (II), 2,6-dimethyl-N-phenylformamide (III), 2,6-dichloro-N-phenylthioamide (IV), 2,6-dimethyl-N-phenylthioamide (V), 2,6-diisopropyl-N-phenylformamide (VI) and 2,6-diisopropyl-N-phenylthioamide (VII). For single-component 2,6-disubstituted-N-phenylformamides only the trans form occurs in the pure crystal, while for thioamides the cis form occurs, with only one exception. By forming solid solutions of pairs of these molecules the resulting structures all adopt similar N-H...O/S chains in the crystals. Solid solutions (1), (2) and (3), resulting from the mixing of (I) and (II), (II) and (III), and (IV) and (V), respectively, are all isostructural with each other (space group Pbca). Only co-crystal (1) is isostructural to both starting materials, while (2) is isostructural to only one of the starting pair, (II). Solid solution (3), which adopts the same Pbca structure as (1) and (2), is different to the monoclinic structures of both the reactants. Solid solution (4) is monoclinic, with similar hydrogen-bonded chains, and isostructural to the two components, resulting from the composition from the mixing of (VI) and (VII). Isostructural indices were used to quantify crystal-packing similarities and differences. Occupancy factors of the reactants in each co-crystal differ widely.
School of Chemistry and Physics, Westville Campus, University of KwaZulu Natal, Private Bag X54001, Durban, KwaZulu Natal 4000, South Africa.
Bernard
B
Omondi
Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, PO WITS, Johannesburg, Gauteng 2050, South Africa.
Andreas
A
Lemmerer
Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, PO WITS, Johannesburg, Gauteng 2050, South Africa.
Manuel A
MA
Fernandes
Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, PO WITS, Johannesburg, Gauteng 2050, South Africa.
Demetrius C
DC
Levendis
Anorganische und Analytische Chemie, Westfälische Wilhelms Universität Münster, D-48149 Münster, Germany.
Marcus
M
Layh
D003460:Crystallization; D018360:Crystallography, X-Ray; D005559:Formamides / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D012996:Solutions; D013854:Thioamides / Q000737:chemistry*
D005559:Formamides; D012996:Solutions; D013854:Thioamides; C045976:N-phenylformamide
co-crystal; crystal engineering; isostructural; solid solution