Crystal structures of cocrystals/salts containing aminopyrimidines/aminotriazines: implications for crystal engineering

Abstract

PART-I Hydrogen bonding patterns involving aminopyrimidine cocrystal/ salt interactions Chapter I Hydrogen bonding patterns in the co-crystal structures of 2-amino- 4,6 dimethoxypyrimidine-4-aminobenzoic acid [1/1] (1), 2-amino- 4,6-dimethoxypyrimidine-anthranilic acid [1/1] (2), 2-amino 4,6- dimethoxypyrimidine-phthalic acid [1/1] (3), 2-amino-4,6- dimethoxypyrimidine-2,4-dichlorobenzoic acid (1/1) (4) and 2- amino-4,6-dimethylpyrimidine-fumaric acid (0.5/0.5) (5) In all the compounds, the carboxylic acid group interacts with the corresponding 2-aminopyrimidine moiety through N-H?O and O-H?N hydrogen bonds to form an R22(8) ring motif. In compound 1, the R22(8) motif further self organizes through N-H?O hydrogen bonds to generate an array of six hydrogen bonds with rings having the graph-set notations R23(6), R22(8), R42(8), R22(8) and R23(6). The 4- aminobenzoic acid molecules self-assemble via N-H?O hydrogen bonds to form a supramolecular chain along the c-axis, with the graph-set notation C(9). In compound 2, inversion-related bases (molecules (AandB)) are paired via N(2)- H?N(3) hydrogen bonds forming another type of R22(8) motif. The carboxyl oxygen atom (O3A) of anthranilic acid (Molecule A) is linked to 4-amino group (N4B) of anthranilic acid (Molecule B) via N-H?O hydrogen bonds. In compound 3, the nitrogen atom (N3) and 2-amino (NH2) group of the pyrimidine ring also interact with carboxyl oxygen atoms (O5 and O6) to form an eight membered ring motif, generating a helical chain (made up of alternating pyrimidine and phthalic acid molecules) along the b-axis. This chain is interpenetrated by a centrosymmetrically related chain to which it is linked by and#61552;-and#61552; stacking of pyrimidines. In compound 4, the R22(8) motifs are centrosymmetrically paired via N-H?O hydrogen bonds to produce DADA (D-donor andA-acceptor) array of quadruple hydrogen bonds. The quadruple DADA arrays are further extended into ladders by pairs of C-H?O hydrogen bonds to form a R22(8) ring motif.