Hydrogen-bonding Patterns in Pyrimethaminium Picolinate

The title compound was prepared by reacting pyrimethamine [2,4-diamino-5-(p-chlorophenyl)-6-ethyl pyrimidine] and picolinic acid, [C12H14ClN4, C6H4NO2] in methanol. It crystallizes in the monoclinic P21/c space group. The unit-cell parameters are a = 9.5731(2) b = 8.7449(2) c = 21.8582(5)A, β = 99.9590(10)°. The final R-value is 0.0662 for 8517 measured reflections. The asymmetric unit contains a pyrimethamine cation and a picolinate anion. The protonated N1 atom is hydrogen bonded to one of the oxygen atoms via a N-H…O hydrogen bond. The carboxyl oxygen atom bridges the 2-amino group and the 4-amino group on either side in addition to the base pairing to form a DADA array (D = donor & A = acceptor in hydrogen bonding) of quadruple hydrogen bonding. The crystal structure is further stabilized by C-H…O, C-H…N and aromatic stacking interactions.