Synthesis, structure and luminescence of novel 2D co-crystals based on asymmetric 5-substituted pyrimidines and isophthalic acid: Alternate arrangement and π–π interactions

Two novel organic co-crystals (A) (isophthalic acid) (1) and (B) (isophthalic acid) (2), were generated based on asymmetric building blocks 5-(4-pyridyl)pyrimidine (A) and 5-(4-(1-imidazolyl)phenyl)pyrimidine (B) with isophthalic acid, respectively. The building blocks interlinked with isophthalic acid through intermolecular H-bonding interactions to generate infinite chains, which further extended 2D planar networks. In addition, the luminescent properties of A, B and 1, 2 were investigated primarily in the solid state. Compared with the free building blocks, the emission maxima of 1 and 2 have not been changed, but emission intensities of 1 and 2 have decreased. The structure–property relationship indicates the luminescent property is dependent on the intermolecular – ABAB – alternate arrangement and the intermolecular π–π contacting characteristic. By incorporation of conformers into the co-crystals, the results display more interesting tunability of the emission intensities of the building modules in this study.