This report presents the single crystal X-ray structures of several substituted isoindolines that have been frequently used as starting materials for phthalocyanines, phthalocyanine analogs and related chelates. The structures of 1,3-diiminoisoindoline (1), 1,3-bis(hydroxyimino)isoindoline (2), 1,4-diaminophthalazine (3), 1,1,3-trichloroisoindoline (4) and 3-imino-1-oxoisoindoline (5) are reported; compounds 2 and 3 are synthesized from diiminoisoindoline (1) and 4 and 5 are produced from phthalimide. All five compounds are planar macrocycles, and localization of double bonds can be readily determined. We elucidated one of the known structures of 1 at low temperature, and observed two additional new structures of 1. For the crystal forms of 1 and compounds 2, 3, and 5, hydrogen bonding in the solid state was observed. Compounds 1, 2 and 3 form extended hydrogen bonded arrays in the solid state, whereas 5 forms discrete hydrogen bonded dimers.