Structural Study on Solvates of Dopamine-Based Cyclic Imide Derivatives

A structural study on two dopamine-based imide derivatives, namely, 2-(3,4-dihydroxyphenethyl)isoindole-1,3-dione (1) and 2,6-bis-[2-(3,4-dihydroxyphenyl)ethyl]pyrrolo [3,4-f]isoindole-1,3,5,7-tetrone (2), and their solvates was carried out. The compound 1 (Z′ = 2) was crystallized through a melt crystallization process, whereas its two solvates (Z′ = 1 of each), containing one water molecule (1a) and the other containing two quinoline molecules (1b) in their crystal lattices, respectively, were obtained through solution crystallization. The reasons for Z′ = 2 arising from symmetry nonequivalent molecules in the unit cell of 1 is attributed to the nonparallel arrangement of two layers of self-assembled molecules in crystal lattice, where one layer has C−H···π and another layer has CO···π interactions. Four different solvates of compound 2 (Z′ = 0.5 of each), containing two DMF molecules (2a), two DMSO molecules (2b), two pyridine molecules (2c), and six quinoline molecules (2d), were also obtained through solution crystallization of 2 in respective solvents. Solvate 2d has channels in its structure which are formed by interaction of 2 with quinoline molecules through O−H···N and C−H···π interactions. Additional quinoline molecules reside in these channels of approximately (11 × 12) Å dimension. Structural features of all the compounds and their solvates have been studied by single crystal X-ray structures, powder X-ray diffractions (PXRD), thermogravimetric analyses (TGA), and differential scanning calorimetric (DSC) measurements.