The formation of molecular complexes (prereactive intermediates) between C3O2 and amines (ammonia, dimethylamine, trimethylamine, and 4-(dimethylamino)pyridine) as well as the subsequent transformation of the complexes into C3O2−amine zwitterions in cryogenic matrixes (ca. 40 K) has been observed. In the case of dimethylamine, the formation of tetramethylmalonamide has also been documented. Calculations using density functional theory (B3LYP/6-31G(2d, p)) are used to assign all above species and are in excellent agreement with the IR spectra.

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The structure of a coumarin ester is reported and compared with the results of a quantum chemical calculation. In the crystal, inter­molecular C—H⋯O contacts generate an infinite C(6) chain along the b axis. C=O⋯π and π–π stacking inter­actions also occur. Hirshfeld surface analysis was used to confirm and qu­antify the supra­molecular inter­actions.

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