Synthesis, characterization, and computational study of N,N′-bis (2′,4′-dihydroxyphenyl)-1.4-quinonediimine, a hydroxyl-capped three-ring quinonediimine with sterically hindered substituent on outer rings

Density functional calculations were performed on N,N′-bis (2′,4′-dihydroxyphenyl)-1.4-quinonediimine, a hydroxyl-terminated quinonediimine with an additional meta-hydroxyl substituent on each outer ring. Results of the calculations were compared to experimental properties of the herein synthesized compound. The calculated LUMO levels for isomers of the title compound range from −2.764 to −3.279 eV. The calculated electron affinities range from 1.398 to 1.989 eV. Both the LUMO levels and electron affinities are greatest in magnitude for the syn, anti isomer. The HOMO levels, on the other hand, range from −5.383 eV (for the anti, anti isomer) to −5.541 eV (syn, anti). The predicted electronic transitions for the molecule in ethanol solvent correspond closely to those seen at 580 and 254 nm. The isomers vary widely in energy, leading to a marked preference for the syn, syn (outer) isomer - a direct result of the steric effect of the hydroxyl group at the 2′ position.