Fulvenes and Thermochromic Ethylenes, Part 53 The Fine Structure of 2‐Arylmethylene‐1,3‐Indandiones; their Dipole Moments and Electronic Spectra

The molar refractions (polarizabilities) and dipole moments of fourteen 2‐arylmethylene‐1,3‐indandiones (I) and the electronic absorption spectra of twenty‐one representatives of this series have been measured. From these data certain features of the fine structure of the compounds have been deduced; inter alia, the carbonyl groups in I are bent away from the benzene ring of the indane moiety, and the 4‐dimethylaminophenyl compound II exists to a significant extent in the zwitterionic form IIA.