Knowledge Bank

The interaction between carbonyl and phenyl chromophores is investigated in the series of compounds $\Phi COX$ (where X = F, C1, OH, $OCH3$, $CF3$ H, $CH3$, and $NH2$) dissolved in a methylcyclohexane matrix at $65\circ K$ . With the first series members (up to X $=OCH3$) both the lowest singlet and triplet states are $\Pi \Pi \ast$ states, whereas with the latter series members of the $\Pi \Pi \ast$ states appear to be the lowest energy. These observations correlate with the ir carbonyl stretching frequencies which are greater than $1725cm-1$ for the beginning series members and less than $1725cm-1$ for the latter ones. Some of these compounds seem to show dual phosphorescence.