Activation of the Fluorescence of Chlorophyll Solutions

Abstract

CHLOROPHYLL dissolved in pure dry hydrocarbons is (practically) non-fluorescent^1–3. The addition of traces of water, alcohols or amines to solutions of chlorophyll restores their fluorescent intensity to that observed in solvents such as methanol, ether, etc. It was demonstrated by Livingston, Watson and McArdle¹ that this increase in the fluorescent yield is the result of the formation of an addition compound between a molecule of chlorophyll and one of the ‘activator’. These authors postulated that the addition compound was formed by the establishment of hydrogen bonds between labile hydrogens of the activator and the keto oxygens of ring V⁴ of the chlorophyll molecule. Afterwards, Evstigneev, Gavriola, and Krasnovskii³ presented evidence supporting the view that the activator adds to the central magnesium atom rather than to ring V. They claimed that the fluorescence of pheophytin is as intense in dry as it is in wet toluene, but that the fluorescence of toluene solutions of the magnesium complex of phthalocyanine is increased by the addition of water.