Solvate and dimer equilibria in solutions of chlorophyll

Abstract

The spectrum of chlorophyll b in very dry hydrocarbon solvents exhibits two maxima, of equal intensity, at 641 and 659 nm which are attributed to the chlorophyll dimer, whilst the spectrum in presence of basic solvent, having a single maximum at 641 nm, is attributed to the monosolvate. Unsolvated monomeric chlorophyll is probably never present in significant amounts in solution and assignment of the 659 nm band to an n-π * transition is almost certainly incorrect. When the basic solvent is pyridine the constant for the equilibrium dimer + 2 solvent ⇌ 2 monosolvate is 1·0 ± 0·2 x 10 3 l. mole -1 .