Crystal structure of the tri­ethyl­ammonium salt of 3-[(4-hy­droxy-3-meth­oxy­phen­yl)(4-hy­droxy-2-oxo-2H-chromen-3-yl)meth­yl]-2-oxo-2H-chromen-4-olate

The reaction between 3,3′-[(3-meth­oxy-4-hy­droxy­phen­yl)methanedi­yl]bis­(4-hy­droxy-2H-chromen-2-one) and tri­ethyl­amine in methanol yielded the title compound tri­ethyl­ammonium 3-[(4-hy­droxy-3-meth­oxy­phen­yl)(4-hy­droxy-2-oxo-2H-chromen-3-yl)meth­yl]-2-oxo-2H-chromen-4-olate, C(6)H(16)N(+)·C(26)H(17)O(8) (−) or (NHEt(3))(+)(C(26)H(17)O(8))(−), which crystallized directly from its methano­lic mother liquor. The non-deprotonated coumarol substituent shares its H atom with the deprotonated coumarolate substituent in a short negative charge-assisted hydrogen bond in which the freely refined H atom is moved from its parent O atom towards the acceptor O atom, elongating the covalent O—H bond to 1.18 (3) Å. The respective H atom can therefore be described as being shared by two alcohol O atoms, culminating in the formation of an eight-membered ring.