Redetermination of 6,6′-dimeth­oxy-2,2′-[hexane-1,6-diylbis(nitrilo­dimethyl­idyne)]diphenol

The title compound, C(22)H(28)N(2)O(4), contains two independent centrosymmetric mol­ecules (A and B). In the previous structure determination [Xia et al. (2007 ▶). Acta Cryst. E63, o259] both A and B were modelled as neutral mol­ecules with the H atoms of the the O—H groups included in calculated positions. In this redetermination, the transferrable H atoms were located in difference maps and freely refined, indicating that one mol­ecule (A) crystallizes in the neutral (nonzwitterionic) form and the other in the zwitterionic form, namely 6,6′-dimeth­oxy-2,2′-[hexane-1,6-diylbis(nitrilo­dimethyl­idyne)]­di­phenol–6,6′-dimeth­oxy-2,2′-[hexane-1,6-diylbis(nitrilio­di­methyl­idyne)]diphenolate (1/1). This finding is supported by significant differences in the C—O(H) (A) and C—O(−) (B) bond lengths. In the crystal, the zwitterionic mol­ecules (B) are involved in inter­molecular N—H⋯O hydrogen bonds forming one-dimensional chains along [001]. Each independent mol­ecule forms an intra­molecular O—H⋯N (A) or N—H⋯O (B) hydrogen bond. In mol­ecule B, one of the –CH(2)– groups is disordered over two sets of sites with refined occupancies of 0.659 (8) and 0.341 (8).