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 mol-ecules (A and B). In the previous structure determination [Xia et al. (2007 ▶). Acta Cryst. E63, o259] both A and B were modelled as neutral mol-ecules 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 mol-ecule (A) crystallizes in the neutral (nonzwitterionic) form and the other in the zwitterionic form, namely 6,6'-dimeth-oxy-2,2'-[hexane-1,6-diylbis(nitrilo-dimethyl-idyne)]-di-phenol-6,6'-dimeth-oxy-2,2'-[hexane-1,6-diylbis(nitrilio-di-methyl-idyne)]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 mol-ecules (B) are involved in inter-molecular N-H⋯O hydrogen bonds forming one-dimensional chains along [001]. Each independent mol-ecule forms an intra-molecular O-H⋯N (A) or N-H⋯O (B) hydrogen bond. In mol-ecule 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).