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

By M. Tabatabaee, M. R. Fotuhiardakani and Alan J. Lough


The title compound, C22H28N2O4, 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 –CH2– groups is disordered over two sets of sites with refined occupancies of 0.659 (8) and 0.341 (8)

Topics: Organic Papers
Publisher: International Union of Crystallography
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Provided by: PubMed Central

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  4. (2007). The title compound contains two centrosymmetric independent molecules [A and B] (see Figs. 1 and 2). In the original crystal structure determination