Syntheses, structures, and mesomorphic properties of two series of oxovanadium(IV) salen and salpn complexes with 4-substituted long alkoxy chains

Two series of oxovanadium(IV) salen and salpn complexes containing 4-substituted alkoxy chains of aromatic rings, [VO((4-CnH2n+1O)2salen)] (n = 3 (1), 4 (2), 6 (3), 8 (4), 10 (5), 12 (6), 14 (7), 16 (8), 18 (9), and 20 (10) and salen = N,N′-ethylenebis(salicylideneiminato)), and [VO((4-CnH2n+1O)2salpn)] (n = 8 (11), 10 (12), 12 (13), 14 (14), 16 (15), and 18 (16) and salpn = N,N′-propylenebis(salicylideneiminato)), have been prepared and their mesomorphic properties have been investigated. The crystal structures of 1–9 except for 7 by an X-ray crystallographic analysis have been revealed. Complexes 4–9 in the solid state have been confirmed as novel bilayer crystal structures composed of only the VO(IV) complex without linear chains via the Vdouble bond; length as m-dashO units. The VO(IV) complexes with longer alkoxy chains of 8–10 transferred from the bilayer crystal to the bilayer metallomesogens (liquid crystals). Based on the X-ray analyses and the precise extinction rules for 8–10 with the bilayer metallomesogens, complexes 8–10 were identified as the liquid crystalline (M(Pa21)) phase derived from 80 layer groups. On the other hand, the 4-alkoxysalpn complexes of 14–16 showed the unusual rectangular columnar mesophase (Colr) with the linear chain via the Vdouble bond; length as m-dashO units supported by the existence of the Vdouble bond; length as m-dashO stretching band characteristic of weak linear chain formation via the Vdouble bond; length as m-dashO units in the liquid crystal.