Separation and mesogenic properties of tetraalkoxy-substituted phthalocyanine isomers

The main aim of this paper is to describe the separation and properties of four possible structural isomers of non-peripherally substituted nickel(II) phthalocyanine. Two isomers (C-4h and D-2h) of this compound were separated by preparative thin layer chromatography; however the other two isomers (C-2v and C-s) were separated by HPLC only with an analytical chiral column. The individual isomers and symmetry were assigned on the basis of the H-1 NMR signals of the aromatic protons of the phthalocyanine ring system. The pure C-4h isomer exhibited liquid crystalline properties at room temperature while the isomeric mixture containing four structural isomers was liquid. The other three isomers were liquid under the same conditions. The mesogenic properties of pure C-4h isomer were determined by differential scanning calorimetry, optical polarizing microscopy and X-ray diffractometry. This is the first report of the separation of a liquid crystalline pure isomer in the field of phthalocyanine chemistry.