Mesomorphic structure peculiarities of two mix-substituted phthalocyanines of the A₃B type

ABSTRACT

Mesomorphic properties and structures of two mix-substituted lipophilic phthalocyanine derivatives of the A₃B type, with a different ratio of electron-donating (hexadecyloxy-) and electron-withdrawing (Cl-) substituents on the isoindol fragments ‘A’ and ‘B’, correspondingly, were studied by polarising optical microscopy, differential scanning calorimetry and small-angle X-ray scattering. Both compounds display columnar mesophases, and the type of organisation of the columns in the mesomorphic state was found to strongly depend on the number of peripheral chlorine substituents in the molecule. The di-chloro-substituted phthalocyanine forms a solid pasty lamellar phase at room temperature, which on heating undergoes successive transitions to two large-lattice columnar mesophases (2D-Col_h and 3D-M_Col) arising from the aggregation of several phthalocyanine-containing piles. On the contrary, aggregation of columns does not occur for the tetra-chloro-substituted phthalocyanine, which forms a nematic columnar mesophase of single phthalocyanine piles (1D-N_Col). While the di-chloro-compound partly crystallises on cooling, the nematic phase of the tetra-chloro-compound freezes at room temperature. The reasons for this different self-organisation behaviour are not yet fully understood, but some hints may be deduced from the proposed supramolecular models.

GRAPHICAL ABSTRACT

KEYWORDS:

• Phthalocyanine
• mesogen
• columnar mesophase
• self-assembly
• SAXS
• DSC
• POM

Acknowledgement

The work was supported by the programme of the Ministry of Education and Science of the Russian Federation (Grant No. 16.1037.2017/4.6) and the Russian Foundation for Basic Research (Grant No. 16-03-00883a). BD and BH thank the CNRS and the Université de Strasbourg for support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work was supported by the programme of the Ministry of Education and Science of the Russian Federation [Grant No. 16.1037.2017/4.6] and the Russian Foundation for Basic Research [Grant No. 16-03-00883a].