Novel Ionic Mesogenic PyTp and ImTp Molecules at Air-Water and Air-Solid Interfaces

The studies on discotic molecules at air-water (A-W) and air-solid (A-S) interfaces have drawn lot of attention [1, 2]. The thin films of discotic mesogens have technological applications in the fabrication of gas sensors [3], field-effect transistors [4], photovoltaic diodes [5], solar cells and optical displays [6]. In addition, these systems have scientific interest in modeling of Π-Π and steric interactions in two-dimensional and biological systems [7]. Disk-like molecules, like porphyrins, vitamins and so on, play significant role in living systems as well. At A-W interface, discotic mesogens can self-assemble into one-dimensional columnar superstructures due to the overlapping of Π-orbitals of adjacent molecules and can arrange in a twodimensional lattice, thereby forming stable Langmuir monolayers [2, 8]. These films need to be transferred to solid supports for practical applications. The preparation of ultra thin films by means of Langmuir-Blodgett (LB) technique is an efficient method to obtain highly ordered layers over large areas [9]. LB technique has the advantage of both macroscopical and microscopical influence on the molecular arrangement by means of the surface pressure variations and interactions with the aqueous subphase. LB films of discotic mesogens have been reported to have a surface morphology which are periodically modulated by columns that lie predominantly along the film deposition direction [1]. Evidence has been presented for square-lattice discotic structure in the bilayer films