Mono- and multilayer films of discotic metal-(alkythio)tetraazaporphyrins

Abstract

We report on the use of a copper compound of 2,3,7,8,12,13,17,18-octakis(octylthio)-5,10,15,20-tetraazaporphyrin for the fabrication of a spreading monolayer and Langmuir-Blodgett films. This compound, as a free ligand or metal substituted, gives mesogenic material with a discotic, columnar structure. Its structural and magnetic properties have been characterized by optical and ESR spectroscopies. The spreading monolayer was not homogeneous and use of a typical film-forming amphiphile, such as stearic acid, was necessary for obtaining stable, reproducible surface films, which were easily transferred onto quartz plates treated with dimethyldichlorosilane. The properties of the film were also analyzed with both UV-vis and ESR spectroscopies. The film did not show orientation order, and the discotic material maintained a columnar aggregate structure

Metal ion mediated mesomorphism and thin film behaviour of amphitropic tetraazaporphyrin complexes

“…Therefore, a columnar stacking of macrocycles comparable to the Col hd mesophase of Cu52 can be excluded, since this arrangement would cause a blue-shift of the Q-bands. 14,32 However, a tilted columnar arrangement, where the molecular plane is not normal to the axis, has been shown to cause a redshift and a decrease in the extinction coefficient of the Q-band. Tilted columnar arrangements are typical for the crystalline phases of porphyrazines and phthalocyanines and usually are of oblique or rectangular symmetry.…”

“…12 However, the aim of this study was to investigate the thermotropic as well as lyotropic mesomorphism of the octakis (3,6-dioxaheptylthio) and octakis (3,6,9-trioxadecylthio) substituted tetraazaporphyrins and their metal complexes as mesogens containing a medium sized aromatic system. 13,14 Experimental Materials All commercially available chemicals were of analytical grade; solvents were dried over molecular sieves and used without further purification. For flash chromatography Matrix Silica Si chromatography medium (60 A ˚35-70 mm particle size), a product of Amicon (Witten, Germany), or RP-18 material from Merck (LiChroprep RP-18, 25-40 mm) was used.…”

Monolayers of triaroylbenzene derivatives

“…Monolayers of triarylpyrylium tetrafluoroborates substituted with six dodecyloxy chains were found to adopt the edge-on orientation upon compression but to form a nematic ordering after transfer to solid supports [12]. Metal-(alkylthio) tetraazaporphyrins did not form stable monolayers alone, and displayed limiting molecular areas smaller than would be consistent with either edge-on or face-on orientations [13]; however, stable monolayers were found in mixtures with stearic acid. Monolayers of asymmetric discogens in which one group projecting from the core is highly amphiphilic favor the edge-on orientation and can give Langmuir-Blodgett films characterized as two-dimensional discotic phases with the columns oriented parallel to the solid support, as was found for monolayers and films of pentakis((4-pentylphenyl)ethynyl)phenoxy-undecanoic acid [14,15].…”

“…X-ray reflectivity and grazing incidence X-ray diffraction data confirmed the edge-on orientation was favored on compression even for triphenylenes symmetrically substituted with six identical alkoxy groups [9]. Disc-shaped molecules with a variety of other structures have also been studied as monolayers and thin films [10][11][12][13][14][15][16][17][18][19]. The earliest reports of monolayers of discotic molecules at the waterair interface concerned those of the benzene-hexa-n-alkanoates (n =5-8), which were found to have the benzene ring flat on the surface and to exhibit a liquid-expanded to liquid-condensed phase transition [10,11].…”

Face- and edge-on orientations of octa-acid and -alcohol substituted tetraazaporphyrins in Langmuir and Langmuir–Blodgett monolayers

“…12,15 More stable Langmuir and LB lms have been obtained with mixtures of at-on oriented Pcs with fatty acids or other aliphatic surfactants to provide a ratio of the foot prints of aliphatic chains and macrocycle close to 1. [16][17][18] Langmuir and LB monolayers of TAPs [19][20][21][22][23][24][25] have attracted much less attention than Langmuir and LB lms of Pcs although their lower propensity for co-facial aggregation 26 makes them better candidates for lms with at-on oriented macrocycles. The only attempt of preparing TAP LB monolayers with at-on orientation of the macrocycle we are aware of was based on oligo(ethylene oxide) substituted TAPs.…”