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An intrinsic shortcoming of self-organizing materials is their susceptibility to structural changes by mechanical forces and exposure to chemicals and radiation. Cross-linking of the molecules in the desired supramolecular structure is a generally applicable pathway to structurally more stable materials but is difficult to apply to self-organizing materials because the introduction of cross-linkable groups affects their self-organization and the process of cross-linking may alter the supramolecular structure of the 10 preceding phase. Reported here are the synthesis, thermal properties, and cross-linking of octaalkylthio substituted tetraazaporphyrins that contain either eight terminal azide groups or eight terminal acetylene groups. Synthesis of these compounds requires the preparation of the azide and alkyne containing sidechains and their reaction with 1,2-dicyanoethylene-1,2-dithiolate to the corresponding maleodinitrile intermediates. All maleodinitriles are successfully converted to tetraazaporphyrins by the established Mg 15 templated cyclotetramerization in typical yields of 60-70%. Thermal properties of the metal-free and copper(II) metallated tetraazaporphyrins were studied by thermal gravimetric analysis, polarized optical microscopy, differential scanning calorimetry, and variable temperature powder X-ray diffraction measurements. Azide substituted tetraazaporphyrins with trimethylene and hexamethylene spacers as well as acetylene derivatives with with trimethylene spacers unexpectedly display columnar mesophases over 20 ranges of temperature from 30 ºC to 110 ºC. A thermally activated cross-linking of a hexagonal columnar mesophase by cycloaddition at 65 ºC is demonstrated for a 1:1 mixture of azide and acetylene derivatives. At this temperatures the reaction progresses for up to 48 hours but renders the mesophase insoluble and stable to above 200 ºC. The structure of the mesophase is surprisingly little affected by the cross-coupling process that reaches a conversion of 60% of all azide and acetylene groups based on IR measurements. 25 Conversion of up to 80% of azide and acetylene groups is reached by copper catalysed cross-linking of a 1:1 mixture in solution to generate insoluble polymers. A similar degree of conversion is achieved by copper catalysed cross-linking of a 1:1 mixture as Langmuir film after 3 hours. However, transfer of intact cross-linked Langmuir films onto substrates was not successful.

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Polyaromatic dyes, such as phthalocyanines and tetraazaporphyrins (TAPs), arrange with an edge-on orientation of the macrocycle in almost all Langmuir and Langmuir-Blodgett (LB) monolayers, especially when condensed at higher surface pressures. Presented here is a new amphiphilic TAP that contains eight terminal carboxylic acid groups attached to the macrocycle via decyl spacers, which forms stable Langmuir and LB monolayers with a flat-on orientation of the macrocycle. A spider-like molecular conformation is proposed based on the measured surface area per molecule and film thickness determined by ellipsometry and AFM. This conformation allows all eight terminal carboxylic acid and carboxylate groups to attach to the polar interface while the aromatic macrocycle sits on top of the orthogonal decyl chains to generate a micro-segregated layer structure. Octa-acid TAPs with shorter alkyl spacers form edge-on structures in Langmuir monolayers upon compression and are not free of 3dimensional aggregates based on observations by Brewster angle microscopy (BAM). All octa-acid TAPs are prone to spontaneous self-assembly that is attributed to strong interactions between carboxylic acid groups. Aggregation and spontaneous self-assembly can be minimized by deprotonation of the carboxylic acid groups but all octa-acid TAPs become water soluble when more than four carboxylic acid groups are deprotonated at a pH higher than 8. Cu(II) chelates of the octa-acid TAPs were also prepared but are unsuitable for Langmuir monolayer formation because of insufficient solubility in spreading solvents. Langmuir and LB monolayers of octa-hydroxy TAPs with propyl and undecyl spacers were also studied for comparison. An edge-on orientation of the macrocycle is obtained at higher surface pressures for both TAPs, although a flat-on orientation of the macrocycle in a spider-like confirmation may be present at low surface pressure for the derivative with undecyl spacers. No mesophases are formed by any of the octa-acid and -hydroxy TAPs as confirmed by polarized optical microscopy and thermal analysis measurements. In fact, of the octa-acid TAPs, only the derivative with the longest spacer (decyl) melts at a temperature below the onset of thermal decomposition.

Donor-acceptor structures have recently gained great popularity for the design of low band gap polymeric organic semiconductors. Presented here is a first systematic study of organic semiconductors based on columnar liquid crystals that consist of discotic and board-shaped donor-acceptor structures. The discotic benzotristhiophenetricarboxamide and hexaphenyldiquinoxalinophenazine derivatives form hexagonal columnar mesophases over wide temperature ranges while the board-shaped tetraphenylquinoxalinophenanthrophenazine derivative displays rectangular and hexagonal columnar mesophases. All compounds are designed to preferentially conduct electrons and not holes because the central acceptor parts, which are the sole contributors to the unoccupied frontier orbitals, show strong intermolecular electronic interactions within columnar stacks whereas the donor parts at the periphery of the cores, the sole contributors to the occupied frontier orbitals, are too far apart to provide sufficient electronic interactions. The absence of hole conduction is confirmed by charge carrier mobility measurements based on time-resolved microwave conductivity and time-of-flight methods that reveal intrinsic electron mobility values of about 10 -2 cm 2 V -1 s -1 . The board-shaped compound is also highly fluorescent not only in solution but also in its mesophases. Interstingly, the fluorescence quantum yield of its mesophases reversibly increases with decreasing temperature, which is reasoned with changes in molecular mobility and intracolumnar packing within columnar stacks.