New columnar Zn-phthalocyanine designed for electronic applications.

Columnar liquid crystals are composed of disk-shaped aromatic molecules surrounded by flexible side chains, where molecules self-assemble in columns and thereby form large surface-oriented domains. These systems are known for their good charge and exciton transport along the columns, with mobilities approaching those of aromatic single crystals. Such semiconducting materials are promising for devices applications, since the output efficiency can be tuned by properly aligning columns. In the work presented here, the synthesis and characterization of a new Zn-phthalocyanine (ZnPc) is described which exhibits remarkable properties, such as hexagonal columnar order, achieved by cooling down from the isotropic phase to room temperature. Such order was confirmed by optical microscopy and X-ray diffraction experiments. Diodes were constructed using spin-coated films, and the conductive properties were investigated by current versus voltage analysis, where mobilities of 10(-3) and 10(-2) cm(2)/(V s) were obtained for the nonannealed and annealed films, respectively.

Luminescent columnar liquid crystals based on tristriazolotriazine.

Five discotic molecules comprising a tris[1,2,4]triazolo[1,3,5] triazine core were designed and synthesized to obtain luminescent and charge-transporting columnar liquid crystalline materials. With the exception of one compound containing terminal hydroxyl groups all compounds presented a wide thermal range and stable columnar liquid crystalline phase, characterized by differential scanning calorimetry, polarized optical microscopy, and X-ray diffraction (XRD) techniques. The phase formation appeared to be associated to some extent with interdigitation of the alkoxy and benzylalkoxy portion, as suggested by the XRD results. All compounds have a strong blue luminescence in solution and solid phase. At the temperature at which the compounds enter in the mesophase the luminescence decreases significantly. This result suggests that entrance into the Col(h) phase is accompanied by a better π-stacking of the peripheral phenyl rings compared to the solid phase, consistent with the intramolecular distances (3.5 Å) observed in the XRD analysis. These compounds based on tristriazolotriazine are quite robust with good optical and thermal properties for application as solid state emitters, and we anticipate that they may provide an interesting alternative to other discotic molecules based on N-heterocycles, which generally present a high-temperature Col(h) phase.

trans-Diaqua-bis{1,3-bis-[5-(2-pyrid-yl)-2H-tetra-zol-2-yl]propane}zinc(II) bis-(perchlorate).

The Zn(II) ion in the title compound, [Zn(C(15)H(14)N(10))(H(2)O)(2)](ClO(4))(2), lies on a centre of symmetry. The distorted N(4)O(2) octa-hedral coordination environment around the Zn atom is composed of two 1,3-bis-[5-(2-pyrid-yl)-2H-tetra-zol-2-yl]propane ligands (L1) and two water mol-ecules, coordinated in trans positions. The ligand acts as a typical bidentate chelating ligand through one of its 2-pyridyl-2H-tetra-zole units, forming a five-membered Zn-N-C-C-N metallacycle with a small N-Zn-N bite angle [77.40 (8)°]. The other 2-pyridyl-2H-tetra-zole unit remains uncoordinated. The average Zn-N distance (2.156 Å) is somewhat longer than the distance between the Zn(II) center and the aqua ligand [2.108 (2) Å]. The coordinated pyrid-yl-tetra-zoyl rings are quasi-coplanar, making a dihedral angle of 1.9 (2)°, while the uncoordinated rings show a larger inter-planar angle of 21.3 (2)°. The flexible propane spacer displays a zigzag chain. Inter-molecular O-H⋯N and O-H⋯O inter-actions result in two-dimensional polymeric structures parallel to (100). Two C atoms of the spacer are disordered over two positions, with site occupancy factors of ca 0.85 and 0.15.