Regiospecific synthesis of tetrasubstituted phthalocyanines and their liquid crystalline order

Abstract

Metal-free and metal(II) all-endo-tetraalkoxy-phthalocyanines of C4h symmetry are synthesised regiospecifically from 3-(2-butyloctyloxy)phthalonitrile with lithium octanolate and subsequent metal ion exchange. The voluminous, yet not overly large, and racemically disordered alkoxy substituent not only renders the cyclotetramerisation regiospecific, but also leads to liquid crystalline self-assembly with attainable clearing temperatures and persisting columnar organisation at room temperature. A rare hexagonal mesophase with twelve columns per hexagonal unit cell is found in the metal-free homologue, whereas the metal complexes show rectangular mesophases. The clearing temperature increases with increasing axial component of the metal ion coordination sphere. At low temperature, significant antiferromagnetic exchange between magnetic centres is observed for the Co(II) homologue, whereas the magnetic centres are magnetically independent in the Cu(II) derivative, in line with the observed higher clearing temperature in the Co(II) case that testifies of stronger interdisk interactions.

High rectification in organic diodes based on liquid crystalline phthalocyanines

“…These rectification ratios are much higher than those reported for a less regularly substituted PC, a hexagonal columnar liquid crystalline zinc PC derivative with a considerably larger electronically inert alkyl periphery, 21 giving rectification ratios of less than 10:1 in a very similar device configuration with ITO/PEDOT:PSS and Ca/Al electrodes. The strong rectification might result from close and regular molecular packing in the well ordered plastic rectangular columnar mesophases present in the materials 1-3, 17 which provides intimate intermolecular π-orbital and metalnitrogen interactions and therewith an efficient charge transport through the PC columns even in planar alignment, and thus leads to efficient charge evacuation after injection, avoiding the build-up of a counter-field that would outplay the built-in rectifier geometry. A rectification of 3 orders of magnitude was also obtained for a perylene-based columnar LC in a diode…”

“…As reported previously, all three exhibit a plastic crystalline columnar mesophase of rectangular symmetry at room temperature that forms upon cooling (1: below 40 1C, 2: below 70 1C, and 3: below 45 1C) from a highertemperature LC mesophase of hexagonal (1) or rectangular (2, 3) symmetry, the transition enthalpies between the liquid crystalline and plastic crystalline states being barely noticeable by calorimetry. 17 1 and 3 can be obtained in a conventional crystalline state (with a strong melting enthalpy to the LC state of ca. 40 kJ mol À1 in both cases) by slow crystallization from a bad solvent, whereas in the case of 2, the plastic crystalline state is directly obtained by slow precipitation from solution.…”

“…16 We have recently reported that racemic 3-(2-butyloctyloxy)phthalonitrile can be tetramerized to a regiosymmetrically tetrasubstituted PC and its transition metal(II) complexes, where the four branched alkoxy substituents lead to the formation of columnar mesophases with moderate phase transition temperatures. 17 Here we present the electronic behavior in solution-processed organic diodes of the metal-free (H 2 -) and metalated (Cu-and Ni-) tetraalkoxy-PCs in order to correlate the optoelectronic properties with the molecular organization and film structure.…”

“…16 We have recently reported that racemic 3-(2-butyloctyloxy)phthalonitrile can be tetramerized to a regiosymmetrically tetrasubstituted PC and its transition metal(II) complexes, where the four branched alkoxy substituents lead to the formation of columnar mesophases with moderate phase transition temperatures. 17 Here we present the electronic behavior in solution-processed organic diodes of metal-free (H 2 -) and metalated (Cu-and Ni-) tetraalkoxy-PCs in order to correlate a Centre de Recherche Paul Pascal, Universite ´de Bordeaux & CNRS, 115 Avenue Schweitzer, 33600 Pessac, France b Departamento de Fı ´sica, Universidade Federal de Santa Catarina -UFSC, 88040-900 Floriano ´polis, SC, Brazil. E-mail: juh_19@yahoo.com.br, ivan.bechtold@ufsc.br; Fax: +55 48 37219946; Tel: +55 48 37212304 c Departamento de Fı ´sica, Universidade Federal de Ouro Preto -UFOP, 35400-000, Ouro Preto, MG, Brazil † Electronic supplementary information (ESI) available: Absorption spectra of H 2 PC and CuPC in solution and films, a comparison between the monoexponential fitting for H 2 PC in solution and bi-exponential fitting in spincoated films, fluorescence spectra of 1-3 excited at 636 nm in solution and thin films, AFM analysis of PCs 1 and 2 before annealing and after annealing for 2, and mobility of the PCs at the SCLC regime as a function of the applied voltage.…”

Octakis(dodecyl)phthalocyanines: Influence of Peripheral versus Non-Peripheral Substitution on Synthetic Routes, Spectroscopy and Electrochemical Behaviour

“…Electrochemical analysis of suitably soluble phthalocyanines, within the solvent window of dichloromethane, often reveal four of the six ring-based redox couples [ 8 ], although 17 of the possible 18 one-electron transfer processes of a cadmium triple decker phthalocyanine, Cd 2 Pc 3 , were observed in the solvent THF [ 9 ]. Phthalocyanines bearing four non-peripheral 2-butyloctyloxy sidechains have been shown to form condensed phases and exhibit liquid-crystal behaviour [ 10 ].…”