Aggregation, Complexation with Guest Molecules, and Mesomorphism of Amphiphilic Phthalocyanines Having Four- or Eight Tri(ethylene oxide) Chains

Abstract

Zinc and metal-free amphiphilic phthalocyanines (pcs) substituted by four or eight tri(ethylene oxide) chains (3,6,9-trioxadecyloxy groups) {(H2(4EGpc), [Zn(4EGpc)], H2(8EGpc), and [Zn(8EGpc)] in Fig. 1)} have been prepared in order to study their aggregation in water, dioxane, and dioxane/water mixtures, their complexation phenomena with guest molecules in benzene, and mesomorphism in the neat state. In particular, tetra-substituted pcs have C4h symmetry and do not contain other positional isomers. [Zn(8EGpc)] forms aggregates in water and water–organic solvent mixtures; the extent of this was examined by electronic absorption and fluorescence spectroscopy. 1H NMR and fluorescence spectroscopy indicated that H2- and [Zn(8EGpc)] form inclusion complexes with quinones in benzene via hydrogen bonding. Benzoquinones with more hydroxy groups form complexes more effectively, plausibly laterally outside of the pc plane. From the higher field shift of the 1H singals of 2,2′-dihydroxy-1,1′-binaphthyl (BINAP) in the presence of [Zn(8EGpc)], BINAP molecules were suggested to lie above or below the pc plane. The mesomorphism of H2(8EGpc), [Zn(4EGpc)], and H2(4EGpc) was studied. In the case of H2(8EGpc), the discotic hexagonal ordered columnar (Dho) phase was seen in the range of from room temperature to 265 °C. However, liquid-crystalline phases were not observed for H2(4EGpc) and [Zn(4EGpc)].

Discotic liquid crystals of transition metal complexes: 28. Temperature-dependent electronic spectra and X-ray structural analysis of discotic liquid crystalline bis(octakisdodecyloxyphthalocyaninato)lutetium(III) complex

“…Very strangely, this D ro mesophase exhibits one more stacking distance h f at 3.48 Å , which is compatible with the face-to-face stacking distance of Pc macrocycles in the D ho mesophase. Although conventional columnar mesophases give only one stacking distance, it was recently reported that two or three stacking distances could be observed in one columnar mesophase [14,15]. These cases are attributable to an equilibrium of dimer monomer or trimer dimer monomer which contains three, two and one times the normal stacking distance h at the same time.…”

Synthesis, electrochemistry and in situ spectroelectrochemistry of water-soluble phthalocyanines

“…Water-soluble phthalocyanines are the most promising photosensitizers for PDT applications [6,7]. However, aggregation (especially in aqueous media) is a very common phenomenon in this family of compounds due to their large p-conjugated systems; this dramatically decreases their fluorescence quantum yields, shortens their triplet state life time and reduces their ability to be used as photosensitizers [8][9][10][11]. In photodynamic therapy, DMSO solutions of phthalocyanines have been also used, because DMSO, with the substance dissolved in it, is able to penetrate directly the tissues and cells, and that is the reason for extraordinary attention given to the absorption and emission properties of phthalocyanines in DMSO solutions [3,12].…”

Supramolecular Organization of $$\pi $$-Conjugated Oligomers

“…Roughly, two distinct kinds of studies can be discerned: (a) the doping of a pure liquid-crystalline donor phase with suitable acceptor dyes and (b) the preparation of mesophases from covalently or non-covalently assembled donor-acceptor complexes. Following the first strategy columnar mesophases of triphenylenes were doped with phthalocyanines [123][124][125][126][127], or 2,4,7-trinitrofluorenone [90,[128][129][130], for example. In these cases efficient quenching of the triphenylene emission was observed as a consequence of energy or charge transfer to the dyes.…”