Self-Assembled Nanowire Networks of Aryloxy Zinc Phthalocyanines Based on Zn−O Coordination

Abstract

Tetrakis(aryloxy)phthalocyanine (4c) and its Zn congeners (4a and 4b) and Ni congener (4d) were synthesized, and their self-assembling properties in coordinating and non-coordinating solvents were investigated by absorption and fluorescence spectroscopy, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), and transmission electron microscopy (TEM). Compounds 4a and 4b in non-coordinating solvents exhibit red-shifted and split Q-bands in absorption spectra even at very low concentrations, suggesting J-aggregate formation. The MALDI-TOF MS for the samples of 4a and 4b prepared from chloroform solutions gives the monomer and aggregate signals. The TEM images of such samples display an indefinite two-dimensional network structure. The aggregates break up into monomers when a coordinating solvent is added to the solution. The driving force for the aggregate formation is proposed to be the complementary coordination of the ether oxygen in the aryloxy groups of one molecule to the core Zn of another molecule of phthalocyanine.

Novel azobenzene-phthalocyanine dyads――design of photo-modulated J-aggregation

“…One of the distinct spectroscopic properties of J-aggregations is a sharp excitonic absorption peak called the J-band, red-shifted from the monomer band [24] . As we have reported previously [7] , α-aryl/ alkoxy-substituted zinc Pcs could form J-aggregation through intermolecular Zn-O coordination in non-coordinating solvents such as chloroform and toluene. However, it did not work in coordinating solvents such as THF, DMF, and ethanol.…”

“…However, it did not work in coordinating solvents such as THF, DMF, and ethanol. It has already been reported that J-aggregation formed through Zn-O coordination could dissociate upon the addition of methanol [7] . Figure 2(a) shows the absorption spectra of 3-azoZnPc in THF and chloroform solutions.…”

“…Theoretically, if such interactions can be controlled by light, the aggregations may become light-controlled or light-triggered. Taking account of the aggregation mechanism of α-aryl/alkoxy-substituted zinc Pcs in non-coordinating solvents ( Figure 1) [7] , we concluded that the oxygen-linked substitution in the Pc rings would largely effect the formation of J-aggregation.…”

“…They found that the complementary coordination of imidazolyl group from one Pc to the central Zn 2+ or Mg 2+ ion in a second Pc molecule led to a "slipped co-facial dimmer". Only one year ago, our group [7,8] proved that α-aryl/alkoxy-substituted zinc Pcs could self-assemble to J-aggregation in non-coordinating solvents based on the coordination of central Zn 2+ of one Pc molecule with the peripheral oxygen atom of another Pc molecule.…”

Synthesis of Stable Dimeric Phthalocyanine J-Type Complexes and Investigation of Their Nucleophilic Properties

“…Thus, UV-Vis spectroscopy has demonstrated the transformation of the monomeric phthalocyanine complexes bearing four peripheral aryloxy substituents to the J-type aggregates upon addition of pyridine to the solutions in chloroform. [6] In the case of the monomeric complexes with only one peripheral polar substituent (e.g. low-symmetry phthalocyanines), instead of aggregates the dimers of similar structure are formed.…”