Observation of a Fluorescent Dimer of a Sulfonated Phthalocyanine¶

Abstract

With very few exceptions, phthalocyanine dimers are found to be nonfluorescent. We report here the observation of a fluorescent dimer of a tetrasulfonated copper phthalocyanine in ethanol and water. Fluorescence excitation and emission spectra at room temperature and at 77 K are presented. These are consistent with the conventional model of exciton coupling in a cofacial dimer.

Bi-molecular emissive excited states in platinum (II) complexes for high-performance organic light-emitting diodes

“…2). We note that the excimer band position of the PL of neat films (as can be seen for PtL 26 Cl in Fig. 4) correlates well with that for the excimer band of its low polarity fluid solution (Fig.…”

“…3b. This could bring one to a supposition that the PtL 26 Cl dimers are indeed present in the solid film, though their low population and weak emission renders them blurred into the long-wavelength wing of the excimer emission centered at 620 nm. If D 1 and D 2 represented two absorption components of the dimer, it would indicate the oblique orientation of monomer transition dipoles composing the dimer with two dipole-allowed transitions.…”

“…The spectral shift of the dimer states relative to the monomer can be either to the blue or to the red region of the spectrum, depending on the relative magnitudes of the coulombic energy of interaction of the charge distribution on mono-molecular components in the ground and excited states, and on the orientation of the monomer transition moments. Also, it must be kept in mind that, among a distribution of dimer species, the majority be non-emissive and/or are constituents of non-emissive larger aggregates as for example in a sulfonated phthalocyanine [26]. One can speculate that varying the polarity of the environment of PtL x Cl would lead to a similar effect as sample softening due to increasing temperature of aromatic molecules-doped low-temperature glasses.…”

“…2b), suggesting the excimers to be formed in them within relatively small size environmental cages of similar rigidity. The characteristic for neat films of both compounds, PtL 26 Cl and FPt1, weakness of molecular exciton emission, does not have to be a rule. Its dominating occurrence may be expected in organic solids with large intermolecular separation distance (ca.…”

“…In this device, holes primarily traverse the HTL, with electrons transported across the TAZ electron transporting layer (ETL) [12]. Due to the high ionization potential of TAZ and thus its strong hole-blocking properties, excited states are formed on PtL 26 Fig. 4).…”