Electronic States and Relaxation Dynamics of Silicon Phthalocyanine Dimers

Abstract

Absorption and emission spectra of monomers and dimers of [tetramethoxytetrakis(octyloxy)phthalocyaninato]silicon have been measured as a function of solvent and concentration. In contrast to the monomer, the fluorescence of the dimer is shifted to lower energy by about 4000 cm -1 , and the emission quantum yield is reduced by a factor of 10 -3 . The spectroscopic data are analyzed in the strong coupling limit of dimer models and lead to an excitation exchange interaction term of 1770 cm -1 and an evaluation of the excited state lifetime of ca. 24 ps. This fast decay is dominated by nonradiative processes. The admixture of ion pair configurations is suggested to provide an efficient coupling to the environment and channel of decay of the exited state energy. Small contributions of such configurations to the ground state are also invoked to explain the marked changes in the absorption spectra as a function of environment (solvent) and concentration (aggregation).

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

“…The dimer would have a non-sandwich molecular configuration. The large splitting between these states 2b % 4032 cm À1 resembles that for silicon phthalocyanine dimers (2b % 3800 cm À1 ) [24] which agrees reasonably well with the values predicted by the strong coupling limit of neutral exciton model [25]. The $200 cm À1 excess of the present value may be due to the involvement of either CT resonance and/or to the difference of the polarization energy between the dimer and the two monomers, the latter being in general dependent on the state of the excitation of the molecule.…”

Absorption, luminescence, and Raman spectroscopic properties of thin films of benzo-annelated metal-free porphyrazines

“…A possible explanation could be the contributions to vibronic levels of the ground state, which could be weakly allowed. This was very recently suggested to interpret the dimer fluorescence in solution of a m-oxy silicon phthalocyanine [49]. On the other hand, Orti et al [64] calculated two allowed transitions for the NIR region of a Pc-H 2 dimer.…”

“…1 An exception is a very weak yet strongly red-shifted fluorescence reported for the m-oxo dimer of silicon phthalocyanine in solution [49,50]. 2 No reproducible luminescence signature could be obtained, possibly due to degradation of AnH 2 under the excitation conditions.…”

Optical Spectra of Phthalocyanines and Related Compounds

“…Highly solvatochromic behaviors have been reported for μ-oxo dimers of Si IV phthalocyanines but not for the corresponding monomers [227][228][229][230]. In aromatic solvents such as benzene or toluene, their optical absorption spectra show a sharp, single Q-band at approximately 640 nm, which is characteristic of μ-oxo dimers (see Sect.…”