Electronic Structures of 9,10-Anthrylene Dimers and Trimers in Solution:  Formation of Charge Separation States Depending on Alkyl Substituent Groups

Abstract

Electronic structures of 9,10-anthrylene dimers and trimers analogous to 9,9‘-bianthryl (BA) have been investigated by means of steady-state fluorescence and transient absorption spectroscopy and dipole moment evaluation based on the solvatochromic fluorescence shifts and integrated electrooptical emission measurements (IEOEM) in various solvents. Formation of the charge-separation (CS) state in the excited state was strongly dependent on the substituent group: unsubstituted and n-hexyl-substituted anthrylenes exhibited almost the same behavior compared to BA, whereas the tert-butyl-substituted dimer and trimer relaxed into an excitonic state rather than the CS state even in a polar solvent. The lower possibility of the CS state for the tert-butyl-substituted anthrylenes was mainly ascribed to the smaller solvation energy because of the larger effective Onsager cavity due to bulky tert-butyl groups. The limitation of a simple continuum model using Onsager's reaction field was also discussed in relation to the solvent-induced electronic structure change in the excited state of anthrylenes.

Solvent Effects on Electronic Structures of Coumarin 153: Parallel Studies by Means of Spectroscopy and RISM-SCF Calculations

“…2, the plots for benzene estimated either by experiment or theory seem to have larger value as could be suggested by the data in polar solvents. Such departure has been experimentally detected in aromatic systems, 3) that has been understood in terms of specific π -π interactions among solute and solvent molecules. On the contrary, RISM-SCF theory we use in this work does not comprise π -π interactions in an explicit formalism.…”

“…As these spectra exhibit asymmetry, we employ the first moment of the spectral function to be applied to eq. (2), which is defined as (3) where X = a or f expresses the same meaning as given in eq. (1), and f(·) is the spectral function with the frequency ν.…”

“…To be precise, the experimental observable, the Stokes shift Δ ν = ν a -ν f , is plotted versus a function f ε -f n , and Δµ is calculated under an assumption of the parameter a 0 . In particular, the Mataga-Lippert equation has been applied to assess electronic structures of charge-transfer complexes, 6) twisted intramolecular charge-transfer (TICT) compounds, 3,7) for example. However, molecular-dependent behavior of the Stokes shift arising from specific solute -solvent interactions has been kept veiled.…”

Solvent dependence of Stokes shift for organic solute–solvent systems: A comparative study by spectroscopy and reference interaction-site model–self-consistent-field theory

“…(2) correlates solvatochromism of absorption or fluorescence spectra and the solvent reorganization because of its nuclear polarization. By virtue of the straightforward analysis of experimental observables, this theory has been applied to a range of systems, such as solvatochromic dyes 9 and twisted intramolecular charge-transfer molecules, [10][11][12] in particular in the field of organic photochemistry. The basic idea of the theory has yielded detailed descriptions of solvation energies in relation to solute photoexcited states, such as electron-transfer reactions in solution.…”

“…14 Another empirical aspect of Mataga-Lippert theory is that in some organic solvents, such as aromatics and 1,4dioxane, one observes larger Stokes shift magnitudes than predicted from their f εf n parameters. 11,12,15 Reynolds and co-workers have applied spectroscopy and extensive ab initio calculations to address this phenomenon with respect to solvents that they refer to as "nondipolar," such as benzene and dioxane. 15 They have also noted that short-range solute-solvent interactions are important in nonpolar solvents.…”