Shpol'skii spectroscopy and vibrational analysis of [N]phenylenes

Abstract

Shpol'skii spectroscopy and vibrational analysis of [N]phenylenes U n i v e r s i t ä t P o t s d a mVibrationally resolved fluorescence spectra of four angular [N]phenylenes were recorded with laser excited Shpol 'skii spectroscopy (LESS) in an n-octane matrix at 10 K. In general, the same vibrational frequencies were observed in the fluorescence excitation and emission spectra, indicating that the geometries of ground and electronically excited state are very similar. Because of intensity borrowing from the S 2 state, vibrations of two different symmetries were observed in the fluorescence excitation spectra of angular [3]phenylene and zig-zag [5]phenylene. This finding allowed the location of the S 2 state for these compounds. DFT calculations (RB3LYP/6-31G*) of the ground state vibrational frequencies were made. The calculated vibrational modes were in reasonably good agreement with the experimental data. A new very low-frequency vibration of approximately 100 cm À1 was predicted and experimentally confirmed for all [N]phenylenes investigated. This vibration seems to be unique for [N]phenylenes and is attributed to an in-plane movement of the carbon backbone.

Deuteration effects on the vibronic structure of the fluorescence spectra and the internal conversion rates of triangular [4]phenylene

“…Therefore, only vibronic transitions which are induced by e'-modes are symmetry allowed. 36 As can be seen from Tab. 1, the experimental data are consistent with the calculated e'-modes within an error below 10 cm -1 for all three isotopomers.…”

Photoinduced electron transfer in [N]phenylenes

“…The unsubstituted [N]phenylenes (1) and (2) exhibit a reorganization energy λ of 0.7 eV, which is smaller than the usual values for classical PAH (1.1 -1.8 eV) [23]. As the internal reorganization energy λ is expected to be small for the A solution of 5,6-bis(trimethylsilylethynyl) angular [3]phenylene (149 mg, 0.36 mmol) and Bu 4 NF (1 ml of a 1.0 M solution in THF, 1.0 mmol) in degassed toluene (50 ml) was stirred at room temperature for 2 h. The reaction mixture was washed with degassed water (3 × 50 ml), dried over MgSO 4 and filtered into a 100 ml flask. To it was added CpCo(CO) 2 (100 μL, 0.78 mmol) and di(benzyl) acetylenedicarboxylate (2.31 g, 7.80 mmol), [26] and the mixture was transferred into a 50 ml syringe.…”

“…A solution of 5,6-bis(trimethylsilylethynyl) angular [3]phenylene (151 mg, 0.36 mmol) and Bu 4 NF (1 ml of a 1.0 M solution in THF, 1.0 mmol) in degassed toluene (50 ml) was permitted to stir at room temperature for 2 h. The reaction mixture was washed with degassed water (3 × 50 ml), dried over MgSO 4 , and filtered into a 100 ml flask. All these steps were…”

“…[N]phenylene molecules have been published in the last years [2][3][4]. The most remarkbale photophysical feature of [N]phenylenes is the striking effect of the annelation geometry on the This is caused by ultrafast IC with rates k IC exceeding 10 9 s -1 , due to major geometric distortions between S 0 and S 1 state.…”

“…Although the general synthetic procedure introduced by K. C. P. In order to elucidate the basic electron transfer properties of angular [N]phenylenes, the bimolecular quenching reactions of angular [3]-(1) and triangular [4]phenylene (2) ( Fig. 1) with various electron acceptors were studied by time-resolved fluorescence spectroscopy.…”