Magnetic Field Effects on Intramolecular Exciplex Fluorescence of Chain-Linked Phenanthrene and N,N-Dimethylaniline: Influence of Chain Length, Solvent, and Temperature

Abstract

Magnetic field effects (MFEs) on the intramolecular exciplex fluorescence of a chain-linked phenanthrene (Phen)/N,N-dimethylaniline (DMA) system, Phen–(CH2)n–O–(CH2)2–DMA, have been studied in the magnetic fields (≤0.62 T) as functions of (1) solvent polarity (ε = 7.6—36.7), (2) chain length (n = 4—12), and (3) temperature (223—333 K). The MFEs on the exciplex fluorescence are attributable to the singlet–triplet intersystem crossing in the intramolecular radical ion pair which is in dynamic equilibrium with the exciplex. (1) Solvent polarity increases significantly the MFEs on the exciplex fluorescence of Phen–(CH2)10–O–(CH2)2–DMA. This is attributable to the stability of the intramolecular radical ion pair relative to the exciplex. (2) A remarkable influence of chain length on MFEs in the exciplex fluorescence in N,N-dimethylformamide (DMF) was observed. The results were discussed in connection with the edge-to-edge distances <r> of two radicals obtained from molecular dynamics calculation for model compounds. (3) The temperature-induced high-field shift of the exchange energies |2J| for Phen–(CH2)4–O–(CH2)2–DMA in DMF was discussed in connection with <r>.

Spin effects in intramolecular electron transfer in naproxen-N-methylpyrrolidine dyad

“…The observation of the MFE in exciplex fluorescence in both the chain-linked phenanthrenedimethylaniline dyad and the supramolecular complex of zinc(II)-tetraphenylporphyrin with viologen, described by Japanese researchers [39], was also assigned to the fast equilibrium between RIP and exciplex.…”

Spin Chemistry Investigation of Peculiarities of Photoinduced Electron Transfer in Donor–Acceptor Linked System

“…The authors suggested that the presence of the radical cation in nonpolar solvents is due to fast, comparable with lifetime of RIP, transitions between solvent separated and contact RIP (exciplex). The observation of MFE on exciplex fluorescence in chain linked phenanthrene-dimethylaniline dyad and in supramolecular complex of zinc(II)-tetraphenylporphyrin with viologen, which was described by Japanese researchers [33], was also explained by the existence of fast equilibrium between RIP and exciplex.…”

2‐Phenanthrenyl–DNA: Synthesis, Pairing, and Fluorescence Properties

“…[51] Furthermore, it has been shown that phenanthrene efficiently forms exciplexes with aromatic amines, in particular with N,N-dimethylaniline. [52] Given that exciplex emission normally occurs at wavelengths higher than that of the emission of the isolated constituents, we assume again that no exciplex is formed in the 3phenH/3phenNH 2 duplex, although we cannot completely rule it out. The mechanistically mostplausible explanation for the observed fluorescence behavior therefore involves charge transfer.…”