ChemInform Abstract: EXCITED STATE BEHAVIOR OF AROMATIC AMINES IN SOLUTION, DIHYDROPHENAZINE DERIVATIVES

Abstract

Ahsorption.s,spektreii, sic,htbar und ultraviolett i Emissionsspektren i Lebenszeiten / QuanterialishruteM Absorption and emission spectra as well as emission quantum yields and lifetimes of 5,lO-dimethylphenazine (DMP), 5-methyl-10-pbenylphenazine, and 5,lO-diphenylphenazine were measured in 3-methylpentane at room temperature and 77' K. By means of relative polarization measurements in conjunction with CND0/2-CI calculations, the excited states were assigned. The long natural lifetime of the fluorescence (TP (DMP) -210 ns), together with the results of the calculation, reveals that the first transition is a symmetry forbidden 'A, --t 'A, transition in a C,, geometry bent along the N -N axis. This transition has an oscillator strength f'" -0.006 for all three compounds as determined from the fluorescence data. We propose that it acquires most of its intensity through a vibronic interaction with S,( 'B,) (Herzberg-Teller coupling). Since intersystem crossing between S,('A,) and T,('A,) is also orbitally forbidden, we suggest, in accordance with the phosphorescence polarization, an electronic spin-orbit coupling between S, and T,. Replacement of the methyl substituents by phenyl groups increases k,,, and enhances the temperature dependent behavior of this parameter. Non-radiative transitions occuring from the lowest triplet state account for nearly 40'%, of the absorbed quanta. Die Absorptions-und Emissionsspektren, die Quantenausbeuten und die Lebenszeiten von 5,lO-Diniethylphenazin (DMP), S-Methyl-10-Phenylphenazin und 5,lO-Diphenylphenazin wurden in 3-Methylpentan sowohl bei RT als auch bei 77 K geniessen. Die Zuordnung der Banden erfolgte anhand der relativen Polarisation in Verbindung mit CND0/2-CI-Berechnungen. Die lange naturliche Lebenszeit der Fluoreszenz ( T : (DMP) -210 ns) und die Recbenergebnisse deuten darauf hin, daR die erste Anregung des um die N-N-Achse gewinkelten Molekiils dem symmetrieverbotenen 'A, --t ' A,(C,,)-Ubergang zuzuordnen ist. Bei allen drei Verbindungen liegt die zugehorige Oszillatorstiirke f", bestimmt aus den Fluoreszenzdaten, in der GroDenordnung von 0,006. Wir nehmen an, daB diese Intensitat in der Hauptsache auf Schwingungswechselwirkungen mit S,( I B,) (Herzberg-Teller-Kopplung) zuruckzufuhren ist. In Anlehnung an die Phosphoreszenzpolarisation und aus dem Verbot des intersystem crossing zwischen S , ( 'A2) und T,(3A,) konnen wir als wahrscheinlich betrachten, daR die elektronische Spin-Bahn-Kopplung zwischen S, und T1 realisiert wird. Parallel zur Zahl der Phenylsubstituenten nimmt k,,, bzw. die Temperaturabhiingigkeit von k,,, zu. Die strablungslosen Uberginge aus dem tiefsten Triplettzustand belaufen sich auf ca. 40 "4 der absorbierten Lichtquanten. bd. 7X. Nr 13 I914

Tuning Electrochemical Stability of 5,10-Ditolylphenazine-Based Antiaromatic Materials for Unipolar Memristor toward Artificial Synapses Application

“…All molecules exhibit sharp π–π* absorptions at shorter wavelengths and broad and weak bathochromic absorptions at longer wavelengths. The low absorbance at longer wavelengths is originated from the partially forbidden S 0 –S 1 transition of the DTPZ unit, which has been reported in the previous literature . Comparing with Cz-DTPZ , DTA-DTPZ and DTA-me-DTPZ exhibit bathochromic absorption due to the stronger electron-donating character of p -ditolylamine than carbazole.…”

“…The low absorbance at longer wavelengths is originated from the partially forbidden S 0 −S 1 transition of the DTPZ unit, which has been reported in the previous literature. 32 Comparing with Cz-DTPZ, DTA-DTPZ and DTA-me-DTPZ exhibit bathochromic absorption due to the stronger electron-donating character of p-ditolylamine than carbazole. For Cz-DTPZ, several shoulder peaks exist around 300−350 nm, which are assigned to the n−π* transition of carbazole.…”

Tailor-Made Dynamic Fluorophores: Precise Structures Controlling the Photophysical Properties

“…15 However, there are also special cases of the L-L-type dihydrophenazine derivatives, such as 5,10-dihydro-5,10-dimethylphenazine (DMP), 5,10-dihydro-5-methyl-10-phenylphenazine (MPP), and 5,10-dihydro-5,10-diphenylphenazine (DPP), reported by Huber and co-workers in 1974 (Figure 1b). 16 These molecules exhibited a large Stokes shift between absorption and emission, which was attributed to the symmetrically forbidden S 0 −S 1 transition. This anomalous phenomenon was also observed in the A-L-type molecule, 9,14-dimethyl-9,14-dihydrodibenzo-[a,c]phenazine (DMAC), reported by Schuster.…”

“…Most L-L-type dihydrophenazine-based fluorophores show a normal Stokes shift emission, such as π-extended dihydrophenazines, including N , N ′-disubstituted dihydrodibenzo­[ b , i ]­phenazine , and dinaphtho­[2,3- b :2′,3′- i ]­dihydrophenazine . However, there are also special cases of the L-L-type dihydrophenazine derivatives, such as 5,10-dihydro-5,10-dimethylphenazine (DMP), 5,10-dihydro-5-methyl-10-phenylphenazine (MPP), and 5,10-dihydro-5,10-diphenylphenazine (DPP), reported by Huber and co-workers in 1974 (Figure b) . These molecules exhibited a large Stokes shift between absorption and emission, which was attributed to the symmetrically forbidden S 0 –S 1 transition.…”

Switching Singlet Exciton to Triplet for Efficient Pure Organic Room-Temperature Phosphorescence by Rational Molecular Design

“…The f was estimated according to the experimental data and listed in Table S1 (46). Interestingly, the f decreased from 0.0509 to 0.0011 with the variation of substituent position, indicating the S0→S1 transition evolved from a bright state to a dark state gradually.…”