Phosphorimetric analysis of phenothiazine derivatives

La, Gifford; Jn, Miller; Dl, Phillipps; Dt, Burns

doi:10.1021/ac60359a061

Cited by 22 publications

(8 citation statements)

References 29 publications

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“…A broad, structureless emission band centered at 620 nm was observed for the dyads, but not for the reference compound NI-Ph (Figure a). It is unlikely that this fluorescence is due to the PTZ moiety because it emits at wavelengths <500 nm . The NI moiety has an emission band centered at 378 nm .…”

Section: Resultsmentioning

confidence: 99%

Long-Lived Charge-Separated State in Naphthalimide–Phenothiazine Compact Electron Donor–Acceptor Dyads: Effect of Molecular Conformation Restriction and Solvent Polarity

Xiao,

Yan,

Sukhanov

et al. 2023

J. Phys. Chem. B

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To study the charge separation (CS) and long-lived CS state, we prepared a series of dyads based on naphthalimide (NI, electron acceptor) and phenothiazine (PTZ, electron donor), with an intervening phenyl linker attached on the N-position of both moieties. The purpose is to exploit the electron spin control effect to prolong the CS-state lifetime by formation of the 3CS state, instead of the ordinary 1CS state, the spin-correlated radical pair (SCRP), or the free ion pairs. The electronic coupling magnitude is tuned by conformational restriction exerted by the methyl groups on the phenyl linker. Differently from the previously reported NI-PTZ analogues containing long and flexible linkers, we observed a significant CS emission band centered at ca. 600 nm and thermally activated delayed fluorescence (TADF) with a lifetime of 13.8 ns (population ratio: 42%)/321.6 μs (56%). Nanosecond transient absorption spectroscopy indicates that in cyclohexane (CHX), only the 3NI* state was observed (lifetime τ = 274.7 μs), in acetonitrile (ACN), only the CS state was observed (τ = 1.4 μs), whereas in a solvent with intermediate polarity, such as toluene (TOL), both the 3NI* (shorter-lived) and the CS states were observed. Observation of the long-lived CS state in ACN, yet lack of TADF, confirms the spin-vibronic coupling theoretical model of TADF. Femtosecond transient absorption spectroscopy indicates that charge separation occurs in both nonpolar and polar solvents, with time constants ranging from less than 1 ps in ACN to ca. 60 ps in CHX. Time-resolved electron paramagnetic resonance (TREPR) spectra indicate the existence of the 3NI* and CS states for the dyads upon photoexcitation. The electron spin–spin dipole interaction magnitude of the radical anion and cation of the CS state is intermediate between that of a typical SCRP and a 3CS state, suggesting that the long CS-state lifetime is partially due to the electron spin control effect.

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Section: Resultsmentioning

confidence: 99%

Long-Lived Charge-Separated State in Naphthalimide–Phenothiazine Compact Electron Donor–Acceptor Dyads: Effect of Molecular Conformation Restriction and Solvent Polarity

Xiao,

Yan,

Sukhanov

et al. 2023

J. Phys. Chem. B

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“…The drugs studied were all the highest purity available from the following sources: chlorpromazine and trifluoperazine, Smith, Kline & French; thioridazine, Sandoz; fluphenazine, National Formulary; perphenazine, Schering. The structures of these drugs are available (13,15), as are the structures of the oxidation products (19). Stock solutions (5 mg/250 ml) were prepared in distilled water, with the exception of perphenazine, which was dissolved in 12.5 ml of ethanol and then diluted to volume with distilled water.…”

Section: Methodsmentioning

confidence: 99%

“…Methods based on the fluorescence of both the unoxidized or oxidized compounds have shown the most promise (8)(9)(10)(11)(12)(13)(14). A recently reported phosphorimetric method has detection limits of about 30 ppb for 14 different phenothiazines, but requires liquid nitrogen and instrumentation with ms response times (15).…”

mentioning

confidence: 99%

Rapid fluorimetric determination of phenothiazines employing in situ photochemical oxidation

White¹,

Frings²,

Villafranca³

et al. 1976

Anal. Chem.

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“…The T1 state of NI was determined as 2.25 eV (by phosphorescence method) [65], and the T1 state of PTZ unit was determined as 2.45 eV (phosphorescence method) [66].…”

Section: Electrochemistry Studymentioning

confidence: 99%

Tuning the photophysical property of naphthalimide-phenothiazine dyads by variation of the electron donating and accepting capability: synthesis and study of the intersystem crossing and thermally-activated delayed fluorescence

Cao¹,

Liu²,

Zhang³

et al. 2023

Preprint

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A series of naphthalimide (NI)-phenothiazine (PTZ) electron donor-acceptor dyads were prepared to study the thermally activated delayed fluorescence (TADF) property of the dyads, from a point of view of detection of the various transient species. The photophysical properties of the dyads were tuned by changing the electron donating and the electron withdrawal capability of the PTZ and NI moieties, respectively, by oxidation of the PTZ unit, or by using different arylamines to attach with the NI unit. This tuning effect was manifested in the UV-vis absorption and fluorescence emission spectra, e.g., the change of the charge transfer absorption bands. TADF was observed for the dyads containing native PTZ unit, and the prompt and delayed fluorescence lifetimes changed when different arylamine was used. In polar solvent, no TADF was observed. For the dyads with the PTZ unit oxidized, no TADF was observed as while. Femtosecond transient absorption spectra show that the charge separation takes ca. 0.6 ps, and admixture of locally excited (3LE) state and charge separated (1CS/3CS) states formed (in n-hexane). The subsequent charge recombination from the 1CS state takes ca. 7.92 ns. Upon oxidation of the PTZ unit, the beginning of charge separation is at 178 fs, and formation of 3LE state takes 4.53 ns. Nanosecond transient absorption (ns-TA) spectra show that both 3CS and 3LE states were observed for the dyads showing TADF, whereas only 3LE or 3CS state was observed for the systems lacking of TADF. This is a rare but unambiguous experimental evidence that the spin-vibronic coupling of 3CS/ 3LE states is crucial for TADF. Without the mediating effect of the 3LE state, no TADF is resulted, even the long-lived 3CS state is populated (lifetime τCS ≈ 140 ns). This experimental result confirms the 3CS → 1CS reverse intersystem crossing (rISC) is slow, without coupling with an approximate 3LE state. These studies are useful for in-depth understanding of the photophysical mechanisms of the TADF emitters, as well as for molecular structure design of new electron donor-acceptor TADF emitters.

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Phosphorimetric analysis of phenothiazine derivatives

Cited by 22 publications

References 29 publications

Long-Lived Charge-Separated State in Naphthalimide–Phenothiazine Compact Electron Donor–Acceptor Dyads: Effect of Molecular Conformation Restriction and Solvent Polarity

Long-Lived Charge-Separated State in Naphthalimide–Phenothiazine Compact Electron Donor–Acceptor Dyads: Effect of Molecular Conformation Restriction and Solvent Polarity

Rapid fluorimetric determination of phenothiazines employing in situ photochemical oxidation

Tuning the photophysical property of naphthalimide-phenothiazine dyads by variation of the electron donating and accepting capability: synthesis and study of the intersystem crossing and thermally-activated delayed fluorescence

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