Internal heavy atom effects in phenothiazinium dyes: enhancement of intersystem crossing via vibronic spin–orbit coupling

Rodriguez-Serrano, Angela; Rai-Constapel, Vidisha; Daza, Martha C.; Doerr, Markus; Marian, Christel M.

doi:10.1039/c5cp00194c

Cited by 59 publications

(52 citation statements)

References 44 publications

(72 reference statements)

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“…56 Recently, it was shown in several organic dyes that vibronic SOC with higherlying singlet/triplet excited states may also effectively enhance the ISC rates. 57 Computing all parameters on Eq. (5) rapidly becomes prohibitive for large molecules so that both semiquantitative 58 and qualitative 59 strategies are often used to rationalize the efficiency of ISC processes.…”

Section: A-2 Andmentioning

confidence: 99%

Controlling Triplet–Triplet Annihilation Upconversion by Tuning the PET in Aminomethyleneanthracene Derivatives

Zhao

Escudero

et al. 2015

J. Phys. Chem. C

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Activatable triplet-triplet annihilation upconversion was achieved using aminomethyleneanthracene derivatives. The molecular structures of the anthracene derivatives were varied by changing the number of phenyl substituents on the anthracene core (A-1, A-2 and A-3 containing no phenyl, one and two phenyl substituents, respectively). The structural modifications tune the intersystem crossing (ISC), the fluorescence as well as the distance between the electron donor (amino group) and the fluorophore by using methylene (A-1 and A-2) or a benzyl moiety (A-3) as a linker. Triplet-triplet annihilation upconversion is mainly tuned by photoinduced electron transfer (PET). Hence, the fluorescence of A-1 and A-2 can be switched on by protonation or acetylation of the amino group, whereas A-3 gives persistent strong fluorescence. Determination of the Gibbs free energy changes indicated significantly different PET driving forces for the three compounds. The mechanism of the fluorescence switching was studied with steady state UV−vis absorption, fluorescence emission spectroscopy, nanosecond transient absorption spectroscopy and ab initio computations. We found that the PET exerts different quenching effects on the singlet and triplet excited states of the anthracene derivatives.The triplet-triplet annihilation upconversion using these compounds as triplet acceptors/emitter was studied as well, and it was found that upconversion can be switched on by inhibition of the PET through acetylation and protonation.synthesis. Indeed, a large panel of triplet photosensitizers 16−19 and acceptors have been developed for TTA upconversion. 1−5,20 TTA upconversion has already been applied in various research field, e.g., luminescence bioimaging, 21 photocatalysis 22 and photovoltaics. 23−27 However, activatable, or switchable TTA upconversion was rarely studied. Indeed, recently we developed photoswitchable TTA upconversion using a photochromic unit, e.g., dithienylethene (DTE). 28−30 However, to the very best of our knowledge, chemically-activatable TTA upconversion was never demonstrated before. Clearly, external stimuli-addressable TTA upconversion adds additional flexibility for the application of TTA upconversion, such as in super resolution fluorescence microscopy, 31 and its development is a major improvement.In this framework, we report herein a new chemical-activatable TTA upconversion with aminoanthracene derivatives as triplet acceptor/emitter (A-1, A-2 and A-3, see Scheme 1). The fluorescence of these anthracene derivatives was quenched by the photo-induced electron transfer (PET) from the amino group to the anthracene core (A-1 and A-2), 32,33 and is also modulated via intersystem crossing (ISC). Our conclusions are supported by the negative Gibbs free energy changes (∆G 0 CS ) of the PET processes 34 and by computational investigations. Interruption of the PET by acetylation of the amino group of the triplet acceptor switches on the TTA upconversion.Interestingly, we found that the singlet excited state of the anthracene ...

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Section: A-2 Andmentioning

confidence: 99%

Controlling Triplet–Triplet Annihilation Upconversion by Tuning the PET in Aminomethyleneanthracene Derivatives

Zhao

Escudero

et al. 2015

J. Phys. Chem. C

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“…This is a remarkable characteristic of the QPTZ fragment, which results from the incorporation of the sulphur atom which enhances the ISC by vibronic spin-orbit coupling. [22] The transition of highest energy presents a maximum at 459 nm for SQPTZ-F and 454 nm for SQPTZ-TXO 2 giving respective triplet energy E T of 2.70 and 2.73 eV. QPTZ based compounds possess hence an E T of ca 2.7 eV, smaller than those of PA (3.08 eV for SPA-TXO 2 and 3.02 eV for SPA-F) and IA analogues (2.93 eV SIA-TXO 2 and 2.87 eV for SIA-F) indicating a different localization of the triplet exciton in IA, PA and QPTZ 4 based molecules.…”

mentioning

confidence: 99%

“…[17] This feature can be assigned to internal heavy atom effects as recently shown for phenothiazinium dyes and highlights the significant impact of the sulphur atom on the electronic properties of the QPTZ fragment. [22] Solvatochromic experiments allow a deeper understanding of the photophysical properties through the determination of the polarity of the excited states (Figure 3, bottom-right). Indeed, the emission maximum of SQPTZ-F in polar MeCN is recorded at 425 nm, being only very weakly shifted by 4 nm, compared to that in apolar cyclohexane (421 nm), in accordance with a transition occurring with only one fragment involved, namely QPTZ.…”

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confidence: 99%

9H‐Quinolino[3,2,1‐k]phenothiazine: A New Electron‐Rich Fragment for Organic Electronics

Poriel

Rault‐Berthelot

Thiery

et al. 2016

Chemistry A European J

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A new electron‐rich fragment, namely the quinolinophenothiazine (QPTZ) is reported. The QPTZ fragment incorporated in spiroconfigured materials leads to higher performance in blue Phosphorescent OLEDs than structurally related phenylacridine and indoloacridine based materials (increasing the HOMO energy level, modulating the spin‐orbit coupling, etc.) and leads to highly efficient blue phosphorescent organic light emitting diodes, indicating the strong potential of this new molecular fragment in organic electronics.

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“…The observed behavior suggests strong increasing of intersystem crossing rate constant due to a heavy atom effect (spin-orbital coupling) [13,14]. Depending on type of metal ions in the center of phthalocyanine macrocycle (e.g.…”

Section: Resultsmentioning

confidence: 99%

Photophysical Features of Phthalocyanines Metallocomplexes with Out-of-Plane Ligands

Старухин¹,

Gorski²,

Knyukshto³

et al. 2017

ujpa

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The objective of this work was synthesizing of Ti-, Zr-, Hf-phthalocyanines, containing chloride ions or dibenzoylmethanate fragments coordinated in out-of-plane positions to macrocycle. Spectroscopic and photophysical parameters of phthalocyanines metallocomplexes with metal atoms Ti(IV), Zr(IV) and Hf(IV) and spectroscopic features of Mg-and Zn-phthalocyanines have been detected and characterized at ambient and liquid nitrogen temperatures. The efficient intersystem crossing observed for Hf-phthalocyanine leads to very weak fluorescence and suppresses the fluorescence lifetimes to less than 1 ns. Changing of nature of central metals from heavy Hf(IV) atom to lighter atoms: Zr(IV), Zn(II), Ti(IV), Mg(II) lead to noticeable increasing of fluorescence lifetimes up to maximum value of 6,6 ns for Mg-phthalocyanine. At the same time the values of fluorescence quantum yield rises from 1 % for Hf-phthalocyanine to 56 % for Mg-phthalocyanine. The heavy atom effect has a substantially greater impact on photophysical parameters metallocomplexes of phthalocyanines than influence of attachment out-of-plane ligands.

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Internal heavy atom effects in phenothiazinium dyes: enhancement of intersystem crossing via vibronic spin–orbit coupling

Cited by 59 publications

References 44 publications

Controlling Triplet–Triplet Annihilation Upconversion by Tuning the PET in Aminomethyleneanthracene Derivatives

Controlling Triplet–Triplet Annihilation Upconversion by Tuning the PET in Aminomethyleneanthracene Derivatives

9H‐Quinolino[3,2,1‐k]phenothiazine: A New Electron‐Rich Fragment for Organic Electronics

Photophysical Features of Phthalocyanines Metallocomplexes with Out-of-Plane Ligands

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