Effects of solvent induced modulation of energy gaps on electronic relaxation of excited hydrogen bonded complexes of some aromatic carbonyl compounds

Burgt, M.J. van der; Jansen, Lisinka; Huizer, A. Herbert; Varma, Cyril A. G. O.

doi:10.1016/0301-0104(95)00306-1

Cited by 18 publications

(8 citation statements)

References 28 publications

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“…As mentioned earlier, we assert that three ISC channels exist: one is a temperature-independent S 1 → T 1 process, and the others are temperature-dependent S 1 → T n processes ( n = 2, 3) with activation energies of E ISC (2) ≈ 40 and E ISC (3) ≈ 170 meV (see the fitted values shown in Figure a). Similar multiple ISC pathways, consisting of temperature-independent and -dependent pathways, have also been reported in some transition metal complexes, , aromatic compounds, − and chlorophyll binding proteins …”

Section: Discussionsupporting

confidence: 70%

Multiple Intersystem Crossing Processes in Ge-Doped Silica Glass: Emission Mechanism of 2-Fold Coordinated Ge atoms

2018

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It has been well documented that ∼5 eV optical excitation of a 2-fold coordinated Ge atom in Ge-doped silica glass results in a singlet–singlet emission at ∼4.2 eV and a triplet–singlet emission at ∼3.1 eV, which are connected by thermally activated intersystem crossing (ISC). However, the true mechanism of the ISC, whose rate shows an apparent non-Arrhenius temperature dependence, has not been well understood and appreciated. In this work, we perform detailed photoluminescence measurements on highly luminescent Ge-doped silica glass with an internal quantum yield of ∼40% in a wide temperature range from 3 to 500 K. It has been found that there exists at least three triplet excited states of the 2-fold coordinated Ge atom, contributing respectively to three different ISC channels. One is a temperature-independent ISC process, and the others are temperature-dependent processes with activation energies of ∼40 and ∼170 meV. We have also found that nonradiative transitions, which have often been neglected in previous studies, need to be considered for a full description of the entire set of emission characteristics. Our conclusion is that the non-Arrhenius characteristics of the ISC rate are not due to a wide and continuous distribution of activation energies of the ISC process, as is often proposed, but instead results from multiple ISC pathways consisting of higher order triplet states.

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Section: Discussionsupporting

confidence: 70%

Multiple Intersystem Crossing Processes in Ge-Doped Silica Glass: Emission Mechanism of 2-Fold Coordinated Ge atoms

2018

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“…First we consider the electronic properties of simplified analogues, methyl 2-naphthoate (2MN), 2-acetonaphthone (2AN), and 2-naphthaldehyde (2NA). The properties of the excited singlet and triplet states of all these compounds are known to depend strongly on solute-solvent interactions. , When 2AN or 2NA is dissolved in an alkane, the S 1 state is an (n,π*) state, and no fluorescence is observed. However, in alcohols or water 2AN and 2NA exhibit strong fluorescence, because the energy of the S 2 (π,π*) state is lowered by hydrogen bonding than that of the lowest 1 (n,π*) state.…”

Section: Resultsmentioning

confidence: 99%

Effects of Electronic Structures on the Excited-State Intramolecular Proton Transfer of 1-Hydroxy-2-acetonaphthone and Related Compounds

et al. 1998

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Effects of electronic structures on the excited-state intramolecular proton transfer (ESIPT) of 1-hydroxy-2-acetonaphthone (1H2AN) and its related compounds [1-hydroxy-2-naphthaldehyde (1H2NA) and methyl 1-hydroxy-2-naphthoate (1H2MN)] were studied by means of the laser photolysis method, time-resolved thermal lensing technique, and fluorometry. Both 1H2AN and 1H2NA showed relatively large Stokes-shifted fluorescence (Δν̄ = 6120 and 6170 cm-1, respectively) and strongly temperature-dependent fluorescence observed usually for ESIPT systems. In contrast, the fluorescence properties of 1H2MN gave no indication of the occurrence of ESIPT. A 355 nm laser photolysis of 1H2AN or 1H2NA in cyclohexane produced a ground-state transient. The decay rate of the transient was markedly enhanced by addition of alcohols or triethylamine in nonpolar aprotic solvents. Furthermore, a bimolecular decay process probably due to mutual hydrogen exchange in a hydrogen-bonded complex was found for the transient from laser intensity dependence of the decay profiles. These observations could be reasonably explained by the occurrence of ESIPT in 1H2AN and 1H2NA to form a long-lived keto-tautomer. The distinct relaxation properties of excited 1H2AN and 1H2NA from that of 1H2MN were attributable to differences in relative stabilities between parent enol- and tautomeric keto-forms in the lowest excited singlet state, which are strongly affected by the electronic effects of the substituent on the carbonyl group.

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“…Hydrogen bonding and solvent polarity are the key factors in controlling pathways of energy dissipation following electronic excitation. , Solvent-moderated shifts of the energy levels may enhance or inhibit radiationless transitions to the ground state via the “proximity effect” . Hydrogen bond formation has a different effect on the energies of various excited states; in an extreme case, hydrogen bonding may cause the reversal of close lying n, π* and π, π*states …”

Section: Introductionmentioning

confidence: 99%

Tunable Solvatochromic Response of Newly Synthesized Antioxidative Naphthalimide Derivatives: Intramolecular Charge Transfer Associated with Hydrogen Bonding Effect

et al. 2011

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The solvatochromic behavior of two newly synthesized naphthalimide derivatives (I and II) which have potential antioxidative activities in anticarcinogenic drug development treatment, has been monitored in protic and aprotic solvents of different polarity applying steady-state and time-resolved fluorescence techniques. The compounds exhibit unique photophysical response in different solvent environments. The spectral trends do not appear to originate only from changes in the solvent polarity but also indicate that hydrogen bonding interactions and intramolecular charge transfer (ICT) influence the energy of electronic excitation of the compounds. Incorporation of an amino group at C(4) position of the naphthalimide ring in II makes it behave differently from I in terms of spectral characterization and fluorescence efficacy of the systems. The nonradiative relaxation process of the compounds is governed by medium polarity. The ground state geometry, lowest energy transition, and the UV-vis absorption energy of the compounds were studied using density functional theory (DFT) and time-dependent density functional theory (TDDFT) at the B3LYP/6-31G* level, which showed that the calculated outcomes were in good agreement with experimental data.

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Effects of solvent induced modulation of energy gaps on electronic relaxation of excited hydrogen bonded complexes of some aromatic carbonyl compounds

Cited by 18 publications

References 28 publications

Multiple Intersystem Crossing Processes in Ge-Doped Silica Glass: Emission Mechanism of 2-Fold Coordinated Ge atoms

Multiple Intersystem Crossing Processes in Ge-Doped Silica Glass: Emission Mechanism of 2-Fold Coordinated Ge atoms

Effects of Electronic Structures on the Excited-State Intramolecular Proton Transfer of 1-Hydroxy-2-acetonaphthone and Related Compounds

Tunable Solvatochromic Response of Newly Synthesized Antioxidative Naphthalimide Derivatives: Intramolecular Charge Transfer Associated with Hydrogen Bonding Effect

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