Naphthalene Triplet Research Articles

Deactivation Mechanism of Triplet Exciplexes between Benzophenone and Sensitized-Triplet Naphthalene Derivatives

Abstract The decay process of the triplet exciplexes formed between triplet naphthalene derivatives and benzophenone was found to be promoted by their charge transfer character since the rate constant of the nonradiative deactivation process increased with decreasing of the oxidation potentials of naphthalene derivatives.

Triplet-sensitized photobleaching of crystal violet

Crystal violet (CV +) and five related triarylmethane dyes quench triplet benzophenone ( 3K) in acetonitrile at diffusion-controlled rates ( k q ∼ 1 × 10 10 M −1 s −1). The interaction with CV + results in bleaching of CV + with a quantum yield, K Φ(−CV +), dependent on the concentration of CV + with a limiting value of 0.2 at high [CV +. Benzopinacol (K 2H 2) is also formed in this reaction but its yield decreases as [CV +] increases. In contrast, although both triplet anthracene ( 3An) and triplet naphthalene ( 3Nap) are also efficiently quenched by CV + at diffusion-controlled rates, there is only very inefficient fading, An Φ(−CV +) = 1.1 × 10 −5 . These results are interpreted in terms of a mechanism in which energy transfer to form triplet crystal violet, 3CV +, is the only major channel in the case of anthracene and naphthalene, i.e. 3CV + (like 1CV +) is unreactive. However, in the case of benzophenone, reduction of 3K by CV + with a rate constant k h = 1.4 × 10 9 M −1 s −1 to form ketyl radicals (KH .) can compete (about 14%) with this energy transfer. The ketyl radicals so formed can either reduce CV + to form leuco crystal violet (CVH) or form benzopinacol.

Dynamics of Probe Complexation to Bile Salt Aggregates

Excited triplet naphthalene and xanthone were employed as probe molecules to study the dynamics of incorporation into sodium cholate, taurocholate, and deoxycholate aggregates. The association and dissociation rate constants and the quenching rate constants for the incorporated probes were recovered from the dependence of the observed triplet decay rate constants on quencher concentrations (nitrite and cupric ions). Triplet naphthalene was incorporated into a site offering a high degree of protection from quenchers and from which dissociation was relatively slow. Triplet xanthone was incorporated into a less protected site from which dissociation was an order of magnitude faster than from the naphthalene site. We propose that naphthalene was incorporated into the hydrophobic site of primary aggregates, and xanthone was located in the region containing the hydroxyl groups in the secondary aggregates.

Excited Triplet State Interactions with Molecular Oxygen: Influence of Charge Transfer on the Bimolecular Quenching Rate Constants and the Yields of Singlet Oxygen [O*2(1.DELTA.g)] for Substituted Naphthalenes in Various Solvents

The bimolecular rate constants k T O2 for oxygen (O 2 ( 3 Σ g - )) quenching and the efficiencies f Δ T with which singlet oxygen (O 2 . ( 1 ΔS g )) is thereby produced are reported for a range of substituted naphthalene triplet states in acetonitrile, benzene, and cyclohexane. The magnitudes of k T O2 and f Δ T are inversely correlated, and both parameters exhibit pronounced sensitivity to the oxidation potential (E M OX ) of the naphthalene derivative and some dependence on the solvent

Synthesis and Adiabatic Photochemistry of a 1,4-Difluorobenzene – Naphthalene Biplanemer

Abstract A naphtalene-1,4-difluorobenzene biplanemer 1a has been prepared through the electrolytic oxidative didecarboxylation. The direct irradiation of 1a gave 1,4-difluorobenzene and excited naphthalene in both a singlet state (Φf = 0.098) and a triplet state (Φp = 0.029) at 77 K in EPA. In the triplet-sensitized reaction, the biplanemer 1a underwent intramolecular [2π+2π] cycloaddition to give a cage compound instead of the formation of the triplet naphthalene.

Intramolecular naphthalene triplet excimers in solutions of phosphazene copolymers

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIntramolecular naphthalene triplet excimers in solutions of phosphazene copolymersLucia Flamigni, Nadia Camaioni, Pietro Bortolus, Francesco Minto, and Mario GleriaCite this: J. Phys. Chem. 1991, 95, 2, 971–975Publication Date (Print):January 1, 1991Publication History Published online1 May 2002Published inissue 1 January 1991https://doi.org/10.1021/j100155a087RIGHTS & PERMISSIONSArticle Views119Altmetric-Citations10LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (576 KB) Get e-Alerts

Photochemical probe of the conformation of naphthalene triplet excimer: light-induced changes in the phosphorescence of Agosta pinacol dimer in rigid hydrocarbon glasses

The initial monomeric phosphorescence of Agosta pinacol dimer of naphthalene in hydrocarbon glasses at 77 K changes to an excimer-like phosphorescence of the corresponding diketone dimer upon irradiation. The close spectral resemblance between the diketone emission and the room-temperature excimer phosphorescence of naphthalene and 1,n-di-{alpha}-naphthylalkanes (n = 1-4) in fluid solutions provides compelling evidence for the stability of the naphthalene triplet excimer and enables us to address the question of its likely conformation.

A study of the triplet state of 7-amino coumarin laser dyes by the nanosecond pulse radiolysis technique

The triplet characteristics of two 7-amino coumarin laser dyes (7-diethylamino 4-methyl coumarin (C 1) and 7-diethylamino 4-trifluoromethyl coumarin (C 1F)) were studied in benzene solution using the nanosecond pulse radiolysis technique. Their T—T absorption spectra, rate constants for triplet to ground state transition and triplet—triplet annihilation and G values were determined. The energy transfers from coumarin triplets to various acceptor molecules such as pyrene, t-stilbene and anthracene and from benzene, biphenyl and naphthalene triplets to these dyes as acceptors were studied. Estimates of their energy levels were made.

Temperature, pressure and deuterium effects on the phosphorescence decay-rate constant of naphthalene in a single crystal of durene

It is suggested that the hitherto unexplained drastic temperature, pressure and external deuterium isotope effects on the phosphorescence decay-rate constant ( k T) of naphthalene in a single crystal of durene can be consistently explained in terms of the photoinduced hydrogen-abstraction reaction of triplet naphthalene from durene in which tunneling plays an essential role. This suggestion is supported by calculations based on the “golden rule” approach to tunneling developed by Siebrand, Wildman and Zgierski.

Molecular reaction kinetics inside channel pores: Delayed fluorescence of naphthalene in methanol

A one-dimensional, diffusion-controlled, reaction is followed in time by phosphorescence (monitoring reactant) and delayed fluorescence (monitoring product). The triplet (excited) naphthalene molecules move in a methanol solution, confined inside the cylindrical channels of a channel-pore polycarbonate membrane. The reaction product is a transient photodimer or excimer, giving delayed fluorescence. In large radius (1 μm) channel-pore membranes, the reaction kinetics are classical, with a heterogeneity exponent h=0. However, in the small radius (0.025 μm) channel-pore membranes the kinetics approach that of a one-dimensional environment, h= 1 2 . For membranes with intermediate channel radius (0.1 μm), the reaction exhibits a “cross-over” behavior which can be approximated via “fractal-like” kinetics.

Triplet state of coumarin 153 studied by nanosecond pulse radiolysis

The triplet—triplet absorption spectrum of the rigidized 7-amino coumarin dye C 153 has been investigatd in benzene solution in the region 450 – 750 nm by the pulse radiolysis technique. The triplet decay was first order with a half-life of 5 μs. Its formation was confirmed by energy transfer from the pulse radiolytically generated biphenyl triplet. The extinction coefficient of C 153 triplet in benzene was calculated to be 10 000 ± 500 dm 3 mol −1 cm −1. Using various triplet donors and acceptors its energy level was estimated to be 50 ± 2 kcal mol −1. The energy transfer rate constants from benzene, biphenyl and naphthalene triplets to C 153 and from C 153 triplet to anthracene were found to be diffusion controlled.

Evidence for non-radiative triplet-doublet energy transfer in the naphthalene-benzophenone system in tetrahydrofuran

Triplet-doublet energy transfer from the naphthalene triplet to the benzophenone ketyl radical has been studied in tetrahydrofuran at room temperature by measuring transient absorption and fluorescence spectra and decay profiles. The rate constant for the energy-transfer process has been determined to be 7 × 10 9 M −1 s −1 in tetrahydrofuran based on an analysis using a simple kinetic model.

The photophysics of some intramolecular ternary complexes formed between aryl and amino groups

The fluorescence properties of (3)–(6) in solvents of varying polarity have been examined and the conclusion reached that in non-polar solvents they exhibit fluorescence (low quantum yield) from an intramolecular ternary complex. In polar solvents very little fluorescence is observable. Although each compound exhibits extensive intramolecular fluorescence quenching, the quantum yield of localised triplet naphthalene in non-polar solvents remains relatively high indicating that intersystem crossing occurs in the non-relaxed exciplex.

Analog metal-to-nonmetal exciton transition: Effect of isotopic alloying on naphthalene triplet transport

A low-temperature investigation of the rate of triplet exciton transport within the guest (${\mathrm{C}}_{10}$${\mathrm{H}}_{8}$) quasilattice of the ${\mathrm{C}}_{10}$${\mathrm{D}}_{8}$-${\mathrm{C}}_{10}$${\mathrm{H}}_{8}$ crystal system has demonstrated a transition from bandlike to hoppinglike motion upon reduction of the guest-to-host concentration ratio. The analog metal and nonmetal regimes are characterized, respectively, by a negative and a positive transport temperature coefficient. In addition, reducing the naphthalene concentration by a factor of 5 reduces the transport rate by five orders of magnitude.

A solvent isotope effect upon exciplex photochemistry

For several naphthylalkylamines, change of solvent from methanol to deuterated methanol (CH 3OD) leads to an increase in quantum yield of intramolecular exciplex fluorescence, an increase in exciplex fluorescence lifetime and an increase in naphthalene triplet yield. The solvent effect is explained by the relative abilities of the two solvents to form hydrogen (deuterium) bonds and to protonate (deuterate).

Homofusion and heterofusion of triplet excitons in a ‘‘real’’ organic mixed crystal: Biphenyl host-naphthalene and pyrene guests system

The prompt and delayed emission spectra of a biphenyl host with naphthalene and pyrene both as guests mixed crystal have been studied. The fluorescence of naphthalene and pyrene and the excimer fluorescence of pyrene have been observed. The delayed emissions are observed from pyrene and naphthalene as delayed fluorescence of pyrene, phosphorescence of naphthalene, and pyrene. The investigations of excitation spectra of these emissions have shown to be very useful to understand the mechanism of delayed fluorescence generation. The heterogeneous defect-naphthalene and homogeneous naphthalene–naphthalene triplet–triplet annihilation are responsible for the production of delayed fluorescence of pyrene. The kinetic analyses from the decays and buildups have been made. The delayed luminescence decays at various temperatures have found to be nonexponential. However, in the long time region they are nearly exponential. Even in the long time region, the pyrene delayed fluorescence decays and buildups are nonexponential in the temperature range above 130 K. It has been established from the various Arrhenius plots that in this mixed crystal the temperature dependence of the phosphorescence lifetime is controlled by the thermal processes The kinetic scheme described satisfactorily explains the experimental results.

Electron transfer from the excited singlet and triplet states of aromatic hydrocarbons to methyl viologen

Evidence is presented that the excited singlet and triplet states of aromatic hydrocarbons are oxidised by methyl viologen (MV 2+). Rate constants for electron transfer from triplet naphthalene, anthracene, phenanthrene and fluoranthene are close to diffusion-controlled whereas those for triplet 1-cyanonaphthalene and 1-cyanoanthracene are about one order of magnitude lower.

Molecular dynamics and the phase transition in the naphthalene–tetracyanobenzene charge-transfer complex as studied by 1H NMR and triplet state EPR

1H NMR second moments and static and rotating frame relaxation time measurements were performed on the crystalline naphthalene–tetracyanobenzene charge-transfer complex between ∼50 and 150 K. The results are consistent with a model where the random jumping of naphthalene molecules between equivalent orientations becomes nonrandom below the phase transition at 72±1 K. Below the transition the two orientations must be inequivalent, with the molecules settling in the one of lower enery to yield a phase which ideally is completely ordered at 0 K. The barrier between the two orientations is 8.0 kJ/mol above Tc and 6.1 kJ/mol below Tc. The statistical average energy difference between the orientations increases with decreasing temperature from near zero at Tc and is 7.2 kJ/mol at 62 K. The EPR spectrum of the triplet naphthalene trap becomes weaker at higher temperature and disappears by 90 K. It shows no evidence of the phase transition. The loss of hfs at 55 K reveals a process, presumably thermal detrapping, which is 50 times faster than the naphthalene reorientation. Anthracene traps reorient some five times faster than naphthalene molecules at low temperatures but the two rates become comparable at higher temperatures. Naphthalene triplet excitons show processes only about four times as fast as the naphthalene reorientation. Evidently the triplet EPR spectra do not directly probe the molecular dynamics of the host lattice or the phase transition.

Calculations of g Tensors and Hyperfine Splitting Tensors for Molecules in Their Triplet States

Abstract The g tensors and hyperfine splitting (hfs) tensors of simple organic radicals in their triplet states have been calculated by using an all valence electron SCF MO method with a first order perturbation treatment. The molecular orbital spin density is partitioned into the σ- and π-electron spin delocalization (SD) terms and the rest terms of spin polarization (SP) which arise from the CI effect. The g tensors for CH2 and several other carbenes which have triplet ground states and for formaldehyde in its nπ* and nσ* excited triplet states are evaluated. The calculated α-proton hfs constants of CH2 contributing from the π orbital well compare with the observed hfs constants of the triplet naphthalene and the doublet malonic acid radical. The anisotropic carbon-13 hfs constants of CH2 are determined almost completely by the SD contribution and their absolute values are in good accord with those observed for CD2. Contribution of the SP terms to the isotropic hfs constant is found to be fairly large. Prediction of the hfs constants in CF2 and CHF is made.

ESR of triplet naphthalene pairs, evidence for non-resonance

ESR measurements on triplet naphthalene guest pairs in a host single crystal of perdeuterated naphthalene have been performed between 0.7 K and 4.2 K. Hyperfine splitting is partially resolved even at lowest temperatures, if the field H O is oriented along the principal pair axes. At arbitrary orientations however the width of the observed ESR line (M-line) decreases monotonically with increasing temperature, whereas its absolute value depends on crystal quality. The saturation of the ESR transitions at low temperatures produces a dip in the M-line. In order to explain the inhomogeneously broadened lines at lowest temperatures a model is developed in terms of the eigenstates of the hamiltonian of the pair including non-resonance between pair molecules of different excitation energies. We are able to correlate quantitatively the low temperature ESR line width with the width of the inhomogeneously broadened optical line which yields the distribution of guest energies within the crystal. The ESR line narrowing effect at higher temperatures is attributed to random phonon processes disturbing the coherence in the energy transfer.