Intramolecular Electronic Energy Transfer Research Articles

Intramolecular Electronic Energy Transfer in a Supersonic Jet Expansion

AbstractIntramolecular electronic energy transfer (intra‐EET) was investigated in an isolated bichromophoric naphthalene (N) and anthracene (A) 1:1 molecular cluster. Investigation of the spectroscopic properties of these chromophores, separately and loosely bound in a van der Waals complex, helps to understand the dependence of the EET rate on the initially excited vibronic level and on the cluster's interchromophoric orientation.Measurement of fluorescence excitation spectra of anthracene, at different anthracene pressures shows bands that can be assigned to dimers of anthracene. From measurement of the anthracene excitation spectrum at increasing naphthalene pressures one can identify other spectral features, characterized by different spectral shifts from excitations of the bare molecule. Some transitions are probably due to a 13.5 cm−1 progression associated with an interchromophore cluster bond. Pressure dependence of fluorescence intensity gives evidence for 1:1 cluster composition, and for a slow intra‐EET rate that is associated with an unfavoured orientation of the two chromophores in one of the two possible conformers of the A‐N cluster, as supported by a calculation of the cluster geometry and by comparison with a recent study of intra‐EET in the A‐(CH2)n‐N bichromophoric molecules.

Novel aspects of intramolecular electronic energy transfer

Intramolecular electronic energy transfer (intra-EET) was investigated in an isolated bichromophoric naphthalene (N) and anthracene (A) 1:1 molecular cluster. Investigation of the spectroscopic properties of these chromophores, separately and loosely bound in a van der Waals complex, helps to understand the dependence of the EET rate on the initially excited vibronic level and on the cluster’s interchromophoric orientation. A slow intra-EET rate that is associated with an unfavoured orientation of the two chromophores in one of the two possible conformers of the A-N cluster, was observed and was supported by a calculation of the cluster geometry and by comparison with a recent study of intra-EET in the A-(CH2)n-N bichromophoric molecules.

Photophysics of the naphthalene—anthracene bichromophoric molecular system in a supersonic jet expansion

Intramolecular electronic energy transfer (intra-EET) was investigated in an isolated bichromophoric naphthalene (N) and anthracene (A) 1:1 molecular cluster. Investigation of the spectroscopic properties of these chromophores, separately and loosely bound in a van der Waals complex, helps to understand the dependence of the EET rate on the initially excited vibronic level and on the cluster's interchromophoric orientation. Measurement of fluorescence excitation spectra of anthracene, at different anthracene pressures shows bands that can be assigned to dimers of anthracene. From measurement of the anthracene excitation spectrum at increasing naphthalene pressures one can identify other spectral features, characterized by different spectral shifts from excitations of the bare molecule. Some transitions are probably due to a 13.5 cm −1 progression associated with an interchromophore cluster bond. Pressure dependence of fluorescence intensity gives evidence for 1:1 cluster composition, and for a slow intra-EET rate that is associated with an unfavoured orientation of the two chromophores in one of the two possible conformers of the A–N cluster, as supported by a calculation of the cluster geometry and by comparison with a recent study of intra-EET in the A-(CH 2) n -N bichromophoric molecules.

Intramolecular Electronic Energy Transfer in Ruthenium(II) Diimine Donor/Pyrene Acceptor Complexes Linked by a Single C−C Bond

The photophysical behavior of [(bpy)2Ru(L)]2+ complexes (L = 4-(1‘‘-pyrenyl)-2,2‘-bipyridine, bpy-pyr; 2-(1‘-pyrenyl)-1,10-phenanthroline, phen-pyr; and 2-(2‘-naphthyl)-1,10-phenanthroline, phen-nap) was investigated in solutions and frozen matrices. The conformation of the linked pyrene differs in the two complexes: The pyrene moiety is conformationally constrained to be nearly perpendicular to the phenanthroline in the phen-pyr complex while the pyrene in the bpy-pyr complex has much greater flexibility about the C−C bond linking the ligand and the pyrene. The 3MLCT excited state of the Ru(II) diimine complex and the 3(π → π*) state of the pyrenyl substituent are nearly isoenergetic; the 3MLCT state is the lowest energy state in the bpy-pyr complex, and the pyrene 3(π → π*) state is lower in energy for the phen-pyr complex. The bpy-pyr complex is unique in that the 3MLCT state has a very long lived luminescence (approximately 50 μs in degassed CH3CN). Luminescence decays for both pyrene containing complexes can be fit as double exponentials, indicating that the 3MLCT and 3(π → π*) states are not in equilibrium. Analysis of decays obtained at several temperatures reveal that energy transfer is slower than relaxation of the 3MLCT state but more rapid than decay of the pyrene localized 3(π → π*) state. The results also suggest that electronic coupling between the two states is weak despite the fact that the two chromophores are separated by a single covalent bond.

Discrete Intensity Jumps and Intramolecular Electronic Energy Transfer in the Spectroscopy of Single Conjugated Polymer Molecules

Single - molecule fluorescence spectroscopy of a multichromophoric conjugated polymer (molecular weight ∼20,000) revealed surprising single-step photobleaching kinetics and acute jumps in fluorescence intensity. These jumps were shown not to result from spectral diffusion and were attributed to fluctuations in the quantum yield of emission for the molecules. The data indicate efficient intramolecular electronic energy transfer along the polymer chain to a localized fluorescence-quenching polymer defect. The defects are created by reversible photochemistry of the polymer. These findings have implications for the use of conjugated polymers in light-emitting diode displays and sensors.

Elastic scattering of Sm in collision with He, Ne, Ar, Kr and Xe and relative cross-sections for intramolecular electronic energy transfer in SmO

Using the molecular beam chemiluminescence technique for the reaction of samarium with N 2O, the averaged elastic scattering crosssection of samarium with different closed-shell inert gases is measured and the relative probability for the collision-assisted intramolecular energy transfer (CAIMET) from metastable to radiative SmO states has been estimated. The relative CAIMET probability represents a gross average value for undefined metastable states to radiative states of SmO.

Gateway coupling between quartet and doublet states of 15N 18O studied in molecular beams

Collision-induced intramolecular electronic energy transfer in NO was studied using a beam of metastable 15N 18O(a 4Π) molecules colliding with Ar atoms in a cell. As in our earlier work on 14N 16O and 15N 16O, selective excitation of certain NO(B 2Π) levels was observed by means of their β-band emission. In the B, ν = 2 level three emitting levels could be uniquely identified in terms of rotational, fine structure and Λ component quantum numbers. They are gateway-coupled to likewise fully characterized b-state levels, which are collisionally populated from the a state. Weaker and less specific emission from the B, ν = 3 level was also observed, but not rotationally assigned.

Intramolecular Electronic Energy Transfer in the Naphthalene—Anthracene Bichromophoric Molecular Complex in a Supersonic Jet Expansion

AbstractIntramolecular electronic energy transfer (intra‐EET) was investigated in an isolated bichromophoric naphthalene (N) and anthracene (A) 1:1 molecular cluster. Investigation of the spectroscopic properties of these chromophores, separately and loosely bound in a van der Waals complex, helps to understand the dependence of the EET rate on the initially excited vibronic level and on the cluster's interchromophoric orientation.Measurement of fluorescence excitation spectra of anthracene at different anthracene pressures shows bands that can be assigned to dimers of anthracene. From measurement of the anthracene excitation spectrum at increasing naphthalene pressures one can identify other spectral features, characterized by different spectral shifts from excitations of the bare molecule. Some transitions are probably due to a 13.5‐cnr−1 progression associated with an interchromophore cluster bond. Pressure dependence of fluorescence intensity gives evidence for 1:1 cluster composition, and for a slow intra‐EET rate that is associated with an unfavored orientation of the two chromophores in one of the two possible conformers of the A‐N cluster, as supported by a calculation of the cluster geometry and by comparison with a recent study of intra‐EET in the A–(CH2)n‐N bichromophoric molecules.

Electronic energy transfer in supersonic jet expanded naphthalene-(CH 2) n-anthracene bichromophoric molecules

A study of intramolecular electronic energy transfer (Intra-EET) has provided evidence, for the first time, of a dramatic difference in Intra-EET efficiency results obtained under jet cooled and room temperature solution conditions. This was observed with anthracene-(CH 2) n -naphthalene bichromophoric molecules, A1N ( n = 1) and A3N ( n = 3). The rich fluorescence excitation spectrum of the naphthalene moiety in A1N indicates an inefficient EET process whose rate constant is substantially slower than that of the naphthalene moiety fluorescence. It was shown that the EET rate depends on a specific vibronic excitation that affects the molecular conformation, and was found to be at least two orders of magnitude slower in A1N molecule compared to A3N.

Solvent effects on competitive intramolecular electron transfer and energy transfer in a covalently linked porphyrin‐phthalocyanine heterodimer

AbstractPhotophysical properties of a porphyrin‐phthalocyanine heterodimer covalently linked with a dipentoxy chain have been studied. Absorption spectra show that there is weak exciton coupling between the two chromophores in the ground state. Fluorescence spectra show that intramolecular energy transfer from porphyrin to phthalocyanine moiety occurs in competition with electron transfer. The efficiency of these two processes depends upon the mutual orientation of the two chromophores. The effect of solvent polarity on the intramolecular processes is also discussed.

Dependence of the intramolecular electronic energy transfer in bichromophoric molecules on the interchromophore bridge

Results are presented on the intramolecular electronic energy transfer (intra-EET) in bichromophoric molecules of the type benzene-α-diketone, in which the interchromophore bridge contains methyl substituents β to the α-dicarbonyl acceptor chromophore. These results show that singlet-singlet intra-EET is independent of substitution and can be explained by a model assuming Dexter-type short-range exchange interaction. For singlet-triplet and triplet-triplet transfer, there are indications that the phosphorescence yield of the acceptor is larger than that for non-substituted bichromophoric molecules. This can be explained by through-bond inteaction promoting EET via a long-range superexchange mechanism, by variations in the non-radiative decay of the triplet state of the acceptor or by chemical reaction.

Intramolecular Exchange Energy Transfer in a Bridged Bimetallic Transition Metal Complex: Calculation of Rate Constants Using Emission Spectral Fitting Parameters

The photophysical behavior of the transition metal complexes {[(bpy)2Ru]2(bphb)}(PF6)4, {[(tpy)(CN)Ru]2(bphb)}(PF6)2, and [(bpy)2Ru(bphb)Ru(tpy)(CN)](PF6)4 (bpy = 2,2‘-bipyridine, tpy = 2,2‘,6‘,2‘‘-terpyridine, bphb = 1,4-bis(2,2‘-bipyrid-4-yl)benzene) was investigated in acetonitrile solution and low-temperature glasses. Luminescence spectra, excitation spectra, and transient absorption decays of the three complexes serve to show that intramolecular electronic energy transfer from the MLCT excited state of the [(bpy)2Ru(bphb) chromophore to the MLCT state of the tpy-containing chromophore occurs in the unsymmetric bimetallic complex. Nearly complete energy transfer from the [(bpy)2Ru(bphb)] chromophore to the tpy-containing chromophore was observed even in 4:1 ethanol:methanol glasses at 20 K. A semiclassical exchange energy transfer mechanism was used to treat the available data; the Franck−Condon weighted density of states (FCWD) was obtained using parameters determined from fits of luminescence spectr...

Photophysics and Mechanisms of Intramolecular Electronic Energy Transfer in Bichromophoric Molecular Systems: Solution and Supersonic Jet Studies.

Photophysics and Mechanisms of Intramolecular Electronic Energy Transfer in Bichromophoric Molecular Systems: Solution and Supersonic Jet Studies.

Intramolecular electronic energy transfer in peptides carrying naphthalene and protoporphyrin molecules: A spectroscopic and conformational statistics investigation

Short linear peptides, carrying an AA spacer in the backbone chain (AA = Aib or Ala), and naphthalene (N) and protoporphyrin IX (P) covalently bound to epsilon-amino groups of lysine side chains, were synthesized. The general formula is Boc-Leu-Leu-Lys(P)-(AA)n-Leu-Leu-Lys(N)-OtBu, with n = 0-2. The photophysical behavior of these compounds was investigated in water/methanol 75/25 (v/v) solution by steady-state and time-resolved fluorescence experiments. Quenching of excited naphthyl chromophore takes place by electronic energy transfer to the porphyrin ground state, and proceeds on a time scale of 3-8 ns, while a minor and slower (approximately 45 ns) fluorescence lifetime measures the decay of the exciplexes. The results were compared with those earlier obtained with the P(Ala)nN peptides (n = 0-4) in methanol solution, showing that addition of water does not significantly alter the dynamic relaxation behavior of the systems investigated, but affects the dissipation mechanism of the energy transferred to P. Quenching efficiencies from both fluorescence intensity and fluorescence lifetime measurements follow a different trend as the number of AA units increases, depending on whether AA = Aib or Ala, indicating that there are differences in the structural features of the two series of peptides. Consistently, CD spectral results suggest that the former compounds attain ordered conformations, possibly of the 3(10)-helical type, while the latter populate alpha-helical structures to an extent depending on the chain length. The ir data in dilute CD3OD or CDCl3 solution confirm this conclusion in that there is an increased percentage of intramolecular H bonds in the P(Aib)nN as compared to the corresponding P(Ala)nN peptides. The photophysical results can be well described by a long-range dipole-dipole interaction model, provided the separation distances distribution and mutual orientation of N and P groups are taken into account. The need of using the angular relationships between the probes implies that interconversion among conformational substates of chromophores linkages is slow on the time scale of the transfer process, very likely because of both the amide bond in the linkages and the bulkiness of the donor-acceptor pair.

Polarized fluorescence and absorption spectroscopy of 1,32-dihydroxy-dotriacontane-bis-rhodamine 101 ester. A new and lipid bilayer-spanning probe

We report on the properties of 1,32-dihydroxy-dotriacontane-bis-rhodamine 101 ester (Rh101C32Rh101) in lipid bilayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and in liquid solvents. The results are compared with those of rhodamine 101 octadecanyl ester (Rh101C18). Both molecules are solubilized in the lipid bilayer and the Rh101 moieties are anchored in the lipid-water interface, so that the electronic transition dipole moments (S 0 ↔S 1) are oriented preferentially in the plane of the bilayer. At low concentrations of the dyes in lipid bilayers of DOPC, the fluorescence relaxation is single exponential with a lifetime of τ=4.9±0.2 ns. The relative fluorescence quantum yield of ΦC32/ΦC18 ≈ 0.95 in DOPC vesicles. These results strongly suggest that only a small fraction of the Rh101C32Rh101 molecules are quenched, by, for example, intra- or intermolecular dimers in the ground state at mole fractions of less than 0.1% in the lipid bilayers. For Rh101C32Rh101 in lipid vesicles, the steady-state and time-resolved fluorescence anisotropies are compatible with efficient intramolecular electronic energy transfer. It is concluded that nearly every Rh101C32Rh101 molecule is spanning across the lipid bilayer of DOPC.

Nonadiabaticity and intramolecular electronic energy transfer in the photodissociation of 1-bromo-3-iodopropane at 222 nm

The photodissociation of 1-bromo-3-iodopropane (1,3-C3H6BrI) at 222 nm is studied with crossed laser-molecular beam experiments. Irradiation at this wavelength excites an n(Br)→σ*(C–Br) transition which promotes the molecule to an approximately diabatic excited state potential energy surface which is dissociative in the carbon–bromine bond. This surface intersects an approximately diabatic surface of n(I)→σ*(C–I) character at extended C–Br distances; this surface is dissociative in the carbon–iodine bond. Crossings from the surface initially accessed to the intersecting surface correspond to intramolecular excitation transfer from the carbon–bromine to the carbon–iodine bond. The incidence of such transfer and hence of carbon–iodine bond fission depends upon the strength of the off-diagonal potential coupling of the two diabatic states. These experiments test the dependence of the coupling and consequent energy transfer upon the separation distance of the C–Br and C–I chromophores. The data show C–Br fission dominates C–I fission by a ratio of 4:1 and determine the center-of-mass translational energy distributions and angular distributions of these processes. The measured anisotropy parameters are β(C–Br)=1.6±0.4 and β(C–I)=0±0.2. A third photofission process, IBr elimination, also contributes to the observed signal. The results of the study of C–Br and C–I fission are compared to previous studies on similar molecules to understand how the branching depends on the relative positioning of the C–Br and C–I chormophores.

Intramolecular Electronic Energy Transfer between Naphthalene and Protoporphyrin Chromophores Bound to Sequential Peptides

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIntramolecular Electronic Energy Transfer between Naphthalene and Protoporphyrin Chromophores Bound to Sequential PeptidesBasilio Pispisa, Mariano Venanazi, Antonio Palleschi, and Giancarlo ZanottiCite this: Macromolecules 1994, 27, 26, 7800–7808Publication Date (Print):December 1, 1994Publication History Published online1 May 2002Published inissue 1 December 1994https://doi.org/10.1021/ma00104a039RIGHTS & PERMISSIONSArticle Views82Altmetric-Citations21LEARN 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 (1 MB) Get e-Alerts Get e-Alerts

Mediated Electronic Energy Transfer: Effect of a Second Acceptor State

Intramolecular electronic energy transfer was observed in bichromophoric molecules with the general structure donor-spacer-acceptor where indole is the donor, naphthalene is the acceptor, and cyclohexane is the inert spacer. Measurements were performed in a supersonic jet where both the absorption and emission spectra of the two chromophores were well-resolved and indole could be selectively excited with essentially no excitation on naphthalene. The emission produced on excitation of indole showed strong naphthalene emission and relatively weak indole emission. Moreover, the fluorescence lifetime was similar to the fluorescence lifetime of naphthalene, indicating that the energy transfer occurred on a time scale faster than the fluorescence lifetime of the donor

Molecular engineering of cyclic ?-diketone aromatic ring bichromophoric molecules for studies of intramolecular electronic energy transfer

The design, structures and spectral properties of a number of bichromophoric molecules are presented. These bichromophoric molecules are composed of an aromatic ring connected by two methylene chains to an α-diketone moiety. Both absorption and emission spectra can be attributed to a superposition of the individual spectra of the separate chromophores. The critical transfer radius for electronic energy transfer from the aromatic (donor) chromophore to the α-diketone (acceptor) chromophore was calculated from the spectral overlap between the fluorescence spectrum of the aromatic moiety and the absorption spectrum of the α-diketone moiety. The results show that this series of molecules is well suited for a mechanistic study of short-range intramolecular electronic energy transfer.

Electronic energy transfer: density of states

Intramolecular electronic energy transfer has been observed in one isomer of the bichromophoric molecule D-Sp-A where the donor (D) is naphthalene, the spacer (Sp) is cyclohexane, and the acceptor (A) is dimethylaniline (DMA). Because the emission spectra of both the donor and acceptor overlap, the emission wavelength could not be used as a diagnostic for energy transfer. However, the donor and acceptor have very different fluorescence lifetimes, and large changes in the fluorescence lifetimes of the vibronic states of naphthalene due to the presence of DMA could be used as a measure of the mixing and energy transfer between the two chromophores