trans-4-Stilbenecarboxylatoalkylpentaamminecobalt(III) Perchlorates: Synthesis and Intramolecular Energy Transfer

1996 ◽  
Vol 61 (3) ◽  
pp. 342-354 ◽  
Author(s):  
Cyril Párkányi ◽  
Lois Shiow-Chyn Yeh Huang ◽  
Sung Gun Chu ◽  
Alfred T. Jeffries III
Keyword(s):  
Energy Transfer ◽  
Excited State ◽  
Singlet State ◽  
Excitation Energy Transfer ◽  
Intramolecular Energy Transfer ◽  
Triplet Excited State ◽  
Excited Singlet ◽  
Fluorescence Studies ◽  
Methylene Groups ◽  
A Charge

Three homologs of trans-4-stilbenecarboxylic acid, viz., trans-4-stilbeneacetic acid (18), β-(trans-4-stilbene)propionic acid (19), and γ-(trans-4-stilbene)butyric acid (20) were synthesized and, together with the parent trans-4-stilbenecarboxylic acid, used to obtain the corresponding [ω-(trans-4-stilbene)carboxylatoalkylpentaamminecobalt(III) complexes, [(PhCH=CHC6H4(CH2)nCOO)Co(NH3)5]2+ (1-4), where n = 0, 1, 2, or 3. Fluorescence studies suggest that an intramolecular excitation energy transfer occurs from the first excited singlet state of the ligand to the metal giving rise to a charge-transfer triplet-excited state of the complex, based on the analogy with previous work on complex 1. The efficiency of the energy transfer seems to decrease with increasing number of the methylene groups in the ligand.

Excited State Dynamics of Novel Diporphyrins with Dissimilar Cores

1999 ◽  
Vol 03 (01) ◽  
pp. 70-77 ◽  
Author(s):  
M. RAVIKUMAR ◽  
R. P. PANDIAN ◽  
T. K. CHANDRASHEKAR
Keyword(s):  
Energy Transfer ◽  
Excited State ◽  
Excitation Wavelength ◽  
Triplet Excited State ◽  
Lifetime Measurements ◽  
Time Resolved ◽  
Fluorescence Studies ◽  
Axial Ligation ◽  
Excitation Time ◽  
The Individual

The singlet and triplet excited state properties of two diporphyrins, H 2- H and Zn - H , are described. Steady state fluorescence studies indicate that the emission of the H 2- H diporphyrin is dependent on the excitation wavelength and is dominated by the emission of the individual constituent monomers at their respective excitation. Time-resolved studies show two lifetimes ascribable to the normal and thiaporphyrin subunits. However, the emission of the Zn - H diporphyrin is dominated by the thiaporphyrin subunit irrespective of the wavelength of excitation, suggesting an energy transfer from the Zn porphyrin subunit to the thiaporphyrin subunit. Lifetime measurements in toluene show two lifetimes due to open and folded conformations, while in DMF an additional component due to axial ligation is observed. The efficiency of energy transfer is moderately higher in DMF (72%) than in toluene (68%). Triplet ESR studies on the H 2- H dimer reveal a localized triplet with ZFS parameters and ESP pattern the same as for the individual monomers. On the other hand, triplet ESR of the Zn - H diporphyrin reveals triplet characteristics of the thiaporphyrin subunit, indicating an energy transfer in the triplet state.

Intramolecular sensitization within steroids: Excited-state interaction of C-17 α and β carbon–bromine bonds with a C-6 carbonyl group

2003 ◽  
Vol 81 (6) ◽  
pp. 660-668 ◽  
Author(s):  
Wen-Shan Li ◽  
Lokman Torun ◽  
Harry Morrison
Keyword(s):  
Energy Transfer ◽  
Excited State ◽  
Carbonyl Group ◽  
Singlet State ◽  
State Interaction ◽  
Excited Singlet State ◽  
Excited Singlet

The synthesis, photochemistry, and photophysics of 17α-bromo-3α-(triphenylsilyloxy)-5α-androstan-6-one (1) and 17β-bromo-3β-(triphenylsilyloxy)-5α-androstan-6-one (2) have been studied in aqueous tetrahydrofuran. The 17α-bromo isomer gives evidence (reduced ϕf, τ1, and ϕisc for the ketone) for interaction between the ketone and C–Br moieties in the excited singlet state. Some photodehalogenation is also observed upon excitation of the ketone chromophore. This interaction seems to be absent or minimal for the 17β-bromo isomer.Key words: photodehalogenation, bromosteroid, ketosteroid, intramolecular singlet–singlet energy transfer (ISSET).

Photoswitchable Sensitization of Porphyrin Excited States

2006 ◽  
Vol 59 (3) ◽  
pp. 170 ◽  
Author(s):  
Stephen D. Straight ◽  
Yuichi Terazono ◽  
Gerdenis Kodis ◽  
Thomas A. Moore ◽  
Ana L. Moore ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Excited State ◽  
Excited States ◽  
Singlet State ◽  
Molecular Switches ◽  
Cyclic Form ◽  
Excited Singlet ◽  
Efficient Energy Transfer ◽  
Efficient Energy ◽  
Covalently Linked

Light-driven molecular switches consisting of a porphyrin covalently linked to a fulgimide photochrome antenna have been prepared. Light absorbed by the cyclic form of the fulgimide is transferred to the porphyrin with ≥ 95% efficiency, generating the porphyrin first excited singlet state. Irradiation with visible light photoisomerizes the fulgimide to the open form, which does not absorb above 450 nm, and antenna function is abolished. UV irradiation converts the fulgimide back into the cyclic form, re-establishing efficient energy transfer. Photoisomerization of the fulgimide thus controls generation of the porphyrin excited state, which may then be used to carry out a variety of useful photochemical processes.

scholarly journals Spectral properties and photophysics of arylacetylenes in thin films

2014 ◽  
Vol 2 (1) ◽  
Author(s):  
Rebecca Flamini ◽  
Benedetta Carlotti ◽  
Anna Spalletti ◽  
Assunta Marrocchi
Keyword(s):  
Thin Films ◽  
Energy Transfer ◽  
Singlet State ◽  
Excited Singlet ◽  
Acetylene Derivative ◽  
Time Resolved ◽  
Homogeneous Surface ◽  
Blend Films ◽  
J Aggregates ◽  
Emitting Species

AbstractWe report the photobehaviour of a series of eight structurally related arylacetylene derivatives, in solution as well as in pristine and PC61BM blended thin-_lms. The formation of both H- and J-aggregates in the solid state have been demonstrated, and, interestingly, an energy transfer from H-aggregates or/and from residual "unstacked" molecules to J-aggregates has been found, the latter being the only emitting species. The fuorescence quenching by PC61BM at di_erent loadings has been studied in blend films, and it has been found particularly effcient in the case of a symmetrical peripheral substitution of the acetylene derivative core. Preliminary time-resolved measurements in emission (ns resolution) and in absorption (fs resolution) con_rmed the H⟶J energy transfer and underlined the presence of delayed fuorescence from Jaggregates, formed by energy transfer from the long-lived first excited singlet state of H-aggregates. In all cases, a homogeneous surface morphology of thin films.

Fast Energy Transfer of Charge−Transfer Triplet Excited State (3CT) of [Ru(bpy)3](PF6)2to Os2+at Short Distances in the Crystal

2000 ◽  
Vol 104 (22) ◽  
pp. 5176-5180 ◽  
Author(s):  
Minoru Tsushima ◽  
Noriaki Ikeda ◽  
Koichi Nozaki ◽  
Takeshi Ohno
Keyword(s):  
Energy Transfer ◽  
Excited State ◽  
Charge Transfer ◽  
Triplet Excited State

Excited state carbon acid dissociation and competing photorearrangements of 5H-dibenzo[a,c]cycloheptene derivatives

1996 ◽  
Vol 74 (8) ◽  
pp. 1447-1464 ◽  
Author(s):  
David. Budac. ◽  
Peter Wan
Keyword(s):  
Excited State ◽  
Fluorescence Quenching ◽  
Singlet State ◽  
Acid Dissociation ◽  
Excited Singlet ◽  
Deuterium Incorporation ◽  
Group A ◽  
Carbon Acids ◽  
Work Structure ◽  
Carbon Acid

The first examples of dissociating excited state carbon acids were reported by our group. A necessary structural feature is the 5H-dibenzocycloheptene ring system where the incipient carbanion is formally an antiaromatic system in S0. In this work, structure–reactivity studies of the excited singlet state carbon acid dissociation and competing formal di-π-methane rearrangement of several 5H-dibenzo[a,c]cycloheptene derivatives have been carried out in order to gain more insights into the photochemistry displayed by these compounds. Photolysis of 7-deuterio-5H-dibenzo[a,c]cycloheptene (9) in aqueous solution showed that the photogenerated carbanion is allylically delocalized. Derivative 7 was found to be less reactive than 3 with respect to carbon acid dissociation whereas 8 was unreactive. Ethanolamine (in CH3CN) was found to be an effective base in catalyzing carbon acid dissociation for 3, 7, and 9, as indicated by higher yields of deuterium incorporation and rates of fluorescence quenching. Binaphthyl derivatives 10 and 11 displayed contrasting photobehaviour. Photolysis of binaphthyl 11 resulted in only efficient (ΦP = 0.47) formal di-π-methane rearrangement under all conditions and no evidence was found for carbon acid dissociation, even in the presence of ethanolamine as base. On the other hand, the formal di-π-methane reaction was very inefficient for binaphthyl 10 (Φp < 0.001). Due to the conformational rigidity inherent in 10, the methylene protons at the 3-position are NMR resolvable as pseudo-axial and pseudo-equatorial protons. Photolysis in the presence of ethanolamine (in D2O–CH3CN) resulted in stereoselective deprotonation of the pseudo-axial proton (Φex ≈ 0.02), as indicated by deuterium exchange studies. The results show that excited state carbon acid dissociation is an observable general reaction of dibenzo and dinaphtho cycloheptenes only if more favourable photochemical pathways are not competing. Key words: excited state carbon acid, di-π-methane rearrangement, carbanion, stereoelectronic effect, fluorescence quenching.

Energy Transfer in Organic Dendrimer Antenna Funnel and Anti-Funnel Supermolecules

1998 ◽  
Vol 543 ◽  
Author(s):  
Stephen F. Swallen ◽  
Raoul Kopelman ◽  
Jeffrey S. Moore
Keyword(s):  
Molecular Structure ◽  
Energy Transfer ◽  
Steady State ◽  
Intermolecular Interactions ◽  
Molecular Geometry ◽  
Intramolecular Energy Transfer ◽  
Fluorescence Studies ◽  
Energy Trapping ◽  
Exciton Localization ◽  
Steady State Fluorescence

AbstractThe photophysics of exciton localization and energy transfer are examined in two unique classes of phenylacetylene dendrimers. One set of supermolecules is observed to efficiently and rapidly funnel absorbed radiation toward the molecular locus, while a slight change in molecular structure creates an effective “anti-funnel”, greatly reducing the efficiency of energy trapping. Lifetime-based and steady state fluorescence studies are used to determine the rates of intramolecular energy transfer and to glean information on molecular geometry and intermolecular interactions in two solvents.

Excited state spectroscopy of 1,5‐naphthyridine: Identification of the lowest energy excited singlet state as 1Bg(1nπ*)

1983 ◽  
Vol 79 (8) ◽  
pp. 3639-3644 ◽  
Author(s):  
David W. Boldridge ◽  
Gary W. Scott
Keyword(s):  
Excited State ◽  
Singlet State ◽  
Excited Singlet State ◽  
Excited Singlet
Sign in / Sign up

Export Citation Format

Share Document