External heavy atom effect on excited state quenching and exciplex decay

Gutierrez, A. R.; Whitten, David G.

doi:10.1021/ja00829a066

Cited by 13 publications

(6 citation statements)

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“…76 Therefore, it is expected that excitation in this region where the t-bpete effectively absorbs may enhance the population of 3 IL t-bpete by the intersystem crossing (ISC) from the 1 IL t-bpete because of coordination to Ln 3+ ions, and consequently to an efficient trans-to-cis photoisomerization process. 76,77 The occurrence of a triplet mechanism for the isomerization of free t-bpete ligand is well established 78 and, for the Ln 3+ complexes, as the triplet pathway becomes more competitive than the singlet, because of the heavy atom effect, the 3 IL t-bpete state should be the main pathway for the photoisomerization. 79−81 Interestingly, the trans-to-cis photoisomerization of bpete ligand induced by UV irradiation has been demonstrated to be responsible for the emission intensity increase observed in solutions of rhenium complexes.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Photo–Click Chemistry to Design Highly Efficient Lanthanide β-Diketonate Complexes Stable under UV Irradiation

et al. 2013

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Europium ( t -Eu) and gadolinium ( t -Gd) β-diketonate complexes with photoactive t-bpete ligand, [Ln(btfa)3(t-bpete)(MeOH)] (Ln = Eu, Gd), where btfa– and t-bpete are 4,4,4-trifluoro-1-phenyl-1,3-butanedionate and trans-1,2-bis(4-pyridyl)ethylene, respectively, were synthesized, characterized by vibrational, absorption (reflectance) and photoluminescence spectroscopies and their crystal structure was determined using single-crystal X-ray diffraction. B3LYP calculations were performed to support the interpretation and rationalization of the experimental results. The complexes, under UV irradiation, do not display the typical photodegradation of the β-diketonate ligands exhibiting, in turn, an unprecedented photostability during, at least, 10 h. During UV-A exposure (>330 nm), the emission intensities of both complexes increase drastically (∼20 times), whereas for t -Eu the emission quantum yield is enhanced at least 30-fold. A mechanism based on a photoclick trans-to-cis isomerization of both t- and c-bpete moieties was proposed to explain the abnormal photostability of these compounds, either in solid state or in solution. The experimental and computational results are consistent with a photostationary state involving the trans-to-cis isomerization of the bpete ligand under continuous UV-A exposure, which thus diverts the incident radiation from other deleterious photochemical or photophysical processes that cause the typical photobleaching behavior of chelate lanthanide complexes. This shielding mechanism could be extended to other ligands permitting the design of new lanthanide-based photostable systems under UV exposure for applications in lighting, sensing, and displays.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Photo–Click Chemistry to Design Highly Efficient Lanthanide β-Diketonate Complexes Stable under UV Irradiation

et al. 2013

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“…The trans -BPE free ligand has been shown to have a very low quantum efficiency (Φ = 0.003 in benzene, 313 nm) for trans − cis isomerization upon direct irradiation in the absence of triplet sensitizers,11a which is in contrast to the efficient trans − cis photoisomerization of trans -stilbene (Φ = 0.52 in pentane, 313 nm) and trans -4-styrylpyridine (Φ = 0.38 in CH 2 Cl 2 , 313 nm) 7e. The lack of direct irradiation trans − cis isomerization of BPE in the absence of a triplet sensitizer suggests that the isomerization of BPE occurs primarily through the triplet excited state …”

Section: Resultsmentioning

confidence: 99%

Self-Assembly of Transition-Metal-Based Macrocycles Linked by Photoisomerizable Ligands: Examples of Photoinduced Conversion of Tetranuclear−Dinuclear Squares

2002

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A series of hetero- and homometallic square complexes bridged by a photoactive 4,4'-azopyridine (AZP) or 1,2-bis(4-pyridyl)ethylene (BPE) ligand, cyclobis[[cis-(dppf)M](mu-L)(2)(fac-Re(CO)(3)Br)](OTf)(4) (M = Pd, L = trans-AZP (5); M = Pt, L = trans-AZP (7); M = Pd, L = trans-BPE (8); M = Pt, L = trans-BPE (10)), cyclo[[cis-(dppf)M](mu-L)(2)(fac-Re(CO)(3)Br)](OTf)(2) (M = Pd, L = cis-AZP (6); M = Pd, L = cis-BPE (9)), [cis-(dppf)Pd(mu-trans-AZP)](4)(OTf)(8) (11), and [cis-(dppf)Pd(mu-cis-AZP)](2)(OTf)(4) (12), where dppf is 1,1'-bis(diphenylphosphino)ferrocene and OTf is trifluoromethanesulfonate anion, were prepared by thermodynamically driven self-assembly processes. The photophysical and photochemical properties of these complexes have been investigated, and all of them show a lack of luminescence in room temperature solution. Upon irradiation at 313 or 366 nm, Pd(II)-Re(I)-containing tetranuclear squares 5, 8, and 11 undergo photoisomerization and convert to their corresponding dinuclear complexes 6, 9, and 12, whereas Pt(II)-Re(I)-based squares 7 and 10 show only slow square disassembling processes. The tetranuclear squares can be fully recovered by heating the photoisomerized solution for several hours.

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“…From these considerations, we assume the following reaction mechanism. For the case of 314-nm excitation: SSP + hv -SSP* (5) SSP* -X* (6) X* -SMC* (7) X* + SMC -X + SMC* (8) X* -X + hvF (9) For the case of 576-nm excitation: SMC + hv -* SMC* The reaction through eqs 6 and 7 is an adiabatic photoreaction,20 in which a photochemical reaction occurs along an excited elec-(20) Turro, N. J.; McVey, J.; Ramamurthy, V.; Lechtken, P. Angew. Chem., Ini.…”

Section: Discussionmentioning

confidence: 99%

Picosecond time-resolved fluorescence spectroscopy of the photochromic reaction of spiropyran in Langmuir-Blodgett films

Minami¹,

Tamai²,

Yamazaki³

et al. 1991

J. Phys. Chem.

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The photochromic reaction of spiropyran *» merocyanine has been studied with l'-octadecyl-3',3'-dimethyl-6-nitrospiro-[2H-1 -benzopyran-2,2'-indoline] (SSP) incorporated in Langmuir-Blodgett (LB) films prepared in a mixed film with stearic acid, arachidic acid, and tripalmitine. Time-resolved fluorescence spectra and decay curves of SSP and its photoisomer, merocyanine (SMC), were measured with a picosecond time-correlated, single-photon-counting apparatus. When SSP in LB films was excited at 360 nm, two fluorescence bands were observed: one has a maximum at 660 nm, and the other has a relatively weak band at 530 nm. We assigned them respectively to the fluorescence band of SMC and an intermediate X as a precursor of SMC. The rigidity of the medium surrounding photochromic molecules is an important factor in determining the rate of reversible photoconversion of SSP -*-* SMC.

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External heavy atom effect on excited state quenching and exciplex decay

Cited by 13 publications

References 1 publication

Photo–Click Chemistry to Design Highly Efficient Lanthanide β-Diketonate Complexes Stable under UV Irradiation

Photo–Click Chemistry to Design Highly Efficient Lanthanide β-Diketonate Complexes Stable under UV Irradiation

Self-Assembly of Transition-Metal-Based Macrocycles Linked by Photoisomerizable Ligands: Examples of Photoinduced Conversion of Tetranuclear−Dinuclear Squares

Picosecond time-resolved fluorescence spectroscopy of the photochromic reaction of spiropyran in Langmuir-Blodgett films

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