Effect of charge of polymeric stabilizing agents on the quantum yields of photoinduced electron transfer from photoexcited colloidal semiconductors to adsorbed viologens

Langmuir ◽  
1987 ◽  
Vol 3 (6) ◽  
pp. 1147-1150 ◽  
Author(s):  
Yoshio. Nosaka ◽  
Marye Anne. Fox
Keyword(s):  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Quantum Yields ◽  
Stabilizing Agents ◽  
Colloidal Semiconductors

Germanium(IV) phthalocyanine-porphyrin based hetero trimers: synthesis, spectroscopy and photochemistry

2012 ◽  
Vol 16 (03) ◽  
pp. 282-289 ◽  
Author(s):  
Jaipal Kandhadi ◽  
Ravi Kumar Kanaparthi ◽  
Lingamallu Giribabu
Keyword(s):  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Method Comparison ◽  
Differential Pulse ◽  
Electronic Energy ◽  
Proton Nuclear Magnetic Resonance ◽  
Quantum Yields ◽  
Electronic Energy Transfer ◽  
Fluorescence Quantum Yields ◽  
Uv Visible

The known oxophilicity of Germanium(IV) ion of Germanium(IV) phthalocyanine and porphyrins have been exploited to synthesize functionally active, "axial-bonding" -type hetero oligomers. These hetero trimers have been fully characterized by elemental analysis, FAB-MS, UV-visible, proton nuclear magnetic resonance (1D and 1 H -1 H COSY) and fluorescence spectroscopies, as well as differential pulse voltammetric method. Comparison of their spectroscopic and electrochemical data with those of the corresponding individual constituents reveals that there is no apparent π–π interactions in these "vertically" linked hetero oligomers. The fluorescence quantum yields were found to be lower of these hetero oligomers in comparison with those of the monomeric chromophores. Electronic energy transfer and photoinduced electron transfer from axial porphyrins to central metalloid phthalocyanine and photoinduced electron transfer from singlet state of axial porphyrins to central metalloid phthalocyanine is detected in these hetero oligomers.

1,3,5-Triarylpyrazolines — pH-driven off-on-off molecular logic devices based on a “receptor1-fluorophore-spacer-receptor2” format with internal charge transfer (ICT) and photoinduced electron transfer (PET) mechanisms

2015 ◽  
Vol 93 (2) ◽  
pp. 199-206 ◽  
Author(s):  
Ramon Zammit ◽  
Maria Pappova ◽  
Esther Zammit ◽  
John Gabarretta ◽  
David C. Magri
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Charge Transfer ◽  
Photoinduced Electron Transfer ◽  
Photophysical Properties ◽  
Molecular Probes ◽  
Quantum Yields ◽  
Ph Sensing ◽  
Internal Charge Transfer ◽  
Internal Charge

The excited state photophysical properties of the 1,3,5-triarylpyrazolines 1–4 were studied in methanol and 1:1 (v/v) methanol–water, as well as 1:4 (v/v) methanol–water and water by fluorescence spectroscopy. The molecules 2–4 incorporate a “receptor1-fluorophore-spacer-receptor2” format while 1 is a reference compound based on a “fluorophore-receptor1” design. The molecular probes operate according to photoinduced electron transfer (PET) and internal charge transfer (ICT) processes. At basic and neutral pHs, 2–4 are essentially nonfluorescent due to PET from the electron-donating dimethylamino moiety appended on the 5-phenyl ring to the excited state of the 1,3,5-triarylpyrazoline fluorophore. At proton concentrations of 10−3 mol/L, the dimethylamino unit is protonated resulting in a strong blue fluorescence about 460 nm with significant quantum yields up to 0.54. At acid concentrations above 10−2 mol/L, fluorescence quenching is observed by an ICT mechanism due to protonation of the pyrazoline chromophore. Symmetrical off-on-off fluorescence–pH profiles are observed, spanning six log units with a narrow on window within three pH units. Hence, 2–4 are novel examples of ternary photonic pH sensing molecular devices.

The Formation of Fluorescent Alkaline Earth Complexes by 4-{2-[10-(2-Morpholinoethyl)-9-anthryl]methyl}morpholine and its -Ethyl}morpholine and -Propyl}morpholine Analogues in Acetonitrile

2003 ◽  
Vol 56 (4) ◽  
pp. 301 ◽  
Author(s):  
Jason P. Geue ◽  
Nicholas J. Head ◽  
A. David Ward ◽  
Stephen F. Lincoln
Keyword(s):  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Alkaline Earth ◽  
Quantum Yields ◽  
Complexation Constants ◽  
Sandwich Complex ◽  
Complexation Constant ◽  
Receptor Structure ◽  
Alkaline Earths ◽  
Tertiary Nitrogen

The formation of fluorescent alkaline earth complexes of 4-{2-[10-(2-morpholinoethyl)9-anthryl]methyl}morpholine and its new -ethyl}morpholine and -propyl}morpholine analogues, L = (1)–(3), in acetonitrile is reported. Each L has a ‘fluorophore–spacer–receptor’ structure in the sequence ‘anthracene–(methylene)n–morpholine’ in which quenching of the anthracene fluorophore becomes less effective as the receptor tertiary nitrogen becomes more distant with an increase in n from 1 to 3. Complexation by the alkaline earths (M2+) modulates photoinduced electron transfer (PET) and enhances the fluorescence of (1)–(3). The two alkyl morpholine receptors of (1)–(3) may either complex M2+ singly to form [ML]2+ and [M2L]4+ or cooperatively to form a [ML′]2+ ‘sandwich’ complex depending on the length of the alkyl spacer. Thus, (1) dominantly forms [ML]2+ and [ML′]2+ while (2) and (3) form all three complexes as exemplified by [Mg(2)]2+ and [Mg(2)′]2+ characterized by the overall complexation constant K1 = 9.19 × 104 dm3 mol−1 and [Mg2(2)]4+ characterized by the stepwise complexation constant K2 = 1.19 × 103 dm3 mol−1 at 298.2 K and I = 0.05 mol dm−3 (NEt4ClO4). The most stable and fluorescent complexes are formed by Mg2+ and Ca2+, consistent with M2+ size being an important factor affecting complex characteristics. Eighteen complexation constants and quantum yields are reported for the (1)–(3) complexes together with those for (1)–(3) alone. In 40 : 60 (v/v) 1,4-dioxan/water, protonation modulates PET to increase the fluorescence of (1)H22+–(3)H22+. (The pKa values for (2)H22+ are 6.38 and 5.62, and for (3)H22+ are 7.00 and 6.25.) The syntheses of (2) and (3) are reported.

Photoelectronic Utility of Photoinduced Electron Transfer by Phosphorescent Ir(III) Complexes

2014 ◽  
Vol 1668 ◽  
Author(s):  
Youngmin You
Keyword(s):  
Electron Transfer ◽  
Energy Conversion ◽  
Photoinduced Electron Transfer ◽  
Chemical Energy ◽  
Quantum Yields ◽  
Intermolecular Electron Transfer ◽  
Wide Range ◽  
Electrochemically Active ◽  
Order Of Magnitude ◽  
Natural Photosynthesis

ABSTRACTIntermolecular photoinduced electron transfer (PeT) has found a wide range of photoelectronic utility. One of the most notable examples includes the natural photosynthesis, where PeT between chlorophyll and quinone triggers photon-to-chemical energy conversion. We observed that phosphorescent Ir(III) complexes exhibited efficient PeT to trigger a cascade of catalytic intermolecular electron transfer among electrochemically active molecules. To establish the photoelectronic utility of PeT, a series of cyclometalated Ir(III) complexes were prepared and evaluated for photoelectrocatalytic conversion of dithienylethene (DTE) compounds. Selective photoexcitation of the Ir(III) complexes facilitated ultrafast PeT from DTE. The oxidative PeT initiated electrocatalytic cycloreversion of DTE, yielding one order of magnitude enhancement in quantum yields relative to direct photochromic conversion.

Computationally Assisted Design of High Signal-to-Noise Photoinduced Electron Transfer-Based Voltage-Sensitive Dyes

2020 ◽  
Author(s):  
Rishikesh Kulkarni ◽  
Anneliese Gest ◽  
Chun Kei Lam ◽  
Benjamin Raliski ◽  
Feroz James ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Dft Calculations ◽  
Photoinduced Electron Transfer ◽  
Density Functional ◽  
Embryonic Stem ◽  
High Sensitivity ◽  
Md Simulations ◽  
High Signal ◽  
Signal To Noise ◽  
Green Fluorescent

<p>High signal-to-noise optical voltage indicators will enable simultaneous interrogation of membrane potential in large ensembles of neurons. However, design principles for voltage sensors with high sensitivity and brightness remain elusive, limiting the applicability of voltage imaging. In this paper, we use molecular dynamics (MD) simulations and density functional theory (DFT) calculations to guide the design of a bright and sensitive green-fluorescent voltage-sensitive fluorophore, or VoltageFluor (VF dye), that uses photoinduced electron transfer (PeT) as a voltage-sensing mechanism. MD simulations predict an 11% increase in sensitivity due to membrane orientation, while DFT calculations predict an increase in fluorescence quantum yield, but a decrease in sensitivity due to a decrease in rate of PeT. We confirm these predictions by synthesizing a new VF dye and demonstrating that it displays the expected improvements by doubling the brightness and retaining similar sensitivity to prior VF dyes. Combining theoretical predictions and experimental validation has resulted in the synthesis of the highest signal-to-noise green VF dye to date. We use this new voltage indicator to monitor the electrophysiological maturation of human embryonic stem cell-derived medium spiny neurons. </p>

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