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Amy S. Mullin - One of the best experts on this subject based on the ideXlab platform.
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unraveling the energy dependence in large δe v rt energy transfer separation of δe and probability in the collisional relaxation of highly vibrationally excited pyrazine evib 36 000 to 41 000 cm 1 by co2
Journal of Chemical Physics, 1999Co-Authors: Mark C. Wall, Andrew S. Lemoff, Amy S. MullinAbstract:The energy dependence of collisional relaxation of highly vibrationally excited pyrazine through collisions with CO2 has been investigated for pyrazine vibrational energies Evib=36 000–41 000 cm−1. Highly excited pyrazine was prepared by absorption of tunable pulsed UV laser light at four wavelengths between 251 and 271 nm. Data for pyrazine excitation at 246 and 266 nm have been published previously and are included with the data presented here. We have used high resolution transient absorption spectroscopy to measure nascent distributions of rotational and translational energy gain in CO2 molecules in their ground vibrationless (0000) state that are populated through collisions with excited pyrazine molecules. Our results reveal that substantial amounts of rotational and translational energy are imparted to CO2(0000) molecules for all pyrazine energies studied and that the magnitude of this energy changes very little for a 13% change in the pyrazine vibrational energy. In contrast, state-resolved rates ...
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observation of an energy threshold for large δe collisional relaxation of highly vibrationally excited pyrazine evib 31 000 41 000 cm 1 by co2
Journal of Chemical Physics, 1999Co-Authors: Michael S. Elioff, Mark C. Wall, Andrew S. Lemoff, Amy S. MullinAbstract:Energy dependent studies of the collisional relaxation of highly vibrationally excited pyrazine through collisions with CO2 were performed for initial pyrazine energies Evib=31 000–35 000 cm−1. These studies are presented along with earlier results for pyrazine with Evib=36 000–41 000 cm−1. High-resolution transient IR laser absorption of individual CO2 (0000) rotational states (J=56–80) was used to investigate the magnitude and partitioning of energy gain into CO2 rotation and translation, which comprises the high energy tail of the energy transfer distribution function. Highly vibrationally excited pyrazine was prepared by absorption of pulsed UV light at seven wavelengths in the range λ=281–324 nm, followed by radiationless decay to pyrazine’s ground electronic state. Nascent CO2 (0000) rotational populations were measured for each UV excitation wavelength and distributions of nascent recoil velocities for individual rotational states of CO2 (0000) were obtained from Doppler-broadened transient linewid...
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molecular supercollisions evidence for large energy transfer in the collisional relaxation of highly vibrationally excited pyrazine by co2
Journal of Chemical Physics, 1995Co-Authors: Amy S. Mullin, Chris A Michaels, George W FlynnAbstract:The temperature dependence of the collisional quenching of highly vibrationally excited pyrazine by CO2 molecules has been investigated for the temperature range 243–364 K using high resolution time resolved diode laser spectroscopy. Particular emphasis is placed on vibration to rotation‐translation (V→R/T) energy transfer which leaves the CO2 vibrations unexcited and occurs predominantly through short‐range repulsive forces. Vibrationally hot pyrazine is prepared by 248 nm excimer laser pumping, followed by rapid radiationless transitions to the ground electronic state. For the range of experimental cell temperatures used here, the nascent rotational population distributions of the 0000 ground state of CO2 resulting from collisions with hot pyrazine were probed at short times following excitation of pyrazine by the excimer laser pulse. The CO2 translational recoil velocity was also measured for individual rotational levels of the 0000 state. In addition, temperature dependent rate constants and probabilities were determined for energy transfer from the vibrationally hot pyrazine into individual rotational levels of the 0000 state of CO2. The rotational distributions, velocity recoils, and quenching rates exhibit a very weak temperature dependence for production of CO2 high J states, indicating that the CO2 molecules involved in these energy transfer events originate from rotational levels only slightly greater than the thermal mean J value. Based on these results, values for ΔE, the energy transfer from hot pyrazine to CO2 resulting in final CO2 0000 states J=58 through J=82, are estimated to range from 2550 to 7090 cm−1 in a single collision.The temperature dependence of the collisional quenching of highly vibrationally excited pyrazine by CO2 molecules has been investigated for the temperature range 243–364 K using high resolution time resolved diode laser spectroscopy. Particular emphasis is placed on vibration to rotation‐translation (V→R/T) energy transfer which leaves the CO2 vibrations unexcited and occurs predominantly through short‐range repulsive forces. Vibrationally hot pyrazine is prepared by 248 nm excimer laser pumping, followed by rapid radiationless transitions to the ground electronic state. For the range of experimental cell temperatures used here, the nascent rotational population distributions of the 0000 ground state of CO2 resulting from collisions with hot pyrazine were probed at short times following excitation of pyrazine by the excimer laser pulse. The CO2 translational recoil velocity was also measured for individual rotational levels of the 0000 state. In addition, temperature dependent rate constants and probabili...
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molecular supercollisions evidence for large energy transfer in the collisional relaxation of highly vibrationally excited pyrazine by co2
Journal of Chemical Physics, 1995Co-Authors: Amy S. Mullin, Chris A Michaels, George W FlynnAbstract:The temperature dependence of the collisional quenching of highly vibrationally excited pyrazine by CO2 molecules has been investigated for the temperature range 243–364 K using high resolution time resolved diode laser spectroscopy. Particular emphasis is placed on vibration to rotation‐translation (V→R/T) energy transfer which leaves the CO2 vibrations unexcited and occurs predominantly through short‐range repulsive forces. Vibrationally hot pyrazine is prepared by 248 nm excimer laser pumping, followed by rapid radiationless transitions to the ground electronic state. For the range of experimental cell temperatures used here, the nascent rotational population distributions of the 0000 ground state of CO2 resulting from collisions with hot pyrazine were probed at short times following excitation of pyrazine by the excimer laser pulse. The CO2 translational recoil velocity was also measured for individual rotational levels of the 0000 state. In addition, temperature dependent rate constants and probabili...
Sayuri Kobayashi - One of the best experts on this subject based on the ideXlab platform.
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swern oxidation of bicyclo 2 2 1 hept 5 ene 2 3 diol and its pyrazine fused derivatives an improved synthesis of bicyclo 2 2 1 hept 5 ene 2 3 dione and an unexpected ring opening reaction
Molecules, 2000Co-Authors: Tomoshige Kobayashi, Sayuri KobayashiAbstract:Abstract: An improved synthesis of bicyclo[2.2.1]hept-5-ene-2,3-dione by Swern oxidation ofbicyclo[2.2.1]hept-5-ene-2,3-diol, and an unexpected ring-opening reaction by the Swern oxida-tion of pyrazine-fused congeners are described. Keywords: Swern oxidation, vicinal cis -diol, α-diketone, ring-opening, norbornene, pyrazine. Introduction Bicyclo[2.2.1]heptane skeletons have been a useful building block for the construction of molecular archi-tectures with a concavity [1]. In the course of our studies to synthesize a host molecule utilizing a negativeelectrostatic potential filed of pyrazine rings, a general method to prepare norobornene-2,3-dione and its py-razine-fused derivatives was required. We describe here an improved synthesis of bicyclo[2.2.1]hept-5-ene-2,3-dione ( 3 ) by Swern oxidation of bicyclo[2.2.1]hept-5-ene-2,3-diol ( 6 ). We also report that a similarSwern oxidation reaction of pyrazine-fused congeners 10 and 11 was found to undergo an unexpected rring-opening reaction.
Samson A. Jenekhe - One of the best experts on this subject based on the ideXlab platform.
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conjugated donor acceptor copolymer semiconductors synthesis optical properties electrochemistry and field effect carrier mobility of pyridopyrazine based copolymers
Macromolecules, 2008Co-Authors: Peitzu Wu, Richard D Champion, Samson A. JenekheAbstract:Five conjugated pyrido[3,4-b]pyrazine-based donor−acceptor copolymers were synthesized by Suzuki and Stille coupling polymerizations, and their photophysical and electrochemical properties and field-effect carrier mobilities were characterized. The copolymer semiconductors include poly(pyrido[3,4-b]pyrazine-alt-9,9-dioctyl-2,7-fluorene) (PPPzF), poly(thiophene-2,5-diyl-alt-2,3-diheptyl-pyrido[3,4-b]pyrazine-5,8-diyl) (PTHPPz), poly(thiophene-2,5-diyl-alt-2,3-didecyl-pyrido[3,4-b]pyrazine-5,8-diyl) (PTDPPz), poly(5,8-bis(4-dodecyl-thiophen-2-yl)-2,3-dioctyl-pyrido[3,4-b]pyrazine-alt-2,5-thiophene) (P3TPPz), and poly(5,8-bis(4-dodecyl-thiophen-2-yl)-2,3-dioctyl-pyrido[3,4-b]pyrazine-alt-9,9-dioctyl-2,7-fluorene) (P2TPPzF). Those soluble in tetrahydrofuran have moderate weight-average molecular weights (19 700−70 400 g/mol). The copolymers have tunable optical absorption bands in the visible region with absorption maxima at 323−588 nm and optical band gaps of 1.75−2.48 eV. Ambipolar redox properties with ion...
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conjugated donor acceptor copolymer semiconductors with large intramolecular charge transfer synthesis optical properties electrochemistry and field effect carrier mobility of thienopyrazine based copolymers
Macromolecules, 2006Co-Authors: Yan Zhu, Richard D Champion, Samson A. JenekheAbstract:Several conjugated thieno[3,4-b]pyrazine-based donor−acceptor copolymers were synthesized by Stille and Suzuki copolymerizations, and their optical, electrochemical, and field-effect charge transport properties were characterized. The new copolymers, poly(5,7-bis(3-dodecylthiophen-2-yl)thieno[3,4-b]pyrazine) (BTTP), poly(5,7-bis(3-dodecylthiophen-2-yl)thieno[3,4-b]pyrazine-alt-2,5-thiophene) (BTTP-T), poly(5,7-bis(3-dodecylthiophen-2-yl)thieno[3,4-b]pyrazine-alt-9,9-dioctyl-2,7-fluorene) (BTTP-F), and poly(5,7-bis(3-dodecylthiophen-2-yl)thieno[3,4-b]pyrazine-alt-1,4-bis(decyloxy)phenylene) (BTTP-P), had moderate to high molecular weights, broad optical absorption bands that extend into the near-infrared region with absorption maxima at 667−810 nm, and small optical band gaps (1.1−1.6 eV). They showed ambipolar redox properties with low ionization potentials (HOMO levels) of 4.6−5.04 eV. The field-effect mobility of holes varied from 4.2 × 10-4 cm2/(V s) in BTTP-T to 1.6 × 10-3 cm2/(V s) in BTTP-F. These r...
Henry Fadamiro - One of the best experts on this subject based on the ideXlab platform.
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phorid fly pseudacteon tricuspis response to alkylpyrazine analogs of a fire ant solenopsis invicta alarm pheromone
Journal of Insect Physiology, 2011Co-Authors: Kavita R Sharma, Robert Vander K Meer, Henry FadamiroAbstract:Abstract The phorid fly, Pseudacteon tricuspis Borgmeier, is a parasitoid of the red imported fire ant, Solenopsis invicta Buren. This fly has been reported to use fire ant chemicals, specifically venom alkaloids and possibly alarm pheromone to locate its host. A recent study identified 2-ethyl-3,6-dimethyl pyrazine as a component of the alarm pheromone of S. invicta. To determine the possible involvement of this fire ant alarm pheromone component in mediating fire ant-phorid fly interactions, we tested electroantennogram (EAG) and behavioral responses of P. tricuspis females to the commercially available mixture of 2-ethyl-3,6-dimethyl pyrazine and its 3,5-dimethyl isomer, as well as six structurally related alkylpyrazine analogs at varying doses. Pseudacteon tricuspis females showed significant EAG response to 2-ethyl-3,6(or 5)-dimethyl pyrazine (herein referred to as pheromone-isomer) at all doses, 0.001–10 μg. Among the tested alkylpyrazine analogs, 2,3-diethyl-5-methyl pyrazine showed significant EAG activity at 0.1 and 1 μg. 2,3-dimethyl pyrazine also showed significant EAG activity at 0.1 μg. Results of four-choice olfactometer bioassays demonstrated significant attraction of P. tricuspis females to the pheromone-isomer (2-ethyl-3,6(or 5)-dimethyl pyrazine) at all tested doses (0.01, 0.1, 1 and 10 μg). The analogs, 2,3-diethyl-5-methyl pyrazine and 2,3-dimethyl pyrazine were significantly better than the control at the higher doses (0.1, 1 and 10 μg). The pheromone-isomer was significantly better than both analogs at two doses, 0.1 and 1 μg. These results confirm that the reported fire ant alarm pheromone component plays a role in mediating attraction of phorid flies to host workers. Venom alkaloids were previously shown to attract P. tricuspis ; therefore, we propose that fire ant alarm pheromones may act in tandem or synergistically with venom alkaloids to attract phorid fly parasitoids to fire ant workers.
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phorid fly pseudacteon tricuspis response to alkylpyrazine analogs of a fire ant solenopsis invicta alarm pheromone
Journal of Insect Physiology, 2011Co-Authors: Kavita R Sharma, Robert Vander K Meer, Henry FadamiroAbstract:Abstract The phorid fly, Pseudacteon tricuspis Borgmeier, is a parasitoid of the red imported fire ant, Solenopsis invicta Buren. This fly has been reported to use fire ant chemicals, specifically venom alkaloids and possibly alarm pheromone to locate its host. A recent study identified 2-ethyl-3,6-dimethyl pyrazine as a component of the alarm pheromone of S. invicta. To determine the possible involvement of this fire ant alarm pheromone component in mediating fire ant-phorid fly interactions, we tested electroantennogram (EAG) and behavioral responses of P. tricuspis females to the commercially available mixture of 2-ethyl-3,6-dimethyl pyrazine and its 3,5-dimethyl isomer, as well as six structurally related alkylpyrazine analogs at varying doses. Pseudacteon tricuspis females showed significant EAG response to 2-ethyl-3,6(or 5)-dimethyl pyrazine (herein referred to as pheromone-isomer) at all doses, 0.001–10 μg. Among the tested alkylpyrazine analogs, 2,3-diethyl-5-methyl pyrazine showed significant EAG activity at 0.1 and 1 μg. 2,3-dimethyl pyrazine also showed significant EAG activity at 0.1 μg. Results of four-choice olfactometer bioassays demonstrated significant attraction of P. tricuspis females to the pheromone-isomer (2-ethyl-3,6(or 5)-dimethyl pyrazine) at all tested doses (0.01, 0.1, 1 and 10 μg). The analogs, 2,3-diethyl-5-methyl pyrazine and 2,3-dimethyl pyrazine were significantly better than the control at the higher doses (0.1, 1 and 10 μg). The pheromone-isomer was significantly better than both analogs at two doses, 0.1 and 1 μg. These results confirm that the reported fire ant alarm pheromone component plays a role in mediating attraction of phorid flies to host workers. Venom alkaloids were previously shown to attract P. tricuspis ; therefore, we propose that fire ant alarm pheromones may act in tandem or synergistically with venom alkaloids to attract phorid fly parasitoids to fire ant workers.
Tomoshige Kobayashi - One of the best experts on this subject based on the ideXlab platform.
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swern oxidation of bicyclo 2 2 1 hept 5 ene 2 3 diol and its pyrazine fused derivatives an improved synthesis of bicyclo 2 2 1 hept 5 ene 2 3 dione and an unexpected ring opening reaction
Molecules, 2000Co-Authors: Tomoshige Kobayashi, Sayuri KobayashiAbstract:Abstract: An improved synthesis of bicyclo[2.2.1]hept-5-ene-2,3-dione by Swern oxidation ofbicyclo[2.2.1]hept-5-ene-2,3-diol, and an unexpected ring-opening reaction by the Swern oxida-tion of pyrazine-fused congeners are described. Keywords: Swern oxidation, vicinal cis -diol, α-diketone, ring-opening, norbornene, pyrazine. Introduction Bicyclo[2.2.1]heptane skeletons have been a useful building block for the construction of molecular archi-tectures with a concavity [1]. In the course of our studies to synthesize a host molecule utilizing a negativeelectrostatic potential filed of pyrazine rings, a general method to prepare norobornene-2,3-dione and its py-razine-fused derivatives was required. We describe here an improved synthesis of bicyclo[2.2.1]hept-5-ene-2,3-dione ( 3 ) by Swern oxidation of bicyclo[2.2.1]hept-5-ene-2,3-diol ( 6 ). We also report that a similarSwern oxidation reaction of pyrazine-fused congeners 10 and 11 was found to undergo an unexpected rring-opening reaction.
