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Jaan Laane - One of the best experts on this subject based on the ideXlab platform.
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Anomeric Effect in Five-Membered Ring Molecules: Comparison of Theoretical Computations and Experimental Spectroscopic Results.
The journal of physical chemistry. A, 2020Co-Authors: Esther J. Ocola, Jaan LaaneAbstract:As demonstrated in previous spectroscopic studies of 1,3-dioxole [ J. Am. Chem. Soc., 1993, 115, 12132-12136] and 1,3-Benzodioxole [ J. Am. Chem. Soc., 1999, 121, 5056-5062], analysis of the ring-puckering potential energy function (PEF) of a "pseudo-four-membered ring" molecule can provide insight into understanding the magnitude of the anomeric effect. In the present study, high-level CCSD/cc-pVTZ and somewhat lower-level MP2/cc-pVTZ ab initio computations have been utilized to calculate the PEFs for 1,3-dioxole and 1,3-Benzodioxole and 10 related molecules containing sulfur and selenium atoms and possessing the anomeric effect. The potential energy parameters derived for the PEFs directly provide a comparison of the relative magnitudes of the anomeric effect for molecules possessing OCO, OCS, OCSe, SCS, SCSe, and SeCSe linkages. The torsional potential energies produced by the anomeric effect for these linkages were estimated to range from 5.97 to 1.91 kcal/mol. The ab initio calculations also yielded the structural parameters, barriers to planarity, and ring-puckering angles for each of the 12 molecules studied. Based on the refined structural parameters for 1,3-dioxole and 1,3-Benzodioxole, improved PEFs for these molecules were also calculated. The calculations also support the conclusion that the relatively low barrier to planarity of 1,3-Benzodioxole results from competitive interactions between its benzene ring and the oxygen atom p orbitals.
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spectroscopic determination of the vibrational potential energy surface and conformation of 1 3 Benzodioxole in its s1 π π excited state the effect of the electronic excitation on the anomeric effect
Journal of the American Chemical Society, 2000Co-Authors: Jaan Laane, Sachie Sakurai, Eugene Bondoc, Kevin Morris, And Niklas Meinander, Jaebum ChooAbstract:The electronic absorption spectra and the laser-induced fluorescence spectra of supersonic-jet-cooled 1,3-Benzodioxole molecules have been investigated to map out the vibronic energy levels in the ...
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Vibrational potential energy surfaces for phthalan and 1,3-Benzodioxole in their S0 and S1(π,π*) states
Journal of Molecular Structure, 1999Co-Authors: Jaan Laane, Sachie Sakurai, T. D. Klots, Niklas Meinander, Kevin F. Morris, Whe-yi Chiang, Eugene BondocAbstract:Abstract The far-infrared, Raman and ultraviolet spectra of phthalan and 1,3-Benzodioxole were recorded and analyzed. In addition, the fluorescence excitation spectra and the dispersed fluorescence spectra of the jet-cooled molecules were also investigated. The far-infrared spectrum of phthalan shows single, double, and triple quantum jump transitions between the various ring-puckering energy levels. Many hot bands involving the ring-puckering and ring-flapping vibrations were also observed. The ring-puckering energy level spacings possess an irregular pattern and calculations show this to arise from the kinetic energy interactions between the puckering and flapping vibrations. A two-dimensional potential energy surface, which nicely fits all the observed data, was determined. This has a barrier to planarity of 35 cm−1. Dispersed fluorescence spectra of jet-cooled phthalan molecules helped to confirm the far-infrared assignments, and the fluorescence excitation spectra were recorded to determine the vibrational energy levels from the puckering in the S1(π,π*) electronic excited state. Ultraviolet absorption spectra were used to better understand the excited state energy levels. The far-infrared spectra of 1,3-Benzodioxole were also reanalyzed. Because of the anomeric effect, 1,3-Benzodioxole is puckered with a barrier to planarity of 125 cm−1. Analysis of the ultraviolet absorption spectra and the fluorescence excitation spectra of the jet-cooled molecules is also in progress and shows that the barrier increases in the S1(π,π*) state.
Jaebum Choo - One of the best experts on this subject based on the ideXlab platform.
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Conformations of phthalan and 1,3-Benzodioxole in their S0 and S1(π,π∗) electronic states: theoretical study
Journal of Molecular Structure, 2001Co-Authors: Jaebum ChooAbstract:Abstract Theoretical ab initio calculations using the HF, B3LYP, MP2, CIS and td-B3LYP methods have been performed in order to investigate the structural features of phthalan and 1,3-Benzodioxole in their S 0 and S 1 (π,π ∗ ) electronic states. The calculated results predict that S 0 →S 1 electronic excitation leads to considerable changes of their structural properties due to the decrease of π electron character in the S 1 state. Extensive comparisons are made with the previously reported far-infrared, Raman and laser-induced fluorescence excitation spectra, and a reasonable agreement has been achieved. Natural bond orbital analysis has also been carried out in order to explain why the five-membered ring of 1,3-Benzodioxole should have more puckered configuration in the S 1 state. Our ab initio calculations, performed for the S 0 and S 1 states, not only strongly support the recently reported experimental results but also explain the theoretical basis for the conformational preferences of phthalan and 1,3-Benzodioxole.
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conformational stabilization of 1 3 Benzodioxole anomeric effect by natural bond orbital analysis
Journal of Physical Chemistry A, 2001Co-Authors: Seongho Moon, Younghi Kwon, Jaebum Lee, Jaebum ChooAbstract:The conformation of 1,3-Benzodioxole has been examined using ab initio calculation and natural bond orbital (NBO) analysis in order to find the origin of its unusual nonplanarity. Geometry optimizations for the planar (C2V) and flap-puckered (Cs) conformers of 1,3-Benzodioxole have been performed at the HF, B3LYP, and MP2 levels, and the results indicate that the flap-puckerd conformer is more stable than the planar conformer. High-level electron correlation treatments with extended basis sets have also been performed to provide a reliable prediction of the puckering barrier for 1,3-Benzodioxole. The calculated puckering barrier appears to be in reasonable agreement with the experiment, but the divergent behavior of the Moller-Plesset series suggests that it is impossible with conventional basis sets smaller than 400 functions to converge the barrier height. NBO analysis of the Hartree-Fock wave functions shows that the conformational preference of the Cs conformer over the C2V is the result of a wide variety of hyperconjugative orbital interactions, but the interaction between the oxygen lone pair (np) and the U*CO orbital, which is closely associated with the anomeric effect, is the most important factor favoring the nonplanar conformation. However, 1,3-Benzodioxole has a lower puckering barrier to planarity than 1,3-dioxole due to the suppression of the anomeric effect by the benzene ring.
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spectroscopic determination of the vibrational potential energy surface and conformation of 1 3 Benzodioxole in its s1 π π excited state the effect of the electronic excitation on the anomeric effect
Journal of the American Chemical Society, 2000Co-Authors: Jaan Laane, Sachie Sakurai, Eugene Bondoc, Kevin Morris, And Niklas Meinander, Jaebum ChooAbstract:The electronic absorption spectra and the laser-induced fluorescence spectra of supersonic-jet-cooled 1,3-Benzodioxole molecules have been investigated to map out the vibronic energy levels in the ...
Eugene Bondoc - One of the best experts on this subject based on the ideXlab platform.
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spectroscopic determination of the vibrational potential energy surface and conformation of 1 3 Benzodioxole in its s1 π π excited state the effect of the electronic excitation on the anomeric effect
Journal of the American Chemical Society, 2000Co-Authors: Jaan Laane, Sachie Sakurai, Eugene Bondoc, Kevin Morris, And Niklas Meinander, Jaebum ChooAbstract:The electronic absorption spectra and the laser-induced fluorescence spectra of supersonic-jet-cooled 1,3-Benzodioxole molecules have been investigated to map out the vibronic energy levels in the ...
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Vibrational potential energy surfaces for phthalan and 1,3-Benzodioxole in their S0 and S1(π,π*) states
Journal of Molecular Structure, 1999Co-Authors: Jaan Laane, Sachie Sakurai, T. D. Klots, Niklas Meinander, Kevin F. Morris, Whe-yi Chiang, Eugene BondocAbstract:Abstract The far-infrared, Raman and ultraviolet spectra of phthalan and 1,3-Benzodioxole were recorded and analyzed. In addition, the fluorescence excitation spectra and the dispersed fluorescence spectra of the jet-cooled molecules were also investigated. The far-infrared spectrum of phthalan shows single, double, and triple quantum jump transitions between the various ring-puckering energy levels. Many hot bands involving the ring-puckering and ring-flapping vibrations were also observed. The ring-puckering energy level spacings possess an irregular pattern and calculations show this to arise from the kinetic energy interactions between the puckering and flapping vibrations. A two-dimensional potential energy surface, which nicely fits all the observed data, was determined. This has a barrier to planarity of 35 cm−1. Dispersed fluorescence spectra of jet-cooled phthalan molecules helped to confirm the far-infrared assignments, and the fluorescence excitation spectra were recorded to determine the vibrational energy levels from the puckering in the S1(π,π*) electronic excited state. Ultraviolet absorption spectra were used to better understand the excited state energy levels. The far-infrared spectra of 1,3-Benzodioxole were also reanalyzed. Because of the anomeric effect, 1,3-Benzodioxole is puckered with a barrier to planarity of 125 cm−1. Analysis of the ultraviolet absorption spectra and the fluorescence excitation spectra of the jet-cooled molecules is also in progress and shows that the barrier increases in the S1(π,π*) state.
Sachie Sakurai - One of the best experts on this subject based on the ideXlab platform.
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spectroscopic determination of the vibrational potential energy surface and conformation of 1 3 Benzodioxole in its s1 π π excited state the effect of the electronic excitation on the anomeric effect
Journal of the American Chemical Society, 2000Co-Authors: Jaan Laane, Sachie Sakurai, Eugene Bondoc, Kevin Morris, And Niklas Meinander, Jaebum ChooAbstract:The electronic absorption spectra and the laser-induced fluorescence spectra of supersonic-jet-cooled 1,3-Benzodioxole molecules have been investigated to map out the vibronic energy levels in the ...
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Vibrational potential energy surfaces for phthalan and 1,3-Benzodioxole in their S0 and S1(π,π*) states
Journal of Molecular Structure, 1999Co-Authors: Jaan Laane, Sachie Sakurai, T. D. Klots, Niklas Meinander, Kevin F. Morris, Whe-yi Chiang, Eugene BondocAbstract:Abstract The far-infrared, Raman and ultraviolet spectra of phthalan and 1,3-Benzodioxole were recorded and analyzed. In addition, the fluorescence excitation spectra and the dispersed fluorescence spectra of the jet-cooled molecules were also investigated. The far-infrared spectrum of phthalan shows single, double, and triple quantum jump transitions between the various ring-puckering energy levels. Many hot bands involving the ring-puckering and ring-flapping vibrations were also observed. The ring-puckering energy level spacings possess an irregular pattern and calculations show this to arise from the kinetic energy interactions between the puckering and flapping vibrations. A two-dimensional potential energy surface, which nicely fits all the observed data, was determined. This has a barrier to planarity of 35 cm−1. Dispersed fluorescence spectra of jet-cooled phthalan molecules helped to confirm the far-infrared assignments, and the fluorescence excitation spectra were recorded to determine the vibrational energy levels from the puckering in the S1(π,π*) electronic excited state. Ultraviolet absorption spectra were used to better understand the excited state energy levels. The far-infrared spectra of 1,3-Benzodioxole were also reanalyzed. Because of the anomeric effect, 1,3-Benzodioxole is puckered with a barrier to planarity of 125 cm−1. Analysis of the ultraviolet absorption spectra and the fluorescence excitation spectra of the jet-cooled molecules is also in progress and shows that the barrier increases in the S1(π,π*) state.
Rolf Meyer - One of the best experts on this subject based on the ideXlab platform.
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the anomeric effect in 1 3 Benzodioxole additional evidence from the rotational vibration rotation and rovibronic spectra
Physical Chemistry Chemical Physics, 2004Co-Authors: Zbigniew Kisiel, L Pszczolkowski, Giangaetano Pietraperzia, Maurizio Becucci, Walther Caminati, Rolf MeyerAbstract:The millimetre wave pure rotation and vibration–rotation spectrum of 1,3-Benzodioxole has been studied and the vibrational spacing between the two lowest vibrational states in the five membered ring puckering potential has been determined with considerable accuracy, at ΔE01 = 259 726.035(10) MHz or 8.663 5280(4) cm−1. In addition, rotationally resolved analysis of two hot bands near the reported origin band in the laser-induced fluorescence spectrum has been carried out and was found to rule out the current literature assignment of this spectrum. The new information has been used to reassign the lowest vibrational transitions in the far-infrared and the Raman spectrum of 1,3-Benzodioxole in terms of a one dimensional potential with a central barrier of 108 cm−1, which successfully accounts for all states up to υ = 5, and for the observed variation in rotational constants. Considerable reassignment of the published spectra, as well as new experimental work is still necessary for a confident determination of the low-energy region of the molecular potential of 1,3-Benzodioxole.
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The anomeric effect in 1,3-Benzodioxole: additional evidence from the rotational, vibration–rotation and rovibronic spectra
Phys. Chem. Chem. Phys., 2004Co-Authors: Zbigniew Kisiel, Giangaetano Pietraperzia, Maurizio Becucci, Walther Caminati, Lech Pszczółkowski, Rolf MeyerAbstract:The millimetre wave pure rotation and vibration–rotation spectrum of 1,3-Benzodioxole has been studied and the vibrational spacing between the two lowest vibrational states in the five membered ring puckering potential has been determined with considerable accuracy, at ΔE01 = 259 726.035(10) MHz or 8.663 5280(4) cm−1. In addition, rotationally resolved analysis of two hot bands near the reported origin band in the laser-induced fluorescence spectrum has been carried out and was found to rule out the current literature assignment of this spectrum. The new information has been used to reassign the lowest vibrational transitions in the far-infrared and the Raman spectrum of 1,3-Benzodioxole in terms of a one dimensional potential with a central barrier of 108 cm−1, which successfully accounts for all states up to υ = 5, and for the observed variation in rotational constants. Considerable reassignment of the published spectra, as well as new experimental work is still necessary for a confident determination of the low-energy region of the molecular potential of 1,3-Benzodioxole.