The Experts below are selected from a list of 78 Experts worldwide ranked by ideXlab platform
Melanie Rademeyer - One of the best experts on this subject based on the ideXlab platform.
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Structures and trends of one-dimensional halide-bridged polymers of five-coordinate cadmium(II) and mercury(II) with Benzopyridine and -pyrazine-type N-donor ligands
CrystEngComm, 2020Co-Authors: Cara Slabbert, Melanie RademeyerAbstract:Cadmium and mercury dihalides were reacted with Benzopyridine- and benzopyrazine-type N-donor ligands as Lewis bases. The solid-state structures of 13 novel reaction products were studied by X-ray diffraction. Eleven of the structures can be classified as one-dimensional halide-bridged polymers of composition [M(μ-X)2(L)]∞, in which the metal ion displays a coordination number of five, while the remaining two structures exhibit one-dimensional dimers that are linked by long, semi-coordinate M–X⋯M–X interactions to form pseudo-halide-bridged polymers. Four of the structures contain Cd2+ as the metal ion, while the remaining nine have Hg2+ as the metal ion. Although all the halide-bridged polymers show a coordination number of five, two different metal cation geometries are displayed. A detailed comparison of all structural results, which includes related compounds from the literature and allows for the study of the effect of an increase in the width of the N-donor ligand on the halide-bridged chain geometries and other structural features, concludes the discussion.
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structures and trends of neutral mxxsolvent4 x tetrahedra and anionic mx4 2 tetrahalometallates of zinc ii cadmium ii and mercury ii with Benzopyridine and benzopyrazine type n donor ligands or cations
CrystEngComm, 2016Co-Authors: Cara Slabbert, Melanie RademeyerAbstract:Zinc, cadmium and mercury dihalides were reacted with Benzopyridine- and benzopyrazine-type N-donor molecules acridine (acr), phenazine (phe), quinoline (quin) and quinoxaline (quinox) as ligands or cations. The solid-state structures of 16 novel, zero-dimensional reaction products were studied by X-ray diffraction. Seven of the compounds were prepared in the presence of an inorganic acid, HX, which resulted in the formation of anionic tetrahalometallates, [MX4]2−, with either Cd2+ or Hg2+ as the cationic metal center and quinolinium (quin-H), quinoxalinium (quinox-H), acridinium (acr-H) or phenazinium (phe-H) as the counter cation. The other nine compounds contain Zn2+ as the tetrahedral cationic node. Five of the nine Zn2+ compounds are neutral, and four are ionic. Three of the four ionic Zn2+ compounds contain an anionic tetrahalometallate inorganic moiety, [ZnX4]2−, while the inorganic component of the fourth ionic Zn2+ compound is coordinated by three halido ligands and one aqua ligand, [ZnX3(H2O)]−. Structural trends, hydrogen bonding interactions and aromatic interactions are identified. In addition, it is observed that in the case of the neutral phenazine or acridine compounds, the size of the organic molecule prevents coordination of the molecule to the metal ion.
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Structures and trends of neutral MXxsolvent4−x tetrahedra and anionic [MX4]2− tetrahalometallates of zinc(II), cadmium(II) and mercury(II) with Benzopyridine- and benzopyrazine-type N-donor ligands or cations
CrystEngComm, 2016Co-Authors: Cara Slabbert, Melanie RademeyerAbstract:Zinc, cadmium and mercury dihalides were reacted with Benzopyridine- and benzopyrazine-type N-donor molecules acridine (acr), phenazine (phe), quinoline (quin) and quinoxaline (quinox) as ligands or cations. The solid-state structures of 16 novel, zero-dimensional reaction products were studied by X-ray diffraction. Seven of the compounds were prepared in the presence of an inorganic acid, HX, which resulted in the formation of anionic tetrahalometallates, [MX4]2−, with either Cd2+ or Hg2+ as the cationic metal center and quinolinium (quin-H), quinoxalinium (quinox-H), acridinium (acr-H) or phenazinium (phe-H) as the counter cation. The other nine compounds contain Zn2+ as the tetrahedral cationic node. Five of the nine Zn2+ compounds are neutral, and four are ionic. Three of the four ionic Zn2+ compounds contain an anionic tetrahalometallate inorganic moiety, [ZnX4]2−, while the inorganic component of the fourth ionic Zn2+ compound is coordinated by three halido ligands and one aqua ligand, [ZnX3(H2O)]−. Structural trends, hydrogen bonding interactions and aromatic interactions are identified. In addition, it is observed that in the case of the neutral phenazine or acridine compounds, the size of the organic molecule prevents coordination of the molecule to the metal ion.
Cara Slabbert - One of the best experts on this subject based on the ideXlab platform.
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Structures and trends of one-dimensional halide-bridged polymers of five-coordinate cadmium(II) and mercury(II) with Benzopyridine and -pyrazine-type N-donor ligands
CrystEngComm, 2020Co-Authors: Cara Slabbert, Melanie RademeyerAbstract:Cadmium and mercury dihalides were reacted with Benzopyridine- and benzopyrazine-type N-donor ligands as Lewis bases. The solid-state structures of 13 novel reaction products were studied by X-ray diffraction. Eleven of the structures can be classified as one-dimensional halide-bridged polymers of composition [M(μ-X)2(L)]∞, in which the metal ion displays a coordination number of five, while the remaining two structures exhibit one-dimensional dimers that are linked by long, semi-coordinate M–X⋯M–X interactions to form pseudo-halide-bridged polymers. Four of the structures contain Cd2+ as the metal ion, while the remaining nine have Hg2+ as the metal ion. Although all the halide-bridged polymers show a coordination number of five, two different metal cation geometries are displayed. A detailed comparison of all structural results, which includes related compounds from the literature and allows for the study of the effect of an increase in the width of the N-donor ligand on the halide-bridged chain geometries and other structural features, concludes the discussion.
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structures and trends of neutral mxxsolvent4 x tetrahedra and anionic mx4 2 tetrahalometallates of zinc ii cadmium ii and mercury ii with Benzopyridine and benzopyrazine type n donor ligands or cations
CrystEngComm, 2016Co-Authors: Cara Slabbert, Melanie RademeyerAbstract:Zinc, cadmium and mercury dihalides were reacted with Benzopyridine- and benzopyrazine-type N-donor molecules acridine (acr), phenazine (phe), quinoline (quin) and quinoxaline (quinox) as ligands or cations. The solid-state structures of 16 novel, zero-dimensional reaction products were studied by X-ray diffraction. Seven of the compounds were prepared in the presence of an inorganic acid, HX, which resulted in the formation of anionic tetrahalometallates, [MX4]2−, with either Cd2+ or Hg2+ as the cationic metal center and quinolinium (quin-H), quinoxalinium (quinox-H), acridinium (acr-H) or phenazinium (phe-H) as the counter cation. The other nine compounds contain Zn2+ as the tetrahedral cationic node. Five of the nine Zn2+ compounds are neutral, and four are ionic. Three of the four ionic Zn2+ compounds contain an anionic tetrahalometallate inorganic moiety, [ZnX4]2−, while the inorganic component of the fourth ionic Zn2+ compound is coordinated by three halido ligands and one aqua ligand, [ZnX3(H2O)]−. Structural trends, hydrogen bonding interactions and aromatic interactions are identified. In addition, it is observed that in the case of the neutral phenazine or acridine compounds, the size of the organic molecule prevents coordination of the molecule to the metal ion.
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Structures and trends of neutral MXxsolvent4−x tetrahedra and anionic [MX4]2− tetrahalometallates of zinc(II), cadmium(II) and mercury(II) with Benzopyridine- and benzopyrazine-type N-donor ligands or cations
CrystEngComm, 2016Co-Authors: Cara Slabbert, Melanie RademeyerAbstract:Zinc, cadmium and mercury dihalides were reacted with Benzopyridine- and benzopyrazine-type N-donor molecules acridine (acr), phenazine (phe), quinoline (quin) and quinoxaline (quinox) as ligands or cations. The solid-state structures of 16 novel, zero-dimensional reaction products were studied by X-ray diffraction. Seven of the compounds were prepared in the presence of an inorganic acid, HX, which resulted in the formation of anionic tetrahalometallates, [MX4]2−, with either Cd2+ or Hg2+ as the cationic metal center and quinolinium (quin-H), quinoxalinium (quinox-H), acridinium (acr-H) or phenazinium (phe-H) as the counter cation. The other nine compounds contain Zn2+ as the tetrahedral cationic node. Five of the nine Zn2+ compounds are neutral, and four are ionic. Three of the four ionic Zn2+ compounds contain an anionic tetrahalometallate inorganic moiety, [ZnX4]2−, while the inorganic component of the fourth ionic Zn2+ compound is coordinated by three halido ligands and one aqua ligand, [ZnX3(H2O)]−. Structural trends, hydrogen bonding interactions and aromatic interactions are identified. In addition, it is observed that in the case of the neutral phenazine or acridine compounds, the size of the organic molecule prevents coordination of the molecule to the metal ion.
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the many facets of mercury ii in one dimensional halide bridged polymers of d 10 metal cations with n Benzopyridine and pyrazine type ligands
Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie, 2015Co-Authors: Cara SlabbertAbstract:The many facets of mercury(II) in one-dimensional halide-bridged polymers of d10 metal cations with N-Benzopyridine and pyrazine type ligands. Divalent d10 metal halides were systematically combined with different N-donor ligands in order to elucidate structural trends. This was accomplished successfully by using zinc(II) or cadmium(II) as metal centre, but not mercury(II). The exotic and diverse mercury(II) structures form the subject of the current presentation.
Enyew A. Bayle - One of the best experts on this subject based on the ideXlab platform.
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Modeling the transition state structure to probe a reaction mechanism on the oxidation of quinoline by quinoline 2-oxidoreductase
Chemistry Central Journal, 2016Co-Authors: Enyew A. BayleAbstract:Background Quinoline 2-oxidoreductase (Qor) is a member of molybdenum hydroxylase which catalyzes the oxidation of quinoline (2, 3 Benzopyridine) to 1-hydro-2-oxoquinoline. Qor has biological and medicinal significances. Qor is known to metabolize drugs produced from quinoline for the treatment of malaria, arthritis, and lupus for many years. However, the mechanistic action by which Qor oxidizes quinoline has not been investigated either experimentally or theoretically. Purpose of the study The present study was intended to determine the interaction site of quinoline, predict the transition state structure, and probe a plausible mechanistic route for the oxidative hydroxylation of quinoline in the reductive half-reaction active site of Qor. Results Density functional theory calculations have been carried out in order to understand the events taking place during the oxidative hydroxylation of quinoline in the reductive half-reaction active site of Qor. The most electropositivity and the lowest percentage contribution to the HOMO are shown at C_2 of quinoline compared to the other carbon atoms. The transition state structure of quinoline bound to the active site has been confirmed by one imaginary negative frequency of −104.500/s and −1.2365899E+06 transition state energies. The Muliken atomic charges, the bond distances, and the bond order profiles were determined to characterize the transition state structure and the reaction mechanism. Conclusion The results have shown that C_2 is the preferred locus of interaction of quinoline to interact with the active site of Qor. The transition state structure of quinoline bound to the active site has been confirmed by one imaginary negative frequency. Moreover, the presence of partial negative charges on hydrogen at the transitions state suggested hydride transfer. Similarly, results obtained from total energy, iconicity and molecular orbital analyses supported a concerted reaction mechanism.
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Modeling the transition state structure to probe a reaction mechanism on the oxidation of quinoline by quinoline 2-oxidoreductase.
Chemistry Central Journal, 2016Co-Authors: Enyew A. BayleAbstract:Quinoline 2-oxidoreductase (Qor) is a member of molybdenum hydroxylase which catalyzes the oxidation of quinoline (2, 3 Benzopyridine) to 1-hydro-2-oxoquinoline. Qor has biological and medicinal significances. Qor is known to metabolize drugs produced from quinoline for the treatment of malaria, arthritis, and lupus for many years. However, the mechanistic action by which Qor oxidizes quinoline has not been investigated either experimentally or theoretically. The present study was intended to determine the interaction site of quinoline, predict the transition state structure, and probe a plausible mechanistic route for the oxidative hydroxylation of quinoline in the reductive half-reaction active site of Qor. Density functional theory calculations have been carried out in order to understand the events taking place during the oxidative hydroxylation of quinoline in the reductive half-reaction active site of Qor. The most electropositivity and the lowest percentage contribution to the HOMO are shown at C2 of quinoline compared to the other carbon atoms. The transition state structure of quinoline bound to the active site has been confirmed by one imaginary negative frequency of −104.500/s and −1.2365899E+06 transition state energies. The Muliken atomic charges, the bond distances, and the bond order profiles were determined to characterize the transition state structure and the reaction mechanism. The results have shown that C2 is the preferred locus of interaction of quinoline to interact with the active site of Qor. The transition state structure of quinoline bound to the active site has been confirmed by one imaginary negative frequency. Moreover, the presence of partial negative charges on hydrogen at the transitions state suggested hydride transfer. Similarly, results obtained from total energy, iconicity and molecular orbital analyses supported a concerted reaction mechanism.
Cristina Puzzarini - One of the best experts on this subject based on the ideXlab platform.
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Organic chemistry in Titan׳s upper atmosphere and its astrobiological consequences: I. Views towards Cassini plasma spectrometer (CAPS) and ion neutral mass spectrometer (INMS) experiments in space
Planetary and Space Science, 2020Co-Authors: E C Sittler, D Chornay, B R Rowe, Cristina PuzzariniAbstract:International audienceThe discovery of carbocations and carbanions by Ion Neutral Mass Spectrometer (INMS) and the Cassini Plasma Spectrometer (CAPS) instruments onboard the Cassini spacecraft in Titan׳s upper atmosphere is truly amazing for astrochemists and astrobiologists. In this paper we identify the reaction mechanisms for the growth of the complex macromolecules observed by the CAPS Ion Beam Spectrometer (IBS) and Electron Spectrometer (ELS). This identification is based on a recently published paper (Ali et al., 2013. Planet. Space Sci. 87, 96) which emphasizes the role of Olah׳s nonclassical carbonium ion chemistry in the synthesis of the organic molecules observed in Titan׳s thermosphere and ionosphere by INMS. The main conclusion of that work was the demonstration of the presence of the cyclopropenyl cation – the simplest Huckel׳s aromatic molecule – and its cyclic methyl derivatives in Titan׳s atmosphere at high altitudes. In this study, we present the transition from simple aromatic molecules to the complex ortho-bridged bi- and tri-cyclic hydrocarbons, e.g., CH2+ mono-substituted naphthalene and phenanthrene, as well as the ortho- and peri-bridged tri-cyclic aromatic ring, e.g., perinaphthenyl cation. These rings could further grow into tetra-cyclic and the higher order ring polymers in Titan׳s upper atmosphere. Contrary to the pre-Cassini observations, the nitrogen chemistry of Titan׳s upper atmosphere is found to be extremely rich. A variety of N-containing hydrocarbons including the N-heterocycles where a CH group in the polycyclic rings mentioned above is replaced by an N atom, e.g., CH2+ substituted derivative of quinoline (Benzopyridine), are found to be dominant in Titan׳s upper atmosphere. The mechanisms for the formation of complex molecular anions are discussed as well. It is proposed that many closed-shell complex carbocations after their formation first, in Titan׳s upper atmosphere, undergo the kinetics of electron recombination to form open-shell neutral radicals. These radical species subsequently might form carbanions via radiative electron attachment at low temperatures with thermal electrons. The classic example is the perinaphthenyl anion in Titan׳s upper atmosphere. Therefore, future astronomical observations of selected carbocations and corresponding carbanions are required to settle the key issue of molecular anion chemistry on Titan. Other than earth, Titan is the only planetary body in our solar system that is known to have reservoirs of permanent liquids on its surface. The synthesis of complex biomolecules either by organic catalysis of precipitated solutes “on hydrocarbon solvent” on Titan or through the solvation process indeed started in its upper atmosphere. The most notable examples in Titan׳s prebiotic atmospheric chemistry are conjugated and aromatic polycyclic molecules, N-heterocycles including the presence of imino >CN–H functional group in the carbonium chemistry. Our major conclusion in this paper is that the synthesis of organic compounds in Titan׳s upper atmosphere is a direct consequence of the chemistry of carbocations involving the ion–molecule reactions. The observations of complexity in the organic chemistry on Titan from the Cassini–Huygens mission clearly indicate that Titan is so far the only planetary object in our solar system that will most likely provide an answer to the question of the synthesis of complex biomolecules on the primitive earth and the origin of lif
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organic chemistry in titan s upper atmosphere and its astrobiological consequences i views towards cassini plasma spectrometer caps and ion neutral mass spectrometer inms experiments in space
Planetary and Space Science, 2015Co-Authors: E C Sittler, D Chornay, B R Rowe, Cristina PuzzariniAbstract:Abstract The discovery of carbocations and carbanions by Ion Neutral Mass Spectrometer (INMS) and the Cassini Plasma Spectrometer (CAPS) instruments onboard the Cassini spacecraft in Titan׳s upper atmosphere is truly amazing for astrochemists and astrobiologists. In this paper we identify the reaction mechanisms for the growth of the complex macromolecules observed by the CAPS Ion Beam Spectrometer (IBS) and Electron Spectrometer (ELS). This identification is based on a recently published paper (Ali et al., 2013. Planet. Space Sci. 87, 96) which emphasizes the role of Olah׳s nonclassical carbonium ion chemistry in the synthesis of the organic molecules observed in Titan׳s thermosphere and ionosphere by INMS. The main conclusion of that work was the demonstration of the presence of the cyclopropenyl cation – the simplest Huckel׳s aromatic molecule – and its cyclic methyl derivatives in Titan׳s atmosphere at high altitudes. In this study, we present the transition from simple aromatic molecules to the complex ortho-bridged bi- and tri-cyclic hydrocarbons, e.g., CH2+ mono-substituted naphthalene and phenanthrene, as well as the ortho- and peri-bridged tri-cyclic aromatic ring, e.g., perinaphthenyl cation. These rings could further grow into tetra-cyclic and the higher order ring polymers in Titan׳s upper atmosphere. Contrary to the pre-Cassini observations, the nitrogen chemistry of Titan׳s upper atmosphere is found to be extremely rich. A variety of N-containing hydrocarbons including the N-heterocycles where a CH group in the polycyclic rings mentioned above is replaced by an N atom, e.g., CH2+ substituted derivative of quinoline (Benzopyridine), are found to be dominant in Titan׳s upper atmosphere. The mechanisms for the formation of complex molecular anions are discussed as well. It is proposed that many closed-shell complex carbocations after their formation first, in Titan׳s upper atmosphere, undergo the kinetics of electron recombination to form open-shell neutral radicals. These radical species subsequently might form carbanions via radiative electron attachment at low temperatures with thermal electrons. The classic example is the perinaphthenyl anion in Titan׳s upper atmosphere. Therefore, future astronomical observations of selected carbocations and corresponding carbanions are required to settle the key issue of molecular anion chemistry on Titan. Other than earth, Titan is the only planetary body in our solar system that is known to have reservoirs of permanent liquids on its surface. The synthesis of complex biomolecules either by organic catalysis of precipitated solutes “on hydrocarbon solvent” on Titan or through the solvation process indeed started in its upper atmosphere. The most notable examples in Titan׳s prebiotic atmospheric chemistry are conjugated and aromatic polycyclic molecules, N-heterocycles including the presence of imino >C N–H functional group in the carbonium chemistry. Our major conclusion in this paper is that the synthesis of organic compounds in Titan׳s upper atmosphere is a direct consequence of the chemistry of carbocations involving the ion–molecule reactions. The observations of complexity in the organic chemistry on Titan from the Cassini–Huygens mission clearly indicate that Titan is so far the only planetary object in our solar system that will most likely provide an answer to the question of the synthesis of complex biomolecules on the primitive earth and the origin of life.
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Organic chemistry in Titan׳s upper atmosphere and its astrobiological consequences: I. Views towards Cassini plasma spectrometer (CAPS) and ion neutral mass spectrometer (INMS) experiments in space
Planetary and Space Science, 2015Co-Authors: E C Sittler, D Chornay, B R Rowe, Cristina PuzzariniAbstract:Abstract The discovery of carbocations and carbanions by Ion Neutral Mass Spectrometer (INMS) and the Cassini Plasma Spectrometer (CAPS) instruments onboard the Cassini spacecraft in Titan׳s upper atmosphere is truly amazing for astrochemists and astrobiologists. In this paper we identify the reaction mechanisms for the growth of the complex macromolecules observed by the CAPS Ion Beam Spectrometer (IBS) and Electron Spectrometer (ELS). This identification is based on a recently published paper (Ali et al., 2013. Planet. Space Sci. 87, 96) which emphasizes the role of Olah׳s nonclassical carbonium ion chemistry in the synthesis of the organic molecules observed in Titan׳s thermosphere and ionosphere by INMS. The main conclusion of that work was the demonstration of the presence of the cyclopropenyl cation – the simplest Huckel׳s aromatic molecule – and its cyclic methyl derivatives in Titan׳s atmosphere at high altitudes. In this study, we present the transition from simple aromatic molecules to the complex ortho-bridged bi- and tri-cyclic hydrocarbons, e.g., CH 2 + mono-substituted naphthalene and phenanthrene, as well as the ortho- and peri-bridged tri-cyclic aromatic ring, e.g., perinaphthenyl cation. These rings could further grow into tetra-cyclic and the higher order ring polymers in Titan׳s upper atmosphere. Contrary to the pre-Cassini observations, the nitrogen chemistry of Titan׳s upper atmosphere is found to be extremely rich. A variety of N-containing hydrocarbons including the N-heterocycles where a CH group in the polycyclic rings mentioned above is replaced by an N atom, e.g., CH 2 + substituted derivative of quinoline (Benzopyridine), are found to be dominant in Titan׳s upper atmosphere. The mechanisms for the formation of complex molecular anions are discussed as well. It is proposed that many closed-shell complex carbocations after their formation first, in Titan׳s upper atmosphere, undergo the kinetics of electron recombination to form open-shell neutral radicals. These radical species subsequently might form carbanions via radiative electron attachment at low temperatures with thermal electrons. The classic example is the perinaphthenyl anion in Titan׳s upper atmosphere. Therefore, future astronomical observations of selected carbocations and corresponding carbanions are required to settle the key issue of molecular anion chemistry on Titan. Other than earth, Titan is the only planetary body in our solar system that is known to have reservoirs of permanent liquids on its surface. The synthesis of complex biomolecules either by organic catalysis of precipitated solutes “on hydrocarbon solvent” on Titan or through the solvation process indeed started in its upper atmosphere. The most notable examples in Titan׳s prebiotic atmospheric chemistry are conjugated and aromatic polycyclic molecules, N-heterocycles including the presence of imino >C N–H functional group in the carbonium chemistry. Our major conclusion in this paper is that the synthesis of organic compounds in Titan׳s upper atmosphere is a direct consequence of the chemistry of carbocations involving the ion–molecule reactions. The observations of complexity in the organic chemistry on Titan from the Cassini–Huygens mission clearly indicate that Titan is so far the only planetary object in our solar system that will most likely provide an answer to the question of the synthesis of complex biomolecules on the primitive earth and the origin of life.
E C Sittler - One of the best experts on this subject based on the ideXlab platform.
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Organic chemistry in Titan׳s upper atmosphere and its astrobiological consequences: I. Views towards Cassini plasma spectrometer (CAPS) and ion neutral mass spectrometer (INMS) experiments in space
Planetary and Space Science, 2020Co-Authors: E C Sittler, D Chornay, B R Rowe, Cristina PuzzariniAbstract:International audienceThe discovery of carbocations and carbanions by Ion Neutral Mass Spectrometer (INMS) and the Cassini Plasma Spectrometer (CAPS) instruments onboard the Cassini spacecraft in Titan׳s upper atmosphere is truly amazing for astrochemists and astrobiologists. In this paper we identify the reaction mechanisms for the growth of the complex macromolecules observed by the CAPS Ion Beam Spectrometer (IBS) and Electron Spectrometer (ELS). This identification is based on a recently published paper (Ali et al., 2013. Planet. Space Sci. 87, 96) which emphasizes the role of Olah׳s nonclassical carbonium ion chemistry in the synthesis of the organic molecules observed in Titan׳s thermosphere and ionosphere by INMS. The main conclusion of that work was the demonstration of the presence of the cyclopropenyl cation – the simplest Huckel׳s aromatic molecule – and its cyclic methyl derivatives in Titan׳s atmosphere at high altitudes. In this study, we present the transition from simple aromatic molecules to the complex ortho-bridged bi- and tri-cyclic hydrocarbons, e.g., CH2+ mono-substituted naphthalene and phenanthrene, as well as the ortho- and peri-bridged tri-cyclic aromatic ring, e.g., perinaphthenyl cation. These rings could further grow into tetra-cyclic and the higher order ring polymers in Titan׳s upper atmosphere. Contrary to the pre-Cassini observations, the nitrogen chemistry of Titan׳s upper atmosphere is found to be extremely rich. A variety of N-containing hydrocarbons including the N-heterocycles where a CH group in the polycyclic rings mentioned above is replaced by an N atom, e.g., CH2+ substituted derivative of quinoline (Benzopyridine), are found to be dominant in Titan׳s upper atmosphere. The mechanisms for the formation of complex molecular anions are discussed as well. It is proposed that many closed-shell complex carbocations after their formation first, in Titan׳s upper atmosphere, undergo the kinetics of electron recombination to form open-shell neutral radicals. These radical species subsequently might form carbanions via radiative electron attachment at low temperatures with thermal electrons. The classic example is the perinaphthenyl anion in Titan׳s upper atmosphere. Therefore, future astronomical observations of selected carbocations and corresponding carbanions are required to settle the key issue of molecular anion chemistry on Titan. Other than earth, Titan is the only planetary body in our solar system that is known to have reservoirs of permanent liquids on its surface. The synthesis of complex biomolecules either by organic catalysis of precipitated solutes “on hydrocarbon solvent” on Titan or through the solvation process indeed started in its upper atmosphere. The most notable examples in Titan׳s prebiotic atmospheric chemistry are conjugated and aromatic polycyclic molecules, N-heterocycles including the presence of imino >CN–H functional group in the carbonium chemistry. Our major conclusion in this paper is that the synthesis of organic compounds in Titan׳s upper atmosphere is a direct consequence of the chemistry of carbocations involving the ion–molecule reactions. The observations of complexity in the organic chemistry on Titan from the Cassini–Huygens mission clearly indicate that Titan is so far the only planetary object in our solar system that will most likely provide an answer to the question of the synthesis of complex biomolecules on the primitive earth and the origin of lif
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organic chemistry in titan s upper atmosphere and its astrobiological consequences i views towards cassini plasma spectrometer caps and ion neutral mass spectrometer inms experiments in space
Planetary and Space Science, 2015Co-Authors: E C Sittler, D Chornay, B R Rowe, Cristina PuzzariniAbstract:Abstract The discovery of carbocations and carbanions by Ion Neutral Mass Spectrometer (INMS) and the Cassini Plasma Spectrometer (CAPS) instruments onboard the Cassini spacecraft in Titan׳s upper atmosphere is truly amazing for astrochemists and astrobiologists. In this paper we identify the reaction mechanisms for the growth of the complex macromolecules observed by the CAPS Ion Beam Spectrometer (IBS) and Electron Spectrometer (ELS). This identification is based on a recently published paper (Ali et al., 2013. Planet. Space Sci. 87, 96) which emphasizes the role of Olah׳s nonclassical carbonium ion chemistry in the synthesis of the organic molecules observed in Titan׳s thermosphere and ionosphere by INMS. The main conclusion of that work was the demonstration of the presence of the cyclopropenyl cation – the simplest Huckel׳s aromatic molecule – and its cyclic methyl derivatives in Titan׳s atmosphere at high altitudes. In this study, we present the transition from simple aromatic molecules to the complex ortho-bridged bi- and tri-cyclic hydrocarbons, e.g., CH2+ mono-substituted naphthalene and phenanthrene, as well as the ortho- and peri-bridged tri-cyclic aromatic ring, e.g., perinaphthenyl cation. These rings could further grow into tetra-cyclic and the higher order ring polymers in Titan׳s upper atmosphere. Contrary to the pre-Cassini observations, the nitrogen chemistry of Titan׳s upper atmosphere is found to be extremely rich. A variety of N-containing hydrocarbons including the N-heterocycles where a CH group in the polycyclic rings mentioned above is replaced by an N atom, e.g., CH2+ substituted derivative of quinoline (Benzopyridine), are found to be dominant in Titan׳s upper atmosphere. The mechanisms for the formation of complex molecular anions are discussed as well. It is proposed that many closed-shell complex carbocations after their formation first, in Titan׳s upper atmosphere, undergo the kinetics of electron recombination to form open-shell neutral radicals. These radical species subsequently might form carbanions via radiative electron attachment at low temperatures with thermal electrons. The classic example is the perinaphthenyl anion in Titan׳s upper atmosphere. Therefore, future astronomical observations of selected carbocations and corresponding carbanions are required to settle the key issue of molecular anion chemistry on Titan. Other than earth, Titan is the only planetary body in our solar system that is known to have reservoirs of permanent liquids on its surface. The synthesis of complex biomolecules either by organic catalysis of precipitated solutes “on hydrocarbon solvent” on Titan or through the solvation process indeed started in its upper atmosphere. The most notable examples in Titan׳s prebiotic atmospheric chemistry are conjugated and aromatic polycyclic molecules, N-heterocycles including the presence of imino >C N–H functional group in the carbonium chemistry. Our major conclusion in this paper is that the synthesis of organic compounds in Titan׳s upper atmosphere is a direct consequence of the chemistry of carbocations involving the ion–molecule reactions. The observations of complexity in the organic chemistry on Titan from the Cassini–Huygens mission clearly indicate that Titan is so far the only planetary object in our solar system that will most likely provide an answer to the question of the synthesis of complex biomolecules on the primitive earth and the origin of life.
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Organic chemistry in Titan׳s upper atmosphere and its astrobiological consequences: I. Views towards Cassini plasma spectrometer (CAPS) and ion neutral mass spectrometer (INMS) experiments in space
Planetary and Space Science, 2015Co-Authors: E C Sittler, D Chornay, B R Rowe, Cristina PuzzariniAbstract:Abstract The discovery of carbocations and carbanions by Ion Neutral Mass Spectrometer (INMS) and the Cassini Plasma Spectrometer (CAPS) instruments onboard the Cassini spacecraft in Titan׳s upper atmosphere is truly amazing for astrochemists and astrobiologists. In this paper we identify the reaction mechanisms for the growth of the complex macromolecules observed by the CAPS Ion Beam Spectrometer (IBS) and Electron Spectrometer (ELS). This identification is based on a recently published paper (Ali et al., 2013. Planet. Space Sci. 87, 96) which emphasizes the role of Olah׳s nonclassical carbonium ion chemistry in the synthesis of the organic molecules observed in Titan׳s thermosphere and ionosphere by INMS. The main conclusion of that work was the demonstration of the presence of the cyclopropenyl cation – the simplest Huckel׳s aromatic molecule – and its cyclic methyl derivatives in Titan׳s atmosphere at high altitudes. In this study, we present the transition from simple aromatic molecules to the complex ortho-bridged bi- and tri-cyclic hydrocarbons, e.g., CH 2 + mono-substituted naphthalene and phenanthrene, as well as the ortho- and peri-bridged tri-cyclic aromatic ring, e.g., perinaphthenyl cation. These rings could further grow into tetra-cyclic and the higher order ring polymers in Titan׳s upper atmosphere. Contrary to the pre-Cassini observations, the nitrogen chemistry of Titan׳s upper atmosphere is found to be extremely rich. A variety of N-containing hydrocarbons including the N-heterocycles where a CH group in the polycyclic rings mentioned above is replaced by an N atom, e.g., CH 2 + substituted derivative of quinoline (Benzopyridine), are found to be dominant in Titan׳s upper atmosphere. The mechanisms for the formation of complex molecular anions are discussed as well. It is proposed that many closed-shell complex carbocations after their formation first, in Titan׳s upper atmosphere, undergo the kinetics of electron recombination to form open-shell neutral radicals. These radical species subsequently might form carbanions via radiative electron attachment at low temperatures with thermal electrons. The classic example is the perinaphthenyl anion in Titan׳s upper atmosphere. Therefore, future astronomical observations of selected carbocations and corresponding carbanions are required to settle the key issue of molecular anion chemistry on Titan. Other than earth, Titan is the only planetary body in our solar system that is known to have reservoirs of permanent liquids on its surface. The synthesis of complex biomolecules either by organic catalysis of precipitated solutes “on hydrocarbon solvent” on Titan or through the solvation process indeed started in its upper atmosphere. The most notable examples in Titan׳s prebiotic atmospheric chemistry are conjugated and aromatic polycyclic molecules, N-heterocycles including the presence of imino >C N–H functional group in the carbonium chemistry. Our major conclusion in this paper is that the synthesis of organic compounds in Titan׳s upper atmosphere is a direct consequence of the chemistry of carbocations involving the ion–molecule reactions. The observations of complexity in the organic chemistry on Titan from the Cassini–Huygens mission clearly indicate that Titan is so far the only planetary object in our solar system that will most likely provide an answer to the question of the synthesis of complex biomolecules on the primitive earth and the origin of life.