Fluorine NMR investigations on trifluoromethylgermanes

Eujen, R.; Mellies, R. L.

doi:10.1016/s0022-1139(00)84956-8

Cited by 28 publications

(50 citation statements)

References 37 publications

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“…The same holds for the 13 12 CF 3 isotopomer is revealed only through simulations. The hexafluoroisopropyl CF 3 groups in the alcohol and triflate and the SO 2 CF 3 group in the triflate apparently provide the first examples of cross-correlated relaxation in 13 CF 3 groups.…”

mentioning

confidence: 57%

“…As will be shown, these lineshape effects depend in a complex manner on the size of 1 J CF , 3 J CF , and 4 J FF ; on the magnitude of the one-bond 13 C/ 12 C isotope effect on the 19 F chemical shift [ 1 19 F( 13/12 C)]; on the field strength; and for 2, also on 6 J FF and the chemical shift differences in hertz between the various 19 . There does not appear to be any presently available field strength at which first-order patterns can be obtained for the 13 C satellites in the 19 F spectra.…”

Section: Introductionmentioning

confidence: 98%

“…The complex lineshapes in the 13 C spectra and the complex and different lineshapes for the 13 C satellites in the 19 F spectra originate in the inequivalence of the hexafluoroisopropyl CF 3 groups when one is 12 CF 3 and the other is 13 CF 3 . As will be shown, these lineshape effects depend in a complex manner on the size of 1 J CF , 3 J CF , and 4 J FF ; on the magnitude of the one-bond 13 C/ 12 C isotope effect on the 19 F chemical shift [ 1 19 F( 13/12 C)]; on the field strength; and for 2, also on 6 J FF and the chemical shift differences in hertz between the various 19 .…”

Section: Introductionmentioning

confidence: 99%

“…[5,6] This very interesting, simple alcohol and the corresponding triflate [(CF 3 ) 2 CH-O-SO 2 CF 3 , 2] seemed appropriate for demonstrating some basic NMR principles involving chemical shifts and J couplings to undergraduates in a laboratory class using a 60-MHz spectrometer at University of St. Thomas (UST). However, unexpectedly complex 19 F and 13 C spectra for 2 led to its analysis on a 500 MHz spectrometer at Rice University and then to a series of additional NMR experiments on 2 and its precursor 1, which provided an excellent opportunity to introduce undergraduates to various NMR topics, as will be described elsewhere. Here, we will focus on the unexpectedly complex 13 C spectra and 13 C satellites in the 19 F spectra.…”

Section: Introductionmentioning

confidence: 99%

“…However, unexpectedly complex 19 F and 13 C spectra for 2 led to its analysis on a 500 MHz spectrometer at Rice University and then to a series of additional NMR experiments on 2 and its precursor 1, which provided an excellent opportunity to introduce undergraduates to various NMR topics, as will be described elsewhere. Here, we will focus on the unexpectedly complex 13 C spectra and 13 C satellites in the 19 F spectra.…”

Section: Introductionmentioning

confidence: 99%

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Simple organofluorine compounds giving field‐dependent ¹³C and ¹⁹F NMR spectra with complex patterns: higher order effects and cross‐correlated relaxation

Alemany

Malloy

Nunes

2010

Magnetic Reson in Chemistry

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The CF(3) signals in the (13)C{(1)H} spectrum of 1,1,1,3,3,3-hexafluoroisopropyl alcohol and the (CF(3))(2) CH signals in the corresponding triflate exhibit much greater complexity than might first be expected. The same holds for the (13)C satellites in the (19)F spectra. Complex patterns appear because of higher order effects resulting from the combination of a relatively large four-bond (19)F-(19)F J coupling in the ((13)CF(3))(12)CH((12)CF(3))-containing isotopomer and a typical large one-bond (13)C/(12)C isotope effect on the (19)F chemical shift. This complexity cannot be eliminated at very high magnetic field strengths. The triflate (CF(3))(2)CH-O-SO(2)CF(3) presents still additional complexity because of the presence of two different types of CF(3) groups exhibiting (6)J(FF) in any of the isotopomers and the chemical shift differences in hertz between the various (19)F signals in the two different (13)CF(3)-containing isotopomers. In addition, the presence of a small (5)J(CF) in the ((13)CF(3))((12)CF(3))(12)CH-O-SO(2) (12)CF(3) isotopomer is revealed only through simulations. The hexafluoroisopropyl CF(3) groups in the alcohol and triflate and the SO(2)CF(3) group in the triflate apparently provide the first examples of cross-correlated relaxation in (13)CF(3) groups. An analysis of the spectra in the context of previously reported work highlights the novel aspects of our findings. In particular, for each part of the complex hexafluoroisopropyl CF(3) quartet, peak height and linewidth variations resulting from cross-correlated relaxation are observed. These variations within a group of (13)C signals reflect different spin-lattice and spin-spin relaxation rates for the transitions within that group arising from higher order coupling effects.

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mentioning

confidence: 57%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Simple organofluorine compounds giving field‐dependent ¹³C and ¹⁹F NMR spectra with complex patterns: higher order effects and cross‐correlated relaxation

Alemany

Malloy

Nunes

2010

Magnetic Reson in Chemistry

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Large Parity‐Violation Effects in Heavy‐Metal‐Containing Chiral Compounds

2003

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The weak neutral current (Z-boson exchange) [1][2][3] between electrons and nucleons (quarks) introduces a small energy difference (DE PV ) between enantiomers of a chiral molecule owing to parity violation (P-odd effects). [4,5] There have been several attempts to measure the parity-violation (PV) difference between enantiomers, [6][7] however, such effects are estimated to be of the order of a few millihertz [8][9][10] for currently known molecules, and several orders of magnitude too low for the present ability of high-resolution spectroscopy. Here we report relativistic calculations of PV effects for several chiral compounds that contain a heavy-metal center; shifts in DE PV of up to 4.8 10 À14 au (300 Hz) are recorded for such compounds as [(h 5 -C 5 H 5 )Re(CO)(NO)I], which can easily be prepared. The high DE PV value is an indication that future P-odd experiments for chiral molecules should be directed towards heavy-transition-metal complexes.Since the creation of the unified electroweak theory by Weinberg, Salam, and Glashow, the investigation of PV effects has become one of the most exciting areas in particle physics. [1][2][3] Precise measurements of PV in atoms are now accurate enough for the standard model to be tested successfully. [11] Electroweak theory also predicts a small energy difference (DE PV ) between pairs of enantiomers, and thus a breakdown of mirror-image symmetry. The search for such effects currently involves vibrational, [5,[12][13][14] NMR, [15,16] electronic, [17,18] and Mössbauer [6,19] spectroscopy, electric-field optical activity, [20] and preferred crystallization. [21] Most notably, Chardonnet and co-workers performed a saturation spectroscopy experiment for CHFClBr in the 9.3 mm spectral range using a tunable CO 2 laser that provided a spectral purity of 6 Hz. [12] They obtained Dn PV = n RÀ Àn S+ = 9.4 AE 5.1 AE 12.7 Hz between the two enantiomers, where the first value of uncertainty is derived from statistical error and the second is determined by systematic effects. More recently, the same group reduced these uncertainties and obtained Dn PV = À4.2 AE 0.6 AE 1.6 Hz. [22] Thus the search for the breakdown of mirror-image symmetry in chiral molecules remains one of the most challenging tasks in molecular chemistry and physics.It is a nontrivial issue to find chiral compounds suitable for high-resolution spectroscopic measurements of parity nonconservation effects. [23] P-odd effects scale approximately like Z n (n % 5; Z = nuclear charge of the atom), [24] which limits the choice to heavy-element-containing compounds. Furthermore, in accordance with the single-center theorem of Hegstroem, the substance should contain more than one heavy element (either as ligands or chiral centers). [25] A detailed analysis of P-odd effects, with respect to the environment around a center of chirality, has been given by Faglioni and Lazzeretti. [26] Very recently they also proposed the hypothetical molecule [BiHFX] (X = Br, I) as a suitable candidate with PV effects, with the Dn PV value o...

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Large Parity‐Violation Effects in Heavy‐Metal‐Containing Chiral Compounds

2003

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The weak neutral current (Z-boson exchange) [1][2][3] between electrons and nucleons (quarks) introduces a small energy difference (DE PV ) between enantiomers of a chiral molecule owing to parity violation (P-odd effects). [4,5] There have been several attempts to measure the parity-violation (PV) difference between enantiomers, [6][7] however, such effects are estimated to be of the order of a few millihertz [8][9][10] for currently known molecules, and several orders of magnitude too low for the present ability of high-resolution spectroscopy. Here we report relativistic calculations of PV effects for several chiral compounds that contain a heavy-metal center; shifts in DE PV of up to 4.8 10 À14 au (300 Hz) are recorded for such compounds as [(h 5 -C 5 H 5 )Re(CO)(NO)I], which can easily be prepared. The high DE PV value is an indication that future P-odd experiments for chiral molecules should be directed towards heavy-transition-metal complexes.Since the creation of the unified electroweak theory by Weinberg, Salam, and Glashow, the investigation of PV effects has become one of the most exciting areas in particle physics. [1][2][3] Precise measurements of PV in atoms are now accurate enough for the standard model to be tested successfully.[11] Electroweak theory also predicts a small energy difference (DE PV ) between pairs of enantiomers, and thus a breakdown of mirror-image symmetry. The search for such effects currently involves vibrational, [5,[12][13][14] NMR, [15,16] electronic, [17,18] and Mössbauer [6,19] spectroscopy, electric-field optical activity, [20] and preferred crystallization.[21] Most notably, Chardonnet and co-workers performed a saturation spectroscopy experiment for CHFClBr in the 9.3 mm spectral range using a tunable CO 2 laser that provided a spectral purity of 6 Hz. [12] They obtained Dn PV = n RÀ Àn S+ = 9.4 AE 5.1 AE 12.7 Hz between the two enantiomers, where the first value of uncertainty is derived from statistical error and the second is determined by systematic effects. More recently, the same group reduced these uncertainties and obtained Dn PV = À4.2 AE 0.6 AE 1.6 Hz.[22] Thus the search for the breakdown of mirror-image symmetry in chiral molecules remains one of the most challenging tasks in molecular chemistry and physics.It is a nontrivial issue to find chiral compounds suitable for high-resolution spectroscopic measurements of parity nonconservation effects.[23] P-odd effects scale approximately like Z n (n % 5; Z = nuclear charge of the atom), [24] which limits the choice to heavy-element-containing compounds. Furthermore, in accordance with the single-center theorem of Hegstroem, the substance should contain more than one heavy element (either as ligands or chiral centers).[25] A detailed analysis of P-odd effects, with respect to the environment around a center of chirality, has been given by Faglioni and Lazzeretti.[26] Very recently they also proposed the hypothetical molecule [BiHFX] (X = Br, I) as a suitable candidate with PV effects, with the Dn PV value of the i...

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Fluorine NMR investigations on trifluoromethylgermanes

Cited by 28 publications

References 37 publications

Simple organofluorine compounds giving field‐dependent ¹³C and ¹⁹F NMR spectra with complex patterns: higher order effects and cross‐correlated relaxation

Simple organofluorine compounds giving field‐dependent ¹³C and ¹⁹F NMR spectra with complex patterns: higher order effects and cross‐correlated relaxation

Large Parity‐Violation Effects in Heavy‐Metal‐Containing Chiral Compounds

Large Parity‐Violation Effects in Heavy‐Metal‐Containing Chiral Compounds

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Fluorine NMR investigations on trifluoromethylgermanes

Cited by 28 publications

References 37 publications

Simple organofluorine compounds giving field‐dependent 13C and 19F NMR spectra with complex patterns: higher order effects and cross‐correlated relaxation

Simple organofluorine compounds giving field‐dependent 13C and 19F NMR spectra with complex patterns: higher order effects and cross‐correlated relaxation

Large Parity‐Violation Effects in Heavy‐Metal‐Containing Chiral Compounds

Large Parity‐Violation Effects in Heavy‐Metal‐Containing Chiral Compounds

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Simple organofluorine compounds giving field‐dependent ¹³C and ¹⁹F NMR spectra with complex patterns: higher order effects and cross‐correlated relaxation

Simple organofluorine compounds giving field‐dependent ¹³C and ¹⁹F NMR spectra with complex patterns: higher order effects and cross‐correlated relaxation