It is wholly accepted that aggregation and self-recognition played an important role in prebiotic earth. Over the several hundred million years of chemical evolution that brought to the first living organisms, simple molecules evolved into larger and more complex systems, often through processes mediated by supramolecular interactions. Chirality is an important element of terrestrial life either at molecular and supramolecular level and various hypotheses have been proposed to explain its abiotic origin [1]. However, several evolutionary steps were required to produce, implement, and maintain chirality in the terrestrial type of life. The specific chemical mechanisms that lead to the first replicable homochiral substance still remain unknown, though it is certain that chiral recognition through supramolecular interactions played a major role in prebiotic earth and in the evolution of life. The in-depth comprehension of stereospecific, non-covalent interactions is a major issue to understand the origin of life and all processes that occur in living organisms. Information on molecular structure, dynamics, reactivity, energetics of diastereomeric complexes can be achieved by spectroscopic techniques. Though it can be argued that the properties of isolated complexes cannot be directly extended to the condensed phase, gas phase studies have the advantage that tailor-made diastereomeric clusters can be investigated at the molecular level and are appropriate for an accurate understanding of the forces at play in chiral recognition. The results of gas-phase experiments can be used by theoretical chemists as benchmark for the validation of different approximations for ab-initio calculations in chiral systems. Resonant Two Photon Ionization (R2PI) spectroscopy, coupled with time of flight mass spectrometry, is a powerful tool for studying non-covalent molecular interactions involved in chiral recognition [2], allowing to evaluate the gas-phase structure and the energetics of diastereomeric complexes. Recently, we have applied these studies to adducts of fluorinated chiral aromatic alcohols and a variety of chiral solvent molecules [3], with the aim of determining the effect of fluorine substitution on the structure and reactivity properties of their complexes and to verify the role of the fluorine substitution on the chiral recognition process. Here we report on the application of R2PI spectroscopy to gas-phase complexes of chiral fluorophenylethanol chromophores with chiral and achiral solvents. The results have been interpreted with the aid of theoretical predictions. [1] (a) M. Quack, Angew. Chem. Int. Ed., 41, 4618 (2002); (b) U.J. Meierhenrich and W.H.P. Thiemann, Orig. Life. Evol. Biosph., 34, 111 (2004); (c) D.K. Kondepudi, R.J. Kaufman, N. Singh, Science, 250, 975 (1990). [2] N. Borho and M. Suhm, Phys. Chem. Chem. Phys., 4, 2721 (2002). [3] F. Rondino, A. Paladini, A. Ciavardini, A. Casavola, D. Catone, M. Satta, H. D. Barth, A. Giardini, M. Speranza, S. Piccirillo, Phys. Chem. Chem. Phys., 13, 818 (2011).
Chiral recognition in diastereomeric adducts of organofluorines
A Paladini;M Satta;
2012
Abstract
It is wholly accepted that aggregation and self-recognition played an important role in prebiotic earth. Over the several hundred million years of chemical evolution that brought to the first living organisms, simple molecules evolved into larger and more complex systems, often through processes mediated by supramolecular interactions. Chirality is an important element of terrestrial life either at molecular and supramolecular level and various hypotheses have been proposed to explain its abiotic origin [1]. However, several evolutionary steps were required to produce, implement, and maintain chirality in the terrestrial type of life. The specific chemical mechanisms that lead to the first replicable homochiral substance still remain unknown, though it is certain that chiral recognition through supramolecular interactions played a major role in prebiotic earth and in the evolution of life. The in-depth comprehension of stereospecific, non-covalent interactions is a major issue to understand the origin of life and all processes that occur in living organisms. Information on molecular structure, dynamics, reactivity, energetics of diastereomeric complexes can be achieved by spectroscopic techniques. Though it can be argued that the properties of isolated complexes cannot be directly extended to the condensed phase, gas phase studies have the advantage that tailor-made diastereomeric clusters can be investigated at the molecular level and are appropriate for an accurate understanding of the forces at play in chiral recognition. The results of gas-phase experiments can be used by theoretical chemists as benchmark for the validation of different approximations for ab-initio calculations in chiral systems. Resonant Two Photon Ionization (R2PI) spectroscopy, coupled with time of flight mass spectrometry, is a powerful tool for studying non-covalent molecular interactions involved in chiral recognition [2], allowing to evaluate the gas-phase structure and the energetics of diastereomeric complexes. Recently, we have applied these studies to adducts of fluorinated chiral aromatic alcohols and a variety of chiral solvent molecules [3], with the aim of determining the effect of fluorine substitution on the structure and reactivity properties of their complexes and to verify the role of the fluorine substitution on the chiral recognition process. Here we report on the application of R2PI spectroscopy to gas-phase complexes of chiral fluorophenylethanol chromophores with chiral and achiral solvents. The results have been interpreted with the aid of theoretical predictions. [1] (a) M. Quack, Angew. Chem. Int. Ed., 41, 4618 (2002); (b) U.J. Meierhenrich and W.H.P. Thiemann, Orig. Life. Evol. Biosph., 34, 111 (2004); (c) D.K. Kondepudi, R.J. Kaufman, N. Singh, Science, 250, 975 (1990). [2] N. Borho and M. Suhm, Phys. Chem. Chem. Phys., 4, 2721 (2002). [3] F. Rondino, A. Paladini, A. Ciavardini, A. Casavola, D. Catone, M. Satta, H. D. Barth, A. Giardini, M. Speranza, S. Piccirillo, Phys. Chem. Chem. Phys., 13, 818 (2011).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
