enantiomers and enantioselective surfaces leonardo andrés...

IntroductionLife and Handedness

Enantioselective SurfacesTheoretical point of view: selection of chiral molecules

Chiral systemsEnantiomers and Enantioselective Surfaces

Leonardo Andrés Espinosa Leal1,2

1Nano-bio Spectroscopy Group.European Theoretical Spectroscopy Facility (ETSF)

nanoquanta. Network of Excellence.

2Departamento de Física de Materiales, Facultad de Ciencias Químicas,Universidad del País Vasco, Centro Mixto UPV-CSIC.

January of 2008

Leonardo A. Espinosa L. Quiral systems

What is Chirality?A Chirality Timelineclassification of chiralityEnantiomers

Outline

1 IntroductionWhat is Chirality?A Chirality Timelineclassification of chiralityEnantiomers

2 Life and HandednessHomochirality and lifeSome possibles answers

3 Enantioselective SurfacesChiral surfaces

4 Theoretical point of view: selection of chiral moleculesSelection methods

What is Chirality?Life in the another side of the mirror

“Imagine. . . a musty storeroom crammedfull of mannequin parts, left and rightarms in rigidified plastic disarrayAnd you, in the dark, have to sortthem out. It’s a left-over Fellini setIt’s soon done, but whyis there one more right hand than left?”

Catalista, Selected Poems, 2002.Roald Hoffmann (Nobel prize in Chemistry,1981).

Definition: From Greek kheir:hand

“I call any geometrical figure or group of points, chiral, and

say that its chirality, if its image in a plane mirror, ideally

realized, cannot be brought to coincide with itself”a.

aW. Thomson Kelvin, Baltimore Lectures on Molecular Dynamics

and the wave theory of light, C.J. Clay, London, 1904.

Outline

HistoryBreaking the symmetry. Part I.

History Path until XIX century

1 250B.C. Archimedes of Syracuse. The design of theArchimedean water screw and the study of spiralstructure.

2 1811. Dominique FranÃ§ois Jean Arago. Discovery ofthe rotation of the polarization of light in quartz crystals.

3 1835. Jean-Baptiste Biot. Discovery of the rotation ofthe polarization of light in sugar solution.

4 1848. Louis Pasteur. Paratartaric acid is identified asthe stereoisomer of tartaric acid. Pasteur postulates thatnature has a chiral asymmetry.

5 1888. Friedrich Reinitzer. Discovery of the (chiral) bluephase of liquid crystals. Coining of the term "liquidcrystals".

6 1893. William Thomson (Lord Kelvin). Defines thenotion of a chiral object and chirality.

History Path after XIX century

1 1951. Linus Pauling and Robert BrainardCorey. Discovery of the alpha-helix inprotein.

2 1953. James D. Watson and Francis Crick.Discovery of the DNA double-helix.

3 1956. Tsung Dao Lee and Chen Ning Yang.Proposal of parity nonconservation to explainthe "theta-tau" paradox.

4 1957. Chien-Shiung Wu. Discovery of parityviolation in the beta-decay of 60Co.

5 1958. Richard P. Feynman, MurrayGell-Mann, Robert E. Marshak and E.C.George Sudarshan. Parity violating"vector–axial vector" theory of the weakinteraction.

6 1964. James Cronin and Val L. Fitch.Discovery of CP violation in neutral kaondecays.

7 1973. Howard C. Berg and Robert A.Anderson. Prediction and confirmation ofrotary motion in bacterial flagella.

Outline

Implications in chemistryWhen Topology Meets Chemistry

Isomers: molecules with the samechemical formula and often with the samekinds of chemical bonds between atoms,but in which the atoms are arrangeddifferently.

The atoms and functional groups arejoined together in different ways.

The bond structure is the same, but thegeometrical positioning of atoms andfunctional groups in space differs.

Enantiomers where different isomers arenon-superimposable mirror-images ofeach other, and diastereomers whenthey are not.

Outline

EnantiomersWhen the mirror-image is not ever beauty

“How would you like to live in a looking-glass house, Kitty? . . . Perhaps looking-glassmilk isn’t good to drink.” Alice to her cat.

Through the Looking-Glass and What Alice Found There.Lewis Carroll, 1871.

1 (R)-limonene smells of oranges while itsenantiomer, (S)-limonene, smells oflemons.

2 From 1956 to 1962, approximately 10,000children were born with severemalformities, including phocomelia,because their mothers had takenthalidomide during pregnancy.

Homochirality and lifeSome possibles answers

Outline

Chirality as a Problem in Underestanding the Origin of Life

Chirality is intrinsic to complex molecules.

What was surprising was that all life usesL-Amino Acids (read proteins) and D-Sugars(DNA and RNA)

Huge implications for origins of life.

First Big Question

Does life require homochirality to initiate or does lifeproduce homochirality?

Preliminary answers

1 Life seems to require homochirality.

2 Must be a mechanism that eitherNaturally selects for a certainchirality.Produces a homochiral solution.

First Big Question

Preliminary answers

First Big Question

Preliminary answers

First Big Question

Preliminary answers

First Big Question

Preliminary answers

First Big Question

Preliminary answers

First Big Question

Preliminary answers

First Big Question

Preliminary answers

Outline

creationism vs evolutionism, again...

Answer 1

God: Intelligent design.

Answer 2

The truth is out here: Panspermiaor Exogenesis.

Answer 3

Mixture of both.

Anothers answers(unsatisfactory, until now)

Parity. Weak nuclear interaction.

Two Chirally Selective Sources.

Circularly polarized light (CPL).

Location of galaxy.

Meteoritic Evidence.

Magnetochiral dichroism.

Answer 1

Answer 2

Answer 3

Mixture of both.

Location of galaxy.

Answer 1

Answer 2

Answer 3

Mixture of both.

Location of galaxy.

Answer 1

Answer 2

Answer 3

Mixture of both.

Location of galaxy.

Chiral surfaces

Outline

Chiral surfaces

Creation of chiral surfaces

Growth of chiral solid films.

Clean metal chiral surfaces.

Organic chiral adsorbates modified metal surfaces.

Adsorbate induced chiral facets.

Physical study of chiral surfaces

Symmetry and geometry sensitive methods.Low-energy electron diffraction.Linear dichroism electron impact scattering.X-Ray photoelectron diffraction.

Chiral interaction methods.Temperature programmed desortion.Reflection-absortion infrared spectroscopy.Electrochemical oxidation.Chemical Force Microscopy.Scanning tunneling microscopy.

Chiral surfaces

Selection methodsConclusions

Outline

Model of enantioselective-control

Perturbative aproximation

Controlling the molecular chirality inchemical reactions by circularlypolarized fields.

Dynamic method

Study of quantum systems with brokensymmetry. Modelling as cyclicthree-level atoms with coexisting one-and two-phton transitions.

Enantioselective surfaces

Until now, do not exist any theory.

Conclusions

Our natural world is filled with structural motifs that reveal an intrinsinhandeness. This shape is a consecuence of organic like-assymetry.

Chiral surfaces shows higher capacity of selectivity of some kind enantiomericalspecies.

The problem of the beginning of life is, until now, a open question. a lot ofliterature show irrelevant results and theories inexact about handeness processin life.

Conclusions

Bibliography

[Qiao Chen and Neville V. Richardson]”Physical studies of chiral surfaces" Annu. Rep. Prog. Chem., Sect. C, 2004, 100, 313â347

[Pedro Cintas]”Tracing the Origins and Evolution of Chirality and Handedness in Chemical Language" Angew. Chem. Int.Ed. 2007, 46, 4016 â 4024

[Yong Li and C. Bruder]”Dynamic method to distinguish between left- and right-handed chiral molecules" PHYSICAL REVIEW A 77,015403 2008.

[G. L. J. A. Rikken, E. Raupach]”Enantioselective magnetochiral photochemistry" NATURE, VOL 405, 22 JUNE 2000

[Jiushu Shao and Peter Hanggi]”Control of molecular chirality" J. Chem. Phys. 107 (23), 15 December 1997.

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