Presentation is loading. Please wait.

Presentation is loading. Please wait.

U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat1 Chimica Fisica dei Materiali Avanzati Part 8 – Molecular switches and molecular machines Laurea.

Similar presentations


Presentation on theme: "U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat1 Chimica Fisica dei Materiali Avanzati Part 8 – Molecular switches and molecular machines Laurea."— Presentation transcript:

1 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat1 Chimica Fisica dei Materiali Avanzati Part 8 – Molecular switches and molecular machines Laurea specialistica in Scienza e Ingegneria dei Materiali Curriculum Scienza dei Materiali

2 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat2 Molecular-level devices Molecular-level electronic components Molecular-level systems that play the same functions played by macroscopic components in electronic devices Molecular-level mechanical machines Molecular-level systems that perform mechanical movements analogous to those observed in macroscopic machines Molecular-level electronic components Molecular wires Molecular switches Molecular antennas Charge-separation devices Molecular memories Molecular sensors Molecular logic gates Molecular-level mechanical machines Molecular tweezers, doors and boxes Rotary motors Piston/cylinder systems Molecular shuttles and muscles Sliding molecular rings

3 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat3 Switching of electron or energy transfer processes Switching requires an external stimulus which, at the molecular level, causes electronic and nuclear rearrangements. Usually one of the two types of rearrangements prevails or is more relevant to the performed function. The three main types of stimuli that can be used to switch a chemical compound are: Light energy Light energy (photons) Electrical energy Electrical energy (electrons or holes) Chemical energy Chemical energy (in the form of reactants) A C A C e - or E

4 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat4 Molecular switches A molecular switch is a system on the molecular scale which can be reversibly brought from one state into another by means of an external stimulus. Important properties for practical applications: thermal irreversibility quick response high efficiency fatigue resistance nondestructive readout

5 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat5 Example: diarylethene switches First described by Irie in M. Irie, M. Mohri, J. Org. Chem. 53 (1988), Reaction is thermally irreversible, response is quick, efficiency and fatigue resistance are high. Many studies have been performed on diarylethenes, with as main goals improving the switching properties and achieving non-destructive read-out. For an extensive review, see: M. Irie, Chem. Rev. 100 (2000),

6 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat6 Photochromic response of diarylethene A very broad absorption extending over most of the visible range appears upon UV irradiation and ring closure The process can be reversed by irradiation with > 500 nm

7 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat7 Mechanism: increase of the conjugation Open ring, parallel conformation Open ring, antiparallel conformation Closed ring

8 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat8 Other photochromic switches Cis-trans isomerization of azobenzenes Switching of a spiropyran derivative (c = closed, o = open) Photochemical transformations of fulgides

9 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat9 Optical memories by holographic recording Holographic optical storage is a unique method for achieving high- density data storage in three dimensions. Photopolymer systems are quite attractive because of their high sensitivity, ease of preparation, and self-development capability. Rewritable holographic recording materials based on photochromic conversion have attracted strong interest for three-dimensional optical recording Photochromic cyclability Holographic writing set-up A phase hologram with n = 1.15x10 -3 and period dependent on the angle 2 is written.

10 U NIVERSITA DEGLI S TUDI DI P ADOVA n * N NR N O CH 3 CH 2 C CO Methacrylic backbone Optically active cyclic group Conjugated trans-azoaromatic chromophore R = CN, NO 2 poly[(S)-MAP-C] R = CN M n =43,900 M w / M n =1.4 T g =192°C T d = 311°C poly[(S)-MAP-N] R = NO 2 M n =18,300 M w / M n =1.4 T g =208°C T d = 315°C

11 U NIVERSITA DEGLI S TUDI DI P ADOVA Absorption in the visible: azo-dyes n *, * and CT el. trans. 488 nm 633 nm

12 U NIVERSITA DEGLI S TUDI DI P ADOVA Photoinduced trans cis trans isomerization cycles Ē rotational diffusion h h STOP trans cis

13 U NIVERSITA DEGLI S TUDI DI P ADOVA Reversible photoinduced orientation of azobenzene groups

14 U NIVERSITA DEGLI S TUDI DI P ADOVA

15 poly[(S)-MAP-N] T g = 208 C thin films nm I 160 mW/cm 2 x 60 s Reversible inversion of the CD signal by irradiation with CP-L light L. Angiolini et al., Chem. Eur. J., 8 (2002) 4241

16 U NIVERSITA DEGLI S TUDI DI P ADOVA Photomodulation of linear birefringence and dichroism PHOTORESPONSIVE PROPERTIES CONVENTIONAL MATERIALS CHIROPTICAL SWITCHES OPTICAL STORAGE AND CHIROPTICAL SWITCHES CHIRAL PHOTOCHROMIC POLYMERS Photomodulation of chiroptical properties OPTICAL STORAGE

17 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat17 Switching of electron transfer by a photon input Light switching of electron transfer in multicomponent molecular systems based on the 1,2-bis-(3-thienyl)-ethene photochromic bridge In the closed form energy is transferred to the conjugated diarylethene unit instead of electron transferred to the pyridinium ion

18 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat18 Multistate-multifunctional supramolecular systems Multistate systems : compounds that can be reversibly interconverted between more than two stable states Multifunctional systems : compounds that can be reversibly interconverted between stable states by means of different stimuli Two photochromic units can be coupled in the same supramolecular species, giving biphotochromic multistate systems The photochemical inputs used to stimulate photochromic compounds can be couped with several other types of stimuli, leading to a variety of interesting multistate-multifunctional systems On application of n independent stimuli, each related to 2 states, 2 n different states of the system become available in principle

19 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat19 Towards molecular logic gates

20 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat20 Electronic vs. chemical computers

21 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat21 Molecular-level machines A molecular machine is a particular type of a molecular device whose outcome is a mechanical motion, i.e., in which the component parts can be set in motion as a result of some external stimulus What are the possibilities of small but movable machines? [...] Lubrication might not be necessary. Bearings could run dry; they wouldnt run hot because heat escapes from such a small device very, very rapidly. [...] An internal combustion engine of that size is impossible. Other chemical reactions, liberating energy when cold, can be used instead. [...] What would be the utility of such machines? Who knows? [...] I cannot see exactly what would happen, but I can hardly doubt that when we have some control of things on a molecular scale we will get an enormously greater range of possible properties that substances can have, and of the different things we can do. R. P. Feynman, Address to the American Physical Society, December 1959

22 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat22 Natural Molecular Machines and Motors Cells have hundreds of different types of molecular motors, each specialized for a particular function. Many biological motor-like proteins have been discovered and characterized in recent years. (Natural) molecular motors come in a wide variety of designs. Some motors operate in a cyclic fashion, undergoing a number of steps that correspond to changes in conformation and/or in chemical state, and eventually resetting themselves to their initial configuration. Copernicus, Springer - Verlag, New York, 1996 C. Bustamante, D. Keller, G. Oster, Acc. Chem. Res., 2001, 34,

23 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat23 Natural Molecular Machines and Motors - 2 Rotary motor proteins ATP Synthase Bacterial flagellar motor Linear motor proteins Myosin Kinesin Dynein

24 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat24 Artificial molecular machines: molecular tweezers Macroscopic tweezers Molecular tweezers (photochemically controlled) S. Shinkai et al., J. Am. Chem. Soc., 1981, 103, 111

25 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat25 Photocontrolled Opening-Closing of Molecular Cavities Azobenzene containing macrotricyclic receptors Azobenzene capped β-cyclodextrin

26 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat26 A Photochemically Driven Molecular Rotary Motor B.L. Feringa et al., Nature, 1999, 401, 152

27 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat27 Photochemically Driven Threading-Dethreading Motions in Pseudorotaxanes

28 U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat28 Undirectional Circumrotation of Macrocycles in Catenanes


Download ppt "U NIVERSITA DEGLI S TUDI DI P ADOVA Corso CFMA. LS-SIMat1 Chimica Fisica dei Materiali Avanzati Part 8 – Molecular switches and molecular machines Laurea."

Similar presentations


Ads by Google