1. Molecular Nanostuctures 1. Introduction. Carbon hybridization and allotropes Alexey A. Popov, IFW Dresden a.popov@ifw-dresden.de

2. Carbon

3. 6 C Carbon Mass fraction in the Earth‘s crust:0.087% Atomic mass:12.011 Isotops: 12 C (98.9 %) 13 C (1.1 %) 14 C (nicht stabil, < 10 −9 %) Electron configuration:1s 2 2s 2 p 2... Material Carbon Nano-Material

4. 6 C Carbon Material Bonding Molecular Structure Compounds Crystal Structure Carbon Nano-Material

5. 6 C Carbon Material Bonding Molecular Structure Compounds Crystal Structure Properties Applications Characterization methods Theory Methods of Synthesis Carbon Nano-Material

6. Carbon: atomic structure main quantum number

7. Ground state C: 1s 2 2s 2 p 2 Carbon: atomic structure main quantum number

8. Ground state Excited state C: 1s 2 2s 2 p 2 C: 1s 2 2s 1 p 3 Carbon: atomic structure

9. Carbon: hybridization C-sp 3 C-sp 2 C-sp Excited state

10. C-sp 180º Carbon: sp-hybridization

11. C-sp 2 Three sp 2 hybrid orbitals 120º Carbon: sp 2 -hybridization

12. C-sp 3 Four sp 3 hybrid orbitals 109.5º Carbon: sp 3 -hybridization

13. Excited state C-sp 3 C-sp 2 C-sp Carbon: hybridization

14. Bonding between atoms: H 2 molecule, σ-bonding Constructive overlap

15. antibonding σ*-Orbital bonding σ-Orbital Bonding between atoms: H 2 molecule, σ-bonding

16. antibonding σ*-orbital bonding σ-orbital Atomic orbitals Molecular orbital bonding π-orbital antibonding π-orbital Bonding between atoms: σ- and π-bonding Molecular orbital Atomic orbitals

17. Bonding between atoms: σ- and π-bonding

18. + C-sp 3 compounds: ethane C 2 H 6, single bond Only σ-bondng, single bond

19. C-sp 2 compounds: ethylene C 2 H 4, double bond σ-bondingπ-bonding σ- and π-bonding, double bond

20. C-sp 2 compounds: ethylene C 2 H 4, double bond σ-bondingπ-bonding σ- and π-bonding, double bond

21. C-sp compounds: acetylene C 2 H 2, triple bond π-bonding σ-bonding σ- and 2 π-bonds Triple bond

22. Single- versus double- versus triple- CC bonds Bond lengthBond energy 1.53 Å 368 kJ/mol 1.34 Å 611 kJ/mol (+243) 1.20 Å 820 kJ/mol (+209) Rotation around C-C bond has low barrier (free rotation at room temperature) Rotation around C=C bond requires breaking of π-bonding, hence high barrier (no rotation at room temperature, rigid framework)

23. C-sp 3 Bonding: Diamond The lattice structure of cubic diamond and ist elemntal cell The lattice structure of hexagonal diamond (Lonsdaleit).

24. C-sp bonding R(−C≡C−) n R, n = 2–14 The existence of carbyne is myth based on bad science and perhaps even wishful thinking. H. Kroto The existence of carbyne is myth based on bad science and perhaps even wishful thinking. H. Kroto

25. C-sp 2 bonding: butadiene, conjugation Band gap

26. Free electron, time independent Schrödinger equation kinetic energy k wave vector standing plane wave

27. Particle in a box (electron in the infinite potential well) 0 L x V = 0 V = ∞

28. Particle in a box (electron in the infinite potential well) 0 L x V = 0 V = ∞

29. Particle in a box (electron in the infinite potential well) 0 L x V = 0 V = ∞

30. Free electron versus electron in infinite well infinite well free electron dispersion relation

31. C-sp 2 bonding: butadiene, conjugation Band gap

32. Conjugated C-sp 2 systems: π-electron as an electron in a box

33. C-sp 2 bonding: increasing the conjugation length Increase of the π-system → decrease of the distance between the levels, decrease of the gap

34. Kekulé C-sp 2 bonding: benzene, PAH (Polycyclic aromatic hydrocarbons) Naphthalin Anthracen Phenanthren Tetracen Chrysen Coronen (Hexabenzobenzol) 1.39 Å 564 kJ/mol Bond lengthBond energy 1.53 Å 368 kJ/mol 1.34 Å 611 kJ/mol

35. „Small molecule“ Organic Semiconductors: Acenes pentacene tetracene naphthalene anthracene hexacene 3.97 eV 3.84 eV 2.72 eV 2.31 eV 1.90 eV gap popular material for OFET

36. C-sp 2 bonding: graphite

37. 3.35 Å 1.42 Å C-sp 2 bonding: graphite

38. CC Bindungen 1.53 Å368 kJ/mol 1.34 Å611 kJ/mol(+243) 1.20 Å820 kJ/mol(+209) 1.53 Å357 kJ/mol Diamond Graphite 1.42 Å~474 kJ/mol intra 3.35 Å~4.5 kJ/mol inter Bond lengthBond energy 1.39 Å 564 kJ/mol Benzene

39. Graphite versus Diamond

40. The Nobel Prize in Chemistry 1996 was awarded jointly to Robert F. Curl Jr., Sir Harold W. Kroto and Richard E. Smalley "for their discovery of fullerenes".

41. The Nobel Prize in Physics 2010 was awarded jointly to Andre Geim and Konstantin Novoselov "for groundbreaking experiments regarding the two-dimensional material graphene"

42. Fullerene ~ 19,000 Nanotube ~66,000 Graphene ~32,000 Statistics for carbon structures in the title of publications

43. laser evaporation of graphite Discovery of fullerenes Mass-spectrometry analysis of the clusters

44. Mass Spectrometry Time of flight Magnet (Lorenz Force)

45. laser evaporation of graphite Mass spectra C 60 C 70 Discovery of fullerenes Mass-spectrometry analysis of the clusters

46. laser evaporation of graphite Mass spectra C 60 C 70

47. Richard Buckminster Fuller 1895–1983 “Buckminsterfullerene”

48. Monometallofullerenes

49. Publication with “Fullerene” in the title 1 3 55 5 12 160 Kroto et al, Nature 1985

50. Wolfgang Krätschmer Donald R. Huffman

52. Fullerene formation mechanism: molecular dynamics