Welcome Professor Lin to direct our group!

1. Welcome Professor Lin to direct our group!

2. Self-introduction Name: Yulei.Hao Hometown: Shou County in Anhui Province Mother school: Hefei University of Technology 合肥工业大学 Grade: First-year graduate

3. σ-Aromaticity Review and σ-Aromaticity investigation of 3MRs transition metal alkylidene complexes Reportor: Yulei Hao Advisor: Jun Zhu

4. 1 Introduction of σ-Aromaticity Results and Discussion 3 4 Further work 2 Computed methods

5. 1 Introduction of σ-Aromaticity Dewar firstly proposed the concept of σ-Aromaticity to explain the anomalous behavior of cyclopropane such as the upfield 1HNMR chemical shift (1.25ppm to 0.22ppm), small difference of CSE (conventional strain energy) compared with cyclobutane , 27.5 kcal mol-1 and 26.5 kcal mol-1 respectively. He concluded that σ-Aromaticity energy compensate the high strain energy, and σ-ring induce the diamagnetic property. cyclopropane σ-Conjugation and σ-Aromaticity M. J. Dewar, Bull. Soc. Chim. Belg. 1979, 88, 957-967 Figure1. Magnetic lines of force in cyclopropane.

6. 1 Introduction of σ-Aromaticity The two structure models of cyclopropane Walsh Coulson and Moffitt three trignal near-sp2 methylene carbenes three bent C(sp3)-C(sp3)bonds

7. 1 Introduction of σ-Aromaticity Table1.the deveiopment of cyclopropane of σ-Aromaticity and evaluation criteria.

8. 1 Introduction of σ-Aromaticity References: TheoreticalDetermination of Molecular Structure and Conformation. 1 5. Three-Membered Rings: Bent Bonds, Ring Strain, and Surface Delocalization J. Am. Chem. Soc. 1985, 107, 13, 3805. Nucleus-Independent Chemical Shifts: A Simple and Efficient Aromaticity Probe J. Am. Chem. Soc. 1996, 118, 6317. Theoretical Bond Energies: A Critical Evaluation J. Phys. Chem. A 2001, 105, 3407-3416. Recommendations for the Evaluation of Aromatic Stabilization Energies Org. Lett. 2002, 4, 2873-2876. An Energetic Measure of Aromaticity andAntiaromaticity Basedon the Pauling–Wheland Resonance. Chem. Eur. J. 2006, 12, 2009-2020. The ring current in cyclopropane Theor. Chem. Acc. 2007, 118, 123-127. Is Cyclopropane Really the s-Aromatic Paradigm? Chem. Eur. J. 2009, 15 9730-9736.

9. 1 Introduction of σ-Aromaticity ISE: isomeric stabilization energy The differences between a methyl derivative of the aromatic system and its nonaromatic exocyclic methylene isomer. Recommendations for the Evaluation of Aromatic Stabilization Energies Org. Lett.Vol. 2002, 4, 2873-2876

10. 1 Introduction of σ-Aromaticity ECRE: extra cyclic resonance energy The RE (resonance energy) difference between a fully cyclic aromatic compound and appropriate acyclic model. An Energetic Measure of Aromaticity and Antiaromaticity Based on the Pauling–Wheland Resonance. Chem. Eur. J. 2006, 12, 2009-2020.

11. 1 Introduction of σ-Aromaticity a b Fig. 3 a Current density map for cyclopropane. bthe sum of localised C–H bonds of the cyclopropane molecule. The currentinduced in the plane of the carbon nuclei by a perpendicularexternal magnetic field is calculated at the (CTOCD-DZ/6-31G**//RHF/6-31G**) level. The ring current in cyclopropane. Patrick W. Fowler Theor. Chem. Acc. 2007, 118, 123-127.

12. 2 Computed Methods Opt DFT: B3LYP Base sets: 6-31G* and LanL2DZ NICS DFT: B3LYP Base sets: 6-311++G** and LanL2DZ ASE DFT: B3LYP Base sets: 6-31G* and LanL2DZ

13. 3 Results and Discussion

14. 3 Results and Discussion

15. 3 Results and Discussion Table 2. NICS values [ppm] of non-metal rings1-3 and alkylidene compelexes rings 4-18. a, b These are the average values of above and below center(0) 1Å.

16. 3 Results and Discussion Benzene Fig. 4 Comparison of NICS(0) with NICS(1), and NICS(0)ZZwith NICS(1)ZZ based on the result in table 2.

17. 3 Results and Discussion

18. 4 Further work • Try to find other ways to evaluate σ-Aromaticity energy by VB. • Explain the NICS results reasonably.

19. Thank you !