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XXVIII Reunió Anual XRQTC

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Presentació feta a la XXVIII Reunió Anual XRQTC celebrada a la Facultat de Biologia de la Universitat de Barcelona els dies 11 i 12 de juny de 2012.

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XXVIII Reunió Anual XRQTC

  1. 1. From all-metal aromatic clusters to open-shell spherical aromaticity Jordi Poater Institut de QuímicaComputacional and Departament de Química, Universitat de Girona
  2. 2. Fullerenes 1985• The concept of aromaticityis no Nanotubes 1991 longer confined to "carbon chemistry" but can be applied 2001 All-metal Aromaticity to the entire periodic table. d-orbital Aromaticity 2005 2007 -Aromaticity f-orbital Aromaticity 2008
  3. 3. Open-shellsphericalaromaticity• Hückel’s 4n+2 rule coronene pyrene Dnh n Aromaticityof (4n+2)p-annuleneswithDnhsymmetry comes fromthefulfillmentof a closed-shellthatprovides extra stability.
  4. 4. Open-shellsphericalaromaticity• Baird’s 4n rule Dnh n Aromaticityoflowest-lyingtripletstateof(4n)p-annuleneswithDnhsymmetry comes fromthesame-spinhalf-filleddegeneratehighest-occupiedMOsthatprovides extra stability.
  5. 5. Open-shellsphericalaromaticity• Hirsch’s 2(n+1)2ruleforsphericalaromaticity Rotor rigid solution n=3 32 n=2 18 n=1 8 n=0 2 2, 8, 18, 32, 50, 72, 98… = 2(n+1)2 A. Hirsch, Z. Chen and H. Jiao, Angew. Chem. Int. Ed. 2000, 39, 3915
  6. 6. Open-shellsphericalaromaticity • Hirsch’s 2(n+1)2ruleforsphericalaromatici ty Z. Cheng and R. B. Bruce Chem. Rev.,2005, 105, 3613
  7. 7. Open-shellsphericalaromaticity PLANAR SPHERICALCLOSED-SHELL 4n+2 Hückel’s rule 2(n+1)2 Hirsch’s rule 4n lowest-lyingOPEN-SHELL triplet excited state ? Baird’s rule
  8. 8. Open-shellsphericalaromaticity• 2n2+2n+1 (S=n+1/2) rulefor open-shellsphericalaromaticity n=3 32 n=2 18 n=1 8 n=0 2 1, 5, 13, 25, 41, 61, 75… = 2n2+2n+1; (S=n+1/2) J. Poater and M. Solà Chem. Commun. 2011, 47, 11647
  9. 9. Open-shellsphericalaromaticity • AromaticityindicesMagnetic shielding tensor Multicenter delocalization indices A = {A1, A2, …, AN} For monodeterminantal WFs: I ring ( A )  n i1  niN S i1i2 A1 S i2i3 A2  S iN i1 AN  i1 ,i2 ,,i N M. Giambiagi, M. S. de Giambiagi, C. D. dos Santos Silva and A. P. de Figuereido,Phys. Chem. Chem. Phys. 2000, 2, 3381 1 MCI ( A )  2N I P( A ) ring ( A) P. Bultinck, R. Ponec and S. van Damme,J. Phys. Org. Chem. 2005, 18, 706
  10. 10. Open-shellsphericalaromaticity Systems symm. NICS(1)zz MCI r(C,C) Spin C202+ Ih -7.4 0.020 1.447 S=0 C207+ Ih -4.0 0.035 1.494 S = 3/2 C205- Ih -18.0 0.024 1.508 S = 7/2 J. Poater and M. Solà Chem. Commun. 2011, 47, 11647
  11. 11. Open-shellsphericalaromaticity Systems symm Ring NICS(1)zz MCI BLA Spin C60 Ih 6-MR 0.8 0.018 0.058 S=0 5-MR 21.5 0.011 C601- Ih 6-MR -1.4 0.017 0.002 S = 11/2 5-MR -19.9 0.049 C6019+ Ih 6-MR -14.9 0.019 0.013 S = 9/2 5-MR -25.3 0.041 C6010+ Ih 6-MR -18.6 0.011 0.030 S=0 5-MR -29.5 0.017 J. Poater and M. Solà Chem. Commun. 2011, 47, 11647
  12. 12. Open-shellsphericalaromaticity Systems symm. Ring NICS(1)zz MCI BLA Spin C80 S6 5-MR 10.7 0.019 S=0 6-MR -5.2 0.012 0.025 5-MR 26.3 0.018 6-MR 11.3 0.014 0.001 6-MR -5.1 0.012 0.025 C808+ Ih 6-MR -7.2 0.011 0.015 S=0 5-MR -4.0 0.017 C805- Ih 6-MR -20.8 0.019 0.012 S = 13/2 5-MR -5.5 0.034 J. Poater and M. Solà Chem. Commun. 2011, 47, 11647
  13. 13. Open-shellsphericalaromaticity Systems symm. NICS(1)zz MCI Spin Ge122- Ih -5.5 0.049 S=0 Ge121- Ih -405.9 0.113 S = 5/2 Ge124+ Ih -69.0 0.088 S=0
  14. 14. All-metal aromatic clusters• All-metal and semimetal aromatic clusters are among the most exciting molecules synthesized since the beginning of the present century.• These compounds can have not only the conventional p-(anti)aromaticity of classical organic compounds, but also - or even - and -(anti)aromaticity, thus giving rise to the so- called multifold aromaticity.
  15. 15. All-metal aromatic clusters• Thetendencyofp-electrons in classicalorganicaromaticmoleculesisalwaystolocalizethedoublebond s (distortivecharacter), againstthedelocalizingforceofthe-electrons. S.C.A.H. Pierrefixe, F.M. Bickelhaupt, Chem. Eur. J. 2007, 13, 6321• Thus, whilemany of thepropertiesattributedtoaromaticity derive fromthep-electrons, the-electrons are theonesresponsibleforthesymmetricframework of monocyclicaromaticcompounds.
  16. 16. All-metal aromatic clusters• Al42-wasthefirstall-metal compoundssynthesized, containinga pair of delocalized p-electrons (orbital 1a2u) and two pairs of -electrons (orbitals 1b2g and 2a1g) that contribute to the overall aromaticity of this species. X. Li, A.E. Kuznetsov, H.F. Zhang, A.I. Boldyrev, L.S. Wang, Science 2001, 291, 859.• Thus, Al42- can be considered as a “3- fold” aromatic system ( + paromatic)
  17. 17. All-metal aromatic clusters• Are the p-electrons of the Al42- cluster distortive, i.e., do they work against the regular "aromatic" structure with delocalized, equivalent bonds? Or is this propensity a characteristic of only classical aromatic organic molecules? J. Poater, F. Feixas, F.M. Bickelhaupt and M. Solà Chem. Commun. 2011, 47, 11647
  18. 18. All-metal aromatic clusters• AmsterdamDensityFunctional• BP86/TZ2P, QUILD• EnergyDecompositionAnalysis ∆E : M2- (aaa) + M2- (bbb) M42- ∆E =∆Eprep + ∆Eint ∆Eint = ∆Velstat + ∆EPauli + ∆Eoi ∆Eoi = SG ∆EG ∆Eint = ∆Velstat + “total ” + “total p” J. Poater, F. Feixas, F.M. Bickelhaupt and M. Solà Chem. Commun. 2011, 47, 11647
  19. 19. All-metal aromatic clusters J. Poater, F. Feixas, F.M. Bickelhaupt and M. Solà Chem. Commun. 2011, 47, 11647
  20. 20. All-metal aromatic clusters504030 total 20 DEint10 0 total p 90 92 94 96 98 100-10 DVelstat-20-30 •Equivalenttrendstothosefound in benzene. J. Poater, F. Feixas, F.M. Bickelhaupt and M. Solà Chem. Commun. 2011, 47, 11647
  21. 21. NICS(1b2g)= +10.8ppmNICS(2a1g)=-3.9ppm
  22. 22. ACKNOWLEDGMENTSProf. Dr. MiquelSolà(UdG) Prof. Dr. F. Matthias Bickelhaupt Dr. FerranFeixas (San Diego, USA)
  23. 23. http://iqc.udg.edu19/4/2012 Toulouse RECENT ADVANCES IN AROMATICITY 27

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