XXVIII Reunió Anual XRQTC
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Transcript of XXVIII Reunió Anual XRQTC
From all-metal aromatic clusters to open-shell spherical aromaticity
Jordi PoaterInstitut de Química Computacional
and Departament de Química, Universitat de Girona
• The concept of aromaticity is no longer confined to "carbon chemistry" but can be applied to the entire periodic table.
1985
1991
2001
Fullerenes
2007
All-metal Aromaticity
2005d-orbital Aromaticity
Nanotubes
2008
-Aromaticity
f-orbital Aromaticity
Open-shell spherical aromaticity
• Hückel’s 4n+2 rule
Dnh
n
Aromaticity of (4n+2)p-annulenes with Dnh symmetry comes from the fulfillment of a closed-shell that provides extra stability.
coronene pyrene
Open-shell spherical aromaticity
• Baird’s 4n rule
Dnh
n
Aromaticity of lowest-lying triplet state of(4n)p-annulenes with Dnh symmetry comes from the same-spin half-filled degenerate highest-occupied MOs that provides extra stability.
Open-shell spherical aromaticity
• Hirsch’s 2(n+1)2 rule for spherical aromaticity
2, 8, 18, 32, 50, 72, 98… = 2(n+1)2
2
8
18
32
n = 0
n = 1
n = 2
n = 3
Rotor rigid solution
A. Hirsch, Z. Chen and H. Jiao, Angew. Chem. Int. Ed. 2000, 39, 3915
Open-shell spherical aromaticity
• Hirsch’s 2(n+1)2 rule for spherical aromaticity
Z. Cheng and R. B. Bruce Chem. Rev., 2005, 105, 3613
Open-shell spherical aromaticity
2(n+1)2 Hirsch’s rule
4n lowest-lying triplet excited state Baird’s rule
4n+2 Hückel’s rule
?OPEN-SHELL
CLOSED-SHELL
PLANAR SPHERICAL
Open-shell spherical aromaticity
• 2n2+2n+1 (S=n+1/2) rule for open-shell spherical aromaticity
2
8
18
32
1, 5, 13, 25, 41, 61, 75… = 2n2+2n+1; (S=n+1/2)
n = 0
n = 1
n = 2
n = 3
J. Poater and M. Solà Chem. Commun. 2011, 47, 11647
Open-shell spherical aromaticity• Aromaticity indices
avzzyyxxNICS 3
1
zzzzNICS Magnetic shielding tensor zzNICS
Multicenter delocalization indices
For monodeterminantal WFs:
M. Giambiagi, M. S. de Giambiagi, C. D. dos Santos Silva and A. P. de Figuereido, Phys. Chem. Chem. Phys. 2000, 2, 3381
P. Bultinck, R. Ponec and S. van Damme, J. Phys. Org. Chem. 2005, 18, 706
A = {A1, A2, …, AN}
Niiiii
iiiiiiring ASASASnnIN
N
N 1
21
32211,,,
21)( A
)(2
1)(
)(
AAAP
ringIN
MCI
Open-shell spherical aromaticity
J. Poater and M. Solà Chem. Commun. 2011, 47, 11647
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
Open-shell spherical aromaticity
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 0.011C60
1- Ih 6-MR -1.4 0.017 0.002 S = 11/2
5-MR -19.9 0.049C60
19+ Ih 6-MR -14.9 0.019 0.013 S = 9/2
5-MR -25.3 0.041C60
10+ 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
Open-shell spherical aromaticitySystems 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 0.025C80
8+ Ih 6-MR -7.2 0.011 0.015 S = 0
5-MR -4.0 0.017C80
5- Ih 6-MR -20.8 0.019 0.012 S = 13/2
5-MR -5.5 0.034J. Poater and M. Solà Chem. Commun. 2011, 47, 11647
Open-shell spherical aromaticity
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
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 -(anti)aromaticity of classical organic compounds, but also - or even - and -(anti)aromaticity, thus giving rise to the so-called multifold aromaticity.
All-metal aromatic clusters• The tendency of p-electrons in classical organic aromatic
molecules is always to localize the double bonds (distortive character), against the delocalizing force of the s-electrons.
S.C.A.H. Pierrefixe, F.M. Bickelhaupt, Chem. Eur. J. 2007, 13, 6321
• Thus, while many of the properties attributed to aromaticity derive from the p-electrons, the s-electrons are the ones responsible for the symmetric framework of monocyclic aromatic compounds.
All-metal aromatic clusters• Al4
2- was the first all-metal compounds synthesized, containing a pair of delocalized -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 ( + s p aromatic)
All-metal aromatic clusters
• Are the -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
All-metal aromatic clusters
• Amsterdam Density Functional• BP86/TZ2P, QUILD• Energy Decomposition Analysis
∆E : M2- (aaa) + M2
- (bbb) M42-
∆E = ∆Eprep + ∆Eint
∆Eint = ∆Velstat + ∆EPauli + ∆Eoi
∆Eoi = SG ∆EG
∆Eint = ∆Velstat + “total s” + “total p”J. Poater, F. Feixas, F.M. Bickelhaupt and M. Solà Chem. Commun. 2011, 47, 11647
All-metal aromatic clusters
J. Poater, F. Feixas, F.M. Bickelhaupt and M. Solà Chem. Commun. 2011, 47, 11647
90 91 92 93 94 95 96 97 98 99 100
-30
-20
-10
0
10
20
30
40
50
total s
total p
DVelstat
DEint
J. Poater, F. Feixas, F.M. Bickelhaupt and M. Solà Chem. Commun. 2011, 47, 11647
All-metal aromatic clusters
• Equivalent trends to those found in benzene.
NICS(1b2g)= +10.8ppmNICS(2a1g)=-3.9ppm
ACKNOWLEDGMENTS
Prof. Dr. Miquel Solà (UdG)Dr. Ferran Feixas (San Diego, USA)
Prof. Dr. F. Matthias Bickelhaupt
19/4/2012 Toulouse RECENT ADVANCES IN AROMATICITY 27
http://iqc.udg.edu