welcome professor lin to direct our group!
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Welcome Professor Lin to direct our group!. 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. - PowerPoint PPT PresentationTRANSCRIPT
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
σ-Aromaticity Review and σ-Aromaticity investigation of 3MRs transition metal
alkylidene complexes
Reportor: Yulei Hao
Advisor: Jun Zhu
Introduction of σ-Aromaticity 1
Computed methods2
Results and Discussion3
Further work4
4
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.
5
Introduction of σ-Aromaticity 1
cyclopropane
σ-Conjugation and σ-Aromaticity
M. J. Dewar, Bull. Soc. Chim. Belg.
1979, 88, 957-967
H
H
H
H
H
H
Figure1. Magnetic lines of force in cyclopropane.
6
Introduction of σ-Aromaticity 1
The two structure models of cyclopropane
H2C CH2
CH2
Walsh Coulson and Moffitt
three trignal near-sp2 methylene carbenes three bent C(sp3)-C(sp3)bonds
7
author concept
Method orconclusion
1979 Dewar σ-Aromaticityproposed σ-ring current and aromaticity energy
1985 Cremerelectron density and surface delocalization
ab initio caculation
1996 Schleyer NICS valuesabsolute magnetic shieldings coputed at ring centers
2001 Schleyerintrinsic bond energy
evaluate ASE (11.3 kal.mol-1)
2002 Schleyer ISE simple way to evaluation ASE
2005 SchleyerECRE(extra cyclic resonance energy)
evaluation ASE and correlated well with NICS
2007 Folwer σ-ring current coupled Hatree-Fock "ipsocentric"
2009Wu Wei and Schleyer
VBSCF motheod, ECRE small σ-ASE (3.5 kal mol-1)
Introduction of σ-Aromaticity 1
Table1. the deveiopment of cyclopropane of σ-Aromaticity and evaluation criteria.
8
J. Am. Chem. Soc. 1996, 118, 6317.
Introduction of σ-Aromaticity 1
Theoretical Determination 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 Simpleand Efficient Aromaticity Probe
Is Cyclopropane Really the s-Aromatic Paradigm?
Chem. Eur. J. 2009, 15 9730-9736.
Theoretical Bond Energies: A Critical Evaluation
J. Phys. Chem. A 2001, 105, 3407-3416.
References:
The ring current in cyclopropane Theor. Chem. Acc. 2007, 118, 123-127.
Recommendations for the Evaluation of Aromatic Stabilization Energies Org. Lett. 2002, 4, 2873-2876.An Energetic Measure of Aromaticity andAntiaromaticity Basedon thePauling–Wheland Resonance. Chem. Eur. J. 2006, 12, 2009-2020.
9
Org. Lett.Vol. 2002, 4, 2873-2876
Recommendations for the Evaluation of Aromatic Stabilization Energies
ISE: isomeric stabilization energy
The differences between a methyl derivative of the aromatic
system and its nonaromatic exocyclic methylene isomer.
Introduction of σ-Aromaticity 1
ISE=35.3kcal/mol
10
ECRE: extra cyclic resonance energy
The RE (resonance energy) difference between a fully
cyclic aromatic compound and appropriate acyclic model.
X X
ERc
X ERa
X
ECRE= ERc - ER
a
Introduction of σ-Aromaticity 1
An Energetic Measure of Aromaticity and Antiaromaticity Based on the Pauling–Wheland Resonance. Chem. Eur. J. 2006, 12, 2009-2020.
11
Introduction of σ-Aromaticity 1
a b Fig. 3 a Current density map for cyclopropane. b the sum of localised C–H bonds of the cyclopropane molecule. The current induced in the plane of the carbon nuclei by a perpendicular external 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
Computed Methods2
OptDFT: B3LYPBase sets: 6-31G* and LanL2DZ
NICS DFT: B3LYPBase sets: 6-311++G** and LanL2DZ
ASEDFT: B3LYPBase sets: 6-31G* and LanL2DZ
13
Mn
O
H2N
OC
OC CO
Mn(4)
NH2
1.908
2.18
7
2.19
2
2.25
3
1.430
1.4101.414
FeOC
OC CO
NH2
NH2
Fe(5)
O
1.89
2
2.28
6
1.94
9
1.406
1.4597
Cr
O
H2N
H2N
NH2
O
Cr(6)
1.873
2.193
1.437
Nb
OH3SiNH
H3Si
H2P PH
ClH2P PH2
2.073
2.0971.357
Nb(7)
benzene(1)
1.398
cycloprapene(2)
1.2921.
510
1.51
0
cyclopropane(3)
1.509
W
F3C
F3C
W.1(8)
CF3
CF3
Cl
Cp
C
NH
1.926
2.567
1.48
3
2.075
2.058
1.30
5
W COOC
F3C
CF3
FNH2NF
F
F F
W.2(9)
1.951
2.224
1.442
WPh
Cl
ON
Cp
W.3(10)
2.087
2.675
1.35
7
Mo
H3P
H3P
Cp
Mo.1(11)
1.9382.303
1.42
5
Mo CF3
CF3
Cp
Mo.3(13)
F3C
F3C
N
S
2.133
1.29
0
1.919
2.224 1.41
9
2.089
Mo
H3P
H3P
Cp
Mo.2(12)
1.946
2.278
1.42
9
SiH3
Results and Discussion3
14
Re
H3P
H3P
PH3
Cl
Re.1(16)
1.995
2.219
1.3181.3
76
1.41
9
1.395
2.051
Re
PH2
PH2
Cp
Re.2(17)
1.902
2.273
1.40
8
ReOC
Re.3(18)
Cp
CO
1.975
2.264
1.40
5
OsH
Os.1(14)
PH3
PH3
O
O
1.932Ph
OsH
PH3
PH3
O
F
F
F
F
Ph
Os.2(15)
1.977
2.167
1.41
3
Results and Discussion3
15
NICS(0) NICS(0)ZZ NICS(1) a NICS(1)ZZ b
1 -8.1 -14.5 -10.2 -29.12 -28.3 -18.2 -6.9 -15.13 -42.4 -29.8 -8.6 -24.24 -33.8 -59.1 -18.8 -21.45 -20.2 -41.7 -13.5 -16.96 -39.5 -65.6 -18.9 -24.97 -31.6 -54.6 -24.1 -35.98 -25.2 -21.2 -17.6 -20.29 -35.7 -51.5 -16.5 -22.4
10 -13.2 -25.5 -9.6 -11.511 -36.6 -60.5 -20.2 -29.612 -36.0 -63.0 -18.4 -28.113 -33.5 -55.3 -17.1 -25.814 -47.5 -65.4 -19.2 -30.015 -33.2 -42.4 -16.3 -24.416 -45.5 -69.6 -18.5 -25.717 -39.0 -49.0 -19.1 -25.818 -31.7 -41.2 -17.0 -24.4
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.
Results and Discussion3
16
Results and Discussion3
Fig. 4 Comparison of NICS(0) with NICS(1), and NICS(0)ZZ with NICS(1)ZZ based on the result in table 2.
Benzene
17
Results and Discussion3
Mn
O
H2N
OC
OC CO
NH2 +
Mn
O
H2N
OC
OC CONH2
27.8
FeOC
OC CO
NH2
NH2
O
FeOC
OC CO
NH2
NH2
O
+ 30.6
W
PhCl
ON
Cp
+ W
Cl
ON
CpPh
49.6
Re
OC
Cp
CO
+Re
OC
Cp
CO20.5
Cr
O
H2N
H2N
NH2
OH+
Cr
O
H2N
H2NO
H2N
32.5
18
Further work4
• Try to find other ways to evaluate σ-Aromaticity
energy by VB.
• Explain the NICS results reasonably.
19
Thank you !