Transcript phenalenyl.ppt

THE PHENALENYL FREE RADICAL
A JAHN-TELLER-HERZBERG-TELLER D3H PAH
G. D. O’CONNOR,
T. P. TROY, D. A. ROBERTS, N. CHALYAVI, B. FÜCKEL, M. J. CROSSLEY, K. NAUTA,
J. F. STANTON and T. W. SCHMIDT
Diffuse Interstellar Bands
10% of light missing
at this wavelength
Hobbs et al a catalog of diffuse
interstellar bands in the
spectrum of HD 204827
due to gas phase molecules… what are they?
Interstellar Carbon
The “Unidentified Infrared Bands”
- believed due to aromatic material in
Interstellar medium.
Aromatic material?
Kwok, Nature 430, 895 (2004)
Cosmic “dust” and RSRs
(Resonance-Stabilized Radicals)
Hydrogenated Amorphous Carbon (HAC)
S. Kwok. Nature 2004, 430, 985–991.
Synthetic chemistry
High Voltage
Discharge
`
`
-H
phenalene
phenalenyl
R2C2PI Spectrum (D1 ← D0)
 01
19560 cm-1
(+760 cm-1)
m/z=165
0 00
Comparison with the DIBs
R2C2PI Spectrum (D1 ← D0)
 01
19560 cm-1
(+760 cm-1)
m/z=165
0 00
Typical origin-dominated spectrum
0 00
21200
19400
20400
Dispersed Fluorescence of Origin
-1
+810cm
807 cm-1

0
0
1
0
0
Dispersed Fluorescence of +760cm-1

1
0


1
2
+1590cm-1
1
0
Behaves like vibrational modes
… look for gradient in transition
moment
13 p-electrons
Cation is 12 p electron
aromatic
(breaks Hückel rule)
Frontier Orbitals
e”
D3h
a1”
e”
Coulson’s Pairing
22E”
21E”
21A
1’
4 one-electron excitations gives 4 states: 2 pairs of E”
Symmetry considerations
A1"  E"
Electronic transition allowed (in-plane)
A1"  E"
Vibronic transition allowed (in-plane)
E"e'  E"
e’ modes allowed (in-plane)
E"a1 '  E"
a1’ modes allowed (in-plane)
CCSD pvdz calculations
Ground state modes near 810cm-1
Mode
Sym
Freq cm-1
31
a2''
784.62
6
a1'
785.65
25
28
e'
a1''
828.32
851.19
R2C2PI Spectrum (D1 ← D0)
 01
19560 cm-1
(+760 cm-1)
m/z=165
0
0
0
25 e’ vibrational modes
Qa
Qb
p/2
p
2p
3p/4
Adiabatic representation
Nuclear Kinetic
 T11 0

ad
H   0 T22
 0 T ad
32

Electronic
0  V11 0
0 



ad
ad
T23    0 V22
0 
ad  
ad 
T33   0
0 V33 

Which is great when we can ignore off-diagonal KE terms…
Move to the diabatic representation
0  V11 0
0 
 T11 0




d
d
d
H   0 T22 0    0 V22 V23 
d  
d
d 
0
0 T33   0 V32 V33 

...
Jahn-Teller diabatic Hamiltonian
0    2
V11 0

 
d
d
 0 V22 V23    0
 0 Vd Vd   0
32
33 


0
   2
0
0  0 0
 
0    0 kQa
   2   0 kQb
Harmonic potential
0 

kQb 
 kQa 
Jahn-Teller
Effect of Jahn-Teller matrix on 25?
 =1
~4cm-1
Effect on the spectrum? Still origin dominated!
0 00
x 50
2510
Frequency (cm-1)
Transition moment suggests coupling to 2E” levels
22E”
|5>
|4>
m=2.5
21E”
|2>
|3>
m=0.06
21A ’
1
|1>
In diabatic representation, this is a manifestation of
pseudo-Jahn-Teller (Herzberg-Teller) coupling
Transition moment suggests coupling to 2E” levels
  2

 0
V  0

 0

 0
0
 2   2
0
0
0
0
0
 3   2
0
0
0
0
0
 4   2
0
0
 0
0
 
0
  0 kQa
   0 kQ
0
b
 
  0  gQa
0
 
 5   2   0 gQb
22E”
|5>
|4>
m=2.5
21E”
|2>
=0
|3>
m=0.06
21A ’
1
|1>
0
kQb
 kQa
gQb
gQa
0
 gQa
gQb
lQa
lQb
Jahn-Teller
Pseudo Jahn-Teller
0 

gQb 
gQa 

lQb 
 lQa 
More or less solved?
Excitation spectrum
CCSD Simulation (Stanton)
Experiment
EOM-CCSD/pJT
People and Money
G. O’Connor
Dr K,Nauta
Dr B. Fückel
Prof. John F. Stanton
Prof. M.J. Crossley
Dr Tyler P. Troy
Dr Nahid Chalyavi
Derrick Roberts
Australian Research Council