An investegation of Rovibrational Interactions in [1.1.1]Propellane, a

Pieces of the
Propellane Puzzle
Robynne Kirkpatrick,a Tony Masiello,b Narumol Jariyasopit,a Joseph
Nibler,a Art Maki,c Alfons Weber,c and Tom Blakeb
bOregon
State University
bPacific Northwest National Laboratory
cNational Institute of Standards and Technology
International Symposium on Molecular Spectroscopy, 2007
?
?
?
1.57 Å
?
[1.1.1]Propellane,
a D3h
hydrocarbon…
1.52 Å
…with a charge distribution that continues
to be a topic of debate!
-Synthesis: Wiberg and Walker, J. Am Chem Soc., 1982, 104, 5239-5240.
-Structure: L. and K. Hedberg, J. Am Chem Soc., 1985, 107, 7257-7260.
Some of the Debate
• Messerschmidt and coworkers used x-ray
diffraction on a derivative that contains of
the propellane skeleton, and found
“…no charge accumulation at the center.”
[Angew Chem, 44, 3925-3928 (2005).]
• Ab Initio calculations with small basis sets
(6-31g*) give what could be interpreted as
conflicting results on the bonding/antibonding
nature of the electrons in the HOMO
[Honneger et al, J Am Chem Soc, 107, 7172 (1985).],
[Sannigrahi and Kar, J Mol Struc; Theochem, 496, 1-17 (2000).]
sv through 3 Cs
LECTRON DENSITY ALONG AXIAL ‘BOND’
What do Ab Initio Calcs Done with a
Larger Basis Set Say about the
Electron Distribution?
Some areas of
relatively low
density
Electron Density:
(Arbitrary Units)
From B3LYP/cc-pvtz
0.75-0.99
1.0-1.25
For [1.1.1]Propellane,
what is the nature of the Highest
Occupied MO?
Singlet state with
large axial lobes
outside the cage
From B3LYP/cc-pvtz
What additional
information can we learn
about Propellane from
results of
-1
high resolution (~0.002cm )
Rovibrational Experiments?
High res spectroscopic results 
●Identify
| n, J, K, l > states
(No K states previously
observed/assigned!)
●Obtain
●
vibration-rotation parameters
Learn about charge flux
(nature of the dipole derivatives)
• Synthesize
Experimental
Protocol: Belzner et al., Chem. Ber. 122, 397-398 (1989)
LiCH3
1,1-dibromo-2,2-bis(chloromethyl)cyclopropane
• Record Spectra
0.5-2 Torr, 285-296K, 352 scans averaged,
Bruker FT120/125
FTIR Spectrometers at PNNL
Bruker IFS
,120/125HR
HR Mirror:
moves 6 m!
Resolution
~0.0015 cm-1
What Can We See at this resolution?
0.06 vs 0.002 cm-1 Resolution
P37
n14 // Band
0.
PK(37)
1070
1080
1090
cm-1
1100
0.06 vs 0.002 cm-1 Resolution
P37
P37
P37
1073.8
1073.9
1074
1074.1
1074.2
1074.3
1074.4
n10 Perpendicular
Band
n10  Band
Q0
cm-1
0.06 vs 0.002
Resolution
1170
1180
-1
1190
cm
1200
Q0
1181.2
1181.25
1181.3
1181.35
1181.4
1181.45
1181.5
1
n15 // Band
n15
Classic P, Q, R band shape
 D3h nuclear spin weights:
K=0: Jodd:2; Jeven:1
K0: 24 for K = mod 3; 20
otherwise
5
Jodd
Jeven
0
y / Arbitrary
590
600
cm-1
610
620
630
Overlay X-Zoom CURS
0.5
n15 Parallel Band
P54 (62)
P52 (62)
0.4
0.8
0.3
Experiment
0.2
Calculated
0.6
0.1
0.0
-0.1
0.4
575.56
575.58
575.60
575.62
0.2
0.0
575.5
575.6
575.7
575.8
575.9
-1
cm576.0
n15 // Band
●Calculated intensities quite good
●1746 transitions assigned
●n15 = 612.31700(2) cm-1
Previous work 611.73 cm-1 (Wiberg et al, 1985)
This work, G03 B3LYP/cc-pVTZ Anharm, 565.8 cm-1
●Rotational parameters for the Ground
state and n15 well-determined
n12  Band
n12 (E′)
Intensity
perturbation!!
vs.
500
500
520
520
540
540
cm-1
560
560
Likely Perturbation Source:
z12,15 Coriolis Interaction
●
15 Tq(1) 12  0 ?
A  E  E (a rot. species )
''
2
'
''
2
● Are the energy levels close?
 Yes!
 Yes!
ycoupled = ay12+ + by15 + cy12–
Coriolis Coupling Operator:
Hcor ~  BQ(P J  P J )
y
 
m
 
m
Q = +/- operator for n15
P’s = +/- ops. for n12
J’s = +/- ops. for rotational angular momentum
(molecule rotating frame)
 Nonvanishing matrix elements:
±2½(Bzy)[J(J+1) – K(K±1)]½
DK = ±1, Dl = ±1
For Frequency Fit,
Estimate - zy
Use Normal Coordinate Components
(fromB3LYP/cc-pvtz)

 y  atoms L
(n 15 )
X atoms L
(n 12x )
= -0.4
Q15 (A2’’)
●Yellow Arrow = Dipole Derivative
● Black Arrow = Displacement Vector
Atom
1
2
3
6
7
4
8
9
5
10
11
C
C
C
H
H
C
H
H
C
H
H
Z
0.38
0.38
-0.20
-0.31
-0.31
-0.20
-0.31
-0.32
-0.20
-0.32
-0.31
Q12 (E′)
Atom
1
2
3
6
7
4
8
9
5
10
11
C
C
C
H
H
C
H
H
C
H
H
X
-0.09
-0.09
0.17
0.41
0.41
-0.03
-0.13
0.19
-0.03
0.19
-0.13
Y
0.00
0.00
0.00
0.37
-0.37
0.12
0.31
0.13
-0.12
-0.13
-0.31
Frequency Fit
●2244 n12 lines + 1746 n15 used
●Fitting of Energy Parameters Good
n12 = 531.49912(2)cm-1
G03 B3LYP/cc-pVTZ pair: 527.1
and 536.2
Ave. = 531.7
(previous work, 529, Wiberg et al)
n12 Rotation-Vibration Parameters
Extent of the z12,15 Coupling for
ycoupled = ay12+ + by15 + cy12–
J  55, K  45, l  1
'
'
'
b = 0.073
0.5% n15
J  55, K  15, l  1
'
'
'
b = 0.109
1.1% n15
 Relatively small amount of n15 in vector composition
But the Intensities are Off!
1.5
p
Expt
Calc intensity if no
perturbation
p
P24 (24)
P6 ( 22)
1
.5
4
518.93
518.94
Arbitrary / Wavenumber (cm-1)
File # 2 : NU12INTNOCPL
2
Intensities
scaled to
unperturbed
lines
0
500
520
540
Arbitrary / Wavenumber (cm-1)
File # 2 : NU12INTNOCPL
560
Overlay X-Zoom CURSOR
cm-1
Res=None
Assume Icoupled ~
|m′1212+ + m′15  15 + m′12  12– |2
Where i is the product of the coupling
coefficient, Boltzmann factor, spin weight,
frequency, and S
 TK(1'K)
J 'J
[DiLauro and Mills, J Mol Struc; Theochem, 21, 386-413 (1966).]
 μ 
μ
 Q
 Q Q0
 μ 
μ'  

 Q  Q0
Intensity Fit for Coupled n12, n15
●Use a least squares regression on
intensities to fit the dipole derivative ratio
●701 isolated lines used
●Used ”One side” transitions (pP and rR)
●K > 4
Calc vs Expt Intensity
Fitted m'z(15)/m'x(12)  35.2
20
10
2
R = 0.8782
0
0
10
20
Ab Initio value from B3LYP/cc-pVTZ is
|m’15/m’12| = 28.9
30
n12  Band
Expt
p
1.5
Calc intensity m’15/m’12
= 35.2 using z negative
p
r
P5 ( 21)
P6 ( 22)
P24 (24)
1
Calc No Coupling
.5
0
518.92
518.93
518.94
Arbitrary / A rbitrary
5
Ov e
File # 1 = PROP_350-700WC
500
/ Wavenumber (cm-1)
520
cm-1
540
560
Ov erlay X-Zoom CURSOR
Discussion of the Intensities
●n15 a high dipole derivative relative
to n12 --most n15 band lines off
scale relative to n12
● n15 oscillation associated with
considerable charge flux
● Effective dipole derivative of
n15 has a very small
projection onto
the x-y plane if
n12 is excited
500
Arbi trary / Arbi trary
Fi l e # 2 : 350-700WCZAP
n15
550
6
HOMO
LOW ELECTRON DENSITY ALONG AXIAL ‘BON
Large dipole derivative associated with n15 
Perhaps the relative axial electron
distribution outside the depleted region is
significant, and it moves with each axial C
during a n15 oscillation
e- density
slice
through sv
and 3 Cs
Summary
High resolution studies of propellane 
Accurate vibration-rotation parameters
determined and in compared w/
B3LYP/cc-pVTZ anharmonic calcs
 Coriolis coupling found between n12 and n15;
dipole derivatives assessed and compared
favorably with ab initio calcs
Charge densities and charge flux studied
using B3LYP/cc-pVTZ

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