1. Time-resolved infrared diode laser spectroscopy of the n1 band of CoNO
Takeo Soejima, Motoki Nakashima, Seiki Ikeda,
and Keiichi Tanaka
The title on my talk is “Time-resolved infrared diode laser spectroscopy of CoNO”.
Department of Chemistry, Faculty of Science, Kyushu University, Japan
(Columbus, Ohio, June , FD04 )

2. Matrix isolation + Ablation
Previous Works on CoNO
CoNO production
1800 cm-1
1900
Abs.
Matrix isolation + Ablation Co
Ne + NO
Yag laser (1064 nm)
CsI NO Ne
Ne-Matrix
This spectrum is reported by Andrews in Ne-Matrix, using laser ablation technique, and this signal is assigned to NO stretch of CoNO, together with these other molecule around 1800 to 1900 cm-1 region.
And each three vibrational frequencies were reported as this. V1 NO strech as this in Ne-Matrix. V2 bending as this by calculation. And v3 Co-N stretch as this in Ar-Matrix.
M. Zhou and L. Andrews, J. Phys. Chem. (2000).
　n1 (N-O str.) : cm-1 (Ne-Matrix)
n2 (bend.) : (calc.)
n3 (Co-N str.) : (Ar-Matrix)　　

3. MMW spectroscopy of CoNO
(cm-1)
G.S. n1 n2
2n2 n3
2000
1000
(RF12) OSU symposium (2004).
CoNO
→　1S
n1 state is not observed
Rotational spectrum of G.S.
No splitting due to electron spin and orbital
linear
High resolution infrared spectroscopy
n1 band
This is the rotational spectrum of ground state of CoNO observed by millimeter-wave spectroscopy together with v2, 2v2, and v3 state.
It was confirmed CoNO has singlet sigma electronic ground state and linear, because no splitting due to electron spin and orbital electron were observed. And we reported in this symposium last year.
However, the v1 state is not observed . So, in the present study, we performed high resolution infrared spectroscopy to this molecule. And measured the v1 band.

4. Experiment 1774 ~ 1799 cm-1 NO 193 nm ArF CoNO Co CoCO photolysis OC
diode laser
1774 ~ 1799 cm-1
Co(CO)3NO
193 nm
CoNO
P.D
CoNO was produced by photolysis with UV laser of Co(CO)3NO. By photolysis with ArF, not only CoNO but also CoCO are produced.
The absorption cell used in thie experiment is shown here. From this window UV laser was introduced into the cell to produce CoNO. From the opposite side , infrared diode laser was introduced and traveled by White-type multi-reflection optics and Infrared laser was detected. this region was measured. Ar Ar
Pump
A/D
MCT detector
Amp.
Computer

5. Observed Spectrum n1 fundamental n0 (cm-1) 1779.0 1775.0 1776.0 1778.0
1777.0
1788.0
1789.0
1794.5
1798.0
(cm-1)
1786.0
1787.0
1782.0
1783.0
1784.0
1785.0
P (27)
P (28)
P (29)
P (30)
P (31)
P (36)
P (37)
P (42)
n1 fundamental
P (54)
P (58)
P (53)
P (52)
P (51)
P (50)
P (49)
P (48)
P (55)
P (47)
P (5)
R (4)
R (6)
P (20)
P (21)
P (22)
P (24)
P (25)
P (26) n0
The observed spectrum between 1775 and 1800 cm-1 is shown here.
The strong lines colored in red were assigned to the v1 fundamental band.
P-branch so here up to R-branch 4 6 were observed.
Brow up of these blue regions will be shown in the next. First this one.

6. Observed Spectrum n1 band P (30) n1 + n3 - n3 l-type doubling linear
n1 fundamental
P (51)
P (50)
P (49)
n1 + n2 - n2
P (30)
P (29)
P (28)
l-type doubling
linear
n1 + 2n2 - 2n2 (D)
P (5)
P (4)
n1 + 2n2 - 2n2 (S)
P (12)
P (11)
P (31)
P(30)
P (29)
n1 + n3 - n3
Here is the observed spectrum around 1778 cm-1.
we assigned these blue lines to the hotband from v2 state. These signals split into l-type doublet.
The hot band from 2v2 state were split into two components.
The ot band from v3 state also observed as shown in pink.
. Unassigned these small signals are presumably the hotband from more highly excited states.

7. Observed Spectrum 1786.5 1787.0 cm-1 n1 band n1 fundamental P(29)
n1 + n2 – n2　
P(3)
P(4)
P(5)
n1 + 2n2 - 2n2 (S)
R(15)
R(16)
R(17)
n1 + 2n2 - 2n2 (D)
R (23)
R (24)
R (25)
R (26)
Here is the observed spectrum around 1787 cm-1.
Fortunately, in this region almost of absorption lines could be assigned as this.
Similarly we observed P-branch lines of v1 fundamental and hotband from v2 around this frequency region.
and R-banch hotband lines from 2v2 are shown here.
1786.5
1787.0
cm-1

8. Observed infrared bands
(cm-1)
n1+2n2(D,S)
2n2(D,S)
n1+ n3 n3
n1 + n2 n2
2000 n1
1000
Observed transitions are summarized here.
The v1 fundamental and hotband from v2 2v2 and v3 were assigned.
Ground State

9. Molecular Constants r n1 fundamental constant unit
n (49) cm-1
B (25) MHz
D (80) kHz
B (29) MHz
D (13) kHz
・ Ne-Matrix
cm-1
(79)
(42)
MMW a2 a3
Be = (51) MHz
a1 = (28) MHz
Obtained molecular constants for v1 fundamental are shown here. The v0, B1, D1, B0, D0, and vibration rotation constant alpha 1 are shown here. The band origin is very close to the the observed value in Ne-Matrix.
we also obtained these accurate value by millimeter wave spectroscopy results.
And the equilibrium rotational constant Be was for the first time derived as this.
this Co-N bond length of CoNO was calculated as this assuming N-O to be calculated value.
This bond length is shorter by point 1 A than this bond length of CoCO.
This suggest this bond is stronger than this bond. Co N O
Co – C – O
1.688 A o
1.583 A
1.182 (DFT)
Bond strength
Co – N 　>　Co – C
0.1 A shorter
< r
C-O

10. NO and CO stretch frequency and Force constant shift
cm-1
40 % decrease
2163 cm-1 (1891 N/m)
(1143) CO
CoCO
Dn =190 cm-1 ~
20 % decrease
1875 cm-1 (1549 N/m)
(1252) NO
CoNO ~
Dn =80 cm-1
Force Constant
Freq.
2 times larger
Electronic configuration
<
red shift
The frequency and force constant shift of NO stretch are shown here.
The decrease of NO frequency and force constant are shown as this.
We have similar effect in the case NO is changed into CO.
The shift of CO frequecy and force constant are shown as this. The red shift of this case is 2 times larger than this.
Where does 2 timesf come from. This fact is explained by the electronic configurartion.

11. Electronic ConfigurationNO
CoNO 1S
CoCO 2D CO 5s
2p* p* 4s 3d s p d s* Co
p back donation
Here is the electronic configuration of CoNO.
It is come from electronic orbital of Co and NO as shown here.
This pi orbital of CoNO has the character of mixing anti-bonding pi* of NO. CoNO has four electrons in this pi orbital. So, the NO bond of CoNO is weaker than NO molecule. This effect is called pi back donation.
However, situation much differ when this ligand is changed to CO.
Here is the electronic configuration of CoCO. The difference is NO molecule already has one unpaired electron in this orbital, but CO has no electron in anti-bonding pi* orbital. Therefore, The effect of pi back donation is 2 times larger than CoNO.

12. NO frequencies shift of Metal-NO in Ne-Matrix
1900
NO　1875 cm-1
(cm-1)
NO frequencies of transition metal mytrosyl in Ne-Matrix are illustrated here. Observed CoNO frequecy and is located here. And NO molecule is here.
These decreased frequencies are characteristic phenomena of these molecule.
Sc Ti V Cr Fe and Co are supported to be linear. However, Ni and Cu are supported to have a bent form.
1500 Sc Ti V Cr Mn Fe Co Ni Cu
(M-NO)
1A’
2A’
1A’
2A’’
3A’’ 2D 1S
2A’
1A’
(state)
linear
Lester Andrews and Angelo Cita, Chem. Rev. (2002)

13. Rotational Constants shift
B (MHz)
2n2 (D) ●
8.3 MHz
4690 n2 ●
2n2 (S) ●
G.S.
n1+2n2 (D)
4670 ● ●
6.2 MHz
n1+n2 ●
n1+2n2 (S)
4650 ● n1 ● 1 2
(v2) S
2n2 D
n3 (S)
Fermi interaction

14. Band origin value X12 : anharmonic term of vibration 2X12 (16.7 cm-1)
n1 + n2 - n2　　
Unit
n1 +2n2 - 2n2 S D
n1+n3 - n3
cm-1 n0
n1 fundamental
X12 : anharmonic term of vibration
2X12 (16.7 cm-1)
2n2 (S)
n3 (S)
closely located states
Fermi Interaction
X12 (8.3 cm-1)
The Band origin values are shown here in table and figure.
This distance is nearly twice as this. X12 is called anharmonic term of vibration.
The band origin of 2v2 sigma state shift to this direction,
Because this 2v2 delta state and v3 vibrational states are located closely each other, therefore affected by Fermi interaction. Unperturbed v3 state is expected to located here.
2n2 (D)
n2 hotband
n1 fundamental
2n2 (S)
n3 (S)
2.3 cm-1
(cm-1)
1780
1790
1800

15. Conclusions
High resolution infrared spectroscopy on CoNO were performed,
and　n1 fundamental, n1 + n2 - n2 , n1 + n3 - n3, and
n1 + 2n2 - 2n2 were assigned.
・　The equilibrium structure was determined as follows. Co N O
1.583 A
1.182 A (Fix) Be
(51)
MHz a1
(28) o
This is the conclusion of this work. Thank you for your attention.
The decrease of frequencies of NO stretch was explained
by p back donation.

16. Loomis – Wood Diagram R ・・ 3 1774.0 cm-1 P ・・ 29 n1 fundamental
n0 ( cm-1)
P ・・ 29
R ・・ 3
n1 fundamental
cm-1

17. Loomis – Wood Diagram 1774.0 cm-1 P ・・ 21 n0 (1787.96979 cm-1)
n1 + n2 – n2
cm-1

18. Energy diagram ( ) ( ) cm-1 S D DE+2 DE’+2 + 1779.523 cm-1 =
n1 +2n2 - 2n2
n1 +n3 - n3
DE’=63.34 cm-1
DE+2 w2 DE
( )
DE’+2
DE’
1779.5
1788.8
cm-1 = w2 DE
DE’
cm-1
DE+2
( )
cm cm-1 =
DE’+2

19. Rotational constant shiftB
Bn1+2n2 (S)
(6.2 MHz) w
DE’
( )2 DB
B0n1+2n2 (S) -
DB (40 MHz) w
DE’
( )2 DB
B0n1+n3 +
(6.2 MHz)
Bn1+n3
DE’= cm-1

20. ~ ~ Frequency shift CO 2163 CoCO 1974 NO 1875 CoNO 1796 Dn =189 cm-1
½ times
FN-O
FC-O
CO ・・・ 1891 N/m
NO ・・・ 1549 N/m
CoNO ・・・ 1252 N/m
CoCO ・・・ 1143 N/m
19 % decline
40 % decline
½ times

21. Introduction Previous Works n1 (N-O str.)・・1794.2 (Ne-Matrix)
Transition metal NO
CoNO +
degenerated d-orbital
Air pollutant
prototype
c.f. FeNO
Previous Works
Ne Matrix
Matrix Isolation ＆ ab initio calculation
　n1 (N-O str.)・・ (Ne-Matrix)
n2 (bend.) ・・ (DFT)
n3 (Co-N str.)・・ (Ar-Matrix)
M. Zhou and L. Andrews, J. Phys. Chem. (2000).

22. Molecular Constants Co N O G. S. Be 4676.949 (51) MHz a1 31.325 (28)
Unit Be
(51)
MHz a1
(28) a2
(79)
MMW a3
(42) Co N O
1.583 A
1.182 A (Fix)
cf. Co – C – O o o
shorter o
1.688 A
Force Constant
FCo-N = 510 N/m
FCo-C = 427 N/m
Bond strength
Co – N 　>　Co – C

23. - : M + + N O M N O - + - - + - + N : M O : : M N O - - + - + + +