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Russian Academy of Sciences
A.N.Nesmeyanov Institute of Organoelement
Compounds
Laboratory of molecular spectroscopy
1
IR SPECTROSCOPIC AND THEORETICAL
STUDY OF NEW PHOTOCHROMIC
SYSTEMS BASED ON CYMANTRENE
DERIVATIVES.
B. V. LOKSHIN, M. G. EZERNITSKAYA, Yu. A. BORISOV, E. S. KELBYSHEVA.
N. M. LOIM
2
hL
M
CO
CO CO
M
L
CO CO
L = PR3, P(OR)3, SR2, olefins,
acetylenes and other n- and pdonors
3
1
2
R1 R
CHN-C-OtBu
2
R R
CHN-C-OtBu
crimson
coloration
O
M
CO
CO CO
M
PPh3
CO CO
hPPh3
colourless
R1 = H
R1 = CH3
R1 = CH3
yellow coloration
R2 = H
(1)
R2 = H
(2)
R2 = CH3 (3)
(4)
(5)
(6)
R1 R2
CHN-C-OtBu
M
O
h
CO
CO CO
+CO in closed system
Reverse dark reaction.
O
crimson
coloration
Colored during some
hours at 10-250С
Decomposition
4
Aim of the work:
Study by infrared spectroscopy and quantum chemistry of the
structure and stability of intermediates formed under irradiation of
cymantrene derivatuves containing substituents, which are able
to coordinate to the metal by its n-and π-donor centers
(C=O or C=N group, pyridine or allyl).
Experimental
Photochemical reaction was carried out directly in the cell of the
IR spectrometer, where the solution of tricarbonyl complex was
irradiated with light of immersional mercury lamp Normag
TQ 150. The monitoring the reaction was carried out by IR spectra.
IR-fourier-spectroscopy - Magna-750 Nicolet instrument
UV-VIS spectrocopy - SPECORD М-40 with digital registration.
NMR-spectroscopy.
Circular dichroism spectroscopy.
DFT B3LYP/LanL2DZ calculations. The GAUSSIAN 03 program .
5
Initial carbamate
С5H5Mn(СO)3CH2NHCOtBu
Calculated structures
Reaction product after UV-irradiation and СО removal.
DFT B3LYP/LanL2DZ calculation with full optimization of geometry
6
UV-vis spectra of compound 3
(R1= CH3, R2= H) before and after
5 minute UV irradiation
3,0
Initial
2,5
After irradiation
A
2,0
The spectrum after irradiation is not solventdependent (hexane, benzene, ethanol, THF).
d-d-transition.
1,5
1,0
CH3 H
CH-N-C-OtBu
0,5
0,0
300
400
500
600
O
700
M
л, nm
0,25
CO
CO CO
(R)-isomer 3
(R)-isomer 6
(S)-isomer 3
(S)-isomer 6
(3)
0,20
0,15

CD spectra of (R) and (S) enantiomers 0,10
of compound 3 (R1= CH3, R2= H)
0,05
before and after UV-irradiation
0,00
350
-0,05
400
450
500
550
600
650
, mn
-0,10
7
R1 R2
C-N-C-OtBu
O
Mn
CO
CO
CO
CO
CO
CH2-CH2-C-CH3
O
Mn
CO
CO
h
h
R1
CH N R2
Mn
O C
CO
OtBu
CO
CH2
Mn
CO
CO
CO
O C
CH2
CH3
+
CH2
Mn C CH2
CO
CO O CH3
Organometallic photochromic systems associated with removal and addition of the
ligand and with intermediate stabilized by chelation between metal atom and the
subsituent in Cp-ring.
The process of removal and adddition of CO can be multiply repeated.
DIRECT REACTION takes place with high rate upon irradiation with full light of UV-lamp
or with the light in 300-400 nm region. The semiconvertion time T1/2 is about 3 min.
REVERSE REACTION semiconvertion time T1/2 is 60-90 min.
Upon irradiation with visible light 480-530 nm the reaction accelerates. T1/2 is about 10
min.
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CYMANTRENES WITH BIFUNCTIONAL SUBSTITUENTS
CH2 N
Mn(CO)3
O
Me
C OtBu
CH N CH
Mn(CO)3
N
D
A
O
Me
O
C Me
Me
CH N CH2
Mn(CO)3
C
N
N
C
OtBu
CH N CH2
Mn(CO)3
B
N
Wide range of compounds were also studied in order elucidate the nature
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of the dicarbonyl intermediate stabilization.
Irradiation in benzene solution of (СO)3MnCH2N(COOtBu)Py (A) results in
removal of СО group and formation of dicarbonyl complex. The intensity
of Amide I band is not changed and the pyridine ring stretch is 10 см-1 up
shifted due to coordination with pyridine nitrogen atom.
А
A
B
S
O
R
B
A
N
C
E
3.0
2.5
Absorbance
2.0
2000
1800
Wavenumbers (cm-1)
1600
1.5
430
1.0
b
324
0.5
a
0.0
200
300
400
500
600
700
800
900
1000
wavelength mn
IR and UV-Vis spectra of complex A in benzene solution in the course of irradiation.
10
E0 = 9.1 kcal/mol
CO calc.= 1862, 1917 cm-1
CO exp.= 1866, 1929 cm-1
CH2NC(=O)OtBu
OÑ
CH2NC(=O)OtBu
CO
Mn
CO
h
CO
N
(А)
OÑ
Mn
N
CO
11
A
B
S
O
R
B
A
N
C
E
1620
2000
1800
1600
1600
Wavenumbers (cm-1)
IR spectra of (B) in benzene solution in the course of irradiation
CH3
OÑ
CHNC(=O)R
CH2
Mn
CO
CO
N
CH3
h
CHNC(=O)R
CO
OÑ
CH2
Mn
CO
R = Otert.Bu (B),
Me
(C)
N
12
A
B
S
O
R
B
A
N
B
E
Upon irradiation in benzene of (D)
Mn(CO)3С5H4CH(CH3)N=CHPy the
dicarbonyl chelate with
coordination of imine nitrogen
atom is formed.
2000
1900
Wavenumbers (cm-1)
2.5
A
B
S
O
R
B
A
N
C
E
Absorbance
2.0
1593
1648
1.5
462
1.0
326
0.5
0.0
200
1600
300
400
500
600
700
800
900
1000
wavelength nm
Wavenumbers (cm-1)
Me
h
CHN=CH
OC
N
Mn
CO
CO
CO
CHMe
OC
Mn
CO
N
(D)
CH
N 13
Initial complex D-cis
=1683 cm-1
Coordination with pyridine nitrogen
(СО)=1687 cm -1
Initial complex D- trans
=1684 cm-1
E = 4.5 kcal/mol
Trans-structure is more stable
Coordination at imine nitrogen
(СО)=1647 cm-1
Coordination at imine nitrogen is
3.1 kcal/mol more preferable.
14
1854
1903
0.5
1928
0.5
1966
Absorbance
Absorbance
Differential spectrum
0.0
0.0
2200
20502000
1900
Wavenumbers (cm-1)
2000
1800
Wavenumbers (cm-1)
CH3
CH NCH2CH=CH2
OC
Mn
CO
CO
h
-CO
CH3
COOBut
h
+CO
-CO
CH3
CH
OC
Mn
CO
O=C
NCH2CH=CH2
OBut
OC
Mn
CO
CH NCOOBut
CH2
CH
CH2
15
CH
Mn(CO)3 O
N
CH2
CH
Mn(CO)3 O
1
All
N
C N C OtertBu
Mn(CO)3 Me Me
2
O
R'
CH N C R
Mn(CO)3
All
O
3
4 R= OtertBu, R'= Me
5 R= Me, R'= Me
6 R = OtertBu, R' = H
7 R= Me, R'= H
16
O
h
1
CH
- CO
OC Mn
CO
N
N
CH
CH2
10
1943
2025
O
(CO)2Mn
9
A
B
S
O
R
B
A
N
C
E
CH
+
1
1940
9
10
1878
In hexane and benzene solutions
the products are formed kinetically
independently in the ratio of 1:0.16,
do not convert to one another and
do not form a photochromic pair. In
THF solution 10 isomerizes
irreversibly to 9.
2025
1975
2100
1917
1900
2000
Wavenumbers (cm-1)
17
Structure 9
Pyridine complex
Structure 10
π-allylic complex.
DFT D3LYP/LanL2DZ calculation:
9 is 12.7 ккал/моль more stable than 10
18
Me
h , - CO
3
C CH2CH=CH2

OC Mn
O
OC
NMe
C OCMe
3

C NMeCOOCM
OC Mn
CO
CH
CH2
14
13
3
A
B
S
O
R
B
A
N
C
E
Me
13
14
Upon irradiation of 3 in hexane and benzene,
the kinetically preferable carbamate
complex13 is initially formed. Then a
mixture of carbamate 13 and olefinic 14
complexes is formed. In the dark reaction, 13
isomerizes to thermodynamically more
stable 14. In the closed system the
bands of tricarbonyl complex 3 appear.
No isomerization of olefinic complex to
carbamate upon irradiation was observed.
2000
1900
Wavenumbers (cm-1)
19
3
A
B
S
O
R
B
A
N
C
E
13
14
2000
1800
1600
Wavenumbers (cm-1)
In THF solution the result is the same but all the processes are
faster.
20
2
, CO
h
O
, CO
CO
h
CH2

OC
N
Mn
O
h
N
CO
OC
Mn
CO
CH2
CH
CH2
12
11
Upon irradiation of 2 in hexane the kinetically
more favorable chelate 12 is initially formed
((СО) 1974 и 1916 см-1), then pyridine chelate
11 is formed ((СО) 1936 и 1870см-1).
Upon consecutive irradiation the olefinic complex
transforms to pyridine one. In the dark reaction
11 transforms slowly during 12-48 hours to
2
A
B
S
O
R
B
A
N
C
E
1974
12
1916
11
more stable thermodynamically 12.
1936
1870
Hence 11 и 12 form the photochromic pair.
1900
2000
Wavenumbers (cm-1)
21
Me
4
h, - CO
OC Mn
O
OC
λmax = 516 нм
CH

NCH2CH=CH2
h
C R
16 R = OCMe3
Me
CH NCOR
OC Mn
CO
λmax = 350 нм
h, - CO
4
CH CH2
CH2
15 R = OCMe3
4
A
B
S
O
R
B
A
N
C
E
Complex
1972
1914
1939
16 1870
1700
15
2000
4
upon irradiation forms olefinic
and carbamate 16 chelates in a ratio of 2:1. In
the dark reaction, the carbamate complex
transforms rapidly to olefinic, which after
irradiation forms again the carbamate complex.
Hence, dicarbonyl complexes 16 and 15 form
the reversible photochromic system due to
linkage isomerization in the bifunctional
substituent.
1800
Wavenumbers (cm-1)
15
22
Initial compound 4.
product 16
Mn coordination with
carbamate group
Substance
E, kcal/mol
Q,
kcal/mol.
Initial 4
-
-
Product 16
7.72
31.82
Product
0.00
26.10
15
СО
15 (Mn coordination with allylic group).
*) E – relative energies of isomeric products
Q corresponds to the processes
4 → 16 + СО и 4 → 15 + СО.
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Me
h, - CO
5
OC Mn
O
OC
CH

NCH2CH=CH2
h
C R
λmax = 509 nm
Me
CH NCOR
OC Mn
CO
CH2
18 R = Me
1944
СОЕДИНЕНИЕ 5 (R=Me, R'=Me)
2027
CH CH2
λmax = 331 nm
17 R = Me
5
А
2
h, - CO
1
17
ОБЛУЧАЛИ 1 МИН
А
0,15
Upon irradiarion 5 transforms
mainly to 17, which
isomerizes thermally to 18.
Upon irradiation 18 again
converts to17. Thus 17 and
18 form the reversible
photochromic system
0,10
0,05
0,00
ТЕМНОВАЯ РЕАКЦИЯ
18
А
0,15
0,10
0,05
0,00
1872
А
1940
1917
1975
ОБЛУЧАЛИ 1 МИН ПОСЛЕ ТЕМНОВОЙ РЕАКЦИИ
0,4
0,2
24
2050
2000
1980
1960
1940
1920
Волновое число (см-1)
1900
1880
1860
1840
6,7
h, - CO
CH2 NCOR
OC Mn
CO
h

CH CH2
CH2
CH 2
OC Mn
O
OC
h, - CO
7
NCH2CH=CH2
C
R
19 R = OCMe3, R' = H
20 R = Me, R' = H
Upon irradiation of allylcarbamate
Under experimental condinions, 19
В – coordination of Mn
with carbamate group
21 R = Me, R' = H
6
in hexane, benzene or THF only olefinic chelate
is a thermo- and photostable compound.
19 is
formed.
Stereoisomer 19S
Stereoisomer 19R
С - coordination of Mn with allylic group
The structure С (R-stereoisomer) is more stable then B (ΔE = 7.09kcal/mol) . The
energy difference between stereoisomers R and S is only 0.75 kcal/mol.
25
7
R=Me, R”=H
20
21
20 R=H is 6.08 kcal/mol more stable
Photolysis of allylamide 7 in hexane gives only
olefinic chelate 20. However both chelates 20
and 21 are the reaction products in benzene and
7
A
B
S
O
R
B
A
N
C
E
THF solution
1965
20
1903
21
1927
2000
1854
THF solutions. 21 is the major kinetic product in
the first step of the reaction at temperatures
below 10оС. Then it isomerizes to 20 for several
minutes. The repeated irradiation of benzene
solution of 20 (λmax 333 нм) leads to
isomerization to chelate 21 with the appearance
of red coloration (λmax 517 нм), which in dark
process again transforms to 20.
Hence, between 20 and 21 the reversible
photochromic transition takes place with the
high isomerization rate.
1900
Wavenumbers (cm-1)
26
CONCLUSIONS:
1. By the methods of IR, UV-Vis spectroscopy and quantum chemistry,
the possibility of obtaining photochromic systems based on cymantrene
derivatives containing mono- and bifunctional n-donor and p-donor
substituents was studied.
2. When irradiated by a mercury lamp, the CO molecule is abstracted
from tricarbonyl complexes and dicarbonyl chelates are formed, stabilized by
intramolecular coordination of the manganese atom with a substituent in the
Cp-ring. This changes the color of the solution. In a closed system the CO
molecules released during irradiation adds again to the intermediate and the
initial colour restores. The process can be carried out repeatedly.
3. In the case of cymantrenes with bifunctional substituents,
photochromic systems were found, where the color change occurs due to
linkage isomerization in the substituent.
4. The spectral data agree well with the results of quantum chemical
calculations using DFT theory.
5. As a result of these studies, two- and three-component
photochromic systems were found, where photochromic properties changes in
dependence on CO abstraction and addition or linkage isomerization.
27