1

Russian Academy of SciencesA.N.Nesmeyanov Institute of Organoelement

CompoundsLaboratory of molecular spectroscopy

2

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

3

hLM

COCOCO

M

COCOL

L = PR3, P(OR)3, SR2, olefins, acetylenes and other n- and -donors

4

colourless

+CO in closed systemReverse dark reaction.

Colored during some hours at 10-250С

Decomposition

R1 = H R2 = H (1) (4)R1 = CH3 R2 = H (2) (5)R1 = CH3 R2 = CH3 (3) (6)

hPPh3

R1

CHN-C-OtBu

O

R2

crimsoncoloration

R1 R2

COCOCO

yellow coloration

CHN-C-OtBu

O

COCOPPh3

M M

h

R1

CHN-C-OtBu

O

R2

crimson coloration

COCOCO

M

5

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).

ExperimentalPhotochemical 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 instrumentUV-VIS spectrocopy - SPECORD М-40 with digital registration.

NMR-spectroscopy.Circular dichroism spectroscopy.

DFT B3LYP/LanL2DZ calculations. The GAUSSIAN 03 program .

6

Initial carbamate С5H5Mn(СO)3CH2NHCOtBu

Reaction product after UV-irradiation and СО removal.DFT B3LYP/LanL2DZ calculation with full optimization of geometry

Calculated structures

7

UV-vis spectra of compound 3 (R1= CH3, R2= H) before and after 5 minute UV irradiation

CD spectra of (R) and (S) enantiomersof compound 3 (R1= CH3, R2= H) before and after UV-irradiation

The spectrum after irradiation is not solvent-dependent (hexane, benzene, ethanol, THF). d-d-transition.

300 400 500 600 7000,0

0,5

1,0

1,5

2,0

2,5

3,0

л, nm

A

Initial

After irradiation

350 400 450 500 550 600 650

-0,10

-0,05

0,00

0,05

0,10

0,15

0,20

0,25

, mn

(R)-isomer 3 (R)-isomer 6 (S)-isomer 3 (S)-isomer 6

(3)

CH-N-C-OtBu

O

COCOCO

M

HCH3

8

Mn

R1R2

C-N-C-OtBu

OCO CO

CO

Mn

CO CO

R1

R2

OOtBu

CNCHh

CO

Mn

CO COCO

O

CH2-CH2-C-CH3hCO Mn

CO COO

CH3

C

CH2CH2

MnCO

CO O CH3C

CH2CH2

+

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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Mn(CO)3N

NCH2 C

O

OtBu

Mn(CO)3N

CHCH N

Me

N

CH2CH N

Me C

O

Me

Mn(CO)3 N

CH2CH N

Me C

O

OtBu

Mn(CO)3

Wide range of compounds were also studied in order elucidate the nature of the dicarbonyl intermediate stabilization.

D

C

CYMANTRENES WITH BIFUNCTIONAL SUBSTITUENTS

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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.

A B S O R B A N C E

1600 1800 2000

Wavenumbers (cm-1)

IR and UV-Vis spectra of complex A in benzene solution in the course of irradiation.

200 300 400 500 600 700 800 900 1000

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Abs

orba

nce

wavelength mn

430

324

a

b

А

11

E0 = 9.1 kcal/mol

CO calc.= 1862, 1917 cm-1

CO exp.= 1866, 1929 cm-1

MnCO

COOÑ

CH2NC(=O)OtBu

N

CO

h

Mn

COOÑ

CH2NC(=O)OtBu

N

(А)

12

A B S O R B A N C E

1600 1800 2000

Wavenumbers (cm-1)

IR spectraf (B) in benzene solution in the course of irradiation

1600 1620

CO

h

MnCO

COOÑ

CHNC(=O)RCH2

Mn

COOÑ

CHNC(=O)R

N

CH2

N

CH3 CH3

R = Otert.Bu (B), Me (C)

13

A B S O R B A N B E

1900

2000

Wavenumbers (cm-1)

1593

1648

A B S O R B A N C E

1600

Wavenumbers (cm-1)

200 300 400 500 600 700 800 900 1000

0.0

0.5

1.0

1.5

2.0

2.5

Ab

sorb

an

ce

462

326

wavelength nm

Upon irradiation in benzene of (D) Mn(CO)3С5H4CH(CH3)N=CHPy the

dicarbonyl chelate with coordination of imine nitrogen atom is formed.

CHN=CH

MnCO

COOC

N

Me

NCH

Me

Mn

COOC

CH

N

hCO

(D)

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Initial complex D- trans=1684 cm-1

Initial complex D-cis СО =1683 cm-1

Coordination with pyridine nitrogen(СО)=1687 cm -1

Coordination at imine nitrogen(СО)=1647 cm-1

E = 4.5 kcal/molTrans-structure is more stable

Coordination at imine nitrogen is 3.1 kcal/mol more preferable.

15

0.0

0.5

Ab

sorb

an

ce

1900 2000 2000 2050

Wavenumbers (cm-1)

185

4

190

3 1

928

196

6

0.0

0.5

Abs

orba

nce

1800 2000 2000 2200 Wavenumbers (cm-1)

Differential spectrum

Mn

COOC

CH

CH3

NCH2CH=CH2

OButO=C CH

CH2

Mn

COOC

CH

CH3

NCH2

COOBut

-COh

h-CO

MnCO

COOC

CH

CH3

NCH2CH=CH2

COOBut

+CO

16

1 2 3

R = OtertBu, R' = H

R= Me, R'= H

R= Me, R'= Me

4 R= OtertBu, R'= Me

CH

OMn(CO)3

NCH

O

CH2

Mn(CO)3

NC N C

OAll

Me Me

OtertBu

Mn(CO)3

CH N C

O

R

All

R'

Mn(CO)3

7

6

5

17

1943

2025

1878

1917

1940

1975

2025

ABSORBANCE

1900 2000 2100

Wavenumbers (cm-1)

1

910

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.

CH

O

CH

N

h

(CO)2Mn

CH2

MnOCCO

CH

O

N

+1- CO

9 10

18

Structure 9Pyridine complex

Structure 10π-allylic complex.

DFT D3LYP/LanL2DZ calculation: 9 is 12.7 ккал/моль more stable than 10

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ABSORBANCE

1900 2000

Wavenumbers (cm-1)

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.

13

14

h3

, - CO

13 14

MnOCCO CH2

CH

C

Me

NMeCOOCMe3C

NMe

Me

CH2CH=CH2

C OCMe3

MnOCOC O

3

20

ABSORBANCE

1600 1800 2000

Wavenumbers (cm-1)

In THF solution the result is the same but all the processes are faster.

3

13

14

21

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

more stable thermodynamically 12.

Hence 11 и 12 form the photochromic pair.

1870

1916

1936

1974

A B S O R B A N C E

1900 2000

Wavenumbers (cm-1)

12 11

h h

h

, CO

MnOC

CO N

OCH2

O

CH2CH

CH2

MnOC

CO

N

CO

, CO

2

11 12

2

22

1700 1870

1914

1939

1972

ABSORBANCE

1800 2000

Wavenumbers (cm-1)

Complex 4 upon irradiation forms olefinic 15

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.

λmax = 516 нм λmax = 350 нм

15

16

4

16 R = OCMe315 R = OCMe3

h

CH

NCH2CH=CH2

Me

C RMnOC

OC O

CH NCOR

CH CH2

Meh, - CO h, - CO

CH2

MnOCCO

44

23

Initial compound 4. product 16

15 (Mn coordination with allylic group).

Mn coordination withcarbamate group

Substance E, kcal/mol Q, kcal/mol.

Initial 4 - -

Product 16 7.72 31.82

Product 15 0.00 26.10

СО

*) E – relative energies of isomeric products Q corresponds to the processes 4 → 16 + СО и 4 → 15 + СО.

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1944

2027

СОЕДИНЕНИЕ 5 (R=Me, R'=Me)

1

2

А

ОБЛУЧАЛИ 1 МИН

0,00

0,05

0,10

0,15

А

ТЕМНОВАЯ РЕАКЦИЯ

0,00

0,05

0,10

0,15

А

1872

1917

1940

1975ОБЛУЧАЛИ 1 МИН ПОСЛЕ ТЕМНОВОЙ РЕАКЦИИ

0,2

0,4

А

1840 1860 1880 1900 1920 1940 1960 1980 2000 2000 2050

Волновое число (см-1)

h

17 R = Me 18 R = Me

CH

NCH2CH=CH2

Me

C RMnOC

OC O

CH NCOR

CH CH2

Meh, - CO h, - CO

MnOCCO CH2

55

λmax = 509 nm λmax = 331 nm

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

5

17

18

25

Upon irradiation of allylcarbamate 6 in hexane, benzene or THF only olefinic chelate 19 is formed.

Under experimental condinions, 19 is a thermo- and photostable compound.

6,7

19 R = OCMe3, R' = H

h

7

21 R = Me, R' = H20 R = Me, R' = H

CH

NCH2CH=CH2

C R

MnOCOC O

CH2 NCOR

CH CH2

h, - COh, - CO

CH2

MnOCCO

2

В – coordination of Mn with carbamate group С - coordination of Mn with allylic group

Stereoisomer 19S Stereoisomer 19R

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.

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1854

1903

1927

1965

ABSORBANCE

1900 2000

Wavenumbers (cm-1)

7THF solution

2021

21 20

20 R=H is 6.08 kcal/mol more stable

7R=Me, R”=H

Photolysis of allylamide 7 in hexane gives only olefinic chelate 20. However both chelates 20 and 21 are the reaction products in benzene and

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.

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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 -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.

CONCLUSIONS: