1 Russian Academy of Sciences A.N.Nesmeyanov Institute of Organoelement Compounds Laboratory 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 L = PR 3, P(OR) 3, SR 2, olefins, acetylenes and other n- and  - donors

4 colourless +CO in closed system Reverse dark reaction. Colored during some hours at С Decomposition

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). 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.

6 Initial carbamate С 5 H 5 Mn(СO) 3 CH 2 NHCOtBu 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 (R 1 = CH 3, R 2 = H) before and after 5 minute UV irradiation CD spectra of (R) and (S) enantiomers of compound 3 (R 1 = CH 3, R 2 = H) before and after UV-irradiation The spectrum after irradiation is not solvent- dependent (hexane, benzene, ethanol, THF). d-d-transition. Initial After irradiation

8 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 nm region. The semiconvertion time T 1/2 is about 3 min. REVERSE REACTION semiconvertion time T 1/2 is min. Upon irradiation with visible light nm the reaction accelerates. T 1/2 is about 10 min.

9 Wide range of compounds were also studied in order elucidate the nature of the dicarbonyl intermediate stabilization.  D C  CYMANTRENES WITH BIFUNCTIONAL SUBSTITUENTS

10 Irradiation in benzene solution of (СO) 3 MnCH 2 N(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. IR and UV-Vis spectra of complex A in benzene solution in the course of irradiation. А

11  E 0 = 9.1 kcal/mol CO calc. = 1862, 1917 cm -1 CO exp. = 1866, 1929 cm -1 (А)

12 IR spectra  f (B) in benzene solution in the course of irradiation R = Otert.Bu (B), Me (C)

13 Upon irradiation in benzene of (D) Mn(CO) 3 С 5 H 4 CH(CH 3 )N=CHPy the dicarbonyl chelate with coordination of imine nitrogen atom is formed. (D)(D)

14 Initial complex D- trans =1684 cm -1 Initial complex D-cis  О  =1683 cm -1 Coordination with pyridine nitrogen (СО)=1687 cm -1 Coordination at imine nitrogen (СО)=1647 cm -1  E = 4.5 kcal/mol Trans-structure is more stable Coordination at imine nitrogen is 3.1 kcal/mol more preferable.

15 Differential spectrum

16

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.

18 Structure 9 Pyridine complex Structure 10 π-allylic complex. DFT D3LYP/LanL2DZ calculation: 9 is 12.7 ккал/моль more stable than 10

19 Upon irradiation of 3 in hexane and benzene, the kinetically preferable carbamate complex 13 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

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

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 hours to more stable thermodynamically 12. Hence 11 и 12 form the photochromic pair

22 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

23 Initial compound 4. product (Mn coordination with allylic group). Mn coordination with carbamate group Substance  E, kcal/mol  Q, kcal/mol. Initial 4-- Product Product СО *)  E – relative energies of isomeric products  Q corresponds to the processes 4 → 16 + СО и 4 → 15 + СО.

24 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

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. 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.

26 7 THF solution R=H is 6.08 kcal/mol more stable 7 R=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 10 о С. 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 (λ max 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.

27 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: