Triplet – triplet absorption of d0 metal complexes was for the first time revealed and studied by means of pulse photolysis and electron-exchange (Dexter) resonant energy transfer energy transfer.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3539

Ivanov, V.L.

Loukova, G.V.

Melnichuk, E.E.

Melnikov, M.Ya.

Smirnov, V.A.

Vasiliev, V.V.

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 2 No 4, 04NAESP18(2pp) (2013)   2304-1862/2013/2(4)04NAESP18(2) 04NAESP18-1  2013 Sumy State University Two−photon Processes in Organometallic Molecules and Clusters:  T−T Absorption of Group IV Metal Complexes  G.V. Loukova1,*, V.V. Vasiliev1, V.L. Ivanov2, M.Ya. Melnikov2, V.A. Smirnov, E.E. Melnichuk3  1 Institute of Problems of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russia 2 Lomonosov Moscow State University, Department of Chemistry, Leninskiye Gory, 1, build. 3, 119991 Moscow, Russia  3 National Taras Shevchenko University of Kiev, Department of Physics, Vladimirskaya Str., 60, 01601 Kiev, Ukraine  (Received 10 June 2013; published online 02 September 2013)  Triplet – triplet absorption of d0 metal complexes was for the first time revealed and studied by means of pulse photolysis and electron-exchange (Dexter) resonant energy transfer energy transfer.   Keywords: Two-Photon Processes, Triplet – Triplet  Absorption, d0 Organometallic Complexes, Ligand-to-Metal Charge Transfer Excited State, Time-Resolved Methods, Flash Photolysis.   PACS numbers: 32.50.+d, 82.50.Pt                                                * gloukova@mail.ru   1. INTROUCTION  Triple states, based on organometallic compounds, are of special fundamental interest. Phosphorescence study is of importance for triplet state theory advance.  Early-transition metal metallocenes (-L)2MXn (n = 1–3) [1] have been a cornerstone in the development of modern coordination organometallic chemistry and catalysis and continue to be a focus of chemical and structural studies giving fresh insights into reactivity, structural preferences, and bonding requirements and even in medical chemistry.  Group IV bent metallo-cenes RCp2MX2 [Cp = η5 – C5H5, cyclopentadienyl; M = Ti, Zr, Hf; R – substit-uent(s) or bridging group(s)] have provided impetus for a new genera-tion of a large family of highly reactive organome-tallics, for years successful-ly used in the fields of ho-mogeneous and heterogeneous catalysis [2–3]. Rare ligand-to-metal charge-transfer (LMCT) excited states, based on d0-metallocenes of titanium group (Ti, Zr, Hf) [4], were revealed to be highly emissive (phosphores-cent) and highly long-lived [5–9]. We have obtained first group IV metal complex [bridged zirconocene, namely rac-С6H10(IndH4)2ZrCl2 (1)], having high phos-phorescence quantum yield (Φ up to 0.41) and emis-sive-state lifetime (τ ranging from 10–7 to 10–5 s. in dif-ferent aprotic organic media) in fluent solutions at room temperature. [9] In the present contribution, we report results of our on-gong study of LMCT excited states based on bridged zirconocene 1 and simpler re-lated unbrided zirconocene Cp2ZrCl2 dissolved in vari-ous organic solvents. In this work, triplet – triplet (T–T) absorption of d0 metal complexes was for the first time revealed and studied by means of pulse photolysis and T–T energy transfer.   2. EXPERIMENTAL  The samples prepared with the use of single crys-tals 1 were studied. Group 4 metallocene complexes are air and moisture sensitive. Therefore, all measure-ments and manipulations with these highly reactive molecules were carried out under strictly anaerobic and anhydrous conditions under prepurified inert (Ar or He) atmosphere in flame-dried glassware on a double-manifold high-vacuum line using standard Schlenk technique or on all-glass vacuum line fitted with high-vacuum Teflon stopcocks. All solvents applied were put through a special multiple purification procedure in-cluding vacuum distillation from the traces of impuri-ties, oxygen, moisture and also degassed through sev-eral freeze-pump-thaw cycles (purity was checked by monitoring the UV-visible absorption and luminescence at 77 K and RT).  Triplet − triplet absorption spectra of the target me-tallocene systems were obtained with the use of flash-photolysis technique. Steady-state absorption spectra were measured on a Shimadzu UV-2101 PC spectro-photometer. Steady-state emission spectra were rec-orded with a Perkin-Elmer LS-55 spectrofluorimeter. The photophysical measurements were performed in 1-cm quartz cells at 20 oC.  3. RESULTS AND DISCUSION   T–T absorption of d0 metal complexes can be repre-sented at Fig. 1 (where IC stands for the internal con-version and ISC is the intersystem crossing.). Respectively, T–T absorption of d0 metal complexes was studied with the use of representative complex rac-С6H10(IndH4)2ZrCl2 dissolved in methylcyclohexane (MCH) (the correspondent spectrum is shown on Fig. 1), toluene, t-butylmethyl ether (BME), CH2Cl2, CHCl3,  MClClM = Ti, Zr, Hf G.V. LOUKOVA, V.V. VASILIEV, V.L. IVANOV ET AL. PROC. NAP 2, 04NAESP18 (2013)   04NAESP18-2 CCl4 and also in THF and 2-methyltetrahydrofuran (MTHF). T–T absorption maxima at 20oC are located at ~540 nm (in MCH), ~545 nm (in toluene), and ~550 nm (in BME).     Fig. 1 – T–T absorption of d0 metal  At photolysis of the target zirconocene dissolved in chlorine-containing hydrocarbons, THF, and MTFH, a fast photochemical decomposition occurs via dissocia-tion of the sandwich moiety С6H10(IndH4)2Zr< and the photolysis products are accumulated not allowing pre-cise characterization for the T–T absorption of the complex. The rate of photolysis of the complex in chlo-rine-containing hydrocarbons increases in the se-quence: CH2Cl2 < CHCl3 < CCl4. In the similar way, pulse photolysis of Cp2ZrCl2 solutions was revealed to yield the fast photochemical decomposition already in toluene that does not permit quantitative estimate for T–T absorption of the simplest zirconocene representa-tive Cp2ZrCl2. 500 550 6000,000,030,060,09  ZrClCl , нмA  Fig. 2 – Spectrum of triplet – triplet absorption of bridged zirconocene 1, dissolved in methylcyclohexane, derived at room temperature. The structure of 1 is shown in the insert.   Notably, up-to-date triplet − triplet absorption spec-tra have been obtained for a remarkable number of organic species, however, at the same time, such spec-tra, being a power and promising tool for quantitative and qualitative molecular analysis, were reported for a very limited number of organometallic (even one or two-component) systems.  ACKNOWLEDGEMENTS  The authors gratefully acknowledge financial sup-port from the Presidium of Russian Academy of Scienc-es, the Division of Chemistry and Material Sciences of Russian Academy of Sciences, and the Russian Foun-dation for Basic Research (projects N 12-03-31130, 12-03-00984, and 12-03-33104).   REFERENCES  1. P.C. Wailes, R.S.P. Coutts, H. Weigold, Organometallic Chemistry of Titanium, Zirconium, and Hafnium (New York: Academic Press: 1974). 2. G. Wilkinson, F.G.A. Stone, E.W. Abel, Eds. Comprehen-sive Organometallic Chemistry (Oxford: Pergamon Press: 1982).  3. P. Reimann, Phys. Rep. 361, 57 (2002). 4. J.A. Gladysz, Ed. Chem. Rev. 100 (2000). 5. H.G. Alt, Ed. Coord. Chem. Rev., 250 (2006). 6. R.W. Harrigan, G.S. Hammound, H.B. Gray, J. Organ-omet. Chem. 81, 79 (1974). 7.  E. Vitz, C.H. Brubaker, Jr., J. Organomet. Chem. 84, C16 (1974). 8.  H. Alt, M.D. Rausch, J. Am. Chem. Soc. 96, 5936 (1974). 9. E. Vitz, P.J. Wagner, C.H. Brubaker, Jr., J. Organomet. Chem. 107, 301 (1976).  10. E. Samuel, H.G. Alt, D.C. Hrncir, M.D. Rausch, J. Orga-nomet. Chem. 113, 331 (1976).  11. (M.D. Rausch, W.H. Boon, H.G. Alt, J. Organomet. Chem. 141, 299 (1977).  12. J.C. Lee, C.H. Brubaker, Jr., Inorg. Chim. Acta 25, 181 (1977).  13. E. Samuel, P. Maillard, C. Giannotti, J. Organomet. Chem. 142, 289 (1977).  14. (M. Pankowski, E. Samuel, J. Organomet. Chem. 221, C21 (1981).  15. M.R.M. Bruce, A. Kenter, D.R. Tyler, J. Am. Chem. Soc. 106, 639 (1984).  16. M.R.M. Bruce, D.R. Tyler, Organometallics 4, 528 (1985). 17.  M.R.M. Bruce, A. Sciafani, D.R. Tyler, Inorg. Chem. 25, 2546 (1986). 18. G.V. Loukova, in Organometallic Compounds: Prepara-tion, Structure and Properties (Ed. H. F. Chin) Ch. 4, 159–196 (New York: Nova Science Publishers, 2010). 19. G.V. Loukova, V.A. Smirnov, Chem. Phys. Lett. 329, 437 (2000).  20. G.V. Loukova, V.A. Smirnov, Russ. Chem. Bull., Int. Ed. 50, 329 (2001). 21. V.W.W. Yam, G.Z. Qi, K.K. Cheung, Organometallics 17, 5448 (1998).  22. V.W.W. Yam, G.Z. Qi, K.K. Cheung,  J. Chem. Soc., Dalton Trans. 1819 (1998).  23. V.W.W. Yam, G.Z. Qi, K.K. Cheung,  J. Organomet. Chem. 548, 289 (1997). 24. G.V. Loukova, S.E. Starodubova, V.A. Smirnov, J. Phys. Chem. A. 111, 10928 (2007).  25. G.V. Loukova, V.A. Smirnov, S.E. Starodubova, Russ. J. Coord. Chem. 31, 530 (2005).  26. G.V. Loukova, V.A. Smirnov, S.E. Starodubova, Doklady Phys. Chem. 404, 173 (2005). 27. G.V. Loukova, W. Huhn, V.P. Vasiliev, V.A. Smirnov, J. Phys. Chem. A. 111, 4117 (2007).  28. G.V. Loukova, V.P. Vasiliev, V.A. Smirnov, W. Huhn, Doklady Phys. Chem. 413, 66 (2007). 

Two−photon Processes in Organometallic Molecules and Clusters: T−T Absorption of Group IV Metal Complexes

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 2 No 4, 04NAESP18(2pp) (2013) 
 
 
2304-1862/2013/2(4)04NAESP18(2) 04NAESP18-1  2013 Sumy State University 
Two−photon Processes in Organometallic Molecules and Clusters:  
T−T Absorption of Group IV Metal Complexes 
 
G.V. Loukova1,*, V.V. Vasiliev1, V.L. Ivanov2, M.Ya. Melnikov2, V.A. Smirnov, E.E. Melnichuk3 
 
1 Institute of Problems of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, 
Russia 
2 Lomonosov Moscow State University, Department of Chemistry, Leninskiye Gory, 1, build. 3, 119991 Moscow, 
Russia  
3 National Taras Shevchenko University of Kiev, Department of Physics, Vladimirskaya Str., 60, 01601 Kiev, 
Ukraine 
 
(Received 10 June 2013; published online 02 September 2013) 
 
Triplet – triplet absorption of d0 metal complexes was for the first time revealed and studied by means 
of pulse photolysis and electron-exchange (Dexter) resonant energy transfer energy transfer.  
 
Keywords: Two-Photon Processes, Triplet – Triplet  Absorption, d0 Organometallic Complexes, Ligand-to-
Metal Charge Transfer Excited State, Time-Resolved Methods, Flash Photolysis. 
 
 PACS numbers: 32.50.+d, 82.50.Pt 
                                               
* gloukova@mail.ru 
 
 
1. INTROUCTION 
 
Triple states, based on organometallic compounds, 
are of special fundamental interest. Phosphorescence 
study is of importance for triplet state theory advance.  
Early-transition metal metallocenes (-L)2MXn (n = 
1–3) [1] have been a cornerstone in the development of 
modern coordination organometallic chemistry and 
catalysis and continue to be a focus of chemical and 
structural studies giving fresh insights into reactivity, 
structural preferences, and bonding requirements and 
even in medical chemistry.  
Group IV bent metallo-
cenes RCp2MX2 [Cp = η5 –
 C5H5, cyclopentadienyl; 
M = Ti, Zr, Hf; R – substit-
uent(s) or bridging 
group(s)] have provided 
impetus for a new genera-
tion of a large family of 
highly reactive organome-
tallics, for years successful-
ly used in the fields of ho-
mogeneous and heterogeneous catalysis [2–3]. Rare 
ligand-to-metal charge-transfer (LMCT) excited states, 
based on d0-metallocenes of titanium group (Ti, Zr, Hf) 
[4], were revealed to be highly emissive (phosphores-
cent) and highly long-lived [5–9]. We have obtained 
first group IV metal complex [bridged zirconocene, 
namely rac-С6H10(IndH4)2ZrCl2 (1)], having high phos-
phorescence quantum yield (Φ up to 0.41) and emis-
sive-state lifetime (τ ranging from 10–7 to 10–5 s. in dif-
ferent aprotic organic media) in fluent solutions at 
room temperature. [9] In the present contribution, we 
report results of our on-gong study of LMCT excited 
states based on bridged zirconocene 1 and simpler re-
lated unbrided zirconocene Cp2ZrCl2 dissolved in vari-
ous organic solvents. In this work, triplet – triplet (T–
T) absorption of d0 metal complexes was for the first 
time revealed and studied by means of pulse photolysis 
and T–T energy transfer.  
 
2. EXPERIMENTAL 
 
The samples prepared with the use of single crys-
tals 1 were studied. Group 4 metallocene complexes are 
air and moisture sensitive. Therefore, all measure-
ments and manipulations with these highly reactive 
molecules were carried out under strictly anaerobic and 
anhydrous conditions under prepurified inert (Ar or 
He) atmosphere in flame-dried glassware on a double-
manifold high-vacuum line using standard Schlenk 
technique or on all-glass vacuum line fitted with high-
vacuum Teflon stopcocks. All solvents applied were put 
through a special multiple purification procedure in-
cluding vacuum distillation from the traces of impuri-
ties, oxygen, moisture and also degassed through sev-
eral freeze-pump-thaw cycles (purity was checked by 
monitoring the UV-visible absorption and luminescence 
at 77 K and RT).  
Triplet − triplet absorption spectra of the target me-
tallocene systems were obtained with the use of flash-
photolysis technique. Steady-state absorption spectra 
were measured on a Shimadzu UV-2101 PC spectro-
photometer. Steady-state emission spectra were rec-
orded with a Perkin-Elmer LS-55 spectrofluorimeter. 
The photophysical measurements were performed in 1-
cm quartz cells at 20 oC. 
 
3. RESULTS AND DISCUSION  
 
T–T absorption of d0 metal complexes can be repre-
sented at Fig. 1 (where IC stands for the internal con-
version and ISC is the intersystem crossing.). 
Respectively, T–T absorption of d0 metal complexes 
was studied with the use of representative complex rac-
С6H10(IndH4)2ZrCl2 dissolved in methylcyclohexane 
(MCH) (the correspondent spectrum is shown on Fig. 
1), toluene, t-butylmethyl ether (BME), CH2Cl2, CHCl3, 
 
M
Cl
Cl
M = Ti, Zr, Hf
 G.V. LOUKOVA, V.V. VASILIEV, V.L. IVANOV ET AL. PROC. NAP 2, 04NAESP18 (2013) 
 
 
04NAESP18-2 
CCl4 and also in THF and 2-methyltetrahydrofuran 
(MTHF). T–T absorption maxima at 20oC are located at 
~540 nm (in MCH), ~545 nm (in toluene), and ~550 nm 
(in BME).  
 
 
 
Fig. 1 – T–T absorption of d0 metal 
 
At photolysis of the target zirconocene dissolved in 
chlorine-containing hydrocarbons, THF, and MTFH, a 
fast photochemical decomposition occurs via dissocia-
tion of the sandwich moiety С6H10(IndH4)2Zr< and the 
photolysis products are accumulated not allowing pre-
cise characterization for the T–T absorption of the 
complex. The rate of photolysis of the complex in chlo-
rine-containing hydrocarbons increases in the se-
quence: CH2Cl2 < CHCl3 < CCl4. In the similar way, 
pulse photolysis of Cp2ZrCl2 solutions was revealed to 
yield the fast photochemical decomposition already in 
toluene that does not permit quantitative estimate for 
T–T absorption of the simplest zirconocene representa-
tive Cp2ZrCl2. 
500 550 600
0,00
0,03
0,06
0,09
 
 
Zr
Cl
Cl
 
, нм
A
 
 
Fig. 2 – Spectrum of triplet – triplet absorption of bridged 
zirconocene 1, dissolved in methylcyclohexane, derived at 
room temperature. The structure of 1 is shown in the insert.  
 
Notably, up-to-date triplet − triplet absorption spec-
tra have been obtained for a remarkable number of 
organic species, however, at the same time, such spec-
tra, being a power and promising tool for quantitative 
and qualitative molecular analysis, were reported for a 
very limited number of organometallic (even one or 
two-component) systems. 
 
ACKNOWLEDGEMENTS 
 
The authors gratefully acknowledge financial sup-
port from the Presidium of Russian Academy of Scienc-
es, the Division of Chemistry and Material Sciences of 
Russian Academy of Sciences, and the Russian Foun-
dation for Basic Research (projects N 12-03-31130, 12-
03-00984, and 12-03-33104). 
 
 
REFERENCES 
 
1. P.C. Wailes, R.S.P. Coutts, H. Weigold, Organometallic 
Chemistry of Titanium, Zirconium, and Hafnium (New 
York: Academic Press: 1974). 
2. G. Wilkinson, F.G.A. Stone, E.W. Abel, Eds. Comprehen-
sive Organometallic Chemistry (Oxford: Pergamon Press: 
1982).  
3. P. Reimann, Phys. Rep. 361, 57 (2002). 
4. J.A. Gladysz, Ed. Chem. Rev. 100 (2000). 
5. H.G. Alt, Ed. Coord. Chem. Rev., 250 (2006). 
6. R.W. Harrigan, G.S. Hammound, H.B. Gray, J. Organ-
omet. Chem. 81, 79 (1974). 
7.  E. Vitz, C.H. Brubaker, Jr., J. Organomet. Chem. 84, C16 
(1974). 
8.  H. Alt, M.D. Rausch, J. Am. Chem. Soc. 96, 5936 (1974). 
9. E. Vitz, P.J. Wagner, C.H. Brubaker, Jr., J. Organomet. 
Chem. 107, 301 (1976).  
10. E. Samuel, H.G. Alt, D.C. Hrncir, M.D. Rausch, J. Orga-
nomet. Chem. 113, 331 (1976).  
11. (M.D. Rausch, W.H. Boon, H.G. Alt, J. Organomet. Chem. 
141, 299 (1977).  
12. J.C. Lee, C.H. Brubaker, Jr., Inorg. Chim. Acta 25, 181 
(1977).  
13. E. Samuel, P. Maillard, C. Giannotti, J. Organomet. 
Chem. 142, 289 (1977).  
14. (M. Pankowski, E. Samuel, J. Organomet. Chem. 221, C21 
(1981).  
15. M.R.M. Bruce, A. Kenter, D.R. Tyler, J. Am. Chem. Soc. 
106, 639 (1984).  
16. M.R.M. Bruce, D.R. Tyler, Organometallics 4, 528 (1985). 
17.  M.R.M. Bruce, A. Sciafani, D.R. Tyler, Inorg. Chem. 25, 
2546 (1986). 
18. G.V. Loukova, in Organometallic Compounds: Prepara-
tion, Structure and Properties (Ed. H. F. Chin) Ch. 4, 159–
196 (New York: Nova Science Publishers, 2010). 
19. G.V. Loukova, V.A. Smirnov, Chem. Phys. Lett. 329, 437 
(2000).  
20. G.V. Loukova, V.A. Smirnov, Russ. Chem. Bull., Int. Ed. 
50, 329 (2001). 
21. V.W.W. Yam, G.Z. Qi, K.K. Cheung, Organometallics 17, 
5448 (1998).  
22. V.W.W. Yam, G.Z. Qi, K.K. Cheung,  J. Chem. Soc., Dalton 
Trans. 1819 (1998).  
23. V.W.W. Yam, G.Z. Qi, K.K. Cheung,  J. Organomet. Chem. 
548, 289 (1997). 
24. G.V. Loukova, S.E. Starodubova, V.A. Smirnov, J. Phys. 
Chem. A. 111, 10928 (2007).  
25. G.V. Loukova, V.A. Smirnov, S.E. Starodubova, Russ. J. 
Coord. Chem. 31, 530 (2005).  
26. G.V. Loukova, V.A. Smirnov, S.E. Starodubova, Doklady 
Phys. Chem. 404, 173 (2005). 
27. G.V. Loukova, W. Huhn, V.P. Vasiliev, V.A. Smirnov, J. 
Phys. Chem. A. 111, 4117 (2007).  
28. G.V. Loukova, V.P. Vasiliev, V.A. Smirnov, W. Huhn, 
Doklady Phys. Chem. 413, 66 (2007). 


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Two−photon Processes in Organometallic Molecules and Clusters: T−T Absorption of Group IV Metal Complexes

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