Sanjukta Ghose

Nonlinear optical properties of mixed Mo/Fe, mixed chalcogen clusters Cp2Mo2Fe2STe(CO)7 and Cp2Mo2Fe2(μ3-S)(μ3-Te)(μ2-SPh)(μ3-H)(CO)5

Studies of the third order optical nonlinearity of the mixed-metal, mixed chalcogen clusters Cp 2 Mo 2 Fe 2 STe(CO) 7 and Cp 2 Mo 2 Fe 2 (μ3-S)(μ3-Te)(μ2-SPh)(μ3-H)(CO) 5 using 532 nm, 6 ns laser pulses are reported. The second compound is the first example in literature of a mixed Fe/Mo mixed chalcogen complex containing a bridging thiolate group. The effective nonlinear absorption coefficient and nonlinear index intensity coefficient of these compounds are measured by the Z-scan technique, from which the corresponding cubic hyperpolarizabilities are evaluated. The obtained values indicate a high nonlinearity comparable to some of the best values reported previously for cluster compounds. Both compounds show strong optical limiting. In addition, their photostability is found to be much superior to many of the previously reported highly nonlinear clusters.

SYNTHESIS, CHARACTERISATION AND NONLINEAR OPTICAL PROPERTIES OF TETRAHEDRAL CLUSTERS CP2MO2ME(CO)7, (M = FE, RU, OS; E = S, SE)

Abstract A set of new chalcogen-bridged mixed metal clusters, Cp 2 Mo 2 M( μ 3 -E)(CO) 7 , (M=Fe, Ru, Os; E=S, Se) have been synthesised and characterised by IR and NMR spectroscopy, and structures of Cp 2 Mo 2 Ru( μ 3 -Se)(CO) 7 and Cp 2 Mo 2 Os( μ 3 -Se)(CO) 7 have been established by single crystal X-ray diffraction methods. The nonlinear optical properties of these clusters were investigated through the Z-scan technique, using 35 ps laser pulses at 532 nm. We report large refractive third order nonlinearity for these clusters indicating their promise for optical limiting applications.

Thermolysis of Fe3(CO)9(μ3-Se)(μ3-E) (E = S, Te) with Cp2Mo2(CO)6 and formation of new mixed-chalcogenide, mixed Fe-Mo carbonyl clusters. Crystal structures of Cp2Mo2Fe2(CO)6(μ3-Se)2(μ4-Te), Cp2Mo2Fe2(CO)7(μ3-Se)(μ3-Te) and Cp2Mo2Fe2(CO)6(μ3-S)(μ3-Se)(μ4-Se)

Abstract The thermolytic reaction of Fe3(CO)9(μ3-Se)(μ3-Te) with Cp2Mo2(CO)6 in benzene yielded the new mixed-metal, mixed trichalcogenide clusters Cp2Mo2Fe2(CO)6(μ3-Se)(μ3-Te)(μ4-Te) (2a), Cp2Mo2Fe2(CO)6(μ3-Te)2(μ4-Se) (2b) and Cp2Mo2Fe2(CO)6(μ3-Se)2(μ4-Te) (3a), Cp2Mo2Fe2(CO)6(μ3-Se)(μ3-Te)(μ4-Se) (3b) as well as the dichalcogenide cluster Cp2Mo2Fe2(CO)7(μ3-Se)(μ3-Te) (8). Similarly, the thermolysis of Fe3(CO)9(μ3-S)(μ3-Se) with Cp2Mo2(CO)6 in benzene afforded the new mixed-metal, mixed trichalcogenide clusters Cp2Mo2Fe2(CO)6(μ3-S)2(μ4-Se) (10), Cp2Mo2Fe2(CO)6(μ3-S)(μ3-Se)(μ4-Se) (11) and the dichalcogenide cluster Cp2Mo2Fe2(CO)7(μ3-S)(μ3-Se) (13). In the case of 10 and 11, formation of isomers containing the sulphido in the μ4-site was not observed. Compounds 2a and 2b could also be obtained when Cp2Mo2Fe2(CO)6(μ3-Te)2 was refluxed with selenium powder in benzene. Similarly, refluxing of benzene solutions containing selenium powder and Cp2Mo2Fe2(CO)6(μ3-Se)(μ3-Te) formed 3a and 3b, and sulphur powder with Cp2Mo2Fe2(CO)6(μ3-S)(μ3-Se) or Cp2Mo2Fe2(CO)6(μ3-Se)2 yielded the compounds 10 and 11 respectively. The new clusters have been characterised by IR and by 1H, 13C, 77Se and 125Te NMR spectroscopy. Clusters 3a, 8 and 11 have also been structurally characterised by single-crystal X-ray diffraction methods.

Synthesis and characterisation of [Fe2M3(μ4-E)(μ3-E′)(CO)17] and [Os3(μ3-E)(μ3-E′)(CO)9] (M=Os or Ru; E=S, Se, Te; E′=Se, Te)

Abstract A set of new chalcogen-bridged mixed metal clusters [Fe2Os3(μ4-E)(μ3-E′)(CO)17] (2, EE′=SeTe; 3, EE′=STe; 4, EE′=Se2; 5, EE′=SSe) and [Fe2Ru3(μ4-E)(μ3-E′)(CO)17] (12, EE′=SeTe; 13, EE′=STe; 14, EE′=Se2; 15, EE′=SSe) has been synthesised by facile methods. Thermolysis or photolysis of compounds 2, 3 and 5 afforded the new triosmium mixed chalcogenide clusters [Os3(μ3-E)(μ3-E′)(CO)9] (7, EE′=SeTe; 8, EE′=STe; 10, EE′=SSe). All new compounds were characterised by IR and 1H-, 77Se- and 125Te-NMR spectroscopy. Clusters 8, 9 and 12 were structurally characterised by single crystal X-ray diffraction methods.

Synthesis, optical nonlinearity and crystal structure of a novel mixed-chalcogen, thiolato-bridged complex [(η5-C5H5)2Mo2(μ-S)(μ-Te)(μ-SPh)2]

Abstract A novel dimolybdenum complex in which the metal atoms are bridged by two different chalcogens and two thiolato ligands has been synthesised and structurally characterised. This complex shows a large third-order optical nonlinearity as measured by degenerate four-wave mixing with picosecond excitation at 532 nm. A hyperpolarisability (γ) of 1.2×10−30 esu has been obtained. The structure of the complex was established by the single-crystal X-ray diffraction method. It consists of a Mo–Mo unit, which is bridged by one S, one Te and two (SPh) groups. Each Mo atom also has a (η5-C5H5) group attached to it.

Synthesis and characterisation of cis and trans isomers of the mixed chalcogen clusters Cp2Mo2Fe2(CO)8(μ3-S)(μ3-Se) and Cp2Mo2Fe2(CO)8(μ3-S)(μ3-Te)

The reaction of Fe 2 (CO) 6 (μ-SSe) and Cp 2 Mo 2 (CO) 4 in benzene at room temperature for 2 h, yielded the new isomeric mixed-metal, mixed-dichalcogenide clusters trans -Cp 2 Mo 2 Fe 2 (CO) 8 (μ 3 -S)(μ 3 -Se) ( 1 ) and cis -Cp 2 Mo 2 Fe 2 (CO) 8 (μ 3 -S)(μ 3 -Se) ( 4 ). The new mixed-metal clusters 1 and 4 could also be obtained when Fe 3 (CO) 9 (μ 3 -S)(μ 3 -Se) and Cp 2 Mo 2 (CO) 6 were heated at 65°C in benzene for 36 h. Similarly, the room-temperature reaction of Fe 2 (CO) 6 (μ-STe) with Cp 2 Mo 2 (CO) 4 in benzene for 2 h and the thermolytic reaction of Fe 3 (CO) 9 (μ 3 -S)(μ 3 -Te) with Cp 2 Mo 2 (CO) 6 in benzene for 36 h afforded the new isomeric clusters trans -Cp 2 Mo 2 Fe 2 (CO) 8 (μ 3 -S)(μ 3 -Te) ( 9 ) and cis -Cp 2 Mo 2 Fe 2 (CO) 8 (μ 3 -S)(μ 3 -Te) ( 11 ). The new clusters have been characterised by IR and by 1 H-, 77 Se-, 125 Te-NMR spectroscopy. Clusters 1 and 4 have also been structurally characterised by single-crystal X-ray diffraction methods.

Synthesis and structural characterisation of a mixed Mo/Fe, mixed chalcogen, PhS-bridged cluster

Abstract Thermolytic reaction of Cp2Mo2Fe2STe(CO)7 and C6H5SH in benzene afforded two isomers of the new compound Cp2Mo2Fe2(μ3-S)(μ3-Te)(μ2-SPh)(μ3-H)(CO)5 in 23 and 21% yields. They were characterised by IR, 1H- and 125Te-NMR spectroscopy. The structure of one isomer was established by single crystal X-ray diffraction method. The structure consists of a Mo2Fe2 tetrahedron with μ3-S and μ3-Te face capping ligands. The Mo–Mo bond is bridged by a SPh group and one MoFe2 face is bridged by a μ-H group. Each Fe atom has two terminal carbonyls and one CO group bridges the Fe–Fe bond.

Synthesis and structural characterisation of trans-Cp2Mo2O2(μ-O)(μ-Te) and cis-Cp2Mo2O2(μ-O)(μ-S)

The two compounds, trans -Cp 2 Mo 2 O 2 (μ-O)(μ-Te) and cis -Cp 2 Mo 2 O 2 (μ-O)(μ-S), were isolated in 31% and 36% yields respectively, when a benzene solution of Cp 2 Mo 2 Fe 2 (CO) 7 ( μ 3 -S)( μ 3 -Te) was refluxed for 3 h in the presence of air. Characterisation was carried out by IR. 1 H NMR and 125 Te NMR spectroscopy. The structures, established by single crystal X-ray diffraction analysis, consist of an oxo-bridged dimolybdenum unit containing a μ 2 -Te atom in one case and a μ 2 -S atom in the other. Also attached to each Mo atom are a Cp ligand and a terminally bonded oxo group.

Synthesis and structural characterisation of a new μ2-Te bridged complex of molybdenum with oxo and imido ligands

Reflux of a benzene solution of Cp 2 Mo 2 Fe 2 (CO) 7 Te 2 and PhN 3 in the presence of air afforded the new compound Cp 2 Mo 2 O 2 (μ-Te)(μ-NC 6 H 5 ) in 33% yield. It was characterised by IR and 1 H and 125 Te NMR. spectroscopy. Crystallographic analysis established its structure. The structure can be described as consisting of a CpMo-MoCp unit, bridged by a μ-Te atom and an imido ligand. Also bonded to each Mo atom is a terminally bonded oxo group.

Characterization of local soils and study the migration behavior of radionuclide from disposal site of LILW

Migration behavior of radionuclide is one of the most important factors to be considered for the long-term safety assessment of a radioactive waste disposal facility in a wet geological formation. In the present study, laboratory based column experiments have been carried out to assess the radionuclide migration behavior of ¹³⁷Cs and ⁶⁰Co and to evaluate the retardation factor through a clay soil layers using gamma spectrometry. Investigation was performed for a range of particle sizes and fixed column lengths to determine an appropriate value of migration rate of ¹³⁷Cs and ⁶⁰Co. The distribution pattern of particle size in soil samples were measured by sieved method. Two different particle sizes (≤ 90 μm and mixed size) were used in the column experiments. The migration rate in the clay type soil layer of particle size ≤ 90 μm was found by the order of ⁶⁰Co > ¹³⁷Cs. The maximum migration length of ⁶⁰Co in the soil layer was found to be 0-25 cm, however in the case of ¹³⁷Cs it was found at a maximum length of 0-10 cm. The distribution coefficient of ⁶⁰Co was found nearly same as that of ¹³⁷Cs. The retardation factor was found to be 1.79 and 1.94 for ⁶⁰Co and ¹³⁷Cs, respectively. The experimental breakthrough from this study indicates that the amount of radioactive cesium and cobalt released depends upon the composition of the soils.