Eleni G. A. Notaras

Mixed-metal cluster chemistry. Part 17. Syntheses of WIr 3 (CO) 11 (n-C 5 H 4 Me) and its reactivity towards diphenylacetylene

Abstract The X-ray structurally confirmed tetrahedral mixed-metal cluster WIr3(CO)11(η-C5H4Me) (1) is prepared in 8% yield from reactions between [W(CO)3(η-C5H4Me)]− and IrCl(CO)2(p-toluidine) under an Ar atmosphere, and in 46% yield from reaction between WH(CO)3(η-C5H4Me) and IrCl(CO)2(p-toluidine) under a CO atmosphere; both reactions also afford tetrahedral W2Ir2(CO)10(η-C5H4Me)2 (2). Cluster 1 reacts with diphenylacetylene to afford three products, namely tetrahedral WIr3(μ3-η2-PhC2Ph)2(CO)7(η-C5H4Me) (3), butterfly WIr3{μ-η4-C(Ph)C(Ph)C(Ph)C(Ph)}(CO)5(η-C5H4Me) (4) and the binuclear product Ir2{μ-η4-C(Ph)C(Ph)C(Ph)C(Ph)}(CO)5 (5); X-ray studies of 4 and 5 reveal a common (iridacyclopentadienyl)iridium structural motif.

Mixed-metal cluster chemistry. Part 18. Synthesis and crystal structure of W 3 Ir 3 (u 4 -η 2 -CO)(u-CO)(CO) 10 (η-C 5 H 4 Me) 3

Abstract Heating a mixture of W 2 Ir 2 (CO) 10 (η-C 5 H 4 Me) 2 and 1,2-( E )-bis{4′-(oct-1′′-ynyl)phenyl}ethene in refluxing CH 2 Cl 2 affords a complex mixture from which W 3 Ir 3 (μ 4 -η 2 -CO)(μ-CO)(CO) 10 (η-C 5 H 4 Me) 3 can be separated in low yield. The crystallographically characterized title cluster is the first hexametallic Group 6–Group 9 mixed-metal cluster, possesses an unusual edge-bridged trigonal bipyramidal core geometry, and has a μ 4 -η 2 -CO ligand which has the longest carbonyl CO bond thus far.

Syntheses, Characterization and Optical Limiting Properties of Heterometallic Cluster-containing Polymers

Transition metal carbonyl clusters incorporating group 6 (molybdenum, tungsten) and iridium atoms in a tetrahedral or butterfly-shaped four-atom cluster core, together with carbonyl, cyclopentadienyl and alkyne ligands, have been synthesized and incorporated into oligourethanes, and their optical limiting properties assessed by open-aperture Z-scan (ns pulses, 523 nm) and time-resolved pump-probe studies (ps pulses, 527 nm). The Z-scan studies reveal that the tetrahedral [M2Ir2] cluster cores (M = Mo, W) displayed a greater effective nonlinear absorption coefficent β2 than the [MoIr3] cores; the tungsten example, W2Ir2(CO)10(η-C5H5)2, exhibited the highest response. Substitution at the cyclopentadienyl group (including incorporation into a polymer backbone) had little effect on the response measured. A time-resolved investigation of the alkyne-adduct Mo2Ir2(μ4-η2-MeC2Ph)(CO)8(η-C5H4Me)2 using picosecond pulses at 527 nm reveals optical-power-limiting behaviour that results from electronic processes [specifically, a fast nonlinear absorption process followed by reverse saturable absorption involving long-lived (>1000 ps) metastable excited states].

Two-photon absorption, absorption saturation, and dispersion of the real and imaginary parts of the third-order optical nonlinearity in organometallic dendrimers

We have been studying third-order NLO properties of ruthenium-containing organometallic dendrimers. These molecules offer large hyperpolarizabilities and the possibility to control both the refractive and absorptive parts of the nonlinear response by electrochemical switching of the oxidation state of the ruthenium centres. Time-resolved studies indicate that it is possible to switch the molecules between the form in which they are two-photon absorbers and the state where they are fast (~ 1 picosecond time scale) saturable absorbers. Measurements of the dispersion of third-order nonlinearity have been made by the Z-scan technique on a nitro decorated dendrimer. They indicate that competition between two-photon absorption and absorption saturation is present in some wavelength ranges. The dispersion of both the real and imaginary parts of the cubic polarizability could be modelled by considering leading terms of the dispersion relation.