Mixed-Metal Cluster Chemistry. 30.1 Syntheses and Optical Limiting Properties of Cluster-Containing Oligo- and Polyurethanes
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- 作者：Michael D. Randles ; Nigel T. Lucas ; Marie P. Cifuentes ; Mark G. Humphrey ; Matthew K. Smith ; Anthony C. Willis ; Marek Samoc
- 刊名：Macromolecules
- 出版年：2007
- 出版时间：October 30, 2007
- 年：2007
- 卷：40
- 期：22
- 页码：7807 - 7818
- 全文大小：356K
- 年卷期：v.40,no.22(October 30, 2007)
- ISSN：1520-5835
文摘
Molybdenum-iridium clusters Mo2Ir2{4-2-C2[(CH2)6OH]2}(-CO)4(CO)4(-C5H4R)2 [R = H (5),Me (6), (CH2)9O(THP) (7); THP = tetrahydropyranyl] are formed from reaction of Mo2Ir2(-CO)3(CO)7(-C5H4R)2with the alkyne HO(CH2)6C2(CH2)6OH. Reaction of 6 and 7 with the diisocyanate OCN(CH2)4NCO affordsoligourethanes [-O(CH2)6(4-2-C2){Mo2Ir2(-CO)4(CO)4(-C5H4R)2}(CH2)6OC(O)NH(CH2)4NHC(O)-]n [R =Me (12), (CH2)9O(THP) (13)], with transition metal clusters in the backbone, the extent of polymerization beingascertained by size exclusion chromatography and 1H NMR spectroscopy. Characterization of the cluster-containingoligo- and polyurethanes was aided by 1H NMR and IR spectral comparison with model cluster diurethanesMo2Ir2{4-2-C2[(CH2)6OC(O)NH(CH2)3Me]2}(-CO)4(CO)4(-C5H4R)2 [R = H (8), Me (9), (CH2)9O(THP) (11)],prepared from reaction between the cluster diols 5, 6, and 7 and the isocyanate Me(CH2)3NCO. The diol cluster5 and cluster diurethane 8 have been characterized by single-crystal X-ray diffraction studies. Removal of theTHP groups in 13 gives [-O(CH2)6(4-2-C2){Mo2Ir2(-CO)4(CO)4(-C5H4(CH2)9OH)2}(CH2)6OC(O)NH(CH2)4NHC(O)-]n (14), which has been cross-linked on reaction with OCN(CH2)4NCO. The cluster content of thepolyurethanes can be diluted; polymerization of 1:19 6:1,6-hexanediol and OCN(CH2)4NCO affords copolymer[-O(CH2)6(4-2-C2){Mo2Ir2(-CO)4(CO)4(-C5H4Me)2}(CH2)6OC(O)NH(CH2)4NHC(O){O(CH2)6OC(O)NH(CH2)4NHC(O)}m-]n (16). The optical limiting properties of these dimolybdenum-diiridium clusters and cluster-containing polymers, and related molybdenum-triiridium clusters and tungsten-containing homologues, have beenassessed by open-aperture Z-scan studies at 527 nm employing ns pulses. Optical limiting merit increases uponincreasing group 6 metal content, and replacing the 4d metal molybdenum with the 5d metal tungsten. Someinsight into the mechanism by which these clusters function as optical limiters has been gleaned fromcomplementary pump-probe studies, with their behavior consistent with a fast nonlinear absorption processfollowed by reverse saturable absorption involving metastable excited states of greater than nanosecond lifetime.