Detection of the Singlet and Triplet MM 未未* States in Quadruply Bonded Dimetal Tetracarboxylates (M = Mo, W) by Time-Resolved Infrared Spectroscopy

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• 作者：Brian G. Alberding ; Malcolm H. Chisholm ; Terry L. Gustafson
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：January 2, 2012
• 年：2012
• 卷：51
• 期：1
• 页码：491-498
• 全文大小：394K
• 年卷期：v.51,no.1(January 2, 2012)
• ISSN：1520-510X

文摘

The compounds M₂(O₂C^tBu)₄ and M₂(O₂CC₆H₅)₄, where M = Mo or W, have been examined by femtosecond time-resolved IR (fs-TRIR) spectroscopy in tetrahydrofuran with excitation into the singlet metal-to-ligand charge-transfer (¹MLCT) band. In the region from 1500 to 1600 cm^鈥?, a long-lived excited state (>2 ns) has been detected for the compounds M₂(O₂C^tBu)₄ and Mo₂(O₂C鈥揅₆H₅)₄ with an IR absorption at 1540 cm^鈥? assignable to the asymmetric CO₂ stretch, 谓_as(CO₂), of the triplet metal鈥搈etal 未鈭捨?star (³MM 未未*) state. The fs-TRIR spectra of W₂(O₂C鈥揅₆H₅)₄ are notably different and are assigned to decay of the MLCT states. In ³MM 未未*, the removal of an electron from the 未 orbital reduces MM 未 to CO₂ 蟺* back-bonding and causes a shift of 谓_as(CO₂) to higher energy by 30鈥?0 cm^鈥?, depending on the metal. TRIR spectroscopy also provides evidence for M₂(O₂C^tBu)₄, where M = Mo or W, having MM 未未* S₁ states with 谓_as(CO₂) distinct from those of the ³MM 未未* states.