Syntheses and Spectroscopic, Structural, Electrochemical, Spectroelectrochemical, and Theoretical Studies of Osmium(II) Mono- and Bis-Alkynyl Complexes

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• 作者：Patrick J. West ; Marie P. Cifuentes ; Torsten Schwich ; Michael D. Randles ; Joseph P. Morrall ; Erandi Kulasekera ; Simon Petrie ; Robert Stranger ; Mark G. Humphrey
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：October 15, 2012
• 年：2012
• 卷：51
• 期：20
• 页码：10495-10502
• 全文大小：385K
• 年卷期：v.51,no.20(October 15, 2012)
• ISSN：1520-510X

文摘

The syntheses of trans-[Os(C鈮-4-C₆H₄X)Cl(dppe)₂] [X = Br (3), I (4)], trans-[Os(C鈮-4-C₆H₄X)(NH₃)(dppe)₂](PF₆) [X = H (5(PF₆)), I (6(PF₆))], and trans-[Os(C鈮-4-C₆H₄X)(C鈮-4-C₆H₄Y)(dppe)₂] [X = Y = H (7), X = I, Y = C鈮SiPrⁱ₃ (8)] are reported, together with improved syntheses of cis-[OsCl₂(dppe)₂] (cis-1), trans-[Os(C鈮Ph)Cl(dppe)₂] (2), and trans-[Ru(C鈮-4-C₆H₄I)(NH₃)(dppe)₂](PF₆) (9(PF₆)) (the last-mentioned direct from trans-[Ru(C鈮-4-C₆H₄I)Cl(dppe)₂]), and single-crystal X-ray structural studies of 2鈥?b>4, 5(PF₆), 6(PF₆), and 7. Ammine complexes 5(PF₆)/6(PF₆) are shown to afford a facile route to both symmetrical (7) and unsymmetrical (8) osmium bis(alkynyl) complexes. A combination of cyclic voltammetry, UV鈥搗is鈥揘IR spectroelectrochemistry, and time-dependent density functional theory (TD-DFT) has permitted identification and assignment of the intense transitions in both the resting state and the oxidized forms of these complexes. Cyclic voltammetric data show fully reversible oxidation processes at 0.32鈥?.42 V (3, 4, 7, 8) (with respect to ferrocene/ferrocenium 0.56 V), assigned to the (formal) Os^II/III couple. The osmium(III) complex (di)cations 5²⁺ and 7⁺ were obtained by in situ oxidation of 5⁺ and 7 using an optically transparent thin-layer electrochemical (OTTLE) cell. The UV鈥搗is鈥揘IR optical spectra of 5²⁺ and 7⁺ reveal low-energy bands in the near IR region, in contrast to 5⁺ and 7 which are optically transparent at frequencies below 22鈥?00 cm^鈥?. TD-DFT calculations on trans-1, 2, 5⁺, and 7 and their oxidized forms suggest that the lowest-energy transitions are chloro-to-metal charge transfer (trans-1), chloro-to-phenylethynyl charge transfer (2), and metal-to-phenylethynyl charge transfer (5⁺, 7) in the resting state and chloro-to-metal charge transfer (trans-1⁺), phosphorus-to-metal charge transfer (5²⁺), alkynyl-to-metal charge transfer (7⁺), or phenylalkynyl-centered 蟺 鈫?蟺* (2⁺) following oxidation. The presence of intense CT bands in the resting states and oxidized states and their significantly different nature across the two states, coupled to their strong charge displacement suggest that these species have considerable potential as electrochemically switchable nonlinear optical materials, while the facile unsymmetrical bis(alkynyl)osmium(II) construction suggests potential in construction of multistate heterometallic modular assemblies.