Syntheses,Spectroscopic, Electrochemical,and Third‐Order Nonlinear Optical Studies of a Hybrid Tris{ruthenium(alkynyl)/(2‐phenylpyridine)}iridium Complex |
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| Authors: | Huajian Zhao Dr Peter V Simpson Adam Barlow Dr Graeme J Moxey Dr Mahbod Morshedi Nivya Roy Prof Reji Philip Prof Chi Zhang Dr Marie P Cifuentes Prof Mark G Humphrey |
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| Affiliation: | 1. Research School of Chemistry, Australian National University, Canberra, ACT 2601 (Australia), Fax: (+61)?2‐6125‐0750;2. School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094 (P.R. China);3. Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore 560080 (India) |
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| Abstract: | The synthesis of fac‐Ir{N,C1′‐(2,2′‐NC5H4C6H3‐5′‐C?C‐1‐C6H2‐3,5‐Et2‐4‐C?CC6H4‐4‐C?CH)}3] ( 10 ), which bears pendant ethynyl groups, and its reaction with RuCl(dppe)2]PF6 to afford the heterobimetallic complex fac‐Ir{N,C1′‐(2,2′‐NC5H4C6H3‐5′‐C?C‐1‐C6H2‐3,5‐Et2‐4‐C?CC6H4‐4‐C?C‐trans‐RuCl(dppe)2])}3] ( 11 ) is described. Complex 10 is available from the two‐step formation of iodo‐functionalized fac‐tris2‐(4‐iodophenyl)pyridine]iridium(III) ( 6 ), followed by ligand‐centered palladium‐catalyzed coupling and desilylation reactions. Structural studies of tetrakis2‐(4‐iodophenyl)pyridine‐N,C1′](μ‐dichloro)diiridium 5 , 6 , fac‐Ir{N,C1′‐(2,2′‐NC5H4C6H3‐5′‐C?C‐1‐C6H2‐3,5‐Et2‐4‐C?CH)}3] ( 8 ), and 10 confirm ligand‐centered derivatization of the tris(2‐phenylpyridine)iridium unit. Electrochemical studies reveal two ( 5 ) or one ( 6 – 10 ) Ir‐centered oxidations for which the potential is sensitive to functionalization at the phenylpyridine groups but relatively insensitive to more remote derivatization. Compound 11 undergoes sequential Ru‐centered and Ir‐centered oxidation, with the potential of the latter significantly more positive than that of Ir(N,C′‐NC5H4‐2‐C6H4‐2)3. Ligand‐centered π–π* transitions characteristic of the Ir(N,C′‐NC5H4‐2‐C6H4‐2)3 unit red‐shift and gain in intensity following the iodo and alkynyl incorporation. Spectroelectrochemical studies of 6 , 7 , 9 , and 11 reveal the appearance in each case of new low‐energy LMCT bands following formal IrIII/IV oxidation preceded, in the case of 11 , by the appearance of a low‐energy LMCT band associated with the formal RuII/III oxidation process. Emission maxima of 6 – 10 reveal a red‐shift upon alkynyl group introduction and arylalkynyl π‐system lengthening; this process is quenched upon incorporation of the ligated ruthenium moiety on proceeding to 11 . Third‐order nonlinear optical studies of 11 were undertaken at the benchmark wavelengths of 800 nm (fs pulses) and 532 nm (ns pulses), the results from the former suggesting a dominant contribution from two‐photon absorption, and results from the latter being consistent with primarily excited‐state absorption. |
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| Keywords: | heterometallic complexes iridium ligand design nonlinear optics ruthenium |
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