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Syntheses, Spectroscopic, Electrochemical, and Third‐Order Nonlinear Optical Studies of a Hybrid Tris{ruthenium(alkynyl)/(2‐phenylpyridine)}iridium Complex
Author(s) -
Zhao Huajian,
Simpson Peter V.,
Barlow Adam,
Moxey Graeme J.,
Morshedi Mahbod,
Roy Nivya,
Philip Reji,
Zhang Chi,
Cifuentes Marie P.,
Humphrey Mark G.
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201500951
Subject(s) - iridium , ruthenium , tris , electrochemistry , order (exchange) , chemistry , nonlinear optical , nonlinear system , combinatorial chemistry , materials science , organic chemistry , catalysis , physics , electrode , biochemistry , finance , quantum mechanics , economics
The synthesis of fac ‐[Ir{ N , C 1 ′‐(2,2′‐NC 5 H 4 C 6 H 3 ‐5′‐CC‐1‐C 6 H 2 ‐3,5‐Et 2 ‐4‐CCC 6 H 4 ‐4‐CCH)} 3 ] ( 10 ), which bears pendant ethynyl groups, and its reaction with [RuCl(dppe) 2 ]PF 6 to afford the heterobimetallic complex fac ‐[Ir{ N , C 1 ′‐(2,2′‐NC 5 H 4 C 6 H 3 ‐5′‐CC‐1‐C 6 H 2 ‐3,5‐Et 2 ‐4‐CCC 6 H 4 ‐4‐CC‐ trans ‐[RuCl(dppe) 2 ])} 3 ] ( 11 ) is described. Complex 10 is available from the two‐step formation of iodo‐functionalized fac ‐tris[2‐(4‐iodophenyl)pyridine]iridium(III) ( 6 ), followed by ligand‐centered palladium‐catalyzed coupling and desilylation reactions. Structural studies of tetrakis[2‐(4‐iodophenyl)pyridine‐ N , C 1 ′](μ‐dichloro)diiridium 5 , 6 , fac ‐[Ir{ N , C 1 ′‐(2,2′‐NC 5 H 4 C 6 H 3 ‐5′‐CC‐1‐C 6 H 2 ‐3,5‐Et 2 ‐4‐CCH)} 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′ ‐NC 5 H 4 ‐2‐C 6 H 4 ‐2) 3 . Ligand‐centered π–π* transitions characteristic of the Ir( N,C′ ‐NC 5 H 4 ‐2‐C 6 H 4 ‐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 Ir III/IV oxidation preceded, in the case of 11 , by the appearance of a low‐energy LMCT band associated with the formal Ru II/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.