Electroswitchable Photoluminescence Activity:  Synthesis, Spectroscopy, Electrochemistry, Photophysics, and X-ray Crystal and Electronic Structures of [Re(bpy)(CO)₃(C⋮CC₆H₄C⋮C)Fe(C₅Me₅)(dppe)][PF₆]_n (n = 0, 1)

Abstract

A novel heterobimetallic alkynyl-bridged complex, [Re(bpy)(CO)(3)(C[triple bond]C[bond]C(6)H(4)[bond]C[triple bond]C)Fe(C(5)Me(5))(dppe)], 1, and its oxidized species, [Re(bpy)(CO)(3)(C[triple bond]C[bond]C(6)H(4)[bond]C[triple bond]C)Fe(C(5)Me(5))(dppe)][PF(6)], 2, have been synthesized and their X-ray crystal structures determined. A related vinylidene complex, [Re(bpy)(CO)(3)(C[triple bond]C[bond]C(6)H(4)[bond](H)C[double bond]C)Fe(C(5)Me(5))(dppe)][PF(6)], 3, has also been synthesized and characterized. The cyclic voltammogram of 1 shows a quasireversible reduction couple at -1.49 V (vs SCE), a fully reversible oxidation at -0.19 V, and a quasireversible oxidation at +0.88 V. In accord with the electrochemical results, density-functional theory calculations on the hydrogen-substituted model complex Re(bpy)(CO)(3)(C[triple bond]C[bond]C(6)H(4)[bond]C[triple bond]C)Fe(C(5)H(5))(dHpe) (Cp = C(5)H(5), dHpe = H(2)P[bond](CH(2))(2)[bond]PH(2)) (1-H) show that the LUMO is mainly bipyridine ligand pi* in character while the HOMO is largely iron(II) d orbital in character. The electronic absorption spectrum of 1 shows low-energy absorption at 390 nm with a 420 nm shoulder in CH(2)Cl(2), while that of 2 exhibits less intense low-energy bands at 432 and 474 nm and additional low-energy bands in the NIR at ca. 830, 1389, and 1773 nm. Unlike the related luminescent rhenium(I)-alkynyl complex [Re(bpy)(CO)(3)(C[triple bond]C[bond]C(6)H(4)[bond]C[triple bond]C[bond]H)], 4, complex 1 is found to be nonemissive, and such a phenomenon is attributed to an intramolecular quenching of the emissive d pi(Re) --> pi*(bpy) (3)MLCT state by the low-lying MLCT and LF excited states of the iron moiety. Interestingly, switching on of the luminescence property derived from the d pi(Re) --> pi*(bpy) (3)MLCT state can be demonstrated in the oxidized species 2 and the related vinylidene analogue 3 due to the absence of the quenching pathway.

Mixed‐Transition‐Metal Acetylides: Synthesis and Characterization of Complexes with up to Six Different Transition Metals Connected by Carbon‐Rich Bridging Units

“…It was found that the reaction of organic 5 with 9 gave somewhat better yields than with 8 with 9. Desilyl-A C H T U N G T R E N N U N G ation of 11 with [nBu 4 N]F (Bu = butyl) afforded 12 in almost quantitative yield. On the other hand, the introduc-…”

“…Alternatively, the reaction of 13 with 2-methyl-3-butyn-2-ol (formation of 16) under typical Sonogashira cross-coupling conditions also gave 15 (Scheme 3). [15] Desilyl-A C H T U N G T R E N N U N G ation of 14 was achieved by addition of [nBu 4 N]F. The de-protection of the propargylic group in 16 was carried out with powdered potassium hydroxide in toluene. Both reactions produced 15 as a colorless solid in good yield.…”

“…[16] This behavior is most probably attributed to the low solubility of 17 in diethyl ether and to the observation that Li-15 decomposed quite fast in tetrahydrofuran. 3 Re- 4 ] with the in situ lithiated alkyne, respectively, were not successful. [6b, 17] An optimized route to 10 is the reaction of 12 with [(h 2 -dppf)A C H T U N G T R E N N U N G (h 5 -C 5 H 5 )RuCl] (7) in a 1:1 dichloromethane/methanol mixture with the simultaneous addition of [NH 4 ]PF 6 and the base KOtBu (OtBu = tert-butan-…”

“…Preparation from 14: [nBu 4 N]F (1.0 m in THF, 1.5 mL, 1.50 mmol) was slowly added to a solution of 14 (600 mg, 1.32 mmol) in THF (30 mL). The resulting reaction solution was stirred for 1 h at 25 8C.…”

“…[2] To control the structure and composition of multimetallic complexes, a prior synthesis of multifunctional bridging ligands is necessary that allows the stepwise metal coordination. Examples of such connectivities are 1,4-diethynylbenzene, [3,4] 1,3,5-triethynylbenzene, [5,6] 1-ethynyl-4-diphenylphosphinobenzene, [7] 5-ethynyl-2,2'-bipyridyl, [8] and 2,5-bisA C H T U N G T R E N N U N G (alkynyl) thiophenes. [9,10] Based on these cores, mainly homometallic transition-metal compounds have been synthesized, while less is known about heteromultimetallic molecules.…”