Sequential Construction Strategy for Rational Design of Luminescent Iridacycles

Abstract

A convenient and general strategy has been developed to synthesize stable iridapolycycles 5–8. Reaction of arylacetylenes with iridium-hydride complex [IrH­(CO)­Cl­(PPh3)3]­BF4 via nucleophilic addition, oxidative decarbonylation, and C–H bond activation results in the formation of a series of iridacyclopentadiene derivatives, including benzo-iridacyclopentadiene 5, naphtho-iridacyclopentadiene 6, pyreno-iridacyclopentadiene 7, and thieno-iridacyclopentadiene 8. These iridapolycycles display high thermal and air stability yet can be further functionalized via facile ligand substitution reactions. As an example, complex 5 was used as a metallosynthon to react with 2,2′-dipyridyl to give intensely luminescent Ir­(III) complex 9 bearing one C∧C and one N∧N ligands. Density functional theory (DFT) calculations reveal that the lowest unoccupied molecular orbitals (LUMOs) of iridapolycycles 5–8 are located on the phosphonium groups while the highest occupied molecular orbitals (HOMOs) are mainly located on the metal-embedded C∧C frameworks. Our method offers a sequential construction strategy for constructing luminescent iridacycles, which potentially allows facile tuning of the photoluminescence properties by modulating the C∧C and N∧N moieties independently.

Color-Tuning Strategy for Iridapolycycles [(N∧N)Ir(C∧C)ClPPh3]+ by the Synergistic Modifications on Both the C∧C and N∧N Units

“…To our delight, 4−12 were efficiently synthesized by treatment of 1, 1-Br, or 1-F with the corresponding N ∧ N ligands in the presence of trimethylamine oxide and sodium hexafluorophosphate under refluxing in chloroform (Scheme 2). In addition, a 64% yield of 3 was achieved by the one-pot synthesis, which is slightly higher than our previously reported method 13 (60%, the yield of 2-benzo was considered). In this event, compound 12 is failed to be obtained through this onepot method from the corresponding iridium vinyl complex.…”

“…NMR spectroscopic experiments were performed on Bruker Avance III 850 MHz spectrometer, Bruker Avance III 500 MHz and Bruker Avance II 400 MHz. The 1 H and 13 C NMR chemical shifts shown are relative to TMS, and the 31 P NMR chemical shifts shown are relative to 85% H 3 PO 4 . Elemental analyses were performed on an Elementar Vario EL III elemental analyzer.…”

“…31 P NMR (161.9 MHz, CDCl 3 ): δ = 19.9 (s, CPPh 3 ), −1.0 (s, IrPPh 3 ). 13 (346 mg, 1.32 mmol) were added to a solution of [IrH(CO)Cl(PPh 3 ) 3 ]BF 4 (500 mg, 0.44 mmol) in chloroform (10 mL). The mixture was stirred in N 2 at room temperature for 3 h to give a clear solution.…”

“…We have previously demonstrated that iridacyclopentadiene derivatives represent a promising scaffold for intriguing modification of emission wavelength. 13 However, the quantum yields of these iridacyclopentadiene derivatives are not sufficient to be used as phosphorescent materials, partially due to the inappropriate orbital distribution in the LUMO. In addition, multistep synthesis and time-consuming purification were required for the previous synthetic manipulations to obtain these phosphorescent iridapolycycles.…”

Unexpected Solvent Effects in the Isomerization of iPrPCPIr(η2‐PhC≡CPh) to a 1‐Iridaindene

“…As well, luminescent phosphonium substituted iridaindenes were recently synthesized by Xu et al. through the reaction of [IrH(CO)Cl(PPh 3 ) 3 ]BF 4 with arylacetylenes …”