Photophysical properties of trans-platinum acetylide complexes featuring N-heterocyclic carbene ligands

Abstract

A series of trans-N-heterocyclic carbene (NHC) platinum(ii) acetylide complexes of the form (ICy)2Pt(R)2 (where ICy = 1,3-bis-(cyclohexyl)imidazol-2-ylidene and R = 1-Ethynyl-4-(phenylethynyl)benzene (PE2), 2-(9,9-Diethyl-9H-fluoren-7-yl)benzo[d]thiazole (BTF), and 9,9-Diethyl-7-ethynyl-N,N-diphenyl-9H-fluoren-2-amine (DPAF), respectively), were synthesized via Hagihara reaction of the unprotected aryl-acetylide ligands with trans-(ICy)2PtCl2 () in 47-73% yield. Precursor was generated in a one-pot synthesis via formation of a silver carbene precursor followed by transmetallation, and was obtained in high yield (95%). The single-crystal X-ray structures of , were determined and analyzed. The photophysical properties of were compared to their respective tributyl phosphine (PBu3) analogues. The optical properties of the series were studied by UV-Vis spectroscopy, photoluminescence spectroscopy, nanosecond transient absorption spectroscopy, and open aperture nanosecond z-scan. Coupling of the organic chromophores to the platinum center affords efficient intersystem crossing as concluded by the complexes' low fluorescence quantum yields, efficient phosphorescence and intense T1 - Tn absorption. Open aperture z-scan with 606 nm, 10 ns laser pulses showed comparable optical attenuation relative to a standard sample of (PBu3)2Pt(DPAF)2 (). Pulse limiting was achieved via a dual-mechanism of two-photon absorption (2PA) coupled with excited-state absorption (ESA). TD-DFT Computations were also employed for to give greater insight into the nature of the singlet-singlet electronic transitions.

Room‐Temperature Phosphorescent Platinum(II) Alkynyls with Microsecond Lifetimes Bearing a Strong‐Field Pincer Ligand

“…[41,42] In symmetric square planar Pt(II) complexes with similar phenyl acetylide ligands the Pt-C bond distance is generally > 2.0 Å We found the Pt-C alk bond distance in complexes 6-9 to fall between 1.963( 9) Å -1.971(6) Å. [24,43] Alkynyl aryl moieties are essentially perpendicular to the best-fit plane of BIMCA. The structures show no evidence of -stacking or of metallophilic interactions with the nearest Pt•••Pt approach (in 6) exceeding 4 Å.…”

“…In recent investigations, numerous groups have reported bis(N-heterocyclic carbene)pyridyl/phenyl complexes of platinum(II) that emit mixed 3 MLCT/ 3 LLCT phosphorescence (LLCT = interligand charge transfer) that is tunable by varying the alkynyl ligand. [16][17][18][19][20][21][22][23][24][25] Many platinum(II) metallacycles aggregate in the ground state, and often in the excited state to form excimers. [17,26,27] Ground-state aggregation can confer such properties as vapochromism, photochromism, and mechanochromism in solids, leading to applications as sensors and switches.…”

Organometallic rhenium(iii) chalcogenide clusters: coordination of N-heterocyclic carbenes

“…A recent study of highly luminescent trans-platinum acetylide complexes containing NHC ligands compared the photophysical properties of these complexes with their PnBu 3 containing analogs. 16 They reported that substitution of a phosphine for an NHC greatly enhanced the phosphorescent properties, i.e. the NHC platinum complexes had much higher quantum yields and excited state lifetimes.…”

Photophysical Enhancement of Triplet Emitters by Coordination‐Driven Self‐Assembly

“…The synthesis of D1 involved a CuI‐catalyzed coupling reaction of 1 with 4‐ethynylpyridinium chloride in dichloromethane (see Scheme ) . The crude product mixture was purified on a silica gel column with CH 2 Cl 2 and MeOH eluent in 49:1 ratio (isolated yield: 80 %).…”

“…The synthesis of D1 involved aC uI-catalyzed coupling reaction of 1 [22] with 4-ethynylpyridinium chloride in dichloromethane (see Scheme 1). [22] The crude product mixture was purified on as ilicag el column with CH 2 Cl 2 and MeOH eluenti n 49:1 ratio (isolated yield:8 0%). Complex [Pt(dtbpy)(pyridine) 2 ](PF 6 ) 2 2 was obtained as ac olorless crystalline solid with an isolated yield of 40 %b yt reating A1 with pyridinea nd KPF 6 in H 2 Ou nder reflux.…”