Synthesis, characterization and luminescence properties of homoleptic platinum(ii) acetylide complexes

Abstract

A family of homoleptic tetraalkynylplatinate() complexes (NBu 4 ) 2 [Pt(C᎐ ᎐ ᎐ CR) 4 ] containing various arylsubstituted (R = C 6 H 4 X), where X is an electron-donating, -withdrawing or -delocalizing substituent, and ethynylpyridine (C 5 H 4 N-2, C 5 H 4 N-4) ligands have been prepared. The structures of complexes with R = (4-CF 3 )C 6 H 4 (4ؒ2HCCl 3 ), (4-CN)C 6 H 4 (6ؒH 2 O) and C 5 H 4 N-4 (9bؒHC᎐ ᎐ ᎐ CC 5 H 4 N-4ؒ2H 2 O) have been determined by single-crystal X-ray diffraction. While in the case of 4 two molecules of CHCl 3 are incorporated to the anion by short CH ؒ ؒ ؒ π interactions, for the para-pyridylethynyl derivative one H 2 O molecule connect different anions through moderate N ؒ ؒ ؒ H-O-H ؒ ؒ ؒ N intermolecular interactions, giving an extended one-dimensional chain. The photophysical and electrochemical properties of the complexes have been examined. All of them display emissions at 77 and 298 K in the fluid and solid state, with lifetimes in the microsecond regime. In some cases the emission profile is clearly the envelope of several closely bands, whose relative intensity depends on the excitation energy. On the basis of TD-DFT theoretical calculations on the anion [Pt{C᎐ ᎐ ᎐ C(4-CN)C 6 H 4 } 4 ] 2Ϫ of complex 6, it is proposed that the emissions are due to triplet intraligand excited states, with both an aryl (or pyridyl) and acetylenic character, which arise from an admixture of π π*(C᎐ ᎐ ᎐ CR) IL and d π (Pt) π*(C᎐ ᎐ ᎐ CR) MLCT transitions.

Novel Luminescent Mixed‐Metal PtTl‐Alkynyl‐Based Complexes: The Role of the Alkynyl Substituent in Metallophilic and η2(π⋅⋅⋅Tl)‐Bonding Interactions

“…Upon [57] but with a lower energy (D = 1185 cm À1 ). Similar behavior was observed in acetone (see Table 4).…”

“…[52][53][54] Many of these complexes, particularly those containing Tl I , have been shown to display luminescent properties, which have invariably been attributed to intermetallic interactions; however, a number of Pt II,0 ÀTl I complexes with strong Pt-Tl interactions do not exhibit any detectable emission. [55,56] In the past two decades, much has been discovered about the photoluminescence behavior of alkynylplatinum(ii) complexes, [57][58][59][60][61][62] but, in comparison, relatively little is understood about the emissive properties of heteropolynuclear platinum systems containing alkynyl bridging ligands. [63][64][65][66] Recent studies by us [67][68][69][70] and others [63,66] 8 ] by sandwiching naked Tl I centers through Tl I -alkyne interactions, [71] thus indicating that in these systems the Tl I centers have a stronger preference for the electron-rich alkynyl entities than for the basic Pt II center.…”

“…[57] [PtCl 2 (tht) 2 ] (0.30 g, 0.68 mmol) was added to a fresh solution of LiCCNp (4.08 mmol) in diethyl ether at a low temperature (À30 8C). After stirring at a low temperature for 10 min, the mixture was allowed to reach room temperature (ca.…”

“…The acetylenes were purchased and used without further purification. [PtCl 2 (tht) 2 ] [89] and (NBu 4 ) 2 [Pt(CCR) 4 ] [57] (R = 4-CH 3 C 6 H 4 , 4-CF 3 C 6 H 4 ) were prepared as described previously.…”

Homo‐ and Heteropolynuclear Platinum Complexes Stabilized by Dimethylpyrazolato and Alkynyl Bridging Ligands: Synthesis, Structures, and Luminescence

“…On the basis of previous assignments [5,10,[120][121][122][123][124] and theoretical studies, [120,[125][126][127] the lowenergy shoulder that is observed at 315 nm in CH 2 Cl 2 and slightly blue-shifted in NCMe (310 nm), is attributed tentatively to an admixture of p!p*A C H T U N G T R E N N U N G (C CPh) IL/dp(Pt)!p*A C H T U N G T R E N N U N G (C CPh) MLCT. [128] In agreement with this assignment, the band is notably blue-shifted in relation to that seen in the homoleptic derivative (NBu 4 ) 2 [PtA C H T U N G T R E N N U N G (CCPh) 4 ] (347 nm) [127] in which its dianionic nature presumably increases the energy of the HOMO (dp(Pt)/pA C H T U N G T R E N N U N G (CC)), [128] . [130] The absorption spectra of the hexanuclear Pt 2 M 4 complexes 2-4 ( Figure 6) show the expected high-energy intraligand bands and are characterized by a low-energy band that appears at 346 nm in the platinum-copper complex 2, and is slightly blue-shifted in the platinum-silver 3 (331 nm) and the platinum-gold 4 (330 nm) derivatives.…”