Triplet Emission in Platinum-Containing Poly(alkynylsilanes)

Abstract

Synthetic routes to novel oligomeric and polymeric platinum(II)-containing alkynylsilanes were developed. Soluble and thermally stable platinum(II) poly(alkynylsilanes) trans-[−Pt(PBu3)2C⋮C(p-C6H4)C⋮CSiPh2C⋮C(p-C6H4)C⋮C−] n were prepared in good yield by CuI-catalyzed condensation polymerization of trans-[PtCl2(PBu3)2] with HC⋮C(p-C6H4)C⋮CSiPh2C⋮C(p-C6H4)C⋮CH. The regiochemical structure of the polymer was studied by NMR (1H, 13C, 29Si, and 31P) spectroscopy. We report the optical absorption and photoluminescence spectra of such metal-based organosilicon polymer and compare the data with their oligomeric model complexes trans-[Pt(Ph)(PEt3)2C⋮C(p-C6H4)C⋮CSiPh2C⋮C(p-C6H4)C⋮CPt(Ph)(PEt3)2] and trans-[Pt(Ph)(PEt3)2C⋮C(p-C6H4)C⋮CSiPh2C⋮C(p-C6H4)C⋮CPt(PBu3)2C⋮C(p-C6H4)C⋮CSiPh2C⋮C(p-C6H4)C⋮CPt(Ph)(PEt3)2]. Our studies indicate that such organometallic poly(alkynylsilanes) show a strong triplet emission with a very high efficiency of intersystem crossing from the S1 singlet excited state to the T1 triplet excited state. The dependence of intersystem crossing and the spatial extent of singlet and triplet excitons as a function of the central spacer group is discussed in polymetallaynes possessing SiPh2, C6H4 and Pt(PR3)2 (R = Et, Bu) linkers. The photoconducting properties of such silicon-linked platinum polyyne are described.

Spatial Extent of the Singlet and Triplet Excitons in Luminescent Angular‐Shaped Transition‐Metal Diynes and Polyynes Comprising Non‐π‐Conjugated Group 16 Main Group Elements

“…The as-prepared diethynyl synthons were used to form a series of Group 10-12 metallaynes and metallopolymers by adaptation of the reported dehydrohalogenation procedures. [23,24] The triple bonds are represented by T and the diphenyl ether, sulfide, sulfoxide, and sulfone by O, S, SO and SO 2 , respectively. Model metal diynes and polyynes are differentiated by use of the subscript 1 for the polyynes.…”

“…The single 31 P{ 1 H} NMR signals flanked by platinum satellites for the platinum complexes and polymers were consistent with a trans geometry of the squareplanar Pt unit with the 1 J(P,Pt) values typical of those for related trans-PtP 2 systems. [23,24] In all cases, 1 H NMR resonances arising from the protons of the organic moieties were observed. Notably, two distinct 13 C NMR signals for the a-and b-acetylenic carbon atoms were ob-served, and the a-acetylide chemical shifts were shifted downfield with respect to the free dialkyne, in agreement with the formation of a metal À C(sp) s bond.…”

“…[23,24] While we have a long-term interest to observe triplet emission under ambient conditions, this work is attractive in that room-temperature phosphorescence can be clearly identified for our platinum polymers (see Figure 5) and is rarely found in the literature for related systems containing heteroaromatic spacers. Presumably due to the internal heavy-atom effect of the sulfone group, [Pt-T(SO 2 )T] 1 shows the most intense phosphorescence band at 290 K among the four polymers and we can even observe very strong solid-state triplet emission for [Pt-T(SO 2 )T] 1 in which the ratio of integrated intensities of phosphorescence to fluorescence is greater than unity.…”

“…[7,23,24] The triplet energy level can be tuned over a wide range by varying the spacer group R. This has enabled a detailed study of the relationship between triplet energy and the rate of nonradiative decay for this class of conjugated materials. More recently, similar research work has been extended to their closest neighbours, such as d 10 gold(i) [25] and mercury(ii) complexes.…”

Synthesis and Luminescent Properties of Platinum-Containing Polyynes with Tetraacetylenic 9,9-Dihexylfluorene Units

“…We note that the order of S 1 →T 1 crossover efficiency is III＞II, since the energy of the T 1 state is higher for the former, this also agrees with the results obtained from the peak height ratio from triplet emission to singlet emission at 77 K, ∆E(T 1 →S 0 , S 1 →S 0 ) ( Table 2), which has been adopted previously as a good parameter to evaluate the relative ISC efficiency. 39,44 In our systems, the transition metal Pt can exert heavy-atom effect as other transition metals (Au, Hg) 45 in the enhancement of ISC rate from the S 1 singlet excited state to the T 1 triplet excited state. …”