Drastic Tuning of the Photonic Properties of «(Push–Pull)_n» trans‐Bis(ethynyl)bis(Tributylphosphine)Platinum(II)‐Containing Polymers

Abstract

The trans-Pt(PBu3)2 Cl2 complex reacts with 1 equiv. of 2,6-diethynyl-AQ and 2 equiv. of 2-ethynyl-AQ (AQ = anthraquinone) to form the polymer (trans-Pt(2,6-diethynyl-AQ)2 (PBu3)2)n, 1, and the model compounds, 2, trans-Pt(PBu3)2 (2-ethynyl-AQ)2 (in a 20:1 ratio as trans-(2a) and cis-(2b) rotational isomers), respectively. These redox-active and luminescent materials have been characterized by gel permeation chromatography, thermal gravimetric analysis, X-ray crystallography, electrochemistry, photophysics, and DFT computations (B3LYP). The typical π,π* T2 → S0 phosphorescence centered on the trans-Pt(PBu3)2 (aryl)2 chromophore, [Pt], generally encountered for the analogous polymers (trans-Pt(PBu3)2 (aryl)2-acceptor)n (acceptor = quinonediimine, QN2; anthraquinone diimine, AQN2), for which the CT T1 → S0 emission is silent, has been completely annihilated and replaced by a red-shifted T1 → S0 emission in 1 and 2a, which arise from a triplet charge transfer excited state [Pt]→ AQ.

Cross Conjugated Organometallic Polymers Exhibiting Ultrafast Excitation Energy Channeling: Drastic Effect of the Connectivity

“…Conversely, P2 is weakly emissive at both 298 and 77 K upon exciting in the low‐energy absorption (i.e., λ exc = 400 nm; note that the blank experiment with the solvent alone was performed). This result comes as a surprise with respect to P0 , which exhibits a rather intense emission at 77 K (λ exc = 610 nm) arising from the CT 3 ( [Pt] → anthraquinone)* manifold, but not with respect to P3 , which does not show any emission from the lowest energy singlet and triplet excited states …”

“…The synthesis of polymers P1 and P2 are shown in Scheme and the chemical steps are considered standard. Compounds a1 and b1 were obtained by reacting 1 with 4‐nitroaniline in a ratio of 1:1 and 1:2, respectively. After the removal of the TMS groups in compound b1 , the resulting intermediate b2 was obtained.…”

“…This chromophore was also used to prepare new materials exhibiting non‐linear optic properties, and for the design of photonic devices such as light emitting diodes and solar cells . We recently reported a “push–pull” [Pt] /anthraquinone‐containing polymer ( P0 ; Figure ) that exhibits redox properties and is strongly emissive at 77 K (τ P = 340 ± 5 µs) . A direct C — C bond secures the conjugation between the electron donor [Pt] and acceptor anthraquinone, thus promoting the presence of an intense charge transfer band 3 ( [Pt] → anthraquinone)* in the visible region.…”

Ultrafast Photoinduced Electron Transfers in Platinum(II)-Anthraquinone Diimine Polymer/PCBM Films

“…P1 and P2 were found fluorescent from the lowest energy excited state at room temperature, thus drastically contrasting with the ( [Pt]-[AQ] ) n , ( [Pt]-[QI] ) n , − and ( [Pt]-[AQI] ) n , polymers reported to be nonemissive or, at best, only luminescent in glassy matrices at 77 K. The absorption, excitation, and fluorescence spectra of 2a , 2b , M1 , M2 , P1 , and P2 in 2MeTHF at 298 K are presented in Figure , and the absorptivity data are summarized in Table . From an examination of the tails, where the 0–0 peak positions are expected (i.e., these tails spread, respectively, from ∼500 to ∼550 nm and from ∼525 to ∼575 nm for M1 and M2 and from ∼550 to ∼600 and from ∼550 to ∼625 nm for P1 and P2 , respectively), it is concluded that the 0–0 peak positions should be placed at lower energy for P1 and P2 in comparison with M1 and M2 .…”

“…To the best of our knowledge, the highest photoconversion efficiency (PCE) was recently reported to be 5.29% for a BHJSC containing the [Pt] moiety. , Concurrently, studies on complexes bearing [Pt] units indicated that the charge separated states are formed in the short picosecond (ps) time scale − and that the [Pt] unit could mediate the electron transfer. − Over the years, it was suggested that anchoring diphenylamine pendants as electron-rich groups , and using the electron-deficient anthraquinone, AQ , moiety , should improve the PCEs of [Pt] -containing materials for solar cells. Alternatively to ( [Pt] - [AQ] ) n polymers, polymers containing anthraquinone diimine, AQI (i.e., ( [Pt]-[AQI] ) n ), were also designed. , These latter materials are nonemissive at room temperature (RT), but exhibit both low potential oxidation and reduction processes, , rendering them suitable for photoinduced electron transfers processes. Despite the fact that [Pt] is a common synthon and its relevance to its use in solar cells, there is, to the best of our knowledge, no investigation reporting the rates of photoinduced electron transfer between [Pt] and an electron acceptor.…”