Photoinduced electron transfer of platinum(ii) bipyridine diacetylides linked by triphenylamine- and naphthaleneimide-derivatives and their application to photoelectric conversion systems

Abstract

The recently reported efficient charge-separated system based on bipyridine-diacetylide platinum(ii) complexes was applied to photoelectric conversion systems herein, based on the design and synthesis of two triads: MTA-Pt-NDISAc (3, MTA: dimethoxytriphenylamine, Pt: platinum(ii) complex, NDISAc: thioacetate derivative linked to naphthalenediimide) and MTA-Pt-MNICOOH (4, MNICOOH: naphthaleneimide-4-carboxylic acid). The charge-separated (CS) states of triads 3 and 5 (MOM-protected 4) were effectively generated by photo-induced electron transfer in both THF and toluene, although the rate of formation of the CS state from 5 was relatively slow in toluene. The lifetimes of these CS states were determined to be 730 ns in toluene and 61 ns (70%) and 170 ns (30%) as a double exponential decay in THF for 3, and 600 ns in toluene and 170 ns in THF for 5. The acetylthio group of triad 3 was exploited in the preparation of a self-assembled monolayer (SAM) on a gold surface. Photocurrent was detected upon irradiation of an electrochemical cell comprising Au/3/Na ascorbate/Pt, which was ascribed to the platinum(ii) complex based on the action spectrum. The carboxylic acid group of triad 4 facilitated adsorption on the TiO2 surface, and a dye-sensitized solar cell constructed based on FTO/TiO2/4/electrolyte (LiI-I2)/Pt exhibited a poor energy conversion efficiency (η = 0.20%) based on the incident photon-to-current conversion efficiency spectrum and the I-V curve. This poor efficiency may be derived from the bent molecular shape of 4, or may be due to a possible high energy barrier in the electron injection process through the adsorption site.

Long‐Lived Charge‐Transfer State Induced by Spin‐Orbit Charge Transfer Intersystem Crossing (SOCT‐ISC) in a Compact Spiro Electron Donor/Acceptor Dyad

“…We observed the growth of an ESA band at 425 nm, assigned to the NI −. absorption (Figure g), concurrently with the decrease of a broad weak ESA band in the range of 480–650 nm which is attributed to 3 NI* state of RB ‐ NI (Figure g). Thus the formation of the final transient species of RB ‐ NI is driven by the 3 NI precursor ( 3 NI*→ 3 CT transition) and it is long‐lived (0.94 μs in deaerated n ‐hexane, Figure i).…”

“…Mimicking the natural photosynthetic reaction centers with the aim to attain a charge transfer (CT) state with high energy and long lifetime has attracted much attention . In photosynthesis, a cascade of electron‐transfer processes takes place in the reaction center upon photoexcitation of the light‐harvesting antenna, leading to the formation of a final CT state at approximately 0.5 eV, that lives up to a few seconds .…”

“…1 μs) was observed in a N^N Pt II bis(acetylide) complex and the formation of a spin‐correlated radical pair (SCRP) was confirmed by TREPR . These molecular systems are synthetically demanding, because the π‐conjugation frameworks of electron D and A must be isolated from the coordination center, to reduce the electronic coupling between electron D and A and avoid the shortening of the 3 CT state lifetime (heavy‐atom effect) . Another strategy is based on the intrinsic ISC ability of the electron D or A (e.g.…”

An N^N Platinum(II) Bis(acetylide) Complex with Naphthalimide and Pyrene Ligands: Synthesis, Photophysical Properties, and Application in Triplet–Triplet Annihilation Upconversion

“…The molecular structures and synthesis procedures of the ligands (NI‐H and Py‐H) and complexes (Pt‐NI‐Py, Pt‐NI, and Pt‐Py) are displayed in Scheme . The heteroleptic complex Pt‐NI‐Py was synthesized from a mixture of the two ligands and Pt(dbbpy)Cl 2 catalyzed by CuI under N 2 , . The ligands and reference complexes Pt‐NI and Pt‐Py were synthesized according to reported methods , , …”

The Ugi four-component reaction as a concise modular synthetic tool for photo-induced electron transfer donor-anthraquinone dyads

“…Among several representations for calculating the Gibbs free energy of the electron transfer [88–89] can be described by Eq. 1 [90]…”