Occurrence of photoinduced charge separation by the modulation of the electronic coupling between pyrene dimers and chemically converted graphenes

Abstract

The photoexcitation of the pyrene dimer on graphene resulted in the final formation of a charge-separated state following an exciplex formation, while that of the pyrene monomer on graphene generated the corresponding exciplex solely due to the difference in the electronic coupling between the pyrene and the graphene.

Long-Range Observation of Exciplex Formation and Decay Mediated by One-Dimensional Bridges

“…Although the phenylpinacolborane groups in SWNT−ph 1 −Bpin may form the paired structures on SWNT, the low yield (12−14%) of the Suzuki coupling reaction rendered the porphyrin groups monomeric in ZnP−ph n −SWNT and ZnP−xy n−1 −ph 1 − SWNT. 26,46 ATR-IR (Figures S2 and S4 The 1D structures of SWNTs were verified by TEM (Figures S7 and S8) and AFM measurements (Figures S9 and S10).…”

“…Taking into account the size of the porphyrin (1.8 nm) and the porphyrin surface coverage on SWNTs, the ZnP molecules are unlikely to be interacted directly each other on SWNTs. Although the phenylpinacolborane groups in SWNT–ph 1 –Bpin may form the paired structures on SWNT, the low yield (12–14%) of the Suzuki coupling reaction rendered the porphyrin groups monomeric in ZnP–ph n –SWNT and ZnP–xy n –1 –ph 1 –SWNT. , ATR-IR (Figures S2 and S4) and resonant Raman spectra (Figures S5 and S6) of p-SWNT, SWNT–ph 1 –Bpin, ZnP–ph n –SWNT, and ZnP–xy n –1 –ph 1 –SWNT ( n = 1–5) also support the surface modification on the SWNTs. The 1D structures of SWNTs were verified by TEM (Figures S7 and S8) and AFM measurements (Figures S9 and S10).…”

“…On a basis of a number of studies on D–B–A systems, − it has been well-established that the D–A electronic coupling mediated by bridge decays exponentially with increasing D–A separation distance, and thereby, the rates of the CS and CR are also decreased exponentially. However, the examples of the exciplex formation and decay in D–B–A systems have been limited so far compared to those of the corresponding CS and CR. ,,,,− We have prepared zinc porphyrin (ZnP) donor–fullerene C 60 acceptor linked systems with systematically controlled D–A separation distances ( R DA ), where either the exciplex or CS state or both are formed strongly dependent on the ZnP–C 60 separation distance and environment. , Very recently, we also constructed two-dimensional (2D) chemically converted graphenes (CCGs) acceptor covalently modified with ZnP donors through tuned lengths of linear oligo­( p -phenylene) bridges (ZnP–ph n –CCG, n = 1–5) . Photoexcitation of the ZnP moieties in ZnP–ph n –CCG ( n = 1–5) was found to cause exclusive formation of an exciplex state, which rapidly decayed to the ground state without yielding the complete charge-separated state.…”

1,7-Dipyrene-Containing Aza-BODIPYs: Are Pyrene Groups Effective as Ligands To Promote and Direct Complex Formation with Common Nanocarbon Materials?

“…The pyrene ligands installed have been reported to serve as effective noncovalent linkers to nanocarbon surfaces, − and evidence for photoinduced electron transfer between organic chromophores and a nanocarbon surface following excitation at around 400 nm has been presented. We report the synthesis and characterization of a series of 1,7-dipyrene aza-BODIPYs ( 5a – e , Scheme and Synthesis and Characterization of 5a – e ) and the subsequent investigation of noncovalent complex formation with potential nanocarbon electron acceptors in solution (Titration with Nanocarbon Materials in Solution) and in the solid state (Solid-State Mixtures).…”

Photophysical Properties of Porphyrin Dimer–Single-Walled Carbon Nanotube Linked Systems

“…Zincporphyrin (ZnP) dimer–SWNT linked systems with m - and p -phenylene linkers (denoted as (ZnP- m -ph) 2 -SWNT and (ZnP- p -ph) 2 -SWNT, respectively) were prepared by the direct addition reaction of the in situ generated phenyl radicals bearing a porphyrin unit onto purified SWNT (p-SWNT) sidewalls (Scheme , upper), as we have established for the pyrene dimer–SWNT linked systems. ,, The ZnP unit with sterically less-hindered ethyl groups at the three meso -positions was utilized to further facilitate the dimer formation owing to the intense intermolecular π–π interaction between the porphyrin rings. As a reference, we also synthesized a ZnP monomer–SWNT linked system with the p -phenylene linker (ZnP- p -ph-SWNT) by the two-step method, that is, Suzuki coupling reaction between the preprepared p- phenylpinacolborane (pinB -p -ph) functionalized SWNT (pinB- p -ph-SWNT) and the ZnP with a bromo at the meso position (Scheme , lower).…”