Time-Resolved EPR Characterization of a Folded Conformation of Photoinduced Charge-Separated State in Porphyrin−Fullerene Dyad Bridged by Diphenyldisilane

Abstract

For development of the molecular solar-energy conversion systems, it is crucial to investigate how both the molecular geometry and electronic structure of electron donor-bridge-acceptor (D-B-A) molecules contribute to the electronic coupling for the charge-separation (CS) and charge-recombination (CR) processes. In a D-B-A system of a porphyrin-fullerene dyad (ZnP-C(60)) bridged by a diphenyldisilane spacer, we have characterized one specific folded molecular conformation in the CS state among several existing conformations using the time-resolved electron paramagnetic resonance (TREPR) method at low temperature. To determine the molecular conformation and spin-spin exchange coupling of the CS state, we have considered (1) the electron spin polarization transfer from the excited triplet state of the C(60) moiety to the CS state and (2) the sublevel-selective spin relaxations and CR in the CS state. In the CS state of this conformation, although the ZnP cation and C(60) anion radicals are in close proximity, direct overlap between their singly occupied molecular orbitals is small, resulting in detection of the long-lived CS state which has a totally different conformation from the optically detected, charge-transfer (CT) complex. It has been demonstrated that, among several folded and extended molecular conformations created by the flexibility of the -Si-Si- bridge, the EPR conformation can play a role on the prevention of the energy-wasting CR.

Covalent Functionalization of Black Phosphorus with Conjugated Polymer for Information Storage

“…When the positive sweep voltage from 0to+ 3Vwas applied to the device,current through the device was rapidly changed from 10 À8 At o1 0 À4 Aa tt he turn-on voltage of + 1.94 V (sweep 1), implying that the device was converted from the OFF state to the ON state.T his switch-on process is also called as the writing process of ad igital memory cell. Like the poly[(1,4-diethynyl-benzene)-alt-BODIPY]-grafted RGO (PDBD-g-RGO)-based memory device reported in our previous work, [23] PDDF-g-BP-based device can only be switched on when the positive-bias was applied to the device (Figure 6d). Like the poly[(1,4-diethynyl-benzene)-alt-BODIPY]-grafted RGO (PDBD-g-RGO)-based memory device reported in our previous work, [23] PDDF-g-BP-based device can only be switched on when the positive-bias was applied to the device (Figure 6d).…”

“…[23] To explore the photoinduced charge transfer occurred in PDDF-g-BP,w em easured LEPR spectra of the samples,asshown in Figure 5. [23] To explore the photoinduced charge transfer occurred in PDDF-g-BP,w em easured LEPR spectra of the samples,asshown in Figure 5.…”

Reduced Graphene Oxide Chemically Modified with Aggregation‐Induced Emission Polymer for Solid‐State Optical Limiter

“…From Figure a, it can be seen that the main absorption peak of PAHFTP is located at 367 nm in dilute NMP solution due to the π–π* transition derived from the conjugated polymer backbone. After covalent grafting of PAHFTP onto the RGO surface, this peak is blueshifted by 7 nm due to the possible electron transfer from the polymer to RGO, which was confirmed by light‐induced EPR spectroscopy . As shown in Figure b, the as‐prepared PFTP‐RGO exhibits a strong EPR signal with an Δ H pp (i.e., the peak‐to‐peak width) of 6.06 G and a g value of 2.0048 before illumination.…”

In Situ Synthesis and Characterization of Poly(aryleneethynylene)‐Grafted Reduced Graphene Oxide

“…The electron paramagnetic resonance (EPR) technique, which has been used to explore photoinduced electron transfer pathway in our previous work, was then employed to measure the electron paramagnetic performance of PAE‐ g ‐RGO before and after illumination (Figure a) . Before illumination, the LEPR spectrum of the sample exhibited a typical radical signal centered on g =2.0037, suggesting the existence of unpaired electrons or free radicals in PAE‐ g ‐RGO.…”