Symmetry-Breaking Charge Separation and Null Aggregates

The Journal of Physical Chemistry C, Год журнала: 2024, Номер 128(1), С. 248 - 260

Опубликована: Янв. 2, 2024

The relationship between symmetry-breaking charge separation (SB-CS) and null aggregate (NA) formation in molecular dimer complexes is investigated theoretically, with applications mainly to dimers based on PDI chromophores. Both processes derive from points, which are defined by degeneracies either the upper or lower adiabatic exciton bands. Hamiltonian contains intermolecular coupling derived interacting transition dipole moments (Coulomb coupling), gives rise Frenkel excitons, as well excitons charge-transfer (CT) driven electron (te) hole (th) hopping integrals. A recipe for efficient SB-CS presented, which, beyond Weller condition─which holds that solvent-stabilized CT state should appear below optical gap -includes two additional conditions: presence of a point and, just important, lopsided transfer integrals, |te| ≫ |th| |te|. When such conditions met, developing asymmetry optimized response small fluctuations polar solvent-induced electric field, eventually leads charge-separated state. It shown can also occur H-dimers significant cofacial overlap, consistent observations made several groups.

Язык: Английский

---

Null Exciton-Coupled Chromophoric Dimer Exhibits Symmetry-Breaking Charge Separation

Journal of the American Chemical Society, Год журнала: 2021, Номер 143(34), С. 13769 - 13781

Опубликована: Авг. 9, 2021

A comprehensive understanding of the structure-property relationships in multichromophoric architectures has pushed limits for developing robust photosynthetic mimics and molecular photovoltaics. The elusive phenomenon null exciton splitting gathered immense attention recent years owing to occurrence unique chromophoric consequent emergent properties. Herein, we unveil hitherto unobserved coupling assisted highly efficient photoinduced symmetry-breaking charge separation (SB-CS) a Greek cross (+)-oriented spiro-conjugated perylenediimide dimer (Sp-PDI2). Quantum chemical calculations have rationalized infrequent manifestation behavior Sp-PDI2. Negligible contribution long-range Coulombic short-range charge-transfer mediated renders monomer-like spectroscopic signature Sp-PDI2 toluene. (+)-arranged possesses selective hole-transfer coupling, facilitating ultrafast dissociation excitons evolution charge-separated state polar solvents. Radical cationic anionic signatures were characterized by employing femtosecond transient absorption spectroscopy. substantial hole transfer electronic lower activation energy barrier accelerated rate. rate recombination (CR) markedly decelerated due falling into inverted region Marcus parabola, where driving force CR is larger than total reorganization CR. Hence, ratio rates SB-CS over exhibited an unprecedently high value 2647 acetonitrile. current study provides impeccable evidence role filtering governing thereby novel insights towards design biomimics advanced functional materials.

Язык: Английский

---

Create a strong internal electric-field on PDI photocatalysts for boosting phenols degradation via preferentially exposing π-conjugated planes up to 100%

Applied Catalysis B Environment and Energy, Год журнала: 2021, Номер 300, С. 120762 - 120762

Опубликована: Сен. 27, 2021

Язык: Английский

---

Symmetry-Breaking Charge Separation in Molecular Constructs for Efficient Light Energy Conversion

ACS Energy Letters, Год журнала: 2022, Номер 7(2), С. 696 - 711

Опубликована: Янв. 26, 2022

The generation of electron–hole radical pair at the active layer organic photovoltaics through symmetry-breaking charge separation (SB-CS) has a crucial role in enhancing open-circuit voltage (Voc) and thereby increasing power conversion efficiency. Since SB-CS materials achieve intramolecular with negligible energetic driving force decelerated recombination (CR) rate, been subjected to extensive experimental theoretical studies. This Focus Review assesses fundamentals photosynthetic reaction centers, especially "special pair", discusses how covalent control over geometric arrangement, surrounding dielectric medium, substitutions on multichromophoric perylenediimide architecture affects energy landscape CR. We systematically summarize kinetically favored undesirable radiative non-radiative deactivation channels CR processes diverse chromophoric arrangements. Here, we suggest new rational design principles fine-tune electron-transfer dynamics molecular level improve performance light–energy devices.

Язык: Английский

---

Coherence in Chemistry: Foundations and Frontiers

Chemical Reviews, Год журнала: 2024, Номер 124(21), С. 11641 - 11766

Опубликована: Окт. 23, 2024

Coherence refers to correlations in waves. Because matter has a wave-particle nature, it is unsurprising that coherence deep connections with the most contemporary issues chemistry research (e.g., energy harvesting, femtosecond spectroscopy, molecular qubits and more). But what does word "coherence" really mean context of molecules other quantum systems? We provide review key concepts, definitions, methodologies, surrounding phenomena chemistry, we describe how terms "quantum coherence" refer many different chemistry. Moreover, show these notions are related concept an interference pattern. indeed complex, ambiguous definitions may spawn confusion. By describing contexts for sciences, aim enhance understanding communication this broad active area

Язык: Английский

---

Mechanism of Ultrafast Triplet Exciton Formation in Single Cocrystals of π-Stacked Electron Donors and Acceptors

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(40), С. 18607 - 18618

Опубликована: Сен. 30, 2022

Ultrafast triplet formation in donor–acceptor (D–A) systems typically occurs by spin–orbit charge-transfer intersystem crossing (SOCT-ISC), which requires a significant orbital angular momentum change and is thus usually observed when the adjacent π of D A are orthogonal; however, results presented here show that subnanosecond series D–A cocrystals form one-dimensional cofacial stacks. Using ultrafast transient absorption microscopy, photoexcitation single cocrystals, where coronene (Cor) or pyrene (Pyr) N,N-bis(3′-pentyl)-perylene-3,4:9,10-bis(dicarboximide) (C5PDI) naphthalene-1,4:5,8-tetracarboxydianhydride (NDA), charge transfer (CT) excitons Cor•+-C5PDI•–, Pyr•+-C5PDI•–, Cor•+-NDA•–, Pyr•+-NDA•– <300 fs, while exciton τ = 125, 106, 484, 958 ps, respectively. TDDFT calculations SOCT-ISC rates correlate with delocalization CT state. In addition, time-resolved EPR spectroscopy shows Cor•+-C5PDI•– Pyr•+-C5PDI•– recombine to localized 3*C5PDI zero-field splittings |D| 1170 1250 MHz, contrast, Cor•+-NDA•– give only 1240 690 respectively, compared NDA (2091 MHz), lowest energy exciton, indicating Cor-NDA Pyr-NDA have character. These impacts both as well character resultant states.

Язык: Английский

---

Excimer evolution hampers symmetry-broken charge-separated states

Chemical Science, Год журнала: 2022, Номер 13(36), С. 10824 - 10835

Опубликована: Янв. 1, 2022

Achieving long-lived symmetry-broken charge-separated states in chromophoric assemblies is quintessential for enhanced performance of artificial photosynthetic mimics. However, the occurrence energy trap hinders exciton and charge transport across photovoltaic devices, diminishing power conversion efficiency. Herein, we demonstrate unprecedented excimer formation relaxed excited-state geometry bichromophoric systems impeding lifetime states. Core-annulated perylenediimide dimers (SC-SPDI2 SC-NPDI2) prefer a near-orthogonal arrangement ground state π-stacked foldamer structure excited state. The prospect an excimer-like foldameric SC-SPDI2 SC-NPDI2 has been rationalized by fragment-based analysis temperature-dependent photoluminescence measurements. Effective electronic coupling matrix elements Franck-Condon facilitate solvation-assisted ultrafast symmetry-breaking charge-separation (SB-CS) high dielectric environment, contrast to unrelaxed (Ex*) low environment. Subsequently, SB-CS dissociates into undesired (Ex) due configuration mixing Frenkel (FE) structure, downgrading efficacy decay rate constant FE (kFE→SB-CS) polar solvents 8-17 fold faster than that direct Ex* (kFE→Ex*) non-polar solvent (kFE→SB-CS≫kFE→Ex*), characterized femtosecond transient absorption (fsTA) spectroscopy. present investigation establishes impact detrimental on persistence offers requisite conformational rigidity as one potential design principles developing advanced molecular photovoltaics.

Язык: Английский

---

Symmetry-Breaking Charge Separation Mediated Triplet Population in a Perylenediimide Trimer at the Single-Molecule Level

The Journal of Physical Chemistry Letters, Год журнала: 2024, Номер 15(22), С. 5896 - 5904

Опубликована: Май 28, 2024

Herein, we demonstrate triplet excited-state population in a conformationally rigid perylenediimide trimer (PDI-T) via intramolecular symmetry-breaking charge separation (SB-CS) at the single-molecule level. The fluorescence intensity trajectories of PDI-T nonpolar polystyrene matrix (ε = 2.60) exhibit prolonged with infrequent dark states, representing and/or transfer states. In contrast, poly(vinyl alcohol) 7.80), erratic blinking dynamics resulting low photon counts were observed, corroborating feasibility polar environment. agreement measurements, transient absorption spectroscopy reveals ultrafast SB-CS (τCS < 5 ps) tetrahydrofuran 7.58) and acetone 20.70), through recombination. current investigation shows utility weakly coupled molecular constructs controlling generation for potential applications optoelectronic devices.

Язык: Английский

---

Perylene Diimide-Fused Dithiophenepyrroles with Different End Groups as Acceptors for Organic Photovoltaics

ACS Applied Materials & Interfaces, Год журнала: 2022, Номер 14(33), С. 37990 - 38003

Опубликована: Июль 29, 2022

In this study, we synthesized four new A–DA′D–A acceptors (where A and D represent acceptor donor chemical units) incorporating perylene diimide units (A′) as their core structures presenting various modes of halogenation substitution the functional groups at end (A). these acceptors, by fusing dithiophenepyrrole (DTP) moieties (D) to helical dimer (hPDI) form fused-hPDI (FhPDI) cores, could increase D/A′ oscillator strength in cores and, thus, intensity intramolecular charge transfer (ICT), thereby enhancing absorption bands. With different group units─IC2F, IC2Cl, IO2F, IO2Cl─tested, each molecules exhibited optical characteristics. Among all systems, organic photovoltaic device polymer PCE10 blended with FhPDI-IC2F (1:1.1 wt %) had highest power conversion efficiency (PCE) 9.0%; optimal PCEs PCE10:FhPDI-IO2F, PCE10:FhPDI-IO2Cl, PCE10:FhPDI-IC2Cl devices were 5.2, 4.7, 7.7%, respectively. The relatively high PCE PCE10:FhPDI-IC2F resulted primarily from higher coefficients acceptor, lower energy loss, more efficient transfer; system experienced a degree geminate recombination─as result improved delocalization π-electrons along unit─relative that other three systems. Thus, altering multichromophoric PDI can PDI-derived materials might also be pathway for creation valuable fused-ring derivatives.

Язык: Английский

---

Ultrafast Charge Separation Driven by Torsional Motion in Orthogonal Boron Dipyrromethene Dimer

The Journal of Physical Chemistry Letters, Год журнала: 2023, Номер 14(3), С. 702 - 708

Опубликована: Янв. 16, 2023

In this work, the photoinduced charge separation (CS) via symmetry breaking in an orthogonal meso-β-linked boron dipyrromethene (BODIPY) dimer was investigated by polarized transient absorption spectroscopy. The time constant about 0.76 ps of CS reaction determined dimethyl sulfoxide is much faster than solvation dynamics. observed anisotropy BODIPY anion band implies that both hole and electron transfers occur with similar probabilities. bidirectional transfer processes suggest locally excited state weakly coupled to polar solvent, excited-state structural relaxation within monomeric unit rather limited. combination electronic excitation analysis based on time-dependent density-functional theory calculations, we deduced enabled torsional motion associated covalently connected units, promoting coupling, irrelevant dynamic solvent relaxation.

Язык: Английский

---