Intramolecular Charge‐Transfer Dopants Enable Isolated Triplet Excitons as Spin Qutrits in a Single Crystal

Angewandte Chemie · 2026-03-09

ABSTRACT Organic molecular crystals enable spin alignment of triplet excitons over macroscopic distances, offering a molecular route to solid‐state quantum technologies. In typical crystals, however, dense packing promotes spin decoherence through dipolar coupling and exciton hopping. Although dilution doping can mitigate these effects, reported examples remain scarce because dopants must satisfy stringent structural and energetic constraints. Here, we broaden the design space for doped organic crystals by introducing a strategy that employs a host‐derived dopant with intramolecular charge‐transfer (ICT) character that maintains structural compatibility with the host lattice, while its ICT character lowers the triplet energy to localize triplet excitons. Ultrafast transient absorption spectroscopy confirms triplet formation, while time‐resolved electron paramagnetic resonance (TREPR) spectroscopy reveals that these oriented triplets possess selectively addressable spin sublevel transitions. Additionally, pulse‐EPR measurements yield a phase memory time ( T m ) of 7.1 µs at 10 K and 3.5 µs at 85 K, enabled by reduced electron‐electron dipolar coupling and suppressed exciton hopping. Temperature‐dependent studies further show that coherence is ultimately limited by nuclear spin flip–flops at low temperatures and spin‐phonon coupling at higher temperatures. These findings demonstrate that ordered triplet excitons produced by an ICT dopant in single crystals promote spin coherence at elevated temperatures.

Molecular Diradical Spin Qubits in a Crystalline Host as a Platform for Quantum Sensing

ChemRxiv · 2026-01-06 · 1 citations

Doping a luminescent tris(2,4,6-trichlorophenyl)methyl diradical m(TTM)2 into a host crystal of its diamagnetic precursor m(HTTM)2 creates a molecular color center with enhanced optical-spin interface properties important for quantum sensing. Optical polarization of the |T0⟩ sublevel of the diradical triplet ground state is achieved by spin-selective intersystem crossing from the |T+⟩ and |T-⟩sublevels of the triplet excited state at ambient and cryogenic temperatures. Coherent spin control of m(TTM)2 doped into m(HTTM)2 using pulsed optically detected magnetic resonance (ODMR) spectroscopy results in a ten-fold improvement in ODMR contrast over that observed for randomly ordered m(TTM)2 using continuous-wave ODMR The diradical doped crystals achieve spin coherence times of 2.8, 3.4, and 7.4 s at 294 K, 85 K, and 5 K, respectively. The diradical photoluminescence is sensitive to weak applied magnetic fields independent of temperature, excitation wavelength and dopant concentration, providing a promising pathway towards robust quantum sensing of anisotropic magnetic fields under ambient conditions.

Chirality-Induced Spin Selectivity in an Achiral Electron Donor–Acceptor Molecule Doped into a Cholesteric Liquid Crystal

Journal of the American Chemical Society · 2026-03-31

Chirality-induced spin selectivity (CISS) enables control over radical pair spin dynamics for applications in quantum information science (QIS). In this study, we show that this control can be achieved through supramolecular chirality transfer, rather than relying on the intrinsic molecular chirality of the molecule used to generate the radical pair. We investigate how doping an achiral donor-bridge-acceptor (D-B-A) molecule into a cholesteric liquid crystal affects the spin dynamics of a spin-correlated radical pair (D•+-B-A•-, SCRP) formed by photoinitiated, subnanosecond, two-step charge separation, where D = p-methoxyaniline (MeOAn), B = 4-(N-piperidinyl)naphthalene-1,8-dicarboximide (ANI), and A = naphthalene-1,8:4,5-bis(dicarboximide) (NDI), compound 1. The cholesteric phase of 4-cyano-4′-n-pentylbiphenyl (5CB) was prepared by the addition of the chiral dopant (R)-2-octyl 4-[4-(hexyloxy)benzoyloxy]benzoate (R811) or its enantiomer (S811). Compound 1 was then doped into these mixtures to form (1/5CB/R811) and (1/5CB/S811). Circular dichroism spectra indicate that chirality transfer occurs from the chiral medium to 1. Time-resolved electron paramagnetic resonance spectroscopy at 85 K was used to observe the SCRP resulting from photoexcitation of B in 1 aligned in 5CB/R811 and 5CB/S811, as well as in 5CB lacking the chiral dopant. The resulting spectra reveal distinct line shape changes indicative of a strong CISS contribution (>83%) to the spin dynamics of D•+-B-A•- formation in the cholesteric phase of 5CB/R811 and 5CB/S811. These results demonstrate that CISS can be effectively induced by supramolecular chirality transfer in SCRPs that lack intrinsic molecular chirality; thus expanding the potential use of CISS for QIS applications.

Symmetry-Enabled Optical Spin Initialization of Luminescent Organic Radical Doublet States

ChemRxiv · 2026-03-02

Optical-spin interfaces that enable the photoinitialization, coherent microwave manipulation, and optical readout of ground state spins are promising for emerging quantum technologies. Molecular optical-spin interfaces offer advantages over solid-state defects through synthetic control of their optical and spin properties. Optical initialization of these systems relies on spin-selective intersystem crossing between electronic states of different spin multiplicity. In this work, we demonstrate experimentally and theoretically that coherent excited-state evolutions enable optical spin polarization of luminescent tris(2,4,6-trichlorophenyl)methyl (TTM) monoradicals without the need for intersystem crossing. Inspired by the alignment-to-orientation conversion (AOC) phenomenon in atomic physics, we find that the doubly degenerate first excited state of 𝐷symmetric TTM possesses a pseudo-orbital angular momentum that couples to the electron spin through in-state spin-orbit coupling, resulting in spin-dependent excited-state dynamics following photoexcitation. These coherent dynamics produce differential decay pathways to the ground state that generate persistent spin polarization in an applied magnetic field. Time-resolved electron paramagnetic resonance spectroscopy confirms photoinduced ground-state spin polarization in TTM and its symmetry-preserving derivatives, while lower-symmetry analogues exhibit no polarization, consistent with a loss of pseudo-orbital angular momentum. Quantum dynamics simulations predict spin-dependent luminescence dynamics and circularly polarized emission from photoinitialized TTM, providing viable pathways for future optical spin readout. These results establish a fundamentally new paradigm for optical spin initialization in organic radicals based on symmetry-enabled coherent dynamics and lay the foundation for establishing optical-spin interfaces in organic monoradicals.

Detecting chirality-induced spin selectivity in chromophore-linked DNA hairpins using photogenerated radical pairs. Open data set

Zenodo (CERN European Organization for Nuclear Research) · 2026-01-23

Data supporting Figures 2, 3, 4, 5 and 6 of the related publication.

Detecting chirality-induced spin selectivity in chromophore-linked DNA hairpins using photogenerated radical pairs. Open data set

Zenodo (CERN European Organization for Nuclear Research) · 2026-01-23

Data supporting Figures 2, 3, 4, 5 and 6 of the related publication.

CCDC 2504916: Experimental Crystal Structure Determination

Open MIND · 2026-02-02

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Intramolecular Charge‐Transfer Dopants Enable Isolated Triplet Excitons as Spin Qutrits in a Single Crystal

Angewandte Chemie International Edition · 2026-03-09

ABSTRACT Organic molecular crystals enable spin alignment of triplet excitons over macroscopic distances, offering a molecular route to solid‐state quantum technologies. In typical crystals, however, dense packing promotes spin decoherence through dipolar coupling and exciton hopping. Although dilution doping can mitigate these effects, reported examples remain scarce because dopants must satisfy stringent structural and energetic constraints. Here, we broaden the design space for doped organic crystals by introducing a strategy that employs a host‐derived dopant with intramolecular charge‐transfer (ICT) character that maintains structural compatibility with the host lattice, while its ICT character lowers the triplet energy to localize triplet excitons. Ultrafast transient absorption spectroscopy confirms triplet formation, while time‐resolved electron paramagnetic resonance (TREPR) spectroscopy reveals that these oriented triplets possess selectively addressable spin sublevel transitions. Additionally, pulse‐EPR measurements yield a phase memory time ( T m ) of 7.1 µs at 10 K and 3.5 µs at 85 K, enabled by reduced electron‐electron dipolar coupling and suppressed exciton hopping. Temperature‐dependent studies further show that coherence is ultimately limited by nuclear spin flip–flops at low temperatures and spin‐phonon coupling at higher temperatures. These findings demonstrate that ordered triplet excitons produced by an ICT dopant in single crystals promote spin coherence at elevated temperatures.

High-Fidelity quantum teleportation mediated by hole transfer in an acceptor–donor–radical molecular triad

Nature Communications · 2026-03-14

Quantum teleportation transfers quantum states between nodes in a quantum network through entanglement distribution and subsequent Bell-state measurements. Here, we report electron spin teleportation through an unexplored hole-transfer mechanism within an ensemble of covalently linked acceptor–donor–stable radical (A–D–R•) molecules. Photoexcitation of A after spin state preparation on R• results in ultrafast hole transfer to produce an entangled pair 1(A•−–D•+). A subsequent spontaneous hole transfer 1(A•−–1[D•+)–R•] → A•−–D–R+ constitutes a Bell-state measurement, projecting the spin state initially prepared on R• onto A•−. Quantum state tomography using pulse electron paramagnetic resonance spectroscopy reveals successful teleportation. A fidelity of 98% is achieved due to high entanglement purity, small Larmor frequency mismatch between sender and receiver radicals, as well as minimized delay between state preparation and teleportation. These results represent an important step in developing molecular materials that can transfer information coherently between nanoscale quantum devices. Recent advances with molecular qubits have enabled the implementation of spin quantum teleportation (QT), albeit with limited fidelity & applicability. Here, the authors demonstrate optimal QT of spin states via hole transfer in covalently linked acceptor-donor-radical molecules, opening towards rational design of molecular materials for coherent information transfer.

Identifying Electrolyte Reduction Intermediates in Lithium Metal Batteries with Spin Trapping

ChemRxiv · 2026-02-18 · 1 citations

Despite promising developments in liquid electrolyte engineering for lithium metal batteries, solid electrolyte interphase (SEI) formation mechanisms from electrolyte components remain challenging to study. Here we establish an approach employing spin trapping to identify radical intermediates formed during electrolyte reduction. We use electron paramagnetic resonance spectroscopy to identify three distinct radical intermediates formed during fluoroethylene carbonate reduction that confirm a ring-opening mechanism. Our spin trapping approach further enables confirmation of radical identity with liquid-chromatography mass spectrometry and nuclear magnetic resonance spectroscopy. The resulting SEI formed in the spin trapped system is investigated with titration and spectroscopic techniques to observe how stunting organic SEI formation reduces SEI stability and increases anion decomposition. Overall, this is the first time radical intermediates in battery interphase formation reactions have been directly characterized, affording insight into the complex mechanisms of electrolyte reduction and establishing a new approach for studying SEI formation and function.