Matthew D. Krzyaniak

Photodriven symmetry-breaking charge separation (SB-CS) has been proposed as a method for producing free charge carriers in organic electronic materials because charge separation can occur with minimal photon energy loss. The challenge in achieving this goal lies in minimizing the rapid charge recombination of the initial charge transfer (CT) exciton to permit charge diffusion away from the site at which the CT exciton is created. Here, we leverage specific crystal packing motifs elicited by hydrogen-bonding core-twisted 1,6,7,12-tetrachloroperylenediimide derivatives substituted at their imide nitrogen atoms with 2-(2-hydroxyethoxy)ethyl or 5-hydroxypentyl chains. Femtosecond transient absorption microscopy reveals that photoexcitation of these derivatives in single crystals results in subpicosecond SB-CS. The initial CT exciton then separates to give mobile charge carriers that live for over 1 ms, as determined by time-resolved microwave conductivity. This investigation shows how controlling crystal morphology and environment can generate high-energy free charge carriers following SB-CS in solid-state organic materials.

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 D₃-symmetric 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. 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.

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 that 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.

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.

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.

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.

Molecules provide a modular and chemically tunable platform for quantum information science. In recent years, significant advances have been made in enabling optical spin initialization, coherent control, and both optical and electrical readout of molecular qubits. Yet, a central challenge remains: realizing scalable architectures through the controlled and ultrafast activation of interqubit interactions. Here, we present a molecular system composed of two vanadyl porphyrin qubits bridged by a free-base porphyrin chromophore, where the qubits are magnetically independent in the ground state but become coupled upon photoexcitation. Femtosecond transient absorption and time-resolved electron paramagnetic resonance experiments, supported by DFT calculations and spectral simulations, reveal that photoexcitation induces the formation of a spin-quintet state within subpicosecond time scales. Notably, long-lived spin polarization persists up to room temperature. Theoretical modeling offers design principles for harnessing this mechanism in future applications. These results provide a proof of concept for optically controlled spin interactions in molecules, paving the way for light-activated molecular quantum gates.

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.