Stable single-site organonickel catalyst preferentially hydrogenolyses branched polyolefin C-C bonds.

Current methods of processing accumulated polyolefin waste typically require harsh conditions, precious metals or high metal loadings to achieve appreciable activities. Here we examined supported, single-site organonickel catalysts for polyolefin upcycling. Chemisorption of Ni(COD) (COD, 1,5-cyclooctadiene) onto Brønsted acidic sulfated alumina (AlS) yields a highly electrophilic Ni(I) precatalyst, AlS/Ni(COD), which is converted under H to the active AlS/NiH catalyst.

Strong NIR II Chiroptical Response and Magnetic Anisotropy via Modular Installation of Chiral Capping Ligands on a Light-Emitting Diradicaloid Scaffold.

Low-energy molecular lumiphores have seen increased interest due to potential imaging and communications applications. Specifically, molecules that emit in the near-infrared (NIR, 700-1700 nm) or telecom (∼1260-1625 nm) regions, where attenuation is minimized in biological tissue and optical fibers, respectively, can drastically improve image resolution and depth penetration; however, bright low-energy emission is rare due to exponentially decreasing quantum yields in this region. Chiral molecules exhibiting strong NIR or telecom absorption/emission would be of particular interest due to advanced security and spintronics applications, but these compounds remain scarce and are currently restricted to lanthanide or nanoparticle-based systems.

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

Chirality-induced spin selectivity (CISS) results in spin polarization of electrons transmitted through chiral molecules and materials. Since CISS results in spin polarization even at room temperature, it affords the possibility of using it to develop quantum technologies that can operate under ambient conditions. We have shown previously that photo-driven hole transfer within DNA hairpins provides a facile route to generate spin-correlated radical pairs (SCRPs).

Effect of Chirality on Ultrafast Triplet Exciton Formation in Electron Donor-Acceptor Cocrystals.

Triplet excitons formed in organic donor-acceptor cocrystals are desirable for solar energy, optoelectronic, and quantum information applications, and recent work on chirality-induced spin selectivity (CISS) provides an indication that chirality may influence triplet exciton formation in potentially useful ways. Here, we investigate the effect of a chiral electron acceptor on the charge transfer dynamics and triplet exciton formation in a series of donor-acceptor cocrystals, each having a coronene donor paired with one of three acceptors: achiral ,-bis(3'-pentyl)perylene-(3,4:9,10)-bis(dicarboximide) and two enantiomeric chiral PDIs, ,'-bis(()- or ()-3'--butyl)perylene-(3,4:9,10)-bis(dicarboximide). X-ray diffraction of the three cocrystals confirms that they have nearly identical structures.

Optically Detected Coherent Spin Control of Organic Molecular Color Center Qubits.

Molecular optical-spin interfaces are emerging as promising alternatives to solid-state defects, such as diamond nitrogen vacancy centers for quantum information science applications. In this work, we report a new organic molecular color center consisting of two luminescent tris(2,4,6-trichlorophenyl)methyl () radicals connected at the 2,6-positions of a toluene bridge. Optical polarization of the |T⟩ sublevel of the triplet ground state is achieved by spin-selective excited-state intersystem crossing from the |T⟩ and |T⟩ sublevels of the triplet excited state.

Molecular Cocrystal Packing Suppresses Hopping-Driven Decoherence of Excitonic Spin Qubits.

Molecular excitonic spins have garnered significant interest for quantum technologies because they can be initialized into addressable, multilevel quantum states through spin-selective intersystem crossing or singlet fission. However, excitonic spin coherence is difficult to maintain above liquid helium temperatures due to typical crystal packings, which promote decoherence through exciton hopping between magnetically inequivalent sites. Here, we engineer donor-acceptor cocrystals where molecular packing in isolated π-stacks of magnetically equivalent molecules suppresses hopping-induced decoherence.

Electronically Tunable Low-Valent Uranium Metallacarboranes.

Uranium metallocenes have played a pivotal role in advancing the understanding of low-valent uranium chemistry since the inception of this field, and they still find continued use today. Functionalization strategies for cyclopentadienyl (Cp) ligands used in uranium metallocenes have predominately focused on modifying the steric properties of the ligand through the incorporation of alkyl or silyl groups, which offer limited control over the electronic properties. Moreover, due to the flat, two-dimensional nature of Cp, functional groups will affect the coordination geometry of the uranium metallocene and can potentially present challenges in decoupling steric and electronic effects.

Triphenylphosphine Oxide-Derived Anolyte for Application in Nonaqueous Redox Flow Battery.

Recent advances in redox flow batteries have made them a viable option for grid-scale energy storage, however they exhibit low energy density. One way to boost energy density is by increasing the cell potential using a nonaqueous system. Molecular engineering has proven to be an effective strategy to develop redox-active compounds with extreme potentials but these are usually challenged by resource sustainability of the newly developed redox materials.

Room-Temperature Optical Spin Polarization of an Electron Spin Qudit in a Vanadyl-Free Base Porphyrin Dimer.

Photoexcited organic chromophores appended to molecular qubits can serve as a source of spin initialization or multilevel qudit generation for quantum information applications. So far, this approach has been primarily investigated in chromophore-stable radical systems. Here, we extend this concept to a linked oxovanadium(IV) porphyrin-free-base porphyrin dimer.

Enhancing Photogenerated Radical Pair Properties in Donor-Chromophore-Acceptor Systems for Quantum Information Applications.

We report on new donor-chromophore-acceptor triads and where the BDX donor is 2,2,6,6-tetramethylbenzo[1,2-;4,5-]bis[1,3]dioxole, the ANI chromophore is 4-(-piperidinyl)naphthalene-1,8-dicarboximide, the NDI acceptor is naphthalene-1,8:4,5-bis(dicarboximide), and xy is a 2,5-xylyl spacer. The results on these compounds are compared to the analogous derivatives having a -methoxyaniline (MeOAn) as the donor. BDX has no nitrogen atoms and only a single hydrogen atom coupled to its unpaired electron spin, and therefore has significantly decreased hyperfine interactions compared to MeOAn.

Luminescent Organic Triplet Diradicals as Optically Addressable Molecular Qubits.

Optical-spin interfaces that enable the photoinitialization, coherent microwave manipulation, and optical read-out of ground state spins have been studied extensively in solid-state defects such as diamond nitrogen vacancy (NV) centers and are promising for quantum information science applications. Molecular quantum bits (qubits) offer many advantages over solid-state spin centers through synthetic control of their optical and spin properties and their scalability into well-defined multiqubit arrays. In this work, we report an optical-spin interface in an organic molecular qubit consisting of two luminescent tris(2,4,6-trichlorophenyl)methyl (TTM) radicals connected via the -positions of a phenyl linker.

Identifying Sources of Entanglement Loss in Photodriven Molecular Electron Spin Teleportation.

We report on an electron donor-electron acceptor-stable radical (D-A-R) molecule in which an electron spin state first prepared on R is followed by photogeneration of an entangled singlet [D-A] spin pair to produce D-A-R. Since the A and R spins within D-A-R are uncorrelated, spin teleportation from R to D occurs with a maximal 25% efficiency only for the singlet pair (A-R) by spin-allowed electron transfer from A to R. However, since [D-A] is sufficiently long-lived, coherent spin mixing involving the unreactive (A-R) population affects entanglement and teleportation within D-A-R.

A Geometrically Flexible Three-Dimensional Nanocarbon.

The development of architecturally unique molecular nanocarbons by bottom-up organic synthesis is essential for accessing functional organic materials awaiting technological developments in fields such as energy, electronics, and biomedicine. Herein, we describe the design and synthesis of a triptycene-based three-dimensional (3D) nanocarbon, , with geometrical flexibility on account of its three peripheral π-panels being capable of interconverting between two curved conformations. An effective through-space electronic communication among the three π-panels of has been observed in its monocationic radical form, which exhibits an extensively delocalized spin density over the entire 3D π-system as revealed by electron paramagnetic resonance and UV-vis-NIR spectroscopies.

Oriented Triplet Excitons as Long-Lived Electron Spin Qutrits in a Molecular Donor-Acceptor Single Cocrystal.

The photogeneration of multiple unpaired electron spins within molecules is a promising route to applications in quantum information science because they can be initialized into well-defined, multilevel quantum states ( > 1/2) and reproducibly fabricated by chemical synthesis. However, coherent manipulation of these spin states is difficult to realize in typical molecular systems due to the lack of selective addressability and short coherence times of the spin transitions. Here, these challenges are addressed by using donor-acceptor single cocrystals composed of pyrene and naphthalene dianhydride to host spatially oriented triplet excitons, which exhibit promising photogenerated qutrit properties.

Enhancing Coherence Times of Chromophore-Radical Molecular Qubits and Qudits by Rational Design.

An important criterion for quantum operations is long qubit coherence times. To elucidate the influence of molecular structure on the coherence times of molecular spin qubits and qudits, a series of molecules featuring perylenediimide (PDI) chromophores covalently linked to stable nitroxide radicals were synthesized and investigated by pulse electron paramagnetic resonance spectroscopy. Photoexcitation of PDI in these systems creates an excited quartet state () followed by a spin-polarized doublet ground state (), which hold promise as spin qudits and qubits, respectively.

Direct observation of chirality-induced spin selectivity in electron donor-acceptor molecules.

The role of chirality in determining the spin dynamics of photoinduced electron transfer in donor-acceptor molecules remains an open question. Although chirality-induced spin selectivity (CISS) has been demonstrated in molecules bound to substrates, experimental information about whether this process influences spin dynamics in the molecules themselves is lacking. Here we used time-resolved electron paramagnetic resonance spectroscopy to show that CISS strongly influences the spin dynamics of isolated covalent donor-chiral bridge-acceptor (D-Bχ-A) molecules in which selective photoexcitation of D is followed by two rapid, sequential electron-transfer events to yield D-Bχ-A.

Spin-Frustrated Trisradical Trication of PrismCage.

Organic trisradicals featuring threefold symmetry have attracted significant interest because of their unique magnetic properties associated with spin frustration. Herein, we describe the synthesis and characterization of a triangular prism-shaped organic cage for which we have coined the name and its trisradical trication─. is composed of three 4,4'-bipyridinium dications and two 1,3,5-phenylene units bridged by six methylene groups.

Pulse sequences for manipulating the spin states of molecular radical-pair-based electron spin qubit systems for quantum information applications.

Molecular qubits are an emerging platform in quantum information science due to the unmatched structural control that chemical design and synthesis provide compared to other leading qubit technologies. This theoretical study investigates pulse sequence protocols for spin-correlated radical pairs, which are important molecular spin qubit pair (SQP) candidates. Here, we introduce improved microwave pulse protocols for enhancing the execution times of quantum logic gates based on SQPs.

Evidence of a Uranium-Paddlewheel Node in a Catecholate-Based Metal-Organic Framework.

The interactions between uranium and non-innocent organic species are an essential component of fundamental uranium redox chemistry. However, they have seldom been explored in the context of multidimensional, porous materials. Uranium-based metal-organic frameworks (MOFs) offer a new angle to study these interactions, as these self-assembled species stabilize uranium species through immobilization by organic linkers within a crystalline framework, while potentially providing a method for adjusting metal oxidation state through coordination of non-innocent linkers.

Quantum Gate Operations on a Spectrally Addressable Photogenerated Molecular Electron Spin-Qubit Pair.

Sub-nanosecond photodriven electron transfer from a molecular donor to an acceptor can be used to generate a radical pair (RP) having two entangled electron spins in a well-defined pure initial singlet quantum state to serve as a spin-qubit pair (SQP). Achieving good spin-qubit addressability is challenging because many organic radical ions have large hyperfine couplings (HFCs) in addition to significant -anisotropy, which results in significant spectral overlap. Moreover, using radicals with -factors that deviate significantly from that of the free electron results in difficulty generating microwave pulses with sufficiently large bandwidths to manipulate the two spins either simultaneously or selectively as is necessary to implement the controlled-NOT (CNOT) quantum gate essential for quantum algorithms.

Computational tools for the simulation and analysis of spin-polarized EPR spectra.

The EPR spectra of paramagnetic species induced by photoexcitation typically exhibit enhanced absorptive and emissive features resulting from sublevel populations that differ from thermal equilibrium. The populations and the resulting spin polarization of the spectra are dictated by the selectivity of the photophysical process generating the observed state. Simulation of the spin-polarized EPR spectra is crucial in the characterization of both the dynamics of formation of the photoexcited state as well as its electronic and structural properties.

Long-lived electronic spin qubits in single-walled carbon nanotubes.

Electron spins in solid-state systems offer the promise of spin-based information processing devices. Single-walled carbon nanotubes (SWCNTs), an all-carbon one-dimensional material whose spin-free environment and weak spin-orbit coupling promise long spin coherence times, offer a diverse degree of freedom for extended range of functionality not available to bulk systems. A key requirement limiting spin qubit implementation in SWCNTs is disciplined confinement of isolated spins.

Optical Spin Polarization of a Narrow-Linewidth Electron-Spin Qubit in a Chromophore/Stable-Radical System.

Photoexcited organic chromophores appended to stable radicals can serve as qubit and/or qudit candidates for quantum information applications. 1,6,7,12-Tetra-(4-tert-butylphenoxy)-perylene-3,4 : 9,10-bis(dicarboximide) (tpPDI) linked to a partially deuterated α,γ-bisdiphenylene-β-phenylallyl radical (BDPA-d ) was synthesized and characterized by time-resolved optical and electron paramagnetic resonance (EPR) spectroscopies. Photoexcitation of tpPDI-BDPA-d results in ultrafast radical-enhanced intersystem crossing to produce a quartet state (Q) followed by formation of a spin-polarized doublet ground state (D ).

Optical Initialization of Molecular Qubit Spin States Using Weak Exchange Coupling to Photogenerated Fullerene Triplet States.

The ability to initialize an electron spin qubit into a well-defined state is an important criterion for quantum information applications. To achieve this goal, a chromophore photoexcited to its triplet state is used to strongly spin polarize a nearby stable radical in a series of C fullerene derivatives containing a covalently linked α,γ-bisdiphenylene-β-phenylallyl (BDPA) radical. Selective photoexcitation of C results in up to 20-fold enhancement of the BDPA spin polarization observed by pulse electron paramagnetic resonance spectroscopy at room temperature.