Important Elements of Spin-Exciton and Magnon-Exciton Coupling.

The recent discovery of spin-exciton and magnon-exciton coupling in a layered antiferromagnetic semiconductor, CrSBr, is both fundamentally intriguing and technologically significant. This discovery unveils a unique capability to optically access and manipulate spin information using excitons, opening doors to applications in quantum interconnects, quantum photonics, and opto-spintronics. Despite their remarkable potential, materials exhibiting spin-exciton and magnon-exciton coupling remain limited.

Sex differences in the structural rich-club connectivity in patients with Alzheimer's disease.

Background And Objectives: Alzheimer's disease (AD) is more prevalent in women than in men; however, there is a discrepancy in research on sex differences in AD. The human brain is a large-scale network with hub regions forming a central core, the rich-club, which is vital to cognitive functions. However, it is unknown whether alterations in the rich-clubs in AD differ between men and women.

Tunable interaction between excitons and hybridized magnons in a layered semiconductor.

The interaction between distinct excitations in solids is of both fundamental interest and technological importance. One such interaction is the coupling between an exciton, a Coulomb bound electron-hole pair, and a magnon, a collective spin excitation. The recent emergence of van der Waals magnetic semiconductors provides a platform to explore these exciton-magnon interactions and their fundamental properties, such as strong correlation, as well as their photospintronic and quantum transduction applications.

Exciton-coupled coherent magnons in a 2D semiconductor.

The recent discoveries of two-dimensional (2D) magnets and their stacking into van der Waals structures have expanded the horizon of 2D phenomena. One exciting application is to exploit coherent magnons as energy-efficient information carriers in spintronics and magnonics or as interconnects in hybrid quantum systems. A particular opportunity arises when a 2D magnet is also a semiconductor, as reported recently for CrSBr (refs.

Spin Waves and Magnetic Exchange Hamiltonian in CrSBr.

CrSBr is an air-stable two-dimensional (2D) van der Waals semiconducting magnet with great technological promise, but its atomic-scale magnetic interactions-crucial information for high-frequency switching-are poorly understood. An experimental study is presented to determine the CrSBr magnetic exchange Hamiltonian and bulk magnon spectrum. The A-type antiferromagnetic order using single crystal neutron diffraction is confirmed here.

Temperature Tuning of Coherent Mixing between States Driving Singlet Fission in a Spiro-Fused Terrylenediimide Dimer.

The excited-state dynamics of a spiro-fused terrylene-3,4:11,12-bis(dicarboximide) (TDI) dimer () in toluene and 2-methyltetrahydrofuran (mTHF) were investigated as a function of temperature using femtosecond- and nanosecond-transient absorption spectroscopy, as well as two-dimensional electronic spectroscopy. The spiro conjugation and the corresponding geometry of this compound guarantee a short intermonomer distance along with a partial orbital overlap between the orthogonal TDI π-electron systems, providing electronic coupling between the TDIs. Photoexcitation of in toluene, a low dielectric solvent, at 295 K, results in the ultrafast formation of a state composed of a coherent mixture of singlet (SS), multiexciton (TT), and charge-transfer (CT) electronic characters.

Singlet fission in core-linked terrylenediimide dimers.

We have studied two regioisomeric terrylenediimide (TDI) dimers in which the 1-positions of two TDIs are linked via 1,3- or 1,4-phenylene spacers, mTDI and pTDI, respectively. The nature and the dynamics of the multiexciton state are tuned by altering the through-bond electronic couplings in the ground and excited states and by changing the solvent environment. Our results show that controlling the electronic coupling between the two chromophores by an appropriate choice of linker can result in independent triplet state formation, even though the initial correlated triplet pair state is confined to a dimer.

Balancing Charge Transfer and Frenkel Exciton Coupling Leads to Excimer Formation in Molecular Dimers: Implications for Singlet Fission.

Photoexcitation of molecular chromophore aggregates can form excimer states that play a significant role in photophysical processes such as charge and energy transfer as well as singlet fission. An excimer state is commonly defined as a superposition of Frenkel exciton and charge transfer states. In this work, we investigate the dynamics of excimer formation and decay in π-stacked 9,10-bis(phenylethynyl)anthracene (BPEA) covalent dimers appended to a xanthene spacer, where the electronic coupling between the two BPEA molecules is adjusted by changing their longitudinal molecular slip distances.

π-Extended Donor-Acceptor Porphyrins and Metalloporphyrins for Antimicrobial Photodynamic Inactivation.

Free base, zinc and palladium π-extended porphyrins containing fused naphthalenediamide units were employed as photosensitizers in antimicrobial photodynamic therapy (aPDT). Their efficacy, assessed by photophysical and in vitro photobiological studies on Gram-positive bacteria, was found to depend on metal coordination, showing a dramatic enhancement of photosensitizing activity for the palladium complex.

Controlling the structure and photophysics of fluorophore dimers using multiple cucurbit[8]uril clampings.

A modular strategy has been employed to develop a new class of fluorescent molecules, which generates discrete, dimeric stacked fluorophores upon complexation with multiple cucurbit[8]uril macrocycles. The multiple constraints result in a "static" complex (remaining as a single entity for more than 30 ms) and facilitate fluorophore coupling in the ground state, showing a significant bathochromic shift in absorption and emission. This modular design is surprisingly applicable and flexible and has been validated through an investigation of nine different fluorophore cores ranging in size, shape, and geometric variation of their clamping modules.

Combining Intra- and Intermolecular Charge Transfer with Polycationic Cyclophanes To Design 2D Tessellations.

A series of donor-acceptor (D-A) naphthalene-viologen-based cyclophanes of different shapes, sizes, and symmetries have been synthesized and characterized. Solution optical studies on these cyclophanes reveal the existence of photoinduced intramolecular charge transfer (CT) at 465 nm from naphthalene (D) to viologen (A) units, resulting in a conformational change in the viologen units and the emergence of an emission at 540 nm. The D-A cyclophanes with box-like and hexagon-like shapes offer an opportunity to control the arrangement within 2D layers where D-A interactions direct the superstructures.

Substituent effects on energetics and crystal morphology modulate singlet fission in 9,10-bis(phenylethynyl)anthracenes.

Singlet fission (SF) converts a singlet exciton into two triplet excitons in two or more electronically coupled organic chromophores, which may then be used to increase solar cell efficiency. Many known SF chromophores are unsuitable for device applications due to chemical instability or low triplet state energies. The results described here show that efficient SF occurs in derivatives of 9,10-bis(phenylethynyl)anthracene (BPEA), which is a highly robust and tunable chromophore.

Quintet-triplet mixing determines the fate of the multiexciton state produced by singlet fission in a terrylenediimide dimer at room temperature.

Singlet fission (SF) is a photophysical process in which one of two adjacent organic molecules absorbs a single photon, resulting in rapid formation of a correlated triplet pair (TT) state whose spin dynamics influence the successful generation of uncorrelated triplets (T). Femtosecond transient visible and near-infrared absorption spectroscopy of a linear terrylene-3,4:11,12-bis(dicarboximide) dimer (TDI), in which the two TDI molecules are directly linked at one of their imide positions, reveals ultrafast formation of the (TT) state. The spin dynamics of the (TT) state and the processes leading to uncoupled triplets (T) were studied at room temperature for TDI aligned in 4-cyano-4'-pentylbiphenyl (5CB), a nematic liquid crystal.

Varying the Interpentacene Electronic Coupling to Tune Singlet Fission.

We have designed and used four different spacers, denoted A-D, to connect two pentacenes and to probe the impact of intramolecular forces on the modulation of pentacene-pentacene interactions and, in turn, on the key steps in singlet fission (SF), that is, the (SS)-to-(TT) as well as (TT)-to-(TT) transitions by means of transient absorption and electron paramagnetic resonance measurements. In terms of the (SS)-to-(TT) transition, a superexchange mechanism, that is, coupling to a higher-lying CT state to generate a virtual intermediate, enables rapid SF in A-D. Sizeable electronic coupling in A and B opens, on one hand, an additional pathway, that is, the population of a real intermediate, and changes, on the other hand, the mechanism to that of hopping.

Dysautonomia is associated with structural and functional alterations in Parkinson disease.

Objective: To investigate whether the presence of autonomic dysfunction is associated with white matter and functional connectivities and the level of cognitive performance in patients with de novo Parkinson disease (PD).

Methods: Seventy-five patients with de novo PD underwent a comprehensive autonomic function test and were classified into 2 groups according to the Composite Autonomic Severity Score (CASS; 30 with moderate to severe autonomic dysfunction [CASS 4-10, PD-AUT+] and 45 without significant autonomic dysfunction [CASS 0-3, PD-AUT-]). Network-based statistics and a graph theoretical analysis were performed to assess the interregional white matter connectivity using diffusion tensor imaging.

Singlet Fission in 9,10-Bis(phenylethynyl)anthracene Thin Films.

Singlet fission (SF) in two or more electronically coupled organic chromophores converts a high-energy singlet exciton into two low-energy triplet excitons, which can be used to increase solar cell efficiency. Many known SF chromophores are unsuitable for device applications due to chemical instability and low triplet state energies. The results described here show that efficient SF occurs in polycrystalline thin films of 9,10-bis(phenylethynyl)anthracene (BPEA), a commercial dye that has singlet and triplet energies of 2.

Fully Conjugated [4]Chrysaorene. Redox-Coupled Anion Binding in a Tetraradicaloid Macrocycle.

[4]Chrysaorene, a fully conjugated carbocyclic coronoid, is shown to be a low-bandgap π-conjugated system with a distinct open-shell character. The system shows good chemical stability and can be oxidized to well-defined radical cation and dication states. The cavity of [4]chrysaorene acts as an anion receptor toward halide ions with a particular selectivity toward iodides ( K = 207 ± 6 M).

Singlet Fission in Covalent Terrylenediimide Dimers: Probing the Nature of the Multiexciton State Using Femtosecond Mid-Infrared Spectroscopy.

Singlet fission (SF) is a spin-allowed process that involves absorption of a photon by two electronically interacting chromophores to produce a singlet exciton state, (SS), followed by rapid formation of two triplet excitons if the singlet exciton energy is about twice that of the triplet exciton. The initial formation of the multiexciton correlated triplet pair state, (TT), is thought to involve the agency of charge transfer (CT) states. The dynamics of these electronic states were studied in a covalent slip-stacked terrylene-3,4:11,12-bis(dicarboximide) (TDI) dimer in which the conformation of two TDI molecules is determined by a xanthene spacer (XanTDI).

Transparent Metal-Organic Framework/Polymer Mixed Matrix Membranes as Water Vapor Barriers.

Preventing the permeation of reactive molecules into electronic devices or photovoltaic modules is of great importance to ensure their life span and reliability. This work is focused on the formation of highly functioning barrier films based on nanocrystals (NCs) of a water-scavenging metal-organic framework (MOF) and a hydrophobic cyclic olefin copolymer (COC) to overcome the current limitations. Water vapor transmission rates (WVTR) of the films reveal a 10-fold enhancement in the WVTR compared to the substrate while maintaining outstanding transparency over most of the visible and solar spectrum, a necessary condition for integration with optoelectronic devices.