Temperature-dependent dynamics of endohedral fullerene Sc@C(CHPh) studied by EPR spectroscopy.

Endohedral fullerenes are promising materials for the quantum information and quantum processing due to the unique properties of the electron-nuclear spin system well isolated from the environment inside the fullerene cage. The endofullerene Sc@C(CHPh) features a strong hyperfine interaction between one electron spin 1/2 localized at the Sc dimer and two equivalent Sc nuclear spins 7/2, which yields 64 well resolved EPR transitions. We report a comprehensive analysis of the temperature dependence of the EPR spectrum of Sc@C(CHPh) dissolved in d-toluene measured in a wide temperature range above and below the melting point.

Effect of the chemical structure of a tetradentate equatorial ligand on the spin-crossover properties of the Fe (III) complexes chain structures: Electron paramagnetic resonance study.

The effect of the chemical structure of the equatorial ligand on the spin state of the Fe (III) ion in a series of 1-D chain complexes of the general formula [Fe(L)(tvp)]BPh ·nCH OH, where L = dianions of Schiff base containing a different number of aromatic groups: N,N'-ethylenebis (salicylaldimine) (salen) 1, N,N'-ethylenebis (acetylacetone)2,2'-imine (acen) 2, N,N'-ethylenebis (benzoylacetylacetone)2,2'-imine (bzacen) 3, and tvp = 1,2-di(4-pyridyl)ethylene, was studied by ultraviolet-visible (UV-vis) and electron paramagnetic resonance (EPR) methods. The values of exchange interactions, thermodynamic parameters of spin-crossover, and electronic structure features of the Fe (III) complexes were estimated from the EPR data. The substitution of a fragment of the equatorial ligand L in the series salen-acen-bzacen changes the local symmetry of the complex in the 1-D chain, thereby affecting the spin variable properties.

Dendritic Iron(III) Carbazole Complexes: Structural, Optical, and Magnetic Characteristics.

This paper focuses on the synthesis, structural characterization, and study of the optical, magnetic, and thermal properties of novel architectures combining metal ions as magnetoactive centers and photoactive blocks formed by carbazole units. For this purpose, a series of azomethine complexes of the composition [Fe(L)]X (L = 3,6-bis[(3',6'-di--butyl-9-carbazol)-9-carbazol]benzoyloxy-4-salicylidene-N'-ethyl-N-ethylenediamine, X = NO, Cl, PF) were synthesized by the reaction of metal salts with Schiff bases in a mixture of solvents. The UV-Vis absorption properties were studied in dichloromethane and rationalized via time-dependent density functional theory (DFT) calculations.

Intersystem Crossing and Triplet-State Property of Anthryl- and Carbazole-[1,12]fused Perylenebisimide Derivatives with a Twisted π-Conjugation Framework.

Heavy atom-free triplet photosensitizers (PSs) are particularly of interest concerning both fundamental photochemistry study and practical applications. However, achieving efficient intersystem crossing (ISC) in planar heavy atom-free aromatic organic compounds is challenging. Herein, we demonstrate that two perylenebisimide (PBI) derivatives with anthryl and carbazole moieties fused at the bay position, showing twisted π-conjugation frameworks and red-shifted UV-vis absorption as compared to the native PBI chromophore (by 75-1610 cm), possess efficient ISC (singlet oxygen quantum yield: Φ = 85%) and a long-lived triplet excited state (τ = 382 μs in fluid solution and τ = 4.

Chromophore Orientation-Dependent Photophysical Properties of Pyrene-Naphthalimide Compact Electron Donor-Acceptor Dyads: Electron Transfer and Intersystem Crossing.

In order to study the effect of mutual orientation of the chromophores in compact electron donor-acceptor dyads on the spin-orbit charge transfer intersystem crossing (SOCT-ISC), we prepared naphthalimide ()-pyrene () compact electron donor-acceptor dyads, in which pyrene acts as an electron donor and is an electron acceptor. The connection of the two units is at the 4-C and 3-C positions of the unit and the 1-position of the pyrene moiety for dyads and , respectively. A charge transfer absorption band was observed for both dyads in the UV-vis absorption spectra.

Enhanced Intersystem Crossing due to Resonant Energy Transfer to a Remote Spin.

A new mechanism for enhanced intersystem crossing in coupled three-spin systems consisting of a chromophore and an attached radical is proposed. It is shown that if the unpaired electron of the radical experiences spin-orbit coupling and different exchange interactions with the two unpaired electron spins of the chromophore, energy transfer from the chromophore to the radical can occur together with singlet-triplet intersystem crossing in the chromophore. The efficiency of this process increases dramatically when the electronic excitation of the radical is resonant with the S-T energy gap of the chromophore.

Influence of Spin Decoherence on the Yield of Photodriven Quantum Teleportation in Molecular Triads.

The evolution of spin coherences due to spin-selective recombination in the system with three unpaired electrons is discussed. It is shown that in the case of bidirectional kinetics, the decoherence processes can significantly change the quantum yield of the products. This enables one to discriminate between approaches that model spin-selective recombination but predict different decoherence rates.

Antimicrobial and antioxidant activity of Evernia prunastri extracts and their isolates.

Lichens are symbiotic organisms formed by a fungus and one or more photosynthetic partners which are usually alga or cyanobacterium. Their diverse and scarcely studied metabolites facilitate adaptability to extreme living conditions. We investigated Evernia prunastri (L.

Photostable and Small YVO:Yb,Er Upconversion Nanoparticles in Water.

In this work, we report a simple method of silica coating of upconversion nanoparticles (UCNPs) to obtain well-crystalline particles that remain small and not agglomerated after high-temperature post-annealing, and produce bright visible emission when pumped with near-infrared light. This enables many interesting biological applications, including high-contrast and deep tissue imaging, quantum sensing and super-resolution microscopy. These VO-based UNCPs are an attractive alternative to fluoride-based crystals for water-based biosensing applications.

Does Twisted π-Conjugation Framework Always Induce Efficient Intersystem Crossing? A Case Study with Benzo[]- and []Phenanthrene-Fused BODIPY Derivatives and Identification of a Dark State.

The photophysical properties, especially the intersystem crossing (ISC) of two heavy-atom-free BODIPY derivatives with twisted π-conjugated frameworks (benzo[]-fused BODIPY, ; and []phenanthrene-fused BODIPY, ), are studied with steady-state and time-resolved optical and electron paramagnetic resonance (TREPR) spectroscopic methods as well as with ADC(2) theoretical investigations. Interestingly, has a planar π-conjugation framework, but it displays UV-vis absorption (ε = 3.8 × 10 M cm at 569 nm) and fluorescence (Φ < 0.

Spiro Rhodamine-Perylene Compact Electron Donor-Acceptor Dyads: Conformation Restriction, Charge Separation, and Spin-Orbit Charge Transfer Intersystem Crossing.

Spiro rhodamine (Rho)-perylene (Pery) electron donor-acceptor dyads were prepared to study the spin-orbit charge transfer intersystem crossing (SOCT-ISC) in these rigid and sterically congested molecular systems. The electron-donor Rho (lactam form) moiety is attached via the N-C bond to the electron acceptor at either 1- or 3-position of the Pery moiety ( and ). Severe torsion of the Pery moiety in was observed.

Diluted Aqueous Dispersed Systems of 4-Aminopyridine: The Relationship of Self-Organization, Physicochemical Properties, and Influence on the Electrical Characteristics of Neurons.

A variety of physicochemical methods were used to examine the self-organization, physicochemical, UV absorption, and fluorescent properties of diluted aqueous solutions (calculated concentrations from 1·10 to 1·10 M) of the membrane voltage-dependent potassium channels blocker 4-aminopyridine (4-AP). Using the dynamic light scattering method, it was shown that 4-AP solutions at concentrations in the range of 1·10-1·10 M are dispersed systems in which domains and nanoassociates of hundreds of nm in size are formed upon dilution. An interrelation between the non-monotonic concentration dependencies of the size of the dispersed phase, the fluorescence intensity ( 225 nm, 340 nm), specific electrical conductivity, and pH has been established.

Engineering Red-Enhanced and Biocompatible Upconversion Nanoparticles.

The exceptional optical properties of lanthanide-doped upconversion nanoparticles (UCNPs) make them among the best fluorescent markers for many promising bioapplications. To fully utilize the unique advantages of the UCNPs for bioapplications, recent significant efforts have been put into improving the brightness of small UCNPs crystals by optimizing dopant concentrations and utilizing the addition of inert shells to avoid surface quenching effects. In this work, we engineered bright and small size upconversion nanoparticles in a core-shell-shell (CSS) structure.

Synthesis, Characterization, and Magnetoresistive Properties of the Epitaxial PdFe/VN/PdFe Superconducting Spin-Valve Heterostructure.

A thin-film superconductor(S)/ferromagnet(F) F1/S/F2-type PdFe(20 nm)/VN(30 nm)/PdFe(12 nm) heteroepitaxial structure was synthesized on (001)-oriented single-crystal MgO substrate utilizing a combination of the reactive magnetron sputtering and the molecular-beam epitaxy techniques in ultrahigh vacuum conditions. The reference VN film, PdFe/VN, and VN/PdFe bilayers were grown in one run with the target sample. In-situ low-energy electron diffraction and ex-situ X-ray diffraction investigations approved that all the PdFe and VN layers in the series grew epitaxial in a cube-on-cube mode.

Terbium(III)-thiacalix[4]arene nanosensor for highly sensitive intracellular monitoring of temperature changes within the 303-313 K range.

The work introduces hydrophilic PSS-[Tb(TCAn)] nanoparticles to be applied as highly sensitive intracellular temperature nanosensors. The nanoparticles are synthesized by solvent-induced nanoprecipitation of [Tb(TCAn)] complexes (TCAn - thiacalix[4]arenes bearing different upper-rim substituents: unsubstituted TCA1, tert-buthyl-substituted TCA2, di- and tetra-brominated TCA3 and TCA4) with the use of polystyrenesulfonate (PSS) as stabilizer. The temperature responsive luminescence behavior of PSS-[Tb(TCAn)] within 293-333 K range in water is modulated by reversible changes derived from the back energy transfer from metal to ligand (M* → T) correlating with the energy gap between the triplet levels of ligands and resonant D level of Tb ion.

Supraamphiphilic Systems Based on Metallosurfactant and Calix[4]resorcinol: Self-Assembly and Drug Delivery Potential.

Metallic amphiphiles are used as building blocks in the construction of nanoscale superstructures, where the hydrophobic effects induce the self-assembly of the nanoparticles of interest. However, the influence of synergizing multiple chemical interactions on an effective design of these structures mostly remains an open question. In this regard, supraamphiphilic systems based on flexible surfactant molecules and rigid macrocycles are being actively developed, but there are few works on the interaction between metallosurfactants and macrocycles.

Radical-Enhanced Intersystem Crossing in a Bay-Substituted Perylene Bisimide-TEMPO Dyad and the Electron Spin Polarization Dynamics upon Photoexcitation*.

A 4-amino-2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) radical was attached to the bay position of perylene-3,4 : 9,10-bis(dicarboximide) (perylenebisimide, PBI) to study the radical-enhanced intersystem crossing (REISC) and electron spin dynamics of the photo-induced high-spin states. The dyads give strong visible light absorption (ϵ=27000 M  cm at 607 nm). Attaching a TEMPO radical to the PBI unit transforms the otherwise non-radiative decay of S state (fluorescence quantum yield: Φ =2.

The effect of one-atom substitution on the photophysical properties and electron spin polarization: Intersystem crossing of compact orthogonal perylene/phenoxazine electron donor/acceptor dyad.

A perylene (Pery)-phenoxazine (PXZ) compact orthogonal electron donor/acceptor dyad was prepared to study the relationship between the molecular structures and the spin-orbit charge transfer intersystem crossing (SOCT-ISC), as well as the electron spin selectivity of the ISC process. The geometry of Pery-PXZ (80.0°) is different from the previously reported perylene-phenothiazine dyad (Pery-PTZ, 91.

Unusually large hyperfine structure of the electron spin levels in an endohedral dimetallofullerene and its spin coherent properties.

We report the synthesis, ESR spectroscopic and spin coherent properties of the dimetallofullerene Sc2@C80(CH2Ph). The single-electron metal-metal bond of the Sc2 dimer inside the fullerene's cage is stabilized with the electron spin density being fully localized at the metal bond. This results in an extraordinary strong hyperfine interaction of the electron spin with the 45Sc nuclear spins with a coupling constant a = 18.

Mathematical description data: Spin-resolved electron transport in nanoscale heterojunctions: Theory and applications.

This study demonstrates a mathematical description of a point-like nanocontact model, which is developed to simulate electron transport through a nanoconstriction between magnetic or non-magnetic contact sides. The theory represents a solution to the quasi-(semi)-classical transport equations for charge current, which takes into account second-order derivatives of the related quasi-classical Green functions along the transport direction. The theoretical approach also enables the creation of an model for a heterojunction with embedded objects, where the initial condition, a conduction band minimum profile of the system, is well-defined.

Reversible triplet energy hopping in photo-excited molecules: A two-site model for the spin polarization.

The effect of reversible energy hopping between different local environments on the properties of spin-polarized excited states is investigated theoretically using a two-site model. The kinetic equations for the populations of the spin sublevels of the excited state are derived and then used to obtain analytical expressions for the evolution of the spin polarization of excited triplet states under specific conditions. The time dependence of the triplet state polarization patterns is also obtained by numerical solution of the kinetic equations.

Electron spin polarization transfer induced by triplet-radical interactions in the weakly coupled regime.

We report the observation of electron spin polarization transfer from the triplet state of a porphyrin to a weakly coupled nitroxide radical in a mutant of human neuroglobin (NGB). The native iron-containing heme substrate of NGB has been substituted with Zn(ii) protoporphyrin IX and the nitroxide has been attached via site-directed spin labeling to the Cys120 residue. A reference synthetic polypeptide with free base tetraphenylporphyrin and a nitroxide bound to it is also studied.

N^N Pt(II) Bisacetylide Complexes with Oxoverdazyl Radical Ligands: Preparation, Photophysical Properties, and Magnetic Exchange Interaction between the Two Radical Ligands.

To study the effect of a stable radical on the photophysical properties of a phosphorescent Pt(II) coordination framework and the intramolecular magnetic interaction between radical ligands in the N^N Pt(II) bisacetylide complexes, we prepared a series of N^N Pt(II) bis(acetylide) complexes with oxoverdazyl radical acetylide ligands. The linker between the Pt(II) center and the spin carrier was systematically varied, to probe the effect on the sign and magnitude of the spin exchange interactions between the radical ligands and photophysical properties. The complexes were studied with steady-state and femtosecond/nanosecond transient absorption spectroscopy, continuous-wave electron paramagnetic resonance (EPR) spectroscopy, and density functional theory (DFT) computations.

Correction: A simple synthetic approach to enhance the thermal luminescence sensitivity of Tb complexes with thiacalix[4]arene derivatives through upper-rim bromination.

Correction for 'A simple synthetic approach to enhance the thermal luminescence sensitivity of Tb3+ complexes with thiacalix[4]arene derivatives through upper-rim bromination' by Sergey N. Podyachev, et al., Dalton Trans.