Perylene Radical Research Articles

Perylene-Mediated Electron Leakage in Respiratory Chain to Trigger Endogenous ROS Burst for Hypoxic Cancer Chemo-Immunotherapy.

Perylene derivatives can be stimulated by the hypoxic tumor microenvironment to generate radical anion that is proposed to arouse electron exchange with oxidizing substance, and in turn, realize reactive oxygen species (ROS) burst. Here, three perylene therapeutic agents, PDI-NI, PDIB-NI, and PDIC-NI, are developed and it is found that the minimum lowest unoccupied molecular orbital (LUMO) energy level makes PDIC-NI most easily accept electrons from the oxidative respiratory chain to form lots of anions, and the resultant maximum ROS generation, establishing an unambiguous mechanism for the formation of perylene radical anions in the cell, presents solid evidence for LUMO energy level determining endogenous ROS burst. Stirringly, PDIC-NI-induced ROS generation arouses enhanced mitochondrial oxidative stress and concurrently activates immunogenic cell death (ICD), which not only efficiently kills lung tumor cells but also reprograms immunosuppressive tumor microenvironment, including the cytokine secretion, dendritic cell maturation, as well as cytotoxic T lymphocytes activation, to inhibit the growth of xenografted and metastasis tumor, presenting a proof-of-concept demonstration of perylene that acts as an integrated therapeutic agent to well realize hypoxia-activated chemotherapy with ICD-induced immunotherapy on lung cancer.

Role of Brønsted Surface Acid Sites of B2O3–Al2O3 Catalyst Supports in Perylene Radical Cation Formation Studied by Probe EPR with TEMPO Radicals

Role of Brønsted Surface Acid Sites of B₂O₃–Al₂O₃ Catalyst Supports in Perylene Radical Cation Formation Studied by Probe EPR with TEMPO Radicals

Using Density Functional Theory Based Methods to Investigate the Photophysics of Polycyclic Aromatic Hydrocarbon Radical Cations: A Benchmark Study on Naphthalene, Pyrene and Perylene Cations

AbstractUnrestricted DFT (UDFT), time‐dependent DFT (TDDFT) and spin‐flip TDDFT (SF‐TDDFT) were used to investigate the potential energy surfaces of the ground and first two electronic excited states of the naphthalene, pyrene and perylene radical cations. In particular, conical intersections (which play a central role in the photophysics of these cations) were located with these DFT‐based methods. The results are consistent with accurate multiconfigurational wavefunction‐based ab initio methods. These show that naphthalene and pyrene cations can quickly relax nonradiatively from their excited states back down to the original ground state species through easily accessible conical intersections, but the perylene cation cannot do so, due to the absence of any accessible funnels between the lowest excited state and the ground state, leaving radiative decay as the most probable photophysical pathway. This study paves the way for using computationally efficient density functional theory (DFT)‐based methods in future investigations of the photophysics of much larger polycyclic aromatic hydrocarbons, for which multiconfigurational wavefunction‐based methods become prohibitively expensive.

Controlled Regioselective Amination of Peryleneimides

AbstractPerylenediimides (PDIs) and perylenemonoimide diesters (PMIs) can be selectively substituted at the 1,6‐ or 7,12‐ positions of the bay region, respectively, by direct amination reactions. The reactions proceed by the formation of a perylene radical anion and its subsequent oxidation, and the yields range from 20–97 %. The amination can be tuned to obtain either mono‐ or disubstituted perylenes by varying the oxidants involved. The presence of the imide cycle is crucial for the transformation, although the amination occurs regioselectively at the bay‐region positions distant from the imide cycle.

Air-stable photoconductive films formed from perylene bisimide gelators

The photoconductivity of perylene-bisimide gelators correlates with the perylene radical anion, which is unusually highly stable in air for many hours.

Fabrication of a Poly(3-octylthiophene-2,5-diyl) Electrochemiluminescence Device Assisted by Perylene.

In this study, we report the light-emitting assistance effect of perylene on a polymer electrochemiluminescence (ECL) device using poly(3-octylthiophene-2,5-diyl) (P3OT). An ECL device is a liquid type self-luminous device with a simple structure, and can be fabricated by a relatively easy procedure. Significant improvement in luminescence properties was confirmed when 1.0 wt % perylene was added to the ECL device using 3.0 wt % P3OT. Improvements of about 12 times of the maximum luminescence intensity and about 23 times of the light-emitting time ratio compared with that of a P3OT ECL device were obtained. We conclude that the light-emitting assistance of perylene is achieved by perylene radical ions shuttling electrons to P3OT while they are moving around in the emitting solution. The light-emitting assistance effect of perylene was also confirmed when poly(3-dodecylthiophene-2,5-diyl), which has almost identical electrochemical and photophysical characteristics to those of P3OT, was used instead of P3OT.

Modeling of the mechanism of one-electron transfer from the perylene molecule to the oxygen molecule 3O2 in the HF medium

The thermodynamic parameters of the formation of the perylene radical cation in anhydrous hydrogen fluoride containing dissolved dioxygen were calculated by the ab initio method MP2. The protonated product of HF autoprotolysis was modeled as the H(FH) 3 + cluster. The 3O2 molecule was found to bind to the linear H(FH) 3 + cluster via a hydrogen bond. As the charge and multiplicity of the system change upon the capture of an electron, the oxygen-hydrogen fluoride cluster complex undergoes rearrangement to yield the hydroperoxyl radical OOH incorporated in a cycle formed by HF molecules. The free energy of electron transfer from the perylene molecule to the 3O2 molecule in the HF medium is about −38 kcal/mol.

Ultrafast Intramolecular Charge Transfer of Formyl Perylene Observed Using Femtosecond Transient Absorption Spectroscopy

The excited-state photophysics of formylperylene (FPe) have been investigated in a series of nonpolar, polar aprotic, and polar protic solvents. A variety of experimental and theoretical methods were employed including femtosecond transient absorption (fs-TA) spectroscopy with 130 fs temporal resolution. We report that the ultrafast intramolecular charge transfer from the perylene unit to the formyl (CHO) group can be facilitated drastically by hydrogen-bonding interactions between the carbonyl group oxygen of FPe and hydrogen-donating solvents in the electronically excited state. The excited-state absorption of FPe in methanol (MeOH) is close to the reported perylene radical cation produced by bimolecular quenching by an electron acceptor. This is a strong indication for a substantial charge transfer in the S(1) state in protic solvents. The larger increase of the dipole moment change in the protic solvents than that in aprotic ones strongly supports this observation. Relaxation mechanisms including vibrational cooling and solvation coupled to the charge-transfer state are also discussed.

Fluorescence of the perylene radical cation and an inaccessible D/D1 conical intersection: An MMVB, RASSCF, and TD-DFT computational study

The photophysics of the perylene radical cation (Pe(+)) was studied using the molecular mechanics-valence bond (MMVB) hybrid force field. Potential energy surfaces of the first three electronic states were investigated. Geometry optimizations of critical points-including conical intersections between the relevant electronic states-were performed using the MMVB analytical energy gradient for cations. No accessible planar conical intersection between the D(0) and D(1) states of Pe(+) was found; this is consistent with the experimentally observed D(1) lifetimes and the observation of D(1) emission from this cation in the condensed phase. Benchmark RASSCF and TD-DFT calculations support the reliability of the MMVB results.

Direct Analysis of Liquid Samples by Desorption Electrospray Ionization-Mass Spectrometry (DESI-MS)

Desorption electrospray ionization-mass spectrometry (DESI-MS) was evaluated for the direct analysis of liquid samples. Several interesting results were found. First, in contrast to the previous DESI analysis of dried solid samples that was limited to proteins with MW < or = 25 kDa (Anal. Chem. 2007, 79, 3514), bovine serum albumin (BSA, 66 kDa) was successfully ionized from solutions by DESI with observation of corresponding multiply charged ions. Second, direct DESI analysis of protein tryptic digest solutions without chromatographic separation, sample clean-up, and the sample drying step was demonstrated, providing reasonably good sequence coverage of 52% to 97%. Third, direct analysis of biofluids such as an undiluted urine sample without sample pretreatment is possible, emphasizing the high tolerance of DESI with salt. These results suggest that a charged droplet pick-up mechanism is responsible for desorption and ionization of liquid samples by DESI. Also, unlike in electrospray ionization (ESI), inhibition of electrochemical reduction in the negative ion mode was observed for liquid sample DESI. In addition, reactive DESI can be performed with ion/ion reactions of Zn(II) complexes for the selective binding of phosphoserine in the presence of serine. DESI experiment can also be carried out directly to liquid samples flowing out of a pumped syringe needle tip, allowing rapid analysis. Furthermore, on-line coupling of electrochemical cell with DESI-MS was demonstrated, in which perylene radical cations generated in the cell were successfully transferred to the gas-phase for MS detection by DESI. This study extended the scope of DESI-MS applications, which could have potentials in bioanalytical and forensic analysis.

Ultrafast Excited State Dynamics of the Perylene Radical Cation Generated upon Bimolecular Photoinduced Electron Transfer Reaction

The ultrafast ground state recovery (GSR) dynamics of the radical cation of perylene, Pe(*+), generated upon bimolecular photoinduced electron transfer in acetonitrile, has been investigated using pump-pump-probe spectroscopy. With 1,4-dicyanobenzene as electron acceptor, the free ion yield is substantial and the GSR dynamics of Pe(*+) was found to depend on the time delay between the first and second pump pulses, Deltat(12), i.e., on the "age" of the ion. At short Deltat(12), the GSR dynamics is biphasic, and at Deltat(12) larger than about 500 ps, it becomes exponential with a time constant around 3 ps. With trans-1,2-dicyanoethylene as acceptor, the free ion yield is essentially zero and the GSR dynamics of Pe(*+) remains biphasic independently of Deltat(12). The change of dynamics observed with 1,4-dicyanobenzene is ascribed to the transition from paired to free solvated ion, because in the pair, the excited ion has an additional decay channel to the ground state, i.e., charge recombination followed by charge separation. The rate constants deduced from the analysis of these GSR dynamics are all fully consistent with this hypothesis.

Anisotropy of charge and spin motion in perylene hexafluoroarsenate salts

Conduction electron spin echo attenuation in well defined magnetic field gradients providesmore accurate values of the anisotropy of electron spin motion than microwave conductivitymeasurements. The electron spin diffusion coefficient for motion along the perylene (PE)radical cation stack, , in the PE hexafluoroarsenate salt is influenced temperature dependently byperpendicular-to-stack motion and reflects the varying average unrestricted chain length,. The anisotropy of is larger than 7300:1 at 250 K.

Disproportionation of arene radical anions is driven overwhelmingly by solvation, not ion pairing

The equilibrium constants for disproportionation of anthracene and perylene radical anions into neutral and dianion both in the absence and presence of solvent and for ion pairing of the dianions to tetraethylammonium ion have been computed by density functional B3LYP/6-311+G* theory. The disproportionation equilibrium is shown to be highly influenced by differential solvation effects and only modestly by ion pairing.

Surface and adsorbates effects on the photochemistry and photophysics of adsorbed perylene on unactivated silica gel and alumina

The effect of the nature of the surface and solvent, the presence of coadsorbed species (O 2, Ar and H 2O) and the surface loading on some photophysical and photochemical properties of perylene (Per) are reported. Although the absorption and emission spectra of perylene adsorbed on alumina and silica gel of different average pore diameters are very similar to those observed in solution, adsorbed perylene presented spectra with broader bands, loss of vibrational structure, and a small red shift and extension to longer wavelengths. These are consequence of aggregate formation, π-stacking, and surface interactions. The nature of the environment affects also the lifetime of the first excited state, presenting a single-exponential decay when in solution and, at least, a double-exponential decay when adsorbed suggesting the adsorption on at least two major surface regions. As the average pore size increases, the emission spectra resembled more to that in solution and the photodegradation rate also increased. Sample loading causes a red shift of the bands on the emission spectrum and a change in the relative intensities of the first and second bands. Oxygen quenched significantly the fluorescence and accelerated the photodegradation. The participation of 1 O 2 in the photodegradation process was confirmed as well as the participation of a perylene radical cation, identified by laser diffuse reflectance transient and EPR spectroscopy. Coadsorbed water induced the formation of a new species, probably a perylene–H 2O complex on the surface.

Temperature dependence of intra-stack defect spin–conduction-electron spininteraction in fluoranthene and perylene radical cation salts

The electron spin resonance line-width anisotropy and intensity areanalysed for the quasi-one-dimensional organic conductors (fluoranthene)2PF6and (perylene)2PF6·2/3tetrahydrofurane in the metallic phase above the Peierls transition temperature.Based on the bottleneck model of relaxation, the temperature dependence of theintra-stack exchange constant between conduction-electron spins and localizeddefect spins is derived and discussed.

Femtosecond Resonance-Enhanced Multiphoton Ionization of Perylene in Hexane. Electronic Excitation of the Radical Cation and Evidence of Hydrogen Abstraction from the Solvent

We demonstrate that perylene in solution can be highly excited with relatively weak femtosecond radiation via two-photon resonance-enhanced multiphoton ionization and excitation. The femtosecond multiphoton excitation spectra of two different observables are presented for perylene dissolved in hexane. The first of these is the normal S 1 → S 0 fluorescence that arises from relaxation of perylene through the singlet manifold after multiphoton excitation. The second observable is the ion yield that results from multiphoton ionization. A comparison of these two excitation spectra is presented, and their striking similarity indicates that both processes occur via the same initial two-photon resonance in the 500-550 nm region. A mechanism is presented illustrating the predicted excitation and relaxation pathways. The multiphoton-excited emission spectrum of the sample exhibits anomalous emission in the 550-620 nm range. Comparison of this emission with the one-photon-excited emission spectrum of perylene in concentrated sulfuric acid shows that the anomalous emission originates from electronic excitation of cationic species present in sulfuric acid. Previous assignment of emission from perylene dissolved in sulfuric acid to the protonated cation implies that the perylene radical cation in hexane abstracts a hydrogen atom from the solvent on an ultrafast time scale.

Magnetic susceptibility and electrical conductivity of Perylene radical cation salts

Conduction electron properties of the quasi-one-dimensional conductors (PE)2XF6 X 2/3 THF, X = P, As and (PE)4(SbF6)3 (PE = perylene, THF = tetrahydrofurane) were investigated by measuring magnetic susceptibility and microwave conductivity in the temperature range from 10 K to 300 K. For quantitative analysis of the measurements a microscopic model was developed.

Spin density distribution of the conduction electrons in diperylene hexafluorophosphate analysed by high-resolution NMR

High-resolution 13C nuclear magnetic resonance with 1H cross polarization and 1H decoupling under magic angle spinning is measured for the quasi-one dimensional organic conductor diperylene hexafluorophosphate (including tetrahydrofurane solvent molecules) at temperatures between 160 K and 270 K. Ab initio molecular orbital calculations are used for chemical shift analysis and for assignment of Knight shifted lines and individual carbon positions. The coexistence of neutral perylene molecules and perylene radicals in the same radical cation salt is revealed. From Knight and chemical shifts we were able to distinguish two inequivalent perylene radicals within the conducting stack. The spin density distribution of the molecular electronic wave function is determined quantitatively for these radicals.

X-ray diffuse scattering and magnetic resonance: a study of structural phase transitions in perylene radical cation salts

The quasi-one-dimensional organic conductors di-perylene hexafluorophosphate and -antimonate undergo three and two structural phase transitions below room temperature, respectively. The unequivocal structural proof of the Peierls transition at T p in both compounds is provided by X-ray diffuse scattering experiments. The characterization of the structural phase transitions above T p is done using the analysis of X-ray patterns together with previously known ESR results. The combined techniques offer new insight into the relative displacements and rotations of the perylene stacks. The relationship between the Peierls transition and the precursor transitions is discussed.

Magnetic susceptibility and electrical conductivity of Perylene radical cation salts

The minority model was introduced to study the competition between agents with limited information. It has the remarkable feature that, as the number of strategies available to the agents increases, the collective gain made by the agents is reduced. This crowd effect arises from the fact that only a minority can profit at each moment, while all agents make their choices using the same input. We show that the properties of the model change drastically if the agents make choices based on their individual stories, keeping all remaining rules unaltered. This variation reduces the intrinsic frustration of the model, and improves the tendency towards cooperation and self organization. We finally study the stable mixing of individual and collective behavior.