Measurement of Photosynthesis Using PAM Technology in a Purple Sulfur Bacterium Thermochromatium tepidum (Chromatiaceae)

We demonstrate that Blue‐diode‐based pulse amplitude modulation (PAM) technology can be used to measure the photosynthetic electron transport rate (ETR) of purple sulfur bacteria (Thermochromatium tepidum, Chromatiaceae). Previous studies showed that PAM technology could be used to estimate photosynthesis in purple nonsulfur bacteria and so PAM technology can be used to estimate photosynthesis of both kinds of purple photosynthetic bacteria. The absorptance of Thermochromatium films on glass fiber disks was measured and used to calculate actual ETR. ETR vs Irradiance (P vs E) curves fitted the waiting‐in‐line model (ETR = (ETR_max × E/E_opt) × exp (1?E/E_opt)). Yield (Y) was only ≈ 0.3–0.4. Thermochromatium saturates at 325 ± 13.8 μmol photons m^?2 s^?1 or ≈15% sunlight and shows photoinhibition at high irradiances. A pond of Thermochromatium would exhibit classic surface inhibition. Photosynthesis is extremely low in the absence of an electron source: ETR increases in the presence of acetate (5 mol m^?3) provided as an organic carbon source and also increases in the presence of sulfite (3 mol m^?3) but not sulfide and is only marginally increased by the presence of Fe²⁺. Nonphotochemical quenching does occur in Thermochromatium but at very low levels compared to oxygenic photo‐organisms or Rhodopseudomonads.     

Photosynthetic Electron Transport in an Anoxygenic Photosynthetic Bacterium Afifella (Rhodopseudomonas) marina Measured Using PAM Fluorometry

Blue diode‐based pulse amplitude modulation (PAM) technology can be used to measure the photosynthetic electron transport rate (ETR) in a purple nonsulfur anoxygenic photobacterium, Afifella (Rhodopseudomonas) marina. Rhodopseudomonads have a reaction center light harvesting antenna complex containing an RC‐2 type bacteriochlorophyll a protein (BChl a RC‐2‐LH1) which has a blue absorption peak and variable fluorescence similar to PSII. Absorptance of cells filtered onto glass fiber disks was measured using a blue–diode‐based absorptance meter (Blue‐RAT) so that absolute ETR could be calculated from PAM experiments. Maximum quantum yield (Y) was ≈0.6, decreasing exponentially as irradiance increased. ETR vs irradiance (P vs E) curves fitted the waiting‐in‐line model (ETR = (ETR_max × E/E_opt) × exp(1 ? E/E_opt)). Maximum ETR (ETR_max) was ≈1000–2000 μmol e^? mg^?1 BChl a h^?1. Fe²⁺, bisulfite and thiosulfate act as photosynthetic electron donors. Optimum irradiance was ≈100 μmol m^?2 s^?1 PPFD even in Afifella grown in sunlight. Quantum efficiencies (α) were ≈0.3–0.4 mol e^? mol hλ^?1; or ≈11.8 ± 2.9 mol e^? mol hλ^?1 m² μg^?1 BChl a). An underlying layer of Afifella in a constructed algal/photosynthetic bacterial mat has little effect on the measured ETR of the overlying oxyphotoautotroph (Chlorella).     

Why is Rose Bengal More Phototoxic to Fibroblasts In Vitro Than In Vivo?

Photosensitized protein cross‐linking has been recently developed to seal wounds and strengthen tissue. Although the photosensitizing dye, Rose Bengal (RB), is phototoxic to cultured cells, cytotoxicity does not accompany RB‐photosensitized tissue repair in vivo. We investigated whether the environment surrounding cells in tissue or the high irradiances used for photo–cross‐linking inhibited RB phototoxicity. Fibroblasts (FB) grown within collagen gels to mimic a tissue environment and monolayer cultured FB were treated with RB (0.01–1 mm ) and the high 532 nm laser irradiances used in vivo for tissue repair (0.10–0.50 W cm^?2). Monolayer FB were substantially more sensitive to RB photosensitization: the LD₅₀ was >200‐fold lower than that in collagen gels. Collagen gel protection was associated with increased Akt phosphorylation, a prosurvival pathway. RB phototoxicity in collagen gels was 25‐fold greater at low (0.030 W cm^?2) that at high (0.50 W cm^?2) irradiances. Oxygen depletion at high irradiance only partially accounted for the irradiance dependence of phototoxicity as replacing air with nitrogen only increased the LD₅₀ by four‐fold in monolayers. These results indicate that the lack of RB phototoxicity during in vivo tissue repair results from upregulation of prosurvival pathways in tissue cells, oxygen depletion and irradiance‐dependent RB photochemistry.     

Addition–fragmentation chain transfer: Molecular weight distributions and retardation in the system methyl methacrylate/methyl α‐(bromomethyl)acrylate

A detailed investigation of addition–fragmentation chain transfer (AFCT) in the free‐radical polymerization of methyl methacrylate (MMA) in the presence of methyl α‐(bromomethyl)acrylate (MBMA) was carried out to elucidate mechanistic details with efficient macromonomer synthesis as an underlying goal. Advanced modeling techniques were used in connection with the experimental work. Curve fitting of simulated and experimental molecular weight distributions with respect to the rate coefficient for addition of propagating radicals to MBMA (k_add) over 60–120 °C resulted in E_add = 21.7 kJ mol^?1 and A_add = 2.18 × 10⁶ M^?1 s^?1 and a very weak temperature dependence of the chain‐transfer constant (E_add ≈ E_p). The rate coefficient for fragmentation of adduct radicals at 60 °C was estimated as k_f ≈ 39 s^?1 on the basis of experimental data of the MMA conversion and the concentration of 2‐carbomethoxy‐2‐propenyl end groups. The approach developed is generic and can be applied to any AFCT system in which copolymerization does not occur and in which the resulting unsaturated end groups do not undergo further reactions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2640–2650, 2004     

Difluorenyl carbo‐Benzenes: Synthesis,Electronic Structure,and Two‐Photon Absorption Properties of Hydrocarbon Quadrupolar Chromophores

The synthesis, crystal and electronic structures, and one‐ and two‐photon absorption properties of two quadrupolar fluorenyl‐substituted tetraphenyl carbo‐benzenes are described. These all‐hydrocarbon chromophores, differing in the nature of the linkers between the fluorenyl substituents and the carbo‐benzene core (C?C bonds for 3 a , C?C?C?C expanders for 3 b ), exhibit quasi–superimposable one‐photon absorption (1PA) spectra but different two‐photon absorption (2PA) cross‐sections σ_2PA. Z‐scan measurements (under NIR femtosecond excitation) indeed showed that the C?C expansion results in an approximately twofold increase in the σ_2PA value, from 336 to 656 GM (1 GM=10^?50 cm⁴ s molecule^?1 photon^?1) at λ=800 nm. The first excited states of A_u and A_g symmetry accounting for 1PA and 2PA, respectively, were calculated at the TDDFT level of theory and used for sum‐over‐state estimations of σ_2PA(λ_i), in which λ_i=2 hc/E_i, h is Planck’s constant, c is the speed of light, and E_i is the energy of the 2PA‐allowed transition. The calculated σ_2PA values of 227 GM at 687 nm for 3 a and 349 GM at 708 nm for 3 b are in agreement with the Z‐scan results.     

Steric Demand and Rate‐determining Step for Photoenolization of Di‐ortho‐substituted Acetophenone Derivatives

Laser flash photolysis of ketone 1 in argon‐saturated methanol yields triplet biradical 1BR (τ = 63 ns) that intersystem crosses to form photoenols Z‐1P (λ_max = 350 nm, τ ~ 10 μs) and E‐1P (λ_max = 350 nm, τ > 6 ms). The activation barrier for Z‐1P re‐forming ketone 1 through a 1,5‐H shift was determined as 7.7 ± 0.3 kcal mol^?1. In contrast, for ketone 2, which has a less sterically hindered carbonyl moiety, laser flash photolysis in argon‐saturated methanol revealed the formation of biradical 2BR (λ_max = 330 nm, τ ~ 303 ns) that intersystem crosses to form photoenol E‐2P (λ_max = 350 nm, τ > 42 μs), but photoenol Z‐2P was not detected. However, in more viscous basic H‐bond acceptor (BHA) solvent, such as hexamethylphosphoramide, triplet 2BR intersystem crosses to form both Z‐2P (λ_max = 370 nm, τ ~ 1.5 μs) and E‐2P. Thus, laser flash photolysis of ketone 2 in methanol reveals that intersystem crossing from 2BR to form Z‐2P is slower than the 1,5‐H shift of Z‐2P, whereas in viscous BHA solvents, the 1,5‐H shift becomes slower than the intersystem crossing from 2BR to Z‐2P. Density functional theory and coupled cluster calculations were performed to support the reaction mechanisms for photoenolization of ketones 1 and 2 .     

Gadolinium(III) Porpholactones as Efficient and Robust Singlet Oxygen Photosensitizers

Construction of Gd^III photosensitizers is important for designing theranostic agents owing to the unique properties arising from seven unpaired f electrons of the Gd³⁺ ion. Combining these with the advantages of porpholactones with tunable NIR absorption, we herein report the synthesis of Gd^III complexes Gd‐1 – 4 ( 1 , porphyrin; 2 , porpholactone; 3 and 4 , cis‐ and trans‐porphodilactone, respectively) and investigated their function as singlet oxygen (¹O₂) photosensitizers. These Gd complexes displayed ¹O₂ quantum yields (Φ_Δs) from 0.64–0.99 with the order Gd‐1 < Gd‐2 < Gd‐3 < Gd‐4 . The gradually enhanced ¹O₂ sensitization after β‐oxazolone moiety replacement was ascribed to the narrowing of the energy gap (ΔE) between the lowest triplet states (T₁) of the ligand and the energy level of the ¹Δ_g→³Σ_g transition of ¹O₂. In particular, Gd‐4 is capable of excitation in the visible to NIR region (400–700 nm) with a quantum yield near unity. These Gd complexes were first demonstrated as efficient photosensitizers in photocatalysis such as oxidative C?H bond functionalization of secondary or tertiary amines, and the oxygenation of the natural product cholesterol. Finally, after glycosylation, these water‐soluble Gd complexes showed potential applications in photodynamic therapy (PDT) in HeLa cells. This work revealed that Gd^III complexes of “bioinspired” β‐modified porpholactones are efficient NIR photosensitizers and form a chemical basis to construct appealing photocatalysts and theranostic agents based on lanthanides.     

Ionic and excited species in irradiated poly(dimethylsiloxane) doped with pyrene

The influence of temperature (77–230 K) on the fate of pyrene (Py) radical ions and Py excited states in irradiated poly(dimethylsiloxane) (PDMS) doped with Py is described. At 77 K, the Py radical ions seem to be stable, whereas the Py excited states [fluorescence (λ = 395 nm) and phosphorescence (λ = 575–650 nm)] are generated via tunneling charge transfer. In the range of the glass‐transition temperature (T_g = 152–153 K), the Py radical ions start to decay, taking part in a recombination process and leading to the Py monomer and Py excimer fluorescence (λ = 475 nm). The wavelength‐selected radiothermoluminescence (WS RTL) observed at approximately 395, 475, and 600 nm has helped us to identify the T_g range (152–153 K). The absorption maximum at approximately 404 nm, found in the temperature range under consideration, is thought to represent PyH^?, cyclohexadienyl‐type radicals produced as a result of the reaction of Py^?? with protonated PDMS macromolecules. With the initial‐rise method of evaluating the activation energy (E_a) with the WS RTL peaks observed in the T_g range, E_a values of 123–151 kJ mol^?1 have been found. Such high E_a values can be explained by the contribution of energy connected to the molecular relaxation of the matrix in the T_g range. The well‐known Williams–Landel–Ferry equation, with universal constants C₁ = 17.4 and C₂ = 12.7, has been successfully applied to the interpretation of old pulse‐radiolysis/viscosity data found for crosslinked PDMS doped with Py. The mechanisms involved in these phenomena are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6125–6133, 2004     

Experimental Study of the Reactions of OH Radicals with Propane,n‐Pentane,and n‐Heptane over a Wide Temperature Range

The kinetics of the reactions of propane, n‐pentane, and n‐heptane with OH radicals has been studied using a low‐pressure flow tube reactor (P = 1 Torr) coupled with a quadrupole mass spectrometer. The rate constants of the title reactions were determined under pseudo–first‐order conditions, monitoring the kinetics of OH radical consumption in excess of the alkanes. A newly developed high‐temperature flow reactor was validated by the study of the OH + propane reaction, where the reaction rate constant, k₁ = 5.1 × 10^?17T^1.85exp(–160/T) cm³ molecule^?1 s^?1 (uncertainty of 20%), measured in a wide temperature range, 230–898 K, was found to be in excellent agreement with previous studies and current recommendations. The experimental data for the rate constants of the reactions of OH with n‐pentane and n‐heptane can be represented as three parameter expressions (in cm³ molecule^?1 s^?1, uncertainty of 20%): k₂ = 5.8 × 10^?18T^2.2exp(260/T) at T= 248–900 K and k₃ = 2.7 × 10^?16T^1.7exp(138/T) at T= 248–896 K, respectively. A combination of the present data with those from previous studies leads to the following expressions: k₁ = 2.64 × 10^?17T^1.93exp(–114/T), k₂ = 9.0 × 10^?17T^1.8 exp(120/T), and k₃ = 3.75 × 10^?16 T^1.65 exp(101/T) cm³ molecule^?1 s^?1, which can be recommended for k₁, k₂, and k₃ (with uncertainty of 20%) in the temperature ranges 190–1300, 240–1300, and 220–1300 K, respectively.     

Properties of excited singlet states of N-arylurethanes : Photo-fries reactions,fluorescence, quenching and sensitization

The deactivation of the first excited S(ππ^*) states of N-arylurethanes (produced upon irradiation with UV light) by emission (fluorescence), chemical reaction (photo-Fries rearrangement and fragmentation), energy transfer to quenchers, and radiationless transitions to ground and triplet states is investigated. Arylurethanes exhibit fluorescence (λ_f ≈ 295–350 nm, φ_f ≈ 10^?2, τ_f ≈ 1–6 ns) and phosphorescencs (λ_p ≈ 370–410 nm). The variations of the quantum yields of the fluorescence and of the photo-Fries rearrangement of N-arylurethanes by substituents and solvents are essentially due to variations of the rate constants for the radiationless processes. Fluorescence and photo-Fries reactions can be quenched by diffusion-controlled energy transfer to aliphatic ketones. Quenching is accompanied by sensitization of the ketone fluorescence. The urethane fluorescence and photo reactions may be sensitized by aromatic hydrocarbons. The results of all the quenching and sensitization experiments demonstrate that the photo-Fries reactions of N-arylurethanes proceed via the first excited singlet states of the urethanes.     

Effectiveness of the Photoactive Dye Methylene Blue versus Caspofungin on the Candida parapsilosis Biofilm in vitro and ex vivo

This research studied the effectiveness of the photoactive compound methylene blue (MB) activated with red LED light (576–672 nm) compared to that of caspofungin (CAS) on 1 Candida albicans and 3 Candida parapsilosis strains. Results were evaluated in terms of SMIC₅₀ for CAS or in PDI (photodynamic inactivation)‐SMIC₅₀ for MB (minimal inhibitory concentration inhibiting sessile biofilm to 50% in comparison to the control without CAS or after irradiation in comparison to the control without MB). While all strains were susceptible to CAS in planktonic form, the SMIC₅₀ was determined to be >16 μg mL^?1 when CAS was added to a 24 h biofilm. However, PDI‐MIC_50s (1.67 mW cm^?2, fluence 15 J cm^?2) were 0.0075–0.03 mmol L^?1. For biofilm, PDI‐SMIC_50s were in the range from 0.7 to 1.35 mmol L^?1. MB concentration of 1 mmol L^?1 prevented a biofilm being formed ex vivo on mouse tongues after irradiation regardless of the application time, in contrast to CAS, which was only effective at a concentration of 16 μg mL^?1 when it was added at the beginning of biofilm formation. PDI seems to be a promising method for the prevention of microbial biofilms that do not respond significantly to conventional drugs.     

Study of carbonaceous clusters in irradiated polycarbonate with UV–vis spectroscopy

The formation of carbonaceous clusters in ion‐irradiated polymer films was investigated extensively. Information about these clusters may be obtained with ultraviolet–visible (UV–vis) spectroscopy. The optical band gap (E_g), calculated from the absorption edge of the UV spectra of these polymers, can be correlated to the number of carbon atoms (N) in a cluster with the modified Tauc equation. The structure of the cluster is also related to E_g; for example, a six‐membered‐benzene‐ring‐type structure has an E_g of ≈5.3 eV, whereas a buckminsterfullerene‐type structure has an E_g of ≈4.9 eV. These clusters are responsible for the electrical conductivity in these films. In this work, polycarbonate films (20 μm thick) were irradiated with 45‐MeV Li ions at fluences of 1 × 10¹² to 1 × 10¹³ cm⁻² and were characterized with UV–vis spectroscopy and impedance measurements. The E_g values, calculated from the absorption edge in the 280–315‐nm region with the Tauc relation, varied from 4.39 to 4.35 eV for the pristine and various irradiated samples, respectively. The cluster size showed a range of 60–62 carbon atoms per cluster. The sheet conductivity (σ_dc) and loss (tan δ) values of 10⁻¹⁶ Ω⁻¹cm⁻¹ and 10⁻³ for the pristine sample changed to 10⁻¹⁵ Ω⁻¹cm⁻¹ and 10⁻², respectively, for the irradiated samples. This increase in the values of σ_dc and tan δ may be correlated to the increase in the size of the carbonaceous clusters. This study provides insight into the mechanism of electrical conductivity in irradiated polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1589–1594, 2000     

Effects of PAR and UV‐B Radiation on Herbal Yield,Bioactive Compounds and Their Antioxidant Capacity of Some Medicinal Plants Under Controlled Environmental Conditions

Photosynthetically active radiation (PAR) and Ultraviolet B (UV‐B) radiation are among the main environmental factors acting on herbal yield and biosynthesis of bioactive compounds in medicinal plants. The objective of this study was to evaluate the influence of biologically effective UV‐B light (280–315 nm) and PAR (400–700 nm) on herbal yield, content and composition, as well as antioxidant capacity of essential oils and polyphenols of lemon catmint (Nepeta cataria L. f. citriodora), lemon balm (Melissa officinalis L.) and sage (Salvia officinalis L.) under controlled greenhouse cultivation. Intensive UV‐B radiation (2.5 kJ m^?2 d^?1) influenced positively the herbal yield. The essential oil content and composition of studied herbs were mainly affected by PAR and UV‐B radiation. In general, additional low‐dose UV‐B radiation (1 kJ m^?2d^?1) was most effective for biosynthesis of polyphenols in herbs. Analysis of major polyphenolic compounds provided differences in sensitivity of main polyphenols to PAR and UV‐B radiation. Essential oils and polyphenol‐rich extracts of radiated herbs showed essential differences in antioxidant capacity by the ABTS system. Information from this study can be useful for herbal biomass and secondary metabolite production with superior quality under controlled environment conditions.     

Bimetallic NiCo Functional Graphene: An Efficient Catalyst for Hydrogen‐Storage Properties of MgH2

Bimetallic NiCo functional graphene (NiCo/rGO) was synthesized by a facile one‐pot method. During the coreduction process, the as‐synthesized ultrafine NiCo nanoparticles (NPs), with a typical size of 4–6 nm, were uniformly anchored onto the surface of reduced graphene oxide (rGO). The NiCo bimetal‐supported graphene was found to be more efficient than their single metals. Synergetic catalysis of NiCo NPs and rGO was confirmed, which can significantly improve the hydrogen‐storage properties of MgH₂. The apparent activation energy (E_a) of the MgH₂? NiCo/rGO sample decreases to 105 kJ mol^?1, which is 40.7 % lower than that of pure MgH₂. More importantly, the as‐prepared MgH₂? NiCo/rGO sample can absorb 5.5 and 6.1 wt % hydrogen within 100 and 350 s, respectively, at 300 °C under 0.9 MPa H₂ pressure. Further cyclic kinetics investigation indicates that MgH₂? NiCo/rGO nanocomposites have excellent cycle stability.     

Synthesis and characterization of cyclic P3HT as a donor polymer for organic solar cells

In this study, cyclic poly(3‐hexylthiophene‐2,5‐diyl) (c‐P3HT) with a controlled M_n was synthesized by the intramolecular cyclization of α‐bromo‐ω‐ethynyl‐functionalized P3HT via the Sonogashira coupling reaction. The effect of the cyclic structure, which does not have terminal groups of polymers, on the photoelectric conversion characteristics was investigated in comparison to linear P3HT (l‐P3HT). c‐P3HT was successfully synthesized with M_n ≈ 17,000, dispersity ≈ 1.2, and regioregularity ≈ 99%. The hole mobility was determined to be 5.1 × 10^?4 cm² V^?1 s^?1 by time‐of‐flight (TOF) experiment. This was comparable to that of l‐P3HT of 5.6 × 10^?4 cm² V^?1 s^?1. Organic solar cell systems were fabricated with each polymer by blending them with [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM). The l‐P3HT:PC₇₁BM system showed a dispersive TOF photocurrent profile for electron transport, whereas a nondispersive profile was observed for c‐P3HT:PC₇₁BM. In addition, an amount of collected electrons in c‐P3HT:PC₇₁BM was greater than that in l‐P3HT:PC₇₁BM for TOF experiments. The photoelectric conversion characteristics were improved by using c‐P3HT rather than l‐P3HT (power conversion efficiency [PCE] = 4.05% vs 3.23%), reflecting the nondispersive transport and the improvement of electron collection. PCEs will be much improved by applying this cyclic concept to highly‐efficient OSC polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 266–271     

Stabilization of HHeF by Complexation: Is it a Really Viable Strategy?

Ab initio calculations at the MP2 and CCSD(T) levels of theory have disclosed the conceivable existence of fluorine‐coordinated complexes of HHeF with alkali‐metal ions and molecules M⁺ (M⁺=Li⁺–Cs⁺), M⁺–OH₂, M⁺–NH₃ (M⁺=Li⁺, Na⁺), and MX (M=Li, Na; X=F, Cl, Br). All these ligands L induce a shortening of the H? He distance and a lengthening of the He? F distance accompanied by consistent blue‐ and redshifts, respectively, of the H? He and He? F stretching modes. These structural effects are qualitatively similar to those predicted for other investigated complexes of the noble gas hydrides HNgY, but are quantitatively more pronounced. For example, the blueshifts of the H? He stretching mode are exceptionally large, ranging between around 750 and 1000 cm^?1. The interactions of HHeF with the ligands investigated herein also enhance the (HHe)⁺F^? dipole character and produce large complexation energies of around 20–60 kcal mol^?1. Most of the HHeF–L complexes are indeed so stable that the three‐body dissociation of HHeF into H+He+F, exothermic by around 25–30 kcal mol^?1, becomes endothermic. This effect is, however, accompanied by a strong decrease in the H? He? F bending barrier. The complexation energies, ΔE, and the bending barriers, E*, are, in particular, related by the inverse relationship E*(kcal mol^?1)=6.9exp[?0.041ΔE(kcal mol^?1)]. Therefore the HHeF? L complexes, which are definitely stable with respect to H+He+F+L (ΔE≈25–30 kcal mol^?1), are predicted to have bending barriers of only 0.5–2 kcal mol^?1. Overall, our calculations cast doubt on the conceivable stabilization of HHeF by complexation.     

The Synthesis,X‐ray Structure Analysis,and Photophysical Characterization of 4‐[(E)‐2‐(4‐Carboxyphenyl)diazenyl]‐morpholine

4‐[(E)‐2‐(4‐Carboxyphenyl)diazenyl]‐morpholine ( 1 ) was prepared in 33% yield from a coupling reaction between morpholine and the diazonium ion formed from 4‐aminobenzoic acid. X‐ray structural analysis of 1 yielded two important insights into its structure: the geometry of the N―N double bond and the partial delocalization across the linear triazene moiety. The absorption spectra of 1 in dilute acetonitrile and 2‐methyltetrahydrofuran solutions both featured an intense (ε ≈ 20,000 M^?1cm^?1) band centered at 320–324 nm that was assigned as a mixture of π → π* and n → π* transitions. Emission was observed at 383 and 379 nm from dilute acetonitrile and 2‐methyltetrahydrofuran solutions of 1 , respectively, with the latter being red‐shifted to 439 nm at 77 K. Emission lifetime data for compound 1 provided evidence that the emission was a mixture of two excited state transitions.     

Characterisation of microstructure and evaluation of optical and EPR properties of superhydrophobic copper dodecanoate films

Copper dodecanoate films prepared by emulsion method exhibit superhydrophobic property with water contact angle of 155° and sliding angle of <2°. The films have been characterised by using X‐ray diffraction, field emission scanning electron microscopy and Fourier transform infrared spectroscopy techniques. Surface microstructure of copper dodecanoate consists of numerous microscale papillas of about 6–12 µm in length with a diameter in the range of 360–700 nm. The superhydrophobicity of the films is due to their dual micronano surface morphology. The wetting behaviour of the film surface was studied by a simple water immersion test. The results show that copper dodecanoate film retained superhydrophobic property even after immersing in water for about 140 h. The optical absorption spectrum exhibits two broadbands centred at 388 and 630 nm that have been assigned to ²B_1g → ²E_g and ²B_1g → ²B_2g transitions of Cu²⁺ ions, respectively. The electron paramagnetic resonance spectrum exhibits two resonance signals with effective g values at g_|| ≈ 2.308 and g_⊥ ≈ 2.071, which suggests that the unpaired electron occupies d_x2–y2 orbital in the ground state. Copyright © 2011 John Wiley & Sons, Ltd.     

Quinoidal Azaacenes: 99 % Diradical Character

Quinoidal azaacenes with almost pure diradical character (y=0.95 to y=0.99) were synthesized. All compounds exhibit paramagnetic behavior investigated by EPR and NMR spectroscopy, and SQUID measurements, revealing thermally populated triplet states with an extremely low‐energy gap ΔE_ST′ of 0.58 to 1.0 kcal mol^?1. The species are persistent in solution (half‐life≈14–21 h) and in the solid state they are stable for weeks.     

Homoatomare Cluster E93– mit E = Ge,Sn und Pb: EPR‐Spektren,Magnetismus und Elektrochemie

Homoatomic Clusters E₉^3– with E = Ge, Sn, and Pb: EPR Spectra, Magnetism and Electrochemistry The properties of the compounds [K‐([2.2.2]‐crypt)]₃E₉ (E = Ge ( 1 ), Sn ( 2 ), Pb ( 3 )), which contain isolated E₉ units, have been examined by EPR measurements at room temperature and at 77 K, magnetic susceptibility measurements in the range from 2 K to 300 K and cyclovoltammetric experiments. The EPR signals of powder samples and of single crystals are analyzed using three g tensor components, indicating low symmetric E₉^3– clusters. Magnetic susceptibility data of 2 and 3 follow the expression (χ_mol = C/(T – θ_p) + χ₀, with θ_p ≈ 0 and C corresponding to the presence of about 50% paramagnetic E₉^3– species (S = ¹/₂). In solution, 2 and 3 show irreversible oxidation processes. Current intensities and peak forms indicate that adsorption processes play an important role irrespective of the material of the working electrode (silver, platinum, glassy carbon).