Motivated by recent detections of several aromatic nitriles in Taurus Molecular Cloud-1, we report laboratory and theoretical investigations of the vibrational spectroscopy and photochemistry of singly and doubly cyano-substituted benzene in solid para-hydrogen matrices. We compare the photochemistry of cyanobenzene (benzonitrile) and three dicyanobenzene isomers initiated by excitations at 193 nm. In addition, we report the photochemistry of deuterated cyanobenzene (d$_5$-cyanobenzene), enabling us to determine the major products produced during the cyanobenzene photodissociation. The major products observed in the photolysis of all the nitriles are HCN and HNC, which are likely produced by hydrogen abstraction from para-H$_2$ by the CN radical. This indicates that the major photodissociation channel involves cleavage of the bond between the ring and the nitrile group, forming the phenyl (or cyanophenyl) radical + CN. We observe secondary photoproducts similar to those found during benzene photolysis. Our findings may aid the interpretation of recent JWST mid-infrared observations of aromatics in photodissociation regions.

Weak interactions between the macrocyclic phenanthroline derivatives and hydrocarbon moieties were quantitatively evaluated by analyzing the NMR spectra of the rotaxanes. The observed associative interaction between the macrocycle and the 1,3-diyne moiety was further investigated by DFT calculations. The C─H⋯N interaction and reduced steric bulk of the 1,3-diyne moiety were assumed to be the origins of the interaction. These findings demonstrate that rotaxane architectures provide a powerful platform for the quantitative analysis of weak interactions.

Light-sensitive pharmaceuticals are susceptible to alteration or degradation under ambient light conditions, such as sunlight or artificial lighting, requiring pharmacists and patients to prevent exposure of these drugs to light. However, the transition from fluorescent to light-emitting diode (LED) light has altered the ambient light characteristics within buildings. Dacarbazine, chemically known as 5-(3,3-dimethyl-1-triazen-1-yl)-1H-imidazole-4-carboxamide (DTIC), is a light-sensitive anticancer drug. Its photodegradation product, Diazo-IC (5-diazoimidazole-4-carboxamide) is known to cause vascular pain in patients during infusion. Utilizing UV/Vis spectroscopy, this study examines the photodegradation of DTIC in aqueous solution under fluorescent and light-emitting diode (LED) lighting conditions, which are both prevalent in contemporary buildings. Results indicate that DTIC remained stable when exposed to LED light, with no decomposition observed, whereas photodegradation occurred under fluorescent light. The residual ratio revealed that DTIC remained stable for 240 min under LED illumination, indicating that LED light exposure does not induce DTIC photodegradation. These findings suggest that the ongoing replacement of fluorescent lighting with LED in healthcare settings and patient residences may eliminate vascular pain associated with DTIC photodegradation in the near future.

Solid-state cyclic voltammetry (CV) of redox-active H-bonding {[RuIII(Hbim)3]}n (1) 1-D nanoporous crystals was performed using single crystals in MeCN solutions containing seven electrolyte cations with different effective ionic radii (EIRs). Two cations must be included to every nanochannel unit in {[RuIIRuII]2-} reductive states by a two-step and multi-electron transfer reaction through the {[RuIIIRuII]-} mixed-valency state. This study is the first to use solid-state CV to determine the EIR limitation of cations confinable in these crystals.

Ethylene and sulfur dioxide molecules were co-deposited on a CsI window at cryogenic temperature, and the photoproducts upon UV irradiation were observed using Fourier transform infrared (FTIR) spectroscopy. The products were found to be UV wavelength-dependent; at shorter wavelengths (λ = 266 nm) one strong peak was observed while more than three peaks were identified at longer UV wavelengths (λ = 300 nm). Spectral features changed seamlessly along with UV wavelength. Density functional theory (DFT) calculations were carried out for potential products, and spectral matches between observations and calculations seemed satisfactory, assuming a cyclic molecule (oxathietane 2-oxide) as the main photoproduct at longer UV wavelengths. On the other hand, the spectra of photoproducts at shorter UV wavelengths were reproduced by assuming the decomposition products of an intermediate, from the supplementary experiments using deuterated samples. Plausible photoreaction schemes were presented to account for the observed photoproducts.

Butin and butein are significant bioactive flavanones derived from plants, existing as tautomers of each other. However, their physicochemical attributes, such as their spectral profiles under varying experimental conditions in aqueous solutions and established chromatographic methods for distinguishing between them, remain undetermined. In this study, we determined the basic properties of butin and butein using conventional spectroscopic, reversed-phase, and chiral HPLC analyses. The spectra of the synthesized butin and butein were analyzed using a UV-Vis spectrophotometer in several solvents with different polarities as well as in aqueous solutions at various pH values. Furthermore, the behavior of the measured spectra was reproduced by calculations to reveal the effects of the solvent and pH on the spectra of butin and butein in organic and aqueous solutions. Subsequently, we assessed the structural stability of butin and butein using reversed-phase HPLC, which revealed that butein is unstable compared with butin in a general culture medium. The synthesized butin was effectively separated into R- and S-isomers with positive and negative Cotton effects, respectively, via HPLC using a chiral column. These findings will aid in uncovering the individual properties of both butin and butein that may have been concealed by their tautomerism and enable the synthesis of S-butin, which is typically challenging and time-consuming to isolate.

The crystals of [RuIII(HIm)3(Im)3](1) are one of the rapid proton-transport materials to work as proton conductors at high temperatures. The proton flow is caused by the strong rotations of Im⋅⋅⋅H−Im H-bonding imidazole groups from 200 K. In the upper left image, as the temperature increases to 400 K, six coordinated imidazole groups are strongly rotating to transport protons. In the lower right image, whole-molecule rotations start becoming the main rotation above 400 K. More information can be found in the Research Article by M. Tadokoro et al. (DOI: 10.1002/chem.202201397).

The 57Fe Mössbauer spectrum obtained after 57Mn (T1/2 = 1.45 min) implantation of solid hydrogen was measured at 7 K. The spectrum was analyzed as three components, and the chemical species of each component was assigned from the obtained Mössbauer parameters and the results of density functional theory (DFT) calculations. The formation process of chemical species and the oxidation states of Fe atoms produced by β– decay of 57Mn are discussed considering the charge transfer process, in relation to previous emission Mössbauer spectroscopy experiments with 57Co implantation of solid hydrogen at low temperature.

Invited for the cover of this issue is mainly the group of Makoto Tadokoro and co-workers at Tokyo University of Science. Other co-workers are Masaki Itoh, Ryota Nishimura, Kensuke Sekiguchi (TUS students), Dr. Norihisa Hoshino (Tohoku Univ.), Dr. Hajime Kamebuchi (Nihon Univ.), Dr. Jun Miyazaki (Tokyo Denki Univ.), Prof. Motohiro Mizuno (Kanazawa Univ.) and Prof. Tomoyuki Akutagawa (Tohoku Univ.). The image depicts on two mechanisms of proton transport rotations of the proton-conductive starburst molecule [RuIII (HIm)3 (Im)3 ]. Read the full text of the article at 10.1002/chem.202201397.

In-beam Mössbauer spectra of 57Mn implanted into LiAlH4 were measured at different temperatures between 17 and 300 K. The Mössbauer spectrum measured at 17 K showed two sets of doublets, which were assigned to 57Fe atoms at substitutional sites at Al3+ and Li+ sites. The Debye temperatures θM for the 57Fe atoms at Al3+-substituted and Li+-substituted sites were estimated to be 194 K and 117 K, respectively. The assignments were confirmed by density functional theory calculations.

1,3-cyclohexadiene was isolated in solid parahydrogen, and its photochemical reactions were studied via irradiation with 193 nm photons from an ArF excimer laser. Photoproducts were identified using Fourier-transform infrared spectroscopy supported by density functional theory calculations. Photolysis with 193 nm light caused the formation of two well-characterized conformers of 1,3,5-hexatriene, tZt-1,3,5-hexatriene and tEt-1,3,5-hexatriene. A third initial photoproduct was identified as the conformer cZc-1,3,5-hexatriene, and its infrared spectrum was characterized for the first time. In addition, the bicyclo[2.2.0]hex-2-ene and 1-methyl-bicyclo[2.1.0]pent-2-ene were also found to be a minor products from photo-induced ring-closure reactions, where the latter further converts to 2-methyl-cyclopentadiene. The reaction mechanisms and stability of these products are discussed using infrared spectroscopy and density functional theory calculations. (c) 2020 Elsevier B.V. All rights reserved.

To investigate the interactions of 57Fe atoms with sulfur hexafluoride SF6 molecules, in-beam Mössbauer spectra were measured for 57Mn implanted SF6 at 9 K and 65 K. Isolated 57Fe atoms or ions produced by β-decay were not trapped within the SF6 matrix. At 9 K, monomeric FeF2 and FeF3 molecules were produced by reaction of 57Fe with F atoms released by decomposition of the SF6 molecules. When the temperature of the SF6 solid was increased to 65 K, FeF4 was formed in addition to FeF2 and FeF3. Density functional calculations were performed to confirm the assignments of the candidate species identified in the Mössbauer spectra.

Infrared spectra of the photochemical products of bis(cyclopentadienyl)dicarbonyl titanium, TiCp2(CO)2, isolated in an Ar matrix and a N2 matrix were measured. UV-irradiation of TiCp2(CO)2 produced TiCp2(CO) in the Ar matrix, and three types of nitrogen-containing compounds, TiCp2(CO)(N2), TiCp2(N2), and TiCp2(N2)2 were produced in the N2 matrix. The yields of the species changed with the duration of UV-irradiation. Annealing of the sample resulted in the disappearance of unstable TiCp2(N2) and an increase of TiCp2(N2)2. Isotope shifts of the infrared spectra were measured using 15N2 to confirm the assignments. The structures of the species were estimated using a double hybrid density functional theory calculation (mPW2PLYP/cc-pVTZ), and the calculated infrared frequencies were in very good agreement with the experimentally measured spectra.

In-beam Mössbauer spectra of 57Mn implanted into a low-temperature Ar solid were measured. Only 57Fe+ with the 3d7 electronic configuration was observed. The production mechanism of 57Fe+ (3d7) is discussed in terms of a charge transfer process between charged species and the surrounding Ar atoms; Mn2+ was trapped in a substitutional position in the fcc Ar lattice, and β-decay of 57Mn2+ produced 57Fe3+ followed by the formation of 57Fe+ (3d7) without disturbing the symmetric surrounding of the Ar lattice. The temperature dependence of the recoil free fraction was well described using the Debye temperature ΘD = 61.3 K.

Hydrogen bonding is one of the exciting and interesting research themes because it plays important roles in biomolecules, plant cells, and so on. Here we report hydrogen-bonded complexes among the photodecomposition products of thiazole, being studied by a joint use of infrared (IR) spectroscopy and density-functional-theory (DFT) calculations. Three types of hydrogen-bonded complexes of ethynethiol (HSCCH) and hydrogen cyanide (HCN), which are photodecomposed by two cleavages of the NC–SC and CN–CC single bonds of thiazole in argon matrices, have been identified by comparison of the observed IR spectra with the corresponding calculated spectral patterns. In addition, another complex with weak interaction between S atom and HCN, which are photoproduced by cleavages of the three single bonds of thiazole, is detected by comparison with the wavenumbers previously reported in literature. The reaction mechanisms to form these complexes are discussed based on the analysis of IR spectra and the DFT calculations.

Faculty of Pharmaceutical Sciences, Hoku Kanazawa, Ishikawa 920-1181, Japan. E-ma Department of Chemical Engineering, Tokyo 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 Graduate School of BASE (Bio-Applicati University of Agriculture and Technology, 8588, Japan. E-mail: necom816@cc.tuat.ac. † Electronic supplementary information wavenumbers and IR intensities of thiazo with references, and calculated wa 2-isocyanoethenethiol (2), 2-isocyanoeth (methyleneamino)-ethenethione (5), N-eth and 2-cyanothiirane obtained at the a gure showing calculated potential ene angle of N-ethynylthioformamide (6)obtai interval of 15 . See DOI: 10.1039/c6ra2749 Cite this: RSC Adv., 2017, 7, 4960

UV-induced photoreactions of thiazole isolated in low-temperature argon matrices have been investigated, leading to the conclusion that photoproducts identified newly, including three kind isocyano compounds, are produced by ring-opening reaction.