The vibration-rotation spectrum of C-fluorophosphaethyne FCP: Fermi resonance and harmonic force field

The vibration-rotation bands of all the fundamentals and several overtone and combination vibrations of F¹²CP have been recorded. The C-F stretching fundamental ν₃ was observed in strong Fermi resonance with the overtone 2ν₂⁰; a similar resonance was also observed between ν₁ + ν₃ and ν₁ + 2ν₁⁰. The spectral analysis gave fundamental wavenumbers: ν₁ = 1670.842 (9), ν₂ = 375.428 (6), and ν₃ = 780.10 (22) cm⁻¹. The value of the equilibrium rotational constant B_e was found to be 0.1758943 (81) cm⁻¹. The harmonic force field for this molecule was derived from the wavenumbers of the three fundamentals and the l-doubling constant.     

Current state for the development of metallopharmaceutics and anti-diabetic metal complexes

This tutorial review introduces the current state of metallopharmaceutics development by focusing on the topics of anti-diabetic vanadium and zinc complexes. Over thousands of years, people have produced many types of inorganic compounds, and the modern concept of chemotherapy was achieved by Ehrlich, who used an arsenic-containing compound to treat syphilis. Since then, many metallopharmaceutics have been developed worldwide. This review will be helpful to researchers who are interested in the current states of not only metallopharmaceutics but also anti-diabetic metal complexes.     

Fluorescence quenching of versatile fluorescent probes based on strongly electron-donating distyrylbenzenes responsive to aromatic chlorinated and nitro compounds, boronic acid and Ca(2+)

The fluorescence quenching behavior of two distyrylbenzenes (DSBs) newly prepared bearing strongly electron-donating groups was investigated. Several chlorinated and nitro compounds quench the fluorescence of both DSBs with various efficiencies depending on the electron-withdrawing properties; the strongly electron-withdrawing compound, such as 2,4,5-trichlorophenol and 2,4-dinitrofluorobenzene, effectively diminish the fluorescence intensities of the DSBs. The fluorescence quenching was also detected in the interaction between the azacrown DSB and phenylboronic acid, while the fluorescence recovers by adding triethylamine. These quenching phenomena are attributed to the photo-induced electron transfer (PET) process. On the other hand, the azacrown DSB selectively interacts with Ca(2+) to decrease its fluorescence intensity, but the DSB with the dimethylamino groups did not. These results suggest a potential use of these types of compounds as sensors for strongly electron-withdrawing substances and a suitable metal cation.     

Threoninol as a scaffold of dyes (threoninol-nucleotide) and their stable interstrand clustering in duplexes

Functional molecules such as dyes (Methyl Red, azobenzene, and Naphthyl Red) were tethered on D-threoninol as base surrogates (threoninol-nucleotide), which were consecutively incorporated at the center of natural oligodeoxyribonucleotides (ODNs). Hybridization of two ODNs involving threoninol-nucleotides allowed interstrand clustering of the dyes on D-threoninol and greatly stabilized the duplex. When two complementary ODNs, both of which had tethered Methyl Reds on consecutive D-threoninols, were hybridized, the melting temperature increased proportionally to the number of Methyl Reds, due to stacking interactions. Clustering of Methyl Reds induced both hypsochromicity and narrowing of the band, demonstrating that Methyl Reds were axially stacked relative to each other (H-aggregation). Since hybridization lowered the intensity of circular dichroism peaks at the pi-pi* transition region of Methyl Red (300-500 nm), clustered Methyl Reds were scarcely wound in the duplex. Alternate hetero dye clusters could also be prepared only by hybridization of two ODNs with different threoninol-nucleotides, such as Methyl Red-azobenzene and Methyl Red-Naphthyl Red combinations. A combination of Methyl Red and azobenzene induced bathochromic shift and broadening of the band at the Methyl Red region due to the disturbance of exciton interaction among Methyl Reds. But interestingly, the Methyl Red and Naphthyl Red combination induced merging of each absorption band to give a single sharp band, indicating that exciton interaction occurred among the different dyes. Thus, D-threoninol can be a versatile scaffold for introducing functional molecules into DNA for their ordered clustering.     

Crystal structure and luminescence of Sr0.99Eu0.01AlSiN3

Strontium europium aluminum silicon nitride, Sr_0.99Eu_0.01AlSiN₃, was synthesized by heating a mixture of binary nitrides at 2173 K and a N₂ gas pressure of 190 MPa. Single crystals of Sr_0.99Eu_0.01AlSiN₃ approximately 30 μm were obtained. The structure was confirmed to be an isotypic structure of CaAlSiN₃ in the orthorhombic space group Cmc2₁, analyzed by single-crystal X-ray diffraction. The lattice parameters are a=9.843(3), b=5.7603(16), c=5.177(2) Å, cell volume=293.53(17) Å³. It shows an orange-red photoluminescence by 5d→4f transition of Eu²⁺ at around 610 nm under excitation ranging from ultraviolet to 525 nm. The photoluminescence intensity, temperature characteristics, and oxidative stability were comparable or superior to those of CaAlSiN₃:Eu²⁺ phosphor.     

Intramolecular Benzyne–Phenolate [4+2] Cycloadditions

An intramolecular benzyne–phenolate [4+2] cycloaddition is reported. Benzyne precursors, having vicinal halogen-sulfonate functionalities, linked with a phenol(ate) by various tether groups undergo efficient intramolecular [4+2] cycloaddition by treatment with either Ph₃MgLi or nBuLi for halogen–metal exchange to form various benzobarrelenes.     

Cyclohexyl "base pairs" stabilize duplexes and intensify pyrene fluorescence by shielding it from natural base pairs

In this study, we investigated the stability and structure of artificial base pairs that contain cyclohexyl rings. The introduction of a single pair of isopropylcyclohexanes into the middle of DNA slightly destabilized the duplex. Interestingly, as the number of the "base pairs" increased, the duplex was remarkably stabilized. A duplex with six base pairs was even more stable than one containing six A-T pairs. Thermodynamic analysis revealed that changes in entropy and not enthalpy contributed to duplex stability, demonstrating that hydrophobic interactions between isopropyl groups facilitated the base pairing, and thus stabilized the duplex. NOESY of a duplex containing an isopropylcyclohexane-methylcyclohexane pair unambiguously demonstrated its "pairing" in the duplex because distinct NOEs between the protons of cyclohexyl moieties and imino protons of both of the neighboring natural base pairs were observed. CD spectra of duplexes tethering cyclohexyl moieties also showed a positive-negative couplet that is characteristic of the B-form DNA duplex. Taken together, these results showed that cyclohexyl moieties formed base pairs in the DNA duplex without severely disturbing the helical structure of natural DNA. Next, we introduced cyclohexyl base pairs between pyrene and nucleobases as an "insulator" that suppresses electron transfer between them. We found a massive increase in the quantum yield of pyrene due to the efficient shielding of pyrene from nucleobases. The cyclohexyl base pairs reported here have the potential to prepare highly fluorescent labeling agents by multiplying fluorophores and insulators alternately into DNA duplexes.     

Detection of three-base deletion by exciplex formation with perylene derivatives

Here, we synthesized fluorescent DNA probes labeled with two perylene derivatives for the detection of a three-base deletion mutant. One such probe discriminated the three-base deletion mutant from the wild-type sequence by exciplex emission, and the deletion mutant was identifiable even by the naked eye.     

Analysis of Coherent Heteroclustering of Different Dyes by Use of Threoninol Nucleotides for Comparison with the Molecular Exciton Theory

To test the molecular exciton theory for heterodimeric chromophores, various heterodimers and clusters, in which two different dyes were stacked alternately, were prepared by hybridizing two oligodeoxyribonucleotides (ODNs), each of which tethered a different dye on D ‐threoninol at the center of the strand. NMR analyses revealed that two different dyes from each strand were stacked antiparallel to each other in the duplex, and were located adjacent to the 5′‐side of a natural nucleobase. The spectroscopic behavior of these heterodimers was systematically examined as a function of the difference in the wavelength of the dye absorption maxima (Δλ_max). We found that the absorption spectrum of the heterodimer was significantly different from that of the simple sum of each monomeric dye in the single strand. When azobenzene and Methyl Red, which have λ_max at 336 and 480 nm, respectively, in the single strand (Δλ_max=144 nm), were assembled on ODNs, the band derived from azobenzene exhibited a small hyperchromism, whereas the band from Methyl Red showed hypochromism and both bands shifted to a longer wavelength (bathochromism). These hyper‐ and hypochromisms were further enhanced in a heterodimer derived from 4′‐methylthioazobenzene and Methyl Red, which had a much smaller Δλ_max (82 nm; λ_max=398 and 480 nm in the single‐strand, respectively). With a combination of 4′‐dimethylamino‐2‐nitroazobenzene and Methyl Red, which had an even smaller Δλ_max (33 nm), a single sharp absorption band that was apparently different from the sum of the single‐stranded spectra was observed. These changes in the intensity of the absorption band could be explained by the molecular exciton theory, which has been mainly applied to the spectral behavior of H‐ and/or J‐aggregates composed of homo dyes. However, the bathochromic band shifts observed at shorter wavelengths did not agree with the hypsochromism predicted by the theory. Thus, these data experimentally verify the molecular exciton theory of heterodimerization. This coherent coupling among the heterodimers could also partly explain the bathochromicity and hypochromicity that were observed when the dyes were intercalated into the duplex.