Investigation of the crystal structure and the structural and magnetic properties of SrCu2(PO4)2

SrCu2(PO4)2 was prepared by the solid-state method at 1153 K. Its structure was solved by direct methods in the space group Pccn (No. 56) with Z = 8 from synchrotron X-ray powder diffraction data measured at room temperature. Structure parameters were then refined by the Rietveld method to obtain the lattice parameters, a = 7.94217(8) A, b = 15.36918(14) A, and c = 10.37036(10) A. SrCu2(PO4)2 presents a new structure type and is built up from Sr2O16 and Cu1Cu2O8 units with Cu1...Cu2 = 3.256 A. The magnetic properties of SrCu2(PO4)2 were investigated by magnetic susceptibility, magnetization up to 65 T, Cu nuclear quadrupole resonance (NQR), electron-spin resonance, and specific heat measurements. With spin-dimer analysis, it was shown that the two strongest spin-exchange interactions between Cu sites result from the Cu1-O...O-Cu2 and Cu2-O...O-Cu2 super-superexchange paths with Cu1...Cu2 = 5.861 A and Cu2...Cu2 = 5.251 A, and the superexchange associated with the structural dimer Cu1Cu2O8 is negligible. The magnetic susceptibility data were analyzed in terms of a linear four-spin cluster model, Cu1-Cu2-Cu2-Cu1 with -2J(1)/kB = 82.4 K for Cu1-Cu2 and -2J(2)/k(B) = 59 K for Cu2-Cu2. A spin gap deduced from this model (Delta/kB = 63 K) is in agreement with that obtained from the Cu NQR data (Delta/kB = 65 K). A one-half magnetization plateau was observed between approximately 50 and 63 T at 1.3 K. Specific heat data show that SrCu2(PO4)2 does not undergo a long-range magnetic ordering down to 0.45 K. SrCu2(PO4)2 melts incongruently at 1189 K. We also report its vibrational properties studied with Raman spectroscopy.     

Facile Synthesis and Palladium‐Catalyzed Cross‐Coupling Reactions of 2,3‐Bis(pinacolatoboryl)‐1,3‐butadiene

Treatment of 1,1‐bis(pinacolatoboryl)ethene with an excess of 1‐bromo‐1‐lithioethene gave 2,3‐bis(pinacolatoboryl)‐1,3‐butadiene in high yield. Palladium‐catalyzed cross‐coupling of the resulting diborylbutadiene with aryl iodides took place smoothly in the presence of a catalytic amount of Pd(OAc)₂/PPh₃ and aqueous KOH to give 2,3‐diaryl‐1,3‐butadienes in good yields. The coupling reaction with commercially available 4‐acetoxyphenylmethyl chloride under the same conditions followed by hydrolysis of the acetyl groups gave anolignan B in a one‐pot manner. A variety of [3]‐ to [6]dendralenes were synthesized by palladium‐catalyzed coupling of the diene or 1,1‐bis(pinacolato)borylethene with alkenyl or dienyl halides, respectively, in good yields.     

New Synthetic Method for Bicyclic Compounds Through a Sequence of Ene-Type Chlorination,Palladium Catalyzed Dehydrochlorination,and Intramolecular Diels-Alder Reaction

A sequence of ene-type chlorination, palladium catalyzed dehydrochlorination, and the intramolecular Diels-Alder reaction afforded a new method for conversion of prenyl derivatives into bicyclic compounds.     

1,4‐Bis[2‐(4‐ferrocenylphenyl)ethynyl]anthraquinone from synchrotron X‐ray powder diffraction

The title compound, [Fe₂(C₅H₅)₂(C₄₀H₂₂O₂)] or 1,4‐(FcPh)₂Aq [where FcPh is 2‐(4‐ferrocenylphenyl)ethynyl and Aq is anthraquinone], was synthesized in an attempt to obtain a new solvent‐incorporating porous material with a large void space. Thermodynamic data for 1,4‐(FcPh)₂Aq show a phase transition at approximately 430 K. The crystal structure of solvent‐free 1,4‐(FcPh)₂Aq was determined at temperatures of 90, 300 and 500 K using synchrotron powder diffraction data. A direct‐space method using a genetic algorithm was employed for structure solution. Charge densities calculated from observed structure factors by the maximum entropy method were employed for model improvement. The final models were obtained through multistage Rietveld refinements. In both phases, the structures of which differ only subtly, the planar Aq fragments are stacked alternately in opposite orientations, forming a one‐dimensional column. The FcPh arms lie between the stacks and fill the remaining space, leaving no voids. C—H...π interactions between the Ph and Fc fragments mediate crystal packing and stabilization.     

RAFT synthesis of an amphiphilic block copolymer bearing chlorin rings in the hydrophobic segment and its application in photodynamic therapy

RAFT polymerization of styrene (St) in the presence of 5,10,15,20‐tetrakis(pentafluorophenyl)porphyrin (TFPP) was conducted using 4‐cyano‐4‐(thiobenzoyl)thiopentanoic acid as a chain‐transfer agent and azobisisobutyronitrile as an initiator at 60 °C. The resulting polymer exhibited a chlorin‐like UV‐vis spectrum, which indicated that the polymer possessed a reduced TFPP structure. Furthermore, an SEC trace recorded using UV‐vis detector (λ = 410 nm), which selectively detected the TFPP‐incorporated polymer, shifted toward higher molecular mass as the polymerization progressed. This evidence indicated that TFPP acted as a vinylene‐type monomer, such as maleimide, to form a copolymer, namely, poly(St‐co‐TFPP). The mole fraction of TFPP units was estimated to be 0.74 × 10^?3, which was close to that in the feed (1 × 10^?3). Chain extension of poly(St‐co‐TFPP) with polyethylene glycol monomethyl ether acrylate (PEGA) was performed to afford the amphiphilic block copolymer poly(St‐co‐TFPP)‐b‐poly(PEGA). The degrees of polymerization of St and PEGA were determined to be 64 and 75, respectively. Poly(St‐co‐TFPP)‐b‐poly(PEGA) formed micelles following dialysis. The median diameter of the micelles in solution was determined to be 16 nm by DLS. The photocytotoxicity of the micelle solution was evaluated in a human glioblastoma cell line (U251) and an N‐methyl‐N'‐nitro‐N‐nitrosoguanidine‐induced mutant of a rat murine RGM‐1 gastric carcinoma mucosal cell line (RGK‐1). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3395–3403     

5,11-Diazadibenzo[hi,qr]tetracene: Synthesis,Properties, and Reactivity toward Nucleophilic Reagents

5,11-Diazadibenzo[hi,qr]tetracene was synthesized as a new nitrogen-substituted polycyclic heteroaromatic compound by Pd-catalyzed cycloisomerization of an alkyne precursor followed by oxidative cyclization with bis(trifluoroacetoxy)iodobenzene. The substitution of imine-type nitrogen atoms significantly enhanced its electron-accepting character and facilitated the direct nucleophilic addition of arylamines under strongly basic conditions to afford the desired amino-substituted products. The introduction of amino groups induced a remarkable red-shift in their absorption spectra; the tetrasubstituted product exhibited intense near-infrared absorbing property. Furthermore, the π-electronic system, which includes a redox-active 1,4-diazabutadiene moiety, underwent reversible interconversion to its corresponding reduced form upon reduction with NaBH₄ and aerobic oxidation.     

Synthesis and crosslinking reaction of a novel polymer containing benzoxazine and phenyleneethynylene moieties in the main chain

A novel polymer, poly( 1 ) containing benzoxazine and phenyleneethynylene moieties in the main chain with number‐average molecular weights ranging from 1400 to 9800 was obtained quantitatively by the Sonogashira–Hagihara coupling polymerization of the corresponding iodophenyl‐ and ethynylphenyl‐substituted monomer 1 . Poly( 1 ) was heated at 200 °C under N₂ for 2 h to obtain the cured polymer, poly( 1 )′ via the ring‐opening polymerization of the benzoxazine moieties. The structures of the polymer before and after curing were confirmed by ¹H‐NMR, IR, and UV–vis absorption and reflectance spectroscopies. Poly( 1 )′ was thermally more stable than monomer 1 and poly( 1 ). A specimen was prepared from a mixture of poly( 1 ) and phenol‐diaminodiphenylmethane type benzoxazine 2 by heating at 200 °C for 2 h under N₂. The poly( 1 )/ 2 resin was thermally stable than bisphenol‐A type benzoxazine resin 3 . Poly( 1 ) exhibited XRD peaks corresponding to the d‐spacings of 1.26–0.98 and 0.40 nm, assignable to the repeating monomer unit and alignment of polymer molecules, respectively. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2581–2589     

Enhancement of Photocatalytic Activity for Hydrogen Production by Surface Modification of Pt-TiO2 Nanoparticles with a Double Layer of Photosensitizers

To investigate the effect of the surface structure of dye-sensitized photocatalyst nanoparticles, we prepared three types of Ru^II-photosensitizer (PS)-double-layered Pt-cocatalyst-loaded TiO₂ nanoparticles with different surface structures, Zr- RuCP⁶ -Zr- RuP⁶ @N wt %Pt-TiO₂, RuCP⁶ -Zr- RuP⁶ @N wt %Pt-TiO₂, and RuCP² -Zr- RuP⁶ @N wt %Pt-TiO₂ (N=0.2, 1, and 5), and evaluated their photocatalytic H₂ evolution activity in the presence of redox-reversible iodide as the electron donor. Although the driving force of the electron injection from I⁻ to the photo-oxidized Ru^III PS is comparable, the activity increased in the following order: RuCP² -Zr- RuP⁶ @1 wt %Pt-TiO₂ < RuCP⁶ -Zr- RuP⁶ @1 wt %Pt-TiO₂ < Zr- RuCP⁶ -Zr- RuP⁶ @1 wt %Pt-TiO₂. The apparent quantum yield of Zr- RuCP⁶ -Zr- RuP⁶ @1 wt %Pt-TiO₂ in the first hour reached 1 %. Zeta-potential measurements suggest that the surface Zr⁴⁺-phosphate groups attracted I⁻ anions to the nanoparticle–solution interface. Our results indicate that the surface modification of dye-sensitized photocatalysts is a promising approach to enhance photocatalytic activity with various redox mediators.     

Reversible and Stepwise Single-Crystal-to-Single-Crystal Transformation of a Platinum(II) Complex with Vapochromic Luminescence

The vapochromic single-crystal-to-single-crystal (SCSC) transformation of a highly luminescent Pt^II complex bearing an N-heterocyclic carbene [Pt(CN)₂(tBu-impy)] (tBu-impyH⁺=1-tert-butyl-3-(2-pyridyl)-1H-imidazolium) is reported. The trihydrate form of the complex, which exhibits blue ³MMLCT emission owing to weak Pt⋅⋅⋅Pt interactions, changed its luminescence color from blue to yellowish-green upon the desorption of water molecules while keeping the high emission quantum yield of more than 0.45. Variable-temperature and continuous in-situ tracking of single-crystal X-ray diffraction measurements revealed that the SCSC transformation proceeds reversibly by the release and reabsorption of water molecules, thereby changing the stacked structure slightly. As a result, the dynamics of vapor-induced SCSC transformation were elucidated: that the anhydrous form returned to the original trihydrate form in a two-step process under a water vapor atmosphere. In addition, the Pt^II complex exhibited a similar SCSC response accompanied by a luminescence color change in the presence of methanol vapor, while being inactive toward ethanol vapor.