超短脉冲强激光与固体靶相互作用中Kα射线的实验研究

在相对论激光强度下，对p偏振30 fs激光与固体Cu靶相互作用中产生的Kα射线进行了实验研究.采用刀边成像技术和单光子计数X射线CCD相结合的探测装置，在单发激光脉冲打靶时同时得到X射线源的尺寸、能谱以及Kα光子的转换效率等多种信息.实验结果与Reich等人的理论计算结果有明显的差异，Kα光子的能量转换效率在激光功率密度为1.6×10¹⁸W/cm²的条件下达到最大值7.08×10^-6/sr.根据这一结果并结合蒙特卡罗程序，推断出在这一聚焦光强下激光能量转换为前向超热电子的效率约为10%.     

Highly Pure Synthesis,Spectral Assignments,and Two‐Photon Properties of Cruciform Porphyrin Pentamers Fused with Benzene Units

Tetrameric porphyrin formation of 2‐hydroxymethylpyrrole fused with porphyrins through a bicyclo[2.2.2]octadiene unit gave bicyclo[2.2.2]octadiene‐fused porphyrin pentamers. Thermal conversion of the pentamers gave fully π‐conjugated cruciform porphyrin pentamers fused with benzene units in quantitative yields. UV/Vis spectra of fully π‐conjugated porphyrin pentamers showed one very strong Q absorption and were quite different from those of usual porphyrins. From TD‐DFT calculations, the HOMO level is 0.49 eV higher than the HOMO?1 level. The LUMO and LUMO+1 levels are very close and are lower by more than 0.27 eV than those of other unoccupied MOs. The strong Q absorption was interpreted as two mutually orthogonal single‐electron transitions (683 nm: 86 %, HOMO→LUMO; 680 nm: 86 %, HOMO→LUMO+1). The two‐photon absorption (TPA) cross section value (σ⁽²⁾) of the benzene‐fused porphyrin pentamer was estimated to be 3900 GM at 1500 nm, which is strongly correlated with a cruciform molecular structure with multidirectional π‐conjugation pathways.     

A platinum-ruthenium dinuclear complex bridged by bis(terpyridyl)xanthene

4,5-Bis(terpyridyl)-2,7-di-tert-butyl-9,9-dimethylxanthene (btpyxa) was prepared to serve as a new bridging ligand via Suzuki coupling of terpyridin-4'-yl triflate and 2,7-di-tert-butyl-9,9-dimethylxanthene-4,5-diboronic acid. The reaction of btpyxa with either 1 equiv or an excess of PtCl(2)(cod) (cod = 1,5-cyclooctadiene) followed by anion exchange afforded mono- and dinuclear platinum complexes [(PtCl)(btpyxa)](PF(6)) ([1](PF(6))) and [(PtCl)(2)(btpyxa)](PF(6))(2) ([2](PF(6))(2)), respectively. The X-ray crystallography of [1](PF(6)).CHCl(3) revealed that the two terpyridine units in the ligand are nearly parallel to each other. The heterodinuclear complex [(PtCl)[Ru((t)Bu(2)SQ)(dmso)](btpyxa)](PF(6))(2) ([4](PF(6))(2)) (dmso = dimethyl sulfoxide; (t)Bu(2)SQ = 3,5-di-tert-butyl-1,2-benzosemiquinone) and the monoruthenium complex [Ru((t)Bu(2)SQ)(dmso)(trpy)](PF(6)) ([5](PF(6))) (trpy = 2,2':6',2' '-terpyridine) were also synthesized. The CV of [2](2+) suggests possible electronic interaction between the two Pt(trpy) groups, whereas such an electronic interaction was not suggested by the CV of [4](2+) between Pt(trpy) and Ru((t)Bu(2)SQ) frameworks.     

Syntheses, properties, and photoreactions of the hybrid molecules consisting of a Co(II) mononuclear complex and porphyrins

New hybrid molecules consisting of mononuclear Co(II) complexes and porphyrin moieties were synthesized and their new photoreactions were examined. Three porphyrins with different meso-substituents (2,6-dimethoxyphenyl, 3,5-di-tert-butylphenyl, and 2,6-difluorophenyl groups) were used to change the redox potentials of the hybrid compounds. The hybrid molecules were prepared by the stepwise condensation of amide bonds. The cyclic voltammograms of these hybrid molecules showed the redox processes of both the cobalt and porphyrin moieties. The redox potentials of the porphyrins showed a systematic change that was consistent with the electronic effects of the meso-substituents. The emission spectra only showed fluorescence of the porphyrins with slightly decreased intensities. When a solution of the hybrid molecule, durohydroquinone, and N,N-diisopropylethylamine in CHCl(3)/MeCN was irradiated with visible light (>580 nm), durohydroquinone was converted into duroquinone with the concurrent formation of the reduced product of CHCl(3). The hydroquinone was employed as an electron donor capable of reversible redox reactions, which is in contrast to conventional sacrificial reagents such as EDTA. The course of the photoreaction was followed by (1)H NMR spectroscopy and the amount of produced duroquinone was between 50-60% after 600 min. We propose that the photoreaction involves a photoinduced electron transfer from the hydroquinone to the excited porphyrin, followed by the formation of a Co(I) intermediate by charge shift, thus leading to the reaction with CHCl(3).     

Substituent effects on core structures and heterogeneous catalytic activities of Mn(III)(μ-O)2Mn(IV) dimers with 2,2':6',2″-terpyridine derivative ligands for water oxidation

[(OH(2))(R-terpy)Mn(μ-O)(2)Mn(R-terpy)(OH(2)) ](3+) (R-terpy = 4'-substituted 2,2':6',2″-terpyridine, R = butoxy (BuO), propoxy (PrO), ethoxy (EtO), methoxy (MeO), methyl (Me), methylthio (MeS), chloro (Cl)) have been synthesized as a functional oxygen-evolving complex (OEC) model and characterized by UV-vis and IR spectroscopic, X-ray crystallographic, magnetometric, and electrochemical techniques. The UV-vis spectra of derivatives in water were hardly influenced by the 4'-substituent variation. X-ray crystallographic data showed that Mn centers in the Mn(III)(μ-O)(2)Mn(IV) cores for derivatives with R = H, MeS, Me, EtO, and BuO are crystallographically indistinguishable, whereas the derivatives with R = MeO and PrO gave the significantly distinguishable Mn centers in the cores. The indistinguishable Mn centers could be caused by rapid electron exchange between the Mn centers to result in the delocalized Mn(μ-O)(2)Mn core. The exchange integral values (J = -196 to -178 cm(-1)) for delocalized cores were lower than that (J = -163 to -161 cm(-1)) for localized cores, though the Mn···Mn distances are nearly the same (2.707-2.750 ?). The half wave potential (E(1/2)) of a Mn(III)-Mn(IV)/Mn(IV)-Mn(IV) pair of the derivatives decreased with an increase of the electron-donating ability of the substituted groups for the delocalized core, but it deviated from the correlation for the localized cores. The catalytic activities of the derivatives on mica for heterogeneous water oxidation were remarkably changed by the substituted groups. The second order rate constant (k(2)/mol(-1) s(-1)) for O(2) evolution was indicated to be correlated to E(1/2) of a Mn(III)-Mn(IV)/Mn(IV)-Mn(IV) pair; k(2) increased by a factor of 29 as E(1/2) increased by 28 mV.     

Fabrication of Microspheres from Phthalimide‐Substituted Porphyrin Derivatives

Microspheres were fabricated from phthalimide‐substituted porphyrin derivatives. Microscopic analysis showed that the structures of the supramolecular assemblies synthesized in the present study were spherical, with diameters in the sub‐micrometer to micrometer range. The size of the microspheres could be controlled by changing the concentration of the casting solution. The spectroscopic properties of the microspheres were measured to determine the influence of their structural components. Thermal studies indicated that the temperature at which these structures became unstable was lower than the bulk melting point. During I–V measurements on devices composed of these microspheres, it was found that the current increased upon light irradiation, and the characteristic photoresponse properties of these devices were reproducible.