Allyl phenyl ether has an absorption band in the ultraviolet region (λ < 400 nm); therefore, irradiation with few-optical-cycle ultraviolet pulses (λ = 360-440 nm) causes a transition to the ultraviolet band, which leads to an electronic state and a photo-Claisen rearrangement (radical reaction) in the electronic excited state. However, the reaction scheme of allyl phenyl ether under irradiation with few-optical-cycle visible pulses (λ = 525-725 nm) was determined to be same as that of the thermal Claisen rearrangement ([3,3]-sigmatropic rearrangement), which is symmetry-allowed in the electronic ground state. Photo-excitation with few-optical cycle visible pulses below the absorption band induces a photo-impulsive reaction in the electronic ground state without electronic excitation, of which the trigger scheme is different from that of photoreaction or thermal-reaction. The photo-impulsive reaction in the electronic ground state is highly possible as a novel reaction scheme. 相似文献
A novel supramolecular complex [Ag(L)(NO(3))] (1) was synthesized by reaction of the oxazoline-containing ligand 1,4-bis(4,5-dihydro-2-oxazolyl)benzene (L) with silver(I) nitrate and its structure was determined by single-crystal X-ray diffraction. Structurally speaking, the one-dimensional (1D) zigzag chains of 1, in which the Ag(I) is three-coordinated with distorted trigonal-planar coordination geometry, are linked together by the hydrogen bonding interactions to form a three-dimensional (3D) supramolecular structure. It was found that the silver supramolecule 1 catalyzes the three-component coupling reactions of aldehyde, alkyne, and amine in the air at room temperature to generate propargylic amines with high efficiency. No additional co-catalyst or activator is required. A variety of aldehydes and amines were used to demonstrate the versatility of the reaction. 相似文献
Silicon oxide films are deposited in atmospheric-pressure (AP) He/O2/HMDSO plasma excited by a 150?MHz VHF power using a cylindrical rotary electrode. The atomic bonding configurations and deposition rate are studied by controlling the O2 concentration (O2/HMDSO source ratio) and VHF power density, the other parameters being maintained constant. Under the addition of 0.03?% O2 to the process gas mixture (O2/HMDSO????0.09), AP-VHF plasma greatly enhances the fragmentation and oxidation of HMDSO, so that an almost inorganic film is obtained at a very high deposition rate of 33?nm?s?1. A silicon oxide coating on a polycarbonate pane is demonstrated with no significant thermal deformation of the pane, showing that AP-VHF plasma would be an efficient coating tool for polymer substrates. 相似文献
Highlights? CPYPP binds to DOCK2 DHR-2 domain and inhibits its catalytic activity ? CPYPP inhibits DOCK2-mediated Rac activation in cells ? The structural features of CPYPP required for its inhibitory effect were revealed ? CPYPP inhibits lymphocyte migration and activation in vitro and in vivo 相似文献
Let k≥2 be an integer and G = (V(G), E(G)) be a k-edge-connected graph. For X⊆V(G), e(X) denotes the number of edges between X and V(G) − X. Let {si, ti}⊆Xi⊆V(G) (i=1,2) and X1∩X2=∅. We here prove that if k is even and e(Xi)≤2k−1 (i=1,2), then there exist paths P1 and P2 such that Pi joins si and ti, V(Pi)⊆Xi (i=1,2) and G − E(P1∪P2) is (k−2)-edge-connected (for odd k, if e(X1)≤2k−2 and e(X2)≤2k−1, then the same result holds [10]), and we give a generalization of this result and some other results about paths not containing
given edges. 相似文献
The RNA‐world hypothesis assumes that life on Earth started with small RNA molecules that catalyzed their own formation. Vital to this hypothesis is the need for prebiotic routes towards RNA. Contemporary RNA, however, is not only constructed from the four canonical nucleobases (A, C, G, and U), it also contains many chemically modified (noncanonical) bases. A still open question is whether these noncanonical bases were formed in parallel to the canonical bases (chemical origin) or later, when life demanded higher functional diversity (biological origin). Here we show that isocyanates in combination with sodium nitrite establish methylating and carbamoylating reactivity compatible with early Earth conditions. These reactions lead to the formation of methylated and amino acid modified nucleosides that are still extant. Our data provide a plausible scenario for the chemical origin of certain noncanonical bases, which suggests that they are fossils of an early Earth. 相似文献
Fork ≥ 2 andα = 0, 1, every (4k + 2α)-edge-connected graph is weakly (3k + 2α)-linked.
IfG is ak-edge-connected graph (k ≥ 2),s, t are vertices andf is an edge, then there exists a pathP betweens andt such thatf ? E(P) andG ? E(P) ? f is (k ? 2)-edge-connected, whereE(P) denotes the edge set ofP.
A neutral tetradentate ligand L1 [L1?=?3,6-bis(pyrazol-1-yl)-pyridazine] reacts with Ni(ClO4)2·6H2O and undergoes counterion exchange with PF?6 to give di- and tetranuclear complexes [Ni2(L1)2(CH3CN)4](PF6)4·4H2O (1) and [Ni4(L1)4(µ-OH)4](ClO4)4·2H2O (2), respectively. The presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as base controls the nuclearity of the complex formation. Both complexes were structurally characterized by physicochemical and spectroscopic techniques. Their crystal structures revealed that both complexes are centrosymmetric and adopt slightly distorted octahedral geometry. Complex 1 crystallizes in monoclinic space group C2/c as the Ni(II) center is octahedrally bound to L1 in a trans-isomer arrangement. Complex 2 crystallizes in tetragonal space group I41/amd with four L1 and four hydroxy bridging ligands linked to Ni(II) center in cis-isomer arrangement. Cyclic voltammograms of complexes 1 and 2 were measured under Ar and CO2. Under CO2, the quasireversible peaks of both complexes become irreversible and a current enhancement occurs under reduction.