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141.
p-Polyphenyl-α,ω-quinododimethides were predicted to be moderately aromatic and diatropic, although they exist only in a single
classical resonance structure with no aromatic conjugated circuits. Such a dichotomy was resolved using our graph theory of
aromaticity and ring-current diamagnetism. Six-site non-conjugated circuits were found to contribute appreciably to aromaticity
and ring-current diamagnetism. Within each quinododimethide molecule, local aromaticity increases on going from the outermost
to inner phenylene rings. 相似文献
142.
Thioacetals were found to be effective precursors to generate and accumulate alkoxycarbenium ions based on direct and indirect cation pool methods. Alkoxycarbenium ions thus generated reacted with carbon nucleophiles such as allylsilanes and enol silyl ethers to give C-C bond formation products in good yields. 相似文献
143.
Naraso Nishida J Kumaki D Tokito S Yamashita Y 《Journal of the American Chemical Society》2006,128(30):9598-9599
The first n-type FET based on TTF derivatives was prepared. TTF derivatives with halogeno-substituted quinoxaline rings showed excellent n- or p-type performances with high carrier mobilities. Introduction of halogen groups determined the FET polarity by controlling the HOMO and LUMO levels of the molecules. The pi-stacking structures were observed in the single crystals of tetrahalogeno-TTFs. 相似文献
144.
Yamada M Hagiwara H Torigoe H Matsumoto N Kojima M Dahan F Tuchagues JP Re N Iijima S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(17):4536-4549
A family of spin-crossover (SC) complexes, [Fe(II)H(3)L(Me)]Cl.X (X(-) = PF(6) (-), AsF(6) (-), SbF(6) (-), CF(3)SO(3) (-)), 1-4, has been synthesized, in which H(3)L(Me) denotes the hexadentate N(6) tripod-like ligand tris[2-{[(2-methylimidazol-4-yl)methylidene]amino}ethyl]amine, containing three imidazole groups, with a view to establishing the effect of the counter anion on the SC behavior. These complexes have been found to crystallize in the same monoclinic crystal system with similar cell dimensions. The general crystal structure consists of a two-dimensional (2D) extended network constructed by NH...Cl- hydrogen bonds between Cl- and the imidazole NH groups of three neighboring [Fe(II)H(3)L(Me)]2+ ions, while the anion X exists as an isolated counter anion and occupies the space between the 2D sheets. Magnetic susceptibilities and M?ssbauer spectra have revealed a variety of SC behaviors depending on the counter anion, including a one-step HS<==>(HS + LS)/2 (1, X = PF(6) (-)), a two-step HS<==>(HS + LS)/2<==>LS with a slow thermal relaxation (2, X = AsF(6) (-)), a gradual one-step HS<==>LS (3, X = SbF(6) (-)), and a steep one-step HS<==>LS with hysteresis (4, X = CF(3)SO(3) (-)). The complexes assume the space group P2(1)/n in the HS state, P2(1) in the HS + LS state, and P2(1)/n in the LS state. The Fe-N bond lengths and the N-Fe-N bond angles are indicative of the HS, HS + LS, and LS states. The molecular volumes, V, of the counter anions have been evaluated by quantum-chemical calculations as follows: 53.4 A(3) (BF(4) (-)), 54.4 A(3) (ClO(4) (-)), 73.0 A(3) (PF(6) (-)), 78.5 A(3) (AsF(6) (-)), 88.7 A(3) (SbF(6) (-)), and 86.9 A(3) (CF(3)SO(3) (-)). The size and shape of the counter anion affects the flexible 2D network structure constructed by the hydrogen bonds, leading to modifications of the SC behavior. These estimated relative sizes of the counter anions correlate well with the observed SC behaviors. 相似文献
145.
Quan HJ Koyanagi J Hagiwara K Cui XR Isshiki Y Kondo S Komada F Saito S 《Chemical & pharmaceutical bulletin》2006,54(1):72-79
26-Iodopseudodiosgenin (8) and 26-iodopseudodiosgenone (9) were reacted with various nucleophiles (KSCN, KOCN, NaCN, NaN(3) and various amines) to give pseudodiosgenin derivatives (4, 12, 16-20, 26) and pseudodiosgenone derivatives (5, 13, 21-25, 27), respectively. The reactions of 8 and 9 with KOCN gave the elimination products (10) and (11), respectively. The reaction of 9 with NaCN gave 5alpha,26- (14) and 5beta,26-dicyanocholestan-3-one (15). The reaction of 8 with NaN3 gave triazepine derivative (30), while that of 9 gave 26-azidopseudodiosgenone (31). Compound 31 was converted into triazepine derivative (32) by heating at 120 degrees C. The cytotoxicity of the pseudodiosgenins and pseudodiosgenones on P-gp-underexpressing HCT 116 cells and P-gp-overexpressing Hep G2 cells was examined by MTT assay. Pseudodiosgenins 2, 4, 12 and 30 showed strong cytotoxic activity (IC50 values: 2.6+/-0.3-6.7+/-1.4 microM), as did pseudodiosgenones 3, 5, 11, 13, 21-25 and 27 (IC50 values: 1.3+/-0.3-6.4+/-0.3 microM) toward HCT 116 cells. Pseudodiosgenins 12, 16 and 30 (IC50 values: 1.2+/-0.7-2.2+/-0.6 microM) and pseudodiosgenones 22, 23, 25 and 27 (IC50 values: 0.6+/-0.1-2.5+/-0.3 microM) were highly cytotoxic to Hep G2 cells. Compounds 3 and 27 showed efficient antibacterial activity (MIC: 15.6, 10.4 microg/ml) and (MIC: 7.8, 15.6 microg/ml) against Bacillus subtilis and Staphylococcus aureus, respectively. 相似文献
146.
Suga S Matsumoto K Ueoka K Yoshida J 《Journal of the American Chemical Society》2006,128(24):7710-7711
A sequential one-pot indirect cation pool method has been developed. The method involves the electrochemical generation and accumulation of ArS(ArSSAr)+ at low temperature (step 1) and the follow-up reaction with a thioacetal to generate an alkoxycarbenium ion pool (step 2), which reacts with various carbon nucleophiles (step 3). Steps 2 and 3 are extremely fast. The electrogenerated ArS(ArSSAr)+ was well-characterized by 1H NMR and CSI-MS. The alkoxycarbenium ion pool generated by the present indirect method exhibited 1H and 13C NMR spectra and thermal stability similar to those of the alkoxycarbenium ion pool generated by the direct electrochemical method. 相似文献
147.
Aihara J 《Journal of the American Chemical Society》2006,128(9):2873-2879
Energetic and magnetic criteria of aromaticity are different in nature and sometimes make different predictions as to the aromaticity of a polycyclic pi-system. Thus, some charged polycyclic pi-systems are aromatic but paratropic. We derived the individual circuit contributions to aromaticity from the magnetic response of a polycyclic pi-system and named them circuit resonance energies (CREs). Each CRE has the same sign and essentially the same magnitude as the corresponding cyclic conjugation energy (CCE) defined by Bosanac and Gutman. Such CREs were found to play a crucial role in associating the energetic criteria for determining the degree of aromaticity with the magnetic ones. We can now interpret both energetic and magnetic criteria of aromaticity consistently in terms of CREs. Ring-current diamagnetism proved to be the tendency of a cyclic pi-system to retain aromatic stabilization energy (ASE) at the level of individual circuits. 相似文献
148.
A new BEDT-TTF-based salt with an organic free radical TEMPO has been prepared. The salt consists of alternate layers of conducting and magnetic sheets, between which are short S(BEDT-TTF) …O(TEMPO) contacts. The magnetic susceptibility is well modelled by the combination of a 2D Heisenberg and a Curie-Weiss model with and . 相似文献
149.
Jun-ichi Nishizawa Tetsuo Sasaki Tadao Tanabe Takenori Tanno 《Applied Surface Science》2006,252(12):4226-4229
Terahertz (THz) dichroism of a nematic liquid N-(p-methoxybenzylidene)-p-butylaniline (MBBA) was measured using a GaP Raman THz spectrometer. MBBA on a rubbed plastic substrate generates a band at around 4.0 THz: its liquid crystal phase shows strong dichroism, which well corresponds to that of the IR absorption caused by π(CH) of MBBA molecule reported in the literature. Based on inferences drawn from the present THz and the published IR dichroic results, the 4.0 THz band probably stems from lateral intermolecular or intramolecular interactions of MBBA molecules aligned to the rubbing direction. The results clearly demonstrate that THz spectroscopy is powerful for discussing of phase transition and dichroism of liquid crystals. 相似文献
150.
Zlatko?ErjavecEmail authorView authors OrcID profile Jun-ichi?Inoguchi 《Mathematical Physics, Analysis and Geometry》2018,21(2):15
We determine magnetic curves corresponding to the Killing magnetic fields in the 3-dimensional homogenous Riemannian space Sol3. 相似文献