A carboranylpentaphenylbenzene

1-(o-Carboran-9-yl)-2,3,4,5,6-pentaphenylbenzene (1) was prepared by the Diels-Alder reaction of 9-phenylethynyl-o-carborane and tetraphenylcyclopentadienone at 300 °C. An X-ray crystal structure of 1 shows that the steric demands of the carborane induce a significant stretching of the aryl carbon-boron bond as well as a variety of distortions of the central benzene ring, the ortho phenyl groups, and the carborane cage.     

Sequential Multistep Excited-State Structural Transformations in N,N′-Diphenyl-dihydrodibenzo[a,c]phenazine Fluorophores

We demonstrate that a single polycyclic π-scaffold can undergo sequential multistep excited-state structural evolution along the bent, planar, and twisted conformers, which coexist to produce intrinsic multiple fluorescence emissions in room-temperature solution. By installing a methyl or trifluoromethyl group on the ortho-site of N,N′-diphenyl-dihydrodibenzo[a,c]phenazine ( DPAC ), the enhanced steric effects change the fluorescence emission of DPAC from a dominant red band to well-resolved triple bands. The ultra-broadband triple emissions of ortho-substituted DPAC s range from ≈350 to ≈850 nm, which is unprecedented for small fluorophores with molecular weight of <500. Ultrafast spectroscopy and theoretical calculations clearly reveal that the above dramatic changes originate from the influence of steric hindrance on the shape of excited state potential energy surface (S₁ PES). Compared to the steep S₁ PES of parental DPAC , the introduction of ortho-substituent is shown to make the path of structural evolution in S₁ wider and flatter, so the ortho-substituted derivatives exhibit slower structural transformations from bent to planar and then to twisted forms, yielding intrinsic triple emission. The results provide the proof of concept that the bent, planar, and twisted emissive states can coexist in the same S₁ PES, which greatly expand the fundamental understanding of the excited-state structural relaxation.     

A Novel Initiator Containing Alkyne Group for the Polymerization of 2-Ethyl-2-oxazoline

A novel trifunctional initiator with one alkyne and two trifluoromethanesulfonate moieties was synthesized from a protected alcohol 5-hydroxyl-2-phenyl-1, 3-dioxane. The alkyne functionalized intermediate with two protected alcohol groups was synthesized by reacting with propargyl bromide. The alcohol groups were cleaved using a mixture of tetrahydrofuran and hydrochloric acid aqueous solution. In the last step the initiator was synthesized using triflic anhydride in carbon tetrachloride. The initiator was characterized by ¹H NMR and used for the polymerization of 2-ethyl-2-oxazoline which gives polymers with narrow distribution. For comparison a similar initiator with two tosylates was prepared and used for the polymerization of the monomer 2-ethyl-2-oxazoline, the resulting product has a wide molecular weight distribution and most of the initiator remains unreacted after 24 h which may be due to the steric hindrance between the two tosylate groups. To further explore the steric hindrance phenomenon, a linear tosylate initiator was synthesized, but still some of the initiator remains unreacted, illustrating that both steric hindrance and electrophilic balance affect the efficiency of the cationic ring-opening polymerization. All of the polymers were characterized in detail by using ¹H NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy, and size exclusion chromatography to confirm the purity and distribution of the polymers.     

2，3－二氰基－2，3－二（X－取代苯基）丁二酸二乙酯在苯乙烯中的分解动力学研究

２，３－二氰基－２，３－二（Ｘ－取代苯基）丁二酸二乙酯在苯乙烯中的分解动力学研究齐陈泽，吴靖嘉，段大勇，贾志胜，张斌，杨第伦（兰州大学应用有机化学国家重点实验室，兰州大学化学系，兰州，７３００００）关键词２，３－二氰基－２，３－二（Ｘ－取代苯基）丁二...     

Stereochemistry and reactivity of the HPA-imine Mannich intermediate

Homophthalic anhydride (HPA) typically reacts rapidly with benzalimines to afford the formal [4+2] adduct, a 1,2,3,4-tetrahydroisoquinolin-1-one-4-carboxylic acid. The stereochemical outcome of this reaction is consistent with an open transition state comprising an iminium species and enolized HPA, leading to a short-lived amino-anhydride intermediate. In the case of N-tert-butylbenzalimine, this Mannich-type intermediate, which would normally cyclize at low temperature to a single isomer of the delta-lactam, is intercepted by base treatment to afford beta-lactam products. A pathway featuring ketene formation followed by ring closure is implicated.     

Complexes based on ferrocenecarboxylate ligands: steric hindrance induced by ferrocenyl groups

Three metal complexes with ferrocenecarboxylate ligands, [M₂(η ²-FcCOO)₂(μ₂-η ²-FcCONHCH₂COO)₂(phen)₂]?·?nH₂O [M?=?Pb, n?=?6 (1) and M?=?Cd, n?=?2 (2)] and [Cd(FcCONHCH₂COO)(μ₂-FcCONHCH₂COO)(2,2′-bipy)(H₂O)] _n (3) (FcCOOH?=?ferrocenemonocarboxylic acid, FcCONHCH₂COOH?=?N-ferrocenylformylglycine, phen?=?1,10-phenanthroline, 2,2′-biby?=?2,2′-bipyridine), were synthesized and characterized by elemental analysis, IR, and single crystal X-ray diffraction analysis. Structural studies revealed that 1 and 2 have similar binuclear structures, but 3 exhibits a 1-D chain structure. The difference in the structures of ferrocenylcarboxylate-containing cadmium(II) complexes is due to steric hindrance of ferrocenyl groups.     

Deuteration of molecules for neutron reflectometry on organic light-emitting diode thin films

Deuterated forms of aromatic charge transporting heterocycles 2 and 3 used in organic light-emitting diodes have been produced by hydrothermal reactions, catalyzed by Pt/C or Pd/C. Comprehensive analysis by mass spectroscopy, ¹H, ²H and ¹³C NMR enables determination of the overall quantity of D atoms present, as well as the level of deuteration at each molecular site. The roles of solubility and steric availability in deuteration are discussed in the light of these results. Neutron reflectometry indicates excellent scattering contrast between protonated and deuterated forms of these molecules, with nanoscale thin films showing the same density as in their bulk molecular forms. Although used for morphological studies of thin films typically used in OLEDs, the synthetic and analysis methods described here are generic and suitable for deuteration of other conjugated aromatic heterocycles and other optoelectronic devices.     

硫酸介质中控制碳钢腐蚀的烷基取代Piperidin-4-one Oximes的立体效应

Three synthesized piperidin-4-one oximes,3-ethyl-2,6-diphenyl-piperidin-4-one oxime(A),1-methyl-3-isopropyl-2,6-diphenyl-piperidin-4-one oxime(B),and 3-isopropyl-2,6-diphenyl-piperidin-4-one oxime(C),were tested at different concentrations to determine their ability to inhibit corrosion of mild steel in 1 mol.L-1 H2SO4 and measured by a mass loss method(at various temperatures),polarization and impedance measurements,X-ray diffraction(XRD),scanning electron microscopy(SEM) with energy-dispersive X-ray spectroscopy(EDS),and a quantum chemical method.The synergistic influence of compounds A,B and C with iodides has also been evaluated.All three compounds show good inhibition efficiency in the following order:A>B>C.Compounds A,B and C were found to physically adsorb on the surface of mild steel while obeying the Temkin isotherm.Polarization measurements indicated that these compounds behave as a mixed mode inhibitor.XRD and SEM with EDS studies revealed the formation of a protective barrier on the mild steel surface by these oximes.The electron donating ability of the studied molecules was tested using semi empirical methods.The studies revealed that the oxime nitrogen,the piperidine moiety,and the phenyl ring assist largely in corrosion control.The studies also showed that the steric crowding by the alkyl group in the piperidine ring affects the inhibitor efficiency.Further,it is interesting to note that all of the studied compounds exhibit synergism with iodide ions.     

Distinction of Push,pull effect and steric hindrance in disubstituted alkynes

The push,pull effect in two series of disubstituted alkynes was studied at the DFT level [B3LYP/6-311G(d)] by application of the ¹³C chemical shift differences (GIAO) between the alkyne carbon atoms (Δδ_CC), the charge difference between these carbons (Δq_CC), the occupation quotient (NBO) of anti-bonding π^∗, and bonding π orbitals (π^∗_CC/π_CC) and the bond length (d_CC) of the CC triple bond. The linear dependence of d_CC versus π^∗_CC/π_CC quantifies changes in the push,pull effect while deviations from the latter correlation indicate and ascertain quantitatively to what extent steric hindrance restricts the strain-less conjugation of the CC triple bond π-orbitals in the disubstituted alkynes.