Characterization of C18 chemically modified silica-gel and porous glass phases by high resolution solid state NMR spectroscopy and other physico-chemical methods

Summary Two types of packing materials, porous glass (PG) and silica gel (SG) have been modified by mono- and difunctional octadecylchlorosilane. The packing surfaces before and after chemical modification have been characterized by CP/MAS NMR, SIMS, porosimetrical, elemental and chromatographic methods. On the basis of the physico-chemical and chromatographic data the PG and SG (of similar porosity) used as supports of chemically bonded phases for RP HPLC, have been compared. Presented at 13th Symposium on Column Liquid Chromatography, Stockholm, June 25–30, 1989.     

Photochemical formation of nonlinear optical and photorefractive image in polymer layer

The paper is devoted to the development of the light-sensitive layers in which the image with nonlinear optical (NLO), photoelectric and photorefractive (PR) properties arises as a result of the photochemical reaction. Layers were obtained by using poly(hydroxyaminoether) (PHAE) containing electron-donor aromatic amino-groups in polymer chains doped with tetrabromomethane as an acceptor. The amino-groups and tetrabromomethane molecules form donor–acceptor complexes the photoexcitation of which induces electron transfer from the donor to the acceptor leading to the synthesis of a colored polycation product which possesses charge carrier photo-generating and NLO properties. Besides, these layers are electron-transporting. This allowed to obtain light-sensitive layers for recording NLO and PR images and pictures.     

孤对键弱化效应研究

在H_2O_2、N_2H_4、F_2分子中,O—O、N—N、F—F键的键长分别是0.148、0.148、0.144nm,虽比C_2H_6分子中的C—C键(0.154nm)短,但其σ键键能分别是146、160、155kJ/mol,却比C—C键能(365 kJ/mol)小约2.5倍,通常称这类原子的单键键能的反常现象为“孤对键弱化效应”。传统观点认为,半径很小的N、O、F等在化合时必须相当接近才能键合,孤对电子的排斥作用阻止了其相互接近,削弱了键能,降低了键的稳定性。显然,将这种削弱效应考虑为原子间效应是不合理的。本文用键参数图解法对“孤对键弱化效应”提出了合理的解释。     

微量元素与中药功效关系的探讨

中药中含有丰富的微量元素，其种类和含量与中药功效有着密切的关系。从微量元素与中药的滋补作用，解热作用．抗菌消炎作用和止血作用等四方面，论述了微量元素与中药功效的关系。     

Effects of Ring Size on Spectral Properties of Copper(II)-Diaminodiamide Complexes in Aqueous Solution

The electronic absorption spectra of aqueous solutions containing copper(II) ion and N, N′-bis(carbamoylmethyl)trimethylenediamine(L-1, 3, 1) at 25.0 ± 0.1°C and 0.10 mol L^?1 NaClO₄, were measured as a function of pH. The absorption maxima and the molar absorptivities of [Cu(L-l, 3, l)]²⁺, [Cu(H.₁L-1, 3, 1)]⁺, and [Cu(H_-2L-l, 3, l)] were calculated from these spectra. A comparison of the spectral parameters of these complexes with those of the copper(lI)-diaminodiamide complexes containing 6, 5, 6-and 6, 6, 6-membered ring systems indicates that the chelate ring size has significant effects on these spectral parameters.     

低能离子注入固态甲酸钠的质能沉积效应

以N~ 、H~ 、Ar 三种离子分别辐照固态甲酸钠样品，经电子顺磁共振（EPR），红外光谱（IR）的检测。结果发现，三种低能离子辐照后的甲酸钠样品中产生了COO~-自由基和亚甲基（－CH_2）．同时，结合茚三酮反应，证明了辐照后的甲酸钠样品中还含有新的基团──氨基（NH_2），并给出了氨基的产生量与注入离子的剂量和能量的相关曲线．     

Discriminating binding and positioning of amphiphiles to lipid bilayers by H NMR

The binding and positioning in lipid bilayers of three well-known drugs—imipramine, nicotine, and caffeine—have been studied using ¹H NMR. The membrane model system consisted of “fast-tumbling” lipid bicelles, in which a bilayered lipid domain, composed of the unsaturated lipid, 1,2-dimyristelaidoyl-sn-glycero-3-phosphocholine (DMLPC) was surrounded by a rim of deuterated detergent-like lipids, consisting of 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC-d22). Binding and immersion depth information was obtained by three experiments. (1) ¹H chemical shift perturbations, upon transfer of the amphiphiles from water to a bicelle mixture, were used to estimate regions of the amphiphiles that interact with the membrane. (2) Water contact to resolvable protons was measured through a Nuclear Overhauser Effect (NOE) between water and resolvable drug and lipid resonances. In the case of both lipids and membrane bound drugs, positive NOEs with large cross-relaxation rates were measured for most resonances originating from the membrane hydrophilic region, while negative NOEs were observed predominantly to resonances in the hydrophobic region of the membrane. (3) ¹H NMR measurements of oxygen-induced (paramagnetic) spin-lattice relaxation rates, which are known to increase with membrane immersion depth, were used to corroborate conclusions based on chemical shift perturbations and water-ligand NOEs.     

A Heptacene Analogue Entailing a Quinoidal Benzodi[7]annulene (7/6/7 Ring) Core with a Tunable Configuration and Multiple Redox Properties

Non-benzenoid acenes containing heptagons have received increasing attention. We herein report a heptacene analogue containing a quinoidal benzodi[7]annulene core. Derivatives of this new non-benzenoid acene were obtained through an efficient synthetic strategy involving an Aldol condensation and a Diels–Alder reaction as key steps. The configuration of this heptacene analogue can be modulated from a wavy to a curved one by just varying the substituents from a (triisopropylsilyl)ethynyl group to a 2,4,6-triisopropylphenyl (Trip) group. When mesityl (Mes) groups are linked to the heptagons, the resulting non-benzenoid acene displays polymorphism with a tunable configuration from a curved to a wavy one upon varying the crystallization conditions. In addition, this new non-benzenoid acene can be oxidized or reduced by NOSbF₆ or KC₈ to the respective radical cation or radical anion. Compared with the neutral acene, the radical anion shows a wavy configuration and the central hexagon becomes aromatic.     

Enaminone-Linked Covalent Organic Frameworks for Boosting Photocatalytic Hydrogen Production

Covalent organic frameworks (COFs), possessing pre-designable structures and tailorable functionalities, are promising candidates for photocatalysis. Nevertheless, the most studied imine-linked COFs (Im-COFs) usually suffer from unsatisfactory stability and photocatalytic performance. To meet this challenge, a series of highly stable enaminone-linked COFs (En-COFs) have been synthesized and afford much improved visible-light-driven hydrogen production activities, ranging from 44 to 1078 times that of isoreticular Im-COFs, with the only difference being the linkages (enaminone vs. imine) in their structures. The enhanced light-harvesting ability, facilitated exciton dissociation and improved chemical stability account for the superior activity. Furthermore, quinoline-linked COFs (Qu-COFs) have been further obtained via the post-modification of Im-COFs. Compared with Im-COFs, the photocatalytic activities of Qu-COFs are significantly improved after modification, but still below those of the corresponding En-COFs (3–107 times). The facile synthesis, excellent activity, and high chemical stability demonstrate that En-COFs are a promising platform for photocatalysis.     

A new approach to analyse H⊗(2h⊕g) Jahn-Teller system for C60

It is now well-known that electron (hole)-vibron coupling and hence Jahn-Teller (JT) effect is important understanding the properties of C₆₀ and related molecules. In this paper, we study H(2) coupling case to find the potential energy surfaces for the positively charged C₆₀ molecule due to distortion. The H(2) Jahn-Teller system is of particular importance as this will be the JT effect displayed by C₆₀ molecules removed with an electron. C₆₀ ⁺ is obtained by removing one electron from fivefold degenerate H_u highest occupied molecular orbital (HOMO) and a hole in HOMO interacts with the vibrational modes of C₆₀ and symmetry is broken. We apply the method of symmetry breaking mechanism to obtain expressions for the potential energy surface. Received 27 December 1999 and Received in final form 15 May 2000