PHOTOREACTIVITY OF ISOLATED PHOTOSYSTEM I PARTICLES UPON COMBINATION WITH ARTIFICIAL LIPID MEMBRANES OR TRITON X-100 MICELLES*

Abstract— PS-I particles isolated according to Shiozawa et al. (1974) show increased rates of O₂-_- and H ⁺-uptake with ascorbate as electron donor upon combination with an artificial vesicular lipid membrane. The amount of increase varies depending on the reconstitution procedure used. Combination of PS-I particles with Triton X-100 micelles increases these photochemical activities even more. The observed proton uptake in PS-I lipid vesicles is not caused by the well-known proton gradient found in thylakoid membranes, since lipid vesicles containing extracted leaf Chl show the same activities and uncouplers have no effect. Because these phenomena are also caused by solubilized Chl, it is concluded that there is no obvious correlation with PS-I activity. Proton uptake most probably is caused by oxidation of ascorbate by either singlet oxygen, superoxide or OH-radicals formed in the light. Experimental results are obtained which indicate that Chl in lipid catalyzes formation of superoxide and singlet oxygen. However, it is not clear whether superoxide formation is caused by direct electron transport from excited Chl to oxygen or by a secondary reaction. Diphenylcarbazone disproportionation has been reported as a specific photosystem I reaction. However, PS-I lipid vesicles and Chl-lipid-Triton X-100 mixtures oxidize DPCN at comparable rates, showing that the reaction is not specific for PS-I. Cations stimulate DPCN disproportionation in Chl-lipid-Triton X-100 mixtures but do not affect the rate of P700 photooxidation at all. Therefore it is suggested that Gross and Greniers (1978) conclusion that cation regulation of PSI electron flow (studied by DPCN disproportionation of PS-I particles in Triton X-100 micelles) provides a fine tuning mechanism for energy transfer, has to be reevaluated.     

Hydrogen bonding and the protonation site in 3-methyl-4-pyrimidone

The interaction between 3-methyl-4-pyrimidone and phenol derivatives or HBr has been studied by IR spectrometry in solution and in the solid state. For pK_a values ranging from 10.3 to 4.5, normal OH··· OC hydrogen bonds are formed. With stronger acids (PK_a = 0.4 to ?6) protonation occurs at the N(1) nitrogen atom of the ring. For phenols of intermediate pK_a values (3.5), there is no preferred site of interaction, both OH···OC and NH⁺···O^? bonds being formed in solution.     

Photoinduced electron transfer of chlorophyll in lipid bilayer system

Photoinduced electron transfer from chlorophyll-a throughtheinterface of dipalmitoylphosphatidylcholine (DPPC) headgroup of the lipid bilayers was studied with electron magnetic resonance (EMR). The photoproduced radicals were identified with electron spin resonance (ESR) and radical yields of chlorophyll-a were determined by double integration ESR spectra. The formation of vesicles was identified by changes in measured λ_max values from diethyl ether solutions to vesicles solutions indirectly, and observed directly with SEM and TEM images. The efficiency of photosynthesis in model system was determined by measuring the amount of chlorophyll-a radical yields which were obtained from integration of ESRspectra.     

Synthesis and characterization of a reduced heteropoly-tungstovanadate: (NH4)7[VvO4W 10IV V 2IV O36].ca. 22H2O

The compound (NH₄)₇[ V^vO₄W ₁₀ ^VI V ₂ ^VI O₃₆]·ca.22H₂O (1) has been synthesized from an aqueous ammonium acetate buffer (pH 4) containing sodium vanadate, sodium rungstate_and sodium dithionite. Compound (1) crystallizes in a cubic space groupFm — 3, witha = 22.2001(6) ? and Z = 8. The anion [V^vO₄W ₁₀ ^VI V ₂ ^IV O₃₆]^7- is a typical Keggin type structure with V^VO₄ as the central tetrahedron. (1) has further been characterized by elemental analyses, redox titration, IR, EPR, and electronic spectroscopy and room temperature magnetic moment measurement.     

Synthesis and spectroscopic characterization of palladium(II) complexes with 6,8-dimethylimidazo[1,5- a ]-1,3,5-triazin-4( 3H )-one and 6,8-dimethyl-2-thioxo-2,3-dihydroimidazo-[1,5- a ]-1,3,5-triazin-4( 1H )-one

The preparation and spectroscopic study (¹H, ¹³C, ¹⁵NNMR, ¹³CP MAS NMR, IR) of new Pd^II complexes with 6,8-dimethylimidazo[1,5-a]-1,3,5-triazin-4(3H)-one (6,8-DiMe-4-O-IMT) (1) and 6,8-dimethyl-2-thioxo-2,3-dihydroimidazo[1,5-a]-1,3,5-triazin-4(1H)-one (6,8-DiMe-4-O-2-S-IMT) (2) is reported. The spectroscopic data indicate a square planar geometry with two N(7) bonded heterocycles and two cis-chloride anions. The final product of the thermal decomposition of cis-PdCl₂(6,8-DiMe-4-O-IMT)₂ (3) is metallic Pd, whereas for cis-PdCl₂(6,8-DiMe-4-O-2-S-IMT)₂ (4) it is metallic Pd plus C.     

Mass spectra of ethenol and its deutero analogues

Ethenol, 1-d-ethenol, O-d-ethenol and Z-2-d-ethenol were prepared by pyrolysis of corresponding 5-norbornenols at 800^°C/2 × 10^?6 Torr. The most important fragments in the electron impact mass spectrum of ethenol are [C₂H₃O]⁺ and CHO⁺ and CH₃˙. The hydrogen atom eliminated from the molecular ion comes mainly from the hydroxyl group (68%) and to a lesser extent from C(1) (25%) and C(2) (7%). The loss of the hydroxyl hydrogen is preceded by rate-determining migration of the hydrogen atom from C(1) onto C(2) to yield CH₃C?OH⁺˙ions that decompose to CH₃CO⁺ and H˙. The loss of deuterium from O-d-ethenol shows a very small primary isotope effect (k_H/k_D=1.07), whereas a significant effect is observed for the loss of hydrogen from 1-d-ethenol (k_H/k_D=1.28). The appearance energy of [C₂H₂DO]⁺ from 1-d-ethenol, AE=11.32 eV, gives a critical energy for the hydrogen loss, E=203 kJ mol^?1, which is 90 kJ mol^?1 above the thermochemical threshold for CH₃CO⁺+H˙. The appearance energy of CDO⁺ from 1-d-ethenol was measured as 12.96±0.07 eV, which sets the barrier to isomerization to CH₃CDO⁺˙ at 1121 kJ mol^?1. The ionization energy of ethenol was found to be 9.22±0.03 eV.     

Self‐Assembly,Spectroscopic and Electrochemical Studies of Nickel(II)‐4,8‐Diazaundecanediamide Complex

The self‐assembly of NiCl₂·6H₂O with a diaminodiamide ligand 4,8‐diazaundecanediamide (L‐2,3,2) gave a [Ni(C₉H₂₀N₄O₂)(Cl)(H₂O)] Cl·2H₂O ( 1 ). The structure of 1 was characterized by single‐crystal X‐ray diffraction analysis. Structural data for 1 indicate that the Ni(II) is coordinated to two tertiary N atoms, two O atoms, one water and one chloride in a distorted octahedral geometry. Crystal data for 1: orthorhombic, space group P 21nb, a = 9.5796(3) Å, b = 12.3463(4) Å, c = 14.6305(5) Å, Z = 4. Through NH···Cl–Ni (H···Cl 2.42 Å, N···Cl 3.24 Å, NH···Cl 158°) and OH···Cl–Ni contacts (H···Cl 2.36 Å, O···Cl 3.08 Å, OH···Cl 143°), each cationic moiety [Ni(C₉H₂₀N₄O₂) (Cl)(H₂O)]⁺ in 1 is linked to neighboring ones, producing a charged hydrogen‐bonded 1D chainlike structure. Thermogrametric analysis of compound 1 is consistent with the crystallographic observations. The electronic absorption spectrum of Ni(L‐2,3,2)²⁺ in aqueous solution shows four absorption bands, which are assigned to the ³A_2g → ³T_2g, ³T_2g → ¹Eg, ³T_2g → ³T_1g, and ³A_2g → ³T_1g transitions of triplet‐ground state, distorted octahedral nickel(II) complex. The cyclic volammetric measurement shows that Ni²⁺ is more easily reduced than Ni(L‐2,3,2)²⁺ in aqueous solution.     

Leurosine me­thio­dide–methanol–water (1/3/2)

The crystal structure of a methanol–water solvate ofleurosine me­thio­dide, (leurosine‐CH₃)⁺I^?·3CH₃OH·2H₂O (C₄₇H₅₉IN₄O₉·3CH₃OH·2H₂O), is described. The piperidine ring of the upper part of the mol­ecule adopts a sofa conformation. An intramolecular hydrogen bond between the tertiary N and the hydroxyl group of the vindoline moiety of the mol­ecule is present.     

正极材料Li(Ni0.5Mn0.5)1-xMxO2 (M=Ti，Al；x=0，0.02)电化学行为的比较研究

0IntroductionMany efforts have been made to develop newmaterials as an alternative to LiCoO2due to the rela-tively high cost and toxicity of Co.Much attention hasbeen paid to layered structure cathode materials suchas LiMnO2and LiNiO2due to their lower co…     

Azole. 47. Über 3-Thiomorpholino- und 3-(4-Methylpiperazino)-5-nitroindazole

The structures of 5-nitro-3-thio­morpholino-1H-indazole, C₁₁H₁₂N₄O₂S, (IIa), and 3-(4-methyl­piperazino)-5-nitro-1H-indazole–methanol–water (2/1/1), 2C₁₂H₁₅N₅O₂·CH₃OH·H₂O, (IIIa), are described. In the crystal lattice of (IIa), the mol­ecules are linked into dimers by N—H⃛N hydrogen bonds. The asymmetric unit of (IIIa) contains two independent mol­ecules of the indazole moiety, one mol­ecule of methanol and one of water. The three components of (IIIa) are linked by hydrogen bonds to form double chains running along the x axis. π-Stacking involving the indazole moieties occurs in both compounds.     

AxMn1-xFe2O4铁氧体(A=Zn,Ni)中阳离子的占位有序化行为研究

基于尖晶石晶体结构信息,本文采用热力学三亚晶格模型,将材料热力学计算和第一性原理计算相结合,研究了Zn_xMn_(1-x) Fe_2O_4和Ni_xMn_(1-x)Fe_2O_4立方相中的Zn~(2+)、Ni~(2+)、Mn~(2+)以及Fe~(3+)在8a和16d亚晶格上的占位有序化行为。结果表明:在锰铁氧体中,室温下Mn~(2+)完全占据在8a亚晶格上,Fe~(3+)完全占据在16d亚晶格上,属于正尖晶石结构;随着热处理温度升高,在1 273 K达到热处理平衡时的占位构型为(Fe~(3+)0.09Mn~(2+)0.91)[Fe~(3+)1.91Mn~(2+)0.09]O_4,在热处理温度升至1 473 K时,达到热处理平衡时的占位构型为(Fe~(3+)0.11Mn~(2+)0.89)[Fe~(3+)1.89Mn~(2+)0.11]O_4,均与实验结果符合较好。在锌铁氧体中,室温下Zn~(2+)完全占据在8a亚晶格上,Fe~(3+)完全占据在16d亚晶格上,属于正尖晶石结构;在热处理温度较高时,Zn~(2+)和Fe~(3+)发生部分置换,符合实验结果。在镍铁氧体中,半数的Fe~(3+)在室温下占据在8a亚晶格上,Ni~(2+)与剩下另一半的Fe~(3+)共同占据在16d亚晶格上,仅在热处理温度较高的时候发生微弱变化,亦与已有的实验结果吻合。在此基础上,本文进一步通过热力学模型研究了立方相尖晶石结构的Zn_xMn_(1-x)Fe_2O_4、Ni_xMn_(1-x)Fe_2O_4复合体系中阳离子占位行为与热处理温度对占位的影响规律。     

锂离子电池正极材料LiV3-xAlxO8的水热合成与性能

采用水热法制备了Al掺杂的锂二次电池正极材料LiV3-xAlxO8,并用X射线衍射和扫描电镜对材料的晶体结构和形貌进行了表征.以50 mA·g-1进行恒流充放电测试,结果表明Al掺杂能够明显改善材料的电化学性能.在掺杂改性的LiV3-xAlxO8材料中,LiV2.93Al0.07O8的初始容量最高,达到325 mAh·g-1.当掺杂量为x=0.04时,材料的循环性能最佳.LiV2.96Al0.04O8经20次循环后仍保持179 mAh·g-1的比容量,且充放电效率始终维持在98%左右.     

纳米钙钛矿型LaFe1-xNixO3(x=0~1.0)的制备及其在紫外光激发下的电化学性能

本文采用溶胶-凝胶法制备了LaFe1-xNixO3(x=0,0.2,0.4,0.6,0.8,1.0)纳米晶粉末,利用XRD、TEM和电化学测试方法对LaFe1-xNixO3材料的相结构、形貌、成分组成和其在碱液中的充放电性能以及电化学动力学性能等方面进行了表征和分析,同时对电极受紫外光激发前后的电化学行为进行了对比研究。XRD和TEM分析表明,用硝酸盐作为原材料和溶胶-凝胶方法可制备出单一相结构的纳米晶钙钛矿型LaFe1-xNixO3复合氧化物,随Ni替代量x的增大,LaFe1-xNixO3的相结构由正交结构向菱面体结构转变,其分子体积和晶粒尺寸呈现减小的趋势。电化学研究结果表明,紫外光激发前,LaFe1-xNixO3电极的放电容量随x的增加而逐渐增大;光激发后,电极的放电容量和交换电流Io与未激发前相比显著提高,当x=0.4时其放电容量具有最大值483.1mAh·g-1,Io值由光激发前的3.54～11.58 mA·g-1大幅增加至激发后的8.37～40.11 mA·g-1。     

Synthesis, Conformational Studies and Inclusion Properties of Tetrakis[(2-pyridylmethyl)oxy]thiacalix[4]arenes

An attempted O-alkylation of the flexible macrocycle 1with 2-(chloromethyl)pyridine in the presence of Cs₂CO₃ under THF reflux afforded a mixture of twoconformers of tetra-O-alkylated product 4a in a ratio of 91:9 (cone-4a:1,2-alternate-4a)in 70% yield, while other possible isomers were not observed. In the case of Na₂CO₃, there was no reaction product,only the starting compound 1, whereasonly monoalkylated compound 3 was obtained when usingK₂CO₃ as the base. The distribution of cone conformer decreased in the case of O-alkylation of tetraol 1with 4-(chloromethyl)pyridine or benzyl bromide in the presence of Cs₂CO₃ in comparison with that ofO-alkylation with 2-(chloromethyl)pyridine, while the 1,2-alternate conformer increased in the same sequence. The larger Cs⁺might increase the contribution of the metal template effect, which can hold the 2-pyridylmethyl group(s) and theoxide group(s) on the same side of the tetrathiacalix[4]arene 1 through the cation-O^- and -N-interaction in the caseof O-alkylation of tetraol 1 with 2-(chloromethyl)pyridine.Only when the template metal can hold the 2-pyridyl group(s) andthe oxide group(s) on the same side of the tetrathiacalix[4]arene is the conformation immobilized to thecone. The template effect of the cesium cation plays an important role in this alkylation reaction. The structuralcharacterization of these products is also discussed.The two-phase solvent extraction data indicated thattetrakis[(2-pyridylmethyl)oxy]thiacalix[4]arenes 4a show strong Ag⁺ affinity and a high Ag⁺ selectivity wasobserved for cone-4a. A good Job plot proves 1:1 coordination of cone-4a with Ag⁺ cation.¹H-NMR titration of cone-4a with AgSO₃CF₃ also clearly demonstrates that a 1:1complex is formed with retention of the original symmetry. In contrast, the 1,2-alternate-4a can form a 2:1 metal/thiacalix[4]arene complex and the two metal-binding sites display positive allostericity. The conformational changes ofpyridine moiety from the original outward orientation of the ring nitrogen to the inside orientation toward thethiacalixarene cavity were observed in the processof Ag⁺ complexation.     

Antioxidant,antimicrobial, and tyrosinase inhibition activities of acetone extract of <Emphasis Type="Italic">Ascophyllum nodosum</Emphasis>

The search for new antioxidants of natural origin derived from plants and seaweeds is still very important at present. In our study, the acetone extract of A. nodosum was investigated for its potential use as a natural antioxidant, natural feed additive with antibacterial activity and as a tyrosinase inhibitor. This study could be useful in the context of improved utilization of the A. nodosum extract in the food and cosmetics industry, being not only economically advantageous but also environmentally friendly. Extracts showed antioxidant activity with application of different methodologies: 1,1-diphenyl-2-picrilhydracil DPPH· radicals scavenging (39 %, 4 mg of freeze-dried sample), β-carotene-linoleic acid antioxidant assay (11 %, 4 mg of freeze-dried sample), O₂· radicals scavenging activity (IC₅₀ 0.43 mg mL⁻¹), OH· radicals scavenging activity (IC₅₀ 1.55 mg mL⁻¹), and iron chelation ability (IC₅₀ 0.56 mg mL⁻¹). The extract showed considerable antibacterial activity being more effective against gram-positive bacteria (Micrococcus luteus, Staphylococcus aureus) than against gram-negative bacteria (Escherichia coli, Enterococcus aerogenes). Results of tyrosinase assay for the acetone extract of Ascophyllum nodosum presented 65.6 % inhibition of tyrosinase activity at the IC₅₀ value of 0.1 mg mL⁻¹. The outcomes of our study support potential utilization of this brown seaweed as a source of natural antioxidants. Antioxidant activity of the studied seaweed can be apparently explained by the free radicals scavenging activity, particularly related to the mechanisms of O₂⁻· radicals scavenging activity, OH· radicals inactivation, and iron chelation ability.     

Lithiated γ-O-functionalized propyl phenyl sulfides and sulfones of the type Li[CH(SOxPh)CH2CH2OR] (x = 0, 2). [Li{CH(SPh)CH2CH2Ot-Bu}(tmeda)] – A structurally characterized organolithium inner complex

Lithiation of O-functionalized alkyl phenyl sulfides PhSCH₂CH₂CH₂OR (R = Me, 1a; i-Pr, 1b; t-Bu, 1c; CPh₃, 1d) with n-BuLi/tmeda in n-pentane resulted in the formation of α- and ortho-lithiated compounds [Li{CH(SPh)CH₂CH₂OR}(tmeda)] (α-2a–d) and [Li{o-C₆H₄SCH₂CH₂CH₂OR)(tmeda)] (o-2a–d), respectively, which has been proved by subsequent reaction with n-Bu₃SnCl yielding the requisite stannylated γ-OR-functionalized propyl phenyl sulfides n-Bu₃SnCH(SPh)CH₂CH₂OR (α-3a–d) and n-Bu₃Sn(o-C₆H₄SCH₂CH₂CH₂OR) (o-3a–d). The α/ortho ratios were found to be dependent on the sterical demand of the substituent R. Stannylated alkyl phenyl sulfides α-3a–c were found to react with n-BuLi/tmeda and n-BuLi yielding the pure α-lithiated compounds α-2a–c and [Li{CH(SPh)CH₂CH₂OR}] (α-4a–b), respectively, as white to yellowish powders. Single-crystal X-ray diffraction analysis of [Li{CH(SPh)CH₂CH₂Ot-Bu}(tmeda)] (α-2c) exhibited a distorted tetrahedral coordination of lithium having a chelating tmeda ligand and a C,O coordinated organyl ligand. Thus, α-2c is a typical organolithium inner complex.Lithiation of O-functionalized alkyl phenyl sulfones PhSO₂CH₂CH₂CH₂OR (R = Me, 5a; i-Pr, 5b; CPh₃, 5c) with n-BuLi resulted in the exclusive formation of the α-lithiated products Li[CH(SO₂Ph)CH₂CH₂OR] (6a–c) that were found to react with n-Bu₃SnCl yielding the requisite α-stannylated compounds n-Bu₃SnCH(SO₂Ph)CH₂CH₂OR (7a–c). The identities of all lithium and tin compounds have been unambiguously proved by NMR spectroscopy (¹H, ¹³C, ¹¹⁹Sn).     

Synthesis of 4,8-anhydro-d-glycero-d-ido-nonanitol 1,6,7-trisphosphate as a novel IP3 receptor ligand using a stereoselective radical cyclization reaction based on a conformational restriction strategy

4,8-Anhydro-d-glycero-d-ido-nonanitol 1,6,7-trisphosphate (9), designed as a novel IP₃ receptor ligand having an α-C-glycosidic structure, was synthesized via a radical cyclization reaction with a temporary connecting allylsilyl group as the key-step. Phenyl 2-O-allyldimethylsilyl-3,4-bis-O-TBS-1-seleno-β-d-glucopyranoside (10a), conformationally restricted in the unusual ¹C₄-conformation, was treated with Bu₃SnH/AIBN to form the desired α-cyclization product 16a almost quantitatively. On the other hand, when a conformationally unrestricted O-benzyl-protected 2-O-allyldimethylsilyl -1-selenoglucoside 15 was used as the substrate, the radical reaction was not stereoselective and gave a mixture of the α-and β-products. From 16a, the target C-glucoside trisphosphate 9 was synthesized via phosphorylation of the hydroxyls by the phosphoramidite method. During the synthetic study, an efficient procedure for the oxidative C-Si bond cleavage, via a nucleophilic substitution at the silicon with p-MeOPhLi followed by Fleming oxidation, was developed. The C-glycoside 9 was found to be a full agonist for Ca²⁺ mobilization, although its activity was weaker than that of the natural ligand IP₃. Thus, the α-C-glucosidic structure was shown to be a useful mimic of the myo-inositol backbone of IP₃.     

Syntheses and pharmacological characterization of achiral and chiral enantiopure C/Si/Ge-analogous derivatives of the muscarinic antagonist cycrimine: a study on C/Si/Ge bioisosterism

The C/Si/Ge-analogous compounds rac-Ph(c-C₅H₉)El(CH₂OH)CH₂CH₂NR₂ (NR₂=piperidino; El=C, rac-3a; El=Si, rac-3b; El=Ge, rac-3c) and (c-C₅H₉)₂El(CH₂OH)CH₂CH₂NR₂ (NR₂=piperidino; El=C, 5a; El=Si, 5b; El=Ge, 5c) were prepared in multi-step syntheses. The (R)- and (S)-enantiomers of 3a–c were obtained by resolution of the respective racemates using the antipodes of O,O′-dibenzoyltartaric acid (resolution of rac-3a), O,O′-di-p-toluoyltartaric acid (resolution of rac-3b), or 1,1′-binaphthyl-2,2′-diyl hydrogen phosphate (resolution of rac-3c). The enantiomeric purities of (R)-3a–c and (S)-3a–c were ≥98% ee (determined by ¹H-NMR spectroscopy using a chiral solvating agent). Reaction of rac-3a–c, (R)-3a–c, (S)-3a–c, and 5a–c with methyl iodide gave the corresponding methylammonium iodides rac-4a–c, (R)-4a–c, (S)-4a–c, and 6a–c (3a–c→4a–c; 5a–c→6a–c). The absolute configuration of (S)-3a was determined by a single-crystal X-ray diffraction analysis of its (R,R)-O,O′-dibenzoyltartrate. The absolute configurations of the silicon analog (R)-4b and germanium analog (R)-4c were also determined by single-crystal X-ray diffraction. The chiroptical properties of the (R)- and (S)-enantiomers of 3a–c, 3a–c·HCl, and 4a–c were studied by ORD measurements. In addition, the C/Si/Ge analogs (R)-3a–c, (S)-3a–c, (R)-4a–c, (S)-4a–c, 5a–c, and 6a–c were studied for their affinities at recombinant human muscarinic M₁, M₂, M₃, M₄, and M₅ receptors stably expressed in CHO-K1 cells (radioligand binding experiments with [³H]N-methylscopolamine as the radioligand). For reasons of comparison, the known C/Si/Ge analogs Ph₂El(CH₂OH)CH₂CH₂NR₂ (NR₂=piperidino; El=C, 7a; El=Si, 7b; El=Ge, 7c) and the corresponding methylammonium iodides 8a–c were included in these studies. According to these experiments, all the C/Si/Ge analogs behaved as simple competitive antagonists at M₁–M₅ receptors. The receptor subtype affinities of the individual carbon, silicon, and germanium analogs 3a–8a, 3b–8b, and 3c–8c were similar, indicating a strongly pronounced C/Si/Ge bioisosterism. The (R)-enantiomers (eutomers) of 3a–c and 4a–c exhibited higher affinities (up to 22.4 fold) for M₁–M₅ receptors than their corresponding (S)-antipodes (distomers), the stereoselectivity ratios being higher at M₁, M₃, M₄, and M₅ than at M₂ receptors, and higher for the methylammonium compounds (4a–c) than for the amines (3a–c). With a few exceptions, compounds 5a–c, 6a–c, 7a–c, and 8a–c displayed lower affinities for M₁–M₅ receptors than the related (R)-enantiomers of 3a–c and 4a–c. The stereoselective interaction of the enantiomers of 3a–c and 4a–c with M₁–M₅ receptors is best explained in terms of opposite binding of the phenyl and cyclopentyl ring of the (R)- and (S)-enantiomers. The highest receptor subtype selectivity was observed for the germanium compound (R)-4c at M₁/M₂ receptors (12.9-fold).     

Preparation and X‐ray analysis of potassium (2,3‐dichlorophenyl)glucosinolate

There has been much interest in obtaining crystals for crystallographic analysis of biologically active glucosinolates. Crystals of potassium (2,3‐dichlorophenyl)glucosinolate were obtained as a dual solvate, containing one methanol and one ethanol molecule of crystallization, K⁺·C₁₃H₁₄Cl₂NO₉S₂⁻·CH₃OH·C₂H₅OH. The three‐dimensional polymeric network consists of chains containing the potassium ions coordinated and bridged by sugar O atoms, which run parallel to the a axis and are further crosslinked through the sugar molecules. The channels of this network are occupied by the dichlorophenyl substituents and the ethanol and methanol solvent molecules. The structure of the S‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl)‐2,3‐dichlorophenylacetothiohydroxymate, C₂₁H₂₃Cl₂NO₁₀S, precursor has also been determined and the β‐configuration and Z isomer of the thiohydroximate substituent is confirmed.     

Evaluation of AM1-calculated radical cation ion-neutral complexes

AM1 semiempirical molecular orbital calculations are reported for 20 ion-neutral complexes, including hydrogen-bonded complexes, presumably involved in the gas-phase unimolecular decomposition of simple organic radical cations. The systems investigated are [C₂H₄O₂]^˙+, [C₂H₅NO]^˙+, [C₂H₆O]^˙+, [C₂H₆O₂]^˙+, [C₃H₆O]^˙+, [C₃H₆O₂]^˙+, [C₃H₈O]^˙+, and [C₃H₈O₂]^˙+. The AM1 results are compared with ab initio molecular orbital calculations at different levels of theory up to MP3/6-31G(d, p)//SCF/6-31G(d) + ZPVE and the available experimental data. AM1 fails to predict some local minima and the equilibrium geometries calculated for several complexes are found to be qualitatively different from those predicted by the ab initio calculations. However, reasonable agreement is generally found for the stabilization energies of the complexes toward dissociation into their loosely bound components. © John Wiley & Sons, Inc.