Preparation and characterisation of some 4,4-dimethylbuta-1,3-dienone-transition metal carbonyls

(4,4-Dimethylbuta-1,3-dienone)iron tricarbonyl (IIa) is obtained in 70% yield from 3,3-dimethylcyclopropene (I) and nonacarbonyldiiron and in 17% yield from I and pentacarbonyliron. Analogously (4,4-dimethylbuta-1,3-dienone)-(η⁵-cyclopentadienyl)manganese carbonyl (V) is formed from I and (η⁵-cyclopentadienyl)(tetrahydrofuran)manganese dicarbonyl. Complexes IIa and V have been characterised by physical and chemical methods. Triphenylphosphine displaces one CO ligand from IIa to yield the corresponding triphenylphosphine-iron complex. The structure of IIa has been determined by X-ray diffraction.     

Synthesis of pyrimido[4,5-e][1,4]oxazepin-5-ones

Eighteen novel pyrimido[4,5-e][1,4]oxazepin-5-ones were prepared directly via the reaction of either ethyl 4-chloro-2-phenyl-5-pyrimidinecarboxylate (Ia) or ethyl 4-chloro-2-m-chlorophenyl-5-pyrimidinecarboxylate (Ib) with a variety of substituted 2-(alkylamino)ethanols. A typical example was the preparation of 8,9-dihydro-9-methyl-2-phenylpyrimido[4,5-e][1,4]-oxazepin-5(7H)-one (IIa) from the reaction of Ia with 2-(methylamino)ethanol. Hydrolytic cleavage of the lactone ring in IIa with sodium hydroxide solution, followed by acidification with hydrochloric acid afforded 4-[(2-hydroxyethyl)methylamino]-2-phenyl-5-pyrimidinecarboxylic acid (IV). Reactions of IIa with concentrated ammonium hydroxide or hydrazine also caused cleavage of the lactone ring, giving the corresponding amide (V) or hydrazide (VI), respectively. Structural assignments were supported by infrared and nuclear magnetic resonance spectra.     

Studies of nucleosides and nucleotides—XLVI Purine cyclonucleosides—13. Synthesis and properties of 8,5′-anhydro-8-mercaptoadenosine

Starting from 8-bromoadenosine, 2′,3′-O-isopropylidene-(IIa) and 2′,3′-O-ethoxymethylidene-5′-O-tosyl-8-bromoadenosme (IIb) were synthesized. Compounds IIa, b gave 8,5′-anhydronucleosides (IV a and b) on treatment with hydrogen sulfide in pyridine or aqueous sodium hydrogen sulfide in pyridine at −5–−15°. The structure of IV was confirmed by UV absorption, NMR and elemental analysis. CD and ORD measurements of IV showed large positive Cotton effects around absorption maxima. Acidic removal of the protecting group in IV gave 8,5′-anhydro-8-mercaptoadenosine (V), which was desulfurized to afford 5′-deoxyadesine (VI).     

Polarographic reduction of pertechnetate

Oxidation states were identified for the products of electrolytic reduction of pertechnetate at the mercury cathode in a variety of media, and for the products of reoxidation upon reversing the cell current. Tast polarography, pulse polarography and triangular-wave voltammetry were employed. The first cathodic wave in acidic phosphate was identified as Tc(VII) → Tc(III) by means of the ratio between it and the Tc(III) → Tc(IV) reoxidation wave obtained on anodic-sweep pulse polarography. This wave was then used as a standard to determine values of n in other media of the same ionic strength. The first wave in acidic media occurred at pH-dependent potential and was found generally to correspond to the formation of Tc(III). The Tc(III) could in some media be reoxidized at the electrode to Tc(IV) or Tc(V). For the second wave in acidic media, which occurred at ?0.9 V, diffusion current measurements indicated that n≤7 with a catalytic component preventing determination of the exact value. In alkaline or unbuffered media the first wave occurred at ?0.8 V and a second wave was sometimes seen at ?1.0 V. The wave heights in alkaline media, while generally proportional to concentration of pertechnetate and varying with drop time in the manner expected for a diffusion current, often corresponded to non-integral values of n. In certain basic media the reduction of pertechnetate led to the formation of an insoluble oxidizable surface film. Under all conditions investigated the reduction of pertechnetate proved to be irreversible.     

四-β-(氨甲基)酞菁锌盐酸盐的合成及光物理光化学性质研究

四-β-(邻苯二甲酰亚胺甲基)酞菁锌(ZnPcP4)与85%水合肼反应得到四-β-(氨甲基)酞菁锌(ZnPcN4,分子式C36H28N12Zn),其盐酸盐为ZnPcN4.HCl。测试合成得到的标题化合物紫外-可见电子吸收光谱,荧光光谱和单线态氧生成速率。标题化合物在水中聚集,在90%1,2-丙二醇/水中主要以单体形式存在。目标酞菁锌配合物在90%DMF/水的中性溶液存在聚集体,在弱酸性条件下,随酸度增大,675 nm处Q带单体吸收峰升高,在DMF/water(10%,V/V)/HCl(1.2 mmol·L-1)溶液中10-5 mol·L-1的酞菁配合物基本上没有聚集;在强酸性条件下,随酸度增大,675 nm处Q带单体吸收峰下降的同时,在713 nm处酞菁单质子化吸收峰强度有所增加。ZnPcN4.HCl在DMF体系中聚集,荧光量子产率和单线态氧量子产率变小,但其在DMF/water(10%,V/V)/HCl(1.2mmol·L-1)体系中主要以单体形式存在,荧光量子产率为0.19,单线态氧量子产率0.58,光敏活性与标准无取代酞菁锌相近。     

乙醇在不同介质中电氧化的原位表面增强拉曼光谱研究

采用常规电化学伏安技术和电化学原位表面增强拉曼光谱(in-situ SERS)技术研究了不同介质中乙醇在粗糙铂电极上的电催化氧化行为. 发现不论在酸性、中性还是碱性介质中, 乙醇均能在粗糙铂电极上自发氧化解离生成强吸附中间体CO; 碱性介质中, CO在粗糙铂电极上基本氧化完全的电位(0.20 V)比中性和酸性介质中(0.50 V)负移了约0.30 V. 而乙醇在粗糙铂电极上CV正向扫描的氧化峰电位(-0.20 V)比酸性介质中(0.65 V)负移了约0.85 V. 比较不同介质中乙醇和CO在粗糙铂电极上的氧化峰电流和峰电位可以发现, 粗糙铂电极在碱性介质中对乙醇和CO的电催化氧化活性比中性和酸性介质中更强; 可以推测, 不论在酸性、中性还是碱性介质中, 乙醇在粗糙铂电极上的氧化过程均按双途径机理进行.     

Terpenoids—LVII Synthesis of some germacrane derivatives

Both liquid and solid hexahydrocostunolides obtained by the pressure hydrogenation of costunolide (V) and solid dihydrocostunolide (VI) respectively, give the same optically active hexahydrogermacol (IIIa), when subjected to controlled reduction with LiAlH₄, followed by Huang-Minlon reduction. The alcohol (IIIa) on oxidation with chromic oxide gives optically active hexahydrogermacrone (IIa). Dehydration of IIIa with KHSO₄ followed by catalytic hydrogenation gives the optically inactive saturated hydrocarbon, germacrane (IV). Since the total synthesis of solid dihydrocostunolide (VI) has already been achieved the preparation of IIIa, IIa and IV from VI constitutes a total synthesis of the above three compounds.     

Preparation of 16-substituted 3-hydroxyestra-1,3,5(10)-triene-17-ones starting with the bromination of estrone acetate

The bromination of estrone acetate (Ia) leads to a mixture of acetates of 16-bromo-16-bromo-, and 16,16-dibromoestrone (IIa, IIIa, and IVa) in a ratio of 63:28:9. On treatment with an aqueous methanolic solution of potash, depending on the conditions, a mixture of (IIa) and (IIIa) gives 3,16-dihydroxyestra-1,3,5(10)-trien-17-one (V) or 3,17-dihydroxyestra-1,3,5(10)-trien-16-one (VI). When 5 g of (Ia) was brominated with 2.8 g of Br₂ in chloroform and the products were chromatographed on silica gel, 0.36 g of (IVa), C₂₀H₂₂Br₂O₃, mp 165–166°C (from ether) 0.37 g of (IIIa), mp 169–170.5°C, 4.6 g of a mixture of (IIa) and (IIIa), 30 mg of (Ia) and 0.2 g of a mixture of 16- and 16-bromoestrones was obtained. The action of potash on a mixture of (IIa) and (IIIa) in aqueous MeOH at 20°C led to the epimerization of the (IIa) into (IIIa) and then the conversion of the latter into (V) with mp 203.5–206°C; diacetate with mp 172–173°C (acetone-ethanol). Similarly, but with heating (98°C, 3 h), a mixture of (IIa) and (IIIa) was converted into (VI), with mp 234–236°C. Characteristics of the IR and PMR spectra of the compounds obtained are given.S. Ordzhonikidze All-Union Scientific-Research Institute of Pharmaceutical Chemistry, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 465–469, July–August, 1983.     

PHOTOCHEMICAL REACTIONS OF CYTOSINE AND 5-METHYLCYTOSINE WITH METHYLAMINE AND n-BUTYLAMINE

Abstract The photoinduced exchange reactions of cytosine ( la ) and 5-methylcytosine (IIa) with two primary amines have been studied. The reactions of Ia and IIa with methylamine lead, respectively, to 1-methylcytosine ( Ib ) and 1,5-dimethylcytosine (IIb) as final products; the reactions of the same two starting materials with n -butylamine gives the corresponding n -butyl compounds. The reactions of IIa with the two amines also gave small amounts of 1-methylthymine and 1- n -butylthymine. An opened ring intermediate, N-(N'-methylcarbamoyl)-3-arnino-2-methylacrylamidine ( IVa ), was isolated from the IIa -methylamine system irradiated at pH 7 and shown to be a precursor of both IIb and 1-methylthymine. The pH profiles for rate of production of IIb , 1-methylthymine and IVa in the reaction of IIa with methylamine were determined and found to be similar in shape. All three profiles show a maximum in reactivity at about pH 8.7 with some reactivity being detectable at pH values as low as 5.     

Synthesis and photoluminescent and electrochromic properties of aromatic poly(amine amide)s bearing pendent N‐carbazolylphenyl moieties

A series of novel poly(amine amide)s ( IIa – IIl ) with pendent N‐carbazolylphenyl units having inherent viscosities of 0.25–1.06 dL/g were prepared via direct phosphorylation polycondensation from various dicarboxylic acids and a carbazole‐based aromatic diamine. Except for poly(amine amide) IIc , derived from trans‐1,4‐cyclohexanedicarboxylic acid, all the other amorphous poly(amine amide)s were readily soluble in many polar solvents, such as N,N‐dimethylacetamide and N‐methyl‐2‐pyrrolidone (NMP), and could be cast into transparent and flexible films. The aromatic poly (amine amide)s had useful levels of thermal stability associated with relatively high glass‐transition temperatures (268–331 °C), 10% weight loss temperatures in excess of 540 °C, and char yields at 800 °C in nitrogen higher than 60%. These polymers exhibited maximum ultraviolet–visible absorption at 293–361 nm in NMP solutions. Their photoluminescence in NMP solutions exhibited fluorescence emission maxima around 362 and 448–499 nm for aromatic–aliphatic poly(amine amide)s IIa – IIc and aromatic poly (amine amide)s IId – IIl , respectively. The fluorescence quantum yield in NMP solutions ranged from 0.34% for IIj to 4.44% for IIa . The hole‐transporting and electrochromic properties were examined with electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the poly(amine amide) films cast onto an indium tin oxide coated glass substrate exhibited reversible oxidation at 0.81 V and irreversible oxidation redox couples at 1.20 V versus Ag/AgCl in acetonitrile solutions, and they revealed excellent stability of the electrochromic characteristics, with a color change from yellow to green at applied potentials ranging from 0.00 to 1.05 V. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4108–4121, 2006     

Ring opening photoreactions of cytosine and uracil with ethylamine

The photochemical reactions of cytosine (Cyt) and uracil (Ura) with ethylamine, an analog of the side chain of the amino acid lysine, have been studied. After irradiation of Cyt in aqueous ethylamine at lambda = 254 nm, N-(N'-ethylcarbamoyl)-3-aminoacrylamidine (Ia) and N-(N'-ethylcarbamoyl)-3-ethylaminoacrylamidine (Ib) were isolated as products, while irradiation of Ura gave N-(N'-ethylcarbamoyl)-3-aminoacrylamide (IIa) and N-(N'-ethylcarbamoyl)-3-ethylaminoacrylamide (IIb) as products. Studies in which Ia and IIa were incubated with ethylamine at various pH values indicate that Ib and IIb are secondary products produced via thermal reactions of Ia and IIa with ethylamine. Heating of Ia and Ib leads to ring closure with the resultant formation of 1-ethylcytosine; small amounts of 1-ethyluracil are also produced. Heating of IIa and IIb produces 1-ethyluracil as the sole product. Spectroscopic properties were determined for each of these opened ring products, as well as for N-(N'-ethylcarbamoyl)-3-amino-2-methylacrylamidine (III) and N-(N'-ethylcarbamoyl)-3-amino-2-methylacrylamide (IV). Quantum yield measurements showed that Ia was formed with a phi of 1.6 x 10(-4) at pH 9.8, while phi for formation of IIa was 7.2 x 10(-4) at pH 11.5. A profile of the relative quantum yield for formation of Ia, determined as a function of pH, showed that the maximum quantum yield occurs at around pH 9.5; the analogous profile for IIa shows a maximum quantum yield at pH 11.3 and above. Acetone sensitization does not produce Ia in the Cyt-ethylamine system, which indicates that the known triplet state of Cyt is not involved in reactions leading to this opened ring product.     

Synthesis and Dynamic NMR Studies of Some New Symmetrical Podands of Dithiocarbamates Formed from Bis(N‐thiazol)chloroacetamides

Reactions of dithiocarbamates salts ( IVa , IVb , IVc ) with bis(N‐thiazol) chloroacetamides( IIa , IIb ) in DMF furnished corresponding podands as Va , Vb , Vc , Vd , Ve , Vf in high to excellent yields. Two reacting ligands ( IIa , IIb ) were obtained in the reaction of bis(aminothiazoles) ( Ia , Ib ) with chloroacetyl chloride. Dynamic NMR spectroscopic data of two series of podands ( Va , Vb , Vc and Vd , Ve , Vf ) are discussed and figured out their free energy of activation () at coalescence temperatures. The s of these podands were attributed to conformational isomerization in the range of 14.9–16.2 kcal/mol due to rotation and resonance effect about thioamide C―N bond.     

Studies on antidiabetic agents. X. Synthesis and biological activities of pioglitazone and related compounds

Various analogues of a new antidiabetic agent, pioglitazone (AD-4833, U-72107), were synthesized in order to study in more detail the structure-activity relationships of this class of drug. 5-(4-Pyridylalkylthiobenzyl)-2,4-thiazolidinediones (I), thia-analogues of pioglitazone, were prepared via Meerwein arylation of the alkylthioanilines (IV). 5-(4-Pyridylalkoxybenzylidene)-2,4-thiazolidinediones (IIa) and related heterocyclic analogues (IIb) were synthesized by Knoevenagel condensation of the aldehydes (VIII) with the corresponding azolidinones. Compounds I and II were evaluated for hypoglycemic and hypolipidemic activity in genetically obese and diabetic yellow KK (KKAy) mice. Several 5-[4-[2-(2-pyridyl)ethoxy]-benzylidene]-2,4- thiazolidinediones (IIa) were equipotent to pioglitazone. However, the thia-analogues (I) and the benzylideneheterocycles (IIb) had decreased activity. Catalytic hydrogenation of the 5-benzylidene analogue (14) was found to be a convenient new synthetic method for pioglitazone. The configuration of 14 is also discussed.     

Carbon-supported Fe/Co-N electrocatalysts synthesized through heat treatment of Fe/Co-doped polypyrrole-polyaniline composites for oxygen reduction reaction

In this paper,we synthesized cathode catalysts(PANI-PPYR,Fe/PANI-PPYR,Co/PANI-PPYR and Fe-Co/PANI-PPYR)with high performance oxygen reduction by using a simple heat treatment process.These catalysts were fabricated by directly calcining the Fe and/or Co doped polyaniline(PANI)-polypyrrole(PPYR)composites.Their electrocatalytic activity for ORR both in acidic and in alkaline media was investigated by voltammetric techniques.Among the prepared catalysts,Co/PANI-PPYR presents the most positive ORR onset potential of 0.62 V(vs.SCE)in 0.5 mol/L H2SO4 solution or?0.09 V(vs.SCE)in 1 mol/L NaOH solution.In addition,the Co/PANI-PPYR catalyst shows the largest limiting-diffusion current density for ORR,which is 4.3 mA/cm2@0.2 V(vs.SCE)in acidic and 2.3 mA/cm2@?0.3 V(vs.SCE)in alkaline media.In acidic media,a four-electron reaction of ORR on the Co/PANI-PPYR and Fe/PANI-PPYR catalysts is more dominant than a two-electron reaction.In alkaline media,however,a four-electron and a two-electron mechanisms are co-present for the ORR on all the prepared catalysts.Co/PANI-PPYR catalyst also presents good electrocatalytic activity stability for ORR both in acidic and in alkaline media.     

Some heterocyclic sulfonyl derivatives

2,3-Diphenylpyrazine, 3,4-diphenylfurazan and 2-methyl-4,5-diphenyl oxazole react with chlorosulfonic acid to give the sulfonyl chlorides Ia, IIa, IIIa. The chlorides were condensed with nucleophiles to give thirteen derivatives. 4′,4″-bis-Dimethylsulfamoyl-2-methyl-4,5-diphenyloxazole (Illb) was oxidized with bromine to give 4,4′-bis-dimethylsulfamoylbenzil (IV), which by heating with ethylenediamine afforded the 4′,4″-bis-dimethylsulfamoylpyrazine (V). The spectral data of the various compounds are briefly discussed.     

A unique dinuclear mixed V(V) oxo-peroxo complex in the structural speciation of the ternary V(V)-peroxo-citrate system. potential mechanistic and structural insight into the aqueous synthetic chemistry of dinuclear V(V)-citrate species with H2O2

Diverse vanadium biological activities entail complex interactions with physiological target ligands in aqueous media and constitute the crux of the undertaken investigation at the synthetic level. Facile aqueous redox reactions, as well as nonredox reactions, of V(III) and V(V) with physiological citric acid and hydrogen peroxide, under pH-specific conditions, led to the synthesis and isolation of a well-formed crystalline material upon the addition of ethanol as the precipitating solvent. Elemental analysis pointed to the molecular formulation (NH4)4[(VO2){VO(O2)}(C6H5O7)2]·1.5H2O (1). Complex 1 was further characterized by Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR), Raman spectroscopy, cyclic voltammetry, and X-ray crystallography. The crystallographic structure of 1 reveals the presence of the first dinuclear V(V)-citrate complex with non-peroxo- and peroxo-containing V(V) ions, concurrently present within the basic VV2O2 core. The nonperoxo unit VO2+ and the peroxo unit VO(O2)+ are each coordinated to a triply deprotonated citrate ligand in a distinct coordination mode and coordination geometry around the V(V) ions. These units are similar to those in homodinuclear complexes bearing oxo or peroxo groups. The unique assembly of both units in the anion of 1 renders the latter as a potential intermediate in the peroxidation process, from [V2O4(C6H5O7)2]4– to [V2O2(O2)2(C6H6O7)2]2–. The transformation reactions of 1 establish its connection with several V(V) and V(IV) dinuclear species present in the aqueous distribution of the V(IV,V)-citrate systems. The shown position of 1 as an intermediate in the mechanism of H2O2 addition to dinuclear V(V)-citrate species portends its role in the complex aqueous distribution of species in the ternary V(V)-peroxo-citrate system and its potential reactivity in (bio)chemically relevant media.     

Stabilities and Biological Activities of Vanadium Drugs: What is the Nature of the Active Species?

Diverse biological activities of vanadium(V) drugs mainly arise from their abilities to inhibit phosphatase enzymes and to alter cell signaling. Initial interest focused on anti‐diabetic activities but has shifted to anti‐cancer and anti‐parasitic drugs. V‐based anti‐diabetics are pro‐drugs that release active components (e.g., H₂VO₄⁻) in biological media. By contrast, V anti‐cancer drugs are generally assumed to enter cells intact; however, speciation studies indicate that nearly all drugs are likely to react in cell culture media during in vitro assays and the same would apply in vivo. The biological activities are due to V^V and/or V^IV reaction products with cell culture media, or the release of ligands (e.g., aromatic diimines, 8‐hydroxyquinolines or thiosemicarbazones) that bind to essential metal ions in the media. Careful consideration of the stability and speciation of V complexes in cell culture media and in biological fluids is essential to design targeted V‐based anti‐cancer therapies.     

Tautomer chemistry of thiazolidines. 1-Thia-4-azaspiro[4,5] decanes

The thiazolidine, 1-thia-4-azaspiro[4,5] decane (Ia), which is derived from cyclohexanone and 2-aminoethanethiol (X), forms a thiazolidone (VIII) with mercaptoacetic acid more slowly and in lower yield than with 2-phenylthiazolidine, a case reported previously. A thiazolidine which is related to a non-conjugate chain tautomer such as Ic, might be expected to behave in this way. Alkylation, as another possible example of tautomer chemistry, was studied, and N-, S-, and C-alkylation were all observed under varying circumstances. Thus, thiazolidine la undergoes alkylation with methyl iodide in ethanol to form the N-methylthiazolidine (IIa), and in sodium-liquid ammonia to give the S-methyl derivative (III). In the latter case, alkylation occurs with reductive cleavage. Although no trace of other tautomer derivatives (IV, V) was to be found in the methyl iodide alkylation, I with acrylonitrile did in fact give C-alkylation. An analytically pure mixture of tautomers was obtained, from which 2-oxocyclohexanepropionitrile (VI) was isolated on hydrolysis. In a manner similar to the formation of III, IIa was S-alkylated by treatment with sodium-liquid ammonia followed by benzyl chloride to give a saturated product (XVII). Although such a process might be identified with a chain tautomer (IIb), the evidence is to the contrary, since the intermediate (XIV), which might be involved in such a process, fails to undergo a similar reduction with sodium-liquid ammonia. A greatly improved procedure for the preparation of thiazolidine (XI, 86% yield) is also reported.     

Dibenzothiophene-thiophene hybrid electrochromic polymer: effect of media on electrosynthesis and optical properties

π-Conjugated monomer, namely 2,8-bis-(4-octoxythiophen-2-yl)-dibenzothiophene (DBT-3OctTh), containing dibenzothiophene moiety as the central unit and 3-octoxythiophene as the external unit have been synthesized via Stille coupling reaction. The monomer was obtained as white powder in a yield of 75 %. Its electropolymerization was comparatively investigated in different media (dichloromethane (DCM), propylene carbonate (PC), or boron trifluoride diethyl etherate (BFEE)), all using Bu₄NPF₆ as the electrolyte. In BFEE, DBT-3OctTh revealed the lowest onset oxidation potential (0.67 V vs. Ag/AgCl) than DCM (1.12 V) and PC (1.13 V), leading to a facile electrodeposition to prepare poly(2,8-bis-(4-octoxythiophen-2-yl)-dibenzothiophene) (PDBT-3OctTh) with less possibility occurring on the side reactions. Doping level was calculated to be 0.32 in DCM, 0.12 in BFEE, and 0.04 in PC, respectively. The structure and performances of as-prepared polymers were systematically studied by cyclic voltammetry and spectroelectrochemistry. Spectroelectrochemical analysis revealed that PDBT-3OctTh films prepared in these media all switched light grey in the neutral state whereas blue in the oxidized state. Further, the existence of polaron or/and bipolaron in the oxidation process demonstrated that PDBT-3OctTh was p-dopable.     

Solvothermal syntheses of [Ln(en)3(H2O)x(mu(3-x)-SbS4)] (Ln = La, x = 0; Ln = Nd, x = 1) and [Ln(en)4]SbS4.0.5en (Ln = Eu, Dy, Yb): a systematic study on the formation and crystal structures of new lanthanide thioantimonates(V)

New lanthanide thioantimonate(V) compounds, [Ln(en)3(H2O)x(mu(3-x)-SbS4)] (en = ethylenediamine, Ln = La, x = 0, Ia; Ln = Nd, x = 1, Ib) and [Ln(en)4]SbS4.0.5en (Ln = Eu, IIa; Dy, IIb; Yb, IIc), were synthesized under mild solvothermal conditions by reacting Ln2O3, Sb, and S in en at 140 degrees C. These compounds were classified as two types according to the molecular structures. The crystal structure of type I (Ia and Ib) consists of one-dimensional neutral [Ln(en)3(H2O)x(mu(3-x)-SbS(4))]infinity (x = 0 or 1) chains, in which SbS4(3-) anions act as tridentate or bidentate bridging ligands to interlink [Ln(en)3]3+ ions, while the crystal structure of type II (IIa, IIb, and IIc) contains isolated [Ln(en)4]3+ cations, tetrahedral SbS4(3-) anions, and free en molecules. A systematic investigation of the crystal structures of the five lanthanide compounds, as well as two reported compounds, clarifies the relationship between the molecular structure and the entity of the lanthanide(III) series, such as the stability of the lanthanide(III)-en complexes, the coordination number, and the ionic radii of the metals.