稀土配合物的研究(Ⅲ)——稀土离子与HPMBP及α-亚硝基-β-萘酚三元配合物的制备及表征

自从1959年Iensen将1-苯基-3-甲基-4-苯甲酰基-吡唑酮-5(HPMBP)推荐为一种新型β-二酮类萃取剂以来,用它作为酸性螯合配体而合成的稀土三元配合物为数不少,但所涉及的中性配体多为膦氧单齿配体和以氮为配位原子的联吡啶及二氮杂菲类双齿配体。α-亚硝基-β-萘酚(NN)作为酸性配体已被广泛地用于过渡元素的溶剂萃取,但用它作为中性配体的稀土三元配合物尚未见报道。本文报道了14种稀土离子与HPMBP及NN的二元固态配合物的合成并对其红外光谱、质子核磁共振谱进行了研究。     

4-乙酰基-2-硝基苯甲醛的简便合成

从4-乙酰基-2-硝基甲苯出发, 经溴化、羟化、氧化以88.5%的总收率制备得到4-乙酰基-2-硝基苯甲醛.     

2-甲氧基-3-氟-4-碘吡啶的合成

2-甲氧基-3-氟-4-碘吡啶是一个重要的医药化工中间体,其合成路线未见文献报道。以2-甲氧基-3-氟-5-氯吡啶为起始原料,经氢解和碘代两步反应合成标题化合物,总收率62.8%,其结构经¹H NMR, ¹³C NMR和MS确证。     

2-甲基-4-羟基-6-苯基嘧啶和2-甲基-4-羟基-5-溴-6-苯基嘧啶的高效液相色谱法分离测定

采用ODS-C18色谱柱和紫外检测器,对2-甲基-4-羟基-6-苯基嘧啶和2-甲基-4-羟基-5-溴-6-苯基嘧啶的含量进行HPLC分离测定.以甲醇水=4555为流动相,紫外检测波长为237 nm,样品线性范围为0.001～0.1 mg/mL.2-甲基-4-羟基-6-苯基嘧啶的RSD为0.5%;2-甲基-4-羟基-5-溴-6-苯基嘧啶的RSD为1.0%.     

1-苯甲酰基-1-甲硫基甲醇与硫脲和芳胺的反应研究

1-苯甲酰基-1-甲硫基甲醇(2)与硫脲(3a)和芳基取代硫脲(3b-3i)在弱酸性条件下回流反应1h,得到5-苯基咪唑啉-2-硫酮-4-酮(4a)和1-芳基-5-苯基咪唑啉-2-硫酮-4-酮(4b-4i),产率72%～89%.而化合物2与芳胺(5a-5f)在弱碱性条件下回流反应3h,则得到2-芳胺基-2-甲硫基苯乙酮(6a-6f),产率为64%～88%.     

基于吡啶基苯甲酸盐的两个银(Ⅰ)配合物的合成、晶体结构及荧光性质

合成了2个含有吡啶基苯甲酸盐的银(Ⅰ)配合物,即[Ag₂(PPh₃)₂(4,4-pybz)₂(H₂O)₂]_n(1)和[Ag₂(PPh₃)₂(4,3-pybz)₂]·2CH₃OH(2)(PPh₃=三苯基膦,4, 4-pybz=4-吡啶-4-基-苯甲酸根, 4,3-pybz=4-吡啶-3-基-苯甲酸根),并通过红外光谱、元素分析和荧光光谱进行分析和表征,它们的结构由X射线单晶衍射测定。在不同的溶剂下,2个配合物由AgBF₄、PPh₃和不同的吡啶苯甲酸在氨水作用下,以1:1:1的比例反应而成。在配合物1中,所有的银原子由吡啶基苯甲酸桥连形成一维链状结构。在配合物2中,2个银原子通过2个4-吡啶-3-基-苯甲酸根配体形成双核结构。在荧光光谱中,在发射状态下所有的峰均来源于配体的π-π*跃迁。     

基于吡啶基苯甲酸盐的两个银(Ⅰ)配合物的合成、晶体结构及荧光性质

合成了2个含有吡啶基苯甲酸盐的银(Ⅰ)配合物,即[Ag₂(PPh₃)₂(4,4-pybz)₂(H₂O)₂]_n(1) 和[Ag₂(PPh₃)₂(4,3-pybz)₂]·2CH₃OH(2)(PPh₃=三苯基膦,4, 4-pybz=4-吡啶-4-基-苯甲酸根, 4,3-pybz=4-吡啶-3-基-苯甲酸根),并通过红外光谱、元素分析和荧光光谱进行分析和表征,它们的结构由X射线单晶衍射测定.在不同的溶剂下,2个配合物由AgBF₄、PPh₃和不同的吡啶苯甲酸在氨水作用下,以1:1:1的比例反应而成.在配合物1中,所有的银原子由吡啶基苯甲酸桥连形成一维链状结构.在配合物2中,2个银原子通过2个4-吡啶-3-基-苯甲酸根配体形成双核结构.在荧光光谱中,在发射状态下所有的峰均来源于配体的π-π*跃迁.     

新型香豆素类荧光化合物的合成及荧光性质研究

合成了两种香豆素类荧光化合物6,8-二氯-7-羟基香豆素-3-羧酸（DClC）和6-氯-7-羟基香豆素-3-羧酸（MClC）,其中DClC未见文献报道,并通过红外光谱、核磁共振、质谱等手段对产物的结构进行了表征。同时首次研究了这两种香豆素衍生物的紫外、荧光性质,以及不同极性溶剂、pH值、表面活性剂等的影响。结果表明,pH对性质测定影响较大,当pH=10时,DClC和MClC的荧光强度明显增强。     

虾青素的合成

以α-紫罗兰酮为起始原料, 采用2C₁₅＋C₁₀→C₄₀路线合成了虾青素. 并经过选择性环氧化三甲基硅基烯醇醚双键的关键步骤, 设计并完成了关键中间体C₁₅部分——6-羟基-3-(3-羟基-3-甲基-1,4-戊二烯)-2,4,4-三甲基-2-环己烯-1-酮的合成.     

3-甲基-2-戊烯-4-炔醛的合成新方法

化合物3-甲基-2-戊烯-4-炔-1-醛两端均为活性官能团,在分子连接及成环反应中能够起到非常重要的作用,是合成轮烯酮[1-7],脱落酸[8]和二苯基二苯并环辛烯[9]等的重要中间体.     

稀土(III)-冠醚配位反应的热力学性质I:稀土(III)高氯酸盐与苯-15-冠-5-在乙腈溶液中配位反应的量热滴定研究

用量热滴定法于298.15K测定了除钪、钷以外的全部十五种稀土(III)高氯酸盐与苯并-15-冠-5在乙腈溶液中的配位作用。借助计算机算出了配合物的稳定常数和配位焓, 进而算出了配位自由能和配位熵。结果表明:十五种稀土(III)离子与苯并-15-冠-5都可以配位, 配位焓为正值;La^3^+配合物最稳定, Ce^3^+次之, 其余稀土(III)离子配合物稳定性变小, 但彼此差别不大, 在Tb处有突变;熵在配合物形成时起稳定化作用。     

锌卟啉与咪唑类配体配位反应的热力学研究

Equilibrium constants for reactions of ZnT(p-X)PP(para-substituted zinc tetraphenylporphyrins) with ligands of the substituted imidazole in CH2Cl2 and several other solvents have been determined by visible spectral techniques, and Rose-Drago method. Electronic effects in metalloporphrins and effects of ligands, temperature and solvents were investigated. It was found that equilibrium constants for reactions of ZnT(p-X)PP with ligands follow Hammett equation. The changes of standard molar enthalpy△rHm and the changes of standard molar entropy △rSm of the reactions were obtainedfrom the plots of lnK vs. 1/T.     

Conductance and Thermodynamic Study of Thallium and Silver Ion Complexes with Crown Ethers in Different Binary Acetonitrile–Water Solvent Mixtures

The complexation reactions between Ag⁺ andTl⁺ ions with 15-crown-5 (15C5) and phenyl-aza-15-crown-5(PhA15C5) have been studied conductometrically in 90%acetonitrile-water and 50% acetonitrile - water mixed solvents attemperatures of 293, 298, 303 and 308 K. The stability constants of theresulting 1 : 1 complexes were determined, indicating that theTl⁺ complexes are more stable than the Ag⁺complexes. The enthalpy and entropy of crown complexation reactions were determined from the temperature dependence of the complexation constants.The enthalpy and entropy changes depend on solvent composition and the T S⁰ _o–H⁰ plotshows a good linear correlation, indicating the existence of entropy –enthalpy compensation in the crown complexation reactions.     

Regularities in the Influence of Water-Organic Solvents on the Thermodynamics of Complex Formation: II.1 Changes in Enthalpy and Entropy of Formation of Ammonia and Carboxylate Complexes

The role of enthalpy, entropy contributions to the shift of complex formation equilibria inwater-organic solvents was studied. The formation of both ammonia and carboxylate complexes of d-metalions was found to be presumably enthalpy-controlled. The role of entropy changes increases in binary solvents with a high level of supramolecular organization, and also in the case of formation of complexes of the highest orders, when the coordination of ligands is accompanied either by a complete displacement of solvent molecules from the inner coordination sphere or by a change in the complex structure. Thus found regularities can be applied for the prediction of heat effects of complex formation in water-organic solvents. In the fist communication [1] of this series we have considered the effects of the nature and composition of water-organic solvents on the stability of ammonia and carboxylate complexes of d-metal ions. This work is based on the data of our recent thermochemical works [2-22] and is dedicated to the study of the role of enthalpy and entropy contributions to the shift of the complex formation equilibria in water-organic solvents.     

四氮杂大环与镧系金属配合物的热力学研究

The stability constants of the 1:1 complexes of H4L2 (5,12-dipheny1-7, 14-dimethyl-1,4,8,11-tetraazamasrocyclotetradecane-N', N", N"',N""-tetraacetic acid) with Ln3+ (Ln=La, Nd, Pr, Sm, Eu, Gd, Dy, Yb) were determined by potemtiometric titrations in 0.5mol•L-1 KCl at 40±0.1℃, 50±0.1℃ and 60±0.1℃ respectively. The △H, △S and △G of the coordination reactions of H4L2 with Ln3+ were given. Influences of the steric effect and temperature changes on the stability lanthanide complexes were discussed thermodynamically.     

Thermodynamic study of complex formation between Ni2+ and Co2+ cations and 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane (kryptofix 5) in binary mixed nonaqueous solutions

Conductometric titrations were performed in pure and binary solvent solutions of ethyl acetate (EtOAc), methyl acetate (MeOAc) and methanol (MeOH) with acetonitrile (AN) at 288, 298, 308, and 318 K to determine the stoichiometry, the complex stability constants and the standard thermodynamic parameters for the complexation of nickel(II) and cobalt(II) cations with 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane (kryptofix 5). The stability constants of the resulting 1:1 complexes formed between the metal cations and the ligand in different solvent mixtures were determined by computer fitting of the conductance-mole ratio data. The results revealed that the stability order of (kryptofix 5)-Ni²⁺ and (kryptofix 5)-Co²⁺ complexes changes with nature and composition of the solvent system. There is a non-linear relationship between the logK _f values of complexes and the mole fraction of acetonitrile in the mixed solvent system. In addition, the conductometric data show that the stoichiometry of the complexes formed between the nickel(II) and cobalt(II) cations with the acyclic ligand changes with the nature of the solvent. The enthalpy and entropy values for the 1: 1 [ML] complexation reactions were evaluated from the temperature dependence of the formation constants. Thermodynamically, in most of systems, the complexation processes of nickel(II) and cobalt(II) cations with kryptofix 5, are both enthalpy and entropy stabilized and the values of these parameters are influenced by the nature and composition of the binary mixed solvent solutions.     

Kinetic and thermodynamic studies on molecular interaction of antipyrine donor and 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone as an electron acceptor in different solvents

The charge–transfer (CT) complex of donor antipyrine with Π‐acceptor 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) has been investigated spectrophotometrically in different halocarbon and acetonitrile solvents. The results indicated immediate formation of an electron donor–acceptor complex (DA), which is followed by two relatively slow consecutive reactions. The pseudo–first‐order rate constants for the formation of the ionic intermediate and the final product at various temperatures were evaluated from the absorbance–time data. The activation parameters, viz. activation energy, enthalpy, entropy, and free energy of activation, were computed from temperature dependence of rate constants. The stoichiometry of the complex was found to be 1:1 by Job's method of continuous variation. The formation constants of the resulting DA complexes were determined by the Benesi–Hildebrand equation at four different temperatures. The enthalpies and entropies of the complex formation reactions have been obtained by temperature dependence of the formation constants using Van't Hoff equation. The results indicate that DDQ complexes of antipyrine in all solvents are enthalpy stabilized but entropy destabilized. Both the kinetics of the interaction and the formation constants of the complexes are dependent upon the polarity of the solvents. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 45: 81–91, 2013     

Conductometric studies of thermodynamics of complexation of Li+, Na+ and K+ ions with 4′,4″(5″)-di-tert-butyldibenzo-18-crown-6 in binary acetonitrile–nitromethane mixtures

The complexation reactions between 4′,4″(5″)-di-tert-butyldibenzo-18-crown-6 (DTBDB18C6) and Li⁺, Na⁺ and K⁺ ions were studied conductometrically in different acetonitrile–nitromethane mixtures at various temperatures. The formation constants of the resulting 1:1 complexes were calculated from the computer fitting of the molar conductance-mole ratio data at different temperatures. At 20 °C and in nitromethane solvent, the stability of the resulting complexes varied in the order K⁺ > Na⁺ > Li⁺. The enthalpy and entropy changes of the complexation reactions were evaluated from the temperature dependence of formation constants. It was found that the stability of the resulting complexes increased with increasing nitromethane in the solvent mixture. The TΔS° versus ΔH° plot of thermodynamic data obtained shows a fairly good linear correlation indicating the existence of enthalpy–entropy compensation in the complexation reactions. The ab initio studies calculated at B3LYP/6-31G level of theory, indicate the binding energy of complexes decreases with increasing cation size in the gas phase. In the solution phase, DTBDB18C6 preferentially forms complexes with the larger ions rather than the smaller ions because the solvation energies of the smaller ions are large enough to overcome and reverse the trends in gas phase complexation. The findings of this study suggest that the current understanding of the factors influencing the selectivity of metal ion complexation by crown ethers may be in need of revision.     

Study of Complex Formation Between Dicyclohexano-18-Crown-6 (DCH18C6) with Mg 2+, Ca2+, Sr 2+, and Ba2+ Cations in Methanol–Water Binary Mixtures Using Conductometric Method

The complexation reactions between Mg²⁺,Ca²⁺,Sr²⁺ and Ba²⁺ metal cations with macrocyclic ligand, dicyclohexano-18-crown-6 (DCH18C6) were studied in methanol (MeOH)–water (H₂O) binary mixtures at different temperatures using conductometric method . In all cases, DCH18C6 forms 1:1 complexes with these metal cations. The values of stability constants of complexes which were obtained from conductometric data show that the stability of complexes is affected by the nature and composition of the mixed solvents. While the variation of stability constants of DCH18C6-Sr ²⁺ and DCH18C6-Ba²⁺versus the composition of MeOH–H₂O mixed solvents is monotonic, an anomalous behavior was observed for variations of stability constants of DCH18C6-Mg²⁺ and DCH18C6-Ca²⁺ versus the composition of the mixed solvents. The values of thermodynamic parameters (ΔH_c°, ΔS_c°) for complexation reactions were obtained from temperature dependence of formation constants of complexes using the van’t Hoff plots. The results show that in most cases, the complexation reactions are enthalpy stabilized but entropy destabilized and the values of thermodynamic parameters are influenced by the nature and composition of the mixed solvents. The obtained results show that the order of selectivity of DCH18C6 ligand for metal cations in different concentrations of methanol in MeOH–H₂O binary system is: Ba²⁺>Sr²⁺>Ca²⁺> Mg²⁺.     

Conductometric and 1H NMR studies of thermodynamics of complexation of Zn2+, Cd2+ and Pb2+ ions with tetrathia-12-crown-4 in dimethylsulfoxide-nitrobenzene mixtures

The complex formation between Zn²⁺, Cd²⁺ and Pb²⁺ ions with macrocyclic ligand, tetrathia12-crown-4 (12S4) was studied in dimethylsulfoxide (DMSO)–nitrobenzene binary mixtures at different temperatures using conductometric and ¹H NMR methods. In all cases, 12S4 found to form 1:1 complexes with these cations. The formation constants of the resulting 1:1 complexes in different solvent mixtures were determined by computer fitting of the resulting molar conductance- and chemical shift-mole ratio data. There is an inverse relationship between the complex stability and the amount of DMSO in the solvent mixtures. The stability of the resulting M²⁺-12S4 complexes found to decrease in the order Pb²⁺ > Cd²⁺ > Zn²⁺. The values of ?H°, ?S° and ?G° for complexation reactions were evaluated from the temperature dependence of formation constants via van’t Hoff method. The obtained results revealed that, in all cases, the complexes are enthalpy stabilized, but entropy destabilized and the values of ?H° and ?S° are strongly depend on the nature of medium. There is also a linear relationship between all ΔH° and TΔS° values indicating the existence of entropy–enthalpy compensation in complexation of the three cations and ligand in the solvent systems studied.