过渡金属掺杂亚铁锌双金属氰化物催化合成生物柴油的研究

研究了掺杂过渡金属盐(La、Ce、Zr、Mn)对亚铁锌双金属氰化物(DMC)固体酸催化剂合成生物柴油的影响,并采用XRD、FT-IR、ICP、BET等方法对其进行结构和性能表征。结果表明,1%的镧、铈、锆、锰金属盐对催化剂的活性都有提高,其中,添加1%镧的DMC催化剂活性最高,在醇油摩尔比16∶1,反应温度160 ℃,催化剂加入量2%条件下,反应7 h,脂肪酸甲酯收率达到99.3%。过渡金属盐引入对催化剂的组成没有影响,但使得催化剂更加分散,颗粒粒径更小,比表面积变大,有利于催化剂和反应物的接触,从而提高了催化剂活性。     

Inorganic supramolecular host architectures: [(M@18c6)2][TlI4].2H2O, M=0.5 Tl, (NH4,NH3), (H3O,H2O)

The compounds [(M@18c6)2][TlI4].2H2O, M=Tl, (NH4,NH3), (H3O,H2O) (cubic, Fd; a=1481.00 pm, for M=0.5 Tl, a=1304.65 pm for M=(NH4,NH3), a=1313.67 pm for M=(H3O,H2O)) can be obtained from solution in the presence of traces of transition metal halides (like copper and mercury halides). Apparently the transition metal cations work as a template in the form of tetrahedral [MX4] units during the synthesis of the supramolecular host architecture. That the compounds are versatile host lattices for tetrahedrally coordinated transition metal units becomes obvious by the large group of known host-guest complex compounds, [(MIIX4)(MI@18c6)4][TlX4]2.nH2O (MII=Cu, Co, Zn, Mn; MI=NH4+, Rb, Tl; X=Cl, Br).     

13-钒镍(锰)杂多酸稀土盐的合成及其镨盐抗肿瘤活性的研究 Ⅰ.

本文以离子交换-复分解法合成了未见文献报道的13-钒镍(锰)杂多酸的稀土盐。通式为Ln2H[MV13O38].nH2O[Ln=La, Ce, Pr, Nd, Sm, Eu; M=Ni, Mn]。经元素分析、红外光谱、电子顺磁共振、磁化率及^5^1V NMR核磁共振谱对其结构进行了表征。微量细胞培养四氮唑(MTT)法实验表明: 13-钒镍(锰)杂多阴离子的镨盐对多种人癌细胞具有较强的杀伤作用, 显示出较强的体外抗肿瘤活性。     

用无机钛源合成Ti-MCM-41的研究

采用无机络合剂稳定钛酰离子的方法,用多种无机钛源合成出了中孔Ti-MCM-41型分子筛,采用XRD,低温N2吸附和FT-IR等方法对合成的含钛分子筛进行了物性的表征。以苯乙烯的H2O2氧化作为模型反应,考察了合成的Ti-MCM-41分子筛的催化性能。结果表明,钛原子已进入分子筛骨架,用Ti(SO4)2和TiCl4为钛源合成的Ti-MCM-41分子筛在960cm^-1处存在较强的红外吸收,并对苯乙烯的H2O2氧化表现出较高的催化活性。     

Transition Metal Complexes of p-Sulfonatocalix[5]arene

The X-ray crystal structure of the p-sulfonatocalix[5]arene(5)(-) anion (1b) in the form of the dimeric hydrate Na(10)[p-sulfonatocalix[5]arene](2).33.5H(2)O (2) is reported. The reactions of 1b with a number of transition metal salts to form transition metal bridged bis(calixarene) inclusion complexes have also been investigated. The X-ray crystal structure of the "Co(H(2)O)(4)(2+)" bridged species Na(8)[Co(H(2)O)(4)(p-sulfonatocalix[5]arene)(2)].2CH(3)C(O)N(CH(3))(2).37H(2)O (3) which incorporates a "supercavity" large enough to encompass 2 N,N-dimethylacetamide (dma) guest molecules as well as ca. 15 water molecules and Na(+) ions is reported. Crystal data are as follows: for 2, monoclinic space group P2(1)/c, Z = 4, a = 22.0644(4), b = 19.1180(3), c = 27.7834(4) ?, beta = 91.780(1), V = 11714.1(5) ?(3); complex 3, orthorhombic space group Pnma, Z = 4, a = 22.2271(5), b = 30.1693(6), c = 18.8503(4) ?, V = 12640.6(5) ?(3).     

过渡金属甲基磺酸盐催化醇的四氢吡喃化反应

以过渡金属甲基磺酸盐［Mn(CH₃SO₃)₂·2H₂O, Cu(CH₃SO₃)₂·4H₂O, Co(CH₃SO₃)₂·4H₂O和Zn(CH₃SO₃)₂·4H₂O］为催化剂,在室温条件下催化醇的四氢吡喃化反应,并对反应条件进行了优化。结果表明：当醇用量为30 mmol,醇和3,4-二氢吡喃摩尔比为1.0 ：1.1,甲基磺酸盐用量为1 mmol,二氯甲烷20 mL时,可高效催化醇的四氢吡喃化反应。与路易斯酸催化活性相比,过渡金属甲基磺酸盐催化醇的四氢吡喃化反应效果最好,催化酚的效果较差。用Mn(CH₃SO₃)₂·2H₂O和Cu(CH₃SO₃)₂·4H₂O催化正丁醇的四氢吡喃化反应,重复使用5次,收率分别为89%和92%。     

Reversible anion exchange and sensing in large porous materials built from 4,4'-bipyridine via pi...pi and H-bonding interactions

Two unusual d10 compounds, [Zn2(bipy)3(H2O)8(ClO4)2(paba)2].2(bipy).4H2O (1) and [Cd2(bipy)4(H2O)6(ClO4)2(paba)2].(bipy).5H2O (2) (bipy = 4,4'-bipyridine, paba = p-aminobenzoate), were obtained from reaction of the metal salts, bipy and paba in an EtOH/H2O mixture. The bipy ligands in the two compounds exhibit two new modes of coordinating to transition metal ions, resulting in the formation of large porous frameworks. Immersion of single crystals of 1 in an aqueous solution of NH4PF6 results in the formation of its hexafluorophosphate derivative 3 as shown by single crystal diffraction. Immersion of crystals of 3 in NaClO4 regenerates 1. Furthermore, compound 1 also shows interesting anion sensing properties in an EtOH/H2O mixture.     

Dawson型杂多酸钕盐催化氧化甲苯制备苯甲醛

合成了Dawson型磷钼钒杂多酸稀土(钕)盐,并用红外光谱分析(IR)、X射线衍射(XRD)方法对催化剂进行了表征;以H2O2为氧化剂,进行了甲苯氧化制备苯甲醛的反应研究.由于钕和钒的协同作用,催化剂表现出高的活性.实验结果表明,甲苯的转化率90.1%,苯甲醛的选择性达51.0%,双氧水的转化率89.0%,双氧水的有效利用率43.1%.基于对杂多酸盐结构的研究,对反应机理进行了初步的探讨.     

Assembling metal phosphonates in the presence of monodentate-terminal and bidentate-bridging pyridine ligands. Use of non-covalent and covalent-coordinate interactions to build polymeric metal-phosphonate architectures

The cubic transition metal phosphonates [(t)BuPO3M(2-apy)]4 (M= Zn (1), Co (2)), whose core resembles the D4R SBU of zeolites, have been synthesized from a reaction between the corresponding metal acetate, tert-butylphosphonic acid and 2-aminopyridine (2-apy) at room temperature. X-Ray structure determination reveals that the molecules of 1 and 2, which crystallize in the tetragonal I4(1)/a space group with crystallographically imposed 4 symmetry, form a 3-D supramolecular assembly aided by N-H...O hydrogen bonding. When the same reaction was carried out by using a bridging bidentate Lewis base such as 4,4'-bipyridine, insoluble precipitate is obtained for both zinc and cobalt. In the case of other metal salts such as copper, manganese and nickel, however, one-dimensional polymeric compounds such as [M((t)BuPO3H)2(4,4'-bipy)(H2O)2]n (M= Cu (3), Mn (4)), [(Ni(4,4'-bipy)(H2O)4)((t)BuPO3H)2(H2O)]n (5) have been isolated. The solid-state structures of 3-5 have been determined by single crystal X-ray diffraction studies. Compounds 3 and 4 are isostructural and crystallize in the triclinic P1 space group with two phosphonate ligands coordinated to the metal centers in a [1.100] fashion, whereas in the case of compound 5, the polymeric backbone is formed by Ni-4,4'-bipy units and the phosphonate anions show no bonding interaction to the metal. The 1-D polymeric chains of 3-5 organize in the solid-state as 3-D supramolecular assemblies with the aid of extensive hydrogen bonding interaction between coordinated water molecules and P-OH or P=O groups of the phosphonate ligands.     

杂多酸(盐)及单缺位磷钨杂多化合物在醇类氧化反应中的催化活性

在相转移条件下,研究了杂多化合物在苄醇,环己醇氧化反应中的催化活性.六种Keggin结构杂多酸的催化活性按GeMo~12(H~4GeMo~12O~40的简写,其余类推,PW~12,PMo~12,SiMo~12,GeW~12,SiW~12顺序下降,杂多酸中的质子可分别被其它阳离逐渐取代而达到酸性修饰. H~3PW~12O~40随着其质子逐步被Na^+取代,酸性下降,催化活性大大提高;杂多酸(盐)的催化活性随体系pH值的改变将发生奇妙剧烈的变化;单缺位杂多化合物显示出较饱和杂多酸(盐)更高催化活性.溶剂对催化活性有明显影响.     

Molecular architectures for trimetallic d/f/d complexes: structural and magnetic properties of a LnNi2 core

A series of cationic, trimetallic d/f/d complexes have been prepared which use a multidentate, macrocyclic amine phenol ligand to coordinate divalent first row d-block transition metal ions (TM) and lanthanides (Ln) ions in close proximity, desirable for magnetic studies. Isolable complexes of the d/f/d cluster compounds with the formula [Ln(TM)2(bcn)2]ClO4.nH2O, where H3bcn is tris-N, N', N'-(2-hydroxybenzyl)-1,4,7-triazacyclononane, TM = Zn(II) and Ni(II) and Ln = La(III), Nd(III), Gd(III), Dy(III), and Yb(III), were synthesized by a one-pot sequential reaction of stoichiometric amounts of H 3bcn with the TM(II) and Ln(III) metal ions. The spontaneously formed cationic complexes were characterized by a variety of analytical techniques including IR, NMR, +ESI-MS, and EA. The [TM(Hbcn)].nH2O and [TM3(bcn)2].nH2O complexes were also synthesized to probe the building blocks of the d/f/d coaggregated species. The solid-state X-ray crystal structures of [GdNi2(bcn)2(CH3CN)2]ClO4.CH3CN and [GdZn2(bcn)2(CH3CN)2]ClO4.CH3CN were determined to be nearly identical with each TM(II) encapsulated in an octahedral geometry by the N3O3 binding pocket of the bcn (3-) ligand. The eight coordinate Gd(III) was bicapped by two [TM(bcn)](-) moieties and coordinated by two solvent molecules. Because of the isostructurality of the [LnZn2(bcn)2]ClO4.nH2O and [LnNi2(bcn)2]ClO4.nH2O complexes, an empirical approach using the LnZn2 magnetic data was utilized to remove first-order anisotropic contributions from the LnNi2 species. Ferromagnetic spin interactions were determined for the [LnNi2(bcn)2]ClO4.nH2O complexes, where Ln = Gd(III), Dy(III), and Yb(III), while an antiferromagnetic exchange was observed for Ln = Nd(III).     

Self-assembled copper(II) coordination polymers derived from aminopolyalcohols and benzenepolycarboxylates: structural and magnetic properties

The new copper(II) or copper(II)/sodium(I) 1D coordination polymers [Cu2(Hmdea)2(mu-H2O)(mu2-tpa)]n.2nH2O (1), [Cu2(H2tipa)2(mu2-ipa)]n.4nH2O (2), [Cu2(H2tea)2Na(H2O)2(mu2-tma)]n.6nH2O (3), [Cu2(H2tea)2(mu2-ipa)]n.nH2O (4a), and [Cu2(H2tea)2{mu3-Na(H2O)3}(mu3-ipa)]n(NO3)n.0.5nH2O (4b) have been prepared in aqueous medium by self-assembly from copper(II) nitrate, aminopolyalcohols [methyldiethanolamine (H2mdea), triisopropanolamine (H3tipa), and triethanolamine (H3tea)] as main chelating ligands and benzenepolycarboxylic acids [terephthalic (H2tpa), isophthalic (H2ipa), and trimesic (H3tma) acid] as spacers. They have been characterized by IR spectroscopy, elemental and single-crystal X-ray diffraction analyses, the latter indicating the formation of unusual multinuclear metal cores interconnected by various benzenepolycarboxylate spacers, leading to distinct wavelike, zigzag, or linear 1D polymeric metal-organic chains. These are further extended to 2D or 3D hydrogen-bonded supramolecular networks via extensive interactions with the intercalated crystallization water molecules. The latter are associated, also with aqua ligands, by hydrogen bonds resulting in acyclic (H2O)3 clusters in 1, (H2O)8 clusters in 2, infinite 1D water chains in 3, and disordered water-nitrate associates in 4b, all playing a key role in the structure stabilization and its extension to further dimensions. Variable-temperature magnetic susceptibility measurements have shown that 1-4 exhibit a moderately strong ferromagnetic coupling through the alkoxo bridge. The small Cu-O-Cu bridging angle and the large out-of-plane displacement of the carbon atom of the alkoxo group accounts for this behavior. The magnetic data have been analyzed by means of a dinuclear and a 1D chain model, and the magnetic parameters have been determined. The magnetic exchange coupling in 3, to our knowledge, is the highest found in alkoxo-bridged copper(II) complexes.     

Crystal engineering of a versatile building block toward the design of novel inorganic-organic coordination architectures

Six novel inorganic-organic coordination supramolecular networks based on a versatile linking unit 4-pyridylthioacetate (pyta) and inorganic Co(II), Cu(II), Ag(I), Zn(II), Mn(II) and Pb(II) salts have been prepared in water medium and structurally characterized by single-crystal X-ray diffraction analysis. Reaction of CoCl(2).6H(2)O with Hpyta afforded a neutral mononuclear complex [Co(pyta)(2)(H(2)O)(4)](1), which exhibits a two-dimensional (2-D) layered architecture through intermolecular O-HO interactions. Reaction of CuCl(2.2H(2)O with Hpyta yielded a neutral one-dimensional (1-D) coordination polymer [[Cu(pyta)(2)(H(2)O].0.5H(2)O](n)(2) consisting of rectangle molecular square units, which show a three-dimensional (3-D) supramolecular network through S...S and O-H...O weak interactions. However, when AgNO(3), Zn(OAc)(2).2H(2)O or MnCl(2).4H(2)O salts were used in the above self-assembled processes, the neutral 2-D coordination polymers [Ag(pyta)](n)(3), [[Zn(pyta)(2)].4H(2)O](n)(4) or [[Mn(pyta)(2)(H(2)O)]](n)(5) with different topologies were obtained, respectively. While substituting the transition metal ions used in 1-5 with Pb(OAc)(2).3H(2)O, a one-dimensional coordination polymer [Pb(pyta)(2)](n)(6), which shows a novel 2-fold interpenetrating 2-D supramolecular architecture through weak SS interactions, was isolated. It is interesting to note that the building block pyta anion exhibits different configurations and coordination modes in the solid structures of complexes 1-6. These results indicate that the versatile nature of this flexible ligand, together with the coordination preferences of the metal centers, play a critical role in construction of these novel coordination polymers or supramolecules. The spectral and thermal properties of these new materials have also been investigated.     

B(C6F5)3‐Catalyzed Selective Chlorination of Hydrosilanes

The chlorination of Si−H bonds often requires stoichiometric amounts of metal salts in conjunction with hazardous reagents, such as tin chlorides, Cl₂, and CCl₄. The catalytic chlorination of silanes often involves the use of expensive transition‐metal catalysts. By a new simple, selective, and highly efficient catalytic metal‐free method for the chlorination of Si−H bonds, mono‐, di‐, and trihydrosilanes were selectively chlorinated in the presence of a catalytic amount of B(C₆F₅)₃ or Et₂O⋅B(C₆F₅)₃ and HCl with the release of H₂ as a by‐product. The hydrides in di‐ and trihydrosilanes could be selectively chlorinated by HCl in a stepwise manner when Et₂O⋅B(C₆F₅)₃ was used as the catalyst. A mechanism is proposed for these catalytic chlorination reactions on the basis of competition experiments and density functional theory (DFT) calculations.     

六次甲基四胺与H_nXMo_(12)O_(40)·mH_2O(X=P,Si,Ge)电荷转移盐的合成、表征及二阶非线性光学性质

合成了由六次甲基四胺与Ｈ３ＰＭｏ１２Ｏ４０·ｎＨ２Ｏ,Ｈ４ＳｉＭｏ１２Ｏ４０·ｎＨ２Ｏ 和Ｈ４ＧｅＭｏ１２ Ｏ４０·ｎＨ２Ｏ 形成的具有二阶非线性光学性质的电荷转移盐,并由元素分析,红外光谱,电子光谱进行了表征。结果表明六次甲基四胺分子中有两个Ｎ 原子参与盐的形成,固体中阴阳离子之间存在强的相互作用;非线性光学性质研究表明,三种电荷转移盐的倍频效应分别为ＫＤＰ和０．０２ ,０ ．１１ 和０．０６ 倍。     

Synthesis, characterization and thermal studies on metal complexes of new azo compounds derived from sulfa drugs

Four new azo ligands, L1 and HL2-4, of sulfa drugs have been prepared and characterized. [MX(2)(L1)(H(2)O)(m)].nH(2)O; [(MX(2))(2)(HL2 or HL3)(H(2)O)(m)].nH(2)O and [M(2)X(3)(L4)(H(2)O)].nH(2)O; M=Co(II), Ni(II) and Cu(II) (X=Cl) and Zn(II) (X=AcO); m=0-4 and n=0-3, complexes were prepared. Elemental and thermal analyses (TGA and DTA), IR, solid reflectance spectra, magnetic moment and molar conductance measurements have accomplished characterization of the complexes. The IR data reveal that HL1 and HL2-3 ligands behave as a bidentate neutral ligands while HL4 ligand behaves as a bidentate monoionic ligand. They coordinated to the metal ions via the carbonyl O, enolic sulfonamide S(O)OH, pyrazole or thiazole N and azo N groups. The molar conductance data reveal that the chelates are non-electrolytes. From the solid reflectance spectra and magnetic moment data, the complexes were found to have octahedral, tetrahedral and square planar geometrical structures. The thermal behaviour of these chelates shows that the water molecules (hydrated and coordinated) and the anions are removed in a successive two steps followed immediately by decomposition of the ligand in the subsequent steps. The activation thermodynamic parameters, such as, E*, DeltaH*, DeltaS* and DeltaG* are calculated from the TG curves applying Coats-Redfern method.     

An allosteric synthetic catalyst: metal ions tune the activity of an artificial phosphodiesterase

A trinuclear metal complex of general formula (L-H)M3(Mf)2 represents the first allosteric low molecular weight catalyst. L is a polyaza ligand having a tetradentate and two bidentate metal binding sites, Ms is a "structural" (allosteric) metal, and Mf are functional (catalytic) metals which interact with a substrate. In mononuclear [(L-H)Ms]+ complexes [(L-H)Cu(MeOH)]ClO4 (1a). [(L-H)Cu]NO3 x 2H2O (1b), [(L-H)Ni]ClO4 x 4H2O (2), and [(L-H)Pd]ClO4 x 2H2O (3), prepared from L and M2+ salts, the metal is strongly bound by an in-plane N4-coordination (confirmed by X-ray crystal structure determination of la). Formation of trinuclear complexes [(L-H)MsCu2]5+, with two functional Cu2+ ions coordinated to the bidentate sites of L, was evidenced in solution by photometric titration and by isolation of [(L-H)Cu3][PO4][ClO4]2 x 9H2O (4). The trinuclear complexes catalyze the cleavage of RNA-analogue 2-(hydroxypropyl)-p-nitrophenyl phosphate (HPNP), an activated phosphodiester. From a kinetic analysis of the cleavage rate at various HPNP concentrations, parameters KHPNP (the equilibrium constant for binding of HPNP to [(L-H)MsCu2]5+ and kcat (first-order rate constant for cleavage of HPNP when bound to the catalyst) were derived: KM= 170 (Ms= Cu2+), 340 (Ms = Ni2+), 2,600 (Ms = Pd2+) M(-1), kcat = 17 x 10(-3) (Ms= Cu2+) 3.1 x 10(-3) (Ms=Ni2+), 0.22 x 10(-3) (Ms = Pd2+) s(-1). Obviously, the nature of the allosteric metal ion Ms strongly influences both substrate affinity and reactivity of the catalyst [(L-H)MsCu2]5+. Our interpretation of this observation is that subtle differences in the ionic radius of Ms and in its tendency to distort the N4-Ms coordination plane have a significant influence on the conformation of the catalyst (i.e., preorganization of functional Cu2+ ions) and thus on catalytic activity.     

Design of novel bilayer compounds of the CPO-8 type containing 1D channels

The reaction between Zn(NO3)2.6H2O and 5-aminoisophthalic acid (aip) in a mixture of diethylformamide (DEF) and ethanol resulted in [Zn(C8H5NO4)(C5H11NO)]n (CPO-8-DEF). This compound is composed of infinite 2D layers with tetrahedral Zn atoms and aip ligands in a triangular topology. The DEF molecules are bonded to Zn, and within each layer, the DEF molecules are oriented in the same direction, while in the subsequent layer, the DEF molecules are oriented in the opposite direction. By introduction of the pillaring ligands 4,4-bipyridine (BPY), 1,2-di-4-pyridylethylene (DPE), 1,2-di-4-pyridylethane (DPA), and 1,3-di-4-pyridylpropane (DPP) into mixtures of N,N'-dimethylformamide and water with Zn(NO3)2 and aip, we have successfully synthesized a series of related pillared bilayer compounds with the same common triangular Zn(aip) layer structural motif as that observed in CPO-8-DEF. The compounds are denoted as CPO-8-BPY ([Zn(C8H5NO4)(C10H8N2)(0.5)]n.3nH2O), CPO-8-DPE ([Zn(C8H5NO4)(C12H10N2)(0.5)]n.2.5nH2O), CPO-8-DPA ([Zn(C8H5NO4)(C12H12N2)(0.5)]n.2.5nH2O), and CPO-8-DPP ([Zn(C8H5NO4)(C13H14N2)(0.5)]n.3nH2O). In all cases, the pillars create spaces inside the bilayers that result in 1D channels running along the [010] directions with dimensions of 3.5 x 6.7 A(2). These channels contain water molecules that can be removed on heating to 150 degrees C, resulting in porous structures. The crystal structures of these porous high-temperature variants have been determined on the basis of powder X-ray diffraction data. All of the compounds show preferential adsorption of H2 over N2 at 77 K.     

Influence of the crystal field stabilization energy of metal(II) ions on the structural distortion of matrix-isolated SO4(2-) guest ions in selenate matrices

Infrared spectra of metal(II) selenate hydrates (MeSeO4.nH2O and Na2Me(SeO4)2.2H2O; n=6, 5, 4, 1; Me=Mg, Mn, Co, Ni, Cu, Zn, Cd) containing matrix-isolated SO42- guest ions are reported and discussed with respect to the S-O stretching modes 3 and 1. An adequate measure for the SO42- guest ion distortion is the site group splitting deltanuas (deltanuab and deltanuac in the case of a doublet and a triplet for 3, respectively; a, being the highest wavenumbered component of nu3) and deltanumax (the difference between the highest and the lowest wave numbered S-O stretching modes). It has been shown that the SO42- guest ion distortion depends on both the number of the sulfate oxygen atoms involved in coordinative bonds with the metal(II) ions and the electronic configuration of the metal(II) ions, i.e. their crystal field stabilization energy (CFSE) additionally to the site symmetry and the local potential at the lattice site of the host lattice. The SO42- guest ions matrix-isolated in MeSeO4.H2O (Me=Mn, Co, Zn) and in Na2Me(SeO4)2.2H2O (Me=Mn, Cu, Cd) exhibit three bands corresponding to the nu3 modes as deduced from the site group analysis and deltanuab approximately equal to deltanubc. When SO42- guest ions are incorporated in the triclinic Na2Me(SeO4)2.2H2O host lattices (Me=Co, Ni, Zn) the nu3 stretching region resembles a higher local symmetry of the SO42- guest ions (an approximate (A1 + E) splitting) than the crystallographic one (i.e. deltanuab>deltanubc instead of deltanuab approximately equal to deltanubc) and, hence, the ratio deltanuab/deltanubc has to be taken into account (the higher value of the ratio deltanuab/deltanubc, the weaker is the distortion of the SO42- guest ions). The SO42- guest ions incorporated in MeSeO4.nH2O (n=6, 5, 4) exhibit a higher local symmetry of the guest ions than that deduced from the site group analysis (D2d for the SO42- guest ions in MeSeO4.5H2O, MeSeO4.4H2O and in the monoclinic MeSeO4.6H2O host lattices and close to Td in the tetragonal MeSeO4.6H2O host lattices). The analysis of the infrared spectra of selenate host lattices containing SO42- guest ions reveals that the guest ions are stronger distorted when the adjacent metal(II) ions have CFSE not equal to 0. These ions are more resistant to angular deformations of the MeO6-octahedra (i.e. changes in the O-Me-O bond angles), thus facilitating the SO42- guest ion distortion as compared to those having CFSE=0 which allow stronger angular deformations of the respective metal octahedra. Infrared spectra of kieserite-type compounds MeSeO4.H2O (Me=Mn, Co, Zn) containing matrix-isolated SO42- guest ions and Me'2+ guest ions different from those of the host ions (i.e. Me'SO4.H2O in MeSeO4.H2O) are also presented and discussed (double matrix-spectroscopy).     

Cation radii induced structural variation in fluorescent alkaline earth networks constructed from tautomers of a nucleobase analogue

Nucleobase tautomers and their metal complexes have attracted considerable attention due to their fascinating architectures along with wide applications. In this paper, 4,6-dihydroxypyrimidine (H(2)DHP), an analogue of uracil and thymine, was employed to react with the vital elements of alkaline earth metals in an aqueous solution and lead to the formation of four novel complexes, [Mg(HDHP)(2) (H(2)O)(4)] (1), [Ca(HDHP)(2)(H(2)O)(3)](n)·nH(2)O (2), [Sr(HDHP)(2)(H(2)O)(3)](n)·nH(2)O (3), and [Ba(HDHP)(2)(H(2)O)(2)](n)·nH(2)O (4), which have been characterized by elemental analysis, IR, TG, UV-Vis, PL, powder and single-crystal X-ray diffraction and progressively evolve from zero-dimensional (0D) mononuclear, one-dimensional (1D) zig-zag double chain, two-dimensional (2D) double layer, to a three-dimensional (3D) porous network along with the increase of cation radii. This tendency in dimensionality follows salient crystal engineering principles and can be explained by considering factors such as hard-soft acid-base principles and cation radii. The deprotonated H(2)DHP ligand exhibits four new coordination modes, namely, O-monodentate (complex 1), N,O-chelating (complexes 2 and 3), O,O-bridging (complexes 2 and 3), and κ(1)O:κ(2)O-bridging mode (complex 4). Interestingly, the structural investigation indicates that the HDHP(-) monoanion shows three unusual types of tautomers, which are essential for the diagnosis of disease and investigation of medicine. Furthermore, the four complexes exhibit strong blue emission compared to free H(2)DHP ligand at room temperature and may be potential candidates for blue fluorescent biological materials used in organisms.