Supramolecular structures of metal complexes containing barbiturate and 1,2-bis(4-pyridyl)-ethane

This work describes the synthesis, thermal, spectroscopic properties (Raman and infrared), and crystal structures of five new supramolecular compounds [Mn(bpa)(H₂O)₄]B₂?·?4H₂O (1), [Fe(bpa)(H₂O)₄]B₂?·?4H₂O (2), [Co(bpa)(H₂O)₄]B₂?·?4H₂O (3), [Zn(bpa)(H₂O)₄]B₂?·?4H₂O (4), and Co₂mal₂bpa?·?2H₂O (5), where B is the anion of barbituric acid, bpa is 1,2-bis(4-pyridyl)-ethane, and mal is malonate ion. Compounds 1–4 are isostructural, showing covalent linear 1-D [M(bpa)(H₂O)₄]²⁺ chains, which interact by hydrogen-bonding and π-stacking interactions with barbiturate and crystallization water molecules resulting in a 3-D arrangement, belonging to Pbcn space group. Compound 5 has been obtained from the opening of the barbituric acid ring, with the formation of malonate, coordinated simultaneously to three cobalts in a 1-D chain along the c-axis, whereas bpa ligand gives rise to another 1-D chain along the a- and b-axes, resulting in a 3-D coordination polymer containing cavities. The vibrational spectra of 1–4 are also very similar; Raman spectra display two intense bands related to bpa at 1616 and 1020?cm^?1, assigned to the (ν _CC/ν _CN) and ring stretching modes, respectively. The barbiturate is also confirmed by a band at 684?cm^?1; the interesting point to be emphasized is this vibrational mode is not observed for 5, corroborating the absence of this building block in the structure.     

Chains,helices, sheets and unusual 3D nets: Diverse structures of the flexible,ditopic ligand 1,2-bis(3-(4-pyridyl)pyrazolyl)ethane

The flexible ditopic ligand 1,2-bis(3-(4-pyridyl)pyrazol-1-yl)ethane (L^4Et) displays remarkable versatility in the complexes that it forms with transition metals with products ranging from 1D chains to interpenetrating 3D networks. The L^4Et ligand itself crystallises in the space group P2₁, adopting a helical twist, although it is found in a variety of other conformations in its complexes. Coordination polymers containing the L^4Et ligand vary from almost straight, parallel 1D chains of [Ag₂(L^4Et)₂(ClO₄)₂(DMF)]·DMF (1), through interdigitating helical complexes containing tetrahedral Zn(II), [Zn(NCS)₂(L^4Et)]·DMF·H₂O (2) to 2D sheets of [Cu(L^4Et)₂(H₂O)₂](PF₆)₂·xH₂O (3) and the three-fold interpenetrating 3D network of [Co(L^4Et)₂(NCS)₂] (4). The 3D network adopts an unusual 3D 4-connected dmp (6⁵.8) topology. Dimensionality can be limited by the use of chelating co-ligands, demonstrated by the formation of the dinuclear complex [{Cu(py-2,6-CO₂)(H₂O)}₂(L^4Et)] (5).     

Synthesis and properties of 2-(2-pyridyl)-1-azaazulene

The title azaazulene 3 was synthesized either by reaction of tropone with N-{(2-pyridyl)acetyl}pyridinium iodide in the presence of ammonium acetate or by palladium-catalyzed cross-coupling between 2-halo-1-azaazulene and 2-substituted pyridine. The compound shows relatively stronger basicity compared with 2,2′-bipyridyl. While 3 showed no emission from the S₁ state but from the S₂ state like azulene does, the protonated species of 3 exhibited emission from the S₁ state. Cationic metal-dependent absorption and emission relating to complexation were also studied.     

Oxovanadium(IV) complexes as molecular catalysts in epoxidation: Simple access to pyridylalkoxide derivatives

Reaction of bis(aryl)-2-pyridylmethanol ligands (1a-7a) with VO(SO₄) · 5H₂O results in the formation of metal-oxo complexes [VO(N-O)₂] (1-7), with N-O = bis(aryl)-2-pyridylmethanol. A molecular structure of (4) has been determined by single crystals X-ray diffraction study, which showed the expected square planar pyramidal geometry with the pyridine ring nitrogens in trans-position to each other. The metal-oxo complexes (1-4,6,7) demonstrated the ability to catalyse epoxidation reactions of alkenes with molecular oxygen.     

Synthesis and fluorescence properties of 7-hydroxy-3-(2-pyridyl)coumarin derivatives

Three coumarin derivatives, 7-hydroxy-3-(2-pyridyl)coumarin (HPC), 7-(4-(5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl)benzyloxy)-3-(2-pyridyl)coumarin (Ox-PC), and 7-(4-(9H-carbazol-9-yl)butoxy)-3-(2-pyridyl)coumarin (Cz-PC), were synthesized and characterized by elemental analysis, ¹H NMR, FT-IR, and UV?Cvis absorption spectra. The fluorescence behaviors of the compounds in methanol solutions and solid states were investigated. HPC exhibits weak green emission, whereas Cz-PC and Ox-PC show strong blue emissions in dilute solutions.     

Synthesis and structures of 6-methyl-1-(2-R-phenyl)-dihydropyrimidine-2,4-dione derivatives

N-Aryl--methyl--alanines were synthesized by the reaction of aromatic amines with crotonic acid. The products were converted to dihydropyrimidine-2,4-dione derivatives. Alkylation, acylotion, and oximation of 1-arylpyrimidine-2,4-diones were carried out. Conformational analysis of the compounds obtained was carried out by dynamic NMR methods.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1096–1106, August, 1990.     

主（脱铝Y分子筛纳米腔）-客（Co，Mn和Cox/Mnx三核金属簇合物）纳米复合物催化剂高效催化环己烯环氧化反应

采用模板合成法制备了在脱铝Y分子筛纳米腔中含有Co, Mn,和Co/Mn混合物的三核金属簇合物的复合物催化剂,包括[Mn3(O)(CH3COO)6-(py)3]-Y,[Co3(O)(CH3COO)6-(py)3],[Co2Mn(O)(CH3COO)6-(py)3]-Y和[CoMn2(O)(CH3COO)6-(py)3]-Y],并运用傅里叶变换红外光谱、紫外-可见光光谱、前场扫描电镜、X射线衍射和原子吸收光谱对其进行了表征.包裹的金属簇合物在环己烯环氧化反应中表现出较高的催化活性,反应以H2O2/O2为氧化剂,在加热机械搅拌下进行,所得环氧化物产率在82.5%?90.7%.在该催化体系中, NaBr用作氧化助剂可以提高反应性能.在所制多相催化体系中,含单核的金属簇合物催化活性更高,其中以Mn3(O)-DAZY化合物的效率最高.各催化剂活性顺序为Mn3(O)-DAZY> Co3(O)-DAZY> Mn2Co(O)-DAZY> MnCo2(O)-DAZY.     

Synthesis of benzene-ring-substituted 2-methyl-3-acetylquinoxaline derivatives

2-Methyl-4-acetylquinoxaline derivatives were obtained by the condensation of pentane-2,3,4-trione with 4-substituted o-phenylenediamines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1423–1424, October, 1971     

A joint electrochemical/spectroelectrochemical inspection (and re-inspection) of high-nuclearity platinum carbonyl clusters

The accurate study of the electron transfer activity of the tetraanion [Pt₁₉(CO)₂₂]⁴⁻ is presented together with that of the dianion [Pt₃₈(CO)₄₄]²⁻, which was previously studied by spectroelectrochemistry but only partially examined from the electrochemical viewpoint. The main feature of the two clusters is that they undergo a sequence of close-spaced pairs of reversible one-electron processes, which are qualitatively reminiscent of those exhibited by the dianion [Pt₂₄(CO)₃₀]²⁻. In order to focus on such unique aspect of the three structurally characterised platinum clusters, we have investigated (and reinvestigated) their electrochemical and spectroelectrochemical redox properties, also reporting on the electron paramagnetic resonance (EPR) spectrum of the monoanion [Pt₂₄(CO)₃₀]⁻, which represents the first successful study of the paramagnetism of homoleptic platinum–carbonyl clusters.     

Synthesis of big palladium clusters. Preparation of Pd23(CO)20(PEt3)8

Selective methods for the synthesis of the cluster Pd₂₃(CO)₂₀L₈, L=PEt₃, have been suggested. The compound has been prepared by two routes: by the reaction of Pd₁₀(CO)₁₂L₆ with Me₃NO in the presence of HOAc with removal of CO from the gas phase, and by the reaction of Pd₁₀(CO)₁₂L₆ with Pd(OAc)₂ and CO followed by oxidation by Me₃NO in an inert atmosphere.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1299–1300, July, 1993.     

High nuclearity metal clusters: Miniature bulk of unusual structures and properties?

Recent developments in cluster synthesis have produced many high nuclearity metal clusters of discretesize andshape approaching that of small particles. Some of these clusters have metal arrangements resemblingfragments of metallic lattices and thus may be considered as aminiature bulk. Some are related to the quasicrystalline phase. Yet others have little or no structural features in common with that of the bulk. These metal clusters of definitivesize andshape provide an opportunity for the study of the evolution of band structure fromatomic tomolecular to thebulk. The focus of this review is on the unusual structures and properties of well-defined high nuclearity metal clusters and their possible relations or variant to the bulk state. Specifically, interesting electronic, optical, and magnetic properties of metal clusters in the quantum-size regime are described. Structural systematics of high nuclearity metal clusters, ranging from thecluster-of-clusters to thelayer-by-layer growth sequence, are discussed. It is hoped that further studies of the structures and properties of large metal cluster compounds of discretesize andshape will shed light on how, when, and why metallic or other bulk behavior begins and ends.     

簇外环化镍十硼烷簇合物的合成与结构研究

研究了[NiCl~2(PPh~3)~2],B~1~0H~1~0^2^-与硫代苯甲酸的反应,得到四个簇合物,其中三个簇合物[(PPh~3)(PhCOS)~2Ni·B~1~0H~1~0]·0.5C~6H~1~4(1),[(PhCOS)~2NiB~1~0H~8(PPh~3)](2),[(PhCOS)~3NiB~1~0H~7(PPh~3)](3)。通过单晶X射线衍射进行了结构研究。三个簇合物均为十一顶巢式构型,并分别存在两个、两个、三个簇外环化的五元环,具有三个环的簇合物至今未见其它文献报道。结构分析表明：簇外环化可以增强Ni－B之间的成键作用。     

Synthesis and reactions of 1-(2-pyridyl)-3-methyl-4-chloro-5-formyl-6,7-dihydroindazoles

The Vilsmeier formylation of 1-(2-pyridyl)-3-methyl-4-oxo-4,5,6,7-tetrahydroindazole and its 6-phenyl derivative gives 1-(2-pyridyl)-3-methyl-4-chloro-5-formyl-6,7-dihydroindazoles. Reactions of these derivatives with different N- and C-nucleophilic agents, including bisnucleophiles, were studied as a means of obtaining new 4- and 5-functional derivatives of indazole and its condensed systems.Riga Technical University, Riga LV-1658, Latvia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 768–773, June, 1998.     

Some recent applications of ab initio electronic structure methods to metal,semimetal, and molecular clusters

Recent experimental and theoretical cluster studies are reviewed. Areas of current and developing interest in theoretical and computational chemistry are identified. Some promising methods applied to metal clusters, main group clusters, molecular clusters, spectroscopy, and models of cluster-molecule reactions are indicated. Results of calculations on small hydrogenated lithium clusters and hydrated sodium clusters are discussed in some detail.     

A New Polymeric Framework Formed by the Self Assembly of 5,10,15,20-tetra(3-pyridyl)porphyrin,HgI2 And C60

The X-ray structure of H₂T(3-Py)P·HgI₂·C_60, cocrystallized from a chlorobenzene/methanol solvent mixture containing 5,10,15,20- tetra(3-pyridyl)porphyrin, HgI₂ and C₆₀, has been determined. A new two dimensional arrangement of the tetra(3-pyridyl)porphyrin molecules joined by coordination to HgI₂ is formed. These assemblies are connected by close C₆₀-porphyrin π–π interactions leading to the alignment of the porphyrins into linear alternating fullerene porphyrin columns. The structure is compact with no significant cavities.     

Syntheses,crystal structures,and characterizations of two novel cubane-like and double cubane-like molybdenum-copper-sulphur clusters {MoCu3S3(S2COEt)}(O)(Ph3P)3 and {Mo2Cu6S6(SCMe3)2}(O)2(Ph3P)4

Two novel heterometallic cubane-like and double cubane-like clusters, {MoCu₃S₃(S₂COEt)}(O)(Ph₃P)₃ I and {Mo₂Cu₆S₆(SCMe₃)₂}(O)₂(Ph₃P)₄ II, were synthesized by reaction of {MoCu₂S₃}(O)(Ph₃P)₃ with CuS₂COEt and CuSCMe₃, respectively. ClusterI crystallized in the triclinic space group (2) witha=12.766(6) Å,b=22.904(5) Å,c=10.522(3) Å, =99.86(2)°, =109.68(2)°, =86.84(3)°,V=2854(2) ų,Z=2,R=0.049 for 6622 observed reflections (I>5(I)) and 410 variables. ClusterII crystallized in the triclinic space group (2) with dimensionsa=14.212(4) Å,b=14.725(5) Å,c=12.396(8) Å, =110.32(4)°, =90.40(5)°, =62.88(2)°,V=2129(2) ų,Z=1,R=0.039 for 6020 observed reflections (I>3(I)) and 461 variables. ClusterI consists of a neutral cubane-like molecule with the core {MoCu₃S₃(S₂COEt)}²⁺, in which one corner of the cubane-like core is a novel triply bridging bidentate 1,1-dithiolato (xanthate, S₂COEt^–) ligand. ClusterII is a double cubane-like one, in which two cubane-like cores {MoCu₃S₃(SCMe₃)}²⁺ are connected by two Cu-S bonds of the triply bridging monothiolato (SCMe ₃ ^– ) ligand. Two different pathways of unit construction from a small heterometallic cluster {MoCu₂S₃}(O)(Ph₃P)₃ have been outlined. Comparisons of the selected bond lengths and bond angles for the cubane-like core {MoCu₃S₃ X} (X=Cl^–, Br^–, S₂COEt^–, SCMe ₃ ^– ) are given. Spectroscopic properties of the title clusters are also reported.     

Synthesis of 2-carbethoxy-3-methyl-4-hydroxybenzofuran derivatives

A number of 2-.carbethoxy-3-methylbenzofuran derivatives were synthesized. A 5,5-gem-dibromo derivative was obtained in the bromination of 2-carbethoxy-3-methyl-4-oxo-4, 5,6,7,tetrahydrobenzofuran. Dehydrobromination of this, dibromo derivative gave 2-carbethoxy-3-methyl-4-hydroxy-5-bromobenzofuran. Depending on the structure of the starting compound and the brominating agent, the bromine in the bromination of 2-carbethoxy-3-methyl-4-hydroxy- and 4-acetoxybenzofurans with bromine and N-bromosuccinimide is incorporated either in the methyl group or in 5 and 7 positions of the benzofuran ring. The nitration of 2-carbethoxy-3-methyl-4-hydroxybenzofuran and its bromo derivative leads to 5-nitro- and 5,7-dinitrobenzofuran derivatives. The structures of the synthesized benzofuran derivatives were established by means of the PMR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 27–29, January, 1980.     

Multi-metal complexation and partially templated synthesis of metal clusters by using triangular trisaloph ligands

On the basis of the concept of partial template, triangular trisaloph ligands 2a and 2b reacted with excess Zn^II to give heptanuclear Zn clusters with a similar geometry. The Zn complex of 2c, which was difficult to be prepared according to a previous procedure, was synthesized in high yield in a one-pot fashion. Various multi-nuclear complexes of 2a with Mn, Co, Ni, and Cu were also produced, although the trinuclear Mn^II and Co^II complexes were smoothly oxidized to the Mn^III and Co^III complexes.