Ab initio study of the reactions of Ga((2)P, (2)S, and (2)P) with silane

The interactions of Ga((2)P:4s(2)4p(1), (2)S:4s(2)5s(1), and (2)P:4s(2)5p(1)) with SiH(4) are studied by means of Hartree-Fock self-consistent field (SCF) and multiconfigurational SCF followed by extensive variational and perturbational second-order multireference M?ller-Plesset configuration by perturbation selected by iterative process calculations, using relativistic effective core potentials. The Ga atom in its (2)P(4s(2)5p(1)) state can spontaneously insert into the SiH(4). The Ga atom in its (2)S(4s(2)5s(1)) state is inserted into the SiH(4). In this interaction the 3 (2)A(') potential energy surface initially attractive becomes repulsive after meeting the 2 (2)A(') surface linked with the Ga((2)P:4s(2)4p(1))+SiH(4) fragments. The two (2)A(') curves (2 (2)A(') and X (2)A(')) derived from the interaction of Ga((2)P:4s(2)4p(1)) atom with silane molecule are initially repulsive. The 2 (2)A(') curve after an avoided crossing with the 3 (2)A(') curve goes down until it meets the X (2)A(') curve. The 2 (2)A(') curve becomes repulsive after the avoided crossing with the X (2)A(') curve. The X (2)A(') curve becomes attractive only after its avoided crossing with the 2 (2)A(') curve. The lowest-lying X (2)A(') potential leads to the HGaSiH(3)X (2)A(') intermediate molecule. This intermediate molecule, diabatically correlated with the Ga((2)S:4s(2)5s(1))+SiH(4) fragments, which lies 1.5 kcal/mol above the ground state reactants leads to the GaH+SiH(3) or H+GaSiH(3) products through the dissociation channels. These products are reached from the HGaSiH(3) intermediate without activation barriers. This work shows that the Ga atom at its first excited state in the presence of silane molecules in gas phase leads to the formation of SiH(3) radicals, H atoms, GaH hydrides, as well as gallium silicide molecules.     

Sensing of sulfur dioxide by base metal thiolates: structures and properties of molecular NiN2S2/SO2 adducts

The cis-dithiolate N2S2Ni complex bismercaptoethanediazacycloheptanenickel(II), (bme-dach)Ni or Ni-1', takes up two equivalents of sulfur dioxide in which thiolate-sulfur to SO2-sulfur interactions are well-defined by X-ray crystallography. Ni-1' x 2SO2, C9H18N2NiO4S4, yields monoclinic crystals belonging to the P2(1)/c space group: a = 10.308(4) angstroms, b = 13.334(5) angstroms, c = 10.842(4) angstroms, alpha = 90 degrees, beta = 91.963(6) degrees, gamma = 90 degrees, and Z = 4. Further characterization by nu(SO) IR spectroscopy, thermal gravimetric analysis, electronic spectroscopy, and visual color changes upon reversible SO2 adduct formation establish Ni-1' and the analogous bismercaptoethanediazacyclooctane derivative, (bme-daco)Ni, Ni-1, to be viable candidates for technical development as chemical sensors of this noxious gas. Visual SO2 detection limits of Ni-1 and Ni-1' are established at 25 and 100 ppm, respectively. Both the Ni-1' x 2SO2 adduct and the Ni-1' reactant are air stable. In addition, the stability of Ni-1' x SO2 to vacuum and removal of SO2 by heating make Ni-1' a possible storage/controlled release complex for SO2 gas.     

Synthesis and deprotonation of 2-(pyridyl)phenols and 2-(pyridyl)anilines

2-(2- and 3-Pyridyl)anilines (1, 2), 2,2-dimethyl-N-[2-(2- and 3-pyridyl)phenyl]propanamides (3, 4), and 2-, 3- and 4-(2-methoxyphenyl)pyridines (7-9) are readily synthesized using cross-coupling reactions. Whereas the amines 1, 2 undergo side reactions, the corresponding amides 3, 4 are deprotonated with lithium 2,2,6,6-tetramethylpiperidide (LTMP): the compound 3 at C6' under in situ quenching, and the compound 4 at C4'. When the ether 7 is subjected to the same reagent, lithiation occurs at C6'.     

Polyhydroxyoligothiophenes. 2. Hydrogen-Bonding-Oriented Solid State Conformation of 3,3'-Bis(2-hydroxyethyl)-2,2'-bithiophene and Regioselective Synthesis of the Corresponding Head-to-Head/Tail-to-Tail Quater- and Sexithiophene

This paper reports the X-ray structure of 3,3'-bis(2-hydroxyethyl)-2,2'-bithiophene (1), which is the building block for the synthesis of head-to-head/tail-to-tail 2-hydroxyethyl-substituted oligothiophenes. Contrary to all the bithiophenes reported so far, 1 exhibits a noncoplanar anti conformation and an inter-ring twist angle (67.5 degrees ) which is the largest ever measured for adjacent rings of alpha-conjugated oligothiophenes. This unusual conformation appears to be dictated by intermolecular hydrogen-bonding interactions involving the OH groups, which bind the molecule in close packed layers. The paper also describes the regioselective synthesis of the dimer and the trimer of 1, namely of 3,3',4",3"'-tetrakis(2-hydroxyethyl)-2,2':5',2":5",2"'-quaterthiophene (3c) and of 3,3',4",3"',4",3"'-hexakis(2-hydroxyethyl)-2,2':5',2":5",2"':5"',2":5",2"'-sexithiophene (4b). 3c And 4b were obtained through palladium(0)-catalyzed coupling of the mono- and distannanes of the tetrahydropyranyl derivative of 1 with the appropriate monobromo compound (Stille's reaction). Finally, the paper reports force-field calculations which suggest that the low lambda(max) values measured for 1, 3c, and 4b are also the result of intramolecular hydrogen-bonding interactions which favor highly twisted conformations in solution.     

Overall considerations on the quenching of PH2(A2A1) and new effects in collision-induced V-V energy transfer of PH2(X2B1; v2' ' = 1)

The quenching constants of PH2(A(2)A1; v2' = 0 and 1) by H(2)S, NH(3), COS, CHCl(3), and CH4 have been measured. Attempts to correlate these data and those published in previous papers due to other quenchers, with the molecular properties through the Parmenter and co-workers' theory, the Thayer and Yardley's model, and the collision complex formation theory have been made. Measurements of collision-induced deactivation constants of PH2(X(2)B1; v2' ' = 1) by COS, CHCl(3), and CH4 have also been carried out. A reliable linear relationship of the log values of V-V energy exchange probability with the minimum energy mismatch Deltanu between PH2(v2' ' = 1) and the quenchers has been shown. Effects on the V-V transfer efficiency by inversion doubling of NH(3) and by the degenerate vibrational modes of the quencher, which participate in the process, have been evidenced.     

3-Hydrazino-1,2,4-triazin-5(2H)-ones in Reactions with Compounds Containing Carbonyl and Active Methylene Groups

Boiling of ethyl cyanoacetate with 6-tert-butyl-3-hydrazino-1'2'4-triazin-5(2H)-one in alkalinemedium yielded 6-tert-butyl-3-(5-hydroxy-3-oxo-2'3-dihydro-1H-pyrazol-1-yl)-1'2'4-triazin-5(2H)-one.Acylation of 6-tert-butyl-3-hydrazino-1'2'4-triazin-5(2H)-one with benzoyl chloride furnished 3-benzoyl-hydrazido-1'2'4-triazine that cyclized when treated with POCl₃ providing a derivative of[1'2'4]triazolo[4'3-b][1'2'4]triazine. Boiling of 6-tert-butyl-3-hydrazino-1'2'4-triazin-5(2H)-one in glacialacetic acid gave rise to diacetylated derivative whereas the boiling with acetic anhydride in an inert solventafforded monoacetylated product.     

3-(2'-苯基-1', 2', 3'-连三唑-4'-基)-6-烷基/芳基-均三唑并[3, 4-b]-1, 3, 4-噻二唑的合成

研究了3-(2'-苯基-1', 2', 3'-连三唑-4'-基)-4-氨基-5-巯基-1, 2, 4-三唑(1)与取代苯甲酸和脂肪酸(2a-r)在POCl3催化下的反应, 共合成得到18个新的3-(2'-苯基-1', 2', 3'-连三唑-4'-基)-6-烷基/芳基-均三唑并[3, 4-b]-1, 3, 4-噻二唑(3a-r), 经元素分析,IR, 1H NMR和MS进行了结构确证。     

Total synthesis of 2',3',4',5',5' '-(2)h(5)-ribonucleosides: the key building blocks for NMR structure elucidation of large RNA

The diastereospecific chemical syntheses of uridine-2',3',4',5',5' '-(2)H(5) (21a), adenosine-2',3',4',5',5' '-(2)H(5) (21b), cytidine-2',3',4',5',5' '-(2)H(5)(2)H(5) (21c), and guanosine-2',3',4',5',5' '-(2)H(5) (21d) (>97 atom % (2)H at C2', C3', C4', and C5'/C5' ') have been achieved for their use in the solution NMR structure determination of oligo-RNA by the Uppsala "NMR-window" concept (refs 4a-c, 5a, 6), in which a small (1)H segment is NMR-visible, while the rest is made NMR-invisible by incorporation of the deuterated blocks 21a-d. The deuterated ribonucleosides 21a-d have been prepared by the condensation of appropriately protected aglycone with 1-O-acetyl-2,3,5-tri-O-(4-toluoyl)-alpha/beta-D-ribofuranose-2,3,4,5,5'-(2)H(5) (19), which has been obtained via diastereospecific deuterium incorporation at the C2 center of appropriate D-ribose-(2)H(4) derivatives either through an oxidation-reduction-inversion sequence or a one-step deuterium-proton exchange in high overall yield (44% and 24%, respectively).     

Binding N2, N2H2, N2H4, and NH3 to transition-metal sulfur sites: modeling potential intermediates of biological N2 fixation

In the quest for low-molecular-weight metal sulfur complexes that bind nitrogenase-relevant small molecules and can serve as model complexes for nitrogenase, compounds with the [Ru(PiPr(3))('N(2)Me(2)S(2)')] fragment were found ('N(2)Me(2)S(2)'(2-)=1,2-ethanediamine-N,N'-dimethyl-N,N'-bis(2-benzenethiolate)(2-)). This fragment enabled the synthesis of a first series of chiral metal sulfur complexes, [Ru(L)(PiPr(3))('N(2)Me(2)S(2)')] with L=N(2), N(2)H(2), N(2)H(4), and NH(3), that meet the biological constraint of forming under mild conditions. The reaction of [Ru(NCCH(3))(PiPr(3))('N(2)Me(2)S(2)')] (1) with NH(3) gave the ammonia complex [Ru(NH(3))(PiPr(3))('N(2)Me(2)S(2)')] (4), which readily exchanged NH(3) for N(2) to yield the mononuclear dinitrogen complex [Ru(N(2))(PiPr(3))('N(2)Me(2)S(2)')] (2) in almost quantitative yield. Complex 2, obtained by this new efficient synthesis, was the starting material for the synthesis of dinuclear (R,R)- and (S,S)-[micro-N(2)[Ru(PiPr(3))('N(2)Me(2)S(2)')](2)] ((R,R)-/(S,S)-3). (Both 2 and 3 have been reported previously.) The as-yet inexplicable behavior of complex 3 to form also the R,S isomer in solution has been revealed by DFT calculations and (2)D NMR spectroscopy studies. The reaction of 1 or 2 with anhydrous hydrazine yielded the hydrazine complex [Ru(N(2)H(4))(PiPr(3))('N(2)Me(2)S(2)')] (6), which is a highly reactive intermediate. Disproportionation of 6 resulted in the formation of mononuclear diazene complexes, the ammonia complex 4, and finally the dinuclear diazene complex [micro-N(2)H(2)[Ru(PiPr(3))('N(2)Me(2)S(2)')](2)] (5). Dinuclear complex 5 could also be obtained directly in an independent synthesis from 1 and N(2)H(2), which was generated in situ by acidolysis of K(2)N(2)(CO(2))(2). Treatment of 6 with CH(2)Cl(2), however, formed a chloromethylated diazene species [[Ru(PiPr(3))('N(2)Me(2)S(2)')]-micro-N(2)H(2)[Ru(Cl)('N(2)Me(2)S(2)CH(2)Cl')]] (9) ('N(2)Me(2)S(2)CH(2)Cl'(2-) =1,2-ethanediamine-N,N'-dimethyl-N-(2-benzenethiolate)(1-)-N'-(2-benzenechloromethylthioether)(1-)]. The molecular structures of 4, 5, and 9 were determined by X-ray crystal structure analysis, and the labile N(2)H(4) complex 6 was characterized by NMR spectroscopy.     

Chemical and structural implications of 1',2'- versus 2',4'- conformational constraints in the sugar moiety of modified thymine nucleosides

In order to understand how the chemical nature of the conformational constraint of the sugar moiety in ON/RNA(DNA) dictates the duplex structure and reactivity, we have determined molecular structures and dynamics of the conformationally constrained 1',2'-azetidine- and 1',2'-oxetane-fused thymidines, as well as their 2',4'-fused thymine (T) counterparts such as LNA-T, 2'-amino LNA-T, ENA-T, and aza-ENA-T by NMR, ab initio (HF/6-31G** and B3LYP/6-31++G**), and molecular dynamics simulations (2 ns in the explicit aqueous medium). It has been found that, depending upon whether the modification leads to a bicyclic 1',2'-fused or a tricyclic 2',4'-fused system, they fall into two distinct categories characterized by their respective internal dynamics of the glycosidic and the backbone torsions as well as by characteristic North-East type sugar conformation (P = 37 degrees +/- 27 degrees , phi(m) = 25 degrees +/- 18 degrees ) of the 1',2'-fused systems, and (ii) pure North type (P = 19 degrees +/- 8 degrees , phi(m) = 48 degrees +/- 4 degrees ) for the 2',4'-fused nucleosides. Each group has different conformational hyperspace accessible, despite the overall similarity of the North-type conformational constraints imposed by the 1',2'- or 2',4'-linked modification. The comparison of pK(a)s of the 1-thyminyl aglycon as well as that of endocyclic sugar-nitrogen obtained by theoretical and experimental measurements showed that the nature of the sugar conformational constraints steer the physicochemical property (pK(a)) of the constituent 1-thyminyl moiety, which in turn can play a part in tuning the strength of hydrogen bonding in the basepairing.     

Formation and structure elucidation of two novel spiro[2H-indol]-3(1H)-ones

The molecular structures of two byproducts 1,1'-diphenyl-3',4'-dihydrodispiro[indole-2,2'-furan-5',2'-indole]-3,3'(1H, 1'H)-dione (3) and 1,5'-diphenyl-4',5'-dihydro-3'H-spiro[indole-2,2'-pyrano[3,2-b]indol]-3(1H)-one (4), which accompanied the rearrangement of 3-hydroxy-3-methyl-1-phenylquinoline-2,4(1H,3H)-dione (1) to 2-hydroxy-2-methyl-1-phenyl-1,2-dihydro-3H-indol-3-one (2), have been elucidated by NMR, MS, and X-ray diffraction.     

6-取代氨基-2-烷硫基腺苷化合物的合成及抗血小板凝聚活性

以鸟苷(1)为原料, 经过糖环保护得到2',3',5'-三-O-乙酰基鸟嘌呤核苷(2), 化合物2与三氯氧磷反应得到2-氨基-6-氯-9-(2',3',5'-三-O-乙酰基-β-D-呋喃核糖基)嘌呤(3), 化合物3经重氮化后再与二烷基二硫醚反应得到2-烷硫基-6-氯-9-(2',3',5'-三-O-乙酰基-β-D-呋喃核糖基)嘌呤(4a~4d), 化合物4a~4d与胺进行亲核取代反应后, 脱去糖环保护得到12个新型的6-取代氨基-2-烷硫基腺苷化合物(5a~5l). 采用¹H NMR, ¹³C NMR, IR和高分辨质谱(HRMS)对目标化合物的结构进行了确证, 并对所有化合物进行了体外抗血小板聚集活性测试. 结果表明, 当测试浓度为10 μmol/L时, 化合物5a~5l仍具有一定的抗凝活性, 其中, 6-(3-苯基丙基)氨基-2-丙硫基腺苷(5d)活性最为显著, 抑制率可达90.2%.     

The possibility of the decomposition of 2'-deoxyribose moiety of thymidine induced by the low energy electron attachment

To evaluate the possibility of the decomposition of 2-deoxyribose moiety of thymidine induced by low energy electrons (LEE) attachment, the transition states and the energy barriers of the bond breaking processes of the ribose of the nucleoside have been studied theoretically by applying the density functional theory with the double zeta basis sets (DZP++). The energy barriers for the breakage of the C-C bonds (C(1')-C(2'), C(2')-C(3'), C(3')-C(4'), and C(4')-C(5')) of the ribose group of the radical anion of thymidine are found to be high (ca. 42-57 kcal/mol). The total energies of the C-C bond-broken products are significantly higher than that of the radical anion dT(*-). The decomposition of dT(*-) through the C-C bond rupture is unlikely to take place. The rupture of the C(1')-O(4') bond of dT(*-) needs an activation energy as low as 10.4 kcal/mol. However, the reversed reaction (C(1')-O(4') bond formation) needs the activation energy low as 0.3 kcal/mol. Therefore, the intermediate product LM1(C1')-(O4') is unlikely to be stable and the C(1')-O(4') bond-broken is not favored. The activation energy of the C(4')-O(4') bond rupture process amounts to 20.5 kcal/mol. The total energy of the C(4')-O(4') bond broken product is about 6.5 kcal/mol lower than that of the reactant dT(*-). The subsequent N1-glycosidic bond breaking process is found to have a very low energy barrier. Therefore, the LEE-induced base release through the C(4')-O(4') bond rupture might be a possible pathway.     

顺式和反式-2-氨基-3-氰基-4-苯基-1-(4'-甲基苯基)-2-环戊烯-1-醇的合成和晶体结构

用低价钛试剂(TiCl4-Zn)与4, 4-二氰基-3-苯基-1-(4'-甲基苯基)-1-丁酮反应合成了顺式和反式-2-氨基-3-氰基-4-苯基-1-(4'-甲基苯基)-2-环戊烯-1-醇, 并用X射线衍射分析确定了这两个异构体的构型。     

2-芳胺基-5-[5'-氨基-1'-(4"-氯苯基)-1',2',3'-三唑-4'-基]-1,3,4-噻二唑的合成

1-[5'-氨基-1'-(4"-氯苯基)-1,2,3-三唑-4'-甲酰基]-4-芳基-3-氨基硫脲在浓硫酸催化下环化得到2-芳胺基-5-[5'-氨基-1'-(4"-氯苯基)-1',2',3',-三唑-4'-基]-1,3,4-噻二唑2a-i, 依此法合成了九个标题化合物, 收率为30-74%。化合物2i的结构用X-光衍射单晶分析确证。     

Reversible transformation of ZnII coordination geometry in a single crystal of porous metal-organic framework [Zn3(ntb)2(EtOH)2].4 EtOH

A 3D porous metal-organic framework [Zn3(ntb)2(EtOH)2]n.4nEtOH (1) that generates 1D channels of honeycomb aperture has been prepared by the solvothermal reaction of Zn(NO3)(2).6 H2O and 4,4',4'-nitrilotrisbenzoic acid (H3NTB) in EtOH at 110 degrees C. Framework 1 exhibits reversible single-crystal-to-single-crystal transformations upon removal and rebinding of the coordinating EtOH as well as the EtOH guest molecules, which give rise to desolvated crystal [Zn3(ntb)2]n (1') and resolvated crystal [Zn3(ntb)2-(EtOH)2]n.4nEtOH (1'). The X-ray structures indicate that 3D host framework is retained during the transformations from 1 to 1' and from 1' to 1', but the coordination geometry of ZnII ions changes from/to trigonal bipyramid to/from tetrahedron, concomitant with the rotational rearrangement of a carboxylate plane of the NTB3- relative to its associated phenyl ring. To retain the single crystal integrity, extensive cooperative motions must exist between the molecular components throughout the crystal. Framework 1' exhibits permanent porosity, thermal stability up to 400 degrees C, and blue luminescence, and high storage capabilities for N2, H2, CO2, and CH4.     

Highly selective colorimetric and electrochemical Pb2+ detection based on TTF-pi-pyridine derivatives

[reaction: see text] The pyridineethenyl-substituted tetrathiafulvalene (TTF) compounds, 4-(4-pyridineethenyl)tetrathiafulvalene (1a) and 4,4'(5')-[bis-(4-pyridineethenyl)]tetrathiafulvalene (2a) together with the styryl-substituted TTF compounds, 4-styryltetrathiafulvalene (1b) and 4,4'(5')-bis-styryltetrathiafulvalene (2b), have been designed and synthesized. All these compounds exhibit strong absorption bands in the range of 370 to 550 nm, which are assigned to the intramolecular charge-transfer transition from the HOMO in TTF to the LUMO in the pyridyl or phenyl group. Compared to compounds 1b and 2b, the pyridineethenyl-substituted TTF compounds 1a and 2a show remarkable sensing and coordinating properties to Pb2+. With the addition of micromolar concentrations of Pb2+ to the solution, 1a or 2a displays dramatic changes in the UV-vis absorption spectrum, 1H NMR spectrum, and redox property.     

Syntheses,structures, and fluxionality of blue luminescent zinc(II) complexes: Zn(2,2',2"-tpa)Cl2, Zn(2,2',2"-tpa)2(O2CCF3)2, and Zn(2,2',3"-tpa)4(O2CCF3)2 (tpa = tripyridylamine)

Three novel Zn(II) complexes containing either 2,2',2"-tripyridylamine (2,2',2"-tpa) or 2,2',3"-tripyridylamine (2,2',3"-tpa) have been synthesized and structurally characterized. Compound 1, Zn(2,2',2"-tpa)Cl2, has a tetrahedral geometry while compounds 2, Zn(2,2',2"-tpa)2(O2CCF3)2, and 3, Zn(2,2',3"-tpa)4(O2CCF3)2, have an octahedral geometry. The 2,2',2"-tpa ligand in 1 and 2 functions as a bidentate ligand, chelating to the zinc center, while the 2,2",3"-tpa ligand in 3 functions as a terminal ligand, binding to the zinc center through the 3-pyridyl nitrogen atom. All three compounds emit a blue color in solution and in the solid state. The emission maxima for the three compounds in solution are at lambda = 422, 426, and 432 nm, respectively. The blue luminescence of the complexes is due to a pi *-->pi transition of the tpa ligand as established by an ab initio calculation on the free ligand 2,2',2"-tpa and complex 1. Compounds 1 and 2 are fluxional in solution owing to an exchange process between the coordinate and noncoordinate 2-pyridyl rings of the 2,2',2"-tpa ligand. Compound 2 is also fluxional owing to a cis-trans isomerization process, as determined by variable-temperature 1H NMR spectroscopic analysis.     

2-芳胺基-5-[5'-氨基-1'-(4''-氯苯基)-1', 2', 3'-三唑-4'-基]——-1, 3, 4-恶二唑的合成

利用1-[5'-氨基-1'-(4'-氯苯基)-1', 2', 3'-三唑-4'-甲酰基]-4-芳基氨基硫脲在汞盐Hg(OAc)2-HOAc中加热缩合, 制得11种新的2-芳胺基-5-[5'-氨基-1'-(4'-氯苯基)-1', 2', 3'-三唑-4'-基]---1, 3, 4-恶二唑。所有化合物的结构经元素分析, IR、MS以及1H NMR确认。选择代表物作生测试验, 结果表明, 2b, 2k中MIC3.1mg/L时, 对大肠杆菌及金黄色葡萄球菌繁殖有明显抑制。     

2, 5-二取代基-1, 3, 4-恶二唑及恶二唑啉类化合物的合成

2-苯基-1,2,3-连三唑-4-甲酰肼(1)与芳酸在POCl~3催化下得到6种新的2-芳基-5-(2'-苯基-1',2',3'-连三唑-4'-基)-1,3,4-恶二唑(2)。1与羰基化合物缩合得到相应的酰腙(3),在Ac~2O作用下环化成2-取代基-3-乙酰基-5-(2'-苯基-1',2',3'-连三唑-4'-基)-1,3,4-恶二唑啉(4)。化合物的结构经元素分析,IR,^1HNMR和MS确证。