Electronic configurations and isotope shifts of the energy levels of the neutral dysprosium atom

Electronic configurations of the energy levels of the neutral dysprosium atom have been suggested on the basis of isotope shift studies carried out in the first spectrum of dysprosium using highly enriched isotopes excited in liquid-air-cooled hollow cathode lamps and a photoelectric recording Fabry-Perot spectrometer. Isotope shift Δ T(164-160) have been evaluated for 85 even and 82 odd energy levels. The configurations 4f⁹d6s6p, 4f⁹6p6s² and 4f¹⁰6s6d along with two new configurations 4f⁹5d²6p and 4f¹⁰6p² have been assigned to even levels whereas the configurations 4f⁹5d²6s, 4f¹⁰6s6p and 4f¹⁰5d6p have been assigned to some odd energy levels of the neutral dysprosium atom.     

Heteroarenium salts in synthesis. Highly functionalized tetra- and pentasubstituted pyridines

Activation of chloropyridines by heteroarenium substituents allows sequential substitutions by O-, N-, and S-nucleophiles. Reaction of 2,3,5,6-tetrachloropyridine and 4-ethylsulfanyl-2,3,5,6-tetrachloropyridine with 4-(dimethylamino)pyridine, 4-(pyrrolidin-1-yl)pyridine, or 4-aminopyridine results in the formation of 2,6-bis-heteroarenium substituted 3,5-dichloropyridines. On nucleophilic displacement of the heteroarenium substituents by O-, N-, or S-nucleophiles highly functionalized 3,5-dichloropyridines form which possess N²,S⁴,N⁶-, O²,S⁴,O⁶-, O²,O⁶-, N²,N⁶-, and S²,S⁶-substitution patterns.     

Spectral Properties and Photochemical Activity of Chalcone Derivatives

A relationship is found between spectral-luminescent and photochemical properties for mono- and disubstituted chalcone derivatives ^R1CO-CH = CHR² [R¹, R² = Ph, 4-FC₆H₄, 4-BrC₆H₄, 2-furyl, 2-thienyl, 4-(PhCONH)C6H4, 4-NH₂C₆H₄, 4-Me₂NC₆H₄].     

Reaction of ethyl 4-aryl-6-bromomethyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates with N-methylmorpholinium 3-cyano-1,4-dihydro- and 3-cyano-1,4,5,6-tetrahydropyridine-2-thiolates

Alkylation of N-methylmorpholinium 4-Ar¹-3-cyano-6-oxo-1,4,5,6-tetrahydropyridine-2-thiolates using ethyl 4-Ar-6-bromomethyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates (10 % KOH, DMF) gives mixtures of diastereomers of ethyl 4-Ar-6-[(4-Ar¹-3-cyano-1,4,5,6-tetrahydropyridin-2-ylthio)methyl]-1-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates in overall 30-58 % yield. Under these conditions the N-methylmorpholinium 4-Ar1-5-(N-Ar²-carbamoyl)-3-cyano-6-methyl-1,4-dihydropyridine-2-thiolates undergo aromatization of the dihydropyridine ring to give ethyl 4-Ar-6-[4-Ar¹-5-(N-Ar²-carbamoyl)-3-cyano-6-methylpyridin-2-ylthio)methyl]-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates (37-51 %). In the absence of KOH, only the substituted pyridine-2(1 H)-thione is formed as a product of oxidation of the dihydropyridine ring in the starting substrate. Some of the alkylation products obtained possess weak or moderate antibacterial activity towards the specific strains of Escherichia coli and Bacillus subtilis but are inactive towards Candida albicans and Staphylococcus aureus.     

Fluorescent chemosensors containing a Ru(tpy)2 2+ core and open-chain polyazaalkanes

4-[4-(Bromomethyl)phenyl]-2,2:6,2-terpyridine reacts with triethylenetetraamine or tetraethylenepentaamine in CH₂Cl₂ to yield the ligands L¹ and L², respectively. Reaction of L¹ and L² with Ru(mtpy)Cl₃ (mtpy = 4-methyl-2,2:6,2-terpyridine) in MeOH yielded, after column chromatography and precipitation with [NH₄][PF₆], the compounds [Ru(L¹)(mtpy)][PF₆]₂ and [Ru(L²)(mtpy)][PF₆]₂. These metallo-receptors contain triethylenetetraamine or tetraethylenepentaamine recognition sites and [Ru(tpy)₂]²⁺ cores as fluorescent signalling subunits. The fluorescent behaviour of [Ru(L¹)(mtpy)]²⁺ and [Ru(L²)(mtpy)]²⁺ in the presence of metal ions and anions has been studied in MeCN:H₂O (70:30 v/v) as a function of the pH.     

Intramolecular dehydrofluorinative coupling of η-arene and fluoroarylphosphine ligands in ruthenium complexes

NMR studies of reactions between a series of arene ruthenium(II) fluoroarylphosphine complexes and Proton Sponge have revealed the necessary conditions for intramolecular dehydrofluorinative ligand coupling. The complex must be cationic, and the phosphine need have only one fluoroaryl substituent. The reaction is rapid and clean for [(η⁶-toluene)RuCl(dfppe)]BF₄, [(η⁶-mesitylene)RuCl{(C₆F₅)₂PC₆H₄SMe}]BF₄ and the diastereomer of [(η⁶-toluene)RuCl{Ph₂PC₂H₄PPh(C₅F₄N-4)}]BF₄ in which the tetrafluoropyridyl substituent is close to the η⁶-arene. [(η⁶-p-cymene)RuCl(dfppe)]BF₄ reacts in the presence of Proton Sponge to give a mixture of unidentified compounds. The neutral complex [(η⁶-toluene)RuCl₂{Ph₂P(C₆F₅)}] and the diastereomer of [(η⁶-toluene)RuCl{Ph₂PC₂H₄PPh(C₅F₄N-4)}]BF₄ in which the tetrafluoropyridyl substituent is distant to the η⁶-arene do not undergo reaction.     

Synthesis,crystal structures,and infrared spectroscopy of a series of lanthanide phosphonoacetate coordination polymers

Hydrothermal reactions of lanthanide chloride, phosphonoacetic acid (H₂O₃PCH₂COOH), and water in the presence of HCl provide a series of lanthanide coordination polymers. FT-IR spectra confirm that there are three kinds of structures among seven complexes, {[Ln₂(O₃PCH₂CO₂)₂(H₂O)₃]?·?H₂O}_∞ (type I) (Ln?=?La^III for 1; Pr^III for 2; Nd^III for 3 and Eu^III for 4), [Ln(O₃PCH₂CO₂)(H₂O)₂]_∞ (type II) (Ln?=?Tb^III for 5), and [Ln(O₃PCH₂CO₂)(H₂O)₂]_∞ (type III) (Ln?=?Ho^III for 6 and Yb^III for 7). Complexes 1–5 show 2-D 4,4,5,5-connected (4⁴?·?6²)(4⁵?·?6)(4⁶?·?6⁴)(4⁸?·?6²) topology networks and 2-D 4-connected (4⁴?·?6²) topology networks and then are further linked into 3-D supramolecular networks by hydrogen-bonding interactions; 6 and 7 both exhibit a 3-D 4-connected (4²?·?6³?·?8) topology with 1-D dumbbell-shaped channels. The results indicate infrared spectroscopy is in accord with the result of single-crystal X-ray analysis.     

5-fluorouracyl. Molecular structure in the gas phase

By means of gas electronography studies combined with nonempirical calculations (BLYP/6-31G*) data on the structure of 5-fluorouracyl corresponding to the theoretical calculations were obtained. Some propeties of 5-fluorouracyl as compared to its isomer, 6-fluorouracyl, were studied. Main geometrical parameters of 5-fluorouracyl molecule are as follows: interatomic distances (r _α, Å) N¹-C¹ 1.396(1), N³-C⁴ 1.412(1), C⁴-C⁵ 1.452(1), C³=C⁶ 1.452, C⁶-C¹ 1.349, C-F 1.337(2); bond angles, deg: N¹C²N³ 113.6(2), C²N³C⁴ 128.9(5), N³C⁴C⁵ 113.0(2), C⁴C⁵C⁶ 120.2(3), C⁵C⁶N¹ 121.1(4), C⁶N¹C² 123.3(4), FC⁵C⁶ 120.3. Pyrimidine cycle was regarded as planar according to the quantum chemical calculations. Comparative analysis of difference in 5- and 6-fluorouracyl + H₂O systems was carried out.     

Intraconfigurational absorption spectroscopy of ReCl2−6 in various A2MCl6 host crystals

Low-temperature absorption and excitation spectra for Re⁴⁺ in distorted substitutional sites in K₂SnCl₆, [N(CH₃)₄]₂SnCl₆, [N(C₂H₅)₄]₂SnCl₆, [N(C₃H₇)₄]₂SnCl₆, and K₂SnBr₆ as well as in pure K₂ReCl₆ are discussed in comparison with the absorption spectra of Re⁴⁺ in cubic K₂PtCl₆, Cs₂ZrCl₆, and (NH₄)₂SnCl₆. Our data indicate that the effects of lowered symmetry are in general small and that the spectra can be interpreted in a manner paralleling earlier studies of Re⁴⁺ in cubic environments. Effects of reduced host symmetry appear to be smaller for this Kramers' ion than was previously noted for Os⁴⁺, a d⁴ system, but about equivalent to those noted for Ir⁴⁺, a d⁵ system, in the same host crystals. Origin shifts do not vary monotonically with cation size but do parallel results seen in Ir⁴⁺. In the N(C₂H₅)⁺₄ and N(C₃H₇)⁺₄ containing host crystals a significant splitting was found that correlated to two substitutional sites with parallel vibronic patterns. Low-symmetry splitting of U′_g states tended, on the contrary, to yield two sets of vibronic side bands with different intensity patterns which is an aid to assignment of the electronic state component.     

Oligotriarylamines with a Pyrene Core: A Multicenter Strategy for Enhancing Radical Cation and Dication Stability and Tuning Spin Distribution

Monoamine 1 , diamines 2 – 4 , triamine 5 , and tetraamine 6 have been synthesized by substituting dianisylamino groups at the 1‐, 3‐, 6‐, and/or 8‐positions of pyrene. Diamines 2 – 4 differ in the positions of the amine substituents. No pyrene–pyrene interactions are evident in the single‐crystal packing of 3 , 4 , and 6 . With increasing numbers of amine substituents, the first oxidation potential decreases progressively from the mono‐ to the tetraamine. These compounds show intense charge‐transfer (CT) emission in CH₂Cl₂ at around 530 nm with quantum yields of 48–68 %. Upon stepwise oxidation by electrolysis or chemical oxidation, these compounds were transformed into radical cations 1 ^?+– 6 ^?+ and dications 2 ²⁺– 6 ²⁺, which feature strong visible and near‐infrared absorptions. Time‐dependent density functional theory studies suggested the presence of localized transitions from the pyrene radical cation and aminium radical cation, intervalence CT, and CT between the pyrene and amine moieties. Spectroscopic studies indicated that these radical cations and dications have good stability. Triamine 5 and tetraamine 6 formed efficient CT complexes with tetracyanoquinodimethane in solution. The results of EPR spectroscopy and density functional theory calculations suggested that the dications 2 ²⁺– 4 ²⁺ have a triplet ground state, whereas 5 ²⁺ and 6 ²⁺ have a singlet ground state. The dication of 1,3‐disubstituted diamine 4 exhibits a strong EPR signal.     

Chemistry of Benzocyclopropenes. 1H-and 13C-NMR. Spectra of 2, 5-dideuterio-1-fluorobenzocyclopropenium ion

Preparation of 1, 1-difluorobenzocyclopropene (4) and of its 2, 5- and 3, 4-dideuterio derivatives 4a and 4b is reported. Upon ionization in cold fluorosulfonic acid, 4 affords 1-fluorobenzocyclopropenium ion (6) . ¹H- and ¹³C-NMR. spectra of 4 and 6 are assigned on the basis of the data for the specifically deuteriumlabelled compounds 4a and 6a . Hydrolysis of 6a leads to 2, 5-dideuteriobenzoic acid (7a) .     

Synthesis of substituted 4-([1,2,4]triazolo[3,4-<Emphasis Type="Italic">b</Emphasis>]-[1,3,4]thiadiazol-6-yl)quinolines

4-Amino-5-R¹-4H-1,2,4-triazole-3-thiols react with 2-R²-6-R³-quinoline-4-carboxylic acids in phosphoryl chloride to give 2-R²-6-R³-4-(3-R¹-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazol-6-yl)quinolines.     

Syntheses,Structures, and Properties of Phosphorescent Iridium(III) Complexes Containing N‐Heterocyclic Carbene Ligands

The organic salts 1‐(2‐pyridylmethyl)‐3‐alkylbenzimidazolium halide (pm‐RbH ⁺X⁻) and 1‐(2‐pyridylmethyl)‐3‐alkylimidazolium halide (pm‐R′iH ⁺X′⁻) were prepared (where R = 4‐, 3‐, 2‐fluorobenzyl ( 4f , 3f , and 2f , respectively), 4‐, 3‐, 2‐chlorobenzyl ( 4c , 3c , and 2c , respectively); 4‐methoxybenzyl (4mo); 2,3,4,5,6‐pentafluorobenzyl (f₅); benzyl (b); and methyl (m)); X = Cl and Br; R′ = benzyl (b) and methyl (m); and X′ = Cl and I. From these salts, heteroleptic Ir(III ) complexes containing one N ‐heterocyclic carbene (NHC ) ligand [Ir(κ²‐ppy)₂(κ²‐(pm‐Rb))]PF₆ (R = 4f, 1 (PF₆ ); 3f, 2 (PF₆ ); 2f, 3 (PF₆ ); f₅b, 4 (PF₆ ); 4c, 5 (PF₆ ); 3c, 6 (PF₆ ); 2c, 7 (PF₆ ); 4mo, 8 (PF₆ ); b, 9 (PF₆ ); m, 10 (PF₆ )) and [Ir(κ²‐ppy)₂(κ²‐(pm‐R′i))]PF₆ (R = b, 11 (PF₆ ); m, 12 (PF₆ )), were synthesized, and the crystal structures of 1 (PF₆ ), 2 (PF₆ ), 3 (PF₆ ), 5 (PF₆ ), 6 (PF₆ ), 7 (PF₆ ), 9 (PF₆ ), 10 (PF₆ ), and 12 (PF₆ ) were determined by X‐ray diffraction. The neutral NHC ligands 1‐(2‐pyridylmethyl)‐3‐alkylbenzimidazolin‐2‐ylidene (pm‐Rb) and 1‐(2‐pyridylmethyl)‐3‐alkylimidazolin‐2‐ylidene (pm‐R′i) of all cations were found to be involved in the intermolecular π−π stacking interactions with the surrounding cations in the solid state, thereby probably influencing the photophysical behavior in the solid state and in solution. The absorption and emission properties of all the complexes show only small variations.     

Unbridged bidentate aluminum complexes supported by diaroylhydrazone ligands: Synthesis,structure and catalysis in polymerization of ε-caprolactone and lactides

A series of novel diaroylhydrazone aluminum complexes have been synthesized and well-defined structurally, and their catalytic performance in the polymerization of ε-caprolactone and lactides have also been evaluated. Complexes [(L^1–4)₂AlMe] ( 1 – 4 ) {[L¹ = (3,5-^tBu₂–2-OMe-C₆H₂)CH=NNCOC₆H₅], [L² = (3,5-^tBu₂–2-OMe-C₆H₂)CH=NNCO(C₆H₄–4-OCH₃)], [L³ = (3,5-^tBu₂–2-OMe-C₆H₂)CH=NNCO(C₆H₄–4-Br)] and [L⁴ = (2-OMe-C₆H₄)CH=NNCO(C₆H₄–4-^tBu)]} were prepared through treatment of AlMe₃ with the corresponding proligands L^1–4H in molar ratios of 1: 1 or 1: 2. Chemical structures of all the complexes were well-defined by elemental analysis, NMR spectra as well as single-crystal X-ray study. Complexes [(L^1–4)₂AlMe] ( 1 – 4 ) in this work represent the first examples of aluminum complexes of aroylhydrazone ligands with crystallographic characterization. Specifically, they are all in monomeric form with a penta-coordinated aluminum center, including two approximately co-planar five-membered metallacycles with aluminum. Introduced bulky tert-butyl substituents in aroylhydrazone ligands could affect the geometry around the central metal which is a distorted square-based pyramid in complexes 1 – 3 while being a trigonal bipyramidal in complex 4 , thus affecting their catalytic behaviors. The complexes can successfully catalyze the ring-opening polymerization of ε-caprolactone and _L-lactide under mild conditions without any activator. In addition, complexes 1 – 4 could also polymerize rac-lactide, affording atactic polylactides with high conversions and good controllability in relatively short reaction time.     

Di-μ-chlorodichlorobis(η4-tetrakis-p-methoxyphenylcyclobutadiene)dipalladium: X-ray structure determination,spectroscopic properties,and reactions with nucleophiles

Reaction of bis-p-methoxyphenylacetylene (An₂C₂) with Na₂[PdCl₄] gave [(η⁴-An₄C₄Pd)₂Cl₃] [Pd₂Cl₆]_0.5 which with HCl gave [(An₄C₄Pd)₂Cl₄] (6). The complexes [(An₄C₄Pd)₂Y₄] (Y = Br, I, NCS, or NCO) were obtained by metathesis. Reaction of 6 with NaN₃ gave the η³-cyclobutenyl complex Na[{(N₃)An₄C₄Pd}(N₃)Cl]. With other nucleophiles OR- (6) gave the dinuclear η³-cyclobutenyl complexes [{(RO)An₄C₄Pd}₂Cl₂] (R = H, Me, Et, Prⁱ or COCH₃); AgPF₆ in the presence of L (MeCN, Bu^tNC, Me₂NC, Me₂C₂ or py) gave [(η⁴-Ar₄C₄Pd)₂Cl₂L₂][PF₆]₂ and in the presence of bipy gave [η⁴-An₄C₄Pd(bipy)Cl]PF₆. The X-ray crystal structure of the dinuclear complex 6 showed each Pd to be η⁴-coordinated to a square planar cyclobutadiene, and bound to three chlorines (two bridging and one terminal). The far IR spectra provide a useful guide to the structures of many of these complexes, but 6 is remarkable in that the spectrum between 200 and 300 cm^?1 changes dramatically on grinding.     

Synthesis and properties of monometallic, homo- and heterobimetallic complexes based on {(η-arene)RuCl} and {(η-arene)OsCl} fragments with tetrathioether and tetraselenoether ligands

The reaction of [Ru(η⁶-p-cymene)Cl₂]₂ with 2.0 mol equivalents of C(CH₂SMe)₄, C(CH₂SeMe)₄, 1,2,4,5-C₆H₂(CH₂SMe)₄ or 1,2,4,5-C₆H₂(CH₂SeMe)₄ (L₄) and [NH₄][PF₆] in ethanol solution forms the [RuCl(η⁶-p-cymene){κ²-L₄}][PF₆] complexes. Similar Os(II) complexes are obtained starting with [Os(η⁶-p-cymene)Cl₂]₂. Treatment of [RuCl(η⁶-p-cymene){κ²-L₄}][PF₆] with a further 0.5 mol equivalents of [Ru(η⁶-p-cymene)Cl₂]₂ or reaction of [Ru(η⁶-p-cymene)Cl₂]₂ directly with 1.0 mol equivalent of L₄ forms the homobimetalllic [{RuCl(η⁶-p-cymene)}₂{κ²κ′²-L₄}][PF₆]₂. Reaction of [OsCl(η⁶-p-cymene)-{κ²-C(CH₂SeMe)₄}][PF₆] with [Ru(η⁶-p-cymene)Cl₂]₂ or [PtCl₂(MeCN)₂] affords the heterobimetallic [{OsCl(η⁶-p-cymene)}{RuCl(η⁶-p-cymene)}{κ²κ′²-C(CH₂SeMe)₄}][PF₆]₂ and [{OsCl(η⁶-p-cymene)}{PtCl₂}{κ²κ′²-C(CH₂SeMe)₄}][PF₆] respectively. The complexes have been characterised by multinuclear NMR and IR spectroscopy and X-ray crystallography.     

Half-sandwich η-benzene Ru(II) complexes of pyridylpyrazole and pyridylimidazole ligands: Synthesis, spectra, and structure

New series of half-sandwich ruthenium(II) complexes supported by a group of bidentate pyridylpyrazole and pyridylimidazole ligands [(η⁶-C₆H₆)Ru(L²)Cl][PF₆] (1), [(η⁶-C₆H₆)Ru(HL³)Cl][PF₆] (2), [(η⁶-C₆H₆)Ru(L⁴)Cl][PF₆] (3), and [(η⁶-C₆H₆)Ru(HL⁵)Cl][PF₆] (4) [L², 2-[3-(4-chlorophenyl)pyrazol-1-ylmethyl]pyridine; HL³, 3-(2-pyridyl)pyrazole; L⁴, 1-benzyl-[3-(2′-pyridyl)]pyrazole; HL⁵, 2-(1-imidazol-2-yl)pyridine] are reported. The molecular structures of 1-4 both in the solid state by X-ray crystallography and in solution using ¹H NMR spectroscopy have been elucidated. Further, the crystal packing in the complexes is stabilized by C-H?X (X = Cl and π), N-H?Cl, and π-π interactions.     

N-Benzyl Derivatives of Leucine Esters

Leucine methyl and ethyl esters reacted with 3-bromobenzaldehyde and 4-chlorobenzaldehyde in anhydrous methanol in the presence of magnesium sulfate to afford the coresponding Schiff bases of the general formula (CH3)2CHCH2CH(COOR¹)N=CHR² [R¹ = CH3, C2H5, R²= 3-BrC6H4, 4-ClC6H4]. Their reduction with sodium tetrahydridoborate yielded N-benzyl derivatives (CH3)2CHCH2CH(COOR¹)NHCH2R², which were converted into N-acyl-N-benzyl derivatives (CH3)2CHCH2CH(COOR¹)N(COR³)CH2R²[R³= CH₃, C₆H₅].     

在四氯合锌离子诱导下反式六元瓜环与碱金属离子构筑的配位超分子自组装体

在盐酸介质中,通过四氯合锌离子诱导,碱金属离子能与反式六元瓜环端口羰基氧原子直接配位构筑形成超分子自组装体。单晶结构表明在HCl介质中,四氯合锌离子形成"蜂巢结构",而且在[ZnCl₄]^2-诱导作用下,碱金属离子和反式六元瓜环端口羰基氧直接配位形成一维超分子自组装体而填充在"蜂巢结构"中。     

Chemistry of 2-mercaptophenol (H2mp) . Part iii. One dimensional arrays of binuclear anions of Mo (VI) linked by bis (2-hydroxyphenyl) disulfide via hydrogen bondings

The reaction of (Bu₄N) ₄ [Mo₈O₂₆] with a suitable amount of 2-mercaptophenol (H₂mp) in MeOH in the presence of equimolar Et₃N gave the complex (Bu₄N) ₂ [{MoO₂ (2-SC₆H₄O) }₂ (μ-O) ] (2 2′-HOC₆H₄SSC₆H₄OH) 2H₂O (1) with a one-dimensional chain network formed via hydrogen bondings (average OH OMo distance 2655 Å) of the hydroxyl groups in the spacer 2 2′-HOC₆H₄SSC₆H₄OH with the terminal oxo groups of the dimolybdenum anions 2 2′-HOC₆H₄SSC₆H₄OH was obtained by oxidation of H₂mp in the presence of molybdenum when the reaction was run in air The characteristic cis-MoO₂² absorptions appear at 913 and 864 cm^{−1 1} H NMR and ¹ H–¹ H COSY spectra characterized the phenyl protons of the mercaptophenol groups in the anion and in 22′-HOC₆H₄SSC₆H₄OH in the ranges of 6700–6270 and 7368–6799 ppmrespectivelywith ³J and ⁴J coupling constants of 8 and 1 Hz respectively.