Experimental studies of the NaCs 5(3)Π0 and 1(a)3Σ+ states

We report high resolution measurements of 372 NaCs 5(3)Π(0)(v, J) ro-vibrational level energies in the range 0 ≤ v ≤ 22. The data have been used to construct NaCs 5(3)Π(0) potential energy curves using the Rydberg-Klein-Rees and inverted perturbation approximation methods. Bound-free 5(3)Π(0)(v, J) → 1(a)(3)Σ(+) emission has also been measured, and is used to determine the repulsive wall of the 1(a)(3)Σ(+) state and the 5(3)Π(0) → 1(a)(3)Σ(+) relative transition dipole moment function. Hyperfine structure in the 5(3)Π(0) state has not been observed in this experiment. This null result is explained using a simple vector coupling model.     

Thermodynamics of the hydrolysis reactions of adenosine 3′,5′-(cyclic)phosphate(aq) and phosphoenolpyruvate(aq); the standard molar formation properties of 3′,5′-(cyclic)phosphate(aq) and phosphoenolpyruvate(aq)

Molar calorimetric enthalpy changes Δ_rH_m(cal) have been measured for the biochemical reactions {cAMP(aq) + H₂O(l)=AMP(aq)} and {PEP(aq) + H₂O(l)=pyruvate(aq) + phosphate(aq)}. The reactions were catalyzed, respectively, by phosphodiesterase 3^′,5^′-cyclic nucleotide and by alkaline phosphatase. The results were analyzed by using a chemical equilibrium model to obtain values of standard molar enthalpies of reaction Δ_rH_m^∘ for the respective reference reactions {cAMP⁻(aq) + H₂O(l)=HAMP⁻(aq)} and {PEP³⁻(aq) + H₂O(l)=pyruvate⁻(aq) + HPO²⁻₄(aq)}. Literature values of the apparent equilibrium constants K^′ for the reactions {ATP(aq)=cAMP(aq) + pyrophosphate(aq)}, {ATP(aq) + pyruvate(aq)=ADP(aq) + PEP(aq)}, and {ATP(aq) + pyruvate(aq) + phosphate(aq)=AMP(aq) + PEP(aq) + pyrophosphate(aq)} were also analyzed by using the chemical equilibrium model. These calculations yielded values of the equilibrium constants K and standard molar Gibbs free energy changes Δ_rG_m^∘ for ionic reference reactions that correspond to the overall biochemical reactions. Combination of the standard molar reaction property values (K, Δ_rH_m^∘, and Δ_rG_m^∘) with the standard molar formation properties of the AMP, ADP, ATP, pyrophosphate, and pyruvate species led to values of the standard molar enthalpy Δ_fH_m^∘ and Gibbs free energy of formation Δ_fG_m^∘ and the standard partial molar entropy S_m^∘ of the cAMP and PEP species. The thermochemical network appears to be reasonably well reinforced and thus lends some confidence to the accuracy of the calculated property values of the variety of species involved in the several reactions considered herein.     

Organometalloidal derivatives of the transition metals: XI. Synthesis and crystal structures of Ph3GeSiMe3 and Ph3GeSiMe2Fe(CO)2(η5-C5H5)

Ph₃GeSiMe₃ and Ph₃GeSiMe₂Fe(CO)₂(η⁵-C₅H₅) have been synthesized and their crystal structures determined. The GeSi bond in iron (2.405(2) Å) is longer by 0.021 Å than in the simple germylsilane (2.384(1) Å). The significant shortening of the SiFe bond (2.328(1) Å) in the iron complex compared to that in the analogous Ph₃SiSiMe₂Fe(CO)₂(η⁵-C₅H₅) (2.346(1) Å) and spectroscopic data indicate an enhanced SiFe interaction.     

The reactions of (η5-C5H5)NiO(s)3(μ-H)3(CO)9 with group V donor ligands. Spectroscopic characterization of the disubstituted derivatives,and crystal structure of (η5-C5H5)NiO(s)3(μ-H)3(CO)7(PMe2Ph)2

The complex (η⁵-C₅H₅NiO(s)₃(μ-H)₃(CO)₉ (1 reacts with phosphines in the presence of Me₃NO to give monosubsituted derivatives, the main products, along with smaller amounts of disubstituted derivatives. The IR and NMR spectroscopic characterizations of two representative disubstituted derivatives are described.The crystal structure of (η⁵-C₅H₅)NiO(s)(μ-H)₃(CO)₇(PMe₂Ph)₂ has been determined by X-ray diffraction. The crystals are monoclinic, space group P2₁/a with Z = 4 in a unit cell of dimensions a 18.198(8), b 20.865(8), c 8.656(5) Å, β 99.67(2)°. The structure was solved by direct and Fourier methods and refined by full-matrix least-squares to R = 0.061 for 3139 observed reflections. The structure can be regarded as derived from that of 1 (which has a tetrahedral NiO(s) core with three hydride hydrogen atoms bridging the OsOs edges, a cyclopentadienyl group coordinated to the Ni atom,and nine terminal carbonyls bound to the Os atoms, three for each Os atom) by replacing two axial carbonyls by two PMe₂Ph ligands.     

Studies of the oxovanadium-organophosphonate system: Hydrothermal synthesis and crystal structure of the mixed valence cluster [V5O9(PhPO3)3(PhPO3H)2]2− and a comparison to the structure of the fully oxidized parent cluster [V5O7(OCH3)2(PhPO3)5]1−

The room temperature reaction of (Bu₄N)₃V₅O₁₄ with PhPO₃H₂ in methanol yields the pentanuclear V(V) cluster (Bu₄N)[V₅O₇(OCH₃)₂(PhPO₃)₅]·CH₃OH (1·CH₃OH). In contrast, the hydrothermal reaction of (Ph₄P) [VO₂Cl₂], PhPO₃H₂ and (NH₄)H₂PO₄ at 125°C for 96 hr yields the mixed valence V(IV)/V(V) species (Ph₄P)₂[V₅O₉(PhPO₃)₃(PhPO₃H)₂] (3). While the anions of both 1 and 3 exhibit a pentanuclear core, the structural consequences of 1-electron reduction of the fully oxidized cluster of 1 to produce 3 are quite dramatic, including reduction in coordination numbers at two vanadium sites and protonation of two phosphonate oxygen sites with concomitant structural reorganization. Crystal data: 1, monoclinic P2₁/n,a=12.167(2) Å,b=23.348(5) Å,c=22.508(5) Å,β=98.49(2)°,V=6323.9(19) ų,Z=4,D _calc=1.558 g cm^?3; 3, triclinic, $P\bar 1$ ,a=13.478(3) Å,b=14.399(3) Å,c=23.638(5) Å,α=72.53(2)°,β=85.58(2)°,γ=69.88(4)°,V=4107.0(16) ų,Z=2, D_calc=1.479 g cm^?3.     

Ligand exchange reactions of the alkyluranium(III) complexes (η5-C5H5)3URLi

The Cp₃URLi compounds (Cp = η⁵-C₅H₅; R = Me, n-Bu, n-Pent) have been synthesized by reaction of CP₃U(THF) with 1 equivalent of RLi. Exchange of the R alkyl occurs on treatment with alkyllithium reagents or in hydrogenolysis in the presence of a terminal olefin. These reactions presumably involve the Cp₃U and Cp₂UR species which are in equilibrium with the Cp₃URLi complexes.     

Crystal and Molecular Structure of BiCl3(15-Crown-5)

Single crystals of complex BiCl3(15-crown-5) were synthesized by gel method, and the structure was solved from X-ray diffraction data by direct and Fourier methods. The crystal is orthorhombic, space group is P212121 with unit cell parameters:a = 7. 677(4), 6=13. 254(6) and c= 15. 911(6) A , and 2=4. The final structural refinement converged with unweighted and weighted factors of 0. 053 and 0. 063 respectively for 1290 observed reflections. The structure consists of discrete BiCl3(15-crown-5) molecules in which bismuth atom is sandwiched between two essentially parallel planes, one of which contains five oxygen atoms and the other contains three chlorine atoms.     

Insertions of nitriles and pyridine into the ZrSi bond of (η5-C5H5)(η5-C5Me5)Zr[Si(SiMe3)3]Me

The zirconium silyl complex CpCpZr[Si(SiMe₃)₃]Me (1; Cp = η⁵-C₅H₅; Cp = η⁵-C₅Me₅) reacts with nitriles RCN (R = Me, CHCH₂, Ph) to form the azomethine derivatives CpCpZr[NC(R)Si(SiMe₃)₃]Me (2, R = Me; 3, R = CHCH₂; 4, R = Ph). Pyridine reacts with 1 to give a 75% yield of CpCpZr[NC₅H₅Si(SiMe₃)₃]Me (5), which results from 1,2-addition of the ZrSi bond of 1 to pyridine. These reactions provide the first examples of nitrile and pyridine insertions into a transition metal-silicon bond. The related silyl complexes Cp₂Zr[Si(SiMe₃)₃]Me and CpCpZr[Si(SiMe₃)₃]Cl are much less reactive toward nitriles and pyridine.     

Crystal structure of twinned (η5-C5(CH3)4CF3) (η5-C5(CH3)5)Ru

The substituted sandwich complex crystallizes in monoclinic space groupP2₁/m withZ=2. Twinning to the (001) direction with the special conditionc ^*/4a ^* = cos ^* causes systematic superposition of the reciprocal lattices of both domains and results in an apparent unit cell with double volume and the reflection condition (2h)kl, l=2n. The structure solution was obtained with the subset of intensity data for the predominant individuum and converged atR = 0.040,R _w =0.046 for 832 independent observations and 122 variables. The molecules show disorder with respect to the crystallographic mirror plane. The structure is closely related to that of decamethylruthenocene.     

2-Polyfluoroalkylchromones. 11. Synthesis and structures of 5-hydroxy-3-(2-hydroxyaryl)-5-polyfluoroalkyl-Δ2-pyrazolines and 3(5)-(2-hydroxyaryl)-5(3)-polyfluoroalkylpyrazoles

The reaction of 2-hydroxy-2-polyfluoroalkylchroman-4-ones with hydrazine affords 5-hydroxy-3-(2-hydroxyaryl)-5-polyfluoroalkyl-²-pyrazolines, whereas 2-polyfluoroalkylchromones under similar conditions produce 3(5)-(2-hydroxyaryl)-5(3)-polyfluoroalkylpyrazoles. 5-(2-Hydroxyaryl)-1-methyl-3-polyfluoroalkylpyrazoles were synthesized in the reaction with methylhydrazine, and the reaction with phenylhydrazine afforded regioisomeric 3(5)-(2-hydroxyphenyl)-1-phenyl-5(3)-polyfluoroalkylpyrazoles.     

Substitution and insertion reactions of (η5-C5H5)Cr(CO)3C2H5

The complex (η⁵-C₅H₅)Cr(CO)₃Cp42 H₅ has been made and its reactions with σ donor ligands L (L = (MeO)₃P and (EtO)₃P) and with SO₂ studied. The alkyl phosphites give compounds of the composition (η⁵-C₅H₅)Cr(CO)₂LC₂H₅, and sulfur dioxide gives the corresponding S-sulfinato (η⁵-C₅H₅)Cr(CO)₃SO₂C₂H₅.     

Synthesis and applications of (5-substituted benzimidazolo)-benzo-15-crown-5 and 4,4′-bis-benzimidazolo-dibenzo-15-crown-5 for the colorimetric detection of Au3+

In the present work, we have reported the synthesis of benzimidazoles functionalized crown ether derivatives of 4-formyl benzo-15-crown-5/4,4′-diformyl dibenzo-15-crown-5 and substituted diamine pyridine using sulfamic acid as a catalyst in DMSO. These molecules are used for the colorimetric determination of Au³⁺ selectively among other metal cations such as Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Hg²⁺, Au³⁺ and Ag⁺ ions_.     

Heats of reaction of HMo(CO)3C5H5 with CCl4 and CBr4 and of NaMo(CO)3C5H5 with I2 and CH3. Solution thermochemical study of the MoX bond for X = H,Cl, Br,I and CH3

The heats of reaction of HMo(CO)₃C₅H₅ with CX₄ (X = Cl, Br) producing XMo(CO)₃C₅H₅ have been measured by solution calorimetry and are −31.8±0.9 and −34.4±2.0 kcal/mole, respectively. The heats of reaction of NaMo(CO)₃C₅H₅ with I₂ and CH₃I producing IMo(CO)₃C₅H₅ and H₃CMo(CO)₃C₅H₅ are −32.3± 1.3 and −7.7± 0.3 kcal/mole. Oxidation with Br₂CCl₄ yielding Br₃Mo(CO)₂C₅H₅ was measured for the following complexes: (C₅H₅(CO)₃Mo)₂, (−92.0±1.0 kcal/mole), BrMo(CO)₃C₅H₅ (−24.9± 2.0 kcal/mole) and HMo(CO)₃C₅H₅ (−60.7± 2.0 kcal/mole). These and other data are used to calculate the Mo–X bond strength for X = H, Cl, Br, I, and CH₃. These bond strength estimates are compared to those reported for X₂Mo(C₅H₅)₂. Iodination of H₃CMo(CO)₃C₅H₅, reported in the literature to yield CH₃I and IMo(CO)₃C₅H₅, actually produces CH₃C(O)I and I₃Mo(CO)₂C₅H₅.     

The Arachno-Zintl Ion (Sn5Sb3)3− and the Effects of Element Composition on the Structures of Isoelectronic Clusters: Another Facet of the Pseudo-Element Concept

The pseudo-element concept, in its most general formulation, states that isoelectronic atoms form equal numbers of bonds. Hence, clusters such as Zintl ions usually retain their structure upon isoelectronic replacement of some or all atoms. Here, a deviation from this common observation is presented, namely the formation of (Sn₅Sb₃)³⁻ ( 1 ), a rare example of an eight-vertex Zintl ion, and an unprecedented example of a Zintl ion synthesized by solution means that has an arachno-type structure according to the Wade–Mingos rules. Three structure-types of interest for (Sn₅Sb₃)³⁻ were identified by DFT calculations: one that matched the X-ray diffraction data, and two that that were reminiscent of fragments of known clusters. A study on the isoelectronic series of clusters, (Sn_xSb_8−x)^2−x (x=0–8), showed that the relative energies of these three isomers vary significantly with composition (independent of electron count) and that each is the global minimum at least once within the series.     

Synthesis of (3S,5R)-cis- and (3S,5S)-trans-3,5-Dimethylvalerolactones and Their Conversion to Biotransformation Products of (S)-5-Ethyl-5-(2′-pentyl)barbituric Acid

(R,S)-5-Ethyl-5-(2′-pentyl)barbituric acid (I)^1,2 is metabolized in vivo to give all four possible optical isomers of 5-ethyl-5-(3′-hydroxy-1′-methylbutyl)barbituric acid (II). ^3,4 From metabolism studies of pure (1′S)- I and (1′3)-I, Palmer and co-workers^4,5 were able to determine the relative amounts of each of the four isomers formed. These studies showed that (1′S)-I gave mainly one enantiomer of (1′S)-II, whereas (1′R)-I gave approximately equal amounts of both (1′R)-II enantiomers.     

Spectrophotometric study of the complexation equilibria of cobalt(II) with 4-(5′-methyl-3′-isoxazolylazo)-resorcinol and determination of cobalt(II)

The reaction of cobalt(II) with 4-(5′-methyl-3′-isoxazolylazo)-resorcinol (MIAR) in 4% v/v ethanol-water medium at I = 0.1 M (NaClO₄) was investigated spectrophotometrically. Graphical and numerical calculation methods were used to establish the equilibria in solution and to evaluate the stability constant of the complexes formed (log β₁₀₁ = 7.48±0.06, log β₁₁₁ = 12.77 max 12.99, log β₁₀₂ = 16.41±0.07). The optimum conditions for the spectrophotometric determination of Co(II) with MIAR were established and the method applied to its determination in some low alloy steels and hydrofining catalysts.     

Modification of the electronic properties of zigzag (n = 5–10) and armchair (n = 3, 5) carbon nanotubes by K atom adsorption

The adsorption of the potassium atom onto the surface of (n,0) zigzag nanotube (n = 5–10) and (n,n) armchair nanotubes (n = 3, 5) has been studied by density functional theory. The local density approximation calculation of adsorption energy (E _ads) emphasized on the dependency of E _ads to the diameter and chirality of the nanotube. E _ads decreases when the diameter increases. So the (5,0)-K system has the highest adsorption energy among all structures. Furthermore, a significant change was observed in the electronic properties of potassium-adsorbed single-walled carbon nanotube (SWCNT) and the metallic behavior of the nanotube improved. Therefore, our results showed that such modified SWCNTs can be applied in nanodevices such as transistors.     

Kinetics and mechanism of the anation of (αβ)-hydroxo(tetraethylenepentamine)cobalt(III) by thiosulfate, the base hydrolysis of the (sulfur-bonded) thiosulfato(tetraethylenepentamine)-cobalt(III) and photochemistry of oxygen and sulfur-bonded thiosulfato complexes

Summary The reaction of ()-(tetren)CoOH²⁺ with S₂O ₃ ^2- in the 7.25–8.28 pH range at 20–40 °C yielded S- (yellow) and O- (purple) bonded thiosulfato(tetren)cobalt(III) complexes, the former in larger quantities. The rate determining step is preceded by diffusion-controlled ion-pair [(tetren)CoOH²⁺,S₂O ₃ ^2- ] formation. Replacement of coordinated OH^- by S₂O ₃ ^2- is interpreted in terms of an internal conjugate base mechanism: (tetren)CoOH²⁺ (tetren-H)CoOH ₂ ²⁺ , the reactive amido conjugate base being generated by intramolecular proton transfer from the coordinated NH site.In acid medium the S-bonded (tetren)Co(S₂O₃)⁺ is highly stable to redox decomposition, in contrast to its pentaammine analogue. The complex however, undergoes base hydrolysis yielding the corresponding hydroxo complex. The rate and activation parameters for the base hydrolysis have been reported. Photolysis of O- and S-bonded isomers of [(tetren)CoS₂O₃]⁺ in acidic medium at 254 and 313 nm, respectively, yielded aquation products accompanied by some decomposition of S₂O ₃ ^2- .     

Syntheses and characterizations of 5-nitro-2-(3′,5′-di(trifluoromethyl)phenyl)pyridyl-containing iridium(III) complexes and the two-band white photoluminescence properties in solution

A derivative of 2-phenylpyridine (Hppy), 5-nitro-2-(3′,5′-di(trifluoromethyl)phenyl)pyridine (HL), is prepared. The L-containing cyclometalated iridium(III) complexes with mono- and bidentate ancillary ligands, [Ir(L)₂(PPh₃)Cl] (1) and [Ir(L)₂(pic)] (2, pic = picolinic acid), are synthesized and characterized. The photoluminescence (PL) spectra of 1 and 2 in CH₂Cl₂ solutions show emission maxima at 558 and 560 nm, corresponding to yellow light emission with the Commission Internationale de L’éclairage (CIE) coordinates of (0.45, 0.54) and (0.46, 0.52), respectively. However, the luminescence intensity of 2 with PL quantum yield of 0.71 is obviously stronger that of 1 with PLQY of 0.19. The two-band white PL properties of 2 and [Ir(dfppy)₂(PPh₃)(NCS)] (3, dfppy = 2-(4,6-difluorophenyl)pyridine) with efficient blue light emission are investigated. The CH₂Cl₂ solutions of 2 and 3 in the molar ratio of 1?:?5 show white light emission with the CIE coordinates of (0.33, 0.41).