Analysis of problematic complexing behavior of ferric chloride with N,N-dimethylformamide using combined techniques of FT-IR,XPS, and TGA/DTG

A problematic coordination behavior of highly hygroscopic FeCl(3) in DMF solution was studied. From the compositional and structural analyses for the adduct of FeCl(3)/DMF using various techniques such as FTIR, elemental analysis, UV/vis, XPS, and TGA/DTG, it was found that the iron cation exists in the form of an Fe(3+) cation and coordinates via the carbonyl oxygen atom of amide bond in DMF. The analyses of both FT-IR and XPS C 1s spectra for the adduct revealed that 2.1 molecules of DMF coordinate with a more electron-deficient Fe(3+); otherwise 1.2 molecules of DMF coordinated with a relatively electron-rich Fe(3+). The Cl 2p spectrum indicated that the electron-deficient Fe(3+) coordinated with two chlorine ions and the electron-rich Fe(3+) with four chlorines so that the chemical formula of the adduct is of [FeCl(2)(DMF)(1.2)(H(2)O)(2.7)](+)[FeCl(4)(DMF)(2.1)](-). The water molecules in the adduct were found chemisorbed rather than physisorbed, with a singular binding energy.     

Evaluation of the impacts of gamma radiolysis on an ALSEP process solvent

Journal of Radioanalytical and Nuclear Chemistry - Separating the minor actinide elements (americium and curium) from the fission product lanthanides is an important step in closing the nuclear...     

A Study on the Ring Transformation of Dihydroisoxazolopyrimidine

Dihydroisoxazolopyrimidine derivatives could be cleaved to form either pyrimidine ring or isoxazole ring derivatives depending upon the reaction conditions employed.     

Regioselectivity and Stereoselectivity in the Intramolecular Nitrile Oxide-Olefin Cycloaddition (INOC) Reaction and the Intramolecular Silyl Nitronate-Olefin Cycloaddition (ISOC) Reaction

Both INOC and ISOC reactions of 1 which has two different double bonds in a molecule (allylic and homoallylic double bond) showed high regioselectivity for allylic double bond to make [5,5] ring system. INOC reactions of 1 and 6 showed high diastereoselectivity for 4-substituents, whereas ISOC reaction did for 6-substituents of tetrahydrofuroisoxazolines.     

Sigma/pi Bonding Preferences of Solvated Alkali-Metal Cations to Ditopic Arylmethyl Anions

Arylmethyl anions allow alkali-metals to bind in a σ-fashion to the lateral carbanionic centre or a π-fashion to the aryl ring or in between these extremities, with the trend towards π bonding increasing on descending group 1. Here we review known alkali metal structures of diphenylmethane, fluorene, 2-benzylpyridine and 4-benzylpyridine. Next, we synthesise Li, Na, K monomers of these diarylmethyls using polydentate donors PMDETA or Me₆TREN to remove competing oligomerizing interactions, studying the effect that two aromatic rings has on negative charge (de)localisation via NMR, X-ray crystallographic and DFT studies. Diphenylmethyl and fluorenyl anions maintain C(H)−M interactions regardless of alkali-metal, although the adjacent arene carbons engage in interactions with larger alkali-metals. Introducing a nitrogen atom into the ring (at the 2- or 4-position) encourages relocalisation of negative charge away from the deprotonated carbon and onto nitrogen. Phenyl(2-pyridyl)methyl moves from an enamide formation at one extremity (lithium) to an aza-allyl formation at the other extremity (potassium), while C- or N-coordination modes become energetically viable for Na and K phenyl(4-pyridyl)methyl complexes.     

Metal ion sensing novel calix[4]crown fluoroionophore with a two-photon absorption property

1,3-Alternate calix[4]arene-based fluorescent chemosensors bearing two-photon absorbing chromophores have been synthesized, and their sensing behaviors toward metal ions were investigated via absorption band shifts as well as one- and two-photon fluorescence changes. Free ligands absorb the light at 461 nm and weakly emit their fluorescence at 600 nm when excited by UV-vis radiation at 461 nm, but no two-photon excited fluorescence is emitted by excitation at 780 nm. Addition of an Al(3+) or Pb(2+) ion to a solution of the ligand causes a blue-shifted absorption and enhanced fluorescence due to a declined resonance energy transfer (RET) upon excitation by one- and two-photon processes. Addition of a Pb(2+) ion to a solution of 1.K(+) results in a higher fluorescence intensity than the original 1.Pb(2+) complex regardless of one- or two-photon excitation, due to the allosteric effect induced by the complexation of K(+) with a crown loop.     

Mixed-metal cluster chemistry. 29. Core expansion and ligand-driven metal exchange at group 6-iridium clusters

Reactions of the tetrahedral clusters MoIr3(mu-CO)3(CO)8(eta-L) (L = C5HMe4, C5Me5) with the carbonylmetalate anions [Mo(CO)3(eta-L)]- afford the trigonal bipyramidal clusters Mo2Ir3(mu3-H)(mu-CO)2(CO)9(eta-L)2 (L = C5HMe4 (3c), 74%; L = C5Me5 (3d), 55%) in which the group 6 metal atoms occupy the apexes; reaction of the cyclopentadienylmolybdenum-containing analogues or their cyclopentadienyltungsten-containing homologues failed to afford analogous products. Reactions of MIr3(mu-CO)3(CO)8(eta-C5H5) (M = Mo, W) with [M(CO)3(eta-L)]- (L = C5HMe4, C5Me5) afford the core-expanded heteroapex clusters M2Ir3(mu3-H)(mu-CO)2(CO)9(eta-C5H5)(eta-L) (M = Mo, L = C5HMe4 (5c), 9%, L = C5Me5 (5d), 4%; M = W, L = C5Me5 (6d), 5%) in low yield, together with the homoapex clusters M2Ir3(mu3-H)(mu-CO)2(CO)9(eta-L)2 (M = Mo, L = C5HMe4 (3c), 81%, L = C5Me5 (3d), 60%; M = W, L = C5Me5 (4d), 5%) in much higher yield for the Mo-containing examples. The identities of clusters 3c,d, 4d, and 5c,d have been confirmed by single-crystal X-ray diffraction studies, with the same disposition of ligands about the trigonal bipyramidal cluster cores being observed in each case, a ligand arrangement that has been examined by complementary density functional theory studies. While cluster 5d is accessible as above, no reaction is observed from MoIr3(mu-CO)3(CO)8(eta-C5Me5) and [M(CO)3(eta-C5H5)]-. Treating MoIr3(mu-CO)3(CO)8(eta-C5H5) with 1 equiv of [M(CO)3(eta-C5Me5)]- affords 5d as the major product, a further 1 equiv affording some MoIr3(mu-CO)3(CO)8(eta-C5Me5) and a third 1 equiv giving a good yield of 3d. This is consistent with reaction proceeding by apex fragment addition, followed by apex fragment elimination, and finally a further apex fragment addition, the homometallic incoming apexes being distinguished from the departing vertices by their highly methylated cyclopentadienyl ligands. Spectroscopic data suggest that the electron density at these disparate-metal-containing cluster cores is tunable by progressive (conceptual) cyclopentadienyl alkylation.     

Probabilistic Extensions of the Erdős–Ko–Rado Property

The classical Erdős–Ko–Rado (EKR) Theorem states that if we choose a family of subsets, each of size k, from a fixed set of size , then the largest possible pairwise intersecting family has size . We consider the probability that a randomly selected family of size t=t _n has the EKR property (pairwise nonempty intersection) as n and k=k _n tend to infinity, the latter at a specific rate. As t gets large, the EKR property is less likely to occur, while as t gets smaller, the EKR property is satisfied with high probability. We derive the threshold value for t using Janson’s inequality. Using the Stein–Chen method we show that the distribution of X ₀, defined as the number of disjoint pairs of subsets in our family, can be approximated by a Poisson distribution. We extend our results to yield similar conclusions for X _i , the number of pairs of subsets that overlap in exactly i elements. Finally, we show that the joint distribution (X ₀, X ₁, ..., X _b ) can be approximated by a multidimensional Poisson vector with independent components.      

Determination of temperatures within acoustically generated bubbles in aqueous solutions at different ultrasound frequencies

Mean acoustic bubble temperatures have been measured using a methyl radical recombination (MRR) method, at three ultrasound frequencies (20, 355, and 1056 kHz) in aqueous tert-butyl alcohol solutions (0-0.5 M). The method is based on yield measurements of some of the hydrocarbon products formed from the recombination of methyl radicals that are thermally generated within collapsing bubbles containing tert-butyl alcohol vapor. The mean bubble temperatures were found to decrease substantially with increasing tert-butyl alcohol concentration at 355 and 1056 kHz but only to a small extent at 20 kHz. Extrapolating the mean temperatures measured to zero concentration of tert-butyl alcohol, at a bulk solution temperature of 20 degrees C, gave the order 355 kHz (4300 +/- 200 K) > 1056 kHz (3700 +/- 200 K) > 20 kHz (3400 +/- 200 K). It is also concluded that the temperature derived from the MRR method is a useful diagnostic parameter for sensing the thermal conditions within an active acoustic bubble. However, attention must be given to the fact that the temperature derived from the MRR method is not theoretically well defined.