Matrix isolation and theoretical study of the reaction of substituted phosphines with CrCl2O2

The reactions between CrO2Cl2 and a series of substituted phosphines have been investigated using matrix isolation infrared spectroscopy. For all of the phosphines except PF3, twin jet co-deposition of the two reagents into argon matrices at 14 K initially led to the formation of weak bands due to the corresponding phosphine oxide. For all of the phosphines, subsequent irradiation with light of lambda > 300 nm led to the growth of a number of intense new bands that have been assigned to the phosphine oxide complexed to CrCl2O, following an oxygen atom transfer reaction. Gas-phase, merged jet reactions prior to matrix deposition led to a significant yield of the uncomplexed phosphine oxide. Theoretical calculations at the B3LYP/6-311++g(d,2p) level were carried out in support of the experimental work, to support product band assignments and clarify the nature of the molecular complexes.     

The infrared spectra and theoretical calculations of frequencies of fac-tricarbonyl octahedral complexes of manganese(I)

The carbonyl stretching frequencies in the infrared spectra of 38 fac-tricarbonyl octahedral complexes of manganese(I) prepared in this laboratory were determined. These complexes may be grouped into three types: (a) neutral complexes of the structure (CO)(3)Mn(P-P)Z where P-P represents depe, dppe, or dppp, and Z represents various anionic functional groups bonded to the manganese; (b) ionic complexes of the structure [(CO)(3)Mn(P-P)Z](+)BF(4)(-) where Z represents various neutral molecules possessing one phosphorous, nitrogen, or oxygen atom coordinated to the manganese; (c) complexes of the structure (CO)(3)Mn(pn)Z where the chelating pn represents 1,1-diphenylphosphino-2,2-dimethylaminoethane, Ph(2)PCH(2)CH(2)NMe(2). All of these complexes show three carbonyl stretching modes (2A' + A"). The effects on the frequencies of these modes induced by both the various Z groups and the various ligands are discussed. Theoretical calculations (B3LYP/6-31G) with optimization of the full molecule make it possible to distinguish between the three stretching modes and to make unambiguous assignments of appropriate symmetry species to each.     

Magnetic circular dichroism of matrix isolated noble gas monohalides

MCD measurements on XeF, XeCl, XeBr and XeI matrix isolated in Ar at low temperature are reported. Some relationships among the various spectroscopic parameters are established by combining these data existing absorption and ESR measurements.     

Investigation of the thermal and photochemical reactions of ozone with 2,3-dimethyl-2-butene

The matrix isolation technique, combined with infrared spectroscopy and twin jet codeposition, has been used to characterize intermediates formed during the ozonolysis of 2,3-dimethyl-2-butene (DMB). Absorptions of early intermediates in the twin jet experiments grew up to 200% upon annealing to 35 K. A number of these absorptions have been assigned to the elusive Criegee intermediate (CI) and secondary ozonide (SOZ) of DMB, transient species not previously observed for this system. Also observed was the primary ozonide (POZ), in agreement with earlier studies. The wavelength dependence of the photodestruction of these product bands was explored with irradiation from λ ≥ 220 to ≥580 nm. Merged jet (flow reactor) experiments generated "late" stable oxidation products of DMB. A recently developed concentric jet method was also utilized to increase yields and monitor the concentration of intermediates and products formed at different times by varying the length of mixing distance (d = 0 to -11 cm) before reaching the cold cell for spectroscopic detection. Identification of intermediates formed during the ozonolysis of DMB was further supported by (18)O and scrambled (16,18)O isotopic labeling experiments as well as theoretical density functional calculations at the B3LYP/6-311++G(d,2p) level.     

Visible absorption and resonance Raman spectra of alkaline earth metal ozonides in argon and nitrogen matrices at 10 K

Optical and resonance Raman spectra of the reaction products of Mg, Ca, Sr, and Ba with ozone were observed in argon and nitrogen matrices. The visible spectra were characterized by strong, vibronically structured absorptions between 540 and 350 nm, and are assigned to the alkaline earth metal ozonides, $\text{A}{}^{\mathrm{+}}\text{O}{}_3{}^{\mathrm{?}}$. Vibrational analysis yielded ω₁′ and ω₁x₁ values of about 900 and 6 cm^?1, respectively, with only slight variation from metal to metal. Resonance Raman spectra consisted of a strong fundamental near 1020 cm^?1 and two overtones with decreasing intensity. Oxygen-18 substitution confirmed the vibrational assignments, which agree very well with the alkali metal ozonide spectra. These results suggest that the +1 oxidation state plays an important role in the chemistry of the alkaline earth metals under conditions where aggregation does not occur to favor the +2 state. A thorough search was made for absorptions due to the alkaline earth oxide species, but no bands were observed.     

Infrared matrix isolation study of the reaction of CrCl2O2 with (CH3)2O and (CH3)2CO

Matrix isolation has been combined with infrared spectroscopy to study the reaction chemistry of CrCl₂O₂ with (CH₃)₂O and (CH₃)₂CO. Very similar results were obtained with twin jet and room temperature merged jet deposition, indicating that the initial product forms on the surface of the matrix during deposition, not in the deposition lines prior to matrix condensation. The initial product in both systems was identified as the 1:1 complex between the two reagents, with a structure in which the oxygen atom of the base donates electron density to the Cr center. A number of perturbed vibrational modes of both subunits were observed; for the bases, these modes were vibrations involving the oxygen atom. Hg arc irradiation of the CrCl₂O₂·O(CH₃)₂ complex led to growth of a secondary product that is tentatively identified as Cl₂CrO(OCH₃)₂. The CrCl₂O₂·OC(CH₃)₂ complex was not photosensitive, and no rearrangements were observed.     

Molar extinction coefficients of some carbohydrates in aqueous solutions

Molar extinction coefficients of some carbohydrates viz. l-arabinose (C₅H₁₀O₅), d-glucose (C₆H₁₂O₆), d-mannose (C₆H₁₂O₆), d-galactose (C₆H₁₂O₆), d(-) fructose (C₆H₁₂O₆) and maltose (C₁₂H₂₄O₁₂) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by gamma ray transmission method in a narrow beam good geometry set-up. These coefficients have been found to depend upon the photon energy following a 4-parameter polynomial. These extinction coefficients for different sugars having the same molecular formula have same values varying within experimental uncertainty. Within concentration ranges studied, Beer-Lambert law is obeyed very well.     

Translational hull of an inverse semigroup

The theory of ideal extensions of semigroups is dependent upon adequate knowledge of the translational hull. We characterize here certain basic structures in the translational hull, Ω(S), of an arbitrary inverse semigroup S: in particular, the semilattice of idempotents of Ω(S) and the group of units of Ω(S). An isomorphic copy of each of these structures is given in terms of the semilattice of idempotents of S.