Twin Jet Deposition Research Articles

Matrix Isolation Studies of Novel Intermediates in the Reaction of Trimethylaluminum with Ozone.

The thermal reaction of ozone with trimethyl aluminum was explored using twin jet, concentric jet, and merged jet deposition into cryogenic matrixes. Infrared spectroscopy and density functional theory calculations were employed to identify and characterize the products formed in each case. Together, these deposition techniques provide information over the essentially full course of the gas-phase reaction. At short times with twin jet deposition, the primary product is the O atom insertion product (CH3)2AlOCH3. With merged jet deposition and longer gas-phase mixing times, the methyl peroxy radical H3COO· was seen in good yield along with final stable products H2CO, H3COH, and C2H6. Production of Al2O3 and its deposition onto the walls of the reaction tube as a powdery film was noted as well. All of these outcomes were combined to propose a reaction mechanism for this system. Of particular note, the observation of H3COO· provides clear evidence for a free radical component to the overall mechanism.

Infrared matrix isolation study of the thermal and photochemical reactions of ozone with trimethylgallium.

The thermal and photochemical reactions of (CH3)3Ga and O3 have been explored using a combination of matrix isolation, infrared spectroscopy, and theoretical calculations. Experimental data using twin jet deposition and theoretical calculations demonstrate the formation of multiple product species after deposition, annealing to 35 K, and UV irradiation of the matrices. The products were identified as (CH3)2GaOCH3, (CH3)2GaCH2OH, (CH3)(CH3O)Ga(OCH3), (CH3)2GaCHO, and (CH3)Ga(OCH3)(CH2OH). Product identifications were confirmed by annealing and irradiation behavior, (18)O substitution experiments, and high level theoretical calculations. Merged jet deposition led to a number of stable late reaction products, including C2H6, CH3OH, and H2CO. A white solid film was also noted on the walls of the merged (flow reactor) region of the deposition system, likely due to the formation of Ga2O3.

Investigation of the mechanism of ozonolysis of (Z)-3-methyl-2-pentene using matrix isolation infrared spectroscopy

The matrix isolation technique, combined with infrared spectroscopy and twin jet codeposition, has been used to characterize intermediates and stable “late” products formed during the ozonolysis of (Z)-3-methyl-2-pentene (MP). While twin jet deposition led to minimal product formation, annealing to 35K produced a number of product bands. Based on isotopic labeling and theoretical calculations, product bands have been assigned to the primary ozonide and also tentatively to the secondary ozonide of MP. Indirect evidence for formation of one or both possible Criegee intermediates in this system is presented. While neither possible Criegee intermediate for this system was observed, the evidence overall clearly supports the mechanism first proposed by Criegee for the ozonolysis of alkenes. UV irradiation led to product arising from O atom addition to MP, while merged jet codeposition led to a number of stable products for this system.

Infrared Matrix Isolation Study of the Thermal and Photochemical Reactions of Ozone with Dimethylcadmium

The matrix isolation technique has been combined with infrared spectroscopy and theoretical calculations to explore the reaction of (CH(3))(2)Cd with O(3) over a range of time scales and upon irradiation. During twin jet deposition, multiple novel product species were observed along with several stable "late" products. Following annealing of these matrices to 35 K, absorptions due to two novel product species increased in intensity. In addition, new bands appeared, indicating the formation of an additional product. Subsequent UV irradiation destroyed several of the initial products and produced a new photoproduct. On the basis of (18)O and (16,18)O spectroscopic data and theoretical calculations, the novel intermediates H(3)COCdCH(3), H(3)CCdCH(2)OH, H(3)COCdOOCH(3), and H(3)CCdCHO were identified. Merged jet deposition led to a number of stable "late" products, including H(2)CO, CH(3)OH, and C(2)H(6), identifications that were confirmed by (18)O substitution. Mechanistic inferences for this reaction are discussed.

Matrix isolation study of the thermal and photochemical reaction of ozone with Trimethyl Indium

The matrix isolation technique has been combined with infrared spectroscopy and theoretical calculations to explore the reaction of (CH 3) 3In with O 3 over a range of time scales. Upon twin jet deposition (short reaction time), formation of the novel H 3COIn(CH 3) 2 species along with a low yield of CH 2O was observed. Subsequent UV irradiation greatly increased the yield of H 3COIn(CH 3) 2 while the intensities of the CH 2O bands were not affected. An extensive set of bands were seen for H 3COIn(CH 3) 2 after irradiation and 18O spectroscopic data was obtained as well. The identification of this species was supported by theoretical calculations at the B3LYP/lanl2dz and B3LYP/dgdzvp levels of theory. Merged jet deposition (longer reaction times) led to high yield of H 2CO, CH 3OH and C 2H 6, identifications that were confirmed by 18O substitution. Mechanistic inferences for the initial steps of this reaction are discussed.

Infrared Matrix Isolation and Theoretical Study of the Initial Intermediates in the Reaction of Ozone with cis-2-Butene

Matrix isolation studies combined with infrared spectroscopy of the twin jet codeposition of ozone and cis-2-butene into argon matrices have led to the first observation of several early intermediates in this ozonolysis reaction. Specifically, evidence is presented for the formation and identification of the long sought-after Criegee intermediate, as well as confirming evidence for earlier reports of the primary and secondary ozonides. These species were observed after initial twin jet deposition, and grew upon annealing to 35 K. Extensive isotopic labeling ((18)O and (16,18)O mixtures) experiments provided important supporting data. Detailed theoretical calculations at the B3LYP/6-311++G(d,2p) level were carried out as well to augment the experimental work. Merged jet (flow reactor) experiments followed by cryogenic trapping in solid argon led to the formation of "late", stable oxidation products. Photochemical reactions of ozone with cis-2-butene was studied as well, as was the photochemical behavior of the primary and secondary ozonides.

Matrix isolation study of the photochemical reaction of cyclohexane, cyclohexene, and cyclopropane with ozone

The matrix isolation technique, combined with infrared spectroscopy, has been used to characterize the products of the photochemical reactions of cyclohexane, cyclohexene, and cyclopropane with ozone. While initial twin jet deposition of the reagents led to no visible changes in the recorded spectra, strong product bands were noted following irradiation with light of λ > 200 nm. Irradiation of matrices containing ozone and cyclohexane led to O atom reactions with insertion into a C H bond and a C C bond to form cyclohexanol and oxacycloheptane, respectively. Irradiation of matrices containing ozone and cyclohexene led to a mixture of products formed through oxidation of the double bond, including cyclohexanone and cyclohexene oxide. Cyclopropane and ozone were codeposited into argon matrices followed by irradiation, leading to the formation of both cyclopropanal through insertion into a C H bond and aldehydes through ring-opening and oxidation. These conclusions were supported by isotopic labeling ( 18O), by comparison to authentic infrared spectra, and by B3LYP/6-311G++(d,2p) density functional calculations.

Matrix Isolation Study of the Early Intermediates in the Ozonolysis of Cyclopentene and Cyclopentadiene: Observation of Two Criegee Intermediates

Matrix isolation studies, combined with infrared spectroscopy, of the twin jet codeposition of ozone into matrices containing either cyclopentadiene or cyclopentene have led to the first observation of several early intermediates in these ozonolysis reactions. Specifically, evidence is presented for the formation, identification, and characterization of the long sought-after Criegee intermediate for each system, as well as the primary and secondary ozonides. These were observed after initial twin jet deposition and grew approximately 300% upon annealing to 35 K. Extensive isotopic labeling ((2)H, (18)O and mixtures) experiments provided important supporting data. Detailed theoretical calculations at the B3LYP/6-311++G(d,2p) and B3LYP/6-311++G(3df, 3pd) levels were carried out as well to augment the experimental work. Merged jet (flow reactor) experiments followed by cryogenic trapping in solid argon led to the formation of "late" stable oxidation products of cyclopentadiene and cyclopentene. In contrast, no thermal reaction between ozone and cyclopentane was observed. Photochemical reactions of ozone with all three organic substrates were studied as well.

Infrared Matrix Isolation Study of the Thermal and Photochemical Reactions of Ozone with Dimethylzinc

The matrix isolation technique has been combined with infrared spectroscopy and theoretical calculations to explore the reaction of (CH3)2Zn with O3 over a range of time scales. Upon twin jet deposition, an initial cage pair complex was observed, along with formation of the novel H3COZnCH3 species. Subsequent UV irradiation destroyed the complex and greatly increased the yield of H3COZnCH3. An extensive set of bands were seen for this molecule, and (18)O spectroscopic data were obtained as well. The identification of this species was supported by theoretical calculations at the B3LYP/6-311++g(d,2p) level. Merged jet deposition led to a very different set of products, including H2CO, CH3OH and C2H6, identifications that were confirmed by (18)O substitution. In addition, a new variable length concentric deposition technique was developed to permit study of the time scales between twin (relatively short) and merged (relatively longer) reaction times. Mechanistic inferences for this reaction are discussed.

Matrix Isolation Studies of Photochemical and Thermal Reactions of 3- and 5-Membered Cyclic Hydrocarbons with CrCl2O2

The matrix isolation technique has been combined with infrared spectroscopy and theoretical calculations to characterize the products of the photochemical and thermal reactions of cyclopentadiene, cyclopentene, cyclopentane, and cyclopropane with CrCl 2O 2. While initial twin jet deposition of the reagents led to no visible changes in the recorded spectra, product bands were observed following irradiation with light of lambda > 300 nm. The irradiation was shown to lead to oxygen atom transfer to the five-membered rings, forming complexes between cyclic alcohol derivatives and CrCl 2O. For the cyclopentadiene and cyclopentene systems, complexes between cyclic ketone derivatives and CrCl 2O were also observed. For cyclopropane, a ring-opening oxidation reaction followed by fragmentation was observed for the first time, forming the H 2COCrCl 2O complex and C 2H 4. In the room temperature thermal (merged jet) reactions between CrCl 2O 2 and cyclopentadiene, cyclopent-3-enone was observed. At the higher temperatures, 150 and 200 degrees C, 1,3-cyclopentanedione was also observed as well. No product bands were detected in the merged jet experiments for the other three systems. These conclusions were supported by isotopic labeling ((2)H) and by B3LYP/6-311G++(d,2p) density functional calculations.

Matrix isolation investigation of the photochemical reaction of activator-substituted benzenes with CrCl 2O 2

The matrix isolation technique, combined with infrared spectroscopy and theoretical calculations, has been used to characterize the products of the photochemical reactions of aniline, anisole, and N, N-dimethylaniline with CrCl 2O 2. While initial twin jet deposition of the reagents did not lead to product formation, new bands were noted following irradiation with light of λ > 300 nm. In the reactions of CrCl 2O 2 and aniline, irradiation led to HCl formation, very likely accompanied by CrClO 2(H)NC 6H 5 formation, and a mixture of isomers of CrCl 2O-aminocyclohexa-2,4-dienone via oxygen atom transfer. CrCl 2O 2 and aniline were also codeposited as cryogenic thin films, producing new bands. Irradiation of these films led to further growth of these bands. The same products were identified in the thin film studies as were observed in the argon matrix experiments. The irradiation of the matrices containing CrCl 2O 2 and anisole and N, N-dimethylaniline were shown to lead to oxygen atom transfer, forming complexes between the corresponding cyclic ketone derivatives and CrCl 2O. The identification of the complexes were supported by density functional calculations at the B3LYP/6-311G++(d,2p) level and isotopic labeling (in the case of aniline).

Matrix isolation and theoretical investigation of the photochemical reaction of CrCl 2O 2 with benzenes substituted with electron withdrawing groups

The matrix isolation technique, combined with infrared spectroscopy and theoretical calculations, has been used to characterize the products of the photochemical reactions of chlorobenzene, α,α,α-trifluorotoluene, benzonitrile, and nitrobenzene with CrCl 2O 2. While initial twin jet deposition of the reagents led to no visible changes in the recorded spectra, product bands were noted following irradiation with light of λ > 300 nm. The irradiation was shown to lead to oxygen atom transfer, forming complexes between the corresponding cyclic ketone derivatives and CrCl 2O. With benzonitrile, cyanophenol complexed to CrCl 2O was also observed. This latter result arises from C–H bond activation and oxygen atom insertion into a C–H bond. The identification of the complexes were further supported by density functional calculations at the B3LYP/6-311G++(d, 2p) level. Product distributions were rationalized by an analysis of the electron density distribution.

Matrix isolation study of the photochemical reaction of cyclohexane and cyclohexene with CrCl 2O 2

The matrix isolation technique, combined with infrared spectroscopy, has been used to characterize the products of the photochemical reactions of cyclohexane and cyclohexene with CrCl 2O 2. While initial twin jet deposition of the reagents led to no visible changes in the recorded spectra, strong product bands were noted following irradiation with light of λ > 300 nm. The irradiation was shown to lead to oxygen atom transfer, forming complexes between cyclic alcohol derivatives and CrCl 2O, although complexes between ring expansion products and CrCl 2O could not be ruled out. This latter result could arise from C–C bond activation and oxygen atom insertion into a C–C bond. For the cyclohexene system, the cyclohexanone–CrCl 2O complex was also observed. The identification of the complexes was further supported by isotopic labeling ( 2H) and by density functional calculations at the B3LYP/6-311G++(d,2p) level.

Matrix Isolation Investigation of the Photochemical Reaction of Methyl-Substituted Benzenes with CrCl2O2

The matrix isolation technique, combined with infrared spectroscopy, has been used to characterize the products of the photochemical reactions of toluene, m-, o-, and p-xylene, mesitylene, and hexamethylbenzene with CrCl2O2. While initial twin jet deposition of the reagents led to no visible changes in the recorded spectra, strong product bands were noted following irradiation with light of lambda > 300 nm. The irradiation was shown to lead to oxygen atom transfer, forming complexes between methylcyclohexadienone derivatives and CrCl2O. With the xylenes and mesitylene, di- and trimethylphenols, complexed to CrCl2O, were also observed, respectively. This latter result arises from C-H bond activation and oxygen atom insertion into a C-H bond. The identification of the complexes was further supported by isotopic labeling (2H) and by density functional calculations at the B3LYP/6-311G++(d,2p) level. Product distributions were rationalized by an analysis of the electron density distribution.

Electronic spectra of intermediate charge transfer complexes of CrO 2Cl 2 in argon matrices

The matrix isolation technique has been combined with UV/Visible spectroscopy to characterize electronic transitions in 1:1 complexes of CrO 2Cl 2 with a series of lone pair electron donors. Following twin jet deposition with NH 3, (CH 3) 2O and (CH 3) 2CO, new absorptions were observed near bands of parent CrO 2Cl 2. These are assigned to intramolecular electronic absorptions of the CrCl 2O 2 chromophore. Weak, diffuse absorptions were observed with PH 3, indicative of a very weak interaction in the 1:1 complex. The reaction between OVCl 3 and NH 3 was also investigated, and resulted in unstructured absorptions at 582 and 473 nm. These have been assigned to LMCT transitions. Theoretical DFT calculations support the identification of these molecular complexes.

Matrix Isolation Investigation of the Photochemical Reaction of Benzene with CrCl2O2 and OVCl3

The matrix isolation technique, combined with infrared spectroscopy, has been used to characterize the products of the photochemical reactions of benzene with CrCl(2)O(2) and OVCl(3). While initial twin jet deposition of the reagents led to no visible changes in the recorded spectra, strong product bands were noted following irradiation with light of lambda > 300 nm. Wavelength dependence studies determined that light of lambda < 590 nm led to reaction and oxygen atom transfer, forming an eta(1)-complex between 2,4-cyclohexadienone and CrCl(2)O. The identification of the complex was further supported by isotopic labeling ((13)C and (2)H) and by density functional calculations at the B3LYP/6-311G++(d,2p) level. Merged-jet experiments in which thermal reactions are examined were also conducted, at temperatures as high as 150 degrees C. No products were observed.

Argon matrix isolation study of the interaction of VCl 4 with (CH 3) 2CO

The matrix isolation technique, combined with infrared spectroscopy and theoretical calculations, has been employed to explore the reaction chemistry of the VCl 4/(CH 3) 2CO system. Initial twin jet deposition led to formation of an isolated 1:1 complex between the subunits. This complex was characterized by strongly shifted C O and V–Cl stretching modes, as well as by lesser perturbations to additional modes of acetone. Theoretical calculations determined a binding energy for the complex of Δ E 0 298=−4.3 kcal/mol at the UB3LYP/6-31++G(d,2p) level of theory. Calculated infrared spectra, including deuterium shifts, were overall in good agreement with the experimental spectra. Bands due to the complex grew upon annealing, as well as upon irradiation prior to annealing. Matrices irradiated after annealing showed no change. This result differs markedly from the chemistry of the OVCl 3/(CH 3) 2CO system, and demonstrates the role of the oxo group in the reaction chemistry.

Matrix-Isolation Infrared and Theoretical Study of the Reaction of VCl4 with CH3OH

The matrix isolation technique, combined with infrared spectroscopy and theoretical calculations, has been used to investigate VCl4, as well as its reactions with CH3OH and its isotopomers. The infrared spectrum of VCl4 in solid argon showed an intense doublet at 474 and 501 cm-1, which is indicative of a splitting of the triply degenerate stretching mode in Td symmetry due to Jahn−Teller distortion. Density functional theory (DFT) calculations (UB3LYP/6-311++g(d,2p)) reproduced this splitting very well. The calculated structure had four equal V−Cl bonds, but with two Cl−V−Cl angles equal to 110.8° and two angles equal to 106.9°. Using twin-jet deposition, the initial intermediate in the reaction of VCl4 with CH3OH was identified as a 1:1 molecular complex, characterized by perturbations to the V−Cl, C−O, and O−H stretching modes. This complex was destroyed by near-UV irradiation, producing the novel Cl3VOCH3 species and cage-paired HCl. Merged-jet co-deposition of CH3OH and VCl4, with a room-temperature reaction zone, led to almost-complete conversion to Cl3VOCH3. This species was identified by use of isotopic labeling, the observation of HCl as an additional reaction product, and by comparison to DFT calculations. In addition, a large yield of CH3Cl was observed.

Matrix isolation study of the thermal and photochemical reaction of OVCl 3 and CrCl 2O 2 with cycloalkylamines

The matrix isolation technique has been combined with infrared spectroscopy and theoretical calculations to identify and characterize the initial and secondary products in the thermal and photochemical reactions of OVCl 3 and CrCl 2O 2 with cyclopropyl-, cyclobutyl- and cyclopentylamine. Initial twin jet deposition led to the formation of two new species, the 1:1 molecular complex and the secondary HCl elimination product (e.g. Cl 2V(O)N(H)C 3H 5), as well as free HCl. Overall, the yield decreased with the size of the cycloalkyl ring, to the point with cyclopentylamine, the yield was extremely low and no firm conclusions could be reached. The complexes appear to be moderately strongly bound, leading to shifts to certain vibrational modes of both the acid and base subunits. Bands due to the complexes were destroyed by near-UV irradiation (λ>300 nm), and led an increase in the intensity of the bands due to the HCl elimination product, as well as cage-paired HCl. Theoretical calculations were used to aid in product identification and band assignments.

Infrared Matrix Isolation and Theoretical Study of the Reactions of MoCl4O and MoCl2O2 with CH3OH: Characterization of Cl3Mo(O)OCH3

The matrix isolation technique has been employed to investigate the reactions of Cl4MoO and MoCl2O2 with CH3OH and C2H5OH. Using twin jet deposition, the initial intermediate in the mechanism was identified as a weakly bound molecular complex, characterized by perturbations to the MoO and O−H stretching modes. The complex between Cl4MoO and CH3OH was destroyed by near-UV irradiation, producing the novel Cl3Mo(O)OCH3 species and cage-paired HCl. The complex between CH3OH and MoCl2O2 was not photosensitive. Merged jet deposition of CH3OH and Cl4MoO, with a 70 °C reaction zone, led to complete conversion to Cl3Mo(O)OCH3, the same product observed in after irradiation of the 1:1 complex. This species was identified by use of extensive isotopic labeling, by the observation of HCl (or DCl) as an additional reaction product, and by comparison to density functional calculations. Most of the fundamental vibrational modes of this species that lie above 400 cm-1 were observed, some with very high intensities. C2H5OH...