Photodissociation at 193 nm of tert-Butyl Nitrite on Ag(111)

Abstract

The translational and internal state properties of nitric oxide, NO, ejected by 193-nm photodissociation of tert-butyl nitrite, (CH 3 ) 3 CONO, TBN, adsorbed on Ag(111) have been investigated using resonance-enhanced multiphoton ionization time-of-flight (REMPI-TOF) and quadrupole mass spectrometer time-of-flight (QMS-TOF). The results are described in terms of three components depending on the number of collisions along the exit trajectory and are compared to prior work using 248-and 351-nm photons. Although 193-nm photons have higher energy, the characteristic translational energy of the collisionless NO (0.55 eV) lies between that for 248 nm (0.89 eV) and 351 nm (0.39 eV). As for gas-phase photolysis at 193 nm, the NO is rotationally cold (J max ) 15.5), much lower than for both 248-(J max ) 53.5) and 351-nm (J max ) 31.5) photolysis. The NO vibrational distribution is dominated by V′′ ) 1, whereas V′′ ) 0 for 248 nm and V′′ ) 1 and 2 for 351 nm photodissociations, respectively. Angle-resolved REMPI-TOF and QMS-TOF studies give information about the orientation of adsorbed TBN. While TBN is more stable with the C-O-NdO plane perpendicular to surface and the internal O-N bond directed about 40°away from the surface normal, dosing less than a full monolayer at 80 K does not achieve this state fully. Annealing to 110 K is sufficient to realize this molecular orientation. For multilayer coverage dosed at 80 K, the data are consistent with considerable surface roughness compared to a surface annealed at 110 K. IntroductionSurface photochemistry has been of interest for many years. 1-3 Among the motivations are its many potential technological applications, e.g., photochemical lithography, deposition, and etching related to the fabrication of electronic and chemical sensor devices with submicron dimensions. There also continues to be scientific interest in fundamental questions concerning the mechanisms of energy transfer among the radiation field, and the various electronic and nuclear degrees of freedom of adsorbate-substrate systems.The spectroscopy and photodissociation dynamics of aliphatic nitrites (R-O-NdO) have been the subject of much interest. [4][5][6][7][8][9] Typically, gas phase and adsorbed nitrites dissociate upon photolysis and do so through cleavage of the internal O-N bond to from an alkoxide and nitric oxide. Like other nitrites, tertbutyl nitrite (TBN, (CH 3 ) 3 CONO) has three distinct optical absorption bands, the lowest energy band is found between 300 and 400 nm (n f π*, S 1 r S 0 ), and motion on S 1 is characterized as vibrational predissociation. The second band ranges from about 216 to 280 nm (π f π*, S 2 r S 0 ), and motion on S 2 is described as a very fast repulsive dissociation. The third band, rarely studied and related to this paper, ranges from 180 to 216 nm and also leads to dissociation of the internal O-N bond. State-resolved studies of NO reveal very different quantum state distributions depending on the photolysis wavelength. For gas-phase irradiation, photodissociation at 35...

New trans dichloro (triphenylphosphine)platinum(II) complexes containing N -(butyl), N -(arylmethyl)amino ligands: Synthesis, cytotoxicity and mechanism of action

“…3A), as previously reported by some authors. 18 Otherwise, complex 2a induces a notable increase in subG 0 population (Fig. 3B).…”

“…Most anticancer drugs block the cell cycle in either the S or G 2 /M phase and also cisplatin inhibits cancer cell growth by arresting the cell cycle progression through these phases. 17,18 In order to compare the effect of 2a with that of cisplatin, flow cytometric analysis was performed on A2780 cells, stained with PI and analyzed for DNA/cell content. The cells were incubated in the absence (control) or in the presence of different concentrations (from 1 to 15 lM) of cisplatin or 2a, and the results are shown in Figure 3A and B, respectively.…”