Degradation of thin 4,4′-bis(2,2′diphenyl vinyl)-1,1′-biphenyl films by UV light

We studied degradation of 4,4′-bis(2,2′diphenyl vinyl)-1,1′-biphenyl (DPVBi), well know OLED material. Thermally evaporated thin films of DPVBi were irradiated with UV light in ambient, vacuum and under different oxygen pressures. The cause of degradation is reaction between UV excited DPVBi molecules and oxygen, via formation of singlet oxygen or electron transfer from excited DPVBi to molecular oxygen. Reaction rates depend on oxygen concentration and UV light intensity. These reactions lead to formation of oxidized species as evidenced by ASAP and MALDI-TOF mass spectroscopy. Photoluminescence quenching has two parts. One part is reversible and may imply formation of charge transfer complexes and the other is irreversible, caused by formation of oxidized species. IR and absorption spectra are studied by Density Functional Theory and results compared with the experiment.SIXTEENTH ANNUAL CONFERENCE YUCOMAT 2014 Hunguest Hotel Sun Resort Herceg Novi, Montenegro, September 1-5, 201

LASER SPECTROSCOPY OF NiO: ROTATIONAL ANALYSIS OF THE SYSTEM IV IN THE 5170 - 5500 {AA} REGION

$^{1}$ B. Rosen, Nature, Lond., 156, 570 (1945).Author Institution: Quantum Institute and the Department of Chemistry, University of CaliforniaLaser-induced fluorescence of NiO formed by the reaction of sputtered Ni atoms from a hollow cathode source with oxygen or ozone was studied. Some of the bands belonging to the Rosen's System $IV^{1}$ were vibrationally and rotationally analyzed. A new vibrational assignment is proposed. The rotational structure of the strongest band at 5176.5 {\AA} resembles $^{1}\Pi-^{1}\Pi$ or $\Omega^{\prime}=1$ to $\Omega^{\prime \prime}=1$ transition. Interesting features include a rotational perturbation in the excited state and extremely strong $\Omega$-doubling in the lower state. This suggests the presence of nearly degenerate $\Omega=0$ electronic state which could be another component of a $a^{3}\Sigma^{-}$ state in Hund's coupling case c. Preliminary rotational analysis of the 5176.5 {\AA} band gives $r^{\prime} = 1.73$ {\AA} and $r^{\prime \prime}_{v} = 1.62$ {\AA} for the equilibrium distances in the upper and lower electronic states

The acentric nature of trans-stilbazole crystals and the origin of its NLO response

The X-ray crystal structure and the second order nonlinear optical response of trans-stilbazole are discussed. Given that diffraction intensities are completely insensitive to any small distortion from centrosymmetry, stilbazole X-ray diffraction data are better modelled in the centrosymmetric P21/c space group and cannot be used to distinguish between alternative acentric options. However, second harmonic generation, notable in itself, sheds light on the acentric nature of the crystals and allows the most reasonable structural model to be selected. A previously unobserved low energy photoemission, probably due to through-space charge transfers, is also reported

VISIBLE-LASER SPECTROSCOPY OF NbN: NEW ELECTRONIC STATES AND HYPERFINE EFFECTS

$^{1}$ Y. Azuma, J.A. Barry, M.P.J. Lyne. A.J. Merer. J.O. Schrixler and J.L. F\'{e}m\'{e}nias. J. Chem. Phys. 91. 1 (1989).Author Institution: Department of Chemistry, University of British Columbia; Physics Division, Argonne National Laboratory; Department of Chemistry, University of British ColumbiaMeasurements of the hyperfine parameters of four excited electronic states of NbN have been carried out. Including previous work on the $B^{3}- X^{3}\Delta system^{1}$. hyperfine parameters have now been measured for a total of six electronic states, namely $\Delta \pi{^{1,3}},\Phi, \sigma 0a^{1}\Delta$ and $X^{3}\Delta$. It is not simple to interpret these parameters without considering higher order spin-orbit effects. For example, the $\Delta \pi{^{1}}\Pi$ state lies within the spin-orbit structure of the $\delta \pi{^{3}}\Pi$ state in zero order, and so strong is the interaction between them that the energy order of the two lowest spin components of the $^{3}\Pi$ state is reversed. Extensive wavelength-resolved fluorescence studies were needed to understand these interactions. These wavelength-resolved fluorescence studies have also led to the discovery of three new low-lying electronic states, $\delta^{2}{^{3}}\Sigma, \delta^{2}{^{1}}\Gamma$ and $\sigma^{2}{^{1}}\Sigma^{+}$, and to the location of $\sigma\delta{^{1}}\Delta$. Above $19,000 cm^{-1}$ the energy level patterns are severely distorted by the onset of charge transfer transitions: the spectra become very perturbed and complicated in this region. The pattern of states found in NbN is likely to be typical of the early diatomic 4d metal compounds; fairly well-behaved low-lying states can be associated with unpaired electrons in the metal orbitals, but the regularity of the structure will break down totally when a ligand electron is promoted to the metal orbitals

Synthesis of hydroazafullerene C59HN, the parent hydroheterofuIlerene

The electronic and geometric properties of C60 can be perturbed by replacing one or more carbon atoms of the fullerene skeleton with an atom of a different element. Exchange of one carbon atom with nitrogen, a trivalent atom with a lone pair of electrons, produces the azafullerene radical C59N·, which is isoelectronic with the C60 radical anion. The process is slightly similar to doping silicon with phosphorus. We have previously described the synthesis of the azafullerene dimer; here we report the bulk preparation of the simplest azafullerene, C59HN. The electronic, vibrational and 13C NMR spectroscopic features of C59HN are similar to those of the dimer, except for the signature of the sp3 (C-H) carbon. C59HN should open the door to a new chemistry of heterofullerenes.

Synthesis of hydroazafullerene C59HN, the parent hydroheterofullerene

THE electronic and geometric properties of C-60 can be perturbed by replacing one or more carbon atoms of the fullerene skeleton with an atom of a different element. Exchange of one carbon atom with nitrogen, a trivalent atom with a lone pair of electrons, produces the azafullerene radical C59N; which is isoelectronic with the C-60 radical anion. The process is slightly similar to doping silicon with phosphorus(1). We have previously described the synthesis of the azafullerene dimer(2); here we report the bulk preparation of the simplest azafullerene, C59HN. The electronic, vibrational and C-13 NMR spectroscopic features of C59HN are similar to those of the dimer(2), except for the signature of the sp(3) (C-H) carbon. C59HN should open the door to a new chemistry of heterofullerenes