Picosecond spectroscopy of 1-phenylazo-2-hydroxynaphthalene

Abstract

Publication costs assisted by Bell LaboratoriesDual-beam picosecond absorption spectroscopy was used to measure the time constant of the trans to cis isomerization of l-phenylazo-2-hydroxynaphthalene as a function of viscosity. We find that the isomerization time constant at 21.5 °C is 14 ± 3 ps in methylcyclohexane (viscosity, = 0.729 cP), 28 ± 5 ps in 5:2 methylcyclohexane-cyclohexanol mixed solvent ( = 2.06 cP), 107 ± 29 ps in 5:9 methylcyclohexane-cyclohexanol mixed solvent ( = 9.63 cP).

Interaction of the excited state intramolecular proton transfer probe 3-hydroxy-2-naphthoic acid with poly N-vinyl-2-pyrrolidone polymer in water: An insight into the water structure in the binding region

“…The l max value found in 400 mM PVP-water mixture indicates that the dielectric constant of the microenvironment of 3HNA is about 21. It is reported that in many organic assemblies, the dielectric constant of confined water is close to that of alcohol (e¼30) [42][43][44]. Thus our results of the micro-polarity of the probe (e ¼21) indicates that water structure where 3HNA gets absorbed is different from that of bulk water and could be speculated as either type I or type II or both types of water as reported by Xu et al [10].…”

Photodissociation UV–Vis Spectra of Cold Protonated Azobenzene and 4-(Dimethylamino)azobenzene and Their Benzenediazonium Cation Fragment

“…2 It is well known 3,4 that transcis isomerizationof AB takes place in the electronic excited statewhen the molecule is excited at 365 nm, whereas the reverse reaction can be thermally activated in the ground state (in the dark, thehalf-life of cis-AB in solution is several hours, at room temperature) or induced photochemicallyby irradiation at 420 nm (lifetime in the ps scale). 5 The photoisomerization mechanism of AB remains a matter of debate despite many years of experimental 6,9 and theoretical 10,13 studies. These results have been interpreted in terms of the contribution of two basic pathways that can in principle take place depending on the excitation scheme used: an inversion mechanism involving an in-plane bending of the azoring bonds and an out-of-plane rotation of the NN double bond.The advantageous photochromic properties of AB and its derivative compounds, as well as the ease of attaining optical controlof the switching process between twophotostable states, motivated researchconcerning the use of these moleculesas molecular devices.…”

“…In the electronic ground state, azobenzene (C 6 H 5 NNC 6 H 5 , hereafter denoted AB) can adopt cis and trans configurations defined by the relative orientation of the two phenyl rings attached to the azo group, the trans isomer being approximately 0.6 eV more stable than the cis one, and the trans → cis isomerization barrier in the gas phase being about 1.1 eV . It is well-known , that trans → cis isomerization of AB takes place in the electronic excited state when the molecule is excited at 365 nm, whereas the reverse reaction can be thermally activated in the ground state (in the dark, the half-life of cis -AB in solution is several hours, at room temperature) or induced photochemically by irradiation at 420 nm (lifetime on the picosecond scale) . The photoisomerization mechanism of AB remains a matter of debate despite many years of experimental − and theoretical − studies.…”

Principle of direct-inscribing diffractive phase elements by linearly polarized light

“…As the trans form is generally more stable [11,12] , the polymer exists as the stable trans-form at room temperature. Azos will thermally reconvert from the cis to trans state, with a timescale ranging from milliseconds to hours, depending on the substitution pattern and local environment [13,14] . Light induces transformation in both directions.…”