Time‐resolved resonance Raman study of S₁cis‐stilbene and its deuterated isotopomers

Abstract

We present the picosecond time-resolved resonance Raman (ps-TR 3 ) spectra of the first excited singlet state (S 1 ) of cis-stilbene (d 0 /, fully deuterated cis-stilbene (d 12 ) and a,a -d 2 -cis-stilbene (d 2 ) measured in hexane at pump and probe wavelengths 267 and 630 nm, respectively. The main observation is that in the lower wavenumber region the spectra are dominated by a second-order overtone progression originating from a 229 cm −1 fundamental band for the S 1 d 0 cis-stilbene. The observed low-wavenumber modes of the excited cis-stilbene are substantially more resonantly enhanced than the modes around 1600 cm −1 .

Stabilising fleeting intermediates of stilbene photocyclization with amino-borane functionalisation: the rare isolation of persistent dihydrophenanthrenes and their [1,5] H-shift isomers

“…Of the many well-studied reactivities within this realm of chemistry, 1 the photocyclization of stilbene and its analogues is a prominent one. 2 These reactions proceed via electrocyclic ring-closure of the cis -isomer ( Z ) according to the Woodward–Hoffman rules 3 to give trans -4a,4b-dihydropheanthrene derivatives (4a,4b-DHPs, Scheme 1 ), which are highly unstable and either revert back to their cis -stilbene form or readily oxidize to their respective phenanthrenes. 4 Photochemical cyclization of stilbenes and derivatives is therefore a straightforward strategy for preparing highly diverse phenanthrenes.…”

Synthesis and optical properties of a poly(2′,5′-dioctyloxy-4,4′,4″- terphenylenevinylene) with high content of (Z) vinylene units

“…The presence of well-defined vibronic structure in luminescence spectra can be explained by considering that, upon relaxation, the geometry of the excited state is less affected by ring torsion as compared to the ground state. Indeed, the excited state is expected to have more quinoidal character than the ground state [21], with a consequent reduction of inter-ring torsion due to the partial double-bond character of the C-C bonds. In Table 2 the energy differences between the position of the absorption and PL maxima (DE s ) in solution are reported.…”

Making molecular machines work

“…Step order of 1 or 2 ps (ref. 55). Hence the rate of rotation is controlled by the thermally induced relaxation of the unstable to the stable state, which requires bulky groups (for example, the methyl and phenyl rings) to pass each other.…”