Low Temperature Photoreactivity of Diacetylene – Phenazine Complex Crystals

Abstract

Absorptionsspektren, sichtbar und ultraviolett / Diradikale / Elektronenspinresonanz / FestkBrperpolymerisation / PhotochemieThe low temperature photoreactivity of diacetylene-phenazine complex crystals has been studied by ESR-and optical spectroscopy. The optical excitation of phenazine at 4.2 K creates a stable, triplet diradical. It is caused by an electron-transfer reaction from the diacetylene to the phenazine and a protonation of the phenazine. The diradical can be bleached optically at 4.2 K and thermally at temperatures above 90 K. The diacetylene units polymerize in the dark, as soon as the preirradiated crystals are warmed up to temperatures above 200 K. The solid-state photochemistry of phenazine at low temperatures and its relation to the sensitized photopolymerization are discussed.

Topochemical Polymerization: Diynes

“…153,154 These conflicting results have been resolved by a series of detailed measurements of the intermediates produced by UV irradiation of bis(toluenesulfonate) diyne (TS) monomer crystals at low temperature. On energetic and mechanistic grounds a dimer diradical with a butatriene structure is the most likely first reaction product.…”