Strong Two‐Photon Absorption of Singlet Diradical Hydrocarbons

Abstract

Ones and twos: The two‐photon absorption cross sections (σ(2)) of singlet diradical hydrocarbons with phenalenyl peripheral groups (see scheme) are larger than those of closed‐shell aromatic hydrocarbons by an order of magnitude or more and are comparable to those of π‐conjugated compounds with strong electron donor or acceptor substituents. A significant increase in cross section was also observed in the resonance‐enhanced region.

Recent Progress in Quinoidal Singlet Biradical Molecules

“…96,97 Indeed, large TPA cross sections (· (2) ) were observed for singlet biradical compounds. 98 The application to such a novel optical property would be one of next challenges of singlet biradical studies. At the same time, it is quite certain that many fundamental issues remain to be answered.…”

Two‐Photon Absorption‐Related Properties of Functionalized BODIPY Dyes in the Infrared Range up to Telecommunication Wavelengths

“…Maximal TPA cross-section of ca. 1500 GM at 1.44 mm and 1600 GM at 1.3 mm have been reported for dipolar and quadrupolar squarine-type chromophores, respectively, [11,12] whereas nickel (bisdithiolene) complexes [13] and singlet diradical systems [14] exhibit significant s 2 over the entire telecommunication range. On the other hand, numerous fused-, extended-, or organizedporphyrin complexes have been reported with very large TPA crosssections ranging from 10 3 to 10 4 GM.…”

Perylene Bisimide Radicals and Biradicals: Synthesis and Molecular Properties

“…[18] Therefore,w e conjecture that 2CC exists as its open-shell singlet biradical form OS-2CC,w hich is due to the higher number of aromatic sextet rings (Scheme 1). Although 1C and OS-2CC slowly decompose with time,asevidenced by the gradual changes in their timedependent UV/Vis/NIR absorption spectra (Supporting Information, Figure S1) 4 ]s olutions,t he broad CT bands at around 1200 nm decrease gradually with the rise of new bands in the visible region, which are accompanied by drastic color changes for both compounds ( Figure 1; Supporting Information, Figure S2, Tables S2, S3). …”

“…Theintermediate occurrence of an additional NIR absorption at 1396 nm after adding one equivalent [Pb(OAc) 4 …”