Bis(dioxaborine) Dyes with Variable π‐Bridges: Towards Two‐Photon Absorbing Fluorophores with Very High Brightness

Abstract

Bis(dioxaborine) dyes of the A-π-A format (A: acceptor, π: conjugated bridge) were prepared and photophysically characterized. The best performing dyes feature (a) visible-light absorption (>400 nm), (b) high molar absorption coefficients (up to 70000 m cm ), (c) Stokes shifts in the range of ca. 2500-5800 cm , and (d) strong fluorescence emission with quantum yields of up to 0.74. This yields very bright-emitting dyes for one-photon excitation. However, the most intriguing feature of the dyes is their strong two-photon absorption. This was achieved by means of increased π-conjugation in the phenylene or phenylene-thiophene bridges through the variation of the conjugation length and rigidity. This provided two-photon absorption cross sections of up to 2800 GM (1 Goeppert-Mayer (GM)=10 cm s photon ). Considering the mentioned high fluorescence quantum yields, exceptionally bright-emitting A-π-A two-photon absorbing dyes with low molecular mass are obtained. Time-dependent density-functional theory calculations corroborated the experimental results.

Visible Light-Driven, Gold(I)-Catalyzed Preparation of Symmetrical (Hetero)biaryls by Homocoupling of Arylazo Sulfones

“…The symmetrical biaryl scaffold is a ubiquitous chemical motive in naturally occurring products 1 as well as artificial bioactive species. 2 In addition, the current growing interest for these biaryls is ascribable to their multifaced applications as (stereogenic) ligands, 3 conducting and electroluminescent materials, 4 and key constituents of molecular switches and devices. 5 Thus, it is not surprising that starting from the early synthetic approaches based on the copper-catalyzed coupling of aryl halides under reductive conditions (the so-called Ullmann reaction), 6 an impressive number of transition metal-catalyzed protocols was developed.…”

Extended Alkenyl and Alkynyl Benzotriazoles with Enhanced Two‐Photon Absorption Properties as a Promising Alternative to Benzothiadiazoles

“…It is known that some TP chromophores undergo a S 2 ←S 0 transition, instead of the classical S 1 ←S 0 transition, joining higher electronic states (Figure a and Figures S4–S14 in the Supporting Information). This behavior is characteristic of quasi‐centrosymmetric quadrupolar molecules …”

“…This behavior is characteristic of quasi-centrosymmetric quadrupolar molecules. [35,42,43] DFT calculations DFT and time-dependent (TD) DFT were performed for all compounds to gain an additional insight into the photophysicso f the investigated dyes. Therefore, the Coulomb-attenuated CAM-B3LYP functional [44] and the 6-31G(d) basis set [45] were employed for the estimation of geometric parameters, and the 6-311 + G(2d,p) basis set was used to determine absorption and emission energies.…”

Two‐Photon‐Induced CO‐Releasing Molecules as Molecular Logic Systems in Solution, Polymers, and Cells

“…Herein, we propose to also analyze 2PA‐induced CO release as a new form of molecular logic gates. The optically activated, cancer‐targeted CORMs presented in this work display excellent properties as molecular logic devices since they can process concomitantly electromagnetic, chemical, and environmental information …”

“…[27] Herein, we propose to also analyze 2PA-induced CO release as an ew form of molecular logic gates.T he optically activated, cancer-targeted CORMs presented in this work display excellent properties as molecular logic devices since they can process concomitantly electromagnetic, chemical, and environmental information. [28][29][30] Herein, photoCORMsc ompounds 1-2 (Scheme1)c ombine a [Mn I (CO) 3 ]C O-rich fragment with ap otentially emissive dipicolylamine-1,8-naphthalimide ligand,w hile 2 also integrates a biotin tether.T he turn-on fluorescent chromophore 1,8-naphthalimide has al arge2 PA cross-section [31][32][33][34] and can be excited between l exc = 600-950 nm. [35][36][37][38] Biotin is required to sustain the natural growth of eukaryotic cells.…”