Preparation and pH-Switching of Fluorescent Borylated Arylisoquinolines for Multilevel Molecular Logic

Abstract

The preparation of pH-switchable fluorescent borylated arylisoquinoline dyes via a flexible iridium-catalyzed route is reported. The obtained dyes feature aromatic amino substitution and lateral aliphatic amino groups as electron donors. The photophysical properties of the internal charge transfer dyes were studied, which was complemented by density functional theory calculations. Appreciable fluorescence quantum yields (Φf up to ca. 0.4) and characteristic spectral fingerprints in the green to red emission range were observed. The fluorescence modulation upon multiple and orthogonal protonation with triflic acid was studied and led to the interpretation of multilevel switching including off-on-off, ternary, and quaternary responses.

Molecular Switches as Platforms for Information Processing

“…However, for information process stepwise protonation at lateral amino func tions and at the isoquinolinyl moiety. [29] In general, similar off-on-off behavior as seen for compound 2 could be expected and indeed, for compound 3 this is the case. The first protonation step at the piperazinyl moiety blocks PeT, as discussed for 2, and the second protonation at the isoquinolinyl leads to quenching.…”

Strongly Emissive and Photostable Four‐Coordinate Organoboron N,C Chelates and Their Use in Fluorescence Microscopy

“…This was motivated by our earlier studies of arylisoquinoline boronic esters (BAI dyes) whose fluorescence properties can be conveniently controlled by the variation of electronic properties of substituents, protonation or temperature. [25][26][27] The herein investigated N,C chelates (see structures in Scheme 1) feature a higher -conjugation than the abovementioned photochromic B(ppy)Mes2 compounds. [23] In addition they contain electrondonating substituents and the electron-accepting isoquinolinyl moiety.…”

“…This has been already verified previously for related borylated arylisoquinoline (BAI) dyes. [26] Expectedly, for such a situation the fluorescence quantum yield should drop in more polar solvents as a consequence of a more favored PET. Indeed, the quantum yield in toluene is 0.…”

Information gathering and processing with fluorescent molecules

“…The result in this non-aqueous medium can also be described as a double-input XOR logic gate with degenerate H + inputs. 5 More benzannellated derivatives of 15 show multi-valued outputs as well, 99 adding further to the usefulness of this study.…”

“…A nice new case of this general type, 15, which actually has the format 'receptor1-spacer1-fluorophore-receptor2' is described by Pischel, Ros and their collaborators. 99 A closely related format 'receptor1-spacer1-receptor2-fluorophore' is known. 100 Viewed simplistically, 15 contains a tertiary amine to serve as receptor1 and an isoquinoline to serve as receptor2.…”