Breaking Azacalix[4]arenes into Induline Derivatives.

Tetraamino-tetranitro-azacalixarene 5 is at the crossroad of two different families of compounds depending on the conditions and the agent used to reduce the NO2 groups: (1) azacalixphyrin 7 in neutral medium, or (2) phenazinium of type 8 in acidic medium. The key role of the N-substituted amino functions at the periphery is highlighted by investigating octaaminoazacalixarene as a model compound, and by using the corresponding tetrahydroxy-tetranitro-azacalixarene 15 as a precursor, which behaves differently.

Tris-benzo[cd]indole Cyanine Enables the NIR-photosensitized Radical and Thiol-ene Polymerizations at 940†nm.

A near-infrared-absorbing heptamethine (HM+ ) incorporating three bulky benzo[cd]indole heterocycles was designed to efficiently prevent self-aggregation of the dye, which results in a strong enhancement of its photoinitiating reactivity as compared to a parent bis-benzo[cd]indole heptamethine (HMCl+ ) used as a reference system. In this context, we highlight an efficient free-radical NIR-polymerization up to a 100 % acrylates C=C bonds conversion even under air conditions. Such an important initiating performance was obtained by incorporating our NIR-sensitizer into a three-component system leading to its self-regeneration. This original photoredox cycle was thoroughly investigated through the identification of each intermediary species using EPR spectroscopy.

Insights into extended coupled polymethines through the investigation of dual UV-to-NIR acidochromic switches based on heptamethine-oxonol dyes.

A series of heptamethine-oxonol dyes featuring different heterocyclic end groups were designed with the aim to explore structure-property relationships in π-extended coupled polymethines. These dyes can be stabilised under three different protonation states, affording dicationic derivatives with an aromatic core, cationic heptamethines, and zwitterionic bis-cyanine forms. The variation of the end groups directly impacts the absorption and emission properties and mostly controls reaching either a colourless neutral dispirocyclic species or near-infrared zwitterions. The acidochromic switching between the three states involves profound electronic rearrangements leading to notable shifts of their optical properties that were investigated using a parallel experiment-theory approach, providing a comprehensive description of these unique systems.