Di- vs. tetra-substituted quinonediimines: a drastic effect on coordination chemistry

Abstract

We describe the first isolation of N,N'-disubstituted benzoquinonediimines (QDIs) 2 which revealed drastically different properties compared to N,N',N'',N'''-tetrasubstituted QDIs 1 due to the absence of N-substituents in the "upper part" of the molecule. Three major differences could be highlighted thanks to the present joint experimental and theoretical investigation: (1) the metalation with different metal precursors revealed a specific behaviour in coordination chemistry giving access to novel complexes with unprecedented stoichiometry and remarkable absorption properties. More specifically, a new monoplatinum complex that is able to absorb light from the UV up to the NIR region because of its unique delocalization pathway across the metal centre was obtained; (2) this new class of di-substituted QDIs showed an exceptionally broad pK range (ΔpK∼ 8) that could be explained by the possible tuning of the basicity of each imine which is now attainable; (3) these quinones could be used as reagents in organic synthesis to form the previously unknown N,N',N'',N'''-tetrasubstituted QDIs with tuneable substituents (aryl vs. alkyl), previously unknown, as a new ligand for coordination chemistry.

Azacalixphyrins as NIR photoacoustic contrast agents

“…, upon peripheral substitution with octylamine moieties, a slight redshift is recorded for compound hyperchromic effect (ε 897 = 14900 M 10c First, N,Nized as described in the literature, 12 and then diisopropylethylamine (DIPEA) to afford in refluxing acetonitrile to form . Eventually, the four nitro groups of this series of macrocycles were reduced in presence of hydrazine monohydrate and Pd/C under heating to reach the corresponding colourless octaamino-azacalix[4]arene 3a-c under aerobic conditions.…”

Near-infrared dyes for two-photon absorption in the short-wavelength infrared: strategies towards optical power limiting

“…900 nm due to a unique delocalization pathway in trans fashion across the metal centre. 224 In the light of these selected examples, we illustrated that few families of dyes absorbing in the NIR exist and that their designs rely on established strategies comparable to the one used for the enhancement of 2PA. In fact, it appears that the most used techniques to shift the optical properties are the optimization of the ICT, the stiffening of the structure and the extension of the -conjugation, possibly through (macrocyclic) oligomerization.…”

Azacalixquinarenes: From Canonical to (Poly-)Zwitterionic Macrocycles

“…This analysis is corroborated by theoretical calculations (see Figure S34 and Table S9). Quinones 1b and 1c , which possess trimethoxyaniline and m -trifluoromethylaniline moieties, do not present such a transition, which hints at a prominent canonical ground state for these compounds, the strong UV band and its tail in the visible region being classical features of tetrasubstituted diaminobenzoquinone diimines. , In contrast, the absorption of p -dimethylaminoaniline-substituted 1d shows a panchromatic absorption spanning from 400 to 800 nm. Two main transitions can be identified at 654 and 570 nm and are counterintuitively theoretically attributed to the forms c -1d and z -1d , respectively (vide infra).…”

“…Quinones trifluoromethylaniline moieties do not present such tra these compounds, the strong UV band and its tail in the visible region being classical features of tetra diamino benzoquinone diimines. 39,40 In co chromatic absorption spanning from 400 to 800 nm. Two main transitions can be ident counter-intuitively theoretically attributed to the for tween the canonical cycles and 4.270(4) Å between the aromatic ones, while the dihedral angles are equal to 7.5(3)° and 1.6(3)° respectively.…”