Azacalixphyrin: The Hidden Porphyrin Cousin Brought to Light

Abstract

No pyrrol: Azacalixphyrin (see picture), a novel isostructural and isoelectronic “pyrrol‐free” analogue of porphyrins is easily prepared in two straightforward steps. The azacalixphyrin is aromatic, absorbs in the entire visible region, and is highly stable (even in the presence of water under air) owing to its unusual bis‐zwitterionic character.

Central substitution of azacalixphyrins: a strategy towards acidochromic NIR dyes

“…[15][16][17] A surprising feature of the azacalixphyrin parent, given its zwitterionic nature, is its high chemical stability, i.e., ACP remains stable when exposed to air for months as a solid and for days in solution. 9 This stability can be rationalised not only by its aromatic nature, as confirmed by the calculated Nucleus Independent Chemical Shift (NICS), but also by showing that the possible hydrolysis mechanisms of ACP are all coming with very high reaction barriers making them kinetically impossible. 10 Another feature of the ACP, relevant for the present study, is its tautomerism occurring in the neutral form.…”

“…The first member of this new family is compound AH 2+ 2 (see Figure 1a) that has been first synthesised in 2013 and characterised both experimentally and theoretically by the groups involved in the present investigation. 9 AH 2+ 2 strongly absorbs in the visible as well as in the UV and NIR regions (between 300 and 1000 nm). The term "azacalixphyrin" is actually the concatenation of "azacalixarene" and "porphyrin" (Figure 1b) and has been proposed to underscore the similarities that ACP presents with these two macrocycles.…”

“…ation properties which makes it a very promising platform for applications in a wide range of research fields, 9 and several developments and analyses of the ACPs have indeed appeared in the last few years. [10][11][12][13][14] Let us summarise the main findings obtained up to now, starting by the unsubstituted ACP.…”

1,3‐Alternate Tetraamido‐Azacalix[4]arenes as Selective Anion Receptors

“…The preparation of the symmetrical tetraamido-tetraaza[1.1.1.1]m,m,m,m-cyclophanes 7-10 relies on ad ifferent twostep synthetic procedure that allows access to numerousderivatives because the introductiono ft he amide groups is performed after the macrocyclization (Scheme 1). The condensation of 1 on the 1,2,4,5-tetraaminobenzene (formed in situ by deprotonation of its tetra-hydrochloric salt 5)g ives, as previously described, [26] ah igh yield of tetraamino-azacalix [4]arene 6.T he oxidation that usuallya ffects electron-rich tetra-aminobenzene units [27] is here avoided through their connections with strong electron-withdrawing dinitro-aryl groups.T he condensation between the tetraamino derivative 6 with 4t o1 0 equivalents of acyl chlorides in MeCN heated to reflux afforded tetraamido-tetraazacalix [4]arenes 7-10 with yields ranging from 32 to 87 %. The 1,3-alternate conformationo f6,p robed by monitoring the 1 HNMR singlet of its hydrogen atoms H-1 located at d = 4.98 ppm in [D 6 ]DMSO, induces as patial proximity between the four appended amine groups.…”

“…Organicsynthesis 1-Benzyl-4-dimethylaminopyridinium bromide, [28] 4-dimethylaminopyridinium bromide, [29] 4,5-diamino-1,2-bis(2,2-dimethylpropionamido)benzene (2b), [25] 4,6,17,19-tetranitro-2,8,15,21-tetraazacalix[4]arene (4c), [24d] and 4,6,16,18-tetranitro-10,12,22,24-tetraamino-2,8,14,20-tetraazacalix[4]arene (6) [26] were prepared and purified according to reported procedures. N 1 ,N 2 -Bis (5-fluoro-2,4-dinitrophenyl)benzene-1,2-diamine( 3a):A solution of 1, 5-difluoro-2,4-dinitrobenzene 1 (2.52 g, 12.35 mmol, 2equiv) in THF (50 mL) was cooled with an ice-water bath before as olution of benzene-1,2-diamine 2a (666 mg, 6.…”