N‐Substituted Azacalixphyrins: Synthesis, Properties, and Self‐Assembly

Abstract

Pre- and postintroduction of substituents with respect to the macrocyclization step leads to previously unknown N-substituted azacalixphyrins. The stepwise synthetic approach has been studied in detail to highlight the key role of the N-substituents of the precursors and/or intermediates in terms of reactivity. Based on a combined experimental and theoretical investigation, the relationship between the properties of the macrocycles and their degree of substitution is rationalized. Depending on the nature of the N-substituents, the formation of supramolecular ribbon-like structures could also be observed, as demonstrated by combined TEM, SEM, AFM, and FTIR experiments.

Central substitution of azacalixphyrins: a strategy towards acidochromic NIR dyes

“…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. First, both Density Functional Theory (DFT) and X-Ray Diffraction (XRD) indicate that ACP adopts a saddle-like conformation due to the repulsion of the four central hydrogen atoms, but that the electron delocalisation is high with only two types of bonds (CN and CC) presenting equivalent distance in the macrocyclic core (in red in Figure 1a).…”

“…To circumvent this problem, substituted azacalixphyrins containing alkyl chains at the periphery have been synthesised and characterised both experimentally and theoretically. 13 The different derivatives considered (BH 2+ 2 -DH 2+ 2 ) are represented in Figure 2 and differ in: (i) the number of alkyl chains (symmetric R 1 =R 2 =Alkyl vs. asymmetric R 1 =Alkyl, R 2 =H substitutions); (ii) the length of the chains (C 4 H 9 vs. C 8 H 17 ); and (iii) their spatial arrangement (branched vs. linear chains). These derivatives present similar features as the parent AH 2+ 2 in terms of global shape, aromaticity, redox and optical properties though the NIR absorption band undergoes very small redshifts when the number of alkyl substituents is increased.…”

“…Indeed, only the ACPs possessing four C 8 chains, namely DH 2+ 2 , were able to form molecular ribbons. 13 To explore further strategies allowing to modulate the optical properties of the azacalixphyrin, two theoretical investigations were performed at Time-Dependent DFT (TD-DFT) level, for putative N-arylated and metal-complexed ACPs. 12,14 For the former, redshifts of the NIR band of up to ca.…”

“…Structure of N-alkylated azacalixphyrins in their di-protonated forms synthesised and characterised in Ref. 13. The index a indicates that the ACP is asymmetrically substituted, i.e., at positions R 1 only.…”

N1-(5-Fluoro-2,4-dinitrophenyl)-N2-phenyl-4-(trifluoromethyl)benzene-1,2-diamine

“…1,5-Difluoro-2,4-dinitrobenzene (1) can also be used to enable the chromatographic resolution of chiral secondary alcohols [12]. More recently, difluorodinitrobenzene 1 has been extensively used as a monomer unit to prepare unusual azamacrocycles via cyclooligomerisation chemistry [13][14][15][16][17][18][19].…”