Synthesis, crystal structures and the preliminary evaluation of the new dibenzotetraaza[14]annulene-based DNA/RNA binding agents

Multichromophore arrays of dibenzotetraaza[14]annulene: a promising platform for bioorganic chemistry

The first series of discrete multichromophore arrays of dibenzotetraaza[14]annulene (DBTAA), containing flexible bridges, have been synthesized in 40-46% isolated yields. The key asymmetrical intermediates, carrying two distinctly addressable functionalities (ROH vs. ROCH2-C[triple bond, length as m-dash]C-H and R(CH2)nBr vs. ROCH2-C[triple bond, length as m-dash]C-H) at the macrocycle periphery, were synthesized in moderate to high (30-78%) isolated yields. Facile synthetic protocols developed for the synthesis of discrete DBTAA arrays offer several advantages such as operational simplicity and easy post-synthetic workup that overcome the need for laborious chromatographic purification. All new compounds were characterized by microanalysis, mass spectrometry, UV-Vis, FTIR-ATR, and 1H and 13C NMR spectroscopy. Structural features were briefly discussed with emphasis on several potential applications.

New developments in porphyrin-like macrocyclic chemistry: a novel family of dibenzotetraaza[14]annulene-based cofacial dimers

The first known cofacial dimers, based on covalently linked dibenzotetraaza[14]annulenes, were synthesized in reasonable 35–40% yields, without recourse to high-dilution techniques.

Noncovalent functionalization of graphene with a Ni(II) tetraaza[14]annulene complex

The few-layer graphene, produced by exfoliation of graphite in 4-methylanisole, was noncovalently functionalized with the Ni(ii) complex of 5,7,12,14-tetramethyldibenzo-1,4,8,11-tetraazacyclotetradeca-3,5,7,10,12,14-hexaene (Ni(ii)-tetramethyldibenzotetraaza[14]annulene, or NiTMTAA), which is a simple model of more complex porphyrins and phthalocyanines. The resulting hybrid materials with different content of NiTMTAA were characterized by means of thermogravimetric analysis, scanning and transmission electron microscopy (SEM and TEM, respectively), atomic force microscopy (AFM), energy dispersive X-ray, Fourier-transform infrared (FTIR), Raman and UV-visible spectroscopy, as well as fluorescence and conductivity measurements. Additional information on the mechanisms of NiTMTAA interaction with graphene was obtained from density functional theory (DFT) and molecular mechanics (MM) calculations. Both experimental and theoretical results suggest that NiTMTAA forms a full double-sided adsorption layer on the graphene surface. The presence of NiTMTAA molecules in the hybrid materials obtained manifests itself in the appearance of characteristic bands in all types of electromagnetic spectra recorded; in FTIR, they are relatively weak as compared to graphene absorption bands, but dominate in Raman spectra. The morphology of the nanohybrids observed by SEM, TEM and AFM, as well as their electrical conductivity, depends on the NiTMTAA content. According to the results of DFT calculations of NiTMTAA adsorption on different graphene models, flat orientation of the complex with respect to graphene is energetically preferable, with a little difference depending on whether benzo or methyl groups contact the sheet.

The dicationic derivatives of DBTAA: Interactions with DNA/RNA and antiproliferative effects on human cell lines

Three dibenzotetraaza[14]annulenes non-covalently interacted with double-stranded DNA and RNA by mixed minor groove and/or intercalative binding mode. Observed interactions were strongly dependent on the steric exposure of positive charges and the length of the linkers of studied compounds as well as on the secondary structure and basepair composition of DNA/RNA. Compound 2 showed pronounced selectivity toward dA-dT-rich sequences and binding mode switch from dominant minor groove binding to ds-DNA to dominant intercalation into ds-RNA. Antiproliferative effect of studied compounds on human tumor and normal cell lines was in good agreement with the strength of observed interactions with DNA/RNA.