Synthesis of Novel Aromatic Nitroxides as Potential DNA Intercalators. An EPR Spectroscopical and DFT Computational Study

Abstract

The synthesis and electron paramagnetic resonance (EPR) spectroscopic properties of three novel aromatic nitroxides and potential DNA intercalators, the carbazole-based 3,6-dimethylcarbazole-9-oxyl, as well as the acridane-based 9-acridanylidenemalonitrile-10-oxyl and 9-ethylacridanylidenecyanoacetate-10-oxyl, are described. The two acridane-based nitroxides can be isolated and are stable in solution as well as in the solid state for several days. Continuous wave X-band EPR measurements and density functional theory (DFT) calculations demonstrated that the spin density is delocalized over the whole molecule in all three cases. Furthermore, the DFT calculations provided insight into the molecular and electronic structures of these nitroxides and yielded hyperfine coupling constants which are in very good agreement with the experimental data allowing therefore an unambiguous assignment of the hyperfine couplings.

A multi-step procedure for evaluating the EPR parameters of indolinonic aromatic aminoxyls: A combined DFT and spectroscopic study

“…In Table 2 [14]. This behavior was previously observed for INDCO too by means of polarized neutron diffraction (PND) [21] and ENDOR [22] techniques; accordingly, in Fig.…”

“…computed at different levels of theory, and the corresponding experimental ones available from X-rays [22] is possible from the data collected in Table 3, while in Table 4 their deviations from experimental values (D) are reported. The excellent correspondence becomes impressive with PBE0/ 6-31G (d) and PBE0/EPR-III for the N-O bond, though these methods yielded 14 N hfcc values rather far from the experimental ones (see Table 1 and Supplementary Table 1) probably due to an excessive underestimation of the spin density on that nucleus (see Table 2). Conversely, B3LYP/ 6-31G gave the best estimate for the 14 N hfcc but the worst fit for the N-O bond length at the same time.…”

“…Despite this fact, while many studies on the comparison between experimental and computed EPR properties of ''non-conjugated'' aminoxyls are available [13], only a very few of them deal with aromatic nitroxides [14].…”

Synthesis and Evaluation of New Nitrone-Based Benzoxazinic Antioxidants

“…The ability of nitrones to act as good radical traps has been widely researched over the last decades [1][2][3][4][5]. For years, nitrones have been used as efficient analytical tool for the detection and characterization of free radicals using EPR Spin Trapping Technique, based on their ability to quickly trap short-lived free radicals and afford persistent and identifiable aminoxyl spin adducts [6][7][8][9]. Due to this unique ability, nitrones have attracted considerable attention as potential therapeutic agents for the treatment of many pathologies where reactive oxygen species (ROS) are implicated, such as cardiovascular diseases, cancer, aging, cerebral ischemia and various neurodegenerative diseases [10][11][12].…”

Endohedral dynamics of push–pull rotor-functionalized cages

“…Compounds based on the same structural motif have been previously examined as luminescent materials, 29 conductive polymers 30 and EPR labels for DNA. 31 We were interested in the structural dynamics of the system in the context of supramolecular self-assembly, since the push-pull character of the underlying conjugated system ( Fig. 1c) was expected to allow for rotation around the CQC double bond in a kinetic regime comparable to the dynamics of supramolecular host-guest systems.…”