(Azulene‐1,3‐diyl)‐bis(nitronyl nitroxide) and (Azulene‐1,3‐diyl)‐bis(iminonitroxide) and Their Copper Complexes

Abstract

In contrast to diradicals connected by alternant hydrocarbons, only a few studies on those connected by nonalternant hydrocarbons have been reported. The syntheses, structures, and magnetic properties of azulene-1,3-diyl linked bis(nitronyl nitroxide) (NN Az) and bis(iminonitroxide) (IN Az) diradicals and their Cu(hfac) (hfac=hexafluoroacetylacetonate) complexes were investigated. NN Az was shown to have an intramolecular ferromagnetic interaction with J /k =+10.0 K (H=-2JS ⋅S ) between (nitronyl nitroxide) spins, whereas IN Az was estimated to have a much weaker intramolecular magnetic interaction. The reactions of NN Az and IN Az with Cu(hfac) gave a 1:2 [{Cu(hfac) } (NN Az)] complex and a 1:1 [Cu(hfac) (IN Az)]⋅C H complex, respectively. [{Cu(hfac) } (NN Az)] showed strong intramolecular antiferromagnetic interactions (J /k ≈-800 K, J /k ≈-500 K) between the Cu spins and the coordinating NN spins, whereas [Cu(hfac) (IN Az)] exhibited a ferromagnetic exchange interaction (J /k =+114 K) between the Cu spin and the imino-coordinated iminonitroxide spin.

Construction of Polycyclic π‐Conjugated Systems Incorporating an Azulene Unit Following the Oxidation of 1,8‐Diphenyl‐9,10‐bis(phenylethynyl)phenanthrene

“…Moreover, recent advances in transition metal‐mediated functionalizations such as borylation, arylation, and silylation have provided methods to develop fascinating azulene‐based materials . Unlike alternant π‐conjugated systems, the non‐alternant structure of azulene contributes to the construction of peculiar π‐conjugated systems . In addition to the electronic perturbations of the alternant π‐conjugated systems, many three‐dimensional nanocarbon structures with curvature have been proposed by embedding pentagons or heptagons in the hexagonal honeycomb lattice .…”

“…[15][16][17][18] Unlike alternant p-conjugated systems, the non-alternant structure of azulenec ontributes to the construction of peculiar p-conjugated systems. [19][20][21][22][23][24][25][26] In addition to the electronic perturbations of the alternant p-conjugated systems, many three-dimensional nanocarbon structuresw ith curvature have been proposed by embedding pentagons or heptagonsi nt he hexagonal honeycomb lattice. [5,[27][28][29][30][31] Thus, the embedding of an azulenec ore into alternant PAHs could change both the molecular geometry and the electronicp roperties of the originalP AHs.…”

Triplet Diradical‐Cation Salts Consisting of the Phenothiazine Radical Cation and a Nitronyl Nitroxide

“…The exchange interaction for the same contact in the gallium salt was the smallest positive value of J calcd-inter =+0.03 K. As stated above,t he DFT calculations usually overestimate the ferromagnetic contributions to the intramolecular J value for diradicals, but are useful to estimate those of intermolecular interactions of diradicals. [25,26] At this level of calculation, av alue smaller than 0.1 Ki sn ot reliable. The FeBr 4 salt has an almost identical intermolecular CÀCc ontact of [···(DAA-PTZ) + ···(DAA-PTZ) + ···] and as mall negative value of J calcd-inter = À1.2 Kw as found (see Ta ble S7).…”

Synthesis and Magnetic Properties of (Pyrrolidin‐1‐oxyl)–(Nitronyl Nitroxide)/(Iminonitroxide)‐Dyads

“…Interestingly,t he positive (red) and negative (green) spin densities aligned alternately in the shortest connecting path through the small spin density on the sp 3 -carbona tom. [4] Consequently,t he ground states of these diradicals can be explainedb yt he spin polarization model for both series of diradicals (triplet diradicals 3 and 4; singlet diradicals 5 and 6). It shouldb en oted that compound 5 exhibited am ore negative spin density on the sp 3 -carbon atom with am ore negative2 J/k B value than that of 6 (À0.04 for 5 and À0.03 for 6).…”

“…[2] Diradical systems linked by p-frameworks have been extensively studied and their intramolecular spin-alignmentc an be predicted by parity-basedm odels, the dynamic spin polarization model,a nd the disjoint and nondisjoint (coextensive) model. [3,4] In contrast, few studies have investigated diradicals linked by sp 3 carbon atoms (Figure 1). [5][6][7] For instance, Keana and co-workersr eported that the spiro-dinitroxide diradical 1 had in as inglet ground state with weake xchange interaction (2J/k B %À12 K), although the D value is extremely large in dinitroxide diradical systems.…”