16689-35-3Relevant articles and documents
Versatile synthesis of chiral 6-oxoverdazyl radical ligands-new building blocks for multifunctional molecule-based magnets
Solea, Atena B.,Wohlhauser, Tobie,Abbasi, Parisa,Mongbanziama, Yvan,Crochet, Aurelien,Fromm, Katharina M.,Novitchi, Ghenadie,Train, Cyrille,Pilkington, Melanie,Mamula, Olimpia
, p. 4785 - 4789 (2018)
A versatile synthetic methodology to access the first family of chiral verdazyl N,N′-chelate ligands is described and exemplified by N,N′-dimethyl-, N,N′-di-isopropyl- and N,N′-diphenyl oxoverdazyls bearing two isomers of the pinene-pyridine functional group. Their physical properties were probed by X-band EPR spectroscopy, cyclic voltammetry and DFT calculations. Preliminary reactivity studies show they can act as N,N′-chelate ligands affording a chiral 1:1 complex (3b) with CuCl2, which was characterized by single-crystal X-ray diffraction. Variable temperature EPR studies on (3b) confirm the presence of antiferromagnetic interactions between the spins of the Cu(ii) ion and the verdazyl radical.
Synthesis of Macrocycles Derived from Substituted Triazines
Yepremyan, Akop,Mehmood, Arshad,Asgari, Parham,Janesko, Benjamin G.,Simanek, Eric E.
, p. 241 - 246 (2018/12/11)
A triazine ring derivatized with morpholine, an N-alkyl-N′-BOC-hydrazine (alkyl=isopropyl or benzyl) and the diethylacetal of glycinylpropionaldehyde undergoes spontaneous dimerization in good yields upon acid-catalyzed deprotection. The resulting 24-member macrocycles can be characterized by NMR spectroscopy, mass spectrometry, and single crystal X-ray diffraction. In the solid state, both homodimers adopt a taco-like conformation. Although each shows π–π stacking between the triazine rings, different patterns of hydrogen bonds emerge. The crystal structure of the isopropyl dimer shows that it includes two molecules of trifluoracetic acid per macrocycle. The trifluoroacetate anion charge balances the protonated triazines, which engage in bifurcated hydrogen bonds with the carbonyl acceptor of the distant glycine. This carbonyl also forms a hydrogen bond with the NH of the proximate glycine. The crystal structure of the benzyl derivative does not include trifluoracetic acid. Instead, two hydrogen bonds form, each between a glycine NH and the lone pair of the C=N nitrogen of the hydrazine group. In the solid state, both molecules present the alkyl side chains and morpholine groups in close proximity. A heterodimer is accessible in approximately statistical yields—along with both homodimers—by mixing the two protected monomers prior to subjecting them to deprotection.
Crystallographic Insights into the Synthesis and Magnetic Properties of Oxoverdazyl Radicals Functionalized by Benzoic Acid
Kumar, Varun,Shova, Sergiu,Maurel, Vincent,Novitchi, Ghenadie,Train, Cyrille
supporting information, p. 517 - 524 (2017/11/28)
The synthesis and crystallization of two verdazyl radicals, 1,5-dimethyl-3-(4′-carboxyphenyl)-6-oxoverdazyl HIMe and 1,5-diisopropyl-3-(4′-carboxyphenyl)-6-oxoverdazyl HIiPr, are described. The electrochemical studies reveal that the oxidation of the two radicals is reversible, whereas their reduction is irreversible. The EPR spectrum of both radicals essentially exhibits a nine-line pattern related to the mean hyperfine interaction of the unpaired electron with the nitrogen atoms of the verdazyl cycle. The single-crystal X-ray diffraction of the intermediates towards HIiPr allows a fine description of the cyanoborane adduct, which is the key intermediate of this synthesis. The verdazyl radicals themselves are obtained as single crystals. In the case of HIiPr, depending on the solvent, two polymorphs are crystallized. The structure resolution reveals that, in the solid state, the organization of the verdazyl radicals is governed by both H-bonding and π–π interactions and is reminiscent of the H-bonded structures that can be present in solution. Within the 1D π stacks observed in the three compounds, the verdazyl–verdazyl distance varies from 4.88 ? in HIMe to 7.90 ? in HaIiPr. This modulation of the distance strongly influences the antiferromagnetic intermolecular exchange interaction between π-stacked radicals, which goes from J = –90 cm–1 (H = –JΣSiSi+1) for HIMe to –12.96(3) cm–1 for HbIiPr and –0.92 cm–1 for HaIiPr.
