Thermally stable organic diradicals with at riplet ground state along with large singlet-triplet energy gap have significant potential for advanced technological applications.A series of phenylene-bridged diradicals with oxoverdazyla nd nitronyl nitroxide units were synthesized via ap alladiumcatalyzedc ross-coupling reaction of iodoverdazyls with an itronyl nitroxide-2-ide gold(I) complex with high yields.T he diradicals exhibit high stability and do not decompose in an inert atmosphere up to 180 8 8C. Fort he diradicals,b oth substantial AF (DE ST %À64 cm À1)a nd FM (DE ST ! 25 and 100 cm À1)intramolecular exchange interactions were observed. The sign of the exchange interaction is determined both by the bridging moiety (para-or meta-phenylene) and by the type of oxoverdazylb lock(C-linked or N-linked). Upon crystallization, diradicals with the triplet ground state form unique onedimensional exchange-coupled chains with strong intra-and weak inter-diradical ferromagnetic coupling.

Thermally resistant air-stable organic triradicals with a quartet ground state and a large energy gap between spin states are still unique compounds. Moreover, stable triradicals with bridging units of the ethylene-1,1-diyl type and ferromagnetic coupling are limited to the family of nitroxides. In this work, for the first time, we designed and prepared the triradical having a quartet ground state based on oxoverdazyl and nitronyl nitroxide radical fragments. The triradical and appropriate triplet diradical precursor were synthesized via a palladium-catalyzed cross-coupling reaction of diiodoverdazyl with nitronyl nitroxide-2-ide gold(I) complex. Both the di-and triradical are air-stable and possess good thermal stability with decomposition onset at ∼160 °C in an inert atmosphere. X-ray diffraction analysis of single crystals confirmed the presence of verdazyl and nitroxide radical centers. In the diradical, the verdazyl and nitronyl nitroxide centers showed fully reversible redox waves. In case of the triradical, the electrochemical processes occur practically at the same redox potentials but become quasi-reversible for the nitroxide moieties. Magnetic properties of the di-and triradical were characterized by a SQUID magnetometry of polycrystalline powders and by EPR spectroscopy in different matrices. Collected data analyzed using of the highlevel quantum chemical calculations confirmed that the di-and triradical have high-spin ground states. Unique high stability of prepared verdazyl-nitronylnitroxyl triradical opens new perspectives for further functionalization and design of high-spin systems with four or more spins.

A series of Zn(hfac)2 alkoxyamines (diethyl(2,2‐dimethyl‐1‐(tert‐butyl‐(1‐pyridylethoxy)amino)propyl)phosphonate) coordinated at ortho, meta and para positions of their pyridyl moiety were prepared and their homolysis rate constants kd measured. Up to a 30‐fold increase in kd was observed for the meta‐(Zn‐RR/SS) and para‐(Zn‐RR/SS) regioisomers. Moreover, the activation is also controlled by the amount of pyridine, used as a ligand competitor. XRD, 1H and 31P NMR spectra show very different structures for each complexes in solid state and in solution depending on the diastereosiomers and on the regioisomers.

Preparation of materials by nitroxide-mediated polymerization (NMP) is well known nowadays. To increase the possible usefulness of NMP for the production of hybrid materials or polymer-decorated complexes, coordination-initiated NMP (CI-NMP) was developed and investigated here. CI-NMP was exemplified using the instantaneous and spontaneous reaction of alkoxyamines carrying a pyridyl moiety on the alkyl group and the Zn(hfac)2 (hfac: hexafluoroacetylacetonate) complex as a metal centre. NMP of styrene and n-butyl acrylate was carried out with either previously or in situ-prepared complexes. Both approaches afforded NMP of the same quality. The positive influence of metal centre coordination is highlighted by efficient NMP at 90°C.

The metal complexation reactions of bis(hexafluoroacetylacetonato)copper(II) (Cu(hfac) 2 ) with alkoxyamines (diethyl(2,2-dimethyl-1-(tert-butyl-(1-( pyridine-4-yl)ethoxy)amino)propyl)phosphonate and diethyl (2,2-dimethyl-1-(tert-butyl-(1-( pyridine-2-yl)ethoxy)amino)propyl)phosphonate) were studied.According to X-ray analysis, the molecular and crystal structures of 1 : 1 complexes depend on the configuration of the free alkoxyamines, that is dimeric (RSSR) and chain-polymeric (RR/SS) structures for para-pyridylsubstituted alkoxyamines, and cyclic unimeric (RS/SR) structure for ortho-pyridyl derivative. The complex(2 : 1 ratio Cu(hfac) 2 /alkoxyamine) for ortho-pyridyl-substituted alkoxyamine is not resolved. Upon warming, ortho complexes decomposed into free alkoxyamines and only a weak activation was observed. Upon warming, para complexes decomposed into their corresponding unimers, and then, a 21-fold increase in the rate constant of the C-ON bond homolysis was observed compared to the corresponding free alkoxyamines. Tuning of the homolysis rate constant of the C-ON bond via addition of pyridine is also reported.Scheme 1 C-ON bond homolysis in alkoxyamine. † Electronic supplementary information (ESI) available: Preparation, characterization, and Table S1 with XRD data of complexes 7 and 8. Fig. S1 ( 1 H NMR) and S2 ( 31 P NMR) of complexes 7 and 8. CCDC 1483562-1483565. For ESI and crystallographic data in CIF or other electronic format see View Article Online ‡ ‡ Here, k d is considered as the apparent rate constant of the C-ON bond homolysis. § § The equilibrium implying the scavenger and pyridine is disregarded. ¶ ¶ For eqn (6), a first order growth might be observed provided k 3 ·k 5 ·[P] is larger than k −1 ·(k −3 + k 5 ).