Coordinated NO Group Research Articles

2p-4f Loop-chains {[Ln(hfac)3]2-radical}n achieved through multidentate nitronyl nitroxide radicals

Reactions of the designed multidenate nitronyl nitroxide radical ligands Nit-pH-3,5-bPy or Nit-pH-3,5-btrz (Nit-pH-3,5-bPy = 2-[3,5-bis(4-pyridyl)-phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; Nit-pH-3,5-btrz = 2-[3,5-bis(1H-1,2,4-triazol-1-yl)-phenyl]-4,4,5,5- tetramethylimidazoline-1-oxyl-3-oxide) with Ln(hfac)3 obtained four rare Ln-radical loop-chains, namely, {[Ln(hfac)3]2(Nit-pH-3,5-bPy)}n (LnIII = Gd 1, Tb 2; hfac = hexafluoroacetylacetonate) and {[Ln(hfac)3]2(Nit-pH-3,5-btrz)}n (LnIII = Tb 3, Ho 4). In all complexes, each pyridyl- or triazolyl-functionalized radical ligand is binded to four Ln(hfac)3 centers with a μ4-η1:η1:η1:η1-coordination mode through its two NO units and two N atoms of pyridines/triazoles, giving rise to interesting radical-bridged loop-chains with the scarcely reported 4f-2p-4f structural motifs. Magnetic measurements indicate that there are ferromagnetic interactions between the Ln(III) ions and the coordinated NO groups in these compounds. Tb 2 exhibits clear frequency-dependent out-of-phase (χ′′) signals in a zero dc field indicating slow relaxation of magnetization, while no non-zero χ′′ signals are observed for Tb 3 without an external magnetic field, which could be ascribed to the slightly different heterocyclic ligands.

Two Cu(II)-Nitronyl Nitroxide Complexes Including Cyclic Dimer: Synthesis, Structures and Magnetic Interactions

Using two new flexible and functional nitronyl nitroxide radicals as ligands, two copper (II) complexes {[Cu(hfac)2]3(NITmPhO3Py)2}n (1) and [Cu(hfac)2 (NIToPhO3Py)]2 (2) (NITmPhO3Py = 2-[(3-methoxy-pyridinyl)phen-3-yl]- 4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, NIToPhO3Py = 2-[(3-methoxy-pyridinyl)phen-2-ly]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, hfac = hexafluoroacetylacetone), have been characterized structurally and magnetically. The X-ray crystal analyses showed that complex 1 displayed a chain polymer structure which formed with {[Cu(hfac)2]3(NITmPhO3Py)2}n due to the cross-linking of two cyclic binuclear fragments {[Cu(hfac)2]2(NITmPhO3- Py)2} via the bridging unit [Cu(hfac)2]; complex 2 presented a binuclear cyclic structure [Cu(hfac)2]2(NIToPhO3Py)2. The magnetic behaviors of the two complexes 1 and 2 have been investigated. Magnetic studies showed that antiferromagnetic interactions dominated in complex 1, while there existed ferromagnetic interactions between Cu(II) and coordinated NO group in complex 2.

Two 2p-3d-4f complexes constructed from functionalized nitronyl nitroxides: Synthesis, structure and magnetic properties

Two 2p-3d-4f complexes of [LnCu(hfac)5NIT-Ph-p-OCH2trz]n (Ln = Gd (1), Ho (2); NIT-Ph-p-OCH2trz = 2-(4-((1H-1,2,4-triazol-1-yl)methoxy)phenyl)-4,4,5,5-tetra- methylimidazoline-1-oxyl-3-oxide; hfac = hexafluoroacetylacetonate) have been successfully synthesized through Cu(hfac)2 and Ln(hfac)3 reacting with nitronyl nirtroxide radical of NIT-Ph-p-OCH2trz. The structures of complexes 1 and 2 were elucidated by single-crystal X-ray structural analysis and the results show that both complexes consist of [Ln-NIT-Ln-NIT]n one-dimensional chains and the additional Cu ions are coordinated to the nitrogen atoms from the triazole rings of the radical ligands. The ferromagnetic couplings are observed between the coordinated NO group and Ln (III) ions. Ac magnetic susceptibilities indicate that the Ho derivatives displays frequency-dependent out-of-phase signals.

Three lanthanide–nitronyl nitroxide complexes: Syntheses, crystal structures, magnetic properties and fluorescence of selective sensing of Fe (III) ions

Three new lanthanide-nitronyl nitroxide radical complexes [Ln(hfac)3(NIT-biPh)2](Ln = Gd 1, Tb 2, Dy 3) (hfac = hexafluoroacetylacetonate; NIT-biPh = 2-([1,1′-biphenyl]-4-yl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) have been successfully synthesized and characterized. The X-ray crystal structure analysis revealed that three complexes are isomorphous, which exhibiting a mononuclear tri-spin structure. The central Ln (III) ion is eight-coordinated by six oxygen atoms from three hfac ligands and two oxygen atoms from the NO groups of two NIT-biPh ligands. The variable-temperature magnetic susceptibility indicated that ferromagnetic exchange interactions between the coordinated NO groups of radicals and Gd(III) ions, while antiferromagnetic exchange couplings between radicals within complex. Ac magnetic susceptibility exhibited no magnetic relaxation behavior at low temperature in compound 2. In addition, the luminescence properties of complex 2 show the characteristic emission peaks of Tb(III) ions and indicate an excellent fluorescent probe of recognizing Fe3+ ion.

Nitronyl nitroxide biradical-supported lanthanide hetero-spin compounds: Magnetic relaxation in Dy analogue

Based on nitronyl nitroxide biradical ligand (NITPhBrbis), two lanthanide coordination polymers, namely, [Ln(hfac)3(NITPhBrbis)]2·C7H16 (LnIII = Gd 1, Dy 2; hfac = hexafiuoroacetylacetonate; NITPhBrbis = 1-bromo-3,5-bis(1′-oxyl-3′-oxido-4′,4′,5′,5′-tetramethyl-4,5-hydro-1H-imidazol-2-yl)-benzene) have been isolated and characterized. Both compounds exhibit 2p-4f tri-spin mononuclear structure, in which NITPhBrbis molecule acts as a bidentate ligand with one coordinated lanthanide ion. DC magnetic susceptibility measurements, performed on Gd compound, reveal the presence of ferromagnetic coupling between GdIII center and the coordinated NO group, with J1 = 1.13 cm−1 following spin Hamiltonian H∧=-2J1(SGd∧·SRad1∧+SGd∧·SRad2∧)-2J2SRad1∧·SRad2∧. Moreover, Dy (2) complex presents slow magnetic relaxation process as confirmed by ac-susceptibility measurement.

Heterobimetallic MnII2DyIII2 cluster involving nitronyl nitroxide biradicals: Structure and magnetic properties

A novel nitronyl nitroxide biradical-based MnII2DyIII2 compound [Dy2Mn2(hfac)10(NITPhPybis)2] has been designed and assembled successfully, representing the first example of nitronyl nitroxide-MnII-LnIII compounds and expanding the realm of radical-metal based magnetic materials. DC magnetic susceptibility studies reveal the existence of ferromagnetic Dy-nitronyl nitroxide interaction and strong antiferromagnetic interaction between direct coordinated NO group and Mn(II) ion.

A novel nitronyl nitroxide and its copper complexes: Synthesis, structures and magnetic properties

A new nitronyl nitroxide NIT-5Im-3Py (1) and its copper complexes [Cu(hfac)2]4(NIT-5Im-3Py)2 (2), [Cu(hfac)2NIT-5Im-3Py]n (3) (NIT-5Im-3Py = 2-(5-(1-imidazole)-3-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; hfac = hexafluoroacetylacetonate) have been successfully synthesized and the molecular structures were elucidated by single-crystal X-ray structural analysis. In complex 2, NIT-3Py-5Im acts as bridge ligand to link four Cu(II) ions leading to {Cu4} complex while complex 3 displays a 1D-chain structure. Magnetic studies show that antiferromagnetic interactions dominate in complex 2, while there exist strong ferromagnetic interactions between Cu(II) and coordinated NO group in complex 3.

Structural and Magnetic Properties of 2p-3d-4f Hetero-Tri-Spin Chains Comprising [{Cu(hfac)2 -Radical}2 ] Dimers and Ln(hfac)3 (hfac=hexafluoroacetylacetonate).

A new family of 2p-3d-4f hetero-tri-spin complexes [Ln(hfac)3 {Cu(hfac)2 (NIT-3 PyPh)}2 ] (Ln=Gd (1), Tb (2), Dy (3), Ho (4); NIT-3 PyPh=2-[4-(3-pyridinylmethoxy)phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; hfac=hexafluoroacetylacetonate) have been synthesized. Four complexes possess a 1D chain structure in which two radical ligands join two Cu(hfac)2 molecules to form a [{Cu(hfac)2 -rad)}2 ] dimer cycle and the dimer rings are linked by Ln(hfac)3 units. Magnetic studies show that ferromagnetic exchange couplings exist between the coordinated NO groups of radical ligands and metal ions. Field-induced slow relaxation of the magnetization was observed in the Tb and Dy compounds.

Cu–Ln compounds based on nitronyl nitroxide radicals: synthesis, structure, and magnetic and fluorescence properties

Three series of nitronyl nitroxide radical 3d–4f compounds, namely, [Ln(hfac)3Cu(hfac)2NIT-5Br-3Py]n (LnIII = La (1), Pr (2)), [Ln(hfac)3Cu(hfac)2NIT-5Br-3Py] (LnIII = Gd (3), Tb (4), Dy (5)) and [Ln(hfac)3Cu(hfac)2(NIT-5Br-3Py)2]n (LnIII = Gd (6), Tb (7), Dy (8); NIT-5Br-3Py = 2-(5-bromo-3-pyridyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide; hfac = hexafluoroacetylacetonate) have been successfully obtained. Single crystal X-ray crystallographic analysis reveals that complexes 1 and 2 consist of 1D chains built up by Ln(hfac)3 units bridged by the radical ligands through their NO moieties and the additional Cu ions are coordinated to the nitrogen atoms of the radicals. Complexes 3–5 are rare hetero-binuclear Cu–Ln compounds bridged by the nitronyl nitroxide radicals while complexes 6–8 possess one-dimensional chain structures with a repeating [Cu–Rad–Ln–Rad] sequence. DC magnetic studies show ferromagnetic interaction between the LnIII ion and the coordinated NO group in compounds 3–8. Tb–Cu derivatives (complexes 4 and 7) display frequency dependent ac magnetic susceptibilities, indicating slow magnetic relaxation behavior. The room-temperature photoluminescence spectra of complexes 4 and 7 exhibit strong characteristic emissions in the visible region.

In vivo nitric oxide transfer of a physiological NO carrier, dinitrosyl dithiolato iron complex, to target complex

Dinitrosyl dithiolato iron complex (DNIC) has been identified as an endogenous NO carrier, yet in vivo mechanisms of NO donation remain undefined. Transnitrosylation, in which a coordinated NO group is transferred to another metal complex, has been observed in transition-metal-nitrosyl chemistry. In this study, we used three kinds of iron dithiocarbamate complexes (Fe-DTCs) as NO acceptors to elucidate in vivo transnitrosylation of diglutathionyl dinitrosyl iron complex [DNIC-(GS) 2]. Fe-DTCs were administered to mice after the injection of DNIC-(GS) 2 and electron paramagnetic resonance (EPR) spectra were measured both in the resected organs and in the upper abdomen of living mice. The spectral feature gradually changed from an initial DNIC-(GS) 2 signal to mononitrosyl iron dithiocarbamate one, suggesting that NO-Fe-DTC was formed through in vivo reaction of DNIC-(GS) 2 with Fe-DTC. The spectral results in in vitro and in vivo systems indicate that NO-Fe-DTCs can be formed not only by the transfer of coordinated NO-group(s) in DNIC-(GS) 2 but also by the abstraction of Fe-NO group in DNIC-(GS) 2 by free DTC ligands. Transnitrosylation proceeded more rapidly in blood than in liver and kidney; and more efficiently in kidney than in liver. Further, the ability to accept NO from DNIC was dependent on water-solubility of Fe-DTCs. Thus, in vivo transnitrosylation from DNIC to exogenous iron complex could be observed and this reaction was influenced by biological constituents and properties of iron complex. These results demonstrate that the transnitrosylation from DNIC to intrinsic NO acceptors like metalloproteins has a probable significance in in vivo NO transfer process.

SYNTHESES AND PROPERTIES OF NITROSYLS OF COBALT N'-AMIDINOISOUREAS

Abstract A number of nitrosyls of cobalt N'-amidinoisoureas of general formula [CoL2(NO)(H2O)], [CoL2'(NO)Cl]Cl and [CoL2'(NO)H2O]SO4 (where L = N'-amidinoisourea, L' = O-alkyl-N'-amidinoisourea) have been synthesized and characterized. Physico-chemical properties of these complexes suggest the above formulations and indicate the presence of comparatively high electron density on the coordinated NO group.

Reactions of (cyclopentadienyl)nitrosyldicarbonylmanganese cation with amines

The [(XC 5H 4)Mn(CO)(NO)L] + complexes react with primary alkylamines to give carboxamido complexes, where X = H, CH 3; L = CO, P(C 6H 5) 3. In the case of L = CO, the carboxamido complexes may be isolated, whereas with L = P(C 6H 5) 3 the reversibility of the reactions permits the isolation only of the starting materials when the solutions are evaporated to dryness. This diminished tendency to form carboxamido complexes is related to the decreased electron density on the carbonyl carbon going from L = CO to L = P(C 6H 5) 3. The presence of the coordinated NO group does not change the reactivity of the cationic complexes towards amines.

The chemistry of transition-metal nitrosyl compounds. Part VII. The preparation and study of some cationic nitrosyl complexes of iron

The cationic iron nitrosyl complexes [Fe(CO)2NOL2]PF6[L = P(OPh)3, P(OMe)3, PPh3, PMePh2, PMe2Ph, PEt3, P(C6H11)3, AsPh3 and 1/2dppe] have been prepared and some of their properties studied. Certain of these cations [L = P(OMe)3, PMePh2, and PMe2Ph] react with additional ligand (L) to produce the cationic species [Fe(CO)(NO)L3]+. With dppe the complex [Fe(CO)2NO(dppe)]PF6 yields the mononitrosyl cation [Fe(NO)(dppe)2]+; this cation has also been prepared from the reaction of the hydride FeHCl(dppe)2 with N-methyl-N-nitrosotoluene-p-sulphonamide in the presence of NaBPh4. The cations [Fe(CO)2NOL2]+ react with OMe– to produce the neutral carboxy-compounds Fe(CO)(NO)(L)2CO2Me (L = PPh3 or 1/2dppe). No evidence for nucleophilic addition of OMe– to the co-ordinated NO group in any of the cationic species has been found.