Experimental Evaluation of Mechanical Reliability of the Impeller Blade for Large Integrally Geared Compressors

Lectur

Pre-programmed self-assembly of polynuclear clusters

This perspective reviews our recent efforts towards the self-assembly of polynuclear clusters with ditopic and tritopic multidentate ligands HL1 (2-phenyl-4,5-bis{6-(3,5-dimethylpyrazol-1-yl)pyrid-2-yl}-1H-imidazole) and H2L2 (2,6-bis-[5-(2-pyridinyl)-1H-pyrazole-3-yl]pyridine), both of which are planar and rigid molecules. HL1 was found to be an excellent support for tetranuclear [Fe4] complexes, [FeII4(L1)4](BF4)4 ([FeII4]) and [FeIII2FeII2(L1)4](BF4)6 ([FeIII2FeII2]). The homovalent system was found to exhibit multistep spin crossover (SCO), while the mixed-valence [FeIII2FeII2] complex shows wavelength-dependent tuneable light-induced excited spin state trapping (LIESST). For H2L2, a variety of polynuclear complexes were obtained through complexation with different transition metal ions, allowing the isolation of rings, grids, and helix structures. The rigidity of the ligand, difference in its coordination sites, and affinity for different metal ions dictates its coordination behaviour. In this paper, we summarise these ligand pre-programmed self-assembled clusters and their diverse physical properties

Oxalate-bridged heterometallic chains with monocationic dabco derivatives

A series of bimetallic oxalate-bridged one-dimensional chains with monocationic dabco derivatives, ({R-dabco}[M(solv)2][Cr(ox)3]·n(solv)) (dabco = 1,4-diazabicyclo[2.2.2]octane, H2ox = oxalate; R = H, M = Co (1); R = H, M = Zn (2); R = Bu, M = Co (3); R = Bu, M = Zn (4)) were synthesized. All compounds have one-dimensional zig-zag chain structures with R-dabco cations located between chains. Cryomagnetic studies reveal that 1 and 3 showed intrachain ferromagnetic interactions between Co(II) and Cr(III) ions and metamagnetic behaviour due to interchain antiferromagnetic interactions. Permittivity measurements on compound 4 indicate specific paraelectronic relaxation behaviour originating from the rotational motion of the dabco alkyl substituent

A rectangular Ni-Fe cluster with unusual cyanide bridges

An asymmetric polycyanide iron complex, K2[Fe III(L1)(CN)4](MeOH) (HL1 = 2,2′-(1H-pyrazole-3,5- diyl)bis-pyridine), was synthesized and its complexation compatibility with nickel ions was examined. Two kinds of enantiomeric nickel-iron squares were obtained in the presence of a chiral bidentate capping ligand. The compounds display unusual cyanide bridge geometry and have ferromagnetic interactions between nickel and iron ions. © 2013 The Royal Society of Chemistry

Cyanide-Bridged Decanuclear Cobalt–Iron Cage

A cyanide-bridged decanuclear [Co6Fe4] cluster was synthesized by a one-pot reaction, and the magnetic properties and electronic configuration were investigated. The complex displayed thermally controlled electron-transfer-coupled spin transition (ETCST) behavior between CoIII low-spin–NC–FeII low-spin and CoII high-spin–NC–FeIII low-spin states, as confirmed by single-crystal X-ray, magnetic, and Mössbauer analyses

Cobalt complexes with redox-active anthraquinone-type ligands

Three anthraquinone-type multidentate ligands, HL1-3 (HL = 2-R-1H-anthra[1,2-d]imidazole6,11-dione, HL1; R = (2-pyridyl), HL2; R = (4,6-dimethyl-2-pyridyl), HL3; R = (6-methoxy-2pyridyl)), were prepared, and their complexation behaviour were investigated. Three bis-chelate cobalt complexes with the formula [CoII(L1-3)2].n(solv.) (1, 2, and 3 for HL1, HL2, and HL3, respectively), in which the ligands adopted tridentate binding modes, were synthesized and structurally characterized by single-crystal X-ray analyses. Electrochemical studies of 1-3 in CH2Cl2 reveal three reversible redox waves, assigned to ligand and cobalt-centred processes. Further complexes were obtained in which HL1 adopted a bidentate binding mode, stabilising the mono-chelate [CoII(HL1)(NO3)2(DMF)2] (4) species and tris-chelate [CoIII(L1)3] (5) complex in which the cobalt ion was in its 3+ state. The electrochemical properties of complex 5 were investigated in DMF, and the Co(II)/Co(III) redox couple was found to have negatively shifted compared to that of complex 1, while the ligand-based processes became irreversible. Tridentate chelation is found to stabilise the anthraquinone ligands and unlocks their redox multi-stability

Structural, Magnetic, and Electrochemical Characterization of Iron(III) and Cobalt Complexes with Penta-N3O2-dentate Ligands

Six new mononuclear [FeIII(LBr,Cl)X]-complexes (LBr,Cl is the dianionic penta-N3O2-dentate Schiff base ligand N,N′-bis(2’-hydroxy-3-bromo-5-chlorobenzylidene)-1,6-diamino-3-azahexane; X: Cl−, N3−, NCO−, NCS−, NCSe−, CN−) were synthesized and their structures, magnetic and electrochemical properties studied. Structure analysis and magnetic measurements showed that [FeIII(LBr,Cl)CN] is in the low spin state and the other five complexes are in high spin states. Furthermore, the trinuclear mixed valent cobalt complex {[CoIII(LH,H)CN]2[CoII(1-methylimidazole)3(H2O)]} was prepared and its magnetic behavior studied. © 2021 The Authors. European Journal of Inorganic Chemistry published by Wiley-VCH Gmb

Two-electron redox-active tricyano iron(II) complex with 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine as a building block for coordination polymers

A new tricyano iron(II) building unit, [{K(H2O)4}{FeII(CN)3(L)}]·3H2O (1), was synthesized by the reaction of Moor\u27s salts with 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (L) as a capping ligand. X-ray structural analysis reveals that the mononuclear iron(II) tricyano complex consists of one ligand and three cyanide groups, with K+ ions coordinated between neighboring units to form a one-dimensional chain network structure. 1 shows two reversible redox waves at +0.713 and −0.849 V vs. SCE, which are assigned as Fe(II)/Fe(III) and L/L˙− processes, respectively. One-dimensional 4,2-ribbon chain type coordination polymers, [MII(H2O)2{FeII(CN)3(L)}2]·6H2O (M = Fe (2) and Mn (3)), were synthesized by using 1 as a building unit. Cryomagnetic studies reveals that 2 and 3 show paramagnetic behaviour of S = 2 and 5/2, respectively. On the other hand, reaction of 1 and Gd(NO3)3·6H2O forms another one-dimensional chain, [GdIII(NO3)2(H2O)3{FeII(CN)3(L)}]·0.5H2O·2CH3OH (4), showing S = 7/2 paramagnetic behaviour

Experimental Evaluation of Mechanical Reliability of the Impeller Blade for Large Integrally Geared Compressors

Lectur