Synthetic, structural, spectroscopic and theoretical study of a Mn(III)-Cu(II) dimer containing a Jahn-Teller compressed Mn ion

The heterobimetallic complex [Cu(II)Mn(III)(L)(2)(py)(4)](ClO4)center dot EtOH (1) built using the pro-ligand 2,2'-biphenol (LH2), contains a rare example of a Jahn-Teller compressed Mn(III) centre. Dc magnetic susceptibility measurements on 1 reveal a strong antiferromagnetic exchange between the Cu(II) and Mn(III) ions mediated through the phenolate O-atoms (J = -33.4 cm(-1)), with magnetisation measurements at low temperatures and high fields suggesting significant anisotropy. Simulations of high-field and high frequency powder EPR data suggest a single-ion anisotropy D-Mn(III) = +4.45 cm(-1). DFT calculations also yield an antiferromagnetic exchange for 1, though the magnitude is overestimated (J(DFT) = -71 cm(-1)). Calculations reveal that the antiferromagnetic interaction essentially stems from the Mn(d(x2-y2))-Cu(d(x2-y2)) interaction. The computed single-ion anisotropy and cluster anisotropy also correlates well with experiment. A larger cluster anisotropy for the S = 3/2 state compared to the single-ion anisotropy of Mn(III) is rationalised on the basis of orbital mixing and various contributions that arise due to the spin-orbit interaction

The role of inducible nitric oxide synthase for interstitial remodeling of alveolar septa in surfactant protein D-deficient mice

Surfactant protein D (SP-D) modulates the lung's immune system. Its absence leads to NOS2-independent alveolar lipoproteinosis and NOS2-dependent chronic inflammation, which is critical for early emphysematous remodeling. With aging, SP-D knockout mice develop an additional interstitial fibrotic component. We hypothesize that this age-related interstitial septal wall remodeling is mediated by NOS2. Using invasive pulmonary function testing such as the forced oscillation technique and quasistatic pressure-volume perturbation and design-based stereology, we compared 29-wk-old SP-D knockout (Sftpd(-/-)) mice, SP-D/NOS2 double-knockout (DiNOS) mice, and wild-type mice (WT). Structural changes, including alveolar epithelial surface area, distribution of septal wall thickness, and volumes of septal wall components (alveolar epithelium, interstitial tissue, and endothelium) were quantified. Twenty-nine-week-old Sftpd(-/-) mice had preserved lung mechanics at the organ level, whereas elastance was increased in DiNOS. Airspace enlargement and loss of surface area of alveolar epithelium coexist with increased septal wall thickness in Sftpd(-/-) mice. These changes were reduced in DiNOS, and compared with Sftpd(-/-) mice a decrease in volumes of interstitial tissue and alveolar epithelium was found. To understand the effects of lung pathology on measured lung mechanics, structural data were used to inform a computational model, simulating lung mechanics as a function of airspace derecruitment, septal wall destruction (loss of surface area), and septal wall thickening. In conclusion, NOS2 mediates remodeling of septal walls, resulting in deposition of interstitial tissue in Sftpd(-/-). Forward modeling linking structure and lung mechanics describes the complex mechanical properties by parenchymatous destruction (emphysema), interstitial remodeling (septal wall thickening), and altered recruitability of acinar airspaces

Bulking up: hexanuclear oximato Fe(III) complexes surrounded by sterically demanding co-ligands

Despite their inherent steric bulk, a combination of 2-hydroxy-1- naphthaldoxime (L1H2) with polyphenolic carboxylate ligands (1-Naphthoate, 9-Anthracene carboxylate) aid the construction and stabilisation of hexanuclear arrays of Fe(III) ions in the form of [Fe(III) 6O2(L1)2(O2C-R) 10(H2O)2]·8MeCN (R = Naphth-(C 10H8) (1); R = Anthra-(C14H9) (2)). Likewise, the sterically hindered ligand 3,5-di-tert-butyl-salicylaldoxime (L2H2) is able to aid the self-assembly of the tetranuclear, cubane-like species [Fe(III)4(L2) 4(MeOH)4(Cl)4] (3). Magnetic susceptibility studies carried out on 1 and 3 reveal antiferromagnetic exchange between the Fe(III) metal centres affording S = 0 ground spin states in both cases. © 2014 Elsevier B.V. All rights reserved.Irish Research Council for Science and Technology (IRCSET Embark Program (EH) and the EPSRC.Published versio

Turning on Single-Molecule Magnet Behavior in a Linear {Mn3} Compound

The synthesis, structure, and magnetic properties are reported for a new manganese compound with a mixed-valent {Mn3} core arranged in a linear fashion. The previously reported complex 1, [MnIV3(dpo)6]*2MeCN, where H2dpo is (E)-1-hydroxy-1,1-diphenylpropan-2-one oxime, served as a starting point for the isolation of a {Mn3} compound with an analogous core arrangement through the reaction of Mn-(OAc)2*4H2O, H3oxol ((E)-2,5-dihydroxy-2,5-dimethylhexan-3-one oxime), and NaOH in MeOH and MeCN. By using these reaction conditions, compound 2, Na[MnIV 2MnIII(Hoxol)6]n*MeOH*H2O, was successfully isolated revealing a central MnIII ion thereby introducing structural and magnetic anisotropy to the system. The structure of 2 reveals linear trinuclear MnIV−MnIII−MnIV units connected through Na+ ions forming a linear one-dimensional coordination polymer. The Jahn−Teller axes of each trinuclear unit are aligned parallel within the same chain and form a 75° angle between the two symmetry related chains. Magnetic susceptibility measurements of 1 and 2 in the temperature range 1.9−300 K reveal that only the reduced compound, 2, is a single-molecule magnet (SMM) largely due to the anisotropy introduced by the Jahn−Teller distortions on the MnIII ions, which effectively induce this magnet behavior. Weak antiferromagnetic interactions along the chains through the Na+ cations lead to a modulation of the intrinsic properties of the MnIV−MnIII−MnIV SMMs