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The abilities of the (HPO 3 ) 2− and (SeO 3 ) 2− anions as structure building units and as spin exchange paths between magnetic ions were investigated by preparing and analyzing the isostructural Fe 2 (SeO 3 ) 3 and Fe 2 (HPO 3 ) 3 . In both compounds, the face-sharing Fe 2 O 9 dimers are interconnected into chains by the (HPO 3 ) 2− and (SeO 3 ) 2− anions. The (HPO 3 ) 2− is the structural counterpart of the Se electron lone pair of (SeO 3 ) 2− due to the weak hydride character of the terminal hydrogen. However, they differ considerably as spin exchange paths between magnetic cations. Both compounds exhibit an effective magnetic dimer behavior, unexpectedly arising from the interdimer FeO•••OFe exchange along the chain, but weaker in Fe 2 (HPO 3 ) 3 by a factor of ∼3. It is consistent with the general tendencies of the phosphite anions to act as a weak magnetic mediator, which is caused by the through-bond effect of the P 3+ ion in the FeO•••P 3+ •••OFe exchange path, much weaker than in the selenite phase in absence of P 3+ d contribution. Reasons for stronger exchanges through phosphates or sulfates are also discussed.

Recently it was discovered that the iron coordination complex L(N4)Fe(II)(OTf)(2) (1) (L(N4) = neutral tetraazadendate ligand and OTf = OSO(2)CF(3)) and its analogues are efficient water oxidizing catalysts (WOCs) in aqueous acidic solution with excess amount of ceric(IV) ammonium nitrate (CAN), [Ce(IV)(NO(3))(6)](NH(4))(2), as sacrificial oxidants. The probable mechanism of water oxidation by these catalysts was explored on the basis of density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations for 1 as a representative WOC. We examined the conversion of 1 to the resting intermediate [L(N4)Fe(IV)(O)(OH(2))](2+) [2(IV)] as well as two catalytic cycles involving 2(IV): one proposed by Fillol et al. [Nat. Chem. 2011, 3, 1] in which the Fe oxidation states of the intermediate species vary from +2 to +5, and the alternative cycle in which they remain constant at +4. In addition, we investigated the role of the sacrificial oxidant CAN in driving the catalytic cycle. Our DFT and TD-DFT calculations confirm the experimental observation that 2(IV) is the resting species, and indicate that the catalytic cycle in which the Fe oxidation states of the intermediate species remain at +4 is energetically more favorable.

High-spin Fe 2+ , Fe + and Co 2+ ions at linear two-coordination sites exhibit uniaxial magnetism. In the one-electron picture, the uniaxial magnetism of the Fe 2+ ion is explained, while those of the Fe + and Co 2+ ions are not, if the d-state split pattern is 1e < 2e < 1a. The opposite is true if the d-state split pattern is 1a < 1e < 2e. We resolved this conceptual dilemma by evaluating the relative stabilities for the various L states of [a]

Se4+ and N3− ions were used as codopants to enhance the photocatalytic activity of TiO2 under sunlight irradiation. The Se/N codoped photocatalysts were prepared through a simple wet-impregnation method followed by heat treatment using SeCl4 and urea as the dopant sources. The prepared photocatalysts were well characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-diffuse reflectance spectroscopy (UV-DRS), scanning electron microscopy (SEM) and Raman spectroscopy. The codoped samples showed photoabsorption in the visible light range from 430 nm extending up to 580 nm. The photocatalytic activity of the Se/N codoped photocatalysts was evaluated by degradation of 4-nitrophenol (4-NP). The degradation of 4-NP was highly increased for the Se/N codoped samples compared to the undoped and single doped samples under both UV-A and sunlight irradiation. Aiming to determine the electronic structure and dopant locations, quantum chemical modeling of the undoped and Se/N codoped anatase clusters was performed using Density Functional Theory (DFT) calculations with the hybrid functional (B3LYP) and double-zeta (LanL2DZ) basis set. The results revealed that Se/N codoping of TiO2 reduces the band gap due to mixing of N2p with O2p orbitals in the valence band and also introduces additional electronic states originating from Se3p orbitals in the band gap.