Tuning the photoluminescence of condensed-phase cyclic trinuclear Au(I) complexes through control of their aggregated structures by external stimuli.

A series of new cyclic trinuclear Au(I) complexes with alkoxy side chains of various lengths were synthesized as photoluminescence materials. None of the complexes emitted luminescence in solution; however, some showed photoluminescence in the crystalline phase. Single crystal X-ray structural analyses revealed that an intermolecular interaction between two Au atoms (aurophilic interaction) existed only in the emissive complexes, which formed molecular aggregates in the crystal.

B3LYP study on reduction mechanisms from O2 to H2O at the catalytic sites of fully reduced and mixed-valence bovine cytochrome c oxidases.

Reduction mechanisms of oxygen molecule to water molecules in the fully reduced (FR) and mixed-valence (MV) bovine cytochrome c oxidases (CcO) have been systematically examined based on the B3LYP calculations. The catalytic cycle using four electrons and four protons has been also shown consistently. The MV CcO catalyses reduction to produce one water molecule, while the FR CcO catalyses to produce two water molecules.

Theoretical study of electronic structures of [(H2O)3(O-)Mn(mu-oxo)2Mn(OH2)4]q+ (q = 2 or 3) with Mn-O bond.

Molecular geometries and electronic structures of manganese binuclear complexes, [(H(2)O)(3)(O-)Mn(bis-mu-oxo-O(2))Mn(OH(2))(4)](q+) (q = 2 or 3), which are model complexes of the S(3) state in the Kok cycle of OEC, were examined using hybrid density functional theory and broken symmetry method. The complexes of q = 2 and 3, which have a Mn-O bond, correspond to those derived from Mn(2)(II,III) and Mn(2)(III,III) at the S(0) state of the Kok cycle. The conformers with the Mn-O bond axial to the Mn(2)O(2) core are lower in energy than those with the equatorial Mn-O bond.

Mechanism on two-electron oxidation of ubiquinol at the Qp site in cytochrome bc1 complex: B3LYP study with broken symmetry.

The molecular and electronic structures of the Rieske iron-sulfur [2Fe-2S] cluster with an imidazolate and imidazole were investigated by using usual unrestricted and broken symmetry B3LYP methods for the highest and lowest spin states, respectively. The electronic structures of the lowest spin states were determined by the spin contaminations and natural orbital analyses. It was shown that the spin contamination presents the number of pairs of the antiferromagnetic spin couplings.

Theoretical study on electronic structures of FeOO, FeOOH, FeO(H2O), and FeO in hemes: as intermediate models of dioxygen reduction in cytochrome c oxidase.

The electronic structures of heme-dioxygen complexes have been studied as intermediate models of dioxygen reduction mechanism catalyzed by the mixed valence (MV) and fully reduced (FR) cytochrome c oxidase (CcO). Dioxygen, protons and electrons were sequentially added to the heme along the proposed reaction path for the O(2) reduction mechanism. The electronic structures of [FeOO], [FeOO](-), [FeOOH](+), [FeOOH], [Fe=O, H(2)O](+), [Fe=O](+) and [Fe=O] were thoroughly investigated by using the unrestricted hybrid exchange-correlation functional B3LYP method.

Density functional study on geometrical features and electronic structures of di-mu-oxo-bridged [Mn2O2(H2O)8]q+ with Mn(II), Mn(III), and Mn(IV).

We report the geometrical features and electronic structures of di-mu-oxo-bridged Mn-Mn binuclear complexes with H2O ligands [Mn2O2(H2O)8]q+ in the iso- and mixed-valence oxidation states. All of the combinations among Mn(II), Mn(III), and Mn(IV) ions are considered the oxidation states of the Mn-Mn center, and the changes in molecular structure induced by the different electron configurations of Mn-based orbitals are investigated in relation to the oxygen-evolving complex (OEC) of photosystem II. The stable geometries of complexes are determined by using the hybrid-type density functional theory for both of the highest- and lowest-spin couplings between Mn sites, and the lowest-spin-coupled states are energetically more favorable than the highest-spin-coupled states except in the case of the complexes with the Mn(II) ion.

Highly activated vinyl hydrogen in a significantly twisted styrene.

The novel example of a vinylic hydrogen more reactive than a benzylic hydrogen was found by treatment of a twisted styrene derivative with a strong base followed by D(2)O quenching. In this paper, the full details of the examples of the highly activated vinyl hydrogens in twisted styrene derivatives are described, with a discussion on the correlation between the reactivity of the vinyl hydrogens and the magnitude of the twist. The highly reactive vinyl hydrogens could be rationalized by considering the novel orbital interaction between the pi(*) orbital of the benzene ring and the pi(*) orbital of the vinylic C-H bond in the twisted styrene derivatives.

Elimination-addition mechanism for nucleophilic substitution reaction of cyclohexenyl iodonium salts and regioselectivity of nucleophilic addition to the cyclohexyne intermediate.

The reaction of 4-substituted cyclohex-1-enyl(phenyl)iodonium tetrafluoroborate with tetrabutylammonium acetate gives both the ipso and cine acetate-substitution products in aprotic solvents. The isomeric 5-substituted iodonium salt also gives the same mixture of the isomeric acetate products. The reaction is best explained by an elimination-addition mechanism with 4-substituted cyclohexyne as a common intermediate.

Ab initio molecular orbital study on the G-selectivity of GGG triplet in copper(I)-mediated one-electron oxidation.

The G-selectivity for Cu(I)-mediated one-electron oxidation of 5'-TG(1)G(2)G(3)-3' and 5'-CG(1)G(2)G(3)-3' has been examined by ab initio molecular orbital calculations. It was confirmed that G(1) is selectively damaged by Cu(I) ion for both 5'-TG(1)G(2)G(3)-3' and 5'-CG(1)G(2)G(3)-3', being good agreement with experimental results. The Cu(I)-mediated G(1)-selectivity is primarily due to the stability of the Cu(I)-coordinated complex, [-XG(1)G(2)G(3)-,-Cu(I)(H(2)O)(3)](+).

Theoretical studies of magnetic interactions in Mn(II)(hfac)(2)[di(4-pyridyl)phenylcarbene] and Cu(II)(hfac)(2)[di(4-pyridyl)phenylcarbene].

Bis(hexafluoroacetylacetonato(hfac))manganese(II) coordinated with di(4-pyridyl)phenylcarbene, Mn(II)(hfac)(2)[di(4-pyridyl)phenylcarbene] (1a) and its copper analogue Cu(II)(hfac)(2)[di(4-pyridyl)phenylcarbene] (2a) have attracted great interest from the viewpoint of photoinduced magnetism. The complexes 1a and 2a are regarded as the new d-pi-p conjugated systems containing transition metal ion and carbene as spin sources. The magnetic measurements demonstrated antiferromagnetic and ferromagnetic effective exchange interactions for 1a and 2a, respectively.