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A theoretical method to extract structural information on spin-exchange-coupled manganese tetramers from the EPR spectroscopy data is presented. This method has been applied to two EPR data, i.e. the ground-state spin (S = 1/2) and the first excitation energy (30—37 cm−1), for the S2-state Mn tetramer in the photosynthetic oxygen-evolving complex, which exhibits a “g = 2 multiline” EPR signal. Based on the EXAFS data and the manganese chemistry, a simplified model spin Hamiltonian to describe the S2-state Mn cluster will be presented, such that two spin-exchange interactions due to 2.7—2.8 A and/or 3.2—3.5 A Mn–Mn bonds can vary from weak to strong coupling, sensitively, depending upon the bridge structure, except for a strong-antiferromagnetic interaction due to a 2.7 A Mn(III)–Mn(IV) bond and the other weak ones. By computer-search of the possible spin-exchange structures with respect to these two parametric interactions, it was found that (1) a dimer of di-μ2-oxo bridged Mn dimers, a propeller-type tet...

Studies of the crystal structures and formation of a charge-transfer (CT) complex proved that 2,2′-bi-1H-imidazole (H2BIM0) forms a new system concerned with the interplay of proton-transfer (PT) and electron-transfer (or charge-transfer (CT)) interactions. X-Ray crystal analyses of newly isolated species, 2-(2-1H-imidazolyl)-1H-imidazolium (H3BIM+) and 2,2′-bi-1H-imidazolium (H4BIM2+), revealed the formation of strong hydrogen bonds along the side-by-side direction of the molecular plane. CT complexes of H3BIM+ and H4BIM2+ with the 7,7,8,8-tetracyanoquinodimethane derivatives (TCNQs) were synthesized by a method metathesis, and the crystal structure of (H3BIM+)2(TCNQ−)2(TCNQ0) was determined. During CT complex formation, the initial simple protonated states of [H3BIM+] or [H4BIM2+] changed to different ones, for example, [H4BIM2+]x[H3BIM+]1−x, [H3BIM+]x[H2BIM0]1−x, and H2BIM0. According to the protonated states of the H2BIM system, the formal charge of the TCNQs in the CT complexes varies from completely...

Trifluoroacetaldehyde azine (TFAcAz) was prepared and its reactivity was investigated. TFAcAz is readily attacked by nucleophiles such as trialkylamines, methanol, and water. The structures of the products were studied by 1H, 13C, and 19F NMR, IR, Raman, and EI–mass spectroscopies and X–ray crystallographic analysis. A cyclic dimer containing a 1,4-dihydro-1,2,4,5-tetrazine ring was obtained by the reactions of TFAcAz with trialkylamines. 1,2-Adducts were found to be produced by the reactions of TFAcAz with methanol and with water.

A dimer-of-di(μ-oxo)manganese(III)manganese(IV)-dimers with two coordinated water molecules, [{Mn2(tmdp)(O)2(H2O)}2](CF3SO3)4·6H2O (1), was prepared, where Htmdp is 1,5-bis[bis(2-pyridylmethyl)amino]-3-pentanol. Crystal structure of 1 was determined by X-ray structure analysis. 1 crystallizes in triclinic space group, with a = 16.543(1), b = 19.097(2), c = 13.393(1) A, α = 94.450(7)°, β = 90.698(6)°, γ = 84.997(7)°, V = 4202.4(6) A3, and Z = 2. The complex cation consists of two di(μ-oxo)manganese(III)manganese(IV) dimers which are linked by two tmdps and hydrogen bonding network between two coordinated water molecules and two alkoxo groups to form a dimer-of-dimers with a bilayered structure with dimer-dimer separation of 5.9 A. The Mn–Mn separations are 2.644(2)—2.651(2) A. Magnetism of 1 was well interpreted in terms of the model based on two kinds of the exchange interactions between Mn(III) and Mn(IV); the intradimer interaction (J1 = −145 cm−1) through di(μ-oxo) bridges and the interdimer interactio...

An oxomolybdenum(V) complex with two chelating ligands of alkane- and arenethiolate parts, (NEt4)[MoVO(α,2-toluenedithiolato)2], was prepared and characterized by visible, ESR, IR, and Raman spectroscopies. Four distinct ligand-to-metal charge transfer absorption bands were observed in visible region. The complex crystallizes in the space group P21 with a=9.535(2), b=16.582(9), c=8.085(1) A, β=90.757(4)°, V=1278.3(8) A3, Z=2, and dcalcd=1.431 g cm−3. The structure was solved and refinement based on 2102 reflections converged at R=0.089 and Rw=0.100. The complex takes an apical oxo and trans bis(α,2-toluenedithiolato) structure with a distorted MoOS4 core from a tetragonal-pyramidal geometry.

The conformation and molecular packing of ditetradecyldimethylammonium bromide monohydrate (2C14N+2C1Br−·H2O), C30H62NBr·H2O, has been determined by the X-ray diffraction method. The crystals are triclinic with the space group P\bar1, Z=2, a=2.9827(9), b=0.7847(3), c=0.7480(3) nm, α=104.69(4), β=90.64(7), and γ=90.84(6)°. The structure was determined by direct methods and refined by the least-squares procedure: R=0.07 (Rw=0.07) for 3335 observed reflections. Two amphiphile molecules of the unit cell are related by centrosymmetry and pack tail to tail in a bilayer structure. The hydrocarbon chains tilt about 45° with respect to the bilayer normal. There are statistically four water molecules with half occupancies in a unit cell. Water molecules and bromide anions make hydrogen-bonding networks along the c-axis in the hydrophilic layer. The above molecular and crystal structure of 2C14N+2C1Br−·H2O was quite similar to those of 2C18N+2C1Br−·H2O.