8 research outputs found
Inverted-sandwich-type and open-lantern-type dinuclear transition metal complexes: theoretical study of chemical bonds by electronic stress tensor
We study the electronic structure of two types of transition metal complexes, the inverted-sandwich-type and open-lantern-type, by the electronic stress tensor. In particular, the bond order bε measured by the energy density which is defined from the electronic stress tensor is studied and compared with the conventional MO-based bond order. We also examine the patterns found in the largest eigenvalue of the stress tensor and corresponding eigenvector field, the “spindle structure” and “pseudo-spindle structure”. As for the inverted-sandwich-type complex, our bond order bε calculation shows that relative strength of the metal-benzene bond among V, Cr, and Mn complexes is V > Cr > Mn, which is consistent with the MO-based bond order. As for the open-lantern-type complex, we find that our energy density-based bond order can properly describe the relative strength of Cr–Cr and Mo–Mo bonds by the surface integration of the energy density over the “Lagrange surface” which can take into account the spatial extent of the orbitals
Bonding Nature of Open-Lantern-type Dinuclear Cr(II) Complexes. Theoretical Study with the MRMP2 Method
Inverted Sandwich Type Dinuclear Chromium(I) Complex and Its Analogues of Scandium(I), Titanium(I), Vanadium(I), Manganese(I), and Iron(I): Theoretical Study of Electronic Structure and Bonding Nature
Theoretical Study of Inverted Sandwich Type Complexes of 4d Transition Metal Elements: Interesting Similarities to and Differences from 3d Transition Metal Complexes
Inverted sandwich type complexes (ISTCs) of 4d metals,
(μ-η<sup>6</sup>:η<sup>6</sup>-C<sub>6</sub>H<sub>6</sub>)[M(DDP)]<sub>2</sub> (DDPH = 2-{(2,6-diisopropylphenyl)amino}-4-{(2,6-diisopropylphenyl)imino}pent-2-ene;
M = Y, Zr, Nb, Mo, and Tc), were investigated with density functional
theory (DFT) and MRMP2 methods, where a model ligand AIP (AIPH = (<i>Z</i>)-1-amino-3-imino-prop-1-ene) was mainly employed. When
going to Nb (group V) from Y (group III) in the periodic table, the
spin multiplicity of the ground state increases in the order singlet,
triplet, and quintet for M = Y, Zr, and Nb, respectively, like 3d
ISTCs reported recently. This is interpreted with orbital diagram
and number of d electrons. However, the spin multiplicity decreases
to either singlet or triplet in ISTC of Mo (group VI) and to triplet
in ISTC of Tc (group VII), where MRMP2 method is employed because
the DFT method is not useful here. These spin multiplicities are much
lower than the septet of ISTC of Cr and the nonet of that of Mn. When
going from 3d to 4d, the position providing the maximum spin multiplicity
shifts to group V from group VII. These differences arise from the
size of the 4d orbital. Because of the larger size of the 4d orbital,
the energy splitting between two d<sub>δ</sub> orbitals of M(AIP)
and that between the d<sub>δ</sub> and d<sub>π</sub> orbitals
are larger in the 4d complex than in the 3d complex. Thus, when occupation
on the d<sub>δ</sub> orbital starts, the low spin state becomes
ground state, which occurs at group VI. Hence, the ISTC of Nb (group
V) exhibits the maximum spin multiplicity
Theoretical Study of Inverted Sandwich Type Complexes of 4d Transition Metal Elements: Interesting Similarities to and Differences from 3d Transition Metal Complexes
High-affinity monoclonal IgA regulates gut microbiota and prevents colitis in mice
Immunoglobulin A (IgA) is the main antibody isotype secreted into the intestinal lumen. IgA plays a critical role in the defence against pathogens and in the maintenance of intestinal homeostasis. However, how secreted IgA regulates gut microbiota is not completely understood. In this study, we isolated monoclonal IgA antibodies from the small intestine of healthy mouse. As a candidate for an efficient gut microbiota modulator, we selected a W27 IgA, which binds to multiple bacteria, but not beneficial ones such as Lactobacillus casei. W27 could suppress the cell growth of Escherichia coli but not L. casei in vitro, indicating an ability to improve the intestinal environment. Indeed W27 oral treatment could modulate gut microbiota composition and have a therapeutic effect on both lymphoproliferative disease and colitis models in mice. Thus, W27 IgA oral treatment is a potential remedy for inflammatory bowel disease, acting through restoration of host–microbial symbiosis