Konstantin Pokhodnya

Formation of Ni[C4(CN)8] from the reaction of Ni(COD)2 (COD = 1,5-cyclooctadiene) with TCNE in THF

The dissolution of Ni(COD)2 (COD = 1,5-cyclooctadiene) into dichloromethane leads to decomposition and formation of a room temperature magnetic material, whereas the reaction of Ni(COD)2 and tetracyanoethylene (TCNE) in THF forms paramagnetic materials including NiII[C4(CN)8](THF)2·xTHF. These results are discussed in context with a recent report of a room temperature magnet based upon the reaction of Ni(COD)2 and TCNE in dichloromethane.

Toward the Mechanism of Perchlorinated Cyclopentasilane (Si5Cl10) Ring Flattening in the [Si5Cl10·2Cl]2– Dianion

We report the detailed computational study of flattening of the puckered Si5 ring by suppression of the pseudo-Jahn-Teller (PJT) effect through coordination of two Cl- anions to the molecule forming an inverse sandwich dianion [Si5Cl10·2Cl]2- complex. The PJT effect that causes nonplanarity of the Si5Cl10 structure (Cs) results from vibronic coupling of pairs of occupied molecular orbitals (OMOs) and unoccupied molecular orbitals (UMOs). It was shown that filling the intervenient molecular orbitals of puckered Si5Cl10 with valent electron pairs of Cl- donors suppresses the PJT effect, with the Si5 ring becoming planar (D5h) upon complex formation. In this paper, the stabilization energy E(2) associated with donor-acceptor charge transfer (delocalization) was estimated using NBO analysis for all studied inverse sandwich compounds [Si5Cl10·2X]2- (where X = F, Cl, Br). It was found that the polarizability of the donor ion might significantly affect the stabilization energy value and should be taken into account when choosing the ligands suitable for forming Si-based one-dimensional compounds and other nanoscale materials.

Chemical bonding and magnetic exchange in two-dimensional [M(TCNE)(NCMe)2]X (M = Fe, Mn; X = FeCl4, SbF6) magnets: A pressure study

Pressure-dependent X-ray diffraction studies reveal the bulk modulus and compression anisotropy of the 2D magnet [Mn(TCNE)(NCMe)(2)]SbF(6). The Raman response of this and the similar [Fe(TCNE)(NCMe)(2)]FeCl(4) layered magnet, shows that the evolution of the a(g) ν(C=C) frequency correlates well with the magnetic exchange and T(c) variations of these materials under pressure. There is a significantly more complex correlation between the a(g) ν(C≡N) frequency and T(c) despite the fact that some unpaired π* electron density (~0.125 e) is localized on each of TCNE nitrile N≡C group. The shortening of the M-NC bond with pressure (<0.5 GPa) does not result in a T(c) increase, which suggests a more complex bond length magnetic exchange relationship.

Dielectric properties of BaMg1∕3Nb2∕3O3 doped Ba0.45Sr0.55Tio3 thin films for tunable microwave applications

Ba(Mg1∕3Nb2∕3)O3 (BMN) doped and undoped Ba0.45Sr0.55TiO3 (BST) thin films were deposited via radio frequency magnetron sputtering on Pt/TiO2/SiO2/Al2O3 substrates. The surface morphology and chemical state analyses of the films have shown that the BMN doped BST film has a smoother surface with reduced oxygen vacancy, resulting in an improved insulating properties of the BST film. Dielectric tunability, loss, and leakage current (LC) of the undoped and BMN doped BST thin films were studied. The BMN dopant has remarkably reduced the dielectric loss (∼38%) with no significant effect on the tunability of the BST film, leading to an increase in figure of merit (FOM). This is attributed to the opposing behavior of large Mg2+ whose detrimental effect on tunability is partially compensated by small Nb5+ as the two substitute Ti4+ in the BST. The coupling between MgTi″ and VO•• charged defects suppresses the dielectric loss in the film by cutting electrons from hopping between Ti ions. The LC of the films was inv...