High‐Resolution 3D Proton MRI of Hyperpolarized Gas Enabled by Parahydrogen and Rh/TiO2 Heterogeneous Catalyst

Several supported metal catalysts were synthesized, characterized, and tested in heterogeneous hydrogenation of propene with parahydrogen to maximize nuclear spin hyperpolarization of propane gas using parahydrogen induced polarization (PHIP). The Rh/TiO₂ catalyst with a metal particle size of 1.6 nm was found to be the most active and effective in the pairwise hydrogen addition and robust, demonstrating reproducible results with multiple hydrogenation experiments and stability for ≥1.5 years. 3D ¹H magnetic resonance imaging (MRI) of 1 % hyperpolarized flowing gas with microscale spatial resolution (625×625×625 μm³) and large imaging matrix (128×128×32) was demonstrated by using a preclinical 4.7 T scanner and 17.4 s imaging scan time.     

Heterospin Single‐Molecule Magnets Based on Terbium Ions and TCNQF4 Radicals: Interplay between Single‐Molecule Magnet and Phonon Bottleneck Phenomena Investigated by Dilution Studies

A series of isostructural compounds with formula [M(TCNQF₄)₂(H₂O)₆]TCNQF₄ ? 3 H₂O (M=Tb ( 1 ), Y ( 2 ), Y:Tb (74:26) ( 3 ), and Y:Tb (97:3) ( 4 ); TCNQF₄= tetrafluorotetracyanoquinodimethane) were prepared and their magnetic properties investigated. Compounds 1 , 3 , and 4 show the beginning of a frequency‐dependent out‐of‐phase ac signal, and decreasing intensity of the signal with decreased concentration of Tb^III ions in the diluted samples is observed. No out‐of‐phase signal was observed for 2 , an indication that the behavior of 1 , 3 , and 4 is indicative of slow paramagnetic relaxation of Tb^III ions in the samples. A more detailed micro‐SQUID study at low temperature revealed an interplay between single‐molecule magnetic (SMM) behavior and a phonon bottleneck (PB) effect, and that these properties depend on the concentration of diamagnetic yttrium ions. A combination of SMM and PB phenomena was found for 1 , whereby the PB effect increases with increasing dilution until eventually a pure PB effect is observed for 2 . The PB behavior is interpreted as being due to the presence of a “sea of organic S=1/2 radicals” from the TCNQF₄ radicals in these compounds. The present data underscore the fact that the presence of an out‐of‐phase ac signal may not, in fact, be caused by SMM behavior, particularly when magnetic metal ions are combined with organic radical ligands such as those found in the organocyanide family.     

Machine with inertial excitation of dynamic loads for testing rigid polymers for fatigue bending

A machine design is described and results given for testing specimens of polymethyl methacrylate, treated in different conditions.Lenin Komsomol Riga Institute of Civil-Aviation Engineers. Translated from from Mekhanika Polimerov, No. 5, pp. 952–955, September–October, 1973.     

A high spin molecular square based on square pyramidal Co(II) and tetrahedral Mn(II) centers: [{MnIICl2}2{CoII(triphos)(CN)2}2

A high spin molecular square of square pyramidal Co(II) and tetrahedral Mn(II) corners exhibiting an overall S= 4 ground state has been crystallized and its magnetic properties investigated.     

Synthesis and magnetooptical properties of mesomorphic complexes of lanthanides with β-aminovinyl ketones

Complexes of the composition L(LH)₂Ln(NO₃)₂ (Ln = La, Dy, Gd, Er, Eu, or Tb) were obtained by the reaction of -aminovinyl ketone (LH) with rare earth metal nitrates. All the compounds synthesized are thermotropic liquid crystals having the smectic S_A phase. The values of magnetic anisotropy of these complexes measured by magnetic birefringence are fairly high.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2331–2333, September, 1996.     

Conversion of a porous material based on a Mn(II)-TCNQF(4) honeycomb net to a molecular magnet upon desolvation

Removal of methanol molecules from the interstices of a metal-organic framework based on a 2-D hexagonal Mn(II)-TCNQF(4) net results in stronger magnetic interactions and leads to a glassy magnetically ordered state; the magnetic behavior can be reversibly cycled upon solvation-desolvation of the material.     

A family of cyanide-bridged molecular squares: structural and magnetic properties of [{MIICl2}2{CoII(triphos)(CN)2}2].xCH2Cl2, M = Mn, Fe, Co, Ni, Zn

The syntheses, structures, and magnetic properties of a series of tetranuclear cyanide-bridged compounds are reported. This family of molecular squares, [{M(II)Cl2}2{Co(II)(triphos)(CN)2}2] (M = Mn ([CoMn]), Fe ([CoFe]), Co ([CoCo]), Ni ([CoNi]), and Zn ([CoZn]), triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane), has been synthesized by the reaction of Co(II)(triphos)(CN)2 and MCl2 (M = Mn, Co, Ni, Zn) or Fe4Cl8(THF)6 in a CH2Cl2/EtOH mixture. These complexes are isostructural and consist of two pentacoordinate Co(II) and two tetrahedral M(II) centers. The resulting molecular squares are characterized by antiferromagnetic coupling between metal centers that generally follows the spin-coupling model S total = SM(II)1 - SCo1 + SM(II)2 - SCo2. Magnetic parameters for all the complexes were measured using SQUID magnetometry. Additionally, [CoZn] and [CoMn] were studied by both conventional and high-frequency and high-field electron paramagnetic resonance.