Control of Exchange Interactions in π Dimers of 6-Oxophenalenoxyl Neutral π Radicals: Spin-Density Distributions and Multicentered-Two-Electron Bonding Governed by Topological Symmetry and Substitution at the 8-Position.

The tri-tert-butylphenalenyl (TBPLY) radical exists as a π dimer in the crystal form with perfect overlapping of the singly occupied molecular orbitals (SOMOs) causing strong antiferromagnetic exchange interactions. 2,5-Di-tert-butyl-6-oxophenalenoxyl (6OPO) is a phenalenyl-based air-stable neutral π radical with extensive spin delocalization and is a counter analogue of phenalenyl in terms of the topological symmetry of the spin density distribution. X-ray crystal structure analyses showed that 8-tert-butyl- and 8-(p-XC6H4)-6OPOs (X=I, Br) also form π dimers in the crystalline state. The π-dimeric structure of 8-tert-butyl-6OPO is seemingly similar to that of TBPLY even though its SOMO-SOMO overlap is small compared with that of TBPLY. The 8-(p-XC6H4) derivatives form slipped stacking π dimers in which the SOMO-SOMO overlaps are greater than in 8-tert-butyl-6OPO, but still smaller than in TBPLY. The solid-state electronic spectra of the 6OPO derivatives show much weaker intradimer charge-transfer bands, and SQUID measurements for 8-(p-BrC6H4)-6OPO show a weak antiferromagnetic exchange interaction in the π dimer. These results demonstrate that the control of the spin distribution patterns of the phenalenyl skeleton switches the mode of exchange interaction within the phenalenyl-based π dimer. The formation of the relevant multicenter-two-electron bonds is discussed.

Organic tailored batteries materials using stable open-shell molecules with degenerate frontier orbitals.

Secondary batteries using organic electrode-active materials promise to surpass present Li-ion batteries in terms of safety and resource price. The use of organic polymers for cathode-active materials has already achieved a high voltage and cycle performance comparable to those of Li-ion batteries. It is therefore timely to develop approaches for high-capacity organic materials-based battery applications. Here we demonstrate organic tailored batteries with high capacity by using organic molecules with degenerate molecular orbitals (MOs) as electrode-active materials. Trioxotriangulene (TOT), an organic open-shell molecule, with a singly occupied MO (SOMO) and two degenerate lowest-unoccupied MOs (LUMOs) was investigated. A tri-tert-butylated derivative ((t-Bu)(3)TOT)exhibited a high discharge capacity of more than 300 A h kg(-1), exceeding those delivered by Li-ion batteries. A tribrominated derivative (Br(3)TOT) was also shown to increase the output voltage and cycle performance up to 85% after 100 cycles of the charge-discharge processes.

Crystallization and preliminary X-ray diffraction studies of nucleoside diphosphate kinase from Thermus thermophilus HB8.

Nucleoside diphosphate (NDP) kinase contributes to the maintenance of cellular pools of all nucleoside triphosphates (NTPs) by catalyzing the transfer of the gamma-phosphoryl group from an NTP donor to an NDP acceptor. NDP kinase from the extreme thermophilic bacterium Thermus thermophilus HB8 was overexpressed in Escherichia coli and crystallized at 297 K using polyethylene glycol 8000 as the precipitant by means of the hanging-drop vapour-diffusion procedure. The crystals belong to the hexagonal system, space group P6(3)22, with unit-cell parameters a = b = 124.0, c = 104.9 A, alpha = beta = 90, gamma = 120 degrees. Assuming the asymmetric unit to contain two subunits, the calculated V(M) value was 3.7 A(3) Da(-1). The crystals diffracted X-rays generated by the synchrotron at SPring-8 to at least 1.9 A resolution and were suitable for high-resolution X-ray crystal structure determination.