|Budget Amount *help
¥5,600,000 (Direct Cost : ¥5,600,000)
Fiscal Year 1998 : ¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1997 : ¥3,600,000 (Direct Cost : ¥3,600,000)
We have carried out a development of a new type of resonator for pulse ESR at very low-temperature. We have also accomplished syntheses and characterization of a series of novel multi-nuclear transition metal compounds.
The resonator we have developed is a loop-gap type which can focus a microwave magnetic field in high density at the sample position. It can be assembled into a liquidhelium temperature controller which has been used for conventional F,SR, which enables to control sample temperature from room temperature to 2.7 K with an accuracy of less than 0.1 K.This means we can control a relaxation time of an electron spin in a radical complex. For the connection between a resonator and a microwave circuit, we adopted a Gordon-type coupler which can widely adjust coupling. By using this coupler a resonator can be overcoupled and the dead time after an irradiation of a microwave pulse could be reducedappreciably.
As for syntheses of multi-nuclear transition-metal compounds, we chose N
i(mnt)_2 derivatives which are known to be active for ^<14>N ESEEM.We succeeded in syntheses and structural characterizations of a series of novel compounds with formula A_2[M(mnt)_2(Cu_4X_4)] (A = Na, TBA ; M = Ni, Pd, Pt ; X= I, Br). Each compound contains a Ni(mnt)_2 moiety which retains the original planar structure and there is no significant change in Ni-S bond lengths compared to those of the parent compound. One side of the Ni(mnt)_2 moiety is covered with an eight-membered ring of Cu_4I_4 with copper atoms being close to the mnt sulfur atoms (Cu-S = 2.35 A in average). Depending on counter cations, the connection of dianionic [M(mnt)_2(Cu_4X_4)] part can be varied from a discrete molecule with A = Na(18-crown-6), one-dimensional chain with A = TBA, and to two-dimensional sheet with A = Na. Among these compounds, the one with A = Na(18-crown-6), M = Ni, and X= I shows strong ESR signal. The ESEEM measurements on this paramagnetic salt was conducted using the above-mentioned resonator and we could observe ^<14>N ESEEM clearly. Less