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New pyrazole-3,5-dicarboxylato (pzdc) chromate(III) complexes containing linear tetradentate edda (ethylenediamine-N,N′-diacetate), trdda (trimethylenediamine-N,N′-diacetate), or eddp (ethylenediamine-N,N′-dipropionate) were synthesized and characterized by elemental analyses, column chromatography, 2 H NMR, FAB mass spectra, and X-ray analyses. Crystallographic data for Na[Cr 2 (edda) 2 (µ-pzdc)]·5H 2 O (1) are monoclinic with space group P2 1 /n, a ) 11.73(1) Å, b ) 19.475(6) Å, c ) 13.229(6) Å, ) 111.99(5)°, Z ) 4, and a final R factor of 0.056 based on 4673 reflections. Na[Cr 2 (trdda) 2 (µ-pzdc)]·3H 2 O (2) crystallizes in the orthorhombic space group Fdd2, with a ) 16.576(4) Å, b ) 29.235(6) Å, c ) 12.544(5) Å, Z ) 8, and a final R factor of 0.078 based on 2456 reflections. In both complexes two Cr(III) units were bridged by a pzdc. The complex 1 and 2 has a (symcis)-(unsym-cis) edda and (unsym-cis)-(unsym-cis) trdda geometrical configuration, respectively. Unlike the edda and trdda ligands, the eddp ligand formed mononuclear pzdc complexes, which may correspond to two geometrical isomers of unsym-cis-mer-and fac-[Cr(eddp)(pzdc)] 2- (3 and 4). The differences in the formations of the pzdc Cr(III) complexes with the edda-type ligands were demonstrated to arise from the chelate ring sizes and/or the intramolecular interaction such as hydrogen bond and van der Waals contact between two Cr(III)-edda type units. The hydrogen bond between the edda moieties following stereognostic coordination brings about the novel inert unsym-cis configuration in complex 1.

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S-Bridged trinuclear complexes, [CrIII{M(aet)3}2]3+, (M = RhIII (1), IrIII (2); aet = NH2CH2CH2S−) were newly prepared by the reaction of fac(S)-[M(aet)3] with chromium(III) nitrate. They were separated and optically resolved into the ΔΔ, ΛΛ, and ΔΛ isomers. Of these isomers for 1 and 2, the crystal structures of the ΔΛ isomers (1a and 2a) were determined by an X-ray diffraction method. Each of 1a and 2a consists of two fac(S)-[M(aet)3] subunits, a central Cr atom, three nitrates, and three water molecules, [Cr{M(aet)3}2](NO3)3·3H2O, in which three metals are aligned so as to be exactly linear. The central Cr atom is situated in an octahedral environment with the CrIIIS6 chromophore, which is formed by the coordination of two terminal fac(S)-[M(aet)3] units. The other isomers for 1 and 2 were characterized by the absorption and CD spectra, the molar conductivity, and the magnetic susceptibility. Each cyclic voltammogram of ΔΛ-[Cr{M(aet)3}2]3+ in water showed a reversible redox couple (M(IV)/M(III)) and an irreversible reduction wave (Cr(III)/Cr(II)). The stabilities of the S-bridged MCrIIIM complexes are also discussed in relation to the Cr–S bond strengths.

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Chromium(III)-lanthanide(III) hetero-polynuclear complex was synthesized and characterized. The structure of [Cr2Nd3(μ-OOCCH3)6(μ-OH)6(H2O)9]Br3·NaBr·8H2O (1) was determined by X-ray analysis.

As described in this paper, we propose an attitude control system for underwater vehicle/manipulator systems (UVMSs) based on control of the position of the center of buoyancy with respect to the center of gravity. Control of the center of buoyancy is accomplished using movable float blocks. The attitude control system is useful to control the pitch angle of UVMSs to enhance their performance and to improve their efficiency of underwater operations.A UVMS that has two 5-degree-of-freedom (DOF) manipulators was developed to verify the effectiveness of the proposed attitude control system. This paper presents a numerical study and some experimental results obtained using the UVMS with the attitude control system. We experimentally confirmed that the proposed system can change the pitch angle of the vehicle between −120 and +105 deg. In another experiment, attitudemaintenance control was conducted. Results show that the proposed system can maintain the vehicle's horizontal attitude during motion of the manipulators.

This paper presents development and motion evaluation of a human-portable underwater robot for soil core sampling. The developed robot is a remotely operated vehicle (ROV) with a core sampling pipe. In general, core sampling devices are heavy and penetrate into the soil by their own weight. In contrast, the developed robot is lightweight and penetrates the soil by its thrust force. This robot has neutral buoyancy; it can therefore move to desired areas using its thrusters. As explained in this paper, we describe the robot specifications and present results of preliminary experiments for the motion performance. Experiments in a test tank demonstrate its static stability, vertical motion for core samplings, and other beneficial features. Moreover, field tests in a lake demonstrate the feasibility of the developed core sampling robot. The soil penetration depth was approximately 0.16 [m] in the first trial.