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Language：English   Publisher：AMER CHEMICAL SOC  

A block single-crystal was obtained using a diffusion method with a concentrated acetone-water(vol. 1/1) solution of [Ru(phen)(3)]Cl-2. 6H(2)O (phen = 1,10-phenanthroline) and a concentrated aqueous solution of K-3[Cr(CN)(6)], without evaporating solvents. The crystal was identified as a double-complex salt including two acetone and fourteen solvent water molecules, [Ru(phen)(3)](2)[Cr(CN)(6)]Cl .2(CH3)(2)CO . 14H(2)O (1). Measurement of the X-ray diffraction pattern of the double-complex salt was performed using an X-ray diffractometer with an Imaging-Flare (IP) Weissenberg camera. 1 crystallizes in the triclinic space group P (1) over bar, with a = 13.930(5) Angstrom, b = 14.783(5) Angstrom, c = 11.137(6) Angstrom, alpha = 89.87(4)degrees, beta = 107.47(3)degrees gamma = 96.68(3)degrees, and Z = 2. The crystal structure is very different from that of [Ru(bpy)(3)](2)[Cr(CN)(6)]Cl . 8H(2)O (2) (bpy = 2,2 ' -bipyridine), which could be obtained using the same procedure and crystallizes in the monoclinic space group C2, with a = 22.414(2) Angstrom, b = 13.7686(15) Angstrom, c = 22.207(2) Angstrom, beta = 90.713(8)degrees, and Z = 4. The distance between the central-metal ions of ruthenium(II) and chromium(III) complexes in [Ru(phen)(3)](2)[Cr(CN)(6)]Cl .2(CH3)(2)CO . 14H(2)O (7.170 Angstrom) is shorter than that in [Ru(bPY)(3)](2)[Cr(CN)(6)]Cl . 8H(2)O (9.173 Angstrom) by about 2 Angstrom, while the rate of energy transfer from the (MLCT)-M-3 state of [Ru(N-N)(3)](2+) to the E-2(g) state of [Cr(CN)(6)](3-) in the former salt (9.5 x 10(5) s(-1)) is far slower than that in the latter one (6.0 x 10(6) s(-1)) at 77 K. These results indicate that the energy-transfer rate strongly depends, not upon the distance between central metal ions, rather, upon the mutual relative orientation between the donor and the acceptor complexes in double-complex salts.

DOI： 10.1021/ic0013936

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Language：English   Publisher：AMER CHEMICAL SOC  

In crystals of double-complex salts [M(bpy)(3)](2)[Cr(CN)(6)]Cl . 8H(2)O (M2+ = Ru2+, Os2+; bpy = 2,2'-bipyridine), luminescence from (CT)-C-3 state of [M(bpy)(3)](2+) is partially quenched by [Cr(CN)(6)](3-) at 77 K and room temperature (RT). This quenching is attributed to intermolecular excitation energy transfer from the (CT)-C-3 state of [M(bpy)(3)](2+) to the E-2(g) state of [Cr(CN)(6)](3-). Crystal structure and crystal parameters of [Os(bpy)(3)](2)[Cr(CN)(6)]Cl . 8H(2)O: monoclinic, C2, a = 22.384(4) Angstrom, b = 13.827(4) Angstrom, c = 22.186(3) Angstrom, beta = 90.70(2)degrees, V = 6866(2) Angstrom(3), Z = 4, R = 0.0789, R-w = 0.1932: are almost the same as those of [Ru(bpy)(3)](2)[Cr(CN)(6)]Cl . 8H(2)O: monoclinic, C2, a = 22.414(2) Angstrom, b = 13.7686(15) Angstrom, c = 22.207(2) Angstrom, beta = 90.713(8)degrees, V = 6852.9(12) Angstrom(3), Z = 4, R = 0.0554; R-w = 0.1679. Moreover, these double complex salts have the same distance and relative orientation between donor and acceptor. The rate of intermolecular energy transfer from [M(bpy)(3)](2+) to [Cr(CN)(6)](3-) was evaluated by the decay time of luminescence from (CT)-C-3 state of [M(bpy)(3)](2+) in single- and double-complex salts. The rate of energy transfer in [Os(bpy)(3)](2)[Cr(CN)(6)]Cl . 8H(2)O (4.9 x 10(7) s(-1)) is about eight times larger than that in [Ru(bpy)(3)](2)[Cr(CN)(6)]Cl . 8H(2)O (6.0 x 10(6) s(-1)) at 77 K. The difference of energy transfer rate is brought about by only the spectral overlap between the normalized luminescence spectrum from the (CT)-C-3 state of donor ([M(bpy)(3)](2+)) and the normalized excitation spectrum of the E-2(g) state of acceptor ([Cr(CN)(6)](3-)) in the salts. Decay rates of the (CT)-C-3 state in [M(bpy)(3)](2)[Cr(CN)(6)]Cl . 8H(2)O were measured as a function of temperature. A large enhancement of a decay rate from the (CT)-C-3 state was obtained for [Ru(bpy)(3)](2)[Cr(CN)(6)]Cl . 8H(2)O as the temperature was increased. This result implies that an additional path from the (CT)-C-3 state of [Ru(bpy)(3)](2+) to the T-2(2g) state of [Cr(CN)(6)](3-) would be opened for energy transfer with a rise in temperature in [Ru(bpy)(3)](2)[Cr(CN)(6)]Cl . 8H(2)O.

DOI： 10.1021/ic9810541

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Language：English   Publisher：American Chemical Society  

The time-resolved ESR (TR-ESR) signals of ground-state (4A2g) of Cr(III) ion were observed in ruby and of Cr(acac)3 doped in Al(acac)3 single crystals after irradiation with the second harmonic of a Nd: YAG laser at 77 K. At room temperature, TR-ESR signal was observed in ruby, but not in Cr(acac)3. Both spectra at 77 K were of the emissive type
however, the intensity of the Cr(acac)3 signal was very weak. The observed TR-ESR signal in ruby was changed from emissive polarity to an absorptive one at 700 μs. The results of ruby and Cr(acac)3 doped in Al(acac)3 were explained by the initial emissive polarization and the recovery absorptive polarization from the excited state 2E. The spin polarization in the sublevels of the ground state was very long (about 500 μs).

DOI： 10.1021/jp972778l

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DOI： 10.1246/cl.1998.231

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DOI： 10.1021/jp972778l

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