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Structural study of mixed crystals of [Zn 1− x Ru x (bpy) 3 ][NaCr(ox) 3 ] probed by high-resolution absorption spectroscopy and high-pressure experiments

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Published in Inorganic Chemistry. 2010, vol. 49, no. 7, p. 3402 - 3408
Abstract In the mixed crystal series of the cubic three-dimensional networks of composition [Zn1-xRux(bpy)3][NaCr(ox)3] (0e x e1, ox = C2O4 2-, bpy = 2,20-bipyridine), high-resolution absorption spectroscopy in the region of the 4A2f2E transition (R-lines) reveals the creation of five specific spectroscopic sites for the [Cr(ox)3]3- complex. The concentration of these spectroscopic sites follows a binomial distribution of [Zn(bpy)3]2þ and [Ru(bpy)3]2þ among the four nearest neighbors of a given [Cr(ox)3]3- complex within the network. The tris-bipyridine complexes occupying those positions have an optimal π-π interaction with the oxalate ligands of the tris-oxalate chromophore. The energy of each spectroscopic [Cr(ox)3]3- site depends on the total concentration of [Ru(bpy)3]2þ in the mixed crystal and on its specific distribution among the four nearest neighbors. Single crystal X-ray diffraction indicates a reduction of the unit cell volume when [Zn(bpy)3]2þ (a = 15.6365(18)A° ) is substituted by [Ru(bpy)3]2þ (a = 15.5098(6)A° ). This alone would lead to a red-shift of the R lines in analogy to the red-shift of 25.2 cm-1/GPa due to the decrease of the metal ligand Cr-O bond length as observed in high-pressure luminescence experiments. However, specific π-π interactions with the nearest neighbors have the opposite effect and shift the transition in discrete jumps to higher energies with increasing [Ru(bpy)3]2þ mole fraction.
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MILOS, Mia et al. Structural study of mixed crystals of [Zn 1− x Ru x (bpy) 3 ][NaCr(ox) 3 ] probed by high-resolution absorption spectroscopy and high-pressure experiments. In: Inorganic Chemistry, 2010, vol. 49, n° 7, p. 3402 - 3408. https://archive-ouverte.unige.ch/unige:6468

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Deposited on : 2010-05-04

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