Kar, Sanjib ; Chanda, Nripen ; Mobin, Shaikh M. ; Datta, Anindya ; Urbanos, Francisco A. ; Puranik, Vedavati G. ; Jimenez-Aparicio, Reyes ; Lahiri, Goutam Kumar (2004) Diruthenium complexes [{(acac)2RuIII}2(μ-OC2H5)2], [{(acac)2RuIII}2(μ-L)](ClO4)2, and [{(bpy)2RuII}2(μ-L)](ClO4)4 [L = (NC5H4)2-N-C6H4-N-(NC5H4) 2, acac = acetylacetonate, and bpy = 2,2'-bipyridine]. synthesis, structure, magnetic, spectral, and photophysical aspects Inorganic Chemistry, 43 (16). pp. 4911-4920. ISSN 0020-1669
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Official URL: http://pubs.acs.org/doi/abs/10.1021/ic0498900
Related URL: http://dx.doi.org/10.1021/ic0498900
Abstract
Paramagnetic diruthenium(III) complexes (acac)2RuIII(μ-OC2H5)2RuIII(acac)2 (6) and [(acac)2RuIII(μ-L)RuIII(acac)2](ClO4)2, [7](ClO4)2, were obtained via the reaction of binucleating bridging ligand, N,N,N',N'-tetra(2-pyridyl)-1,4-phenylenediamine [(NC5H4)2-N-C6H4-N-(NC5H4)2, L] with the monomeric metal precursor unit (acac)2RuII(CH3CN)2 in ethanol under aerobic conditions. However, the reaction of L with the metal fragment RuII(bpy)2(EtOH)22+ resulted in the corresponding [(bpy)2RuII (μ-L) RuII(bpy)2](ClO4)4, [8](ClO4)4. Crystal structures of L and 6 show that, in each case, the asymmetric unit consists of two independent half-molecules. The Ru-Ru distances in the two crystallographically independent molecules (F and G) of 6 are found to be 2.6448(8) and 2.6515(8) Å, respectively. Variable-temperature magnetic studies suggest that the ruthenium(III) centers in 6 and [7](ClO4)2 are very weakly antiferromagnetically coupled, having J = -0.45 and -0.63 cm-1, respectively. The g value calculated for 6 by using the van Vleck equation turned out to be only 1.11, whereas for [7](ClO4)2, the g value is 2.4, as expected for paramagnetic Ru(III) complexes. The paramagnetic complexes 6 and [7]2+ exhibit rhombic EPR spectra at 77 κ in CHCl3 (g1 = 2.420, g2 = 2.192, g3 = 1.710 for 6 and g1 = 2.385, g2 = 2.177, g3 = 1.753 for [7]2+). This indicates that 6 must have an intermolecular magnetic interaction, in fact, an antiferromagnetic interaction, along at least one of the crystal axes. This conclusion was supported by ZINDO/1-level calculations. The complexes 6, [7]2+, and [8]4+ display closely spaced Ru(III)/Ru(II) couples with 70, 110, and 80 mV separations in potentials between the successive couples, respectively, implying weak intermetallic electrochemical coupling in their mixed-valent states. The electrochemical stability of the Ru(II) state follows the order:∅ [7]2+ < 6 <[8]4+. The bipyridine derivative [8]4+ exhibits a strong luminescence [quantum yield (φ) = 0.18] at 600 nm in EtOH/MeOH (4:1) glass (at 77 κ), with an estimated excited-state lifetime of approximately 10 μ s.
| Item Type: | Article |
|---|---|
| Source: | Copyright of this article belongs to American Chemical Society. |
| ID Code: | 88399 |
| Deposited On: | 28 Mar 2012 10:01 |
| Last Modified: | 28 Mar 2012 10:01 |
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