A New Coordination Mode of the Photometric Reagent Glyoxalbis(2-hydroxyanil) (H2gbha): Bis-Bidentate Bridging by gbha2- in the Redox Series {(
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- 作者：Sanjib Kar ; Biprajit Sarkar ; Sandeep Ghumaan ; Dipankar Roy ; Francisco A. Urbanos ; Jan Fiedler ; Raghavan B. Sunoj ; Reyes Jimenez-Aparicio ; Wolfgang Kaim ; and Goutam Kumar Lahiri
- 刊名：Inorganic Chemistry
- 出版年：2005
- 出版时间：November 28, 2005
- 年：2005
- 卷：44
- 期：24
- 页码：8715 - 8722
- 全文大小：217K
- 年卷期：v.44,no.24(November 28, 2005)
- ISSN：1520-510X
文摘
The bis-bidentate bridging function of gbha2- with N,O-/N,O- coordination was observed for the first time in thecomplex (
-gbha)[RuIII(acac)2]2 (1). Density functional theory calculations of 1 yield a triplet ground state with alarge (
E > 6000 cm-1) singlet-triplet gap. Intermolecular antiferromagnetic coupling was observed (J 
-5.3cm-1) for the solid. Complex 1 undergoes two one-electron reduction and two one-electron oxidation steps; thefive redox forms {(-gbha)[Ru(acac)2]2}n (n = -2, -1, 0, +1, +2) were characterized by UV-vis-NIRspectroelectrochemistry (NIR = near infrared). The paramagnetic intermediates were also investigated by electronparamagnetic resonance (EPR) spectroscopy. The monoanion with a comproportionation constant Kc of 2.7 × 108does not exhibit an NIR band for a RuIII/RuII mixed-valent situation; it is best described as a 1,4-diazabutadieneradical anion containing ligand gbha
3-, which binds two ruthenium(III) centers. A RuIII-type EPR spectrum with g1= 2.27, g2 = 2.21, and g3 = 1.73 is observed as a result of antiferromagnetic coupling between one RuIII and theligand radical. The EPR-active monocation (Kc = 1.7 × 106) exhibits a broad (
1/2 = 2600 cm-1) intervalencecharge-transfer band at 1800 nm, indicating a valence-averaged (Ru3.5)2 formulation (class III) with a tendencytoward class II (borderline situation).
-gbha)[RuIII(acac)2]2 (1). Density functional theory calculations of 1 yield a triplet ground state with alarge (E > 6000 cm-1) singlet-triplet gap. Intermolecular antiferromagnetic coupling was observed (J -5.3cm-1) for the solid. Complex 1 undergoes two one-electron reduction and two one-electron oxidation steps; thefive redox forms {(-gbha)[Ru(acac)2]2}n (n = -2, -1, 0, +1, +2) were characterized by UV-vis-NIRspectroelectrochemistry (NIR = near infrared). The paramagnetic intermediates were also investigated by electronparamagnetic resonance (EPR) spectroscopy. The monoanion with a comproportionation constant Kc of 2.7 × 108does not exhibit an NIR band for a RuIII/RuII mixed-valent situation; it is best described as a 1,4-diazabutadieneradical anion containing ligand gbha3-, which binds two ruthenium(III) centers. A RuIII-type EPR spectrum with g1= 2.27, g2 = 2.21, and g3 = 1.73 is observed as a result of antiferromagnetic coupling between one RuIII and theligand radical. The EPR-active monocation (Kc = 1.7 × 106) exhibits a broad (1/2 = 2600 cm-1) intervalencecharge-transfer band at 1800 nm, indicating a valence-averaged (Ru3.5)2 formulation (class III) with a tendencytoward class II (borderline situation).