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Controlling Metal–Ligand–Metal Oxidation State Combinations by Ancillary Ligand (L) Variation in the Redox Systems [L 2 Ru(μ‐boptz)RuL 2 ] n , boptz=3,6‐bis(2‐oxidophenyl)‐1,2,4,5‐tetrazine, and L=acetylacetonate, 2,2′‐bipyridine, or 2‐phenylazopyridine
Author(s) -
Patra Srikanta,
Sarkar Biprajit,
Maji Somnath,
Fiedler Jan,
Urbanos Francisco A.,
JimenezAparicio Reyes,
Kaim Wolfgang,
Lahiri Goutam Kumar
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200500295
Subject(s) - chemistry , ligand (biochemistry) , electron paramagnetic resonance , ruthenium , redox , oxidation state , metal , crystallography , bridging ligand , acceptor , photochemistry , crystal structure , medicinal chemistry , inorganic chemistry , catalysis , nuclear magnetic resonance , organic chemistry , condensed matter physics , biochemistry , physics , receptor
The new compounds [(acac) 2 Ru(μ‐boptz)Ru(acac) 2 ] ( 1 ), [(bpy) 2 Ru(μ‐boptz)Ru(bpy) 2 ](ClO 4 ) 2 ( 2 ‐(ClO 4 ) 2 ), and [(pap) 2 Ru(μ‐boptz)Ru(pap) 2 ](ClO 4 ) 2 ( 3 ‐(ClO 4 ) 2 ) were obtained from 3,6‐bis(2‐hydroxyphenyl)‐1,2,4,5‐tetrazine (H 2 boptz), the crystal structure analysis of which is reported. Compound 1 contains two antiferromagnetically coupled ( J =−36.7 cm −1 ) Ru III centers. We have investigated the role of both the donor and acceptor functions containing the boptz 2− bridging ligand in combination with the electronically different ancillary ligands (donating acac − , moderately π‐accepting bpy, and strongly π‐accepting pap; acac=acetylacetonate, bpy=2,2′‐bipyridine pap=2‐phenylazopyridine) by using cyclic voltammetry, spectroelectrochemistry and electron paramagnetic resonance (EPR) spectroscopy for several in situ accessible redox states. We found that metal–ligand–metal oxidation state combinations remain invariant to ancillary ligand change in some instances; however, three isoelectronic paramagnetic cores Ru(μ‐boptz)Ru showed remarkable differences. The excellent tolerance of the bpy co ‐ ligand for both Ru III and Ru II is demonstrated by the adoption of the mixed ‐ valent form in [L 2 Ru(μ‐boptz)RuL 2 ] 3+ , L=bpy, whereas the corresponding system with pap stabilizes the Ru II states to yield a phenoxyl radical ligand and the compound with L=acac − contains two Ru III centers connected by a tetrazine radical‐anion bridge.