Coordination of o-benzosemiquinonate, o-iminobenzosemiquinonate, 4, 4′-di-tert-butyl-2, 2′-bipyridine and 1, 10-phenanthroline anion radicals to oxidovanadium(iv). (7th November 2016)

• Record Type: Journal Article
• Authors: Shit, Madhusudan; Maity, Suvendu; Bera, Sachinath; Weyhermüller, Thomas; Ghosh, Prasanta
• Is Part Of: New journal of chemistry. Volume 40:Number 12(2016:Dec.)
• Page Start: 10305
• Page End: 10315
• Publication Date: 2016-11-07
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c6nj02220k
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : Coordination of semiquinonate and heterocyclic α-diimine anion radicals to oxidovanadium(iv ) is authenticated. Abstract : This article reports on the stabilization of organic radical anions promoted by the oxidovanadium(iv ) ion. A 3, 5-di- tert -butylcatecholate ( t Bu catH − ) complex of oxidovanadium(v ) of the type [(L a ONO 2− )(VO 3+ )( t Bu catH − )] (1 ) was isolated using tridentate ( E )- N ′-((3-hydroxynaphthalen-2-yl)methylene)benzohydrazide (L a ONO H2 ) as a coligand, whereas o -benzosemiquinonate (sq˙ − ) and p -nitro- o -iminobenzosemiquinonate ( NO2 isq˙ − ) radical anion complexes of oxidovanadium(iv ) of the types [(LNNO − )(VO 2+ )(sq˙ − )] (2 ) and [(LNNO − )(VO 2+ )( NO2 isq˙ − )] (3 ) were successfully isolated using (1 Z, N ′ E )- N ′-(phenyl(pyridin-2-yl)methylene)benzohydrazonic acid (LNNO H) as a coligand. Oxidovanadium(iv ) complexes of the types [(L b ONO 2− )(VO 2+ )(phen)] (4 ) and [(L b ONO 2− )(VO 2+ )( t Bu bpy)] (5 ), which undergo reversible reduction to the 4, 4′-di- tert -butyl-2, 2′-bipyridine radical anion ( t Bu bpy˙ − ) and the 1, 10-phenanthroline radical anion (phen˙ − ) to afford the coupled states [(L b ONO 2− )(VO 2+ )(phen˙ − )] − (4 − ) and [(L b ONO 2− )(VO 2+ )( t Bu bpy˙ − )] − (5 − ), respectively, were isolated (L b ONO H2 = ( E )- N ′-(2-hydroxybenzylidene)benzohydrazide). The molecular geometries of the complexes were confirmed by the single-crystal X-ray structure determinations of1, 3 and4 . In1, the V–Ophenolato length cis to VO is 1.879(2) Å and the dissimilar V–O and V–OH lengths corresponding to the t Bu catH − ligand are 1.832(2) and 2.312(2) Å, respectively. In1, the average C–O lengths in t Bu catH − are 1.351(3) Å, whereas in3 the average C–O and C–N lengths in NO2 isq˙ − are 1.293(4) and 1.355(5) Å, respectively. In4, the V–Ophenolato length cis to VO (1.937(3) Å) is relatively longer. The 51 V NMR spectrum of1 displays a signal at −337.2 ppm, whereas the signals for2 and3 are deshielded to +382.4 and +71.8 ppm, respectively. The closed-shell singlet (CSS) solutions of3 and5 − at the B3LYP/DFT level are unstable and the open-shell singlet (OSS) solutions are 0.5 and 7.3 kcal mol −1 lower in energy, respectively, than the CSS solutions. In3 and5 − the alpha spin (100%) is localized on the vanadium ion, whereas the beta spin is delocalized across the aminophenol and bipyridine fragments.2 and3 exhibit lower-energy absorption bands at 785 and 585 nm, which are defined as CSS → OSS perturbation transitions.