Premium
A bipyridine‐ligated zinc(II) complex with bridging flavonolate ligation: synthesis, characterization, and visible‐light‐induced CO release reactivity
Author(s) -
Sorenson Shayne,
Popova Marina,
Arif Atta M.,
Berreau Lisa M.
Publication year - 2017
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229617011366
Subject(s) - chemistry , zinc , denticity , deprotonation , bridging ligand , bipyridine , perchlorate , ligand (biochemistry) , octahedral molecular geometry , medicinal chemistry , stereochemistry , metal ions in aqueous solution , metal , crystallography , inorganic chemistry , crystal structure , ion , organic chemistry , biochemistry , receptor
Metal–flavonolate compounds are of significant current interest as synthetic models for quercetinase enzymes and as bioactive compounds of importance to human health. Zinc–3‐hydroxyflavonolate compounds, including those of quercetin, kampferol, and morin, generally exhibit bidentate coordination to a single Zn II center. The bipyridine‐ligated zinc–flavonolate compound reported herein, namely bis(μ‐4‐oxo‐2‐phenyl‐4 H ‐chromen‐3‐olato)‐κ 3 O 3 : O 3 , O 4 ;κ 3 O 3 , O 4 : O 3 ‐bis[(2,2′‐bipyridine‐κ 2 N , N ′)zinc(II)] bis(perchlorate), {[Zn 2 (C 15 H 9 O 3 ) 2 (C 10 H 8 N 2 ) 2 ](ClO 4 ) 2 } n , ( 1 ), provides an unusual example of bridging 3‐hydroxyflavonolate ligation in a dinuclear metal complex. The symmetry‐related Zn II centers of ( 1 ) exhibit a distorted octahedral geometry, with weak coordination of a perchlorate anion trans to the bridging deprotonated O atom of the flavonolate ligand. Variable‐concentration conductivity measurements provide evidence that, when ( 1 ) is dissolved in CH 3 CN, the complex dissociates into monomers. 1 H NMR resonances for ( 1 ) dissolved in d 6 ‐DMSO were assigned via HMQC to the H atoms of the flavonolate and bipyridine ligands. In CH 3 CN, ( 1 ) undergoes quantitative visible‐light‐induced CO release with a quantum yield [0.004 (1)] similar to that exhibited by other mononuclear zinc–3‐hydroxyflavonolate complexes. Mass spectroscopic identification of the [(bpy) 2 Zn( O ‐benzoylsalicylate)] + ion provides evidence of CO release from the flavonol and of ligand exchange at the Zn II center.