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Photoinduced electron‐transfer reactions of tris(2,2′‐bipyridine)ruthenium(II)‐based carbonic anhydrase inhibitors tethering plural binding sites
Author(s) -
Suwa Mikiko,
Imamura Narumi,
Awano Pirika,
Nakata Eiji,
Takashima Hiroshi
Publication year - 2018
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.3848
Subject(s) - chemistry , ruthenium , intramolecular force , photochemistry , bipyridine , photoinduced electron transfer , electron transfer , electron acceptor , amide , stereochemistry , medicinal chemistry , catalysis , crystallography , crystal structure , organic chemistry
Abstract Tris(2,2′‐bipyridine)ruthenium(II) complex‐based carbonic anhydrase (CA) inhibitors, [Ru(bpy) 2 (bpydbs)] 2+ {bpy = 2,2′‐bipyridine and bpydbs = 2,2′‐bipyridinyl‐4,4′‐dicarboxilic acid bis[(2‐{2‐[2‐(4‐sulfamoylbenzoylamino)ethoxy]ethoxy}ethyl)amide]} and [Ru(bpydbs) 3 ] 2+ , tethering plural benzenesulfonamide groups have been prepared. The CA catalytic activity was effectively suppressed by these synthetic [Ru(bpy) 2 (bpydbs)] 2+ and [Ru(bpydbs) 3 ] 2+ inhibitors, and their dissociation constants at pH = 7.2 and at 25°C were determined to be K I = 0.93 ± 0.02 μM and K I = 0.24 ± 0.03 μM, respectively. Next, 2 photoinduced electron‐transfer (ET) systems comprising a Ru 2+ ‐CA complex and an electron acceptor, such as chloropentaamminecobalt(III) ([CoCl(NH 3 ) 5 ] 2+ ) or methylviologen (MV 2+ ) were studied. In the presence of CA and a sacrificial electron acceptor, such as pentaamminechlorocobalt(III) complex, the photoexcited triplet state of 3 ([Ru(II)] 2+ )* was quenched through an intermolecular photoinduced ET mechanism. In case of the [Ru(bpydbs) 3 ] 2+ ‐CA‐MV 2+ system, the photoexcited triplet state of 3 ([Ru(bpydbs) 3 ] 2+ )* was quenched by sacrificial quencher through an intermolecular photoinduced ET mechanism, giving the oxidized [Ru(bpydbs) 3 ] 3+ . Then the following intramolecular ET from the amino acid residue, Tyr6, near the active site of CA proceeded. We observed a transient absorption around at 410 nm, arising from the formation of a Tyr •+ in the [Ru(bpydbs) 3 ] 2+ ‐CA‐MV 2+ system. These artificial Ru(II)‐CA systems may clearly demonstrate both intermolecular and intramolecular photoinduced ET reactions of protein and could be one of the interesting models of the ET proteins. Their photophysical properties and the detailed ET mechanisms are discussed in order to clarify the multistep ET reactions.