A Synthetic Route to a Ruthenium Complex via Successive Photosubstitution Reactions

Abstract

Photosubstitution reactions of cis-[Ru­(bpy)2(MeCN)2]2+ with a pyrazole ligand (pzH) were studied under various conditions toward the development of a photochemical synthetic route to polypyridyl ruthenium complexes (bpy = 2,2′-bipyridine). In the absence of a base, light irradiation of an acetonitrile solution of pyrazole and cis-[Ru­(bpy)2(MeCN)2]2+ gave a mixture of the reactant and cis-[Ru­(bpy)2(pzH)­(MeCN)]2+. In the presence of a mild base such as N,N-dimethylaminopyridine, a second photosubstitution from cis-[Ru­(bpy)2(pzH)­(MeCN)]2+ to cis-[Ru­(bpy)2(pz)­(pzH)]+ (1b) was greatly enhanced, as confirmed by UV–vis and 1H nuclear magnetic resonance spectroscopy. The yields of 1b were increased in solvents with moderate coordinating properties, such as acetone. The successive photosubstitution reaction was observed using a stoichiometric amount of pyrazole.

Modulating Excited State Properties and Ligand Ejection Kinetics in Ruthenium Polypyridyl Complexes Designed to Mimic Photochemotherapeutics

“…S2-bpy showed the highest PTI of all of the complexes, although our measured PTI's are significantly lower than those reported for the same complex on HL60 leukemia (PTI = 188) and A549 lung (PTI = 136) cancer cells by Glazer and co-workers. 22 The PTIs observed for the complexes reported herein are also lower than other recently reported Ru(II) PCTs such as the Ru(II) cytochrome P450 3A4 inhibitor reported by Toupin et al (PTI = 9), 82 a trisheteroleptic Ru(II) complex that inhibited conjunctival 84 However, a direct comparison between PTIs is difficult given the wide range of experimental variables including cell line, growth medium, irradiation source, distance, flux, and time. This is demonstrated by the lowered PTIs for S2-bpy in our experiment compared to the conditions used by Glazer and co-workers.…”

Ruthenium Pyrazole Complexes: A Family of Highly Active Metallodrugs for Photoactivated Chemotherapy

“…The ruthenium complex with ClpzH ligands (ClpzH = 4-chloropyrazole), cis-[Ru(bpy) 2 (Clpz)(ClpzH)] + 2b, was synthesized by a stepwise photosubstitution reaction of cis-[Ru-(bpy) 2 (MeCN) 2 ] 2+ in the presence of ClpzH and N,Ndimethyl-4-aminopyridine as a base in an analogous procedure to our previous report. 42 Removal of excess unreacted ClpzH ligand and DMAP by washing with THF afforded spectroscopically pure 2b in a moderate synthetic yield. On the contrary, the thermal reaction of cis-Ru(bpy) 2 Cl 2 with ClpzH and silver trifluoromethanesulfonate gave a mixture of 2b and monosubstituted product, cis-[Ru(bpy) 2 (ClpzH)Cl] + .…”

Unravelling the kinetics of electro- and photochemical S → O linkage isomerization in Ru(ii)–NHC–DMSO complexes utilised for photoinduced substitution reactions

“…In addition to the intra-ligand π → π* transitions, due to the aromatic ligands, below 280 nm, an intense band at 292 nm was observed, typically belonging to the bpy system for bpy(π) → bpy(π*) transitions. 60,61 Coordination of the bpy to the Ru( ii ) centre induced red-shifts of 7 nm (in 3a ) and 5 nm (in 3b ) in wavelength for the dπ(Ru) → π*(NHC) MLCT transition compared to 2a and 2b , respectively (Fig. 3).…”