Monohydroxamic acids and bridging dihydroxamic acids as chelators to ruthenium(iii) and as nitric oxide donors: syntheses, speciation studies and nitric oxide releasing investigation

Abstract

The synthesis and spectroscopic characterisation of novel mononuclear Ru(III)(edta)(hydroxamato) complexes of general formula [Ru(H2edta)(monoha)] (where monoha = 3- or 4-NH2, 2-, 3- or 4-C1 and 3-Me-phenylhydroxamato), as well as the first example of a Ru(III)-N-aryl aromatic hydroxamate, [Ru(H2edta)(N-Me-bha)].H2O (N-Me-bha = N-methylbenzohydroxamato) are reported. Three dinuclear Ru(III) complexes with bridging dihydroxamato ligands of general formula [{Ru(H2edta)}2(mu-diha)] where diha = 2,6-pyridinedihydroxamato and 1,3- or 1,4-benzodihydroxamato, the first of their kind with Ru(III), are also described. The speciation of all of these systems (with the exception of the Ru-1,4-benzodihydroxamic acid and Ru-N-methylbenzohydroxamic systems) in aqueous solution was investigated. We previously proposed that nitrosyl abstraction from hydroxamic acids by Ru(III) involves initial formation of Ru(III)-hydroxamates. Yet, until now, no data on the rate of nitric oxide (NO) release from hydroxamic acids has been published. We now describe a UV-VIS spectroscopic study, where we monitored the decrease in the ligand-to-metal charge-transfer band of a series of Ru(III)-monohydroxamates with time, with a view to gaining an insight into the NO-releasing properties of hydroxamic acids.

Lossen Rearrangements under Heck Reaction Conditions

“…To determine whether Heck reaction conditions would result in Lossen rearrangements, different easily prepared hydroxamic acids18 ( 8a–f ) were exposed to these conditions (Scheme , Table 1). Heating these hydroxamic acids with catalytic Pd(OAc) 2 and triethylamine (TEA) in acetonitrile (CH 3 CN) or dimethylformamide (DMF) with stirring in a sealed glass tube at 90 °C for 24 h affords either the corresponding amines ( 9a – f ) or symmetrical ureas ( 10a–f , Scheme , Table 1).…”

“…Methanol (60 mL) was added and the precipitate was filtered, the solvent was removed under vacuum, diethyl ether (30 mL) was added and any formed precipitate was filtered. The filtrate was evaporated under vacuum yielding a white solid, which was recrystallized from water to give the product 18…”

An Experimental and Computational Approach to Understanding the Reactions of Acyl Nitroso Compounds in [4 + 2] Cycloadditions

“…Compounds 1-12 have been reported elsewhere [31][32][33][34][35][36][37][38][39][40][41][42] using different procedures to those described here.…”

Suberoylanilide hydroxamic acid, a potent histone deacetylase inhibitor; its X-ray crystal structure and solid state and solution studies of its Zn(II), Ni(II), Cu(II) and Fe(III) complexes

“…We have been fervently interested in the application of hydroxamic acids as bioligands [11][12][13][14][15][16][17][18] and in the design of novel metalbased cancer chemotherapeutics [11][12][13][14]. In fact we recently reported a bifunctional platinum-SAHA conjugate which possesses dual DNA binding and HDAC inhibitory activity as well as exhibiting potent cytotoxicity against the A2780 cisplatin sensitive ovarian cancer cell line [12].…”