pH- and Time-Dependent Release of Phytohormones from Diruthenium Complexes

Abstract

The controlled release of functionally active compounds is important in a variety of applications. Here, we have synthesized, characterized, and studied the magnetic properties of three novel metal−metal-bonded tris(formamidinato) Ru 2 5+ complexes. We have used different auxin-related hormones, indole-3-acetate (IAA), 2,4-dichlorophenoxyacetate (2,4-D), and 1-naphthaleneacetate (NAA), to generate [Ru 2 Cl(μ-DPhF) 3 (μ-IAA)] (RuIAA), [Ru 2 Cl(μ-DPhF) 3 (μ-2,4-D)] (Ru2,4-D), and [Ru 2 Cl(μ-DPhF) 3 (μ-NAA)] (RuNAA) (DPhF = N,N′-diphenylformamidinate). The crystal structures of RuIAA, RuIAA•THF, Ru2,4-D•CH 2 Cl 2 , and RuNAA•0.5THF have been determined by single-crystal Xray diffraction. To assess the releasing capacity of the bound hormone, we have employed a biological assay that relied on Arabidopsis thaliana plants expressing an auxin reporter gene and we demonstrate that the release of the phytohormones from RuIAA, Ru2,4-D, and RuNAA is pH-and time-dependent. These studies serve as a proof of concept showing the potential of these types of compounds as biological molecule carriers.

New insights into progressive ligand replacement from [Ru2Cl(O2CCH3)4]: synthetic strategies and variation in redox potentials and paramagnetic shifts

“…1, as well as in other similar complexes. 20,42–44,62–64 A second peak in the mass spectra of compounds 1 and 2 , assigned to the species [M + CH 3 CO] + , is observed.…”

“…40 Due to the high coordination capacity of the open-paddlewheel complexes, they can interact with nucleic acids, 20 biological macromolecules such as RNA, 41 and can be used as drug carriers. 42 In the case of monosubstituted [Ru 2 Cl(DArF)(O 2 CR) 3 ] compounds, until very recently, 43 only two species had been synthesized and described. 44 To the extent of our knowledge, no further studies in the supramolecular field have been carried out, even when they present three equatorial positions that can be replaced and two axial sites that can work as Lewis acidic sites.…”

Diruthenium(ii,iii) paddlewheel complexes: effects of bridging and axial ligands on anticancer properties

“…4). 63 The produced complexes [Ru 2 Cl(μ-DPhF) 3 (μ-IAA)], [Ru 2 Cl(μ-DPhF) 3 (μ-2,4-D)], and [Ru 2 Cl(μ-DPhF) 3 (μ-NAA)] were tested for their capability to detach the bound hormone at various pH values, via a very sensitive assay prepared on the basis of Arabidopsis thaliana plants; results demonstrated that the auxin ligands were released more rapidly at acidic and neutral pH than in slightly alkaline media. Indeed, as the auxins were found to be mostly in their anionic forms in solutions, their release from the diruthenium( ii , iii ) scaffold necessitates a protonation step, thus being favored in acidic pH.…”

Steric, Activation Method and Solvent Effects on the Structure of Paddlewheel Diruthenium Complexes

“…The syntheses and properties of numerous formally mixed-valent diruthenium(II,III) complexes have been reported to date [1][2][3]. The synthesis and reactivity of tetracarboxylatochloridodiruthenium complexes, [Ru 2 Cl(µ-O 2 CR) 4 ] (R = alkyl o aryl), with paddlewheel structure have been intensively studied due to their singular electronic and magnetic properties [4] and their potential applications in several fields as catalysers [5,6], anticancer drugs [7,8], drugs carriers [9] or structural probes of biomolecules [10][11][12]. These complexes are usually obtained by the metathesis reaction of [Ru 2 Cl(µ-O 2 CMe) 4 ] n with an excess of the corresponding carboxylic acid in a refluxing mixture of methanol/water (1:1).…”