FUNDAMENTAL ASPECTS OF COORDINATION CHEMISTRY OF TRANSITION METALS WITH FUNCTIONALLY SUBSTITUTED THIOAMIDES (PART 2)

Abstract

In the second part of the analytical review, the influence of polydentate and N-allyl-substituted thiamides on the course of complexation reactions with platinum metal ions and Ag(I) was analyzed. The potential of the obtained coordination compounds for their application in medical and analytical chemistry is also demonstrated. The presented results are obtained on the basis of joint research performed in the Department of "Chemistry of Complex Compounds" of the V.I. Vernadsky Institute of General and Inorganic Chemistry NAS of Ukraine together with the staff of the Department of “Chemistry of Heterocyclic Compounds” of the Institute of Organic Chemistry NAS of Ukraine. The example of the reaction of polydentate thioureas with metal ions shows that the increase in functional groups does not always lead to their simultaneous coordination with metal ions. For example, the migration of double bonds, which is characteristic of H2 L5 thioureas, contributes to the stiffness of heterocycles, which in turn reduces the dentat capacity of these thioureas as ligands, despite the localization of donor atoms in a favorable position for metallocycle formation. In addition, an increase in the number of donor centers in the thioamide molecule can lead to their intramolecular rearrangement under conditions of complexation, and to the occurs of redox reactions. It has been shown that the formation of a π coordination bond involved in the formation of a six-membered chelated metalocycle occurs only when, together with the C=C allyl moiety, other donor atoms of the organic ligand are at an unfavorable geometric  location for metalocycle formation. Otherwise, the allyl group does not participate in the coordination to the central metal ion. A characteristic indicator of the formation of the π coordination bond is the splitting of the C3 H2 signal of allylic group protons in 1 H NMR spectra into two doublets with the same spin-spin interaction constant, as well as high-frequency shift of absorption bands of valence vibrations νas(CH)allyl, νs (CH) allyl in the IR spectra of π,n-chelate complexes.It was found that regardless of the stoichiometry of the starting components, the reaction of N-allyl-substituted thioamides HL10-12 with platinum metal ions leads to the formation of complexes only in the ratio M:L=1:1, due to the strong "trans-effect" of the allylic fragment. It was found that a number of n,π-chelate complexes of palladium(II) and platinum(II) with general formula [Pd/Pt(HL10-12)Hal2 ] (Hal = Cl-, Br- , I- ), which are structurally analogous to the known antitumor agent cisplatin, show effective antitumor action: antiproliferative, cytotoxic, anti-metastatic, proapoptotic. However, unlike cisplatin, they have proven to be much more effective: they are stable over a wide pH range; have the ability to overcome the resistance of pathogenic cells to the action of antitumor agents and show a wider range of action. The method of molecular docking was used to study the possible mechanism of interaction of the studied complexes, ie the most probable orientation and location of the complex molecule relative to the protein site of DNA binding was determined by mathematical modeling. Thioamide H2 L1 has been found to be an effective universal analytical reagent for the determination, extraction and separation of Ru(III), Rh(III) and Pd(II) from model solutions of their chlorides. The difference in the formation of anionic complexes of these metals and their ionic associations with the cationic dye atrafloxin is the basis of the developedmethod of extraction-photometric determination and stepwise separation of Ru(III), Rh(II) and Pd(II), which is important for applied aspects chemistry.