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Charles Farrar Browne

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Výzkum

Trithiocyanurate complexes of iron, manganese and nickel and their anticholinesterase activity

Sodium salt of trithiocyanuric acid (ttcH3 = trithiocyanuric acid, also named as 2,4,6-trimercapto-1,3,5-triazine (TMT)) readily forms precipitates with heavy metal ions and that is why it is used for removal of heavy metal ions from industrial waste water. Effectiveness of heavy metal removal was widely studied by Atwood et al. [1-6] and other groups [7-10]. Removal of residual palladium and its compounds from reaction mixtures in preparation of drugs, in which palladium is used as a catalyst, is also very important and presented in many papers [11-14]. Trithiocyanuric acid and its salts have found wide range of applications for example the use as silver and nickel plating agents, the production of composite materials with metals and rubbers and a rewritable image formation by photopolymerization of the acid [15-18].

Biological activity of trithiocyanuric compound was also evaluated as it can serve as a ligand of Toxoplasma gondii orotate phosphoribosyltransferase [19-21]. This enzyme is necessary for replication of parasitic protozoan Toxoplasma gondii, which causes the disease toxoplasmosis. It was proved that trithiocyanuric acid is better ligand for the enzyme than 5-fluorouracil and emimycin, which are used for clinical treatment of toxoplasmosis. Kar et al. prepared a series of trinuclear Ru(II) complexes of composition , where L = 2,2’-bipyridine, 1,10-phenanthroline and arylazopyridine, which contain trithiocyanurate(3-) bridge bounding Ru(II) centers by chelating S,N donor sets of the anion [22,23]. Except of structural, electrochemical and spectral study, interaction of the complexes with the circular and linear forms of p-Bluescript DNA was reported. The Ru(II) complexes reduce fluorescence intensity of both circular and linear DNA. Zn(II), Fe(II) and Mn(II) complexes with a combination of nitrogen-donor ligands and ttcH3 were prepared and their antitumor and antimicrobial activities were assayed [24]. The IC50 values of the Fe(II) and Mn(II) compounds turned out to be lower than those of cisplatin and oxaliplatin. The antimicrobial activities of some Fe(II) and Mn(II) complexes were also found. Except of other physico-chemical properties of ttcH3 and its salts, their X-ray structures were determined [2,25-35]. Potentially six donor atoms can be used for coordination to metal centres. It is always difficult to avoid formation of precipitates of unknown and probably polymeric structure with metal ions in the presence of deprotonated trithiocyanuric acid. Mostly blocking ligands on metal centres must be coordinated. Despite of that, bonding properties of trithiocyanuric acid complexes were proved by single crystal X-ray analysis. In some compounds only deprotonated trithiocyanuric acid is present as anion not bonded to central atoms [36]. Mononuclear nickel and zinc complexes with nitrogen donor ligands and thiocyanurate(2-) bonded by S and N have been structurally characterized in [37-43]. Bridging, bischelating S,N mode was for the first time proved on cobalt complex can be used to store lipophilic organic molecules with the matching sizes in the inner cavity. Except for structure of mononuclear Ag(I) [52], hexanuclear [{AgPh3}6(?-ttc)2] complex with two parallel triazine rings held by six Cu-S bridges was characterized [53] as well as Au(I) cluster [54] and Cu(I) polymer [55]. Trinuclear cyclopentadienyl complexes of rhodium and iridium were also reported [56,57]. Magnetic and structural study on trinuclear copper complex with 1,3-bis(2-(4-methylpyridyl)imino)isoindoline as blocking ligand and ttc was given in [58]. Pmdien was proven to be a very good terdentate ligand for complexes with ttc. Trinuclear complexes of compositions [M3(pmdien)3(?-ttc)](ClO4)3 , where M = Zn, Cu and Ni were prepared and structurally characterized. [59-62]

The aim of this work was to prepare Fe(II), Mn(II) and Ni(II) complexes with nitrogen atom donors and trithiocyanurate anion. The complexes are of the following composition: [Fe(L1)](ttcH2)(ClO4)•EtOH•H2O (1), [Mn3(phen)6(ttc)](ClO4)3 (2), and Ni2(L2)(ttcH)(ClO4)2•6H2O•EtOH (3), where L1 = 2-[(E)-2-pyridylmethyleneamino]-N,N-bis[2-[(E)-2-pyridylmethyleneamino]ethyl]ethanamine, ttcH3 = trithiocyanuric acid, phen = 1,10-phenanthroline and L2 = 3-[2-(1,3,5,9,12-pentazacyclopentadec-3-yl)ethyl]-1,3,5,9,12-pentazacyclopentadecane. Structures of ligands are depicted in Scheme 1. Scheme 1. Structural formulas of used ligands. L1 = 2-[(E)-2-pyridylmethyleneamino]-N,N-bis[2-[(E)-2-pyridylmethyleneamino]ethyl]ethanamine, phen = 1,10-phenanthroline, L2 = 3-[2-(1,3,5,9,12-pentazacyclopentadec-3-yl)ethyl]-1,3,5,9,12-pentazacyclopentadecane We also attempted to prepare single crystals for X-ray analysis to confirm stereochemistry of the compounds and characterize them by physico-chemical methods. Due to the presence of positive charge in the molecule, prepared compounds can interact with enzyme acetylcholinesterase (AChE; EC 3.1.1.7). Acetylcholine, natural AChE substrate, contains positively charged quaternary nitrogen, which is responsible for its interaction with the enzyme active site [63]. Therefore, other goal of our study was to test possible anticholinesterase activity of synthesized complexes.

Práce je spojená s projektem CEITEC CZ.1.05/1.1.00/02.0068.

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