Kompleksi nekih prelaznih metala sa Šifovim bazama aminogvanidina

Abstract

U ovoj doktorskoj disertaciji opisane su sinteze novih kompleksa prelaznih metala sa piridoksiliden- (PLAG), odnosno saliciliden-aminogvanidinom (SALAG). Dobijeni kompleksi su okarakterisani elementalnom analizom, IR spektrima, konduktometrijskim i magnetnim merenjima, a većina i rendgenskom strukturnom analizom. Osim toga, dobijene su i nove forme ovih Šifovih baza, i to u vidu monokristala, čime su omogućena ispitivanja njihovih molekulskih i kristalnih struktura, kao i uporedna analiza sa koordinovanim ligandima. Sa PLAG je sintetisano 7 novi kompleksa Cu(II), a pored toga po prvi put su izolovani mono i bis(ligand) kompleksi Fe(III) i Co(III), mono(ligand) kompleksi V(V), kao i jedan kompleks Zn(II) u kojem ovaj potencijalno tridentatni ONN ligand, u monoprotonovanoj formi, ima ulogu kontra-jona. Sa stanovišta geometrije zajedničko za izolovane komplekse Cu(II) i V(V) je da imaju kvadratno-piramidalnu strukturu, sa izuzetkom jednog kvadratno-planarnog kompleksa Cu(II), dok je u kompleksima Fe(III) i Co(III) nađeno očekivano oktaedarsko okruženje centralnog jona. Pored ovih, sintetisano je i pet novih kompleksa sa SALAG, od kojih su dva kompleksa Cu(II) i kompleks V(V) okarakterisani rendgenskom strukturnom analizom, dok je mikrokristalnim bis(ligand) kompleksima Co(III) i Ni(III) na osnovu fizičko-hemijskih karakteristika predložena odgovarajuća struktura. Zajedničko za obe opisane Šifove baze je da se koordinuju na ONN tridentatni način, i to preko atoma kiseonika deprotonovane fenolne grupe i atoma azota azometinske i imino grupe AG fragmeta. Posebno je naglašeno da su sa PLAG izolovana dva dimerna kompleksa Cu(II) u kojima je po prvi put nađena tetradentatna koordinacija ovog liganda, u koju je dodatno uključen atom kiseonika hidroksimetil-grupe PL-ostatka. Za razliku od SALAG, koji je u izolovanim kompleksima koordinovan isključivo kao monoanjon, nastao deprotonacijom fenolne OH-grupe, za PLAG je osim ove, potvđena koordinacija u neutralnoj, zwitter-jonskoj, ali i dvostruko deprotonovanoj formi. Zwitter-jonska forma liganda nastaje migracijom atoma vodonika sa fenolnog hidroksila na piridinski atom azota PL-ostatka, dok deprotonacijom piridinskog ili hidrazinskog atoma azota, odnosno oba pomenuta atoma nastaju monoanjon i dianjon helatnog liganda, respektivno. Na kraju, urađena su i ispitivanja antimikrobne aktivnosti odabranih jedinjenja prema predstavnicima grampozitivnih i gramnegativnih bakterija, kao i dve kulture kvasca. Tom prilikom nije utvrđena nikakva inhibitorna aktivnost prema primenjenim bakterijskim sojevima, dok su u slučaju kvasaca izvesno mikrobicidno dejstvo pokazali samo kompleksi Cu(II).

This PhD thesis describes the syntheses of some new transition metal complexes with pyridoxilidene- (PLAG) and salicylideneaminoguanidine (SALAG). Obtained complexes are characterized by elemental analysis, IR spectroscopy, conductometric and magnetic measurements. Besides, the structural analysis of majority of the obtained complexes was performed. Some new forms of these Schiff bases are synthesized in form of single crystals, which made their X-ray analysis as well as comparison with coordinated forms possible. With PLAG, 7 new Cu(II) complexes were obtained and for the first time mono and bis(ligand) complexes of Fe(III) and Co(III) as well mono(ligand) complexes of V(V) were isolated. Furthermore, the structure of Zn(II) complex in which PLAG in its monocationic form has a role of counter ion is presented. With the exception of one Cu(II) complex, all reported Cu(II) and V(V) complexes have a square-pyramidal geometry, whilst Fe(III) and Co(III) are situated in octahedral surroundings. Also, five new complexes of Cu(II), Co(III), Ni(II) and V(V) with SALAG were synthesized. In both Cu(II) complexes and V(V) complex the expected coordination mode and geometry were confirmed by X-ray analysis, while octahedral structure of bis(ligand) complexes with Co(III) and Ni(II) was proposed based on results of physico-chemical characterization. Both PLAG and SALAG coordinate the metal ion in tridentate ONN manner, through the oxygen atom of deprotonated phenolic group and nitrogen atoms of azomethine and imino groups of AG moiety. It is also emphasized that in two dimeric Cu(II) complexes with PLAG tetradentate coordination mode was found, in which the oxygen atom of hydroxymethyl group of PL residue was additionally involved. Unlike SALAG, which is coordinated as monoanion in all of the examined complexes, PLAG can have one of three degrees of deprotonation. Zwitter-ion of PLAG is formed by migration of H-atom from phenolic oxygen to pyridine nitrogen, while the deprotonation of pyridine or/and hydrazine nitrogen, makes it mono-and dianion, respectively. Also, microbiological tests on the selected compounds were preformed. Namely, antimicrobial activity of these compounds against some gram-positive and gram-negative bacteria, as well as some yeast cultures was examined and none of the samples showed antimicrobial activity against bacteria, whilst only Cu(II) complexes showed certain inhibitory effect against yeasts.