Polymeric, dimeric and monomeric Mn(II) complexes derived from [N′-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid methyl ester and 1-isonicotinoyl-4-phenyl-3-thiosemicarbazide: Syntheses, crystal structure and thermal analysis

The new Mn(II) polymeric complexes [Mn(pot)2(H2O)2]n (1) {pot− = 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione} and [Mn(ttfa)(μ-pchcm)]n (3) {Hpchcm = [N′-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid methyl ester}, from the precursor [Mn(ttfa)2(bpy)] (2) {Httfa = thenoyltrifluoroacetone}, as well as [Mn(ipt)2(o-phen)] (4) and [Mn(ttfa)2(ppta)2](ppta) (5) {ppta = N-phenyl-5-(4-pyridyl)-1,3,4-thiadiazol-2-yl-amine}, obtained from 1-isonicotinoyl-4-phenyl-3-thiosemicarbazide (Hipt) using o-phen and Httfa, are described. The ligand and complexes have been characterized by various physicochemical methods. The reaction of Hpchcm with Mn(OAc)2·4H2O in the presence of Httfa afforded an uniform two-dimensional Mn(II) coordination polymer, [Mn(pot)2(H2O)2]n (1), in which the cyclized ligand is bonded through the oxadiazole and pyridyl ring nitrogen atoms. During complexation, 1-isonicotinoyl-4-phenyl-3-thiosemicarbazide is converted to N-phenyl-5-(pyridine-4-yl)-1,3,4-thiadiazol-2-amine (ppta) in complex 5, where the Mn(II) center is bonded by two ttfa anions and two cyclized ppta ligands via pyridyl nitrogen atoms in axial positions. The crystal structure of complex 4 reveals that the ligand is uncyclized, bonded to the Mn(II) center as ON uninegative bidentate, through the deprotonated hydrazinic nitrogen and carbonyl oxygen atoms. The complexes have a distorted octahedral geometry around the metal center. Hpchcm acts as a multidentate ligand bonding through the Npy, Nhy, O and S atoms, producing five and six membered chelate rings in complex 3 and forming a network structure. The thermal behavior of the ligand Hpchcm and complexes 1, 2 and 3 have been studied which show that the complexes undergo two/three stages of decomposition and finally yield MnO as the residue.

New Mn(II) octahedral complexes [Mn(pot)2(H2O)2]n (1) and [Mn(ttfa)(μ-pchcm)]n (3) derived from 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (pot) and [N′-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid methyl ester (Hpchcm) are synthesized. Complex [Mn(ttfa)2(bpy)] (2) is synthesized by the reaction of Mn(OAc)2·4H2O with 2-thenoyltrifluoro acetone (Httfa) and 2,2′-bipyridyl. Complexes [Mn(ipt)2(o-phen)] (4) {Hipt = 1-isonicotinoyl-4-phenyl-3-thiosemicarbazide} and [Mn(ttfa)2(ppta)2](ppta) (5) {ppta = N-phenyl-5-(4-pyridyl)-1,3,4-thiadiazol-2-yl-amine} are also being reported. The complex 1 is a two-dimensional coordination polymer in which the cyclized ligand is bonded through the oxadiazole and pyridyl ring nitrogens. In complex 5, the ligand 1-isonicotinoyl-4-phenyl-3-thiosemicarbazide is converted to N-phenyl-5-(pyridine-4-yl)-1,3,4-thiadiazol-2-amine (ppta) during complex formation. Thermal behaviour of the ligand Hpchcm and complexes 1, 2 and 3 have been studied which indicate that complexes undergo two/three stages of decomposition and finally yield MnO as the residue.Figure optionsDownload as PowerPoint slide