Temperature effect on the conversions of phthalato and maleato manganese(II) complexes with diamine ligands

1,10-Phenanthroline hydrogen phthalato manganese(II) dimer [Mn2(Hphth)2(phen)4] · 2Hphth · 6H2O (1), monomeric phenanthroline phthalato manganese(II) monomer [Mn(phth)(phen)2(H2O)] · 2.5H2O (2), 2,2′-bipyridine phthalato manganese(II) polymer [Mn(phth)(bpy)(H2O)2]n (3) and 1,10-phenanthroline maleato polymer [Mn(male)(phen)(H2O)2]n · 2nH2O (4) (H2phth = o-phthalic acid, male = maleic acid, phen = 1,10-phenanthroline and bpy = 2,2′-bipyridine) have been synthesized and characterized spectroscopically and structurally. Each Mn(II) atom in dimeric 1 is octahedrally coordinated by two oxygen atoms of phthalate anions and by two cis-phenanthroline ligands. The hydrogen phthalato anion bridges the Mn(II) ions through the deprotonated carboxyl groups, while the carboxylic acid group remains free. In the monomeric 2, the Mn(II) ion is octahedrally surrounded by four nitrogen atoms from two cis-phen ligands, one carboxyl oxygen from a monodentate phth ion, and one coordinated water molecule. The dimeric phthalato complex 1 can be cleaved into monomer 2 under heating with deprotonation, and the course of the reaction can be qualitatively traced by IR spectra. The phthalate group in the complex 3 binds to two manganese atoms through the vicinal carboxyl-oxygen atoms in syn–syn bridging mode. The Mn(II) atoms are linked by the phthalate group to yield a one-dimensional chain running along the a-axis. The coordination polymer 3 can be obtained from the reaction of dichloro dibipyridine manganese with phthalate under heating. In polymer 4, the manganese atom is six-coordinated by two nitrogen atoms from phen, two oxygen atoms from the coordinated water molecules and two oxygen atoms from two different maleate dianions. Each maleato unit links two neighboring manganese atoms to yield one-dimensional chain along b-axis in bis-monodentate mode. The single-chain polymer 4 prepared at low temperature can be converted to double-chain coordination polymer [Mn(male)(phen)]n · nH2O (5) with dehydration in warm solution.

Graphical abstractUnder heating, phenanthroline hydrogen phthalato manganese(II) dimer could be cleaved into its related monomer with deprotonation of phthalate ligand. The 1D maleato manganese(II) prepared in an ice bath is converted into double-chain coordination polymer.Figure optionsDownload full-size imageDownload as PowerPoint slide