Mn(II) azamacrocyclic bromide complexes with different nuclearities

The coordination behaviour of a series of pyridyl azamacrocyclic ligands, some of them containing cyanomethyl and cyanoethyl pendant-arms, towards Mn(II) ion was studied. All the complexes were characterized by microanalysis, LSI mass spectrometry, IR, UV–Vis spectroscopy and magnetic measurements. Crystal structures of [MnL1][MnBr4] (1), [MnL3][MnBr4] · 2CH3CN (3), [Mn2L5Br4] · 2CH3CN (5) and [Mn2L6Br4] (6) complexes have been determined. The X-ray studies show the presence of an ionic mixed octahedral–tetrahedral complex for 1 and 2, with the manganese ion of the cation complex, endomacrocyclicly coordinated by the six nitrogen donor atoms from the macrocyclic backbone in a distorted octahedral geometry. Instead, the complexes 5 and 6 are dinuclear, and both manganese ions are coordinated by one pyridinic and two amine nitrogen atoms from the macrocyclic backbone and two bromide ions, being the geometry around the metal better described as distorted square pyramidal. In all cases, the nitrile pendant-arms do not show coordination to the metal ion.

Graphical abstractThe coordination behaviour of a series of pyridyl azamacrocyclic ligands, some of them containing cyanomethyl and cyanoethyl pendant-arms, towards Mn(II) ion was studied. All the complexes were characterized by microanalysis, LSI mass spectrometry, IR, UV–Vis spectroscopy and magnetic measurements. Crystal structures of [MnL1][MnBr4] (1), [MnL3][MnBr4] · 2CH3CN (3), [Mn2L5Br4] · 2CH3CN (5) and [Mn2L6Br4] (6) complexes have been determined. The X-ray studies show the presence of an ionic mixed octahedral–tetrahedral complex for 1 and 3, with the manganese ion of the cation complex, endomacrocyclicly coordinated by the six nitrogen donor atoms from the macrocyclic backbone in a distorted octahedral geometry. Instead, the complexes 5 and 6 are dinuclear, and both manganese ions are coordinated by one pyridinic and two amine nitrogen atoms from the macrocyclic backbone and two bromide ions, being the geometry around the metal better described as distorted square pyramidal. In all cases, the nitrile pendant-arms do not show coordination to the metal ion.Figure optionsDownload full-size imageDownload as PowerPoint slide