The Mn(II)-2,2′-dipyridylamine-pseudohalide system: Synthesis, crystal structure and luminescence behaviour of [Mn(dpa)2(X)2]·H2O and [Mn(dpa)2(X)(OH2)]ClO4 (dpa=2,2′-dipyridylamine; , NCO−)

Abstract: Four complexes of the type [Mn(dpa)2(X)2]·H2O (dpa=2,2′-dipyridylamine; ; X=NCO−, 2) and [Mn(dpa)2(X)(OH2)]ClO4 (; X=NCO−, 4) have been synthesized using single-pot reactions of manganese(II) salt, dpa and X in 1:2:2 and 1:2:1 molar ratios, respectively. The compounds have been characterized by microanalytical, physicochemical, spectroscopic and magnetic results. Room temperature magnetic moments (μ eff) are in the range 5.88–5.97 BM and are typical of high-spin manganese(II) complexes ( idealized, S =5/2). The complexes display a Mn(III)–Mn(II) couple at ∼0.6 V versus SCE in DMF solutions. X-ray structure determinations show that in 1–4 the manganese(II) centres are in a distorted octahedral environment. Compounds 1 and 2 contain the MnN6 chromophore, completed by two bidentatendpa units and two terminal azido groups in 1 or N-coordinated cyanato ligands in 2, along with a water of crystallization. In 3 and 4, one water molecule acts as a coordinating ligand replacing one of the terminal pseudohalides in 1 and 2, respectively, resulting in a MnN5O chromophore. The amine H, terminal azido N or cyanato O, O and H’s of the water molecule are engaged in extensive hydrogen bonding of the type N–H⋯N, O–H⋯N and N–H⋯O in 1 and 2. Additionally O–H⋯O bonding is observed in 3 and 4. Supramolecular 2D sheet structures are obtained arising from such weak intermolecular forces. All the complexes display high-energy intraligand 1(π–π*) fluroscence and intraligand 3(π–π*) phosphorescence in glassy solutions (DMF at 77 K). [Copyright &y& Elsevier]