Synthesis, structure and photoluminescent properties of complexes manganese(II) based on 3-chloro-6-(3,5-dimethyl-1<i>Н</i>-pyrazol-1-yl)pyridazine

Manganese(II) complexes based on 3-chloro-6-(3,5-dimethyl-1H-pyrazol-1-yl)pyridazine (L) with different anions (bromide, perchlorate and salicylate) have been synthesized and structurally characterized. Complex compounds [MnL2Br2] (I), [MnL2(H2O)2](ClO4)2 (II) and [Mn3L2(Sal)6] · 2CH3CN (III) have been obtained by a reaction of appropriate manganese(II) salts and L in organic media at a molar ratio of 1 : 1. According to the single-crystal X-ray diffraction analysis, complexes I and II have mononuclear molecular structure and ionic structure, respectively, and complex III has a trinuclear molecular structure. The Mn centers in these solids exhibit a distorted octahedral coordination geometry, the coordination polyhedron in I is MnN4Br2, in II is MnN4O2, in III is Mn(1)N2O4 or Mn(2)O6. For the complexes I–III the photoluminescent (PL) properties have been studied in the solid state and in solution. The absorption spectrum of III in compared to the spectrum of L shows new bands at 310 and 340 nm; upon excitation in this region a dual-band emission with maxima at 390 and 445 nm with nanosecond lifetimes is observed. Solid complex III shows weak phosphorescence (λmax = 420 nm). Upon cooling at 77 K, in the PL spectrum of III two additional bands (520 and 585 nm) appear, while in the excitation spectrum bands at 460 and 520 nm appear. Probably, this emission occurs due to transitions in the Mn2+ ion. The effective magnetic moments of I–III have been measured at room temperature. For complex I the value is 5.82 B.M., which is typical of high-spin d5 configuration, where the predicted spin only value is 5.90 B.M. For complex III it is 5.70 B.M., which seems to be due to magnetic exchange interactions in the Mn3O12N4 cluster.