Synthesis, structures, photoluminescence, and theoretical investigations on two new Zn(II)/Mn(II) complexes with pyridine-2-amidoxine and carboxylate ligands

Abstract

Two new neutral mononuclear Zn(II) and Mn(II) complexes with pyridine-2-amidoxine and carboxylate ligands, [Zn(paH)2(OAc)2]·2CH3OH (paH = pyridine-2-amidoxine, HOAc = acetic acid) (1), and [Mn(paH)2(OAc)2]·C2H5OH·2H2O (2), have been prepared and characterized structurally by X-ray crystallography. 1 and free paH exhibit photoluminescence at room temperature in solid state, which is rare so fare for metal complexes with oxime-based ligand. The emissions of 1 and free paH arise from the metal-perturbed paH-based π → π* ligand-to-ligand charge transfer transition (LLCT) and π → π* charge transfer transition in nature, respectively, in terms of the density functional theory level calculations and molecular orbital analyses. Two new neutral mononuclear Zn (II) and Mn(II) complexes with pyridine-2-amidoxine and carboxylate ligands, [Zn(paH)2(OAc)2]·2CH3OH (paH = pyridine-2-amidoxine, HOAc = acetic acid) (1), and [Mn(paH)2(OAc)2]·C2H5OH·2H2O (2), have been synthesized and characterized structurally. The rarely reported photoluminescent behavior for oxime-based metal complexes has been observed in solid 1, indicating that such neutral mononuclear oxime-based metal complexes are a new class of potential candidates for photoluminescence and/or electroluminescence devices. The photoluminescent property and spectroscopic shifts have been investigated in detail for 1 and free paH ligand by means of the density functional theory level calculations and molecular orbital analyses. The emission for 1 and free paH ligand, are related to the metal-perturbed paH-based π → π* ligand-to-ligand charge transfer transition (LLCT) and π → π* charge transfer transition in nature, respectively.