Syntheses, structures, and photoluminescence studies of [2∶2] metallomacrocyclic silver(i) complexes with 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)benzene

Abstract

Five new silver(I) complexes with dimeric units, namely [Ag₂(bib)₂](BrO₃)₂1, [Ag₂(bib)₂](ClO₃)₂2, [Ag₂(bib)₂](ClO₄)₂3, [Ag₂(bib)₂](NO₃)₂·2H₂O 4 and [Ag₂(bib)₂(SCN)₂] 5 (bib = 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)benzene), have been synthesized and characterized by X-ray diffraction to observe the influence of the counter anions on crystal structures. Each bib acts as a bidentate ligand and every two bib ligands ligate a pair of Ag(I) ions resulting in a [2∶2] metallomacrocyclic motif that is further stabilized by intracyclic π–π interactions. 3 exhibits a dimeric structure, while 1, 2 and 4 are 1-D coordination polymers extended via interconnection of the dimeric units by the oxygen atoms from XO₃⁻ (X = Br and Cl) anions or Ag(I)⋯Ag(I) interactions. In 5, each Ag(I) ion is four-coordinate, and each dimeric unit is linked to the four adjacent dimeric units by four μ-sulfur atoms from SCN⁻ groups into 2-D layer and further packed in 3-D network via hydrogen bonds. The photoluminescent properties of 1–4 have been observed in the solid state and dichloromethane solution at room temperature. The possible emission mechanisms have been proposed based on molecular orbital (MO) calculations.