Macrometallocycle binuclear NHC silver(I) complexes: synthesis, structure and recognition of o-phenylenediamine

Two bis-benzimidazolium salts 1,4-bis[n'-(N-benzyl-benzimidazolium-N'-yl)alkoxy]-9,10-anthraquinone hexafluorophosphate ((LH2)-H-1 center dot(PF6)(2) and (LH2)-H-3 center dot(PF6)(2)) and two bis-imidazolium salts 1,4-bis[n'-(N-benzylimidazolium-N'-yl) alkoxy]-9,10-anthraquinone hexafluorophosphate ((LH2)-H-2 center dot(PF6)(2) and (LH2)-H-4 center dot(PF6)(2)) (n = 2 or 3), as well as their four macrometallocycle binuclear N-heterocyclic carbene silver(I) complexes [((LAg)-Ag-1)(2)](PF6)(2) (1), [((LAg)-Ag-2)(2)](PF6)(2) (2), [((LAg)-Ag-3)(2)](PF6)(2) (3) and [((LAg)-Ag-4)(2)](PF6)(2) (4) were prepared and characterized. In complexes 1-4, each macrometallocycle (30-membered macrometallocycle for 1 and 2, 34-membered macrometallocycle for 3 and 4) was formed by two biscarbene ligands (L-1-L-4 for 1-4) and two silver(I) ions. In the crystal packings of 1-4, 2D supramolecular layers are formed via intermolecular weak interactions including hydrogen bonds and pi-pi interactions. Additionally, the selective recognition of o-phenylenediamine (OPD) using 4 as a host compound was investigated using fluorescence and UV/vis titrations. The results indicate that 4 can distinguish effectively o-phenylenediamine from other aromatic amines.