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 (L1H2·(PF6)2 and L3H2·(PF6)2) and two bis-imidazolium salts 1,4-bis[n′-(N-benzyl-imidazolium-N′-yl)alkoxy]-9,10-anthraquinone hexafluorophosphate (L2H2·(PF6)2 and L4H2·(PF6)2) (n = 2 or 3), as well as their four macrometallocycle binuclear N-heterocyclic carbene silver(I) complexes [(L1Ag)2](PF6)2 (1), [(L2Ag)2](PF6)2 (2), [(L3Ag)2](PF6)2 (3) and [(L4Ag)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 (L1–L4 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 π–π 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.