Synthesis and structural studies of N-heterocyclic carbene Ag(I) and Hg(II) complexes and recognition of dihydrogen phosphate anion

Abstract

Abstract Bis-benzimidazolium salt ( S )-2,2′-bis[2″-( N -Et-benzimidazoliumyl)ethoxy]-1,1′-binaphthyl hexafluorophosphate [( S )-L 1 H 2 ]·(PF 6 ) 2 and bis-imidazolium salts ( S )-2,2′-bis[2″-( N -R-imidazoliumyl)ethoxy]-1,1′-binaphthyl hexafluorophosphate [( S )-L 2 H 2 ]·(PF 6 ) 2 and [( S )-L 3 H 2 ]·(PF 6 ) 2 (R = ethyl or benzyl), as well as their five N-heterocyclic carbene Hg(II) and Ag(I) complexes such as [( S )-L 1 Hg(HgBr 4 )] (1), [( S )-L 2 Hg(HgBr 4 )] (2), [( S )-L 2 Hg(HgI 4 )] (3), {[( S )-L 2 Ag](PF 6 )} n (4) and [( S )-L 3 Ag](PF 6 ) (5) have been prepared and characterized. Each of complexes 1–3 consists of two rings (one 6-membered ring and one 11-membered ring), in which the oxygen atom in the ligand participates in coordination with Hg(II) ion. In complex 4, 1D helical polymeric chain is formed via biscarbene ligand ( S )-L 2 and Ag(I) ion. A 15-membered macrometallocycle is constructed through a ligand ( S )-L 3 and a Ag(I) ion in complex 5. Additionally, the selective recognition of H 2 PO 4 − using complex 5 as a receptor was investigated on the basis of fluorescence and UV/vis spectroscopic titrations. The results indicate that complex 5 can distinguish effectively H 2 PO 4 − from other anions.